Adding Plugins

Updating the following
akismet.4.1.2, google-authenticator.0.52, jetpack.7.3.1

Signed-off-by: Yury German <blueknight@gentoo.org>

36 files changed, 8967 insertions, 0 deletions

diff --git a/plugins/jetpack/sync/class.jetpack-sync-actions.php b/plugins/jetpack/sync/class.jetpack-sync-actions.php
new file mode 100644
index 00000000..9268f78e
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-actions.php
@@ -0,0 +1,485 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-modules.php';
+
+/**
+ * The role of this class is to hook the Sync subsystem into WordPress - when to listen for actions,
+ * when to send, when to perform a full sync, etc.
+ *
+ * It also binds the action to send data to WPCOM to Jetpack's XMLRPC client object.
+ */
+class Jetpack_Sync_Actions {
+	static $sender                         = null;
+	static $listener                       = null;
+	const DEFAULT_SYNC_CRON_INTERVAL_NAME  = 'jetpack_sync_interval';
+	const DEFAULT_SYNC_CRON_INTERVAL_VALUE = 300; // 5 * MINUTE_IN_SECONDS;
+
+	static function init() {
+
+		// everything below this point should only happen if we're a valid sync site
+		if ( ! self::sync_allowed() ) {
+			return;
+		}
+
+		if ( self::sync_via_cron_allowed() ) {
+			self::init_sync_cron_jobs();
+		} elseif ( wp_next_scheduled( 'jetpack_sync_cron' ) ) {
+			self::clear_sync_cron_jobs();
+		}
+		// When importing via cron, do not sync
+		add_action( 'wp_cron_importer_hook', array( __CLASS__, 'set_is_importing_true' ), 1 );
+
+		// Sync connected user role changes to .com
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-users.php';
+
+		// publicize filter to prevent publicizing blacklisted post types
+		add_filter( 'publicize_should_publicize_published_post', array( __CLASS__, 'prevent_publicize_blacklisted_posts' ), 10, 2 );
+
+		/**
+		 * Fires on every request before default loading sync listener code.
+		 * Return false to not load sync listener code that monitors common
+		 * WP actions to be serialized.
+		 *
+		 * By default this returns true for cron jobs, non-GET-requests, or requests where the
+		 * user is logged-in.
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param bool should we load sync listener code for this request
+		 */
+		if ( apply_filters( 'jetpack_sync_listener_should_load', true ) ) {
+			self::initialize_listener();
+		}
+
+		add_action( 'init', array( __CLASS__, 'add_sender_shutdown' ), 90 );
+	}
+
+	static function add_sender_shutdown() {
+		/**
+		 * Fires on every request before default loading sync sender code.
+		 * Return false to not load sync sender code that serializes pending
+		 * data and sends it to WPCOM for processing.
+		 *
+		 * By default this returns true for cron jobs, POST requests, admin requests, or requests
+		 * by users who can manage_options.
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param bool should we load sync sender code for this request
+		 */
+		if ( apply_filters(
+			'jetpack_sync_sender_should_load',
+			(
+				( isset( $_SERVER['REQUEST_METHOD'] ) && 'POST' === $_SERVER['REQUEST_METHOD'] )
+				||
+				current_user_can( 'manage_options' )
+				||
+				is_admin()
+				||
+				defined( 'PHPUNIT_JETPACK_TESTSUITE' )
+			)
+		) ) {
+			self::initialize_sender();
+			add_action( 'shutdown', array( self::$sender, 'do_sync' ) );
+			add_action( 'shutdown', array( self::$sender, 'do_full_sync' ) );
+		}
+	}
+
+	static function sync_allowed() {
+		if ( defined( 'PHPUNIT_JETPACK_TESTSUITE' ) ) {
+			return true;
+		}
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+		if ( ! Jetpack_Sync_Settings::is_sync_enabled() ) {
+			return false;
+		}
+		if ( Jetpack::is_development_mode() ) {
+			return false;
+		}
+		if ( Jetpack::is_staging_site() ) {
+			return false;
+		}
+		if ( ! Jetpack::is_active() ) {
+			if ( ! doing_action( 'jetpack_user_authorized' ) ) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	static function sync_via_cron_allowed() {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+		return ( Jetpack_Sync_Settings::get_setting( 'sync_via_cron' ) );
+	}
+
+	static function prevent_publicize_blacklisted_posts( $should_publicize, $post ) {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+		if ( in_array( $post->post_type, Jetpack_Sync_Settings::get_setting( 'post_types_blacklist' ) ) ) {
+			return false;
+		}
+
+		return $should_publicize;
+	}
+
+	static function set_is_importing_true() {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+		Jetpack_Sync_Settings::set_importing( true );
+	}
+
+	static function send_data( $data, $codec_name, $sent_timestamp, $queue_id, $checkout_duration, $preprocess_duration ) {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-functions.php';
+		Jetpack::load_xml_rpc_client();
+
+		$query_args = array(
+			'sync'      => '1',             // add an extra parameter to the URL so we can tell it's a sync action
+			'codec'     => $codec_name,     // send the name of the codec used to encode the data
+			'timestamp' => $sent_timestamp, // send current server time so we can compensate for clock differences
+			'queue'     => $queue_id,       // sync or full_sync
+			'home'      => Jetpack_Sync_Functions::home_url(),  // Send home url option to check for Identity Crisis server-side
+			'siteurl'   => Jetpack_Sync_Functions::site_url(),  // Send siteurl option to check for Identity Crisis server-side
+			'cd'        => sprintf( '%.4f', $checkout_duration ),   // Time spent retrieving queue items from the DB
+			'pd'        => sprintf( '%.4f', $preprocess_duration ), // Time spent converting queue items into data to send
+		);
+
+		// Has the site opted in to IDC mitigation?
+		if ( Jetpack::sync_idc_optin() ) {
+			$query_args['idc'] = true;
+		}
+
+		if ( Jetpack_Options::get_option( 'migrate_for_idc', false ) ) {
+			$query_args['migrate_for_idc'] = true;
+		}
+
+		$query_args['timeout'] = Jetpack_Sync_Settings::is_doing_cron() ? 30 : 15;
+
+		/**
+		 * Filters query parameters appended to the Sync request URL sent to WordPress.com.
+		 *
+		 * @since 4.7.0
+		 *
+		 * @param array $query_args associative array of query parameters.
+		 */
+		$query_args = apply_filters( 'jetpack_sync_send_data_query_args', $query_args );
+
+		$url = add_query_arg( $query_args, Jetpack::xmlrpc_api_url() );
+
+		$rpc = new Jetpack_IXR_Client(
+			array(
+				'url'     => $url,
+				'user_id' => JETPACK_MASTER_USER,
+				'timeout' => $query_args['timeout'],
+			)
+		);
+
+		$result = $rpc->query( 'jetpack.syncActions', $data );
+
+		if ( ! $result ) {
+			return $rpc->get_jetpack_error();
+		}
+
+		$response = $rpc->getResponse();
+
+		// Check if WordPress.com IDC mitigation blocked the sync request
+		if ( is_array( $response ) && isset( $response['error_code'] ) ) {
+			$error_code              = $response['error_code'];
+			$allowed_idc_error_codes = array(
+				'jetpack_url_mismatch',
+				'jetpack_home_url_mismatch',
+				'jetpack_site_url_mismatch',
+			);
+
+			if ( in_array( $error_code, $allowed_idc_error_codes ) ) {
+				Jetpack_Options::update_option(
+					'sync_error_idc',
+					Jetpack::get_sync_error_idc_option( $response )
+				);
+			}
+
+			return new WP_Error(
+				'sync_error_idc',
+				esc_html__( 'Sync has been blocked from WordPress.com because it would cause an identity crisis', 'jetpack' )
+			);
+		}
+
+		return $response;
+	}
+
+	static function do_initial_sync() {
+		// Lets not sync if we are not suppose to.
+		if ( ! self::sync_allowed() ) {
+			return false;
+		}
+
+		$initial_sync_config = array(
+			'options'   => true,
+			'functions' => true,
+			'constants' => true,
+			'users'     => array( get_current_user_id() ),
+		);
+
+		if ( is_multisite() ) {
+			$initial_sync_config['network_options'] = true;
+		}
+
+		self::do_full_sync( $initial_sync_config );
+	}
+
+	static function do_full_sync( $modules = null ) {
+		if ( ! self::sync_allowed() ) {
+			return false;
+		}
+
+		$full_sync_module = Jetpack_Sync_Modules::get_module( 'full-sync' );
+
+		if ( ! $full_sync_module ) {
+			return false;
+		}
+
+		self::initialize_listener();
+
+		$full_sync_module->start( $modules );
+
+		return true;
+	}
+
+	static function jetpack_cron_schedule( $schedules ) {
+		if ( ! isset( $schedules[ self::DEFAULT_SYNC_CRON_INTERVAL_NAME ] ) ) {
+			$schedules[ self::DEFAULT_SYNC_CRON_INTERVAL_NAME ] = array(
+				'interval' => self::DEFAULT_SYNC_CRON_INTERVAL_VALUE,
+				'display'  => sprintf(
+					esc_html( _n( 'Every minute', 'Every %d minutes', intval( self::DEFAULT_SYNC_CRON_INTERVAL_VALUE / 60 ), 'jetpack' ) ),
+					intval( self::DEFAULT_SYNC_CRON_INTERVAL_VALUE / 60 )
+				),
+			);
+		}
+		return $schedules;
+	}
+
+	static function do_cron_sync() {
+		self::do_cron_sync_by_type( 'sync' );
+	}
+
+	static function do_cron_full_sync() {
+		self::do_cron_sync_by_type( 'full_sync' );
+	}
+
+	/**
+	 * Try to send actions until we run out of things to send,
+	 * or have to wait more than 15s before sending again,
+	 * or we hit a lock or some other sending issue
+	 *
+	 * @param string $type Sync type. Can be `sync` or `full_sync`.
+	 */
+	static function do_cron_sync_by_type( $type ) {
+		if ( ! self::sync_allowed() || ( 'sync' !== $type && 'full_sync' !== $type ) ) {
+			return;
+		}
+
+		self::initialize_sender();
+
+		$time_limit = Jetpack_Sync_Settings::get_setting( 'cron_sync_time_limit' );
+		$start_time = time();
+
+		do {
+			$next_sync_time = self::$sender->get_next_sync_time( $type );
+
+			if ( $next_sync_time ) {
+				$delay = $next_sync_time - time() + 1;
+				if ( $delay > 15 ) {
+					break;
+				} elseif ( $delay > 0 ) {
+					sleep( $delay );
+				}
+			}
+
+			$result = 'full_sync' === $type ? self::$sender->do_full_sync() : self::$sender->do_sync();
+		} while ( $result && ! is_wp_error( $result ) && ( $start_time + $time_limit ) > time() );
+	}
+
+	static function initialize_listener() {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-listener.php';
+		self::$listener = Jetpack_Sync_Listener::get_instance();
+	}
+
+	static function initialize_sender() {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-sender.php';
+		self::$sender = Jetpack_Sync_Sender::get_instance();
+
+		// bind the sending process
+		add_filter( 'jetpack_sync_send_data', array( __CLASS__, 'send_data' ), 10, 6 );
+	}
+
+	static function initialize_woocommerce() {
+		if ( false === class_exists( 'WooCommerce' ) ) {
+			return;
+		}
+		add_filter( 'jetpack_sync_modules', array( 'Jetpack_Sync_Actions', 'add_woocommerce_sync_module' ) );
+	}
+
+	static function add_woocommerce_sync_module( $sync_modules ) {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-woocommerce.php';
+		$sync_modules[] = 'Jetpack_Sync_Module_WooCommerce';
+		return $sync_modules;
+	}
+
+	static function initialize_wp_super_cache() {
+		if ( false === function_exists( 'wp_cache_is_enabled' ) ) {
+			return;
+		}
+		add_filter( 'jetpack_sync_modules', array( 'Jetpack_Sync_Actions', 'add_wp_super_cache_sync_module' ) );
+	}
+
+	static function add_wp_super_cache_sync_module( $sync_modules ) {
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-wp-super-cache.php';
+		$sync_modules[] = 'Jetpack_Sync_Module_WP_Super_Cache';
+		return $sync_modules;
+	}
+
+	static function sanitize_filtered_sync_cron_schedule( $schedule ) {
+		$schedule  = sanitize_key( $schedule );
+		$schedules = wp_get_schedules();
+
+		// Make sure that the schedule has actually been registered using the `cron_intervals` filter.
+		if ( isset( $schedules[ $schedule ] ) ) {
+			return $schedule;
+		}
+
+		return self::DEFAULT_SYNC_CRON_INTERVAL_NAME;
+	}
+
+	static function get_start_time_offset( $schedule = '', $hook = '' ) {
+		$start_time_offset = is_multisite()
+			? mt_rand( 0, ( 2 * self::DEFAULT_SYNC_CRON_INTERVAL_VALUE ) )
+			: 0;
+
+		/**
+		 * Allows overriding the offset that the sync cron jobs will first run. This can be useful when scheduling
+		 * cron jobs across multiple sites in a network.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param int    $start_time_offset
+		 * @param string $hook
+		 * @param string $schedule
+		 */
+		return intval(
+			apply_filters(
+				'jetpack_sync_cron_start_time_offset',
+				$start_time_offset,
+				$hook,
+				$schedule
+			)
+		);
+	}
+
+	static function maybe_schedule_sync_cron( $schedule, $hook ) {
+		if ( ! $hook ) {
+			return;
+		}
+		$schedule = self::sanitize_filtered_sync_cron_schedule( $schedule );
+
+		$start_time = time() + self::get_start_time_offset( $schedule, $hook );
+		if ( ! wp_next_scheduled( $hook ) ) {
+			// Schedule a job to send pending queue items once a minute
+			wp_schedule_event( $start_time, $schedule, $hook );
+		} elseif ( $schedule != wp_get_schedule( $hook ) ) {
+			// If the schedule has changed, update the schedule
+			wp_clear_scheduled_hook( $hook );
+			wp_schedule_event( $start_time, $schedule, $hook );
+		}
+	}
+
+	static function clear_sync_cron_jobs() {
+		wp_clear_scheduled_hook( 'jetpack_sync_cron' );
+		wp_clear_scheduled_hook( 'jetpack_sync_full_cron' );
+	}
+
+	static function init_sync_cron_jobs() {
+		add_filter( 'cron_schedules', array( __CLASS__, 'jetpack_cron_schedule' ) );
+
+		add_action( 'jetpack_sync_cron', array( __CLASS__, 'do_cron_sync' ) );
+		add_action( 'jetpack_sync_full_cron', array( __CLASS__, 'do_cron_full_sync' ) );
+
+		/**
+		 * Allows overriding of the default incremental sync cron schedule which defaults to once every 5 minutes.
+		 *
+		 * @since 4.3.2
+		 *
+		 * @param string self::DEFAULT_SYNC_CRON_INTERVAL_NAME
+		 */
+		$incremental_sync_cron_schedule = apply_filters( 'jetpack_sync_incremental_sync_interval', self::DEFAULT_SYNC_CRON_INTERVAL_NAME );
+		self::maybe_schedule_sync_cron( $incremental_sync_cron_schedule, 'jetpack_sync_cron' );
+
+		/**
+		 * Allows overriding of the full sync cron schedule which defaults to once every 5 minutes.
+		 *
+		 * @since 4.3.2
+		 *
+		 * @param string self::DEFAULT_SYNC_CRON_INTERVAL_NAME
+		 */
+		$full_sync_cron_schedule = apply_filters( 'jetpack_sync_full_sync_interval', self::DEFAULT_SYNC_CRON_INTERVAL_NAME );
+		self::maybe_schedule_sync_cron( $full_sync_cron_schedule, 'jetpack_sync_full_cron' );
+	}
+
+	static function cleanup_on_upgrade( $new_version = null, $old_version = null ) {
+		if ( wp_next_scheduled( 'jetpack_sync_send_db_checksum' ) ) {
+			wp_clear_scheduled_hook( 'jetpack_sync_send_db_checksum' );
+		}
+
+		$is_new_sync_upgrade = version_compare( $old_version, '4.2', '>=' );
+		if ( ! empty( $old_version ) && $is_new_sync_upgrade && version_compare( $old_version, '4.5', '<' ) ) {
+			require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+			self::clear_sync_cron_jobs();
+			Jetpack_Sync_Settings::update_settings(
+				array(
+					'render_filtered_content' => Jetpack_Sync_Defaults::$default_render_filtered_content,
+				)
+			);
+		}
+	}
+
+	static function get_sync_status() {
+		self::initialize_sender();
+
+		$sync_module     = Jetpack_Sync_Modules::get_module( 'full-sync' );
+		$queue           = self::$sender->get_sync_queue();
+		$full_queue      = self::$sender->get_full_sync_queue();
+		$cron_timestamps = array_keys( _get_cron_array() );
+		$next_cron       = $cron_timestamps[0] - time();
+
+		$full_sync_status = ( $sync_module ) ? $sync_module->get_status() : array();
+		return array_merge(
+			$full_sync_status,
+			array(
+				'cron_size'            => count( $cron_timestamps ),
+				'next_cron'            => $next_cron,
+				'queue_size'           => $queue->size(),
+				'queue_lag'            => $queue->lag(),
+				'queue_next_sync'      => ( self::$sender->get_next_sync_time( 'sync' ) - microtime( true ) ),
+				'full_queue_size'      => $full_queue->size(),
+				'full_queue_lag'       => $full_queue->lag(),
+				'full_queue_next_sync' => ( self::$sender->get_next_sync_time( 'full_sync' ) - microtime( true ) ),
+			)
+		);
+	}
+}
+
+// Check for WooCommerce support
+add_action( 'plugins_loaded', array( 'Jetpack_Sync_Actions', 'initialize_woocommerce' ), 5 );
+
+// Check for WP Super Cache
+add_action( 'plugins_loaded', array( 'Jetpack_Sync_Actions', 'initialize_wp_super_cache' ), 5 );
+
+/*
+ * Init after plugins loaded and before the `init` action. This helps with issues where plugins init
+ * with a high priority or sites that use alternate cron.
+ */
+add_action( 'plugins_loaded', array( 'Jetpack_Sync_Actions', 'init' ), 90 );
+
+
+
+// We need to define this here so that it's hooked before `updating_jetpack_version` is called
+add_action( 'updating_jetpack_version', array( 'Jetpack_Sync_Actions', 'cleanup_on_upgrade' ), 10, 2 );
+add_action( 'jetpack_user_authorized', array( 'Jetpack_Sync_Actions', 'do_initial_sync' ), 10, 0 );
+
diff --git a/plugins/jetpack/sync/class.jetpack-sync-defaults.php b/plugins/jetpack/sync/class.jetpack-sync-defaults.php
new file mode 100644
index 00000000..787145c8
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-defaults.php
@@ -0,0 +1,637 @@
+<?php
+require_once JETPACK__PLUGIN_DIR . 'modules/sso/class.jetpack-sso-helpers.php';
+
+/**
+ * Just some defaults that we share with the server
+ */
+class Jetpack_Sync_Defaults {
+
+	static $default_options_whitelist = array(
+		'stylesheet',
+		'blogname',
+		'blogdescription',
+		'blog_charset',
+		'permalink_structure',
+		'category_base',
+		'tag_base',
+		'sidebars_widgets',
+		'comment_moderation',
+		'default_comment_status',
+		'page_on_front',
+		'rss_use_excerpt',
+		'subscription_options',
+		'stb_enabled',
+		'stc_enabled',
+		'comment_registration',
+		'show_avatars',
+		'avatar_default',
+		'avatar_rating',
+		'highlander_comment_form_prompt',
+		'jetpack_comment_form_color_scheme',
+		'stats_options',
+		'gmt_offset',
+		'timezone_string',
+		'jetpack_sync_non_public_post_stati',
+		'jetpack_options',
+		'site_icon', // (int) - ID of core's Site Icon attachment ID
+		'default_post_format',
+		'default_category',
+		'large_size_w',
+		'large_size_h',
+		'thumbnail_size_w',
+		'thumbnail_size_h',
+		'medium_size_w',
+		'medium_size_h',
+		'thumbnail_crop',
+		'image_default_link_type',
+		'site_logo',
+		'sharing-options',
+		'sharing-services',
+		'post_count',
+		'default_ping_status',
+		'sticky_posts',
+		'blog_public',
+		'default_pingback_flag',
+		'require_name_email',
+		'close_comments_for_old_posts',
+		'close_comments_days_old',
+		'thread_comments',
+		'thread_comments_depth',
+		'page_comments',
+		'comments_per_page',
+		'default_comments_page',
+		'comment_order',
+		'comments_notify',
+		'moderation_notify',
+		'social_notifications_like',
+		'social_notifications_reblog',
+		'social_notifications_subscribe',
+		'comment_whitelist',
+		'comment_max_links',
+		'moderation_keys',
+		'jetpack_wga',
+		'disabled_likes',
+		'disabled_reblogs',
+		'jetpack_comment_likes_enabled',
+		'twitter_via',
+		'jetpack-memberships-connected-account-id',
+		'jetpack-twitter-cards-site-tag',
+		'wpcom_publish_posts_with_markdown',
+		'wpcom_publish_comments_with_markdown',
+		'jetpack_activated',
+		'jetpack_available_modules',
+		'jetpack_autoupdate_plugins',
+		'jetpack_autoupdate_plugins_translations',
+		'jetpack_autoupdate_themes',
+		'jetpack_autoupdate_themes_translations',
+		'jetpack_autoupdate_core',
+		'jetpack_autoupdate_translations',
+		'carousel_background_color',
+		'carousel_display_exif',
+		'jetpack_portfolio',
+		'jetpack_portfolio_posts_per_page',
+		'jetpack_testimonial',
+		'jetpack_testimonial_posts_per_page',
+		'tiled_galleries',
+		'gravatar_disable_hovercards',
+		'infinite_scroll',
+		'infinite_scroll_google_analytics',
+		'wp_mobile_excerpt',
+		'wp_mobile_featured_images',
+		'wp_mobile_app_promos',
+		'monitor_receive_notifications',
+		'post_by_email_address',
+		'jetpack_mailchimp',
+		'jetpack_protect_key',
+		'jetpack_protect_global_whitelist',
+		'jetpack_sso_require_two_step',
+		'jetpack_sso_match_by_email',
+		'jetpack_relatedposts',
+		'verification_services_codes',
+		'users_can_register',
+		'active_plugins',
+		'uninstall_plugins',
+		'advanced_seo_front_page_description', // Jetpack_SEO_Utils::FRONT_PAGE_META_OPTION
+		'advanced_seo_title_formats', // Jetpack_SEO_Titles::TITLE_FORMATS_OPTION
+		'jetpack_api_cache_enabled',
+		'start_of_week',
+		'blacklist_keys',
+		'posts_per_page',
+		'posts_per_rss',
+		'show_on_front',
+		'ping_sites',
+		'uploads_use_yearmonth_folders',
+		'date_format',
+		'time_format',
+		'admin_email',
+		'new_admin_email',
+		'default_email_category',
+		'default_role',
+		'page_for_posts',
+		'mailserver_url',
+		'mailserver_login', // Not syncing contents, only the option name
+		'mailserver_pass', // Not syncing contents, only the option name
+		'mailserver_port',
+		'wp_page_for_privacy_policy',
+		'enable_header_ad',
+		'wordads_second_belowpost',
+		'wordads_display_front_page',
+		'wordads_display_post',
+		'wordads_display_page',
+		'wordads_display_archive',
+		'wordads_custom_adstxt',
+		'site_segment',
+		'site_user_type',
+		'site_vertical',
+		'jetpack_excluded_extensions',
+	);
+
+	public static function get_options_whitelist() {
+		/** This filter is already documented in json-endpoints/jetpack/class.wpcom-json-api-get-option-endpoint.php */
+		$options_whitelist = apply_filters( 'jetpack_options_whitelist', self::$default_options_whitelist );
+		/**
+		 * Filter the list of WordPress options that are manageable via the JSON API.
+		 *
+		 * @module sync
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array The default list of options.
+		 */
+		return apply_filters( 'jetpack_sync_options_whitelist', $options_whitelist );
+	}
+
+	// Do not sync contents for these events, only the option name
+	static $default_options_contentless = array(
+		'mailserver_login',
+		'mailserver_pass',
+	);
+
+	public static function get_options_contentless() {
+		/**
+		 * Filter the list of WordPress options that should be synced without content
+		 *
+		 * @module sync
+		 *
+		 * @since 6.1.0
+		 *
+		 * @param array The list of options synced without content.
+		 */
+		return apply_filters( 'jetpack_sync_options_contentless', self::$default_options_contentless );
+	}
+
+	static $default_constants_whitelist = array(
+		'EMPTY_TRASH_DAYS',
+		'WP_POST_REVISIONS',
+		'AUTOMATIC_UPDATER_DISABLED',
+		'ABSPATH',
+		'WP_CONTENT_DIR',
+		'FS_METHOD',
+		'DISALLOW_FILE_EDIT',
+		'DISALLOW_FILE_MODS',
+		'WP_AUTO_UPDATE_CORE',
+		'WP_HTTP_BLOCK_EXTERNAL',
+		'WP_ACCESSIBLE_HOSTS',
+		'JETPACK__VERSION',
+		'IS_PRESSABLE',
+		'DISABLE_WP_CRON',
+		'ALTERNATE_WP_CRON',
+		'WP_CRON_LOCK_TIMEOUT',
+		'PHP_VERSION',
+		'WP_MEMORY_LIMIT',
+		'WP_MAX_MEMORY_LIMIT',
+	);
+
+	public static function get_constants_whitelist() {
+		/**
+		 * Filter the list of PHP constants that are manageable via the JSON API.
+		 *
+		 * @module sync
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array The default list of constants options.
+		 */
+		return apply_filters( 'jetpack_sync_constants_whitelist', self::$default_constants_whitelist );
+	}
+
+	static $default_callable_whitelist = array(
+		'wp_max_upload_size'               => 'wp_max_upload_size',
+		'is_main_network'                  => array( 'Jetpack', 'is_multi_network' ),
+		'is_multi_site'                    => 'is_multisite',
+		'main_network_site'                => array( 'Jetpack_Sync_Functions', 'main_network_site_url' ),
+		'site_url'                         => array( 'Jetpack_Sync_Functions', 'site_url' ),
+		'home_url'                         => array( 'Jetpack_Sync_Functions', 'home_url' ),
+		'single_user_site'                 => array( 'Jetpack', 'is_single_user_site' ),
+		'updates'                          => array( 'Jetpack', 'get_updates' ),
+		'has_file_system_write_access'     => array( 'Jetpack_Sync_Functions', 'file_system_write_access' ),
+		'is_version_controlled'            => array( 'Jetpack_Sync_Functions', 'is_version_controlled' ),
+		'taxonomies'                       => array( 'Jetpack_Sync_Functions', 'get_taxonomies' ),
+		'post_types'                       => array( 'Jetpack_Sync_Functions', 'get_post_types' ),
+		'post_type_features'               => array( 'Jetpack_Sync_Functions', 'get_post_type_features' ),
+		'shortcodes'                       => array( 'Jetpack_Sync_Functions', 'get_shortcodes' ),
+		'rest_api_allowed_post_types'      => array( 'Jetpack_Sync_Functions', 'rest_api_allowed_post_types' ),
+		'rest_api_allowed_public_metadata' => array( 'Jetpack_Sync_Functions', 'rest_api_allowed_public_metadata' ),
+		'sso_is_two_step_required'         => array( 'Jetpack_SSO_Helpers', 'is_two_step_required' ),
+		'sso_should_hide_login_form'       => array( 'Jetpack_SSO_Helpers', 'should_hide_login_form' ),
+		'sso_match_by_email'               => array( 'Jetpack_SSO_Helpers', 'match_by_email' ),
+		'sso_new_user_override'            => array( 'Jetpack_SSO_Helpers', 'new_user_override' ),
+		'sso_bypass_default_login_form'    => array( 'Jetpack_SSO_Helpers', 'bypass_login_forward_wpcom' ),
+		'wp_version'                       => array( 'Jetpack_Sync_Functions', 'wp_version' ),
+		'get_plugins'                      => array( 'Jetpack_Sync_Functions', 'get_plugins' ),
+		'get_plugins_action_links'         => array( 'Jetpack_Sync_functions', 'get_plugins_action_links' ),
+		'active_modules'                   => array( 'Jetpack', 'get_active_modules' ),
+		'hosting_provider'                 => array( 'Jetpack_Sync_Functions', 'get_hosting_provider' ),
+		'locale'                           => 'get_locale',
+		'site_icon_url'                    => array( 'Jetpack_Sync_Functions', 'site_icon_url' ),
+		'roles'                            => array( 'Jetpack_Sync_Functions', 'roles' ),
+		'timezone'                         => array( 'Jetpack_Sync_Functions', 'get_timezone' ),
+		'available_jetpack_blocks'         => array( 'Jetpack_Gutenberg', 'get_availability' ), // Includes both Gutenberg blocks *and* plugins
+		'paused_themes'                    => array( 'Jetpack_Sync_Functions', 'get_paused_themes' ),
+		'paused_plugins'                   => array( 'Jetpack_Sync_Functions', 'get_paused_plugins' ),
+	);
+
+
+	static $default_post_type_attributes = array(
+		'name'                => '',
+		'label'               => '',
+		'labels'              => array(),
+		'description'         => '',
+		'public'              => false,
+		'hierarchical'        => false,
+		'exclude_from_search' => true,
+		'publicly_queryable'  => null,
+		'show_ui'             => false,
+		'show_in_menu'        => null,
+		'show_in_nav_menus'   => null,
+		'show_in_admin_bar'   => false,
+		'menu_position'       => null,
+		'menu_icon'           => null,
+		'supports'            => array(),
+		'capability_type'     => 'post',
+		'capabilities'        => array(),
+		'cap'                 => array(),
+		'map_meta_cap'        => true,
+		'taxonomies'          => array(),
+		'has_archive'         => false,
+		'rewrite'             => true,
+		'query_var'           => true,
+		'can_export'          => true,
+		'delete_with_user'    => null,
+		'show_in_rest'        => false,
+		'rest_base'           => false,
+		'_builtin'            => false,
+		'_edit_link'          => 'post.php?post=%d',
+	);
+
+	public static function get_callable_whitelist() {
+		/**
+		 * Filter the list of callables that are manageable via the JSON API.
+		 *
+		 * @module sync
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array The default list of callables.
+		 */
+		return apply_filters( 'jetpack_sync_callable_whitelist', self::$default_callable_whitelist );
+	}
+
+	static $blacklisted_post_types = array(
+		'ai1ec_event',
+		'bwg_album',
+		'bwg_gallery',
+		'customize_changeset', // WP built-in post type for Customizer changesets
+		'dn_wp_yt_log',
+		'http',
+		'idx_page',
+		'jetpack_migration',
+		'postman_sent_mail',
+		'rssap-feed',
+		'rssmi_feed_item',
+		'secupress_log_action',
+		'sg_optimizer_jobs',
+		'snitch',
+		'wpephpcompat_jobs',
+		'wprss_feed_item',
+		'wp_automatic',
+		'jp_sitemap_master',
+		'jp_sitemap',
+		'jp_sitemap_index',
+		'jp_img_sitemap',
+		'jp_img_sitemap_index',
+		'jp_vid_sitemap',
+		'jp_vid_sitemap_index',
+		'vip-legacy-redirect',
+	);
+
+	static $default_post_checksum_columns = array(
+		'ID',
+		'post_modified',
+	);
+
+	static $default_post_meta_checksum_columns = array(
+		'meta_id',
+		'meta_value',
+	);
+
+	static $default_comment_checksum_columns = array(
+		'comment_ID',
+		'comment_content',
+	);
+
+	static $default_comment_meta_checksum_columns = array(
+		'meta_id',
+		'meta_value',
+	);
+
+	static $default_option_checksum_columns = array(
+		'option_name',
+		'option_value',
+	);
+
+	static $default_multisite_callable_whitelist = array(
+		'network_name'                        => array( 'Jetpack', 'network_name' ),
+		'network_allow_new_registrations'     => array( 'Jetpack', 'network_allow_new_registrations' ),
+		'network_add_new_users'               => array( 'Jetpack', 'network_add_new_users' ),
+		'network_site_upload_space'           => array( 'Jetpack', 'network_site_upload_space' ),
+		'network_upload_file_types'           => array( 'Jetpack', 'network_upload_file_types' ),
+		'network_enable_administration_menus' => array( 'Jetpack', 'network_enable_administration_menus' ),
+	);
+
+	public static function get_multisite_callable_whitelist() {
+		/**
+		 * Filter the list of multisite callables that are manageable via the JSON API.
+		 *
+		 * @module sync
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array The default list of multisite callables.
+		 */
+		return apply_filters( 'jetpack_sync_multisite_callable_whitelist', self::$default_multisite_callable_whitelist );
+	}
+
+	static $post_meta_whitelist = array(
+		'_feedback_akismet_values',
+		'_feedback_email',
+		'_feedback_extra_fields',
+		'_g_feedback_shortcode',
+		'_jetpack_post_thumbnail',
+		'_menu_item_classes',
+		'_menu_item_menu_item_parent',
+		'_menu_item_object',
+		'_menu_item_object_id',
+		'_menu_item_orphaned',
+		'_menu_item_type',
+		'_menu_item_xfn',
+		'_publicize_facebook_user',
+		'_publicize_twitter_user',
+		'_thumbnail_id',
+		'_wp_attached_file',
+		'_wp_attachment_backup_sizes',
+		'_wp_attachment_context',
+		'_wp_attachment_image_alt',
+		'_wp_attachment_is_custom_background',
+		'_wp_attachment_is_custom_header',
+		'_wp_attachment_metadata',
+		'_wp_page_template',
+		'_wp_trash_meta_comments_status',
+		'_wpas_mess',
+		'content_width',
+		'custom_css_add',
+		'custom_css_preprocessor',
+		'enclosure',
+		'imagedata',
+		'nova_price',
+		'publicize_results',
+		'sharing_disabled',
+		'switch_like_status',
+		'videopress_guid',
+		'vimeo_poster_image',
+		'advanced_seo_description', // Jetpack_SEO_Posts::DESCRIPTION_META_KEY
+	);
+
+	public static function get_post_meta_whitelist() {
+		/**
+		 * Filter the list of post meta data that are manageable via the JSON API.
+		 *
+		 * @module sync
+		 *
+		 * @since 4.8.0
+		 *
+		 * @param array The default list of meta data keys.
+		 */
+		return apply_filters( 'jetpack_sync_post_meta_whitelist', self::$post_meta_whitelist );
+	}
+
+	static $comment_meta_whitelist = array(
+		'hc_avatar',
+		'hc_post_as',
+		'hc_wpcom_id_sig',
+		'hc_foreign_user_id',
+	);
+
+	public static function get_comment_meta_whitelist() {
+		/**
+		 * Filter the list of comment meta data that are manageable via the JSON API.
+		 *
+		 * @module sync
+		 *
+		 * @since 5.7.0
+		 *
+		 * @param array The default list of comment meta data keys.
+		 */
+		return apply_filters( 'jetpack_sync_comment_meta_whitelist', self::$comment_meta_whitelist );
+	}
+
+	// TODO: move this to server? - these are theme support values
+	// that should be synced as jetpack_current_theme_supports_foo option values
+	static $default_theme_support_whitelist = array(
+		'post-thumbnails',
+		'post-formats',
+		'custom-header',
+		'custom-background',
+		'custom-logo',
+		'menus',
+		'automatic-feed-links',
+		'editor-style',
+		'widgets',
+		'html5',
+		'title-tag',
+		'jetpack-social-menu',
+		'jetpack-responsive-videos',
+		'infinite-scroll',
+		'site-logo',
+	);
+
+	static function is_whitelisted_option( $option ) {
+		$whitelisted_options = self::get_options_whitelist();
+		foreach ( $whitelisted_options as $whitelisted_option ) {
+			if ( $whitelisted_option[0] === '/' && preg_match( $whitelisted_option, $option ) ) {
+				return true;
+			} elseif ( $whitelisted_option === $option ) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
+	static $default_capabilities_whitelist = array(
+		'switch_themes',
+		'edit_themes',
+		'edit_theme_options',
+		'install_themes',
+		'activate_plugins',
+		'edit_plugins',
+		'install_plugins',
+		'edit_users',
+		'edit_files',
+		'manage_options',
+		'moderate_comments',
+		'manage_categories',
+		'manage_links',
+		'upload_files',
+		'import',
+		'unfiltered_html',
+		'edit_posts',
+		'edit_others_posts',
+		'edit_published_posts',
+		'publish_posts',
+		'edit_pages',
+		'read',
+		'publish_pages',
+		'edit_others_pages',
+		'edit_published_pages',
+		'delete_pages',
+		'delete_others_pages',
+		'delete_published_pages',
+		'delete_posts',
+		'delete_others_posts',
+		'delete_published_posts',
+		'delete_private_posts',
+		'edit_private_posts',
+		'read_private_posts',
+		'delete_private_pages',
+		'edit_private_pages',
+		'read_private_pages',
+		'delete_users',
+		'create_users',
+		'unfiltered_upload',
+		'edit_dashboard',
+		'customize',
+		'delete_site',
+		'update_plugins',
+		'delete_plugins',
+		'update_themes',
+		'update_core',
+		'list_users',
+		'remove_users',
+		'add_users',
+		'promote_users',
+		'delete_themes',
+		'export',
+		'edit_comment',
+		'upload_plugins',
+		'upload_themes',
+	);
+
+	public static function get_capabilities_whitelist() {
+		/**
+		 * Filter the list of capabilities that we care about
+		 *
+		 * @module sync
+		 *
+		 * @since 5.5.0
+		 *
+		 * @param array The default list of capabilities.
+		 */
+		return apply_filters( 'jetpack_sync_capabilities_whitelist', self::$default_capabilities_whitelist );
+	}
+
+	static function get_max_sync_execution_time() {
+		$max_exec_time = intval( ini_get( 'max_execution_time' ) );
+		if ( 0 === $max_exec_time ) {
+			// 0 actually means "unlimited", but let's not treat it that way
+			$max_exec_time = 60;
+		}
+		return floor( $max_exec_time / 3 );
+	}
+
+	static function get_default_setting( $setting ) {
+		$default_name = "default_$setting"; // e.g. default_dequeue_max_bytes
+		return Jetpack_Sync_Defaults::$$default_name;
+	}
+
+	static $default_network_options_whitelist = array(
+		'site_name',
+		'jetpack_protect_key',
+		'jetpack_protect_global_whitelist',
+		'active_sitewide_plugins',
+	);
+
+	/**
+	 * A mapping of known importers to friendly names.
+	 *
+	 * Keys are the class name of the known importer.
+	 * Values are the friendly name.
+	 *
+	 * @since 7.3.0
+	 *
+	 * @var array
+	 */
+	public static $default_known_importers = array(
+		'Blogger_Importer'     => 'blogger',
+		'LJ_API_Import'        => 'livejournal',
+		'MT_Import'            => 'mt',
+		'RSS_Import'           => 'rss',
+		'WC_Tax_Rate_Importer' => 'woo-tax-rate',
+		'WP_Import'            => 'wordpress',
+	);
+
+	/**
+	 * Returns a list of known importers.
+	 *
+	 * @since 7.3.0
+	 *
+	 * @return array Known importers with importer class names as keys and friendly names as values.
+	 */
+	public static function get_known_importers() {
+		/**
+		 * Filter the list of known importers.
+		 *
+		 * @module sync
+		 *
+		 * @since 7.3.0
+		 *
+		 * @param array The default list of known importers.
+		 */
+		return apply_filters( 'jetpack_sync_known_importers', self::$default_known_importers );
+	}
+
+	static $default_taxonomy_whitelist       = array();
+	static $default_dequeue_max_bytes        = 500000; // very conservative value, 1/2 MB
+	static $default_upload_max_bytes         = 600000; // a little bigger than the upload limit to account for serialization
+	static $default_upload_max_rows          = 500;
+	static $default_sync_wait_time           = 10; // seconds, between syncs
+	static $default_sync_wait_threshold      = 5; // only wait before next send if the current send took more than X seconds
+	static $default_enqueue_wait_time        = 10; // wait between attempting to continue a full sync, via requests
+	static $default_max_queue_size           = 1000;
+	static $default_max_queue_lag            = 900; // 15 minutes
+	static $default_queue_max_writes_sec     = 100; // 100 rows a second
+	static $default_post_types_blacklist     = array();
+	static $default_post_meta_whitelist      = array();
+	static $default_comment_meta_whitelist   = array();
+	static $default_disable                  = 0; // completely disable sending data to wpcom
+	static $default_network_disable          = 0; // completely disable sending data to wpcom network wide
+	static $default_sync_via_cron            = 1; // use cron to sync
+	static $default_render_filtered_content  = 0; // render post_filtered_content
+	static $default_max_enqueue_full_sync    = 100; // max number of items to enqueue at a time when running full sync
+	static $default_max_queue_size_full_sync = 1000; // max number of total items in the full sync queue
+	static $default_sync_callables_wait_time = MINUTE_IN_SECONDS; // seconds before sending callables again
+	static $default_sync_constants_wait_time = HOUR_IN_SECONDS; // seconds before sending constants again
+	static $default_sync_queue_lock_timeout  = 120; // 2 minutes
+	static $default_cron_sync_time_limit     = 30; // 30 seconds
+
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-functions.php b/plugins/jetpack/sync/class.jetpack-sync-functions.php
new file mode 100644
index 00000000..609797bb
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-functions.php
@@ -0,0 +1,403 @@
+<?php
+
+/*
+ * Utility functions to generate data synced to wpcom
+ */
+
+class Jetpack_Sync_Functions {
+	const HTTPS_CHECK_OPTION_PREFIX = 'jetpack_sync_https_history_';
+	const HTTPS_CHECK_HISTORY       = 5;
+
+	public static function get_modules() {
+		require_once JETPACK__PLUGIN_DIR . 'class.jetpack-admin.php';
+
+		return Jetpack_Admin::init()->get_modules();
+	}
+
+	public static function get_taxonomies() {
+		global $wp_taxonomies;
+		$wp_taxonomies_without_callbacks = array();
+		foreach ( $wp_taxonomies as $taxonomy_name => $taxonomy ) {
+			$sanitized_taxonomy = self::sanitize_taxonomy( $taxonomy );
+			if ( ! empty( $sanitized_taxonomy ) ) {
+				$wp_taxonomies_without_callbacks[ $taxonomy_name ] = $sanitized_taxonomy;
+			} else {
+				error_log( 'Jetpack: Encountered a recusive taxonomy:' . $taxonomy_name );
+			}
+		}
+		return $wp_taxonomies_without_callbacks;
+	}
+
+	public static function get_shortcodes() {
+		global $shortcode_tags;
+		return array_keys( $shortcode_tags );
+	}
+
+	/**
+	 * Removes any callback data since we will not be able to process it on our side anyways.
+	 */
+	public static function sanitize_taxonomy( $taxonomy ) {
+
+		// Lets clone the taxonomy object instead of modifing the global one.
+		$cloned_taxonomy = json_decode( wp_json_encode( $taxonomy ) );
+
+		// recursive taxonomies are no fun.
+		if ( is_null( $cloned_taxonomy ) ) {
+			return null;
+		}
+		// Remove any meta_box_cb if they are not the default wp ones.
+		if ( isset( $cloned_taxonomy->meta_box_cb ) &&
+			 ! in_array( $cloned_taxonomy->meta_box_cb, array( 'post_tags_meta_box', 'post_categories_meta_box' ) ) ) {
+			$cloned_taxonomy->meta_box_cb = null;
+		}
+		// Remove update call back
+		if ( isset( $cloned_taxonomy->update_count_callback ) &&
+			 ! is_null( $cloned_taxonomy->update_count_callback ) ) {
+			$cloned_taxonomy->update_count_callback = null;
+		}
+		// Remove rest_controller_class if it something other then the default.
+		if ( isset( $cloned_taxonomy->rest_controller_class ) &&
+			 'WP_REST_Terms_Controller' !== $cloned_taxonomy->rest_controller_class ) {
+			$cloned_taxonomy->rest_controller_class = null;
+		}
+		return $cloned_taxonomy;
+	}
+
+	public static function get_post_types() {
+		global $wp_post_types;
+
+		$post_types_without_callbacks = array();
+		foreach ( $wp_post_types as $post_type_name => $post_type ) {
+			$sanitized_post_type = self::sanitize_post_type( $post_type );
+			if ( ! empty( $sanitized_post_type ) ) {
+				$post_types_without_callbacks[ $post_type_name ] = $sanitized_post_type;
+			} else {
+				error_log( 'Jetpack: Encountered a recusive post_type:' . $post_type_name );
+			}
+		}
+		return $post_types_without_callbacks;
+	}
+
+	public static function sanitize_post_type( $post_type ) {
+		// Lets clone the post type object instead of modifing the global one.
+		$sanitized_post_type = array();
+		foreach ( Jetpack_Sync_Defaults::$default_post_type_attributes as $attribute_key => $default_value ) {
+			if ( isset( $post_type->{ $attribute_key } ) ) {
+				$sanitized_post_type[ $attribute_key ] = $post_type->{ $attribute_key };
+			}
+		}
+		return (object) $sanitized_post_type;
+	}
+
+	public static function expand_synced_post_type( $sanitized_post_type, $post_type ) {
+		$post_type        = sanitize_key( $post_type );
+		$post_type_object = new WP_Post_Type( $post_type, $sanitized_post_type );
+		$post_type_object->add_supports();
+		$post_type_object->add_rewrite_rules();
+		$post_type_object->add_hooks();
+		$post_type_object->register_taxonomies();
+		return (object) $post_type_object;
+	}
+
+	public static function get_post_type_features() {
+		global $_wp_post_type_features;
+
+		return $_wp_post_type_features;
+	}
+
+	public static function get_hosting_provider() {
+		if ( defined( 'GD_SYSTEM_PLUGIN_DIR' ) || class_exists( '\\WPaaS\\Plugin' ) ) {
+			return 'gd-managed-wp';
+		}
+		if ( defined( 'MM_BASE_DIR' ) ) {
+			return 'bh';
+		}
+		if ( defined( 'IS_PRESSABLE' ) ) {
+			return 'pressable';
+		}
+		if ( function_exists( 'is_wpe' ) || function_exists( 'is_wpe_snapshot' ) ) {
+			return 'wpe';
+		}
+		if ( defined( 'VIP_GO_ENV' ) && false !== VIP_GO_ENV ) {
+			return 'vip-go';
+		}
+		return 'unknown';
+	}
+
+	public static function rest_api_allowed_post_types() {
+		/** This filter is already documented in class.json-api-endpoints.php */
+		return apply_filters( 'rest_api_allowed_post_types', array( 'post', 'page', 'revision' ) );
+	}
+
+	public static function rest_api_allowed_public_metadata() {
+		/** This filter is documented in json-endpoints/class.wpcom-json-api-post-endpoint.php */
+		return apply_filters( 'rest_api_allowed_public_metadata', array() );
+	}
+
+	/**
+	 * Finds out if a site is using a version control system.
+	 *
+	 * @return bool
+	 **/
+	public static function is_version_controlled() {
+
+		if ( ! class_exists( 'WP_Automatic_Updater' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
+		}
+		$updater = new WP_Automatic_Updater();
+
+		return (bool) strval( $updater->is_vcs_checkout( $context = ABSPATH ) );
+	}
+
+	/**
+	 * Returns true if the site has file write access false otherwise.
+	 *
+	 * @return bool
+	 **/
+	public static function file_system_write_access() {
+		if ( ! function_exists( 'get_filesystem_method' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/file.php';
+		}
+
+		require_once ABSPATH . 'wp-admin/includes/template.php';
+
+		$filesystem_method = get_filesystem_method();
+		if ( 'direct' === $filesystem_method ) {
+			return true;
+		}
+
+		ob_start();
+
+		if ( ! function_exists( 'request_filesystem_credentials' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/file.php';
+		}
+
+		$filesystem_credentials_are_stored = request_filesystem_credentials( self_admin_url() );
+		ob_end_clean();
+		if ( $filesystem_credentials_are_stored ) {
+			return true;
+		}
+
+		return false;
+	}
+
+	/**
+	 * Helper function that is used when getting home or siteurl values. Decides
+	 * whether to get the raw or filtered value.
+	 *
+	 * @return string
+	 */
+	public static function get_raw_or_filtered_url( $url_type ) {
+		$url_function = ( 'home' == $url_type )
+			? 'home_url'
+			: 'site_url';
+
+		if (
+			! Jetpack_Constants::is_defined( 'JETPACK_SYNC_USE_RAW_URL' ) ||
+			Jetpack_Constants::get_constant( 'JETPACK_SYNC_USE_RAW_URL' )
+		) {
+			$scheme = is_ssl() ? 'https' : 'http';
+			$url    = self::get_raw_url( $url_type );
+			$url    = set_url_scheme( $url, $scheme );
+		} else {
+			$url = self::normalize_www_in_url( $url_type, $url_function );
+		}
+
+		return self::get_protocol_normalized_url( $url_function, $url );
+	}
+
+	public static function home_url() {
+		$url = self::get_raw_or_filtered_url( 'home' );
+
+		/**
+		 * Allows overriding of the home_url value that is synced back to WordPress.com.
+		 *
+		 * @since 5.2.0
+		 *
+		 * @param string $home_url
+		 */
+		return esc_url_raw( apply_filters( 'jetpack_sync_home_url', $url ) );
+	}
+
+	public static function site_url() {
+		$url = self::get_raw_or_filtered_url( 'siteurl' );
+
+		/**
+		 * Allows overriding of the site_url value that is synced back to WordPress.com.
+		 *
+		 * @since 5.2.0
+		 *
+		 * @param string $site_url
+		 */
+		return esc_url_raw( apply_filters( 'jetpack_sync_site_url', $url ) );
+	}
+
+	public static function main_network_site_url() {
+		return self::get_protocol_normalized_url( 'main_network_site_url', network_site_url() );
+	}
+
+	public static function get_protocol_normalized_url( $callable, $new_value ) {
+		$option_key = self::HTTPS_CHECK_OPTION_PREFIX . $callable;
+
+		$parsed_url = wp_parse_url( $new_value );
+		if ( ! $parsed_url ) {
+			return $new_value;
+		}
+		if ( array_key_exists( 'scheme', $parsed_url ) ) {
+			$scheme = $parsed_url['scheme'];
+		} else {
+			$scheme = '';
+		}
+		$scheme_history   = get_option( $option_key, array() );
+		$scheme_history[] = $scheme;
+
+		// Limit length to self::HTTPS_CHECK_HISTORY
+		$scheme_history = array_slice( $scheme_history, ( self::HTTPS_CHECK_HISTORY * -1 ) );
+
+		update_option( $option_key, $scheme_history );
+
+		$forced_scheme = in_array( 'https', $scheme_history ) ? 'https' : 'http';
+
+		return set_url_scheme( $new_value, $forced_scheme );
+	}
+
+	public static function get_raw_url( $option_name ) {
+		$value    = null;
+		$constant = ( 'home' == $option_name )
+			? 'WP_HOME'
+			: 'WP_SITEURL';
+
+		// Since we disregard the constant for multisites in ms-default-filters.php,
+		// let's also use the db value if this is a multisite.
+		if ( ! is_multisite() && Jetpack_Constants::is_defined( $constant ) ) {
+			$value = Jetpack_Constants::get_constant( $constant );
+		} else {
+			// Let's get the option from the database so that we can bypass filters. This will help
+			// ensure that we get more uniform values.
+			$value = Jetpack_Options::get_raw_option( $option_name );
+		}
+
+		return $value;
+	}
+
+	public static function normalize_www_in_url( $option, $url_function ) {
+		$url        = wp_parse_url( call_user_func( $url_function ) );
+		$option_url = wp_parse_url( get_option( $option ) );
+
+		if ( ! $option_url || ! $url ) {
+			return $url;
+		}
+
+		if ( $url['host'] === "www.{$option_url[ 'host' ]}" ) {
+			// remove www if not present in option URL
+			$url['host'] = $option_url['host'];
+		}
+		if ( $option_url['host'] === "www.{$url[ 'host' ]}" ) {
+			// add www if present in option URL
+			$url['host'] = $option_url['host'];
+		}
+
+		$normalized_url = "{$url['scheme']}://{$url['host']}";
+		if ( isset( $url['path'] ) ) {
+			$normalized_url .= "{$url['path']}";
+		}
+
+		if ( isset( $url['query'] ) ) {
+			$normalized_url .= "?{$url['query']}";
+		}
+
+		return $normalized_url;
+	}
+
+	public static function get_plugins() {
+		if ( ! function_exists( 'get_plugins' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/plugin.php';
+		}
+
+		/** This filter is documented in wp-admin/includes/class-wp-plugins-list-table.php */
+		return apply_filters( 'all_plugins', get_plugins() );
+	}
+
+	/**
+	 * Get custom action link tags that the plugin is using
+	 * Ref: https://codex.wordpress.org/Plugin_API/Filter_Reference/plugin_action_links_(plugin_file_name)
+	 *
+	 * @return array of plugin action links (key: link name value: url)
+	 */
+	public static function get_plugins_action_links( $plugin_file_singular = null ) {
+		// Some sites may have DOM disabled in PHP fail early
+		if ( ! class_exists( 'DOMDocument' ) ) {
+			return array();
+		}
+		$plugins_action_links = get_option( 'jetpack_plugin_api_action_links', array() );
+		if ( ! empty( $plugins_action_links ) ) {
+			if ( is_null( $plugin_file_singular ) ) {
+				return $plugins_action_links;
+			}
+			return ( isset( $plugins_action_links[ $plugin_file_singular ] ) ? $plugins_action_links[ $plugin_file_singular ] : null );
+		}
+		return array();
+	}
+
+	public static function wp_version() {
+		global $wp_version;
+		return $wp_version;
+	}
+
+	public static function site_icon_url( $size = 512 ) {
+		$site_icon = get_site_icon_url( $size );
+		return $site_icon ? $site_icon : get_option( 'jetpack_site_icon_url' );
+	}
+
+	public static function roles() {
+		$wp_roles = wp_roles();
+		return $wp_roles->roles;
+	}
+
+	/**
+	 * Determine time zone from WordPress' options "timezone_string"
+	 * and "gmt_offset".
+	 *
+	 * 1. Check if `timezone_string` is set and return it.
+	 * 2. Check if `gmt_offset` is set, formats UTC-offset from it and return it.
+	 * 3. Default to "UTC+0" if nothing is set.
+	 *
+	 * @return string
+	 */
+	public static function get_timezone() {
+		$timezone_string = get_option( 'timezone_string' );
+
+		if ( ! empty( $timezone_string ) ) {
+			return str_replace( '_', ' ', $timezone_string );
+		}
+
+		$gmt_offset = get_option( 'gmt_offset', 0 );
+
+		$formatted_gmt_offset = sprintf( '%+g', floatval( $gmt_offset ) );
+
+		$formatted_gmt_offset = str_replace(
+			array( '.25', '.5', '.75' ),
+			array( ':15', ':30', ':45' ),
+			(string) $formatted_gmt_offset
+		);
+
+		/* translators: %s is UTC offset, e.g. "+1" */
+		return sprintf( __( 'UTC%s', 'jetpack' ), $formatted_gmt_offset );
+	}
+	// New in WP 5.1
+	public static function get_paused_themes() {
+		if ( function_exists( 'wp_paused_themes' ) ) {
+			$paused_themes = wp_paused_themes();
+			return $paused_themes->get_all();
+		}
+		return false;
+	}
+	// New in WP 5.1
+	public static function get_paused_plugins() {
+		if ( function_exists( 'wp_paused_plugins' ) ) {
+			$paused_plugins = wp_paused_plugins();
+			return $paused_plugins->get_all();
+		}
+		return false;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-json-deflate-array-codec.php b/plugins/jetpack/sync/class.jetpack-sync-json-deflate-array-codec.php
new file mode 100644
index 00000000..04d3dd7d
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-json-deflate-array-codec.php
@@ -0,0 +1,84 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/interface.jetpack-sync-codec.php';
+
+/**
+ * An implementation of iJetpack_Sync_Codec that uses gzip's DEFLATE
+ * algorithm to compress objects serialized using json_encode
+ */
+class Jetpack_Sync_JSON_Deflate_Array_Codec implements iJetpack_Sync_Codec {
+	const CODEC_NAME = 'deflate-json-array';
+
+	public function name() {
+		return self::CODEC_NAME;
+	}
+
+	public function encode( $object ) {
+		return base64_encode( gzdeflate( $this->json_serialize( $object ) ) );
+	}
+
+	public function decode( $input ) {
+		return $this->json_unserialize( gzinflate( base64_decode( $input ) ) );
+	}
+
+	// @see https://gist.github.com/muhqu/820694
+	protected function json_serialize( $any ) {
+		if ( function_exists( 'jetpack_json_wrap' ) ) {
+			return wp_json_encode( jetpack_json_wrap( $any ) );
+		}
+		// This prevents fatal error when updating pre 6.0 via the cli command
+		return wp_json_encode( $this->json_wrap( $any ) );
+	}
+
+	protected function json_unserialize( $str ) {
+		return $this->json_unwrap( json_decode( $str, true ) );
+	}
+
+	private function json_wrap( &$any, $seen_nodes = array() ) {
+		if ( is_object( $any ) ) {
+			$input        = get_object_vars( $any );
+			$input['__o'] = 1;
+		} else {
+			$input = &$any;
+		}
+
+		if ( is_array( $input ) ) {
+			$seen_nodes[] = &$any;
+
+			$return = array();
+
+			foreach ( $input as $k => &$v ) {
+				if ( ( is_array( $v ) || is_object( $v ) ) ) {
+					if ( in_array( $v, $seen_nodes, true ) ) {
+						continue;
+					}
+					$return[ $k ] = $this->json_wrap( $v, $seen_nodes );
+				} else {
+					$return[ $k ] = $v;
+				}
+			}
+
+			return $return;
+		}
+
+		return $any;
+	}
+
+	private function json_unwrap( $any ) {
+		if ( is_array( $any ) ) {
+			foreach ( $any as $k => $v ) {
+				if ( '__o' === $k ) {
+					continue;
+				}
+				$any[ $k ] = $this->json_unwrap( $v );
+			}
+
+			if ( isset( $any['__o'] ) ) {
+				unset( $any['__o'] );
+				$any = (object) $any;
+			}
+		}
+
+		return $any;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-listener.php b/plugins/jetpack/sync/class.jetpack-sync-listener.php
new file mode 100644
index 00000000..62abc0d2
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-listener.php
@@ -0,0 +1,329 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-queue.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-modules.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-actions.php';
+
+/**
+ * This class monitors actions and logs them to the queue to be sent
+ */
+class Jetpack_Sync_Listener {
+	const QUEUE_STATE_CHECK_TRANSIENT = 'jetpack_sync_last_checked_queue_state';
+	const QUEUE_STATE_CHECK_TIMEOUT   = 300; // 5 minutes
+
+	private $sync_queue;
+	private $full_sync_queue;
+	private $sync_queue_size_limit;
+	private $sync_queue_lag_limit;
+
+	// singleton functions
+	private static $instance;
+
+	public static function get_instance() {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+
+		return self::$instance;
+	}
+
+	// this is necessary because you can't use "new" when you declare instance properties >:(
+	protected function __construct() {
+		$this->set_defaults();
+		$this->init();
+	}
+
+	private function init() {
+		$handler           = array( $this, 'action_handler' );
+		$full_sync_handler = array( $this, 'full_sync_action_handler' );
+
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$module->init_listeners( $handler );
+			$module->init_full_sync_listeners( $full_sync_handler );
+		}
+
+		// Module Activation
+		add_action( 'jetpack_activate_module', $handler );
+		add_action( 'jetpack_deactivate_module', $handler );
+
+		// Jetpack Upgrade
+		add_action( 'updating_jetpack_version', $handler, 10, 2 );
+
+		// Send periodic checksum
+		add_action( 'jetpack_sync_checksum', $handler );
+	}
+
+	function get_sync_queue() {
+		return $this->sync_queue;
+	}
+
+	function get_full_sync_queue() {
+		return $this->full_sync_queue;
+	}
+
+	function set_queue_size_limit( $limit ) {
+		$this->sync_queue_size_limit = $limit;
+	}
+
+	function get_queue_size_limit() {
+		return $this->sync_queue_size_limit;
+	}
+
+	function set_queue_lag_limit( $age ) {
+		$this->sync_queue_lag_limit = $age;
+	}
+
+	function get_queue_lag_limit() {
+		return $this->sync_queue_lag_limit;
+	}
+
+	function force_recheck_queue_limit() {
+		delete_transient( self::QUEUE_STATE_CHECK_TRANSIENT . '_' . $this->sync_queue->id );
+		delete_transient( self::QUEUE_STATE_CHECK_TRANSIENT . '_' . $this->full_sync_queue->id );
+	}
+
+	// prevent adding items to the queue if it hasn't sent an item for 15 mins
+	// AND the queue is over 1000 items long (by default)
+	function can_add_to_queue( $queue ) {
+		if ( ! Jetpack_Sync_Settings::is_sync_enabled() ) {
+			return false;
+		}
+
+		$state_transient_name = self::QUEUE_STATE_CHECK_TRANSIENT . '_' . $queue->id;
+
+		$queue_state = get_transient( $state_transient_name );
+
+		if ( false === $queue_state ) {
+			$queue_state = array( $queue->size(), $queue->lag() );
+			set_transient( $state_transient_name, $queue_state, self::QUEUE_STATE_CHECK_TIMEOUT );
+		}
+
+		list( $queue_size, $queue_age ) = $queue_state;
+
+		return ( $queue_age < $this->sync_queue_lag_limit )
+			   ||
+			   ( ( $queue_size + 1 ) < $this->sync_queue_size_limit );
+	}
+
+	function full_sync_action_handler() {
+		$args = func_get_args();
+		$this->enqueue_action( current_filter(), $args, $this->full_sync_queue );
+	}
+
+	function action_handler() {
+		$args = func_get_args();
+		$this->enqueue_action( current_filter(), $args, $this->sync_queue );
+	}
+
+	// add many actions to the queue directly, without invoking them
+
+	/**
+	 * Bulk add action to the queue.
+	 *
+	 * @param $action_name String the name the full sync action.
+	 * @param $args_array Array of chunked arguments
+	 */
+	function bulk_enqueue_full_sync_actions( $action_name, $args_array ) {
+		$queue = $this->get_full_sync_queue();
+
+		// periodically check the size of the queue, and disable adding to it if
+		// it exceeds some limit AND the oldest item exceeds the age limit (i.e. sending has stopped)
+		if ( ! $this->can_add_to_queue( $queue ) ) {
+			return;
+		}
+
+		// if we add any items to the queue, we should try to ensure that our script
+		// can't be killed before they are sent
+		if ( function_exists( 'ignore_user_abort' ) ) {
+			ignore_user_abort( true );
+		}
+
+		$data_to_enqueue = array();
+		$user_id         = get_current_user_id();
+		$currtime        = microtime( true );
+		$is_importing    = Jetpack_Sync_Settings::is_importing();
+
+		foreach ( $args_array as $args ) {
+			$previous_end = isset( $args['previous_end'] ) ? $args['previous_end'] : null;
+			$args = isset( $args['ids'] ) ? $args['ids'] : $args;
+
+
+			/**
+			 * Modify or reject the data within an action before it is enqueued locally.
+			 *
+			 * @since 4.2.0
+			 *
+			 * @module sync
+			 *
+			 * @param array The action parameters
+			 */
+			$args = apply_filters( "jetpack_sync_before_enqueue_$action_name", $args );
+			$action_data = array( $args );
+			if ( ! is_null( $previous_end ) ) {
+				$action_data[] = $previous_end;
+			}
+			// allow listeners to abort
+			if ( $args === false ) {
+				continue;
+			}
+
+			$data_to_enqueue[] = array(
+				$action_name,
+				$action_data,
+				$user_id,
+				$currtime,
+				$is_importing,
+			);
+		}
+
+		$queue->add_all( $data_to_enqueue );
+	}
+
+	function enqueue_action( $current_filter, $args, $queue ) {
+		// don't enqueue an action during the outbound http request - this prevents recursion
+		if ( Jetpack_Sync_Settings::is_sending() ) {
+			return;
+		}
+
+		/**
+		 * Add an action hook to execute when anything on the whitelist gets sent to the queue to sync.
+		 *
+		 * @module sync
+		 *
+		 * @since 5.9.0
+		 */
+		do_action( 'jetpack_sync_action_before_enqueue' );
+
+		/**
+		 * Modify or reject the data within an action before it is enqueued locally.
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param array The action parameters
+		 */
+		$args = apply_filters( "jetpack_sync_before_enqueue_$current_filter", $args );
+
+		// allow listeners to abort
+		if ( $args === false ) {
+			return;
+		}
+
+		// periodically check the size of the queue, and disable adding to it if
+		// it exceeds some limit AND the oldest item exceeds the age limit (i.e. sending has stopped)
+		if ( ! $this->can_add_to_queue( $queue ) ) {
+			return;
+		}
+
+		// if we add any items to the queue, we should try to ensure that our script
+		// can't be killed before they are sent
+		if ( function_exists( 'ignore_user_abort' ) ) {
+			ignore_user_abort( true );
+		}
+
+		if (
+			'sync' === $queue->id ||
+			in_array(
+				$current_filter,
+				array(
+					'jetpack_full_sync_start',
+					'jetpack_full_sync_end',
+					'jetpack_full_sync_cancel',
+				)
+			)
+		) {
+			$queue->add(
+				array(
+					$current_filter,
+					$args,
+					get_current_user_id(),
+					microtime( true ),
+					Jetpack_Sync_Settings::is_importing(),
+					$this->get_actor( $current_filter, $args ),
+				)
+			);
+		} else {
+			$queue->add(
+				array(
+					$current_filter,
+					$args,
+					get_current_user_id(),
+					microtime( true ),
+					Jetpack_Sync_Settings::is_importing(),
+				)
+			);
+		}
+
+		// since we've added some items, let's try to load the sender so we can send them as quickly as possible
+		if ( ! Jetpack_Sync_Actions::$sender ) {
+			add_filter( 'jetpack_sync_sender_should_load', '__return_true' );
+			if ( did_action( 'init' ) ) {
+				Jetpack_Sync_Actions::add_sender_shutdown();
+			}
+		}
+	}
+
+	function get_actor( $current_filter, $args ) {
+		if ( 'wp_login' === $current_filter ) {
+			$user = get_user_by( 'ID', $args[1]->data->ID );
+		} else {
+			$user = wp_get_current_user();
+		}
+
+		$translated_role = Jetpack::translate_user_to_role( $user );
+
+		$actor = array(
+			'wpcom_user_id'    => null,
+			'external_user_id' => isset( $user->ID ) ? $user->ID : null,
+			'display_name'     => isset( $user->display_name ) ? $user->display_name : null,
+			'user_email'       => isset( $user->user_email ) ? $user->user_email : null,
+			'user_roles'       => isset( $user->roles ) ? $user->roles : null,
+			'translated_role'  => $translated_role ? $translated_role : null,
+			'is_cron'          => defined( 'DOING_CRON' ) ? DOING_CRON : false,
+			'is_rest'          => defined( 'REST_API_REQUEST' ) ? REST_API_REQUEST : false,
+			'is_xmlrpc'        => defined( 'XMLRPC_REQUEST' ) ? XMLRPC_REQUEST : false,
+			'is_wp_rest'       => defined( 'REST_REQUEST' ) ? REST_REQUEST : false,
+			'is_ajax'          => defined( 'DOING_AJAX' ) ? DOING_AJAX : false,
+			'is_wp_admin'      => is_admin(),
+			'is_cli'           => defined( 'WP_CLI' ) ? WP_CLI : false,
+			'from_url'         => $this->get_request_url(),
+		);
+
+		if ( $this->should_send_user_data_with_actor( $current_filter ) ) {
+			require_once JETPACK__PLUGIN_DIR . 'modules/protect/shared-functions.php';
+			$actor['ip']         = jetpack_protect_get_ip();
+			$actor['user_agent'] = isset( $_SERVER['HTTP_USER_AGENT'] ) ? $_SERVER['HTTP_USER_AGENT'] : 'unknown';
+		}
+
+		return $actor;
+	}
+
+	function should_send_user_data_with_actor( $current_filter ) {
+		$should_send = in_array( $current_filter, array( 'jetpack_wp_login', 'wp_logout', 'jetpack_valid_failed_login_attempt' ) );
+		/**
+		 * Allow or deny sending actor's user data ( IP and UA ) during a sync event
+		 *
+		 * @since 5.8.0
+		 *
+		 * @module sync
+		 *
+		 * @param bool True if we should send user data
+		 * @param string The current filter that is performing the sync action
+		 */
+		return apply_filters( 'jetpack_sync_actor_user_data', $should_send, $current_filter );
+	}
+
+	function set_defaults() {
+		$this->sync_queue      = new Jetpack_Sync_Queue( 'sync' );
+		$this->full_sync_queue = new Jetpack_Sync_Queue( 'full_sync' );
+		$this->set_queue_size_limit( Jetpack_Sync_Settings::get_setting( 'max_queue_size' ) );
+		$this->set_queue_lag_limit( Jetpack_Sync_Settings::get_setting( 'max_queue_lag' ) );
+	}
+
+	function get_request_url() {
+		if ( isset( $_SERVER['HTTP_HOST'], $_SERVER['REQUEST_URI'] ) ) {
+			return 'http' . ( isset( $_SERVER['HTTPS'] ) ? 's' : '' ) . '://' . "{$_SERVER['HTTP_HOST']}{$_SERVER['REQUEST_URI']}";
+		}
+		return is_admin() ? get_admin_url( get_current_blog_id() ) : home_url();
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-attachments.php b/plugins/jetpack/sync/class.jetpack-sync-module-attachments.php
new file mode 100644
index 00000000..f68ba832
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-attachments.php
@@ -0,0 +1,55 @@
+<?php
+
+class Jetpack_Sync_Module_Attachments extends Jetpack_Sync_Module {
+	function name() {
+		return 'attachments';
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'add_attachment', array( $this, 'process_add' ) );
+		add_action( 'attachment_updated', array( $this, 'process_update' ), 10, 3 );
+		add_action( 'jetpack_sync_save_update_attachment', $callable, 10, 2 );
+		add_action( 'jetpack_sync_save_add_attachment', $callable, 10, 2 );
+		add_action( 'jetpack_sync_save_attach_attachment', $callable, 10, 2 );
+	}
+
+	function process_add( $attachment_id ) {
+		$attachment = get_post( $attachment_id );
+		/**
+		 * Fires when the client needs to sync an new attachment
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param int The attachment ID
+		 * @param object The attachment
+		 */
+		do_action( 'jetpack_sync_save_add_attachment', $attachment_id, $attachment );
+	}
+
+	function process_update( $attachment_id, $attachment_after, $attachment_before ) {
+		// Check whether attachment was added to a post for the first time
+		if ( 0 === $attachment_before->post_parent && 0 !== $attachment_after->post_parent ) {
+			/**
+			 * Fires when an existing attachment is added to a post for the first time
+			 *
+			 * @since 6.6.0
+			 *
+			 * @param int The attachment ID
+			 * @param object The attachment
+			 */
+			do_action( 'jetpack_sync_save_attach_attachment', $attachment_id, $attachment_after );
+		} else {
+			/**
+			 * Fires when the client needs to sync an updated attachment
+			 *
+			 * @since 4.9.0
+			 *
+			 * @param int The attachment ID
+			 * @param object The attachment
+			 *
+			 * Previously this action was synced using jetpack_sync_save_add_attachment action.
+			 */
+			do_action( 'jetpack_sync_save_update_attachment', $attachment_id, $attachment_after );
+		}
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-callables.php b/plugins/jetpack/sync/class.jetpack-sync-module-callables.php
new file mode 100644
index 00000000..d46d5514
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-callables.php
@@ -0,0 +1,273 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-functions.php';
+
+class Jetpack_Sync_Module_Callables extends Jetpack_Sync_Module {
+	const CALLABLES_CHECKSUM_OPTION_NAME = 'jetpack_callables_sync_checksum';
+	const CALLABLES_AWAIT_TRANSIENT_NAME = 'jetpack_sync_callables_await';
+
+	private $callable_whitelist;
+
+	public function name() {
+		return 'functions';
+	}
+
+	public function set_defaults() {
+		if ( is_multisite() ) {
+			$this->callable_whitelist = array_merge( Jetpack_Sync_Defaults::get_callable_whitelist(), Jetpack_Sync_Defaults::get_multisite_callable_whitelist() );
+		} else {
+			$this->callable_whitelist = Jetpack_Sync_Defaults::get_callable_whitelist();
+		}
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'jetpack_sync_callable', $callable, 10, 2 );
+		add_action( 'current_screen', array( $this, 'set_plugin_action_links' ), 9999 ); // Should happen very late
+
+		// For some options, we should always send the change right away!
+		$always_send_updates_to_these_options = array(
+			'jetpack_active_modules',
+			'home',
+			'siteurl',
+			'jetpack_sync_error_idc',
+			'paused_plugins',
+			'paused_themes',
+		);
+		foreach ( $always_send_updates_to_these_options as $option ) {
+			add_action( "update_option_{$option}", array( $this, 'unlock_sync_callable' ) );
+			add_action( "delete_option_{$option}", array( $this, 'unlock_sync_callable' ) );
+		}
+
+		// Provide a hook so that hosts can send changes to certain callables right away.
+		// Especially useful when a host uses constants to change home and siteurl.
+		add_action( 'jetpack_sync_unlock_sync_callable', array( $this, 'unlock_sync_callable' ) );
+
+		// get_plugins and wp_version
+		// gets fired when new code gets installed, updates etc.
+		add_action( 'upgrader_process_complete', array( $this, 'unlock_plugin_action_link_and_callables' ) );
+		add_action( 'update_option_active_plugins', array( $this, 'unlock_plugin_action_link_and_callables' ) );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_callables', $callable );
+	}
+
+	public function init_before_send() {
+		add_action( 'jetpack_sync_before_send_queue_sync', array( $this, 'maybe_sync_callables' ) );
+
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_callables', array( $this, 'expand_callables' ) );
+	}
+
+	public function reset_data() {
+		delete_option( self::CALLABLES_CHECKSUM_OPTION_NAME );
+		delete_transient( self::CALLABLES_AWAIT_TRANSIENT_NAME );
+
+		$url_callables = array( 'home_url', 'site_url', 'main_network_site_url' );
+		foreach ( $url_callables as $callable ) {
+			delete_option( Jetpack_Sync_Functions::HTTPS_CHECK_OPTION_PREFIX . $callable );
+		}
+	}
+
+	function set_callable_whitelist( $callables ) {
+		$this->callable_whitelist = $callables;
+	}
+
+	function get_callable_whitelist() {
+		return $this->callable_whitelist;
+	}
+
+	public function get_all_callables() {
+		// get_all_callables should run as the master user always.
+		$current_user_id = get_current_user_id();
+		wp_set_current_user( Jetpack_Options::get_option( 'master_user' ) );
+		$callables = array_combine(
+			array_keys( $this->get_callable_whitelist() ),
+			array_map( array( $this, 'get_callable' ), array_values( $this->get_callable_whitelist() ) )
+		);
+		wp_set_current_user( $current_user_id );
+		return $callables;
+	}
+
+	private function get_callable( $callable ) {
+		return call_user_func( $callable );
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		/**
+		 * Tells the client to sync all callables to the server
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean Whether to expand callables (should always be true)
+		 */
+		do_action( 'jetpack_full_sync_callables', true );
+
+		// The number of actions enqueued, and next module state (true == done)
+		return array( 1, true );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		return 1;
+	}
+
+	public function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_callables' );
+	}
+
+	public function unlock_sync_callable() {
+		delete_transient( self::CALLABLES_AWAIT_TRANSIENT_NAME );
+	}
+
+	public function unlock_plugin_action_link_and_callables() {
+		delete_transient( self::CALLABLES_AWAIT_TRANSIENT_NAME );
+		delete_transient( 'jetpack_plugin_api_action_links_refresh' );
+		add_filter( 'jetpack_check_and_send_callables', '__return_true' );
+	}
+
+	public function set_plugin_action_links() {
+		if (
+			! class_exists( 'DOMDocument' ) ||
+			! function_exists( 'libxml_use_internal_errors' ) ||
+			! function_exists( 'mb_convert_encoding' )
+		) {
+			return;
+		}
+
+		$current_screeen = get_current_screen();
+
+		$plugins_action_links = array();
+		// Is the transient lock in place?
+		$plugins_lock = get_transient( 'jetpack_plugin_api_action_links_refresh', false );
+		if ( ! empty( $plugins_lock ) && ( isset( $current_screeen->id ) && $current_screeen->id !== 'plugins' ) ) {
+			return;
+		}
+		$plugins = array_keys( Jetpack_Sync_Functions::get_plugins() );
+		foreach ( $plugins as $plugin_file ) {
+			/**
+			 *  Plugins often like to unset things but things break if they are not able to.
+			 */
+			$action_links = array(
+				'deactivate' => '',
+				'activate'   => '',
+				'details'    => '',
+				'delete'     => '',
+				'edit'       => '',
+			);
+			/** This filter is documented in src/wp-admin/includes/class-wp-plugins-list-table.php */
+			$action_links = apply_filters( 'plugin_action_links', $action_links, $plugin_file, null, 'all' );
+			/** This filter is documented in src/wp-admin/includes/class-wp-plugins-list-table.php */
+			$action_links           = apply_filters( "plugin_action_links_{$plugin_file}", $action_links, $plugin_file, null, 'all' );
+			$action_links           = array_filter( $action_links );
+			$formatted_action_links = null;
+			if ( ! empty( $action_links ) && count( $action_links ) > 0 ) {
+				$dom_doc = new DOMDocument();
+				foreach ( $action_links as $action_link ) {
+					// The @ is not enough to suppress errors when dealing with libxml,
+					// we have to tell it directly how we want to handle errors.
+					libxml_use_internal_errors( true );
+					$dom_doc->loadHTML( mb_convert_encoding( $action_link, 'HTML-ENTITIES', 'UTF-8' ) );
+					libxml_use_internal_errors( false );
+
+					$link_elements = $dom_doc->getElementsByTagName( 'a' );
+					if ( $link_elements->length == 0 ) {
+						continue;
+					}
+
+					$link_element = $link_elements->item( 0 );
+					if ( $link_element->hasAttribute( 'href' ) && $link_element->nodeValue ) {
+						$link_url = trim( $link_element->getAttribute( 'href' ) );
+
+						// Add the full admin path to the url if the plugin did not provide it
+						$link_url_scheme = wp_parse_url( $link_url, PHP_URL_SCHEME );
+						if ( empty( $link_url_scheme ) ) {
+							$link_url = admin_url( $link_url );
+						}
+
+						$formatted_action_links[ $link_element->nodeValue ] = $link_url;
+					}
+				}
+			}
+			if ( $formatted_action_links ) {
+				$plugins_action_links[ $plugin_file ] = $formatted_action_links;
+			}
+		}
+		// Cache things for a long time
+		set_transient( 'jetpack_plugin_api_action_links_refresh', time(), DAY_IN_SECONDS );
+		update_option( 'jetpack_plugin_api_action_links', $plugins_action_links );
+	}
+
+	public function should_send_callable( $callable_checksums, $name, $checksum ) {
+		$idc_override_callables = array(
+			'main_network_site',
+			'home_url',
+			'site_url',
+		);
+		if ( in_array( $name, $idc_override_callables ) && Jetpack_Options::get_option( 'migrate_for_idc' ) ) {
+			return true;
+		}
+
+		return ! $this->still_valid_checksum( $callable_checksums, $name, $checksum );
+	}
+
+	public function maybe_sync_callables() {
+		if ( ! apply_filters( 'jetpack_check_and_send_callables', false ) ) {
+			if ( ! is_admin() || Jetpack_Sync_Settings::is_doing_cron() ) {
+				return;
+			}
+
+			if ( get_transient( self::CALLABLES_AWAIT_TRANSIENT_NAME ) ) {
+				return;
+			}
+		}
+
+		set_transient( self::CALLABLES_AWAIT_TRANSIENT_NAME, microtime( true ), Jetpack_Sync_Defaults::$default_sync_callables_wait_time );
+
+		$callables = $this->get_all_callables();
+
+		if ( empty( $callables ) ) {
+			return;
+		}
+
+		$callable_checksums = (array) Jetpack_Options::get_raw_option( self::CALLABLES_CHECKSUM_OPTION_NAME, array() );
+		$has_changed = false;
+		// only send the callables that have changed
+		foreach ( $callables as $name => $value ) {
+			$checksum = $this->get_check_sum( $value );
+			// explicitly not using Identical comparison as get_option returns a string
+			if ( ! is_null( $value ) && $this->should_send_callable( $callable_checksums, $name, $checksum ) ) {
+				/**
+				 * Tells the client to sync a callable (aka function) to the server
+				 *
+				 * @since 4.2.0
+				 *
+				 * @param string The name of the callable
+				 * @param mixed The value of the callable
+				 */
+				do_action( 'jetpack_sync_callable', $name, $value );
+				$callable_checksums[ $name ] = $checksum;
+				$has_changed = true;
+			} else {
+				$callable_checksums[ $name ] = $checksum;
+			}
+		}
+		if ( $has_changed ) {
+			Jetpack_Options::update_raw_option( self::CALLABLES_CHECKSUM_OPTION_NAME, $callable_checksums );
+		}
+
+	}
+
+	public function expand_callables( $args ) {
+		if ( $args[0] ) {
+			$callables           = $this->get_all_callables();
+			$callables_checksums = array();
+			foreach ( $callables as $name => $value ) {
+				$callables_checksums[ $name ] = $this->get_check_sum( $value );
+			}
+			Jetpack_Options::update_raw_option( self::CALLABLES_CHECKSUM_OPTION_NAME, $callables_checksums );
+			return $callables;
+		}
+
+		return $args;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-comments.php b/plugins/jetpack/sync/class.jetpack-sync-module-comments.php
new file mode 100644
index 00000000..0a0ee16f
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-comments.php
@@ -0,0 +1,196 @@
+<?php
+
+class Jetpack_Sync_Module_Comments extends Jetpack_Sync_Module {
+
+	public function name() {
+		return 'comments';
+	}
+
+	public function get_object_by_id( $object_type, $id ) {
+		$comment_id = intval( $id );
+		if ( $object_type === 'comment' && $comment = get_comment( $comment_id ) ) {
+			return $this->filter_comment( $comment );
+		}
+
+		return false;
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'wp_insert_comment', $callable, 10, 2 );
+		add_action( 'deleted_comment', $callable );
+		add_action( 'trashed_comment', $callable );
+		add_action( 'spammed_comment', $callable );
+		add_action( 'trashed_post_comments', $callable, 10, 2 );
+		add_action( 'untrash_post_comments', $callable );
+		add_action( 'comment_approved_to_unapproved', $callable );
+		add_action( 'comment_unapproved_to_approved', $callable );
+		add_action( 'jetpack_modified_comment_contents', $callable, 10, 2 );
+		add_action( 'untrashed_comment', $callable, 10, 2 );
+		add_action( 'unspammed_comment', $callable, 10, 2 );
+		add_filter( 'wp_update_comment_data', array( $this, 'handle_comment_contents_modification' ), 10, 3 );
+
+		// even though it's messy, we implement these hooks because
+		// the edit_comment hook doesn't include the data
+		// so this saves us a DB read for every comment event
+		foreach ( array( '', 'trackback', 'pingback' ) as $comment_type ) {
+			foreach ( array( 'unapproved', 'approved' ) as $comment_status ) {
+				$comment_action_name = "comment_{$comment_status}_{$comment_type}";
+				add_action( $comment_action_name, $callable, 10, 2 );
+			}
+		}
+
+		// listen for meta changes
+		$this->init_listeners_for_meta_type( 'comment', $callable );
+		$this->init_meta_whitelist_handler( 'comment', array( $this, 'filter_meta' ) );
+	}
+
+	public function handle_comment_contents_modification( $new_comment, $old_comment, $new_comment_with_slashes ) {
+		$content_fields = array(
+			'comment_author',
+			'comment_author_email',
+			'comment_author_url',
+			'comment_content',
+		);
+		$changes        = array();
+		foreach ( $content_fields as $field ) {
+			if ( $new_comment_with_slashes[ $field ] != $old_comment[ $field ] ) {
+				$changes[ $field ] = array( $new_comment[ $field ], $old_comment[ $field ] );
+			}
+		}
+
+		if ( ! empty( $changes ) ) {
+			/**
+			 * Signals to the sync listener that this comment's contents were modified and a sync action
+			 * reflecting the change(s) to the content should be sent
+			 *
+			 * @since 4.9.0
+			 *
+			 * @param int $new_comment['comment_ID'] ID of comment whose content was modified
+			 * @param mixed $changes Array of changed comment fields with before and after values
+			 */
+			do_action( 'jetpack_modified_comment_contents', $new_comment['comment_ID'], $changes );
+		}
+		return $new_comment;
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_comments', $callable ); // also send comments meta
+	}
+
+	public function init_before_send() {
+		add_filter( 'jetpack_sync_before_send_wp_insert_comment', array( $this, 'expand_wp_insert_comment' ) );
+
+		foreach ( array( '', 'trackback', 'pingback' ) as $comment_type ) {
+			foreach ( array( 'unapproved', 'approved' ) as $comment_status ) {
+				$comment_action_name = "comment_{$comment_status}_{$comment_type}";
+				add_filter(
+					'jetpack_sync_before_send_' . $comment_action_name,
+					array(
+						$this,
+						'expand_wp_insert_comment',
+					)
+				);
+			}
+		}
+
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_comments', array( $this, 'expand_comment_ids' ) );
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		global $wpdb;
+		return $this->enqueue_all_ids_as_action( 'jetpack_full_sync_comments', $wpdb->comments, 'comment_ID', $this->get_where_sql( $config ), $max_items_to_enqueue, $state );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		global $wpdb;
+
+		$query = "SELECT count(*) FROM $wpdb->comments";
+
+		if ( $where_sql = $this->get_where_sql( $config ) ) {
+			$query .= ' WHERE ' . $where_sql;
+		}
+
+		$count = $wpdb->get_var( $query );
+
+		return (int) ceil( $count / self::ARRAY_CHUNK_SIZE );
+	}
+
+	private function get_where_sql( $config ) {
+		if ( is_array( $config ) ) {
+			return 'comment_ID IN (' . implode( ',', array_map( 'intval', $config ) ) . ')';
+		}
+
+		return null;
+	}
+
+	public function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_comments' );
+	}
+
+	public function count_full_sync_actions( $action_names ) {
+		return $this->count_actions( $action_names, array( 'jetpack_full_sync_comments' ) );
+	}
+
+	function expand_wp_comment_status_change( $args ) {
+		return array( $args[0], $this->filter_comment( $args[1] ) );
+	}
+
+	function expand_wp_insert_comment( $args ) {
+		return array( $args[0], $this->filter_comment( $args[1] ) );
+	}
+
+	function filter_comment( $comment ) {
+		/**
+		 * Filters whether to prevent sending comment data to .com
+		 *
+		 * Passing true to the filter will prevent the comment data from being sent
+		 * to the WordPress.com.
+		 * Instead we pass data that will still enable us to do a checksum against the
+		 * Jetpacks data but will prevent us from displaying the data on in the API as well as
+		 * other services.
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean false prevent post data from bing synced to WordPress.com
+		 * @param mixed $comment WP_COMMENT object
+		 */
+		if ( apply_filters( 'jetpack_sync_prevent_sending_comment_data', false, $comment ) ) {
+			$blocked_comment                   = new stdClass();
+			$blocked_comment->comment_ID       = $comment->comment_ID;
+			$blocked_comment->comment_date     = $comment->comment_date;
+			$blocked_comment->comment_date_gmt = $comment->comment_date_gmt;
+			$blocked_comment->comment_approved = 'jetpack_sync_blocked';
+			return $blocked_comment;
+		}
+
+		return $comment;
+	}
+
+	// Comment Meta
+	function is_whitelisted_comment_meta( $meta_key ) {
+		return in_array( $meta_key, Jetpack_Sync_Settings::get_setting( 'comment_meta_whitelist' ) );
+	}
+
+	function filter_meta( $args ) {
+		return ( $this->is_whitelisted_comment_meta( $args[2] ) ? $args : false );
+	}
+
+	public function expand_comment_ids( $args ) {
+		list( $comment_ids, $previous_interval_end ) = $args;
+		$comments    = get_comments(
+			array(
+				'include_unapproved' => true,
+				'comment__in'        => $comment_ids,
+				'orderby'            => 'comment_ID',
+				'order'              => 'DESC',
+			)
+		);
+
+		return array(
+			$comments,
+			$this->get_metadata( $comment_ids, 'comment', Jetpack_Sync_Settings::get_setting( 'comment_meta_whitelist' ) ),
+			$previous_interval_end,
+		);
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-constants.php b/plugins/jetpack/sync/class.jetpack-sync-module-constants.php
new file mode 100644
index 00000000..f3af3195
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-constants.php
@@ -0,0 +1,125 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-defaults.php';
+
+class Jetpack_Sync_Module_Constants extends Jetpack_Sync_Module {
+	const CONSTANTS_CHECKSUM_OPTION_NAME = 'jetpack_constants_sync_checksum';
+	const CONSTANTS_AWAIT_TRANSIENT_NAME = 'jetpack_sync_constants_await';
+
+	public function name() {
+		return 'constants';
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'jetpack_sync_constant', $callable, 10, 2 );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_constants', $callable );
+	}
+
+	public function init_before_send() {
+		add_action( 'jetpack_sync_before_send_queue_sync', array( $this, 'maybe_sync_constants' ) );
+
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_constants', array( $this, 'expand_constants' ) );
+	}
+
+	public function reset_data() {
+		delete_option( self::CONSTANTS_CHECKSUM_OPTION_NAME );
+		delete_transient( self::CONSTANTS_AWAIT_TRANSIENT_NAME );
+	}
+
+	function set_constants_whitelist( $constants ) {
+		$this->constants_whitelist = $constants;
+	}
+
+	function get_constants_whitelist() {
+		return Jetpack_Sync_Defaults::get_constants_whitelist();
+	}
+
+	function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		/**
+		 * Tells the client to sync all constants to the server
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean Whether to expand constants (should always be true)
+		 */
+		do_action( 'jetpack_full_sync_constants', true );
+
+		// The number of actions enqueued, and next module state (true == done)
+		return array( 1, true );
+	}
+
+	function estimate_full_sync_actions( $config ) {
+		return 1;
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_constants' );
+	}
+
+	function maybe_sync_constants() {
+		if ( get_transient( self::CONSTANTS_AWAIT_TRANSIENT_NAME ) ) {
+			return;
+		}
+
+		set_transient( self::CONSTANTS_AWAIT_TRANSIENT_NAME, microtime( true ), Jetpack_Sync_Defaults::$default_sync_constants_wait_time );
+
+		$constants = $this->get_all_constants();
+		if ( empty( $constants ) ) {
+			return;
+		}
+
+		$constants_checksums = (array) get_option( self::CONSTANTS_CHECKSUM_OPTION_NAME, array() );
+
+		foreach ( $constants as $name => $value ) {
+			$checksum = $this->get_check_sum( $value );
+			// explicitly not using Identical comparison as get_option returns a string
+			if ( ! $this->still_valid_checksum( $constants_checksums, $name, $checksum ) && ! is_null( $value ) ) {
+				/**
+				 * Tells the client to sync a constant to the server
+				 *
+				 * @since 4.2.0
+				 *
+				 * @param string The name of the constant
+				 * @param mixed The value of the constant
+				 */
+				do_action( 'jetpack_sync_constant', $name, $value );
+				$constants_checksums[ $name ] = $checksum;
+			} else {
+				$constants_checksums[ $name ] = $checksum;
+			}
+		}
+		update_option( self::CONSTANTS_CHECKSUM_OPTION_NAME, $constants_checksums );
+	}
+
+	// public so that we don't have to store an option for each constant
+	function get_all_constants() {
+		$constants_whitelist = $this->get_constants_whitelist();
+		return array_combine(
+			$constants_whitelist,
+			array_map( array( $this, 'get_constant' ), $constants_whitelist )
+		);
+	}
+
+	private function get_constant( $constant ) {
+		return ( defined( $constant ) ) ?
+			constant( $constant )
+			: null;
+	}
+
+	public function expand_constants( $args ) {
+		if ( $args[0] ) {
+			$constants           = $this->get_all_constants();
+			$constants_checksums = array();
+			foreach ( $constants as $name => $value ) {
+				$constants_checksums[ $name ] = $this->get_check_sum( $value );
+			}
+			update_option( self::CONSTANTS_CHECKSUM_OPTION_NAME, $constants_checksums );
+			return $constants;
+		}
+		return $args;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-full-sync.php b/plugins/jetpack/sync/class.jetpack-sync-module-full-sync.php
new file mode 100644
index 00000000..4ad60896
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-full-sync.php
@@ -0,0 +1,477 @@
+<?php
+
+/**
+ * This class does a full resync of the database by
+ * enqueuing an outbound action for every single object
+ * that we care about.
+ *
+ * This class, and its related class Jetpack_Sync_Module, contain a few non-obvious optimisations that should be explained:
+ * - we fire an action called jetpack_full_sync_start so that WPCOM can erase the contents of the cached database
+ * - for each object type, we page through the object IDs and enqueue them by firing some monitored actions
+ * - we load the full objects for those IDs in chunks of Jetpack_Sync_Module::ARRAY_CHUNK_SIZE (to reduce the number of MySQL calls)
+ * - we fire a trigger for the entire array which the Jetpack_Sync_Listener then serializes and queues.
+ */
+
+class Jetpack_Sync_Module_Full_Sync extends Jetpack_Sync_Module {
+	const STATUS_OPTION_PREFIX = 'jetpack_sync_full_';
+	const FULL_SYNC_TIMEOUT    = 3600;
+
+	public function name() {
+		return 'full-sync';
+	}
+
+	function init_full_sync_listeners( $callable ) {
+		// synthetic actions for full sync
+		add_action( 'jetpack_full_sync_start', $callable, 10, 2 );
+		add_action( 'jetpack_full_sync_end', $callable, 10, 2 );
+		add_action( 'jetpack_full_sync_cancelled', $callable );
+	}
+
+	function init_before_send() {
+		// this is triggered after actions have been processed on the server
+		add_action( 'jetpack_sync_processed_actions', array( $this, 'update_sent_progress_action' ) );
+	}
+
+	function start( $module_configs = null ) {
+		$was_already_running = $this->is_started() && ! $this->is_finished();
+
+		// remove all evidence of previous full sync items and status
+		$this->reset_data();
+
+		if ( $was_already_running ) {
+			/**
+			 * Fires when a full sync is cancelled.
+			 *
+			 * @since 4.2.0
+			 */
+			do_action( 'jetpack_full_sync_cancelled' );
+		}
+
+		$this->update_status_option( 'started', time() );
+		$this->update_status_option( 'params', $module_configs );
+
+		$enqueue_status   = array();
+		$full_sync_config = array();
+
+		// default value is full sync
+		if ( ! is_array( $module_configs ) ) {
+			$module_configs = array();
+			foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+				$module_configs[ $module->name() ] = true;
+			}
+		}
+
+		// set default configuration, calculate totals, and save configuration if totals > 0
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$module_name   = $module->name();
+			$module_config = isset( $module_configs[ $module_name ] ) ? $module_configs[ $module_name ] : false;
+
+			if ( ! $module_config ) {
+				continue;
+			}
+
+			if ( 'users' === $module_name && 'initial' === $module_config ) {
+				$module_config = $module->get_initial_sync_user_config();
+			}
+
+			$enqueue_status[ $module_name ] = false;
+
+			$total_items = $module->estimate_full_sync_actions( $module_config );
+
+			// if there's information to process, configure this module
+			if ( ! is_null( $total_items ) && $total_items > 0 ) {
+				$full_sync_config[ $module_name ] = $module_config;
+				$enqueue_status[ $module_name ]   = array(
+					$total_items,   // total
+					0,              // queued
+					false,          // current state
+				);
+			}
+		}
+
+		$this->set_config( $full_sync_config );
+		$this->set_enqueue_status( $enqueue_status );
+
+		$range = $this->get_content_range( $full_sync_config );
+		/**
+		 * Fires when a full sync begins. This action is serialized
+		 * and sent to the server so that it knows a full sync is coming.
+		 *
+		 * @since 4.2.0
+		 * @since 7.3.0 Added $range arg.
+		 *
+		 * @param $full_sync_config - array
+		 * @param $range array
+		 */
+		do_action( 'jetpack_full_sync_start', $full_sync_config, $range );
+
+		$this->continue_enqueuing( $full_sync_config, $enqueue_status );
+
+		return true;
+	}
+
+	function continue_enqueuing( $configs = null, $enqueue_status = null ) {
+		if ( ! $this->is_started() || $this->get_status_option( 'queue_finished' ) ) {
+			return;
+		}
+
+		// if full sync queue is full, don't enqueue more items
+		$max_queue_size_full_sync = Jetpack_Sync_Settings::get_setting( 'max_queue_size_full_sync' );
+		$full_sync_queue          = new Jetpack_Sync_Queue( 'full_sync' );
+
+		$available_queue_slots = $max_queue_size_full_sync - $full_sync_queue->size();
+
+		if ( $available_queue_slots <= 0 ) {
+			return;
+		} else {
+			$remaining_items_to_enqueue = min( Jetpack_Sync_Settings::get_setting( 'max_enqueue_full_sync' ), $available_queue_slots );
+		}
+
+		if ( ! $configs ) {
+			$configs = $this->get_config();
+		}
+
+		if ( ! $enqueue_status ) {
+			$enqueue_status = $this->get_enqueue_status();
+		}
+
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$module_name = $module->name();
+
+			// skip module if not configured for this sync or module is done
+			if ( ! isset( $configs[ $module_name ] )
+				|| // no module config
+					! $configs[ $module_name ]
+				|| // no enqueue status
+					! $enqueue_status[ $module_name ]
+				|| // finished enqueuing this module
+					true === $enqueue_status[ $module_name ][2] ) {
+				continue;
+			}
+
+			list( $items_enqueued, $next_enqueue_state ) = $module->enqueue_full_sync_actions( $configs[ $module_name ], $remaining_items_to_enqueue, $enqueue_status[ $module_name ][2] );
+
+			$enqueue_status[ $module_name ][2] = $next_enqueue_state;
+
+			// if items were processed, subtract them from the limit
+			if ( ! is_null( $items_enqueued ) && $items_enqueued > 0 ) {
+				$enqueue_status[ $module_name ][1] += $items_enqueued;
+				$remaining_items_to_enqueue        -= $items_enqueued;
+			}
+
+			// stop processing if we've reached our limit of items to enqueue
+			if ( 0 >= $remaining_items_to_enqueue ) {
+				$this->set_enqueue_status( $enqueue_status );
+				return;
+			}
+		}
+
+		$this->set_enqueue_status( $enqueue_status );
+
+		// setting autoload to true means that it's faster to check whether we should continue enqueuing
+		$this->update_status_option( 'queue_finished', time(), true );
+
+		$range = $this->get_content_range( $configs );
+
+		/**
+		 * Fires when a full sync ends. This action is serialized
+		 * and sent to the server.
+		 *
+		 * @since 4.2.0
+		 * @since 7.3.0 Added $range arg.
+		 *
+		 * @param args ''
+		 * @param $range array 
+		 */
+		do_action( 'jetpack_full_sync_end', '', $range );
+	}
+
+	function get_range( $type ) {
+		global $wpdb;
+		if ( ! in_array( $type, array( 'comments', 'posts' ) ) ) {
+			return array();
+		}
+
+		switch ( $type ) {
+			case 'posts':
+				$table     = $wpdb->posts;
+				$id        = 'ID';
+				$where_sql = Jetpack_Sync_Settings::get_blacklisted_post_types_sql();
+
+				break;
+			case 'comments':
+				$table     = $wpdb->comments;
+				$id        = 'comment_ID';
+				$where_sql = Jetpack_Sync_Settings::get_comments_filter_sql();
+				break;
+		}
+		$results = $wpdb->get_results( "SELECT MAX({$id}) as max, MIN({$id}) as min, COUNT({$id}) as count FROM {$table} WHERE {$where_sql}" );
+		if ( isset( $results[0] ) ) {
+			return $results[0];
+		}
+
+		return array();
+	}
+
+	private function get_content_range( $config ) {
+		$range = array();
+		// Only when we are sending the whole range do we want to send also the range
+		if ( isset( $config['posts'] ) && $config['posts'] === true ) {
+			$range['posts'] = $this->get_range( 'posts' );
+		}
+
+		if ( isset( $config['comments'] ) && $config['comments'] === true ) {
+			$range['comments'] = $this->get_range( 'comments' );
+		}
+		return $range;
+	}
+
+	function update_sent_progress_action( $actions ) {
+		// quick way to map to first items with an array of arrays
+		$actions_with_counts = array_count_values( array_filter( array_map( array( $this, 'get_action_name' ), $actions ) ) );
+
+		// Total item counts for each action.
+		$actions_with_total_counts = $this->get_actions_totals( $actions );
+
+		if ( ! $this->is_started() || $this->is_finished() ) {
+			return;
+		}
+
+		if ( isset( $actions_with_counts['jetpack_full_sync_start'] ) ) {
+			$this->update_status_option( 'send_started', time() );
+		}
+
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$module_actions     = $module->get_full_sync_actions();
+			$status_option_name = "{$module->name()}_sent";
+			$total_option_name  = "{$status_option_name}_total";
+			$items_sent         = $this->get_status_option( $status_option_name, 0 );
+			$items_sent_total   = $this->get_status_option( $total_option_name, 0 );
+
+			foreach ( $module_actions as $module_action ) {
+				if ( isset( $actions_with_counts[ $module_action ] ) ) {
+					$items_sent += $actions_with_counts[ $module_action ];
+				}
+
+				if ( ! empty( $actions_with_total_counts[ $module_action ] ) ) {
+					$items_sent_total += $actions_with_total_counts[ $module_action ];
+				}
+			}
+
+			if ( $items_sent > 0 ) {
+				$this->update_status_option( $status_option_name, $items_sent );
+			}
+
+			if ( 0 !== $items_sent_total ) {
+				$this->update_status_option( $total_option_name, $items_sent_total );
+			}
+		}
+
+		if ( isset( $actions_with_counts['jetpack_full_sync_end'] ) ) {
+			$this->update_status_option( 'finished', time() );
+		}
+	}
+
+	public function get_action_name( $queue_item ) {
+		if ( is_array( $queue_item ) && isset( $queue_item[0] ) ) {
+			return $queue_item[0];
+		}
+		return false;
+	}
+
+	/**
+	 * Retrieve the total number of items we're syncing in a particular queue item (action).
+	 * `$queue_item[1]` is expected to contain chunks of items, and `$queue_item[1][0]`
+	 * represents the first (and only) chunk of items to sync in that action.
+	 *
+	 * @param array $queue_item Item of the sync queue that corresponds to a particular action.
+	 * @return int Total number of items in the action.
+	 */
+	public function get_action_totals( $queue_item ) {
+		if ( is_array( $queue_item ) && isset( $queue_item[1][0] ) ) {
+			if ( is_array( $queue_item[1][0] ) ) {
+				// Let's count the items we sync in this action.
+				return count( $queue_item[1][0] );
+			}
+			// -1 indicates that this action syncs all items by design.
+			return -1;
+		}
+		return 0;
+	}
+
+	/**
+	 * Retrieve the total number of items for a set of actions, grouped by action name.
+	 *
+	 * @param array $actions An array of actions.
+	 * @return array An array, representing the total number of items, grouped per action.
+	 */
+	public function get_actions_totals( $actions ) {
+		$totals = array();
+
+		foreach ( $actions as $action ) {
+			$name          = $this->get_action_name( $action );
+			$action_totals = $this->get_action_totals( $action );
+			if ( ! isset( $totals[ $name ] ) ) {
+				$totals[ $name ] = 0;
+			}
+			$totals[ $name ] += $action_totals;
+		}
+
+		return $totals;
+	}
+
+	public function is_started() {
+		return ! ! $this->get_status_option( 'started' );
+	}
+
+	public function is_finished() {
+		return ! ! $this->get_status_option( 'finished' );
+	}
+
+	public function get_status() {
+		$status = array(
+			'started'        => $this->get_status_option( 'started' ),
+			'queue_finished' => $this->get_status_option( 'queue_finished' ),
+			'send_started'   => $this->get_status_option( 'send_started' ),
+			'finished'       => $this->get_status_option( 'finished' ),
+			'sent'           => array(),
+			'sent_total'     => array(),
+			'queue'          => array(),
+			'config'         => $this->get_status_option( 'params' ),
+			'total'          => array(),
+		);
+
+		$enqueue_status = $this->get_enqueue_status();
+
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$name = $module->name();
+
+			if ( ! isset( $enqueue_status[ $name ] ) ) {
+				continue;
+			}
+
+			list( $total, $queued, $state ) = $enqueue_status[ $name ];
+
+			if ( $total ) {
+				$status['total'][ $name ] = $total;
+			}
+
+			if ( $queued ) {
+				$status['queue'][ $name ] = $queued;
+			}
+
+			if ( $sent = $this->get_status_option( "{$name}_sent" ) ) {
+				$status['sent'][ $name ] = $sent;
+			}
+
+			$sent_total = $this->get_status_option( "{$name}_sent_total" );
+			if ( $sent_total ) {
+				$status['sent_total'][ $name ] = $sent_total;
+			}
+		}
+
+		return $status;
+	}
+
+	public function clear_status() {
+		$prefix = self::STATUS_OPTION_PREFIX;
+		Jetpack_Options::delete_raw_option( "{$prefix}_started" );
+		Jetpack_Options::delete_raw_option( "{$prefix}_params" );
+		Jetpack_Options::delete_raw_option( "{$prefix}_queue_finished" );
+		Jetpack_Options::delete_raw_option( "{$prefix}_send_started" );
+		Jetpack_Options::delete_raw_option( "{$prefix}_finished" );
+
+		$this->delete_enqueue_status();
+
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			Jetpack_Options::delete_raw_option( "{$prefix}_{$module->name()}_sent" );
+			Jetpack_Options::delete_raw_option( "{$prefix}_{$module->name()}_sent_total" );
+		}
+	}
+
+	public function reset_data() {
+		$this->clear_status();
+		$this->delete_config();
+		require_once dirname( __FILE__ ) . '/class.jetpack-sync-listener.php';
+		$listener = Jetpack_Sync_Listener::get_instance();
+		$listener->get_full_sync_queue()->reset();
+	}
+
+	private function get_status_option( $name, $default = null ) {
+		$value = Jetpack_Options::get_raw_option( self::STATUS_OPTION_PREFIX . "_$name", $default );
+
+		return is_numeric( $value ) ? intval( $value ) : $value;
+	}
+
+	private function update_status_option( $name, $value, $autoload = false ) {
+		Jetpack_Options::update_raw_option( self::STATUS_OPTION_PREFIX . "_$name", $value, $autoload );
+	}
+
+	private function set_enqueue_status( $new_status ) {
+		Jetpack_Options::update_raw_option( 'jetpack_sync_full_enqueue_status', $new_status );
+	}
+
+	private function delete_enqueue_status() {
+		return Jetpack_Options::delete_raw_option( 'jetpack_sync_full_enqueue_status' );
+	}
+
+	private function get_enqueue_status() {
+		return Jetpack_Options::get_raw_option( 'jetpack_sync_full_enqueue_status' );
+	}
+
+	private function set_config( $config ) {
+		Jetpack_Options::update_raw_option( 'jetpack_sync_full_config', $config );
+	}
+
+	private function delete_config() {
+		return Jetpack_Options::delete_raw_option( 'jetpack_sync_full_config' );
+	}
+
+	private function get_config() {
+		return Jetpack_Options::get_raw_option( 'jetpack_sync_full_config' );
+	}
+
+	private function write_option( $name, $value ) {
+		// we write our own option updating code to bypass filters/caching/etc on set_option/get_option
+		global $wpdb;
+		$serialized_value = maybe_serialize( $value );
+		// try updating, if no update then insert
+		// TODO: try to deal with the fact that unchanged values can return updated_num = 0
+		// below we used "insert ignore" to at least suppress the resulting error
+		$updated_num = $wpdb->query(
+			$wpdb->prepare(
+				"UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s",
+				$serialized_value,
+				$name
+			)
+		);
+
+		if ( ! $updated_num ) {
+			$updated_num = $wpdb->query(
+				$wpdb->prepare(
+					"INSERT IGNORE INTO $wpdb->options ( option_name, option_value, autoload ) VALUES ( %s, %s, 'no' )",
+					$name,
+					$serialized_value
+				)
+			);
+		}
+		return $updated_num;
+	}
+
+	private function read_option( $name, $default = null ) {
+		global $wpdb;
+		$value = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT option_value FROM $wpdb->options WHERE option_name = %s LIMIT 1",
+				$name
+			)
+		);
+		$value = maybe_unserialize( $value );
+
+		if ( $value === null && $default !== null ) {
+			return $default;
+		}
+
+		return $value;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-import.php b/plugins/jetpack/sync/class.jetpack-sync-module-import.php
new file mode 100644
index 00000000..4b5dd83d
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-import.php
@@ -0,0 +1,170 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+
+class Jetpack_Sync_Module_Import extends Jetpack_Sync_Module {
+
+	/**
+	 * Tracks which actions have already been synced for the import
+	 * to prevent the same event from being triggered a second time
+	 *
+	 * @var array
+	 */
+	private $synced_actions = array();
+
+	/**
+	 * A mapping of action types to sync action name.
+	 * Keys are the name of the import action.
+	 * Values are the resulting sync action.
+	 *
+	 * Note: import_done and import_end both intentionally map to
+	 * jetpack_sync_import_end, as they both track the same type of action,
+	 * the successful completion of an import. Different import plugins use
+	 * differently named actions, and this is an attempt to consolidate.
+	 *
+	 * @var array
+	 */
+	private static $import_sync_action_map = array(
+		'import_start' => 'jetpack_sync_import_start',
+		'import_done'  => 'jetpack_sync_import_end',
+		'import_end'   => 'jetpack_sync_import_end',
+	);
+
+	public function name() {
+		return 'import';
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'export_wp', $callable );
+		add_action( 'jetpack_sync_import_start', $callable, 10, 2 );
+		add_action( 'jetpack_sync_import_end', $callable, 10, 2 );
+
+		// WordPress.
+		add_action( 'import_start', array( $this, 'sync_import_action' ) );
+
+		// Movable type, RSS, Livejournal.
+		add_action( 'import_done', array( $this, 'sync_import_action' ) );
+
+		// WordPress, Blogger, Livejournal, woo tax rate.
+		add_action( 'import_end', array( $this, 'sync_import_action' ) );
+	}
+
+	public function set_defaults() {
+		$this->synced_actions = array();
+	}
+
+	public function sync_import_action( $importer ) {
+		$import_action = current_filter();
+		// Map action to event name.
+		$sync_action = self::$import_sync_action_map[ $import_action ];
+
+		// Only sync each action once per import.
+		if ( array_key_exists( $sync_action, $this->synced_actions ) && $this->synced_actions[ $sync_action ] ) {
+			return;
+		}
+
+		// Mark this action as synced.
+		$this->synced_actions[ $sync_action ] = true;
+
+		// Prefer self-reported $importer value.
+		if ( ! $importer ) {
+			// Fall back to inferring by calling class name.
+			$importer = self::get_calling_importer_class();
+		}
+
+		// Get $importer from known_importers.
+		$known_importers = Jetpack_Sync_Settings::get_setting( 'known_importers' );
+		if ( isset( $known_importers[ $importer ] ) ) {
+			$importer = $known_importers[ $importer ];
+		}
+
+		$importer_name = $this->get_importer_name( $importer );
+
+		switch ( $sync_action ) {
+			case 'jetpack_sync_import_start':
+				/**
+				 * Used for syncing the start of an import
+				 *
+				 * @since 7.3.0
+				 *
+				 * @module sync
+				 *
+				 * @param string $importer      Either a string reported by the importer, the class name of the importer, or 'unknown'.
+				 * @param string $importer_name The name reported by the importer, or 'Unknown Importer'.
+				 */
+				do_action( 'jetpack_sync_import_start', $importer, $importer_name );
+				break;
+
+			case 'jetpack_sync_import_end':
+				/**
+				 * Used for syncing the end of an import
+				 *
+				 * @since 7.3.0
+				 *
+				 * @module sync
+				 *
+				 * @param string $importer      Either a string reported by the importer, the class name of the importer, or 'unknown'.
+				 * @param string $importer_name The name reported by the importer, or 'Unknown Importer'.
+				 */
+				do_action( 'jetpack_sync_import_end', $importer, $importer_name );
+				break;
+		}
+	}
+
+	private function get_importer_name( $importer ) {
+		$importers = get_importers();
+		return isset( $importers[ $importer ] ) ? $importers[ $importer ][0] : 'Unknown Importer';
+	}
+
+	/**
+	 * Determine the class that extends `WP_Importer` which is responsible for
+	 * the current action. Designed to be used within an action handler.
+	 *
+	 * @return string  The name of the calling class, or 'unknown'.
+	 */
+	private static function get_calling_importer_class() {
+		// If WP_Importer doesn't exist, neither will any importer that extends it.
+		if ( ! class_exists( 'WP_Importer', false ) ) {
+			return 'unknown';
+		}
+
+		$action    = current_filter();
+		$backtrace = debug_backtrace( false ); //phpcs:ignore PHPCompatibility.FunctionUse.NewFunctionParameters.debug_backtrace_optionsFound,WordPress.PHP.DevelopmentFunctions.error_log_debug_backtrace
+
+		$do_action_pos = -1;
+		$backtrace_len = count( $backtrace );
+		for ( $i = 0; $i < $backtrace_len; $i++ ) {
+			// Find the location in the stack of the calling action.
+			if ( 'do_action' === $backtrace[ $i ]['function'] && $action === $backtrace[ $i ]['args'][0] ) {
+				$do_action_pos = $i;
+				break;
+			}
+		}
+
+		// If the action wasn't called, the calling class is unknown.
+		if ( -1 === $do_action_pos ) {
+			return 'unknown';
+		}
+
+		// Continue iterating the stack looking for a caller that extends WP_Importer.
+		for ( $i = $do_action_pos + 1; $i < $backtrace_len; $i++ ) {
+			// If there is no class on the trace, continue.
+			if ( ! isset( $backtrace[ $i ]['class'] ) ) {
+				continue;
+			}
+
+			$class_name = $backtrace[ $i ]['class'];
+
+			// Check if the class extends WP_Importer.
+			if ( class_exists( $class_name, false ) ) {
+				$parents = class_parents( $class_name, false );
+				if ( $parents && in_array( 'WP_Importer', $parents, true ) ) {
+					return $class_name;
+				}
+			}
+		}
+
+		// If we've exhausted the stack without a match, the calling class is unknown.
+		return 'unknown';
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-menus.php b/plugins/jetpack/sync/class.jetpack-sync-module-menus.php
new file mode 100644
index 00000000..86e2279c
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-menus.php
@@ -0,0 +1,78 @@
+<?php
+
+class Jetpack_Sync_Module_Menus extends Jetpack_Sync_Module {
+	private $nav_items_just_added = array();
+
+	function name() {
+		return 'menus';
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'wp_create_nav_menu', $callable, 10, 2 );
+		add_action( 'wp_update_nav_menu', array( $this, 'update_nav_menu' ), 10, 2 );
+		add_action( 'wp_add_nav_menu_item', array( $this, 'update_nav_menu_add_item' ), 10, 3 );
+		add_action( 'wp_update_nav_menu_item', array( $this, 'update_nav_menu_update_item' ), 10, 3 );
+		add_action( 'post_updated', array( $this, 'remove_just_added_menu_item' ), 10, 2 );
+
+		add_action( 'jetpack_sync_updated_nav_menu', $callable, 10, 2 );
+		add_action( 'jetpack_sync_updated_nav_menu_add_item', $callable, 10, 4 );
+		add_action( 'jetpack_sync_updated_nav_menu_update_item', $callable, 10, 4 );
+		add_action( 'delete_nav_menu', $callable, 10, 3 );
+	}
+
+	public function update_nav_menu( $menu_id, $menu_data = array() ) {
+		if ( empty( $menu_data ) ) {
+			return;
+		}
+		/**
+		 * Helps sync log that a nav menu was updated.
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param int $menu_id, the id of the menu
+		 * @param object $menu_data
+		 */
+		do_action( 'jetpack_sync_updated_nav_menu', $menu_id, $menu_data );
+	}
+
+	public function update_nav_menu_add_item( $menu_id, $nav_item_id, $nav_item_args ) {
+		$menu_data                    = wp_get_nav_menu_object( $menu_id );
+		$this->nav_items_just_added[] = $nav_item_id;
+		/**
+		 * Helps sync log that a new menu item was added.
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param int $menu_id, the id of the menu
+		 * @param object $menu_data
+		 * @param int $nav_item_id
+		 * @param int $nav_item_args
+		 */
+		do_action( 'jetpack_sync_updated_nav_menu_add_item', $menu_id, $menu_data, $nav_item_id, $nav_item_args );
+	}
+
+	public function update_nav_menu_update_item( $menu_id, $nav_item_id, $nav_item_args ) {
+		if ( in_array( $nav_item_id, $this->nav_items_just_added ) ) {
+			return;
+		}
+		$menu_data = wp_get_nav_menu_object( $menu_id );
+		/**
+		 * Helps sync log that an update to the menu item happened.
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param int $menu_id, the id of the menu
+		 * @param object $menu_data
+		 * @param int $nav_item_id
+		 * @param int $nav_item_args
+		 */
+		do_action( 'jetpack_sync_updated_nav_menu_update_item', $menu_id, $menu_data, $nav_item_id, $nav_item_args );
+	}
+
+	public function remove_just_added_menu_item( $nav_item_id, $post_after ) {
+		if ( 'nav_menu_item' !== $post_after->post_type ) {
+			return;
+		}
+		$this->nav_items_just_added = array_diff( $this->nav_items_just_added, array( $nav_item_id ) );
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-meta.php b/plugins/jetpack/sync/class.jetpack-sync-module-meta.php
new file mode 100644
index 00000000..e3d43544
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-meta.php
@@ -0,0 +1,62 @@
+<?php
+
+class Jetpack_Sync_Module_Meta extends Jetpack_Sync_Module {
+
+	public function name() {
+		return 'meta';
+	}
+
+	/**
+	 * This implementation of get_objects_by_id() is a bit hacky since we're not passing in an array of meta IDs,
+	 * but instead an array of post or comment IDs for which to retrieve meta for. On top of that,
+	 * we also pass in an associative array where we expect there to be 'meta_key' and 'ids' keys present.
+	 *
+	 * This seemed to be required since if we have missing meta on WP.com and need to fetch it, we don't know what
+	 * the meta key is, but we do know that we have missing meta for a given post or comment.
+	 *
+	 * @param string $object_type The type of object for which we retrieve meta. Either 'post' or 'comment'
+	 * @param array  $config Must include 'meta_key' and 'ids' keys
+	 *
+	 * @return array
+	 */
+	public function get_objects_by_id( $object_type, $config ) {
+		global $wpdb;
+
+		$table = _get_meta_table( $object_type );
+
+		if ( ! $table ) {
+			return array();
+		}
+
+		if ( ! isset( $config['meta_key'] ) || ! isset( $config['ids'] ) || ! is_array( $config['ids'] ) ) {
+			return array();
+		}
+
+		$meta_key         = $config['meta_key'];
+		$ids              = $config['ids'];
+		$object_id_column = $object_type . '_id';
+
+		// Sanitize so that the array only has integer values
+		$ids_string = implode( ', ', array_map( 'intval', $ids ) );
+		$metas      = $wpdb->get_results(
+			$wpdb->prepare(
+				"SELECT * FROM {$table} WHERE {$object_id_column} IN ( {$ids_string} ) AND meta_key = %s",
+				$meta_key
+			)
+		);
+
+		$meta_objects = array();
+		foreach ( (array) $metas as $meta_object ) {
+			$meta_object                                       = (array) $meta_object;
+			$meta_objects[ $meta_object[ $object_id_column ] ] = array(
+				'meta_type'  => $object_type,
+				'meta_id'    => $meta_object['meta_id'],
+				'meta_key'   => $meta_key,
+				'meta_value' => $meta_object['meta_value'],
+				'object_id'  => $meta_object[ $object_id_column ],
+			);
+		}
+
+		return $meta_objects;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-network-options.php b/plugins/jetpack/sync/class.jetpack-sync-module-network-options.php
new file mode 100644
index 00000000..011e9bba
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-network-options.php
@@ -0,0 +1,116 @@
+<?php
+
+class Jetpack_Sync_Module_Network_Options extends Jetpack_Sync_Module {
+	private $network_options_whitelist;
+
+	public function name() {
+		return 'network_options';
+	}
+
+	public function init_listeners( $callable ) {
+		if ( ! is_multisite() ) {
+			return;
+		}
+
+		// multi site network options
+		add_action( 'add_site_option', $callable, 10, 2 );
+		add_action( 'update_site_option', $callable, 10, 3 );
+		add_action( 'delete_site_option', $callable, 10, 1 );
+
+		$whitelist_network_option_handler = array( $this, 'whitelist_network_options' );
+		add_filter( 'jetpack_sync_before_enqueue_delete_site_option', $whitelist_network_option_handler );
+		add_filter( 'jetpack_sync_before_enqueue_add_site_option', $whitelist_network_option_handler );
+		add_filter( 'jetpack_sync_before_enqueue_update_site_option', $whitelist_network_option_handler );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_network_options', $callable );
+	}
+
+	public function init_before_send() {
+		if ( ! is_multisite() ) {
+			return;
+		}
+
+		// full sync
+		add_filter(
+			'jetpack_sync_before_send_jetpack_full_sync_network_options',
+			array(
+				$this,
+				'expand_network_options',
+			)
+		);
+	}
+
+	public function set_defaults() {
+		$this->network_options_whitelist = Jetpack_Sync_Defaults::$default_network_options_whitelist;
+	}
+
+	function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		if ( ! is_multisite() ) {
+			return array( 0, true );
+		}
+
+		/**
+		 * Tells the client to sync all options to the server
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean Whether to expand options (should always be true)
+		 */
+		do_action( 'jetpack_full_sync_network_options', true );
+
+		// The number of actions enqueued, and next module state (true == done)
+		return array( 1, true );
+	}
+
+	function estimate_full_sync_actions( $config ) {
+		if ( ! is_multisite() ) {
+			return 0;
+		}
+
+		return 1;
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_network_options' );
+	}
+
+	function get_all_network_options() {
+		$options = array();
+		foreach ( $this->network_options_whitelist as $option ) {
+			$options[ $option ] = get_site_option( $option );
+		}
+
+		return $options;
+	}
+
+	function set_network_options_whitelist( $options ) {
+		$this->network_options_whitelist = $options;
+	}
+
+	function get_network_options_whitelist() {
+		return $this->network_options_whitelist;
+	}
+
+	// reject non-whitelisted network options
+	function whitelist_network_options( $args ) {
+		if ( ! $this->is_whitelisted_network_option( $args[0] ) ) {
+			return false;
+		}
+
+		return $args;
+	}
+
+	function is_whitelisted_network_option( $option ) {
+		return is_multisite() && in_array( $option, $this->network_options_whitelist );
+	}
+
+	public function expand_network_options( $args ) {
+		if ( $args[0] ) {
+			return $this->get_all_network_options();
+		}
+
+		return $args;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-options.php b/plugins/jetpack/sync/class.jetpack-sync-module-options.php
new file mode 100644
index 00000000..287e73b9
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-options.php
@@ -0,0 +1,173 @@
+<?php
+
+class Jetpack_Sync_Module_Options extends Jetpack_Sync_Module {
+	private $options_whitelist, $options_contentless;
+
+	public function name() {
+		return 'options';
+	}
+
+	public function init_listeners( $callable ) {
+		// options
+		add_action( 'added_option', $callable, 10, 2 );
+		add_action( 'updated_option', $callable, 10, 3 );
+		add_action( 'deleted_option', $callable, 10, 1 );
+
+		// Sync Core Icon: Detect changes in Core's Site Icon and make it syncable.
+		add_action( 'add_option_site_icon', array( $this, 'jetpack_sync_core_icon' ) );
+		add_action( 'update_option_site_icon', array( $this, 'jetpack_sync_core_icon' ) );
+		add_action( 'delete_option_site_icon', array( $this, 'jetpack_sync_core_icon' ) );
+
+		$whitelist_option_handler = array( $this, 'whitelist_options' );
+		add_filter( 'jetpack_sync_before_enqueue_deleted_option', $whitelist_option_handler );
+		add_filter( 'jetpack_sync_before_enqueue_added_option', $whitelist_option_handler );
+		add_filter( 'jetpack_sync_before_enqueue_updated_option', $whitelist_option_handler );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_options', $callable );
+	}
+
+	public function init_before_send() {
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_options', array( $this, 'expand_options' ) );
+	}
+
+	public function set_defaults() {
+		$this->update_options_whitelist();
+		$this->update_options_contentless();
+	}
+
+	public function set_late_default() {
+
+		/** This filter is already documented in json-endpoints/jetpack/class.wpcom-json-api-get-option-endpoint.php */
+		$late_options = apply_filters( 'jetpack_options_whitelist', array() );
+		if ( ! empty( $late_options ) && is_array( $late_options ) ) {
+			$this->options_whitelist = array_merge( $this->options_whitelist, $late_options );
+		}
+	}
+
+	function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		/**
+		 * Tells the client to sync all options to the server
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean Whether to expand options (should always be true)
+		 */
+		do_action( 'jetpack_full_sync_options', true );
+
+		// The number of actions enqueued, and next module state (true == done)
+		return array( 1, true );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		return 1;
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_options' );
+	}
+
+	// Is public so that we don't have to store so much data all the options twice.
+	function get_all_options() {
+		$options       = array();
+		$random_string = wp_generate_password();
+		foreach ( $this->options_whitelist as $option ) {
+			$option_value = get_option( $option, $random_string );
+			if ( $option_value !== $random_string ) {
+				$options[ $option ] = $option_value;
+			}
+		}
+
+		// add theme mods
+		$theme_mods_option = 'theme_mods_' . get_option( 'stylesheet' );
+		$theme_mods_value  = get_option( $theme_mods_option, $random_string );
+		if ( $theme_mods_value === $random_string ) {
+			return $options;
+		}
+		$this->filter_theme_mods( $theme_mods_value );
+		$options[ $theme_mods_option ] = $theme_mods_value;
+		return $options;
+	}
+
+	function update_options_whitelist() {
+		$this->options_whitelist = Jetpack_Sync_Defaults::get_options_whitelist();
+	}
+
+	function set_options_whitelist( $options ) {
+		$this->options_whitelist = $options;
+	}
+
+	function get_options_whitelist() {
+		return $this->options_whitelist;
+	}
+
+	function update_options_contentless() {
+		$this->options_contentless = Jetpack_Sync_Defaults::get_options_contentless();
+	}
+
+	function get_options_contentless() {
+		return $this->options_contentless;
+	}
+
+	function whitelist_options( $args ) {
+		// Reject non-whitelisted options
+		if ( ! $this->is_whitelisted_option( $args[0] ) ) {
+			return false;
+		}
+
+		// filter our weird array( false ) value for theme_mods_*
+		if ( 'theme_mods_' === substr( $args[0], 0, 11 ) ) {
+			$this->filter_theme_mods( $args[1] );
+			if ( isset( $args[2] ) ) {
+				$this->filter_theme_mods( $args[2] );
+			}
+		}
+
+		// Set value(s) of contentless option to empty string(s)
+		if ( $this->is_contentless_option( $args[0] ) ) {
+			// Create a new array matching length of $args, containing empty strings
+			$empty    = array_fill( 0, count( $args ), '' );
+			$empty[0] = $args[0];
+			return $empty;
+		}
+
+		return $args;
+	}
+
+	function is_whitelisted_option( $option ) {
+		return in_array( $option, $this->options_whitelist ) || 'theme_mods_' === substr( $option, 0, 11 );
+	}
+
+	private function is_contentless_option( $option ) {
+		return in_array( $option, $this->options_contentless );
+	}
+
+	private function filter_theme_mods( &$value ) {
+		if ( is_array( $value ) && isset( $value[0] ) ) {
+			unset( $value[0] );
+		}
+	}
+
+	function jetpack_sync_core_icon() {
+		$url = get_site_icon_url();
+
+		require_once JETPACK__PLUGIN_DIR . 'modules/site-icon/site-icon-functions.php';
+		// If there's a core icon, maybe update the option.  If not, fall back to Jetpack's.
+		if ( ! empty( $url ) && $url !== jetpack_site_icon_url() ) {
+			// This is the option that is synced with dotcom
+			Jetpack_Options::update_option( 'site_icon_url', $url );
+		} elseif ( empty( $url ) ) {
+			Jetpack_Options::delete_option( 'site_icon_url' );
+		}
+	}
+
+	public function expand_options( $args ) {
+		if ( $args[0] ) {
+			return $this->get_all_options();
+		}
+
+		return $args;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-plugins.php b/plugins/jetpack/sync/class.jetpack-sync-module-plugins.php
new file mode 100644
index 00000000..876526ab
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-plugins.php
@@ -0,0 +1,289 @@
+<?php
+
+class Jetpack_Sync_Module_Plugins extends Jetpack_Sync_Module {
+
+	private $action_handler;
+	private $plugin_info = array();
+	private $plugins     = array();
+
+	public function name() {
+		return 'plugins';
+	}
+
+	public function init_listeners( $callable ) {
+		$this->action_handler = $callable;
+
+		add_action( 'deleted_plugin', array( $this, 'deleted_plugin' ), 10, 2 );
+		add_action( 'activated_plugin', $callable, 10, 2 );
+		add_action( 'deactivated_plugin', $callable, 10, 2 );
+		add_action( 'delete_plugin', array( $this, 'delete_plugin' ) );
+		add_filter( 'upgrader_pre_install', array( $this, 'populate_plugins' ), 10, 1 );
+		add_action( 'upgrader_process_complete', array( $this, 'on_upgrader_completion' ), 10, 2 );
+		add_action( 'jetpack_plugin_installed', $callable, 10, 1 );
+		add_action( 'jetpack_plugin_update_failed', $callable, 10, 4 );
+		add_action( 'jetpack_plugins_updated', $callable, 10, 2 );
+		add_action( 'admin_action_update', array( $this, 'check_plugin_edit' ) );
+		add_action( 'jetpack_edited_plugin', $callable, 10, 2 );
+		add_action( 'wp_ajax_edit-theme-plugin-file', array( $this, 'plugin_edit_ajax' ), 0 );
+	}
+
+	public function init_before_send() {
+		add_filter( 'jetpack_sync_before_send_activated_plugin', array( $this, 'expand_plugin_data' ) );
+		add_filter( 'jetpack_sync_before_send_deactivated_plugin', array( $this, 'expand_plugin_data' ) );
+		// Note that we don't simply 'expand_plugin_data' on the 'delete_plugin' action here because the plugin file is deleted when that action finishes
+	}
+	public function populate_plugins( $response ) {
+		$this->plugins = get_plugins();
+		return $response;
+	}
+	public function on_upgrader_completion( $upgrader, $details ) {
+		if ( ! isset( $details['type'] ) ) {
+			return;
+		}
+		if ( 'plugin' != $details['type'] ) {
+			return;
+		}
+
+		if ( ! isset( $details['action'] ) ) {
+			return;
+		}
+
+		$plugins = ( isset( $details['plugins'] ) ? $details['plugins'] : null );
+		if ( empty( $plugins ) ) {
+			$plugins = ( isset( $details['plugin'] ) ? array( $details['plugin'] ) : null );
+		}
+
+		// for plugin installer
+		if ( empty( $plugins ) && method_exists( $upgrader, 'plugin_info' ) ) {
+			$plugins = array( $upgrader->plugin_info() );
+		}
+
+		if ( empty( $plugins ) ) {
+			return; // We shouldn't be here
+		}
+
+		switch ( $details['action'] ) {
+			case 'update':
+				$state  = array(
+					'is_autoupdate' => Jetpack_Constants::is_true( 'JETPACK_PLUGIN_AUTOUPDATE' ),
+				);
+				$errors = $this->get_errors( $upgrader->skin );
+				if ( $errors ) {
+					foreach ( $plugins as $slug ) {
+						/**
+						 * Sync that a plugin update failed
+						 *
+						 * @since  5.8.0
+						 *
+						 * @module sync
+						 *
+						 * @param string $plugin , Plugin slug
+						 * @param        string  Error code
+						 * @param        string  Error message
+						 */
+						do_action( 'jetpack_plugin_update_failed', $this->get_plugin_info( $slug ), $errors['code'], $errors['message'], $state );
+					}
+
+					return;
+				}
+				/**
+				 * Sync that a plugin update
+				 *
+				 * @since  5.8.0
+				 *
+				 * @module sync
+				 *
+				 * @param array () $plugin, Plugin Data
+				 */
+				do_action( 'jetpack_plugins_updated', array_map( array( $this, 'get_plugin_info' ), $plugins ), $state );
+				break;
+			case 'install':
+		}
+
+		if ( 'install' === $details['action'] ) {
+			/**
+			 * Signals to the sync listener that a plugin was installed and a sync action
+			 * reflecting the installation and the plugin info should be sent
+			 *
+			 * @since  5.8.0
+			 *
+			 * @module sync
+			 *
+			 * @param array () $plugin, Plugin Data
+			 */
+			do_action( 'jetpack_plugin_installed', array_map( array( $this, 'get_plugin_info' ), $plugins ) );
+
+			return;
+		}
+	}
+
+	private function get_plugin_info( $slug ) {
+		$plugins = get_plugins(); // Get the most up to date info
+		if ( isset( $plugins[ $slug ] ) ) {
+			return array_merge( array( 'slug' => $slug ), $plugins[ $slug ] );
+		};
+		// Try grabbing the info from before the update
+		return isset( $this->plugins[ $slug ] ) ? array_merge( array( 'slug' => $slug ), $this->plugins[ $slug ] ) : array( 'slug' => $slug );
+	}
+
+	private function get_errors( $skin ) {
+		$errors = method_exists( $skin, 'get_errors' ) ? $skin->get_errors() : null;
+		if ( is_wp_error( $errors ) ) {
+			$error_code = $errors->get_error_code();
+			if ( ! empty( $error_code ) ) {
+				return array(
+					'code'    => $error_code,
+					'message' => $errors->get_error_message(),
+				);
+			}
+		}
+
+		if ( isset( $skin->result ) ) {
+			$errors = $skin->result;
+			if ( is_wp_error( $errors ) ) {
+				return array(
+					'code'    => $errors->get_error_code(),
+					'message' => $errors->get_error_message(),
+				);
+			}
+
+			if ( false == $skin->result ) {
+				return array(
+					'code'    => 'unknown',
+					'message' => __( 'Unknown Plugin Update Failure', 'jetpack' ),
+				);
+			}
+		}
+		return false;
+	}
+
+	public function check_plugin_edit() {
+		$screen = get_current_screen();
+		if ( 'plugin-editor' !== $screen->base ||
+			! isset( $_POST['newcontent'] ) ||
+			! isset( $_POST['plugin'] )
+		) {
+			return;
+		}
+
+		$plugin  = $_POST['plugin'];
+		$plugins = get_plugins();
+		if ( ! isset( $plugins[ $plugin ] ) ) {
+			return;
+		}
+
+		/**
+		 * Helps Sync log that a plugin was edited
+		 *
+		 * @since 4.9.0
+		 *
+		 * @param string $plugin, Plugin slug
+		 * @param mixed $plugins[ $plugin ], Array of plugin data
+		 */
+		do_action( 'jetpack_edited_plugin', $plugin, $plugins[ $plugin ] );
+	}
+
+	public function plugin_edit_ajax() {
+		// this validation is based on wp_edit_theme_plugin_file()
+		$args = wp_unslash( $_POST );
+		if ( empty( $args['file'] ) ) {
+			return;
+		}
+
+		$file = $args['file'];
+		if ( 0 !== validate_file( $file ) ) {
+			return;
+		}
+
+		if ( ! isset( $args['newcontent'] ) ) {
+			return;
+		}
+
+		if ( ! isset( $args['nonce'] ) ) {
+			return;
+		}
+
+		if ( empty( $args['plugin'] ) ) {
+			return;
+		}
+
+		$plugin = $args['plugin'];
+		if ( ! current_user_can( 'edit_plugins' ) ) {
+			return;
+		}
+
+		if ( ! wp_verify_nonce( $args['nonce'], 'edit-plugin_' . $file ) ) {
+			return;
+		}
+		$plugins = get_plugins();
+		if ( ! array_key_exists( $plugin, $plugins ) ) {
+			return;
+		}
+
+		if ( 0 !== validate_file( $file, get_plugin_files( $plugin ) ) ) {
+			return;
+		}
+
+		$real_file = WP_PLUGIN_DIR . '/' . $file;
+
+		if ( ! is_writeable( $real_file ) ) {
+			return;
+		}
+
+		$file_pointer = fopen( $real_file, 'w+' );
+		if ( false === $file_pointer ) {
+			return;
+		}
+		fclose( $file_pointer );
+		/**
+		 * This action is documented already in this file
+		 */
+		do_action( 'jetpack_edited_plugin', $plugin, $plugins[ $plugin ] );
+	}
+
+	public function delete_plugin( $plugin_path ) {
+		$full_plugin_path = WP_PLUGIN_DIR . DIRECTORY_SEPARATOR . $plugin_path;
+
+		// Checking for file existence because some sync plugin module tests simulate plugin installation and deletion without putting file on disk
+		if ( file_exists( $full_plugin_path ) ) {
+			$all_plugin_data = get_plugin_data( $full_plugin_path );
+			$data            = array(
+				'name'    => $all_plugin_data['Name'],
+				'version' => $all_plugin_data['Version'],
+			);
+		} else {
+			$data = array(
+				'name'    => $plugin_path,
+				'version' => 'unknown',
+			);
+		}
+
+		$this->plugin_info[ $plugin_path ] = $data;
+	}
+
+	public function deleted_plugin( $plugin_path, $is_deleted ) {
+		call_user_func( $this->action_handler, $plugin_path, $is_deleted, $this->plugin_info[ $plugin_path ] );
+		unset( $this->plugin_info[ $plugin_path ] );
+	}
+
+	public function expand_plugin_data( $args ) {
+		$plugin_path = $args[0];
+		$plugin_data = array();
+
+		if ( ! function_exists( 'get_plugins' ) ) {
+			require_once ABSPATH . 'wp-admin/includes/plugin.php';
+		}
+		$all_plugins = get_plugins();
+		if ( isset( $all_plugins[ $plugin_path ] ) ) {
+			$all_plugin_data        = $all_plugins[ $plugin_path ];
+			$plugin_data['name']    = $all_plugin_data['Name'];
+			$plugin_data['version'] = $all_plugin_data['Version'];
+		}
+
+		return array(
+			$args[0],
+			$args[1],
+			$plugin_data,
+		);
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-posts.php b/plugins/jetpack/sync/class.jetpack-sync-module-posts.php
new file mode 100644
index 00000000..0384b64f
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-posts.php
@@ -0,0 +1,431 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+
+class Jetpack_Sync_Module_Posts extends Jetpack_Sync_Module {
+
+	private $just_published  = array();
+	private $previous_status = array();
+	private $action_handler;
+	private $import_end = false;
+
+	const DEFAULT_PREVIOUS_STATE = 'new';
+
+	public function name() {
+		return 'posts';
+	}
+
+	public function get_object_by_id( $object_type, $id ) {
+		if ( $object_type === 'post' && $post = get_post( intval( $id ) ) ) {
+			return $this->filter_post_content_and_add_links( $post );
+		}
+
+		return false;
+	}
+
+	public function init_listeners( $callable ) {
+		$this->action_handler = $callable;
+
+		add_action( 'wp_insert_post', array( $this, 'wp_insert_post' ), 11, 3 );
+		add_action( 'jetpack_sync_save_post', $callable, 10, 4 );
+
+		add_action( 'deleted_post', $callable, 10 );
+		add_action( 'jetpack_published_post', $callable, 10, 2 );
+
+		add_action( 'transition_post_status', array( $this, 'save_published' ), 10, 3 );
+		add_filter( 'jetpack_sync_before_enqueue_jetpack_sync_save_post', array( $this, 'filter_blacklisted_post_types' ) );
+
+		// listen for meta changes
+		$this->init_listeners_for_meta_type( 'post', $callable );
+		$this->init_meta_whitelist_handler( 'post', array( $this, 'filter_meta' ) );
+
+		add_action( 'jetpack_daily_akismet_meta_cleanup_before', array( $this, 'daily_akismet_meta_cleanup_before' ) );
+		add_action( 'jetpack_daily_akismet_meta_cleanup_after', array( $this, 'daily_akismet_meta_cleanup_after' ) );
+		add_action( 'jetpack_post_meta_batch_delete', $callable, 10, 2 );
+
+	}
+
+
+	public function daily_akismet_meta_cleanup_before( $feedback_ids ) {
+		remove_action( 'deleted_post_meta', $this->action_handler );
+		/**
+		 * Used for syncing deletion of batch post meta
+		 *
+		 * @since 6.1.0
+		 *
+		 * @module sync
+		 *
+		 * @param array $feedback_ids feedback post IDs
+		 * @param string $meta_key to be deleted
+		 */
+		do_action( 'jetpack_post_meta_batch_delete', $feedback_ids, '_feedback_akismet_values' );
+	}
+
+	public function daily_akismet_meta_cleanup_after( $feedback_ids ) {
+		add_action( 'deleted_post_meta', $this->action_handler );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_posts', $callable ); // also sends post meta
+	}
+
+	public function init_before_send() {
+		add_filter( 'jetpack_sync_before_send_jetpack_sync_save_post', array( $this, 'expand_jetpack_sync_save_post' ) );
+
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_posts', array( $this, 'expand_post_ids' ) );
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		global $wpdb;
+
+		return $this->enqueue_all_ids_as_action( 'jetpack_full_sync_posts', $wpdb->posts, 'ID', $this->get_where_sql( $config ), $max_items_to_enqueue, $state );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		global $wpdb;
+
+		$query = "SELECT count(*) FROM $wpdb->posts WHERE " . $this->get_where_sql( $config );
+		$count = $wpdb->get_var( $query );
+
+		return (int) ceil( $count / self::ARRAY_CHUNK_SIZE );
+	}
+
+	private function get_where_sql( $config ) {
+		$where_sql = Jetpack_Sync_Settings::get_blacklisted_post_types_sql();
+
+		// config is a list of post IDs to sync
+		if ( is_array( $config ) ) {
+			$where_sql .= ' AND ID IN (' . implode( ',', array_map( 'intval', $config ) ) . ')';
+		}
+
+		return $where_sql;
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_posts' );
+	}
+
+	/**
+	 * Process content before send
+	 *
+	 * @param array $args wp_insert_post arguments
+	 *
+	 * @return array
+	 */
+	function expand_jetpack_sync_save_post( $args ) {
+		list( $post_id, $post, $update, $previous_state ) = $args;
+		return array( $post_id, $this->filter_post_content_and_add_links( $post ), $update, $previous_state );
+	}
+
+	function filter_blacklisted_post_types( $args ) {
+		$post = $args[1];
+
+		if ( in_array( $post->post_type, Jetpack_Sync_Settings::get_setting( 'post_types_blacklist' ) ) ) {
+			return false;
+		}
+
+		return $args;
+	}
+
+	// Meta
+	function filter_meta( $args ) {
+		if ( $this->is_post_type_allowed( $args[1] ) && $this->is_whitelisted_post_meta( $args[2] ) ) {
+			return $args;
+		}
+
+		return false;
+	}
+
+	function is_whitelisted_post_meta( $meta_key ) {
+		// _wpas_skip_ is used by publicize
+		return in_array( $meta_key, Jetpack_Sync_Settings::get_setting( 'post_meta_whitelist' ) ) || wp_startswith( $meta_key, '_wpas_skip_' );
+	}
+
+	function is_post_type_allowed( $post_id ) {
+		$post = get_post( intval( $post_id ) );
+		if ( $post->post_type ) {
+			return ! in_array( $post->post_type, Jetpack_Sync_Settings::get_setting( 'post_types_blacklist' ) );
+		}
+		return false;
+	}
+
+	function remove_embed() {
+		global $wp_embed;
+		remove_filter( 'the_content', array( $wp_embed, 'run_shortcode' ), 8 );
+		// remove the embed shortcode since we would do the part later.
+		remove_shortcode( 'embed' );
+		// Attempts to embed all URLs in a post
+		remove_filter( 'the_content', array( $wp_embed, 'autoembed' ), 8 );
+	}
+
+	function add_embed() {
+		global $wp_embed;
+		add_filter( 'the_content', array( $wp_embed, 'run_shortcode' ), 8 );
+		// Shortcode placeholder for strip_shortcodes()
+		add_shortcode( 'embed', '__return_false' );
+		// Attempts to embed all URLs in a post
+		add_filter( 'the_content', array( $wp_embed, 'autoembed' ), 8 );
+	}
+
+	// Expands wp_insert_post to include filtered content
+	function filter_post_content_and_add_links( $post_object ) {
+		global $post;
+		$post = $post_object;
+
+		// return non existant post
+		$post_type = get_post_type_object( $post->post_type );
+		if ( empty( $post_type ) || ! is_object( $post_type ) ) {
+			$non_existant_post                    = new stdClass();
+			$non_existant_post->ID                = $post->ID;
+			$non_existant_post->post_modified     = $post->post_modified;
+			$non_existant_post->post_modified_gmt = $post->post_modified_gmt;
+			$non_existant_post->post_status       = 'jetpack_sync_non_registered_post_type';
+			$non_existant_post->post_type         = $post->post_type;
+
+			return $non_existant_post;
+		}
+		/**
+		 * Filters whether to prevent sending post data to .com
+		 *
+		 * Passing true to the filter will prevent the post data from being sent
+		 * to the WordPress.com.
+		 * Instead we pass data that will still enable us to do a checksum against the
+		 * Jetpacks data but will prevent us from displaying the data on in the API as well as
+		 * other services.
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean false prevent post data from being synced to WordPress.com
+		 * @param mixed $post WP_POST object
+		 */
+		if ( apply_filters( 'jetpack_sync_prevent_sending_post_data', false, $post ) ) {
+			// We only send the bare necessary object to be able to create a checksum.
+			$blocked_post                    = new stdClass();
+			$blocked_post->ID                = $post->ID;
+			$blocked_post->post_modified     = $post->post_modified;
+			$blocked_post->post_modified_gmt = $post->post_modified_gmt;
+			$blocked_post->post_status       = 'jetpack_sync_blocked';
+			$blocked_post->post_type         = $post->post_type;
+
+			return $blocked_post;
+		}
+
+		// lets not do oembed just yet.
+		$this->remove_embed();
+
+		if ( 0 < strlen( $post->post_password ) ) {
+			$post->post_password = 'auto-' . wp_generate_password( 10, false );
+		}
+
+		/** This filter is already documented in core. wp-includes/post-template.php */
+		if ( Jetpack_Sync_Settings::get_setting( 'render_filtered_content' ) && $post_type->public ) {
+			global $shortcode_tags;
+			/**
+			 * Filter prevents some shortcodes from expanding.
+			 *
+			 * Since we can can expand some type of shortcode better on the .com side and make the
+			 * expansion more relevant to contexts. For example [galleries] and subscription emails
+			 *
+			 * @since 4.5.0
+			 *
+			 * @param array of shortcode tags to remove.
+			 */
+			$shortcodes_to_remove        = apply_filters(
+				'jetpack_sync_do_not_expand_shortcodes',
+				array(
+					'gallery',
+					'slideshow',
+				)
+			);
+			$removed_shortcode_callbacks = array();
+			foreach ( $shortcodes_to_remove as $shortcode ) {
+				if ( isset( $shortcode_tags[ $shortcode ] ) ) {
+					$removed_shortcode_callbacks[ $shortcode ] = $shortcode_tags[ $shortcode ];
+				}
+			}
+
+			array_map( 'remove_shortcode', array_keys( $removed_shortcode_callbacks ) );
+
+			$post->post_content_filtered = apply_filters( 'the_content', $post->post_content );
+			$post->post_excerpt_filtered = apply_filters( 'the_excerpt', $post->post_excerpt );
+
+			foreach ( $removed_shortcode_callbacks as $shortcode => $callback ) {
+				add_shortcode( $shortcode, $callback );
+			}
+		}
+
+		$this->add_embed();
+
+		if ( has_post_thumbnail( $post->ID ) ) {
+			$image_attributes = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' );
+			if ( is_array( $image_attributes ) && isset( $image_attributes[0] ) ) {
+				$post->featured_image = $image_attributes[0];
+			}
+		}
+
+		$post->permalink = get_permalink( $post->ID );
+		$post->shortlink = wp_get_shortlink( $post->ID );
+
+		if ( function_exists( 'amp_get_permalink' ) ) {
+			$post->amp_permalink = amp_get_permalink( $post->ID );
+		}
+
+		return $post;
+	}
+
+	public function save_published( $new_status, $old_status, $post ) {
+		if ( 'publish' === $new_status && 'publish' !== $old_status ) {
+			$this->just_published[ $post->ID ] = true;
+		}
+
+		$this->previous_status[ $post->ID ] = $old_status;
+	}
+
+	/*
+	 * When publishing or updating a post, the Gutenberg editor sends two requests:
+	 * 1. sent to WP REST API endpoint `wp-json/wp/v2/posts/$id`
+	 * 2. sent to wp-admin/post.php `?post=$id&action=edit&classic-editor=1&meta_box=1`
+	 *
+	 * The 2nd request is to update post meta, which is not supported on WP REST API.
+	 * When syncing post data, we will include if this was a meta box update.
+	 */
+	public function is_gutenberg_meta_box_update() {
+		return (
+			isset( $_POST['action'], $_GET['classic-editor'], $_GET['meta_box'] ) &&
+			'editpost' === $_POST['action'] &&
+			'1' === $_GET['classic-editor'] &&
+			'1' === $_GET['meta_box']
+		);
+	}
+
+	public function wp_insert_post( $post_ID, $post = null, $update = null ) {
+		if ( ! is_numeric( $post_ID ) || is_null( $post ) ) {
+			return;
+		}
+
+		// workaround for https://github.com/woocommerce/woocommerce/issues/18007
+		if ( $post && 'shop_order' === $post->post_type ) {
+			$post = get_post( $post_ID );
+		}
+
+		$previous_status = isset( $this->previous_status[ $post_ID ] ) ?
+			$this->previous_status[ $post_ID ] :
+			self::DEFAULT_PREVIOUS_STATE;
+
+		$just_published = isset( $this->just_published[ $post_ID ] ) ?
+			$this->just_published[ $post_ID ] :
+			false;
+
+		$state = array(
+			'is_auto_save'                 => (bool) Jetpack_Constants::get_constant( 'DOING_AUTOSAVE' ),
+			'previous_status'              => $previous_status,
+			'just_published'               => $just_published,
+			'is_gutenberg_meta_box_update' => $this->is_gutenberg_meta_box_update(),
+		);
+		/**
+		 * Filter that is used to add to the post flags ( meta data ) when a post gets published
+		 *
+		 * @since 5.8.0
+		 *
+		 * @param int $post_ID the post ID
+		 * @param mixed $post WP_POST object
+		 * @param bool  $update Whether this is an existing post being updated or not.
+		 * @param mixed $state state
+		 *
+		 * @module sync
+		 */
+		do_action( 'jetpack_sync_save_post', $post_ID, $post, $update, $state );
+		unset( $this->previous_status[ $post_ID ] );
+		$this->send_published( $post_ID, $post );
+	}
+
+	public function send_published( $post_ID, $post ) {
+		if ( ! isset( $this->just_published[ $post_ID ] ) ) {
+			return;
+		}
+
+		// Post revisions cause race conditions where this send_published add the action before the actual post gets synced
+		if ( wp_is_post_autosave( $post ) || wp_is_post_revision( $post ) ) {
+			return;
+		}
+
+		$post_flags = array(
+			'post_type' => $post->post_type,
+		);
+
+		$author_user_object = get_user_by( 'id', $post->post_author );
+		if ( $author_user_object ) {
+			$post_flags['author'] = array(
+				'id'              => $post->post_author,
+				'wpcom_user_id'   => get_user_meta( $post->post_author, 'wpcom_user_id', true ),
+				'display_name'    => $author_user_object->display_name,
+				'email'           => $author_user_object->user_email,
+				'translated_role' => Jetpack::translate_user_to_role( $author_user_object ),
+			);
+		}
+
+		/**
+		 * Filter that is used to add to the post flags ( meta data ) when a post gets published
+		 *
+		 * @since 4.4.0
+		 *
+		 * @param mixed array post flags that are added to the post
+		 * @param mixed $post WP_POST object
+		 */
+		$flags = apply_filters( 'jetpack_published_post_flags', $post_flags, $post );
+
+		/**
+		 * Action that gets synced when a post type gets published.
+		 *
+		 * @since 4.4.0
+		 *
+		 * @param int $post_ID
+		 * @param mixed array $flags post flags that are added to the post
+		 */
+		do_action( 'jetpack_published_post', $post_ID, $flags );
+		unset( $this->just_published[ $post_ID ] );
+
+		/**
+		 * Send additional sync action for Activity Log when post is a Customizer publish
+		 */
+		if ( 'customize_changeset' == $post->post_type ) {
+			$post_content = json_decode( $post->post_content, true );
+			foreach ( $post_content as $key => $value ) {
+				// Skip if it isn't a widget
+				if ( 'widget_' != substr( $key, 0, strlen( 'widget_' ) ) ) {
+					continue;
+				}
+				// Change key from "widget_archives[2]" to "archives-2"
+				$key = str_replace( 'widget_', '', $key );
+				$key = str_replace( '[', '-', $key );
+				$key = str_replace( ']', '', $key );
+
+				global $wp_registered_widgets;
+				if ( isset( $wp_registered_widgets[ $key ] ) ) {
+					$widget_data = array(
+						'name'  => $wp_registered_widgets[ $key ]['name'],
+						'id'    => $key,
+						'title' => $value['value']['title'],
+					);
+					do_action( 'jetpack_widget_edited', $widget_data );
+				}
+			}
+		}
+	}
+
+	public function expand_post_ids( $args ) {
+		list( $post_ids, $previous_interval_end) = $args;
+
+		$posts = array_filter( array_map( array( 'WP_Post', 'get_instance' ), $post_ids ) );
+		$posts = array_map( array( $this, 'filter_post_content_and_add_links' ), $posts );
+		$posts = array_values( $posts ); // reindex in case posts were deleted
+
+		return array(
+			$posts,
+			$this->get_metadata( $post_ids, 'post', Jetpack_Sync_Settings::get_setting( 'post_meta_whitelist' ) ),
+			$this->get_term_relationships( $post_ids ),
+			$previous_interval_end
+		);
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-protect.php b/plugins/jetpack/sync/class.jetpack-sync-module-protect.php
new file mode 100644
index 00000000..a8dcd43e
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-protect.php
@@ -0,0 +1,23 @@
+<?php
+
+/**
+ * logs bruteprotect failed logins via sync
+ */
+class Jetpack_Sync_Module_Protect extends Jetpack_Sync_Module {
+
+	function name() {
+		return 'protect';
+	}
+
+	function init_listeners( $callback ) {
+		add_action( 'jpp_log_failed_attempt', array( $this, 'maybe_log_failed_login_attempt' ) );
+		add_action( 'jetpack_valid_failed_login_attempt', $callback );
+	}
+
+	function maybe_log_failed_login_attempt( $failed_attempt ) {
+		$protect = Jetpack_Protect_Module::instance();
+		if ( $protect->has_login_ability() && ! Jetpack_Constants::is_true( 'XMLRPC_REQUEST' ) ) {
+			do_action( 'jetpack_valid_failed_login_attempt', $failed_attempt );
+		}
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-stats.php b/plugins/jetpack/sync/class.jetpack-sync-module-stats.php
new file mode 100644
index 00000000..d23d3e00
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-stats.php
@@ -0,0 +1,28 @@
+<?php
+
+class Jetpack_Sync_Module_Stats extends Jetpack_Sync_Module {
+
+	function name() {
+		return 'stats';
+	}
+
+	function init_listeners( $callback ) {
+		add_action( 'jetpack_heartbeat', array( $this, 'sync_site_stats' ), 20 );
+		add_action( 'jetpack_sync_heartbeat_stats', $callback );
+	}
+	/*
+	 * This namespaces the action that we sync.
+	 * So that we can differentiate it from future actions.
+	 */
+	public function sync_site_stats() {
+		do_action( 'jetpack_sync_heartbeat_stats' );
+	}
+
+	public function init_before_send() {
+		add_filter( 'jetpack_sync_before_send_jetpack_sync_heartbeat_stats', array( $this, 'add_stats' ) );
+	}
+
+	public function add_stats() {
+		return array( Jetpack::get_stat_data( false, false ) );
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-terms.php b/plugins/jetpack/sync/class.jetpack-sync-module-terms.php
new file mode 100644
index 00000000..f09371c6
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-terms.php
@@ -0,0 +1,114 @@
+<?php
+
+class Jetpack_Sync_Module_Terms extends Jetpack_Sync_Module {
+	private $taxonomy_whitelist;
+
+	function name() {
+		return 'terms';
+	}
+
+	function init_listeners( $callable ) {
+		add_action( 'created_term', array( $this, 'save_term_handler' ), 10, 3 );
+		add_action( 'edited_term', array( $this, 'save_term_handler' ), 10, 3 );
+		add_action( 'jetpack_sync_save_term', $callable );
+		add_action( 'jetpack_sync_add_term', $callable );
+		add_action( 'delete_term', $callable, 10, 4 );
+		add_action( 'set_object_terms', $callable, 10, 6 );
+		add_action( 'deleted_term_relationships', $callable, 10, 2 );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_terms', $callable, 10, 2 );
+	}
+
+	function init_before_send() {
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_terms', array( $this, 'expand_term_taxonomy_id' ) );
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		global $wpdb;
+		return $this->enqueue_all_ids_as_action( 'jetpack_full_sync_terms', $wpdb->term_taxonomy, 'term_taxonomy_id', $this->get_where_sql( $config ), $max_items_to_enqueue, $state );
+	}
+
+	private function get_where_sql( $config ) {
+		if ( is_array( $config ) ) {
+			return 'term_taxonomy_id IN (' . implode( ',', array_map( 'intval', $config ) ) . ')';
+		}
+
+		return '';
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		global $wpdb;
+
+		$query = "SELECT count(*) FROM $wpdb->term_taxonomy";
+
+		if ( $where_sql = $this->get_where_sql( $config ) ) {
+			$query .= ' WHERE ' . $where_sql;
+		}
+
+		$count = $wpdb->get_var( $query );
+
+		return (int) ceil( $count / self::ARRAY_CHUNK_SIZE );
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_terms' );
+	}
+
+	function save_term_handler( $term_id, $tt_id, $taxonomy ) {
+		if ( class_exists( 'WP_Term' ) ) {
+			$term_object = WP_Term::get_instance( $term_id, $taxonomy );
+		} else {
+			$term_object = get_term_by( 'id', $term_id, $taxonomy );
+		}
+
+		$current_filter = current_filter();
+
+		if ( 'created_term' === $current_filter ) {
+			/**
+			 * Fires when the client needs to add a new term
+			 *
+			 * @since 5.0.0
+			 *
+			 * @param object the Term object
+			 */
+			do_action( 'jetpack_sync_add_term', $term_object );
+			return;
+		}
+
+		/**
+		 * Fires when the client needs to update a term
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param object the Term object
+		 */
+		do_action( 'jetpack_sync_save_term', $term_object );
+	}
+
+	function set_taxonomy_whitelist( $taxonomies ) {
+		$this->taxonomy_whitelist = $taxonomies;
+	}
+
+	function set_defaults() {
+		$this->taxonomy_whitelist = Jetpack_Sync_Defaults::$default_taxonomy_whitelist;
+	}
+
+	public function expand_term_taxonomy_id( $args ) {
+		list( $term_taxonomy_ids,  $previous_end ) = $args;
+
+		return
+			array( 'terms' => get_terms(
+				array(
+					'hide_empty'       => false,
+					'term_taxonomy_id' => $term_taxonomy_ids,
+					'orderby'          => 'term_taxonomy_id',
+					'order'            => 'DESC'
+				)
+			),
+			'previous_end' => $previous_end
+		);
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-themes.php b/plugins/jetpack/sync/class.jetpack-sync-module-themes.php
new file mode 100644
index 00000000..e8b4185d
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-themes.php
@@ -0,0 +1,612 @@
+<?php
+
+class Jetpack_Sync_Module_Themes extends Jetpack_Sync_Module {
+	function name() {
+		return 'themes';
+	}
+
+	public function init_listeners( $callable ) {
+		add_action( 'switch_theme', array( $this, 'sync_theme_support' ), 10, 3 );
+		add_action( 'jetpack_sync_current_theme_support', $callable, 10, 2 );
+		add_action( 'upgrader_process_complete', array( $this, 'check_upgrader' ), 10, 2 );
+		add_action( 'jetpack_installed_theme', $callable, 10, 2 );
+		add_action( 'jetpack_updated_themes', $callable, 10, 2 );
+		add_action( 'delete_site_transient_update_themes', array( $this, 'detect_theme_deletion' ) );
+		add_action( 'jetpack_deleted_theme', $callable, 10, 2 );
+		add_filter( 'wp_redirect', array( $this, 'detect_theme_edit' ) );
+		add_action( 'jetpack_edited_theme', $callable, 10, 2 );
+		add_action( 'wp_ajax_edit-theme-plugin-file', array( $this, 'theme_edit_ajax' ), 0 );
+		add_action( 'update_site_option_allowedthemes', array( $this, 'sync_network_allowed_themes_change' ), 10, 4 );
+		add_action( 'jetpack_network_disabled_themes', $callable, 10, 2 );
+		add_action( 'jetpack_network_enabled_themes', $callable, 10, 2 );
+
+		// Sidebar updates.
+		add_action( 'update_option_sidebars_widgets', array( $this, 'sync_sidebar_widgets_actions' ), 10, 2 );
+
+		add_action( 'jetpack_widget_added', $callable, 10, 4 );
+		add_action( 'jetpack_widget_removed', $callable, 10, 4 );
+		add_action( 'jetpack_widget_moved_to_inactive', $callable, 10, 2 );
+		add_action( 'jetpack_cleared_inactive_widgets', $callable );
+		add_action( 'jetpack_widget_reordered', $callable, 10, 2 );
+		add_filter( 'widget_update_callback', array( $this, 'sync_widget_edit' ), 10, 4 );
+		add_action( 'jetpack_widget_edited', $callable );
+	}
+
+	public function sync_widget_edit( $instance, $new_instance, $old_instance, $widget_object ) {
+		if ( empty( $old_instance ) ) {
+			return $instance;
+		}
+
+		// Don't trigger sync action if this is an ajax request, because Customizer makes them during preview before saving changes
+		if ( defined( 'DOING_AJAX' ) && DOING_AJAX && isset( $_POST['customized'] ) ) {
+			return $instance;
+		}
+
+		$widget = array(
+			'name'  => $widget_object->name,
+			'id'    => $widget_object->id,
+			'title' => isset( $new_instance['title'] ) ? $new_instance['title'] : '',
+		);
+		/**
+		 * Trigger action to alert $callable sync listener that a widget was edited
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param string $widget_name , Name of edited widget
+		 */
+		do_action( 'jetpack_widget_edited', $widget );
+
+		return $instance;
+	}
+
+	public function sync_network_allowed_themes_change( $option, $value, $old_value, $network_id ) {
+		$all_enabled_theme_slugs = array_keys( $value );
+
+		if ( count( $old_value ) > count( $value ) ) {
+
+			// Suppress jetpack_network_disabled_themes sync action when theme is deleted
+			$delete_theme_call = $this->get_delete_theme_call();
+			if ( ! empty( $delete_theme_call ) ) {
+				return;
+			}
+
+			$newly_disabled_theme_names = array_keys( array_diff_key( $old_value, $value ) );
+			$newly_disabled_themes      = $this->get_theme_details_for_slugs( $newly_disabled_theme_names );
+			/**
+			 * Trigger action to alert $callable sync listener that network themes were disabled
+			 *
+			 * @since 5.0.0
+			 *
+			 * @param mixed $newly_disabled_themes, Array of info about network disabled themes
+			 * @param mixed $all_enabled_theme_slugs, Array of slugs of all enabled themes
+			 */
+			do_action( 'jetpack_network_disabled_themes', $newly_disabled_themes, $all_enabled_theme_slugs );
+			return;
+		}
+
+		$newly_enabled_theme_names = array_keys( array_diff_key( $value, $old_value ) );
+		$newly_enabled_themes      = $this->get_theme_details_for_slugs( $newly_enabled_theme_names );
+		/**
+		 * Trigger action to alert $callable sync listener that network themes were enabled
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param mixed $newly_enabled_themes , Array of info about network enabled themes
+		 * @param mixed $all_enabled_theme_slugs, Array of slugs of all enabled themes
+		 */
+		do_action( 'jetpack_network_enabled_themes', $newly_enabled_themes, $all_enabled_theme_slugs );
+	}
+
+	private function get_theme_details_for_slugs( $theme_slugs ) {
+		$theme_data = array();
+		foreach ( $theme_slugs as $slug ) {
+			$theme               = wp_get_theme( $slug );
+			$theme_data[ $slug ] = array(
+				'name'    => $theme->get( 'Name' ),
+				'version' => $theme->get( 'Version' ),
+				'uri'     => $theme->get( 'ThemeURI' ),
+				'slug'    => $slug,
+			);
+		}
+		return $theme_data;
+	}
+
+	public function detect_theme_edit( $redirect_url ) {
+		$url              = wp_parse_url( admin_url( $redirect_url ) );
+		$theme_editor_url = wp_parse_url( admin_url( 'theme-editor.php' ) );
+
+		if ( $theme_editor_url['path'] !== $url['path'] ) {
+			return $redirect_url;
+		}
+
+		$query_params = array();
+		wp_parse_str( $url['query'], $query_params );
+		if (
+			! isset( $_POST['newcontent'] ) ||
+			! isset( $query_params['file'] ) ||
+			! isset( $query_params['theme'] ) ||
+			! isset( $query_params['updated'] )
+		) {
+			return $redirect_url;
+		}
+		$theme      = wp_get_theme( $query_params['theme'] );
+		$theme_data = array(
+			'name'    => $theme->get( 'Name' ),
+			'version' => $theme->get( 'Version' ),
+			'uri'     => $theme->get( 'ThemeURI' ),
+		);
+
+		/**
+		 * Trigger action to alert $callable sync listener that a theme was edited
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param string $query_params['theme'], Slug of edited theme
+		 * @param string $theme_data, Information about edited them
+		 */
+		do_action( 'jetpack_edited_theme', $query_params['theme'], $theme_data );
+
+		return $redirect_url;
+	}
+
+	public function theme_edit_ajax() {
+		$args = wp_unslash( $_POST );
+
+		if ( empty( $args['theme'] ) ) {
+			return;
+		}
+
+		if ( empty( $args['file'] ) ) {
+			return;
+		}
+		$file = $args['file'];
+		if ( 0 !== validate_file( $file ) ) {
+			return;
+		}
+
+		if ( ! isset( $args['newcontent'] ) ) {
+			return;
+		}
+
+		if ( ! isset( $args['nonce'] ) ) {
+			return;
+		}
+
+		$stylesheet = $args['theme'];
+		if ( 0 !== validate_file( $stylesheet ) ) {
+			return;
+		}
+
+		if ( ! current_user_can( 'edit_themes' ) ) {
+			return;
+		}
+
+		$theme = wp_get_theme( $stylesheet );
+		if ( ! $theme->exists() ) {
+			return;
+		}
+
+		$real_file = $theme->get_stylesheet_directory() . '/' . $file;
+		if ( ! wp_verify_nonce( $args['nonce'], 'edit-theme_' . $real_file . $stylesheet ) ) {
+			return;
+		}
+
+		if ( $theme->errors() && 'theme_no_stylesheet' === $theme->errors()->get_error_code() ) {
+			return;
+		}
+
+		$editable_extensions = wp_get_theme_file_editable_extensions( $theme );
+
+		$allowed_files = array();
+		foreach ( $editable_extensions as $type ) {
+			switch ( $type ) {
+				case 'php':
+					$allowed_files = array_merge( $allowed_files, $theme->get_files( 'php', -1 ) );
+					break;
+				case 'css':
+					$style_files                = $theme->get_files( 'css', -1 );
+					$allowed_files['style.css'] = $style_files['style.css'];
+					$allowed_files              = array_merge( $allowed_files, $style_files );
+					break;
+				default:
+					$allowed_files = array_merge( $allowed_files, $theme->get_files( $type, -1 ) );
+					break;
+			}
+		}
+
+		if ( 0 !== validate_file( $real_file, $allowed_files ) ) {
+			return;
+		}
+
+		// Ensure file is real.
+		if ( ! is_file( $real_file ) ) {
+			return;
+		}
+
+		// Ensure file extension is allowed.
+		$extension = null;
+		if ( preg_match( '/\.([^.]+)$/', $real_file, $matches ) ) {
+			$extension = strtolower( $matches[1] );
+			if ( ! in_array( $extension, $editable_extensions, true ) ) {
+				return;
+			}
+		}
+
+		if ( ! is_writeable( $real_file ) ) {
+			return;
+		}
+
+		$file_pointer = fopen( $real_file, 'w+' );
+		if ( false === $file_pointer ) {
+			return;
+		}
+		fclose( $file_pointer );
+
+		$theme_data = array(
+			'name'    => $theme->get( 'Name' ),
+			'version' => $theme->get( 'Version' ),
+			'uri'     => $theme->get( 'ThemeURI' ),
+		);
+
+		/**
+		 * This action is documented already in this file
+		 */
+		do_action( 'jetpack_edited_theme', $stylesheet, $theme_data );
+
+	}
+
+	public function detect_theme_deletion() {
+		$delete_theme_call = $this->get_delete_theme_call();
+		if ( empty( $delete_theme_call ) ) {
+			return;
+		}
+
+		$slug       = $delete_theme_call['args'][0];
+		$theme      = wp_get_theme( $slug );
+		$theme_data = array(
+			'name'    => $theme->get( 'Name' ),
+			'version' => $theme->get( 'Version' ),
+			'uri'     => $theme->get( 'ThemeURI' ),
+			'slug'    => $slug,
+		);
+
+		/**
+		 * Signals to the sync listener that a theme was deleted and a sync action
+		 * reflecting the deletion and theme slug should be sent
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param string $slug Theme slug
+		 * @param array $theme_data Theme info Since 5.3
+		 */
+		do_action( 'jetpack_deleted_theme', $slug, $theme_data );
+	}
+
+	public function check_upgrader( $upgrader, $details ) {
+		if ( ! isset( $details['type'] ) ||
+			 'theme' !== $details['type'] ||
+			 is_wp_error( $upgrader->skin->result ) ||
+			 ! method_exists( $upgrader, 'theme_info' )
+		) {
+			return;
+		}
+
+		if ( 'install' === $details['action'] ) {
+			$theme = $upgrader->theme_info();
+			if ( ! $theme instanceof WP_Theme ) {
+				return;
+			}
+			$theme_info = array(
+				'name'    => $theme->get( 'Name' ),
+				'version' => $theme->get( 'Version' ),
+				'uri'     => $theme->get( 'ThemeURI' ),
+			);
+
+			/**
+			 * Signals to the sync listener that a theme was installed and a sync action
+			 * reflecting the installation and the theme info should be sent
+			 *
+			 * @since 4.9.0
+			 *
+			 * @param string $theme->theme_root Text domain of the theme
+			 * @param mixed $theme_info Array of abbreviated theme info
+			 */
+			do_action( 'jetpack_installed_theme', $theme->stylesheet, $theme_info );
+		}
+
+		if ( 'update' === $details['action'] ) {
+			$themes = array();
+
+			if ( empty( $details['themes'] ) && isset( $details['theme'] ) ) {
+				$details['themes'] = array( $details['theme'] );
+			}
+
+			foreach ( $details['themes'] as $theme_slug ) {
+				$theme = wp_get_theme( $theme_slug );
+
+				if ( ! $theme instanceof WP_Theme ) {
+					continue;
+				}
+
+				$themes[ $theme_slug ] = array(
+					'name'       => $theme->get( 'Name' ),
+					'version'    => $theme->get( 'Version' ),
+					'uri'        => $theme->get( 'ThemeURI' ),
+					'stylesheet' => $theme->stylesheet,
+				);
+			}
+
+			if ( empty( $themes ) ) {
+				return;
+			}
+
+			/**
+			 * Signals to the sync listener that one or more themes was updated and a sync action
+			 * reflecting the update and the theme info should be sent
+			 *
+			 * @since 6.2.0
+			 *
+			 * @param mixed $themes Array of abbreviated theme info
+			 */
+			do_action( 'jetpack_updated_themes', $themes );
+		}
+
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_theme_data', $callable );
+	}
+
+	public function sync_theme_support( $new_name, $new_theme = null, $old_theme = null ) {
+		$previous_theme = $this->get_theme_support_info( $old_theme );
+
+		/**
+		 * Fires when the client needs to sync theme support info
+		 * Only sends theme support attributes whitelisted in Jetpack_Sync_Defaults::$default_theme_support_whitelist
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param array the theme support array
+		 * @param array the previous theme since Jetpack 6.5.0
+		 */
+		do_action( 'jetpack_sync_current_theme_support', $this->get_theme_support_info(), $previous_theme );
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		/**
+		 * Tells the client to sync all theme data to the server
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean Whether to expand theme data (should always be true)
+		 */
+		do_action( 'jetpack_full_sync_theme_data', true );
+
+		// The number of actions enqueued, and next module state (true == done)
+		return array( 1, true );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		return 1;
+	}
+
+	public function init_before_send() {
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_theme_data', array( $this, 'expand_theme_data' ) );
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_theme_data' );
+	}
+
+	function expand_theme_data() {
+		return array( $this->get_theme_support_info() );
+	}
+
+	function get_widget_name( $widget_id ) {
+		global $wp_registered_widgets;
+		return ( isset( $wp_registered_widgets[ $widget_id ] ) ? $wp_registered_widgets[ $widget_id ]['name'] : null );
+	}
+
+	function get_sidebar_name( $sidebar_id ) {
+		global $wp_registered_sidebars;
+		return ( isset( $wp_registered_sidebars[ $sidebar_id ] ) ? $wp_registered_sidebars[ $sidebar_id ]['name'] : null );
+	}
+
+	function sync_add_widgets_to_sidebar( $new_widgets, $old_widgets, $sidebar ) {
+		$added_widgets = array_diff( $new_widgets, $old_widgets );
+		if ( empty( $added_widgets ) ) {
+			return array();
+		}
+		$moved_to_sidebar = array();
+		$sidebar_name     = $this->get_sidebar_name( $sidebar );
+
+		// Don't sync jetpack_widget_added if theme was switched
+		if ( $this->is_theme_switch() ) {
+			return array();
+		}
+
+		foreach ( $added_widgets as $added_widget ) {
+			$moved_to_sidebar[] = $added_widget;
+			$added_widget_name  = $this->get_widget_name( $added_widget );
+			/**
+			 * Helps Sync log that a widget got added
+			 *
+			 * @since 4.9.0
+			 *
+			 * @param string $sidebar, Sidebar id got changed
+			 * @param string $added_widget, Widget id got added
+			 * @param string $sidebar_name, Sidebar id got changed Since 5.0.0
+			 * @param string $added_widget_name, Widget id got added Since 5.0.0
+			 */
+			do_action( 'jetpack_widget_added', $sidebar, $added_widget, $sidebar_name, $added_widget_name );
+		}
+		return $moved_to_sidebar;
+	}
+
+	function sync_remove_widgets_from_sidebar( $new_widgets, $old_widgets, $sidebar, $inactive_widgets ) {
+		$removed_widgets = array_diff( $old_widgets, $new_widgets );
+
+		if ( empty( $removed_widgets ) ) {
+			return array();
+		}
+
+		$moved_to_inactive = array();
+		$sidebar_name      = $this->get_sidebar_name( $sidebar );
+
+		foreach ( $removed_widgets as $removed_widget ) {
+			// Lets check if we didn't move the widget to in_active_widgets
+			if ( isset( $inactive_widgets ) && ! in_array( $removed_widget, $inactive_widgets ) ) {
+				$removed_widget_name = $this->get_widget_name( $removed_widget );
+				/**
+				 * Helps Sync log that a widgte got removed
+				 *
+				 * @since 4.9.0
+				 *
+				 * @param string $sidebar, Sidebar id got changed
+				 * @param string $removed_widget, Widget id got removed
+				 * @param string $sidebar_name, Name of the sidebar that changed  Since 5.0.0
+				 * @param string $removed_widget_name, Name of the widget that got removed Since 5.0.0
+				 */
+				do_action( 'jetpack_widget_removed', $sidebar, $removed_widget, $sidebar_name, $removed_widget_name );
+			} else {
+				$moved_to_inactive[] = $removed_widget;
+			}
+		}
+		return $moved_to_inactive;
+
+	}
+
+	function sync_widgets_reordered( $new_widgets, $old_widgets, $sidebar ) {
+		$added_widgets = array_diff( $new_widgets, $old_widgets );
+		if ( ! empty( $added_widgets ) ) {
+			return;
+		}
+		$removed_widgets = array_diff( $old_widgets, $new_widgets );
+		if ( ! empty( $removed_widgets ) ) {
+			return;
+		}
+
+		if ( serialize( $old_widgets ) !== serialize( $new_widgets ) ) {
+			$sidebar_name = $this->get_sidebar_name( $sidebar );
+			/**
+			 * Helps Sync log that a sidebar id got reordered
+			 *
+			 * @since 4.9.0
+			 *
+			 * @param string $sidebar, Sidebar id got changed
+			 * @param string $sidebar_name, Name of the sidebar that changed  Since 5.0.0
+			 */
+			do_action( 'jetpack_widget_reordered', $sidebar, $sidebar_name );
+		}
+
+	}
+
+	function sync_sidebar_widgets_actions( $old_value, $new_value ) {
+		// Don't really know how to deal with different array_values yet.
+		if (
+			( isset( $old_value['array_version'] ) && $old_value['array_version'] !== 3 ) ||
+			( isset( $new_value['array_version'] ) && $new_value['array_version'] !== 3 )
+		) {
+			return;
+		}
+
+		$moved_to_inactive_ids = array();
+		$moved_to_sidebar      = array();
+
+		foreach ( $new_value as $sidebar => $new_widgets ) {
+			if ( in_array( $sidebar, array( 'array_version', 'wp_inactive_widgets' ) ) ) {
+				continue;
+			}
+			$old_widgets = isset( $old_value[ $sidebar ] )
+				? $old_value[ $sidebar ]
+				: array();
+
+			if ( ! is_array( $new_widgets ) ) {
+				$new_widgets = array();
+			}
+
+			$moved_to_inactive_recently = $this->sync_remove_widgets_from_sidebar( $new_widgets, $old_widgets, $sidebar, $new_value['wp_inactive_widgets'] );
+			$moved_to_inactive_ids      = array_merge( $moved_to_inactive_ids, $moved_to_inactive_recently );
+
+			$moved_to_sidebar_recently = $this->sync_add_widgets_to_sidebar( $new_widgets, $old_widgets, $sidebar );
+			$moved_to_sidebar          = array_merge( $moved_to_sidebar, $moved_to_sidebar_recently );
+
+			$this->sync_widgets_reordered( $new_widgets, $old_widgets, $sidebar );
+
+		}
+
+		// Don't sync either jetpack_widget_moved_to_inactive or jetpack_cleared_inactive_widgets if theme was switched
+		if ( $this->is_theme_switch() ) {
+			return;
+		}
+
+		// Treat inactive sidebar a bit differently
+		if ( ! empty( $moved_to_inactive_ids ) ) {
+			$moved_to_inactive_name = array_map( array( $this, 'get_widget_name' ), $moved_to_inactive_ids );
+			/**
+			 * Helps Sync log that a widgets IDs got moved to in active
+			 *
+			 * @since 4.9.0
+			 *
+			 * @param array $moved_to_inactive_ids, Array of widgets id that moved to inactive id got changed
+			 * @param array $moved_to_inactive_names, Array of widgets names that moved to inactive id got changed Since 5.0.0
+			 */
+			do_action( 'jetpack_widget_moved_to_inactive', $moved_to_inactive_ids, $moved_to_inactive_name );
+		} elseif ( empty( $moved_to_sidebar ) &&
+				   empty( $new_value['wp_inactive_widgets'] ) &&
+				   ! empty( $old_value['wp_inactive_widgets'] ) ) {
+			/**
+			 * Helps Sync log that a got cleared from inactive.
+			 *
+			 * @since 4.9.0
+			 */
+			do_action( 'jetpack_cleared_inactive_widgets' );
+		}
+	}
+
+	/**
+	 * @param null $theme or the theme object
+	 *
+	 * @return array
+	 */
+	private function get_theme_support_info( $theme = null ) {
+		global $_wp_theme_features;
+
+		$theme_support = array();
+
+		// We are trying to get the current theme info.
+		if ( $theme === null ) {
+			$theme = wp_get_theme();
+
+			foreach ( Jetpack_Sync_Defaults::$default_theme_support_whitelist as $theme_feature ) {
+				$has_support = current_theme_supports( $theme_feature );
+				if ( $has_support ) {
+					$theme_support[ $theme_feature ] = $_wp_theme_features[ $theme_feature ];
+				}
+			}
+		}
+
+		$theme_support['name']    = $theme->get( 'Name' );
+		$theme_support['version'] = $theme->get( 'Version' );
+		$theme_support['slug']    = $theme->get_stylesheet();
+		$theme_support['uri']     = $theme->get( 'ThemeURI' );
+
+		return $theme_support;
+	}
+
+	private function get_delete_theme_call() {
+		$backtrace         = debug_backtrace();
+		$delete_theme_call = null;
+		foreach ( $backtrace as $call ) {
+			if ( isset( $call['function'] ) && 'delete_theme' === $call['function'] ) {
+				$delete_theme_call = $call;
+				break;
+			}
+		}
+		return $delete_theme_call;
+	}
+
+	private function is_theme_switch() {
+		return did_action( 'after_switch_theme' );
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-updates.php b/plugins/jetpack/sync/class.jetpack-sync-module-updates.php
new file mode 100644
index 00000000..4da4414f
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-updates.php
@@ -0,0 +1,321 @@
+<?php
+
+class Jetpack_Sync_Module_Updates extends Jetpack_Sync_Module {
+
+	const UPDATES_CHECKSUM_OPTION_NAME = 'jetpack_updates_sync_checksum';
+
+	private $old_wp_version = null;
+	private $updates        = array();
+
+	public function set_defaults() {
+		$this->updates = array();
+	}
+
+	function name() {
+		return 'updates';
+	}
+
+	public function init_listeners( $callable ) {
+		global $wp_version;
+		$this->old_wp_version = $wp_version;
+		add_action( 'set_site_transient_update_plugins', array( $this, 'validate_update_change' ), 10, 3 );
+		add_action( 'set_site_transient_update_themes', array( $this, 'validate_update_change' ), 10, 3 );
+		add_action( 'set_site_transient_update_core', array( $this, 'validate_update_change' ), 10, 3 );
+
+		add_action( 'jetpack_update_plugins_change', $callable );
+		add_action( 'jetpack_update_themes_change', $callable );
+		add_action( 'jetpack_update_core_change', $callable );
+
+		add_filter(
+			'jetpack_sync_before_enqueue_jetpack_update_plugins_change',
+			array(
+				$this,
+				'filter_update_keys',
+			),
+			10,
+			2
+		);
+		add_filter(
+			'jetpack_sync_before_enqueue_upgrader_process_complete',
+			array(
+				$this,
+				'filter_upgrader_process_complete',
+			),
+			10,
+			2
+		);
+
+		add_action( 'automatic_updates_complete', $callable );
+
+		if ( is_multisite() ) {
+			add_filter( 'pre_update_site_option_wpmu_upgrade_site', array( $this, 'update_core_network_event' ), 10, 2 );
+			add_action( 'jetpack_sync_core_update_network', $callable, 10, 3 );
+		}
+
+		// Send data when update completes
+		add_action( '_core_updated_successfully', array( $this, 'update_core' ) );
+		add_action( 'jetpack_sync_core_reinstalled_successfully', $callable );
+		add_action( 'jetpack_sync_core_autoupdated_successfully', $callable, 10, 2 );
+		add_action( 'jetpack_sync_core_updated_successfully', $callable, 10, 2 );
+
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_updates', $callable );
+	}
+
+	public function init_before_send() {
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_updates', array( $this, 'expand_updates' ) );
+		add_filter( 'jetpack_sync_before_send_jetpack_update_themes_change', array( $this, 'expand_themes' ) );
+	}
+
+	public function update_core_network_event( $wp_db_version, $old_wp_db_version ) {
+		global $wp_version;
+		/**
+		 * Sync event for when core wp network updates to a new db version
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param int $wp_db_version the latest wp_db_version
+		 * @param int $old_wp_db_version previous wp_db_version
+		 * @param string $wp_version the latest wp_version
+		 */
+		do_action( 'jetpack_sync_core_update_network', $wp_db_version, $old_wp_db_version, $wp_version );
+		return $wp_db_version;
+	}
+
+	public function update_core( $new_wp_version ) {
+		global $pagenow;
+
+		if ( isset( $_GET['action'] ) && 'do-core-reinstall' === $_GET['action'] ) {
+			/**
+			 * Sync event that fires when core reinstall was successful
+			 *
+			 * @since 5.0.0
+			 *
+			 * @param string $new_wp_version the updated WordPress version
+			 */
+			do_action( 'jetpack_sync_core_reinstalled_successfully', $new_wp_version );
+			return;
+		}
+
+		// Core was autoudpated
+		if (
+			'update-core.php' !== $pagenow &&
+			! Jetpack_Constants::is_true( 'REST_API_REQUEST' ) // wp.com rest api calls should never be marked as a core autoupdate
+		) {
+			/**
+			 * Sync event that fires when core autoupdate was successful
+			 *
+			 * @since 5.0.0
+			 *
+			 * @param string $new_wp_version the updated WordPress version
+			 * @param string $old_wp_version the previous WordPress version
+			 */
+			do_action( 'jetpack_sync_core_autoupdated_successfully', $new_wp_version, $this->old_wp_version );
+			return;
+		}
+		/**
+		 * Sync event that fires when core update was successful
+		 *
+		 * @since 5.0.0
+		 *
+		 * @param string $new_wp_version the updated WordPress version
+		 * @param string $old_wp_version the previous WordPress version
+		 */
+		do_action( 'jetpack_sync_core_updated_successfully', $new_wp_version, $this->old_wp_version );
+		return;
+
+	}
+
+	public function get_update_checksum( $update, $transient ) {
+		$updates    = array();
+		$no_updated = array();
+		switch ( $transient ) {
+			case 'update_plugins':
+				if ( ! empty( $update->response ) && is_array( $update->response ) ) {
+					foreach ( $update->response as $plugin_slug => $response ) {
+						if ( ! empty( $plugin_slug ) && isset( $response->new_version ) ) {
+							$updates[] = array( $plugin_slug => $response->new_version );
+						}
+					}
+				}
+				if ( ! empty( $update->no_update ) ) {
+					$no_updated = array_keys( $update->no_update );
+				}
+
+				if ( ! isset( $no_updated['jetpack/jetpack.php'] ) && isset( $updates['jetpack/jetpack.php'] ) ) {
+					return false;
+				}
+
+				break;
+			case 'update_themes':
+				if ( ! empty( $update->response ) && is_array( $update->response ) ) {
+					foreach ( $update->response as $theme_slug => $response ) {
+						if ( ! empty( $theme_slug ) && isset( $response['new_version'] ) ) {
+							$updates[] = array( $theme_slug => $response['new_version'] );
+						}
+					}
+				}
+
+				if ( ! empty( $update->checked ) ) {
+					$no_updated = $update->checked;
+				}
+
+				break;
+			case 'update_core':
+				if ( ! empty( $update->updates ) && is_array( $update->updates ) ) {
+					foreach ( $update->updates as $response ) {
+						if ( ! empty( $response->response ) && $response->response === 'latest' ) {
+							continue;
+						}
+						if ( ! empty( $response->response ) && isset( $response->packages->full ) ) {
+							$updates[] = array( $response->response => $response->packages->full );
+						}
+					}
+				}
+
+				if ( ! empty( $update->version_checked ) ) {
+					$no_updated = $update->version_checked;
+				}
+
+				if ( empty( $updates ) ) {
+					return false;
+				}
+				break;
+
+		}
+		if ( empty( $updates ) && empty( $no_updated ) ) {
+			return false;
+		}
+		return $this->get_check_sum( array( $no_updated, $updates ) );
+	}
+
+	public function validate_update_change( $value, $expiration, $transient ) {
+		$new_checksum = $this->get_update_checksum( $value, $transient );
+
+		if ( false === $new_checksum ) {
+			return;
+		}
+
+		$checksums = get_option( self::UPDATES_CHECKSUM_OPTION_NAME, array() );
+
+		if ( isset( $checksums[ $transient ] ) && $checksums[ $transient ] === $new_checksum ) {
+			return;
+		}
+
+		$checksums[ $transient ] = $new_checksum;
+
+		update_option( self::UPDATES_CHECKSUM_OPTION_NAME, $checksums );
+		if ( 'update_core' === $transient ) {
+			/**
+			 * jetpack_update_core_change
+			 *
+			 * @since 5.1.0
+			 *
+			 * @param array containing info that tells us what needs updating
+			 */
+			do_action( 'jetpack_update_core_change', $value );
+			return;
+		}
+		if ( empty( $this->updates ) ) {
+			// lets add the shutdown method once and only when the updates move from empty to filled with something
+			add_action( 'shutdown', array( $this, 'sync_last_event' ), 9 );
+		}
+		if ( ! isset( $this->updates[ $transient ] ) ) {
+			$this->updates[ $transient ] = array();
+		}
+		$this->updates[ $transient ][] = $value;
+	}
+
+	public function sync_last_event() {
+		foreach ( $this->updates as $transient => $values ) {
+			$value = end( $values ); // only send over the last value
+			/**
+			 * jetpack_{$transient}_change
+			 * jetpack_update_plugins_change
+			 * jetpack_update_themes_change
+			 *
+			 * @since 5.1.0
+			 *
+			 * @param array containing info that tells us what needs updating
+			 */
+			do_action( "jetpack_{$transient}_change", $value );
+		}
+
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		/**
+		 * Tells the client to sync all updates to the server
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param boolean Whether to expand updates (should always be true)
+		 */
+		do_action( 'jetpack_full_sync_updates', true );
+
+		// The number of actions enqueued, and next module state (true == done)
+		return array( 1, true );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		return 1;
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_updates' );
+	}
+
+	public function get_all_updates() {
+		return array(
+			'core'    => get_site_transient( 'update_core' ),
+			'plugins' => get_site_transient( 'update_plugins' ),
+			'themes'  => get_site_transient( 'update_themes' ),
+		);
+	}
+
+	// removes unnecessary keys from synced updates data
+	function filter_update_keys( $args ) {
+		$updates = $args[0];
+
+		if ( isset( $updates->no_update ) ) {
+			unset( $updates->no_update );
+		}
+
+		return $args;
+	}
+
+	function filter_upgrader_process_complete( $args ) {
+		array_shift( $args );
+
+		return $args;
+	}
+
+	public function expand_updates( $args ) {
+		if ( $args[0] ) {
+			return $this->get_all_updates();
+		}
+
+		return $args;
+	}
+
+	public function expand_themes( $args ) {
+		if ( ! isset( $args[0], $args[0]->response ) ) {
+			return $args;
+		}
+		if ( ! is_array( $args[0]->response ) ) {
+			trigger_error( 'Warning: Not an Array as expected but -> ' . wp_json_encode( $args[0]->response ) . ' instead', E_USER_WARNING );
+			return $args;
+		}
+		foreach ( $args[0]->response as $stylesheet => &$theme_data ) {
+			$theme              = wp_get_theme( $stylesheet );
+			$theme_data['name'] = $theme->name;
+		}
+		return $args;
+	}
+
+	public function reset_data() {
+		delete_option( self::UPDATES_CHECKSUM_OPTION_NAME );
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-users.php b/plugins/jetpack/sync/class.jetpack-sync-module-users.php
new file mode 100644
index 00000000..e74d7116
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-users.php
@@ -0,0 +1,500 @@
+<?php
+
+class Jetpack_Sync_Module_Users extends Jetpack_Sync_Module {
+	const MAX_INITIAL_SYNC_USERS = 100;
+
+	protected $flags = array();
+
+	function name() {
+		return 'users';
+	}
+
+	// this is here to support the backfill API
+	public function get_object_by_id( $object_type, $id ) {
+		if ( $object_type === 'user' && $user = get_user_by( 'id', intval( $id ) ) ) {
+			return $this->sanitize_user_and_expand( $user );
+		}
+
+		return false;
+	}
+
+	public function init_listeners( $callable ) {
+
+		// users
+		add_action( 'user_register', array( $this, 'user_register_handler' ) );
+		add_action( 'profile_update', array( $this, 'save_user_handler' ), 10, 2 );
+
+		add_action( 'add_user_to_blog', array( $this, 'add_user_to_blog_handler' ) );
+		add_action( 'jetpack_sync_add_user', $callable, 10, 2 );
+
+		add_action( 'jetpack_sync_register_user', $callable, 10, 2 );
+		add_action( 'jetpack_sync_save_user', $callable, 10, 2 );
+
+		add_action( 'jetpack_sync_user_locale', $callable, 10, 2 );
+		add_action( 'jetpack_sync_user_locale_delete', $callable, 10, 1 );
+
+		add_action( 'deleted_user', array( $this, 'deleted_user_handler' ), 10, 2 );
+		add_action( 'jetpack_deleted_user', $callable, 10, 3 );
+		add_action( 'remove_user_from_blog', array( $this, 'remove_user_from_blog_handler' ), 10, 2 );
+		add_action( 'jetpack_removed_user_from_blog', $callable, 10, 2 );
+
+		// user roles
+		add_action( 'add_user_role', array( $this, 'save_user_role_handler' ), 10, 2 );
+		add_action( 'set_user_role', array( $this, 'save_user_role_handler' ), 10, 3 );
+		add_action( 'remove_user_role', array( $this, 'save_user_role_handler' ), 10, 2 );
+
+		// user capabilities
+		add_action( 'added_user_meta', array( $this, 'maybe_save_user_meta' ), 10, 4 );
+		add_action( 'updated_user_meta', array( $this, 'maybe_save_user_meta' ), 10, 4 );
+		add_action( 'deleted_user_meta', array( $this, 'maybe_save_user_meta' ), 10, 4 );
+
+		// user authentication
+		add_filter( 'authenticate', array( $this, 'authenticate_handler' ), 1000, 3 );
+		add_action( 'wp_login', array( $this, 'wp_login_handler' ), 10, 2 );
+
+		add_action( 'jetpack_wp_login', $callable, 10, 3 );
+
+		add_action( 'wp_logout', $callable, 10, 0 );
+
+		// Add on init
+		add_filter( 'jetpack_sync_before_enqueue_jetpack_sync_add_user', array( $this, 'expand_action' ) );
+		add_filter( 'jetpack_sync_before_enqueue_jetpack_sync_register_user', array( $this, 'expand_action' ) );
+		add_filter( 'jetpack_sync_before_enqueue_jetpack_sync_save_user', array( $this, 'expand_action' ) );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_users', $callable );
+	}
+
+	public function init_before_send() {
+
+		add_filter( 'jetpack_sync_before_send_jetpack_wp_login', array( $this, 'expand_login_username' ), 10, 1 );
+		add_filter( 'jetpack_sync_before_send_wp_logout', array( $this, 'expand_logout_username' ), 10, 2 );
+
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_users', array( $this, 'expand_users' ) );
+	}
+
+	private function get_user( $user ) {
+		if ( is_numeric( $user ) ) {
+			$user = get_user_by( 'id', $user );
+		}
+		if ( $user instanceof WP_User ) {
+			return $user;
+		}
+		return null;
+	}
+
+	public function sanitize_user( $user ) {
+		$user = $this->get_user( $user );
+		// this create a new user object and stops the passing of the object by reference.
+		$user = unserialize( serialize( $user ) );
+
+		if ( is_object( $user ) && is_object( $user->data ) ) {
+			unset( $user->data->user_pass );
+		}
+		return $user;
+	}
+
+	public function expand_user( $user ) {
+		if ( ! is_object( $user ) ) {
+			return null;
+		}
+		$user->allowed_mime_types = get_allowed_mime_types( $user );
+		$user->allcaps            = $this->get_real_user_capabilities( $user );
+
+		// Only set the user locale if it is different from the site local
+		if ( get_locale() !== get_user_locale( $user->ID ) ) {
+			$user->locale = get_user_locale( $user->ID );
+		}
+
+		return $user;
+	}
+
+	public function get_real_user_capabilities( $user ) {
+		$user_capabilities = array();
+		if ( is_wp_error( $user ) ) {
+			return $user_capabilities;
+		}
+		foreach ( Jetpack_Sync_Defaults::get_capabilities_whitelist() as $capability ) {
+			if ( $user_has_capabilities = user_can( $user, $capability ) ) {
+				$user_capabilities[ $capability ] = true;
+			}
+		}
+		return $user_capabilities;
+	}
+
+	public function sanitize_user_and_expand( $user ) {
+		$user = $this->get_user( $user );
+		$user = $this->expand_user( $user );
+		return $this->sanitize_user( $user );
+	}
+
+	public function expand_action( $args ) {
+		// the first argument is always the user
+		list( $user ) = $args;
+		if ( $user ) {
+			$args[0] = $this->sanitize_user_and_expand( $user );
+			return $args;
+		}
+
+		return false;
+	}
+
+	public function expand_login_username( $args ) {
+		list( $login, $user, $flags ) = $args;
+		$user                         = $this->sanitize_user( $user );
+
+		return array( $login, $user, $flags );
+	}
+
+	public function expand_logout_username( $args, $user_id ) {
+		$user = get_userdata( $user_id );
+		$user = $this->sanitize_user( $user );
+
+		$login = '';
+		if ( is_object( $user ) && is_object( $user->data ) ) {
+			$login = $user->data->user_login;
+		}
+		// if we don't have a user here lets not send anything.
+		if ( empty( $login ) ) {
+			return false;
+		}
+
+		return array( $login, $user );
+	}
+
+	/**
+	 * Additional processing is needed for wp_login so we introduce this wrapper
+	 * handler.
+	 *
+	 * @param String  $user_login the user login.
+	 * @param WP_User $user       the user object.
+	 */
+	 function wp_login_handler( $user_login, $user ) {
+		/**
+		 * Fires when a user is logged into a site.
+		 *
+		 * @since 7.2.0
+		 *
+		 * @param Numeric $user_id The user ID.
+		 * @param WP_User $user  The User Object  of the user that currently logged in
+		 * @param Array   $params Any Flags that have been added during login
+		 */
+		do_action( 'jetpack_wp_login', $user->ID, $user, $this->get_flags( $user->ID ) );
+		$this->clear_flags( $user->ID );
+	}
+
+	/**
+	 * A hook for the authenticate event that checks the password strength.
+	 *
+	 * @param WP_Error|WP_User $user     the user object, or an error.
+	 * @param String           $username the username.
+	 * @param Sting            $password the password used to authenticate.
+	 * @return WP_Error|WP_User the same object that was passed into the function.
+	 */
+	public function authenticate_handler( $user, $username, $password ) {
+		// In case of cookie authentication we don't do anything here.
+		if ( empty( $password ) ) {
+			return $user;
+		}
+
+		// We are only interested in successful authentication events.
+		if ( is_wp_error( $user ) || ! ( $user instanceof WP_User ) ) {
+			return $user;
+		}
+
+		jetpack_require_lib( 'class.jetpack-password-checker' );
+		$password_checker = new Jetpack_Password_Checker( $user->ID );
+
+		$test_results = $password_checker->test( $password, true );
+
+		// If the password passes tests, we don't do anything.
+		if ( empty( $test_results['test_results']['failed'] ) ) {
+			return $user;
+		}
+
+		$this->add_flags(
+			$user->ID,
+			array(
+				'warning'          => 'The password failed at least one strength test.',
+				'failures'         => $test_results['test_results']['failed'],
+			)
+		);
+
+		return $user;
+	}
+
+	public function deleted_user_handler( $deleted_user_id, $reassigned_user_id = '' ) {
+		$is_multisite = is_multisite();
+		/**
+		 * Fires when a user is deleted on a site
+		 *
+		 * @since 5.4.0
+		 *
+		 * @param int $deleted_user_id - ID of the deleted user
+		 * @param int $reassigned_user_id - ID of the user the deleted user's posts is reassigned to (if any)
+		 * @param bool $is_multisite - Whether this site is a multisite installation
+		 */
+		do_action( 'jetpack_deleted_user', $deleted_user_id, $reassigned_user_id, $is_multisite );
+	}
+
+	function user_register_handler( $user_id, $old_user_data = null ) {
+		// ensure we only sync users who are members of the current blog
+		if ( ! is_user_member_of_blog( $user_id, get_current_blog_id() ) ) {
+			return;
+		}
+
+		if ( Jetpack_Constants::is_true( 'JETPACK_INVITE_ACCEPTED' ) ) {
+			$this->add_flags( $user_id, array( 'invitation_accepted' => true ) );
+		}
+		/**
+		 * Fires when a new user is registered on a site
+		 *
+		 * @since 4.9.0
+		 *
+		 * @param object The WP_User object
+		 */
+		do_action( 'jetpack_sync_register_user', $user_id, $this->get_flags( $user_id ) );
+		$this->clear_flags( $user_id );
+
+	}
+
+	function add_user_to_blog_handler( $user_id, $old_user_data = null ) {
+		// ensure we only sync users who are members of the current blog
+		if ( ! is_user_member_of_blog( $user_id, get_current_blog_id() ) ) {
+			return;
+		}
+
+		if ( Jetpack_Constants::is_true( 'JETPACK_INVITE_ACCEPTED' ) ) {
+			$this->add_flags( $user_id, array( 'invitation_accepted' => true ) );
+		}
+		/**
+		 * Fires when a user is added on a site
+		 *
+		 * @since 4.9.0
+		 *
+		 * @param object The WP_User object
+		 */
+		do_action( 'jetpack_sync_add_user', $user_id, $this->get_flags( $user_id ) );
+		$this->clear_flags( $user_id );
+	}
+
+	function save_user_handler( $user_id, $old_user_data = null ) {
+		// ensure we only sync users who are members of the current blog
+		if ( ! is_user_member_of_blog( $user_id, get_current_blog_id() ) ) {
+			return;
+		}
+
+		$user = get_user_by( 'id', $user_id );
+
+		// Older versions of WP don't pass the old_user_data in ->data
+		if ( isset( $old_user_data->data ) ) {
+			$old_user = $old_user_data->data;
+		} else {
+			$old_user = $old_user_data;
+		}
+
+		if ( $old_user !== null && $user->user_pass !== $old_user->user_pass ) {
+			$this->flags[ $user_id ]['password_changed'] = true;
+		}
+		if ( $old_user !== null && $user->data->user_email !== $old_user->user_email ) {
+			// The '_new_email' user meta is deleted right after the call to wp_update_user
+			// that got us to this point so if it's still set then this was a user confirming
+			// their new email address
+			if ( 1 === intval( get_user_meta( $user->ID, '_new_email', true ) ) ) {
+				$this->flags[ $user_id ]['email_changed'] = true;
+			}
+		}
+
+		/**
+		 * Fires when the client needs to sync an updated user
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param object The WP_User object
+		 * @param array state - New since 5.8.0
+		 */
+		do_action( 'jetpack_sync_save_user', $user_id, $this->get_flags( $user_id ) );
+		$this->clear_flags( $user_id );
+	}
+
+	function save_user_role_handler( $user_id, $role, $old_roles = null ) {
+		$this->add_flags(
+			$user_id,
+			array(
+				'role_changed'  => true,
+				'previous_role' => $old_roles,
+			)
+		);
+
+		// The jetpack_sync_register_user payload is identical to jetpack_sync_save_user, don't send both
+		if ( $this->is_create_user() || $this->is_add_user_to_blog() ) {
+			return;
+		}
+		/**
+		 * This action is documented already in this file
+		 */
+		do_action( 'jetpack_sync_save_user', $user_id, $this->get_flags( $user_id ) );
+		$this->clear_flags( $user_id );
+	}
+
+	function get_flags( $user_id ) {
+		if ( isset( $this->flags[ $user_id ] ) ) {
+			return $this->flags[ $user_id ];
+		}
+		return array();
+	}
+
+	function clear_flags( $user_id ) {
+		if ( isset( $this->flags[ $user_id ] ) ) {
+			unset( $this->flags[ $user_id ] );
+		}
+	}
+
+	function add_flags( $user_id, $flags ) {
+		$this->flags[ $user_id ] = wp_parse_args( $flags, $this->get_flags( $user_id ) );
+	}
+
+	function maybe_save_user_meta( $meta_id, $user_id, $meta_key, $value ) {
+		if ( $meta_key === 'locale' ) {
+			$this->add_flags( $user_id, array( 'locale_changed' => true ) );
+		}
+
+		$user = get_user_by( 'id', $user_id );
+		if ( isset( $user->cap_key ) && $meta_key === $user->cap_key ) {
+			$this->add_flags( $user_id, array( 'capabilities_changed' => true ) );
+		}
+
+		if ( $this->is_create_user() || $this->is_add_user_to_blog() || $this->is_delete_user() ) {
+			return;
+		}
+
+		if ( isset( $this->flags[ $user_id ] ) ) {
+			/**
+			 * This action is documented already in this file
+			 */
+			do_action( 'jetpack_sync_save_user', $user_id, $this->get_flags( $user_id ) );
+		}
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		global $wpdb;
+
+		return $this->enqueue_all_ids_as_action( 'jetpack_full_sync_users', $wpdb->usermeta, 'user_id', $this->get_where_sql( $config ), $max_items_to_enqueue, $state );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		global $wpdb;
+
+		$query = "SELECT count(*) FROM $wpdb->usermeta";
+
+		if ( $where_sql = $this->get_where_sql( $config ) ) {
+			$query .= ' WHERE ' . $where_sql;
+		}
+
+		$count = $wpdb->get_var( $query );
+
+		return (int) ceil( $count / self::ARRAY_CHUNK_SIZE );
+	}
+
+	private function get_where_sql( $config ) {
+		global $wpdb;
+
+		$query = "meta_key = '{$wpdb->prefix}capabilities'";
+
+		// config is a list of user IDs to sync
+		if ( is_array( $config ) ) {
+			$query .= ' AND user_id IN (' . implode( ',', array_map( 'intval', $config ) ) . ')';
+		}
+
+		return $query;
+	}
+
+	function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_users' );
+	}
+
+	function get_initial_sync_user_config() {
+		global $wpdb;
+
+		$user_ids = $wpdb->get_col( "SELECT user_id FROM $wpdb->usermeta WHERE meta_key = '{$wpdb->prefix}user_level' AND meta_value > 0 LIMIT " . ( self::MAX_INITIAL_SYNC_USERS + 1 ) );
+
+		if ( count( $user_ids ) <= self::MAX_INITIAL_SYNC_USERS ) {
+			return $user_ids;
+		} else {
+			return false;
+		}
+	}
+
+	public function expand_users( $args ) {
+		list( $user_ids, $previous_end ) = $args;
+
+		return array(
+			'users' => array_map( array( $this, 'sanitize_user_and_expand' ), get_users(
+				array(
+					'include' => $user_ids,
+					'orderby' => 'ID',
+					'order' => 'DESC'
+				)
+			) ),
+			'previous_end' => $previous_end
+		);
+	}
+
+	public function remove_user_from_blog_handler( $user_id, $blog_id ) {
+		// User is removed on add, see https://github.com/WordPress/WordPress/blob/0401cee8b36df3def8e807dd766adc02b359dfaf/wp-includes/ms-functions.php#L2114
+		if ( $this->is_add_new_user_to_blog() ) {
+			return;
+		}
+
+		$reassigned_user_id = $this->get_reassigned_network_user_id();
+
+		// Note that we are in the context of the blog the user is removed from, see https://github.com/WordPress/WordPress/blob/473e1ba73bc5c18c72d7f288447503713d518790/wp-includes/ms-functions.php#L233
+		/**
+		 * Fires when a user is removed from a blog on a multisite installation
+		 *
+		 * @since 5.4.0
+		 *
+		 * @param int $user_id - ID of the removed user
+		 * @param int $reassigned_user_id - ID of the user the removed user's posts is reassigned to (if any)
+		 */
+		do_action( 'jetpack_removed_user_from_blog', $user_id, $reassigned_user_id );
+	}
+
+	protected function is_add_new_user_to_blog() {
+		return Jetpack::is_function_in_backtrace( 'add_new_user_to_blog' );
+	}
+
+	protected function is_add_user_to_blog() {
+		return Jetpack::is_function_in_backtrace( 'add_user_to_blog' );
+	}
+
+	protected function is_delete_user() {
+		return Jetpack::is_function_in_backtrace( array( 'wp_delete_user', 'remove_user_from_blog' ) );
+	}
+
+	protected function is_create_user() {
+		$functions = array(
+			'add_new_user_to_blog', // Used to suppress jetpack_sync_save_user in save_user_cap_handler when user registered on multi site
+			'wp_create_user', // Used to suppress jetpack_sync_save_user in save_user_role_handler when user registered on multi site
+			'wp_insert_user', // Used to suppress jetpack_sync_save_user in save_user_cap_handler and save_user_role_handler when user registered on single site
+		);
+
+		return Jetpack::is_function_in_backtrace( $functions );
+	}
+
+	protected function get_reassigned_network_user_id() {
+		$backtrace = debug_backtrace( false ); // phpcs:ignore PHPCompatibility.PHP.NewFunctionParameters.debug_backtrace_optionsFound
+		foreach ( $backtrace as $call ) {
+			if (
+				'remove_user_from_blog' === $call['function'] &&
+				3 === count( $call['args'] )
+			) {
+				return $call['args'][2];
+			}
+		}
+
+		return false;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-woocommerce.php b/plugins/jetpack/sync/class.jetpack-sync-module-woocommerce.php
new file mode 100644
index 00000000..962258a2
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-woocommerce.php
@@ -0,0 +1,335 @@
+<?php
+
+require_once JETPACK__PLUGIN_DIR . '/sync/class.jetpack-sync-module.php';
+
+class Jetpack_Sync_Module_WooCommerce extends Jetpack_Sync_Module {
+
+	private $order_item_meta_whitelist = array(
+		// https://github.com/woocommerce/woocommerce/blob/master/includes/data-stores/class-wc-order-item-product-store.php#L20
+		'_product_id',
+		'_variation_id',
+		'_qty',
+		// Tax ones also included in below class
+		// https://github.com/woocommerce/woocommerce/blob/master/includes/data-stores/class-wc-order-item-fee-data-store.php#L20
+		'_tax_class',
+		'_tax_status',
+		'_line_subtotal',
+		'_line_subtotal_tax',
+		'_line_total',
+		'_line_tax',
+		'_line_tax_data',
+		// https://github.com/woocommerce/woocommerce/blob/master/includes/data-stores/class-wc-order-item-shipping-data-store.php#L20
+		'method_id',
+		'cost',
+		'total_tax',
+		'taxes',
+		// https://github.com/woocommerce/woocommerce/blob/master/includes/data-stores/class-wc-order-item-tax-data-store.php#L20
+		'rate_id',
+		'label',
+		'compound',
+		'tax_amount',
+		'shipping_tax_amount',
+		// https://github.com/woocommerce/woocommerce/blob/master/includes/data-stores/class-wc-order-item-coupon-data-store.php
+		'discount_amount',
+		'discount_amount_tax',
+	);
+
+	private $order_item_table_name;
+
+	public function __construct() {
+		global $wpdb;
+		$this->order_item_table_name = $wpdb->prefix . 'woocommerce_order_items';
+
+		// options, constants and post meta whitelists
+		add_filter( 'jetpack_sync_options_whitelist', array( $this, 'add_woocommerce_options_whitelist' ), 10 );
+		add_filter( 'jetpack_sync_constants_whitelist', array( $this, 'add_woocommerce_constants_whitelist' ), 10 );
+		add_filter( 'jetpack_sync_post_meta_whitelist', array( $this, 'add_woocommerce_post_meta_whitelist' ), 10 );
+		add_filter( 'jetpack_sync_comment_meta_whitelist', array( $this, 'add_woocommerce_comment_meta_whitelist' ), 10 );
+
+		add_filter( 'jetpack_sync_before_enqueue_woocommerce_new_order_item', array( $this, 'filter_order_item' ) );
+		add_filter( 'jetpack_sync_before_enqueue_woocommerce_update_order_item', array( $this, 'filter_order_item' ) );
+	}
+
+	function name() {
+		return 'woocommerce';
+	}
+
+	public function init_listeners( $callable ) {
+		// attributes
+		add_action( 'woocommerce_attribute_added', $callable, 10, 2 );
+		add_action( 'woocommerce_attribute_updated', $callable, 10, 3 );
+		add_action( 'woocommerce_attribute_deleted', $callable, 10, 3 );
+
+		// orders
+		add_action( 'woocommerce_new_order', $callable, 10, 1 );
+		add_action( 'woocommerce_order_status_changed', $callable, 10, 3 );
+		add_action( 'woocommerce_payment_complete', $callable, 10, 1 );
+
+		// order items
+		add_action( 'woocommerce_new_order_item', $callable, 10, 4 );
+		add_action( 'woocommerce_update_order_item', $callable, 10, 4 );
+		add_action( 'woocommerce_delete_order_item', $callable, 10, 1 );
+		$this->init_listeners_for_meta_type( 'order_item', $callable );
+
+		// payment tokens
+		add_action( 'woocommerce_new_payment_token', $callable, 10, 1 );
+		add_action( 'woocommerce_payment_token_deleted', $callable, 10, 2 );
+		add_action( 'woocommerce_payment_token_updated', $callable, 10, 1 );
+		$this->init_listeners_for_meta_type( 'payment_token', $callable );
+
+		// product downloads
+		add_action( 'woocommerce_downloadable_product_download_log_insert', $callable, 10, 1 );
+		add_action( 'woocommerce_grant_product_download_access', $callable, 10, 1 );
+
+		// tax rates
+		add_action( 'woocommerce_tax_rate_added', $callable, 10, 2 );
+		add_action( 'woocommerce_tax_rate_updated', $callable, 10, 2 );
+		add_action( 'woocommerce_tax_rate_deleted', $callable, 10, 1 );
+
+		// webhooks
+		add_action( 'woocommerce_new_webhook', $callable, 10, 1 );
+		add_action( 'woocommerce_webhook_deleted', $callable, 10, 2 );
+		add_action( 'woocommerce_webhook_updated', $callable, 10, 1 );
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+		add_action( 'jetpack_full_sync_woocommerce_order_items', $callable ); // also sends post meta
+	}
+
+	public function get_full_sync_actions() {
+		return array( 'jetpack_full_sync_woocommerce_order_items' );
+	}
+
+	public function init_before_send() {
+		// full sync
+		add_filter( 'jetpack_sync_before_send_jetpack_full_sync_woocommerce_order_items', array( $this, 'expand_order_item_ids' ) );
+	}
+
+	public function filter_order_item( $args ) {
+		// Make sure we always have all the data - prior to WooCommerce 3.0 we only have the user supplied data in the second argument and not the full details
+		$args[1] = $this->build_order_item( $args[0] );
+		return $args;
+	}
+
+	public function expand_order_item_ids( $args ) {
+		$order_item_ids = $args[0];
+
+		global $wpdb;
+
+		$order_item_ids_sql = implode( ', ', array_map( 'intval', $order_item_ids ) );
+
+		$order_items = $wpdb->get_results(
+			"SELECT * FROM $this->order_item_table_name WHERE order_item_id IN ( $order_item_ids_sql )"
+		);
+
+		return array(
+			$order_items,
+			$this->get_metadata( $order_item_ids, 'order_item', $this->order_item_meta_whitelist ),
+		);
+	}
+
+	public function build_order_item( $order_item_id ) {
+		global $wpdb;
+		return $wpdb->get_row( $wpdb->prepare( "SELECT * FROM $this->order_item_table_name WHERE order_item_id = %d", $order_item_id ) );
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		global $wpdb;
+
+		return $this->enqueue_all_ids_as_action( 'jetpack_full_sync_woocommerce_order_items', $this->order_item_table_name, 'order_item_id', $this->get_where_sql( $config ), $max_items_to_enqueue, $state );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		global $wpdb;
+
+		$query = "SELECT count(*) FROM $this->order_item_table_name WHERE " . $this->get_where_sql( $config );
+		$count = $wpdb->get_var( $query );
+
+		return (int) ceil( $count / self::ARRAY_CHUNK_SIZE );
+	}
+
+	private function get_where_sql( $config ) {
+		return '1=1';
+	}
+
+	public function add_woocommerce_options_whitelist( $list ) {
+		return array_merge( $list, self::$wc_options_whitelist );
+	}
+
+	public function add_woocommerce_constants_whitelist( $list ) {
+		return array_merge( $list, self::$wc_constants_whitelist );
+	}
+
+	public function add_woocommerce_post_meta_whitelist( $list ) {
+		return array_merge( $list, self::$wc_post_meta_whitelist );
+	}
+
+	public function add_woocommerce_comment_meta_whitelist( $list ) {
+		return array_merge( $list, self::$wc_comment_meta_whitelist );
+	}
+
+	private static $wc_options_whitelist = array(
+		'woocommerce_currency',
+		'woocommerce_db_version',
+		'woocommerce_weight_unit',
+		'woocommerce_version',
+		'woocommerce_unforce_ssl_checkout',
+		'woocommerce_tax_total_display',
+		'woocommerce_tax_round_at_subtotal',
+		'woocommerce_tax_display_shop',
+		'woocommerce_tax_display_cart',
+		'woocommerce_prices_include_tax',
+		'woocommerce_price_thousand_sep',
+		'woocommerce_price_num_decimals',
+		'woocommerce_price_decimal_sep',
+		'woocommerce_notify_low_stock',
+		'woocommerce_notify_low_stock_amount',
+		'woocommerce_notify_no_stock',
+		'woocommerce_notify_no_stock_amount',
+		'woocommerce_manage_stock',
+		'woocommerce_force_ssl_checkout',
+		'woocommerce_hide_out_of_stock_items',
+		'woocommerce_file_download_method',
+		'woocommerce_enable_signup_and_login_from_checkout',
+		'woocommerce_enable_shipping_calc',
+		'woocommerce_enable_review_rating',
+		'woocommerce_enable_guest_checkout',
+		'woocommerce_enable_coupons',
+		'woocommerce_enable_checkout_login_reminder',
+		'woocommerce_enable_ajax_add_to_cart',
+		'woocommerce_dimension_unit',
+		'woocommerce_default_country',
+		'woocommerce_default_customer_address',
+		'woocommerce_currency_pos',
+		'woocommerce_api_enabled',
+		'woocommerce_allow_tracking',
+	);
+
+	private static $wc_constants_whitelist = array(
+		// woocommerce options
+		'WC_PLUGIN_FILE',
+		'WC_ABSPATH',
+		'WC_PLUGIN_BASENAME',
+		'WC_VERSION',
+		'WOOCOMMERCE_VERSION',
+		'WC_ROUNDING_PRECISION',
+		'WC_DISCOUNT_ROUNDING_MODE',
+		'WC_TAX_ROUNDING_MODE',
+		'WC_DELIMITER',
+		'WC_LOG_DIR',
+		'WC_SESSION_CACHE_GROUP',
+		'WC_TEMPLATE_DEBUG_MODE',
+	);
+
+	private static $wc_post_meta_whitelist = array(
+		// woocommerce products
+		// https://github.com/woocommerce/woocommerce/blob/8ed6e7436ff87c2153ed30edd83c1ab8abbdd3e9/includes/data-stores/class-wc-product-data-store-cpt.php#L21
+		'_visibility',
+		'_sku',
+		'_price',
+		'_regular_price',
+		'_sale_price',
+		'_sale_price_dates_from',
+		'_sale_price_dates_to',
+		'total_sales',
+		'_tax_status',
+		'_tax_class',
+		'_manage_stock',
+		'_backorders',
+		'_sold_individually',
+		'_weight',
+		'_length',
+		'_width',
+		'_height',
+		'_upsell_ids',
+		'_crosssell_ids',
+		'_purchase_note',
+		'_default_attributes',
+		'_product_attributes',
+		'_virtual',
+		'_downloadable',
+		'_download_limit',
+		'_download_expiry',
+		'_featured',
+		'_downloadable_files',
+		'_wc_rating_count',
+		'_wc_average_rating',
+		'_wc_review_count',
+		'_variation_description',
+		'_thumbnail_id',
+		'_file_paths',
+		'_product_image_gallery',
+		'_product_version',
+		'_wp_old_slug',
+
+		// woocommerce orders
+		// https://github.com/woocommerce/woocommerce/blob/8ed6e7436ff87c2153ed30edd83c1ab8abbdd3e9/includes/data-stores/class-wc-order-data-store-cpt.php#L27
+		'_order_key',
+		'_order_currency',
+		// '_billing_first_name', do not sync these as they contain personal data
+		// '_billing_last_name',
+		// '_billing_company',
+		// '_billing_address_1',
+		// '_billing_address_2',
+		'_billing_city',
+		'_billing_state',
+		'_billing_postcode',
+		'_billing_country',
+		// '_billing_email', do not sync these as they contain personal data
+		// '_billing_phone',
+		// '_shipping_first_name',
+		// '_shipping_last_name',
+		// '_shipping_company',
+		// '_shipping_address_1',
+		// '_shipping_address_2',
+		'_shipping_city',
+		'_shipping_state',
+		'_shipping_postcode',
+		'_shipping_country',
+		'_completed_date',
+		'_paid_date',
+		'_cart_discount',
+		'_cart_discount_tax',
+		'_order_shipping',
+		'_order_shipping_tax',
+		'_order_tax',
+		'_order_total',
+		'_payment_method',
+		'_payment_method_title',
+		// '_transaction_id', do not sync these as they contain personal data
+		// '_customer_ip_address',
+		// '_customer_user_agent',
+		'_created_via',
+		'_order_version',
+		'_prices_include_tax',
+		'_date_completed',
+		'_date_paid',
+		'_payment_tokens',
+		'_billing_address_index',
+		'_shipping_address_index',
+		'_recorded_sales',
+		'_recorded_coupon_usage_counts',
+		// https://github.com/woocommerce/woocommerce/blob/8ed6e7436ff87c2153ed30edd83c1ab8abbdd3e9/includes/data-stores/class-wc-order-data-store-cpt.php#L539
+		'_download_permissions_granted',
+		// https://github.com/woocommerce/woocommerce/blob/8ed6e7436ff87c2153ed30edd83c1ab8abbdd3e9/includes/data-stores/class-wc-order-data-store-cpt.php#L594
+		'_order_stock_reduced',
+
+		// woocommerce order refunds
+		// https://github.com/woocommerce/woocommerce/blob/b8a2815ae546c836467008739e7ff5150cb08e93/includes/data-stores/class-wc-order-refund-data-store-cpt.php#L20
+		'_order_currency',
+		'_refund_amount',
+		'_refunded_by',
+		'_refund_reason',
+		'_order_shipping',
+		'_order_shipping_tax',
+		'_order_tax',
+		'_order_total',
+		'_order_version',
+		'_prices_include_tax',
+		'_payment_tokens',
+	);
+
+	private static $wc_comment_meta_whitelist = array(
+		'rating',
+	);
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module-wp-super-cache.php b/plugins/jetpack/sync/class.jetpack-sync-module-wp-super-cache.php
new file mode 100644
index 00000000..04d6c5dd
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module-wp-super-cache.php
@@ -0,0 +1,79 @@
+<?php
+
+class Jetpack_Sync_Module_WP_Super_Cache extends Jetpack_Sync_Module {
+
+	public function __construct() {
+		add_filter( 'jetpack_sync_constants_whitelist', array( $this, 'add_wp_super_cache_constants_whitelist' ), 10 );
+		add_filter( 'jetpack_sync_callable_whitelist', array( $this, 'add_wp_super_cache_callable_whitelist' ), 10 );
+	}
+
+	static $wp_super_cache_constants = array(
+		'WPLOCKDOWN',
+		'WPSC_DISABLE_COMPRESSION',
+		'WPSC_DISABLE_LOCKING',
+		'WPSC_DISABLE_HTACCESS_UPDATE',
+		'ADVANCEDCACHEPROBLEM',
+	);
+
+	static $wp_super_cache_callables = array(
+		'wp_super_cache_globals' => array( 'Jetpack_Sync_Module_WP_Super_Cache', 'get_wp_super_cache_globals' ),
+	);
+
+	public function name() {
+		return 'wp-super-cache';
+	}
+
+	public static function get_wp_super_cache_globals() {
+		global $wp_cache_mod_rewrite;
+		global $cache_enabled;
+		global $super_cache_enabled;
+		global $ossdlcdn;
+		global $cache_rebuild_files;
+		global $wp_cache_mobile;
+		global $wp_super_cache_late_init;
+		global $wp_cache_anon_only;
+		global $wp_cache_not_logged_in;
+		global $wp_cache_clear_on_post_edit;
+		global $wp_cache_mobile_enabled;
+		global $wp_super_cache_debug;
+		global $cache_max_time;
+		global $wp_cache_refresh_single_only;
+		global $wp_cache_mfunc_enabled;
+		global $wp_supercache_304;
+		global $wp_cache_no_cache_for_get;
+		global $wp_cache_mutex_disabled;
+		global $cache_jetpack;
+		global $cache_domain_mapping;
+
+		return array(
+			'wp_cache_mod_rewrite'         => $wp_cache_mod_rewrite,
+			'cache_enabled'                => $cache_enabled,
+			'super_cache_enabled'          => $super_cache_enabled,
+			'ossdlcdn'                     => $ossdlcdn,
+			'cache_rebuild_files'          => $cache_rebuild_files,
+			'wp_cache_mobile'              => $wp_cache_mobile,
+			'wp_super_cache_late_init'     => $wp_super_cache_late_init,
+			'wp_cache_anon_only'           => $wp_cache_anon_only,
+			'wp_cache_not_logged_in'       => $wp_cache_not_logged_in,
+			'wp_cache_clear_on_post_edit'  => $wp_cache_clear_on_post_edit,
+			'wp_cache_mobile_enabled'      => $wp_cache_mobile_enabled,
+			'wp_super_cache_debug'         => $wp_super_cache_debug,
+			'cache_max_time'               => $cache_max_time,
+			'wp_cache_refresh_single_only' => $wp_cache_refresh_single_only,
+			'wp_cache_mfunc_enabled'       => $wp_cache_mfunc_enabled,
+			'wp_supercache_304'            => $wp_supercache_304,
+			'wp_cache_no_cache_for_get'    => $wp_cache_no_cache_for_get,
+			'wp_cache_mutex_disabled'      => $wp_cache_mutex_disabled,
+			'cache_jetpack'                => $cache_jetpack,
+			'cache_domain_mapping'         => $cache_domain_mapping,
+		);
+	}
+
+	public function add_wp_super_cache_constants_whitelist( $list ) {
+		return array_merge( $list, self::$wp_super_cache_constants );
+	}
+
+	public function add_wp_super_cache_callable_whitelist( $list ) {
+		return array_merge( $list, self::$wp_super_cache_callables );
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-module.php b/plugins/jetpack/sync/class.jetpack-sync-module.php
new file mode 100644
index 00000000..995e5ec3
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-module.php
@@ -0,0 +1,174 @@
+<?php
+
+/**
+ * Basic methods implemented by Jetpack Sync extensions
+ */
+abstract class Jetpack_Sync_Module {
+	const ARRAY_CHUNK_SIZE = 10;
+
+	abstract public function name();
+
+	public function get_object_by_id( $object_type, $id ) {
+		return false;
+	}
+
+	// override these to set up listeners and set/reset data/defaults
+	public function init_listeners( $callable ) {
+	}
+
+	public function init_full_sync_listeners( $callable ) {
+	}
+
+	public function init_before_send() {
+	}
+
+	public function set_defaults() {
+	}
+
+	public function reset_data() {
+	}
+
+	public function enqueue_full_sync_actions( $config, $max_items_to_enqueue, $state ) {
+		// in subclasses, return the number of actions enqueued, and next module state (true == done)
+		return array( 0, true );
+	}
+
+	public function estimate_full_sync_actions( $config ) {
+		// in subclasses, return the number of items yet to be enqueued
+		return 0;
+	}
+
+	public function get_full_sync_actions() {
+		return array();
+	}
+
+	protected function count_actions( $action_names, $actions_to_count ) {
+		return count( array_intersect( $action_names, $actions_to_count ) );
+	}
+
+	protected function get_check_sum( $values ) {
+		return crc32( wp_json_encode( jetpack_json_wrap( $values ) ) );
+	}
+
+	protected function still_valid_checksum( $sums_to_check, $name, $new_sum ) {
+		if ( isset( $sums_to_check[ $name ] ) && $sums_to_check[ $name ] === $new_sum ) {
+			return true;
+		}
+
+		return false;
+	}
+
+	protected function enqueue_all_ids_as_action( $action_name, $table_name, $id_field, $where_sql, $max_items_to_enqueue, $state ) {
+		global $wpdb;
+
+		if ( ! $where_sql ) {
+			$where_sql = '1 = 1';
+		}
+
+		$items_per_page        = 1000;
+		$page                  = 1;
+		$chunk_count           = 0;
+		$previous_interval_end = $state ? $state : '~0';
+		$listener              = Jetpack_Sync_Listener::get_instance();
+
+		// count down from max_id to min_id so we get newest posts/comments/etc first
+		while ( $ids = $wpdb->get_col( "SELECT {$id_field} FROM {$table_name} WHERE {$where_sql} AND {$id_field} < {$previous_interval_end} ORDER BY {$id_field} DESC LIMIT {$items_per_page}" ) ) {
+			// Request posts in groups of N for efficiency
+			$chunked_ids = array_chunk( $ids, self::ARRAY_CHUNK_SIZE );
+
+			// if we hit our row limit, process and return
+			if ( $chunk_count + count( $chunked_ids ) >= $max_items_to_enqueue ) {
+				$remaining_items_count = $max_items_to_enqueue - $chunk_count;
+				$remaining_items       = array_slice( $chunked_ids, 0, $remaining_items_count );
+				$remaining_items_with_previous_interval_end = $this->get_chunks_with_preceding_end( $remaining_items, $previous_interval_end );
+				$listener->bulk_enqueue_full_sync_actions( $action_name, $remaining_items_with_previous_interval_end );
+
+				$last_chunk = end( $remaining_items );
+				return array( $remaining_items_count + $chunk_count, end( $last_chunk ) );
+			}
+			$chunked_ids_with_previous_end = $this->get_chunks_with_preceding_end( $chunked_ids, $previous_interval_end );
+
+			$listener->bulk_enqueue_full_sync_actions( $action_name, $chunked_ids_with_previous_end );
+
+			$chunk_count    += count( $chunked_ids );
+			$page           += 1;
+			// $ids are ordered in descending order
+			$previous_interval_end = end( $ids );
+		}
+
+		return array( $chunk_count, true );
+	}
+
+	private function get_chunks_with_preceding_end( $chunks, $previous_interval_end ) {
+		foreach( $chunks as $chunk ) {
+			$chunks_with_ends[] = array(
+				'ids' => $chunk,
+				'previous_end' => $previous_interval_end
+			);
+			// Chunks are ordered in descending order
+			$previous_interval_end = end( $chunk );
+		}
+		return $chunks_with_ends;
+	}
+
+	protected function get_metadata( $ids, $meta_type, $meta_key_whitelist ) {
+		global $wpdb;
+		$table = _get_meta_table( $meta_type );
+		$id    = $meta_type . '_id';
+		if ( ! $table ) {
+			return array();
+		}
+
+		$private_meta_whitelist_sql = "'" . implode( "','", array_map( 'esc_sql', $meta_key_whitelist ) ) . "'";
+
+		return array_map(
+			array( $this, 'unserialize_meta' ),
+			$wpdb->get_results(
+				"SELECT $id, meta_key, meta_value, meta_id FROM $table WHERE $id IN ( " . implode( ',', wp_parse_id_list( $ids ) ) . ' )' .
+				" AND meta_key IN ( $private_meta_whitelist_sql ) ",
+				OBJECT
+			)
+		);
+	}
+
+	public function init_listeners_for_meta_type( $meta_type, $callable ) {
+		add_action( "added_{$meta_type}_meta", $callable, 10, 4 );
+		add_action( "updated_{$meta_type}_meta", $callable, 10, 4 );
+		add_action( "deleted_{$meta_type}_meta", $callable, 10, 4 );
+	}
+
+	public function init_meta_whitelist_handler( $meta_type, $whitelist_handler ) {
+		add_filter( "jetpack_sync_before_enqueue_added_{$meta_type}_meta", $whitelist_handler );
+		add_filter( "jetpack_sync_before_enqueue_updated_{$meta_type}_meta", $whitelist_handler );
+		add_filter( "jetpack_sync_before_enqueue_deleted_{$meta_type}_meta", $whitelist_handler );
+	}
+
+	protected function get_term_relationships( $ids ) {
+		global $wpdb;
+
+		return $wpdb->get_results( "SELECT object_id, term_taxonomy_id FROM $wpdb->term_relationships WHERE object_id IN ( " . implode( ',', wp_parse_id_list( $ids ) ) . ' )', OBJECT );
+	}
+
+	public function unserialize_meta( $meta ) {
+		$meta->meta_value = maybe_unserialize( $meta->meta_value );
+		return $meta;
+	}
+
+	public function get_objects_by_id( $object_type, $ids ) {
+		if ( empty( $ids ) || empty( $object_type ) ) {
+			return array();
+		}
+
+		$objects = array();
+		foreach ( (array) $ids as $id ) {
+			$object = $this->get_object_by_id( $object_type, $id );
+
+			// Only add object if we have the object.
+			if ( $object ) {
+				$objects[ $id ] = $object;
+			}
+		}
+
+		return $objects;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-modules.php b/plugins/jetpack/sync/class.jetpack-sync-modules.php
new file mode 100644
index 00000000..2450bae9
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-modules.php
@@ -0,0 +1,104 @@
+<?php
+
+/**
+ * simple wrapper that allows enumerating cached static instances
+ * of sync modules
+ */
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-posts.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-import.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-comments.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-constants.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-callables.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-options.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-network-options.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-updates.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-users.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-themes.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-menus.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-attachments.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-meta.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-terms.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-plugins.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-full-sync.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-stats.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-module-protect.php';
+
+class Jetpack_Sync_Modules {
+
+	private static $default_sync_modules = array(
+		'Jetpack_Sync_Module_Constants',
+		'Jetpack_Sync_Module_Callables',
+		'Jetpack_Sync_Module_Options',
+		'Jetpack_Sync_Module_Network_Options',
+		'Jetpack_Sync_Module_Terms',
+		'Jetpack_Sync_Module_Themes',
+		'Jetpack_Sync_Module_Menus',
+		'Jetpack_Sync_Module_Users',
+		'Jetpack_Sync_Module_Posts',
+		'Jetpack_Sync_Module_Import',
+		'Jetpack_Sync_Module_Protect',
+		'Jetpack_Sync_Module_Comments',
+		'Jetpack_Sync_Module_Updates',
+		'Jetpack_Sync_Module_Attachments',
+		'Jetpack_Sync_Module_Meta',
+		'Jetpack_Sync_Module_Plugins',
+		'Jetpack_Sync_Module_Full_Sync',
+		'Jetpack_Sync_Module_Stats',
+	);
+
+	private static $initialized_modules = null;
+
+	public static function get_modules() {
+		if ( null === self::$initialized_modules ) {
+			self::$initialized_modules = self::initialize_modules();
+		}
+
+		return self::$initialized_modules;
+	}
+
+	public static function set_defaults() {
+		foreach ( self::get_modules() as $module ) {
+			$module->set_defaults();
+		}
+	}
+
+	public static function get_module( $module_name ) {
+		foreach ( self::get_modules() as $module ) {
+			if ( $module->name() === $module_name ) {
+				return $module;
+			}
+		}
+
+		return false;
+	}
+
+	static function initialize_modules() {
+		/**
+		 * Filters the list of class names of sync modules.
+		 * If you add to this list, make sure any classes implement the
+		 * Jetpack_Sync_Module interface.
+		 *
+		 * @since 4.2.0
+		 */
+		$modules = apply_filters( 'jetpack_sync_modules', self::$default_sync_modules );
+
+		$modules = array_map( array( 'Jetpack_Sync_Modules', 'load_module' ), $modules );
+
+		return array_map( array( 'Jetpack_Sync_Modules', 'set_module_defaults' ), $modules );
+	}
+
+	static function load_module( $module_name ) {
+		return new $module_name();
+	}
+
+	static function set_module_defaults( $module ) {
+		$module->set_defaults();
+		if ( method_exists( $module, 'set_late_default' ) ) {
+			add_action( 'init', array( $module, 'set_late_default' ), 90 );
+		}
+		return $module;
+	}
+
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-queue.php b/plugins/jetpack/sync/class.jetpack-sync-queue.php
new file mode 100644
index 00000000..ae40a597
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-queue.php
@@ -0,0 +1,478 @@
+<?php
+
+/**
+ * A buffer of items from the queue that can be checked out
+ */
+class Jetpack_Sync_Queue_Buffer {
+	public $id;
+	public $items_with_ids;
+
+	public function __construct( $id, $items_with_ids ) {
+		$this->id             = $id;
+		$this->items_with_ids = $items_with_ids;
+	}
+
+	public function get_items() {
+		return array_combine( $this->get_item_ids(), $this->get_item_values() );
+	}
+
+	public function get_item_values() {
+		return Jetpack_Sync_Utils::get_item_values( $this->items_with_ids );
+	}
+
+	public function get_item_ids() {
+		return Jetpack_Sync_Utils::get_item_ids( $this->items_with_ids );
+	}
+}
+
+/**
+ * A persistent queue that can be flushed in increments of N items,
+ * and which blocks reads until checked-out buffers are checked in or
+ * closed. This uses raw SQL for two reasons: speed, and not triggering
+ * tons of added_option callbacks.
+ */
+class Jetpack_Sync_Queue {
+	public $id;
+	private $row_iterator;
+
+	function __construct( $id ) {
+		$this->id           = str_replace( '-', '_', $id ); // necessary to ensure we don't have ID collisions in the SQL
+		$this->row_iterator = 0;
+		$this->random_int   = mt_rand( 1, 1000000 );
+	}
+
+	function add( $item ) {
+		global $wpdb;
+		$added = false;
+		// this basically tries to add the option until enough time has elapsed that
+		// it has a unique (microtime-based) option key
+		while ( ! $added ) {
+			$rows_added = $wpdb->query(
+				$wpdb->prepare(
+					"INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES (%s, %s,%s)",
+					$this->get_next_data_row_option_name(),
+					serialize( $item ),
+					'no'
+				)
+			);
+			$added      = ( 0 !== $rows_added );
+		}
+	}
+
+	// Attempts to insert all the items in a single SQL query. May be subject to query size limits!
+	function add_all( $items ) {
+		global $wpdb;
+		$base_option_name = $this->get_next_data_row_option_name();
+
+		$query = "INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES ";
+
+		$rows = array();
+
+		for ( $i = 0; $i < count( $items ); $i += 1 ) {
+			$option_name  = esc_sql( $base_option_name . '-' . $i );
+			$option_value = esc_sql( serialize( $items[ $i ] ) );
+			$rows[]       = "('$option_name', '$option_value', 'no')";
+		}
+
+		$rows_added = $wpdb->query( $query . join( ',', $rows ) );
+
+		if ( count( $items ) === $rows_added ) {
+			return new WP_Error( 'row_count_mismatch', "The number of rows inserted didn't match the size of the input array" );
+		}
+	}
+
+	// Peek at the front-most item on the queue without checking it out
+	function peek( $count = 1 ) {
+		$items = $this->fetch_items( $count );
+		if ( $items ) {
+			return Jetpack_Sync_Utils::get_item_values( $items );
+		}
+
+		return array();
+	}
+
+	// lag is the difference in time between the age of the oldest item
+	// (aka first or frontmost item) and the current time
+	function lag( $now = null ) {
+		global $wpdb;
+
+		$first_item_name = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT 1",
+				"jpsq_{$this->id}-%"
+			)
+		);
+
+		if ( ! $first_item_name ) {
+			return 0;
+		}
+
+		if ( null === $now ) {
+			$now = microtime( true );
+		}
+
+		// break apart the item name to get the timestamp
+		$matches = null;
+		if ( preg_match( '/^jpsq_' . $this->id . '-(\d+\.\d+)-/', $first_item_name, $matches ) ) {
+			return $now - floatval( $matches[1] );
+		} else {
+			return 0;
+		}
+	}
+
+	function reset() {
+		global $wpdb;
+		$this->delete_checkout_id();
+		$wpdb->query(
+			$wpdb->prepare(
+				"DELETE FROM $wpdb->options WHERE option_name LIKE %s",
+				"jpsq_{$this->id}-%"
+			)
+		);
+	}
+
+	function size() {
+		global $wpdb;
+
+		return (int) $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT count(*) FROM $wpdb->options WHERE option_name LIKE %s",
+				"jpsq_{$this->id}-%"
+			)
+		);
+	}
+
+	// we use this peculiar implementation because it's much faster than count(*)
+	function has_any_items() {
+		global $wpdb;
+		$value = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT exists( SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s )",
+				"jpsq_{$this->id}-%"
+			)
+		);
+
+		return ( $value === '1' );
+	}
+
+	function checkout( $buffer_size ) {
+		if ( $this->get_checkout_id() ) {
+			return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' );
+		}
+
+		$buffer_id = uniqid();
+
+		$result = $this->set_checkout_id( $buffer_id );
+
+		if ( ! $result || is_wp_error( $result ) ) {
+			return $result;
+		}
+
+		$items = $this->fetch_items( $buffer_size );
+
+		if ( count( $items ) === 0 ) {
+			return false;
+		}
+
+		$buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, array_slice( $items, 0, $buffer_size ) );
+
+		return $buffer;
+	}
+
+	// this checks out rows until it either empties the queue or hits a certain memory limit
+	// it loads the sizes from the DB first so that it doesn't accidentally
+	// load more data into memory than it needs to.
+	// The only way it will load more items than $max_size is if a single queue item
+	// exceeds the memory limit, but in that case it will send that item by itself.
+	function checkout_with_memory_limit( $max_memory, $max_buffer_size = 500 ) {
+		if ( $this->get_checkout_id() ) {
+			return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' );
+		}
+
+		$buffer_id = uniqid();
+
+		$result = $this->set_checkout_id( $buffer_id );
+
+		if ( ! $result || is_wp_error( $result ) ) {
+			return $result;
+		}
+
+		// get the map of buffer_id -> memory_size
+		global $wpdb;
+
+		$items_with_size = $wpdb->get_results(
+			$wpdb->prepare(
+				"SELECT option_name AS id, LENGTH(option_value) AS value_size FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT %d",
+				"jpsq_{$this->id}-%",
+				$max_buffer_size
+			),
+			OBJECT
+		);
+
+		if ( count( $items_with_size ) === 0 ) {
+			return false;
+		}
+
+		$total_memory = 0;
+
+		$min_item_id = $max_item_id = $items_with_size[0]->id;
+
+		foreach ( $items_with_size as $id => $item_with_size ) {
+			$total_memory += $item_with_size->value_size;
+
+			// if this is the first item and it exceeds memory, allow loop to continue
+			// we will exit on the next iteration instead
+			if ( $total_memory > $max_memory && $id > 0 ) {
+				break;
+			}
+
+			$max_item_id = $item_with_size->id;
+		}
+
+		$query = $wpdb->prepare(
+			"SELECT option_name AS id, option_value AS value FROM $wpdb->options WHERE option_name >= %s and option_name <= %s ORDER BY option_name ASC",
+			$min_item_id,
+			$max_item_id
+		);
+
+		$items = $wpdb->get_results( $query, OBJECT );
+		foreach ( $items as $item ) {
+			$item->value = maybe_unserialize( $item->value );
+		}
+
+		if ( count( $items ) === 0 ) {
+			$this->delete_checkout_id();
+
+			return false;
+		}
+
+		$buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, $items );
+
+		return $buffer;
+	}
+
+	function checkin( $buffer ) {
+		$is_valid = $this->validate_checkout( $buffer );
+
+		if ( is_wp_error( $is_valid ) ) {
+			return $is_valid;
+		}
+
+		$this->delete_checkout_id();
+
+		return true;
+	}
+
+	function close( $buffer, $ids_to_remove = null ) {
+		$is_valid = $this->validate_checkout( $buffer );
+
+		if ( is_wp_error( $is_valid ) ) {
+			return $is_valid;
+		}
+
+		$this->delete_checkout_id();
+
+		// by default clear all items in the buffer
+		if ( is_null( $ids_to_remove ) ) {
+			$ids_to_remove = $buffer->get_item_ids();
+		}
+
+		global $wpdb;
+
+		if ( count( $ids_to_remove ) > 0 ) {
+			$sql   = "DELETE FROM $wpdb->options WHERE option_name IN (" . implode( ', ', array_fill( 0, count( $ids_to_remove ), '%s' ) ) . ')';
+			$query = call_user_func_array( array( $wpdb, 'prepare' ), array_merge( array( $sql ), $ids_to_remove ) );
+			$wpdb->query( $query );
+		}
+
+		return true;
+	}
+
+	function flush_all() {
+		$items = Jetpack_Sync_Utils::get_item_values( $this->fetch_items() );
+		$this->reset();
+
+		return $items;
+	}
+
+	function get_all() {
+		return $this->fetch_items();
+	}
+
+	// use with caution, this could allow multiple processes to delete
+	// and send from the queue at the same time
+	function force_checkin() {
+		$this->delete_checkout_id();
+	}
+
+	// used to lock checkouts from the queue.
+	// tries to wait up to $timeout seconds for the queue to be empty
+	function lock( $timeout = 30 ) {
+		$tries = 0;
+
+		while ( $this->has_any_items() && $tries < $timeout ) {
+			sleep( 1 );
+			$tries += 1;
+		}
+
+		if ( $tries === 30 ) {
+			return new WP_Error( 'lock_timeout', 'Timeout waiting for sync queue to empty' );
+		}
+
+		if ( $this->get_checkout_id() ) {
+			return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' );
+		}
+
+		// hopefully this means we can acquire a checkout?
+		$result = $this->set_checkout_id( 'lock' );
+
+		if ( ! $result || is_wp_error( $result ) ) {
+			return $result;
+		}
+
+		return true;
+	}
+
+	function unlock() {
+		return $this->delete_checkout_id();
+	}
+
+	/**
+	 * This option is specifically chosen to, as much as possible, preserve time order
+	 * and minimise the possibility of collisions between multiple processes working
+	 * at the same time.
+	 *
+	 * @return string
+	 */
+	protected function generate_option_name_timestamp() {
+		return sprintf( '%.6f', microtime( true ) );
+	}
+
+	private function get_checkout_id() {
+		global $wpdb;
+		$checkout_value = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT option_value FROM $wpdb->options WHERE option_name = %s",
+				$this->get_lock_option_name()
+			)
+		);
+
+		if ( $checkout_value ) {
+			list( $checkout_id, $timestamp ) = explode( ':', $checkout_value );
+			if ( intval( $timestamp ) > time() ) {
+				return $checkout_id;
+			}
+		}
+
+		return false;
+	}
+
+	private function set_checkout_id( $checkout_id ) {
+		global $wpdb;
+
+		$expires     = time() + Jetpack_Sync_Defaults::$default_sync_queue_lock_timeout;
+		$updated_num = $wpdb->query(
+			$wpdb->prepare(
+				"UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s",
+				"$checkout_id:$expires",
+				$this->get_lock_option_name()
+			)
+		);
+
+		if ( ! $updated_num ) {
+			$updated_num = $wpdb->query(
+				$wpdb->prepare(
+					"INSERT INTO $wpdb->options ( option_name, option_value, autoload ) VALUES ( %s, %s, 'no' )",
+					$this->get_lock_option_name(),
+					"$checkout_id:$expires"
+				)
+			);
+		}
+
+		return $updated_num;
+	}
+
+	private function delete_checkout_id() {
+		global $wpdb;
+		// rather than delete, which causes fragmentation, we update in place
+		return $wpdb->query(
+			$wpdb->prepare(
+				"UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s",
+				'0:0',
+				$this->get_lock_option_name()
+			)
+		);
+
+	}
+
+	private function get_lock_option_name() {
+		return "jpsq_{$this->id}_checkout";
+	}
+
+	private function get_next_data_row_option_name() {
+		$timestamp = $this->generate_option_name_timestamp();
+
+		// row iterator is used to avoid collisions where we're writing data waaay fast in a single process
+		if ( $this->row_iterator === PHP_INT_MAX ) {
+			$this->row_iterator = 0;
+		} else {
+			$this->row_iterator += 1;
+		}
+
+		return 'jpsq_' . $this->id . '-' . $timestamp . '-' . $this->random_int . '-' . $this->row_iterator;
+	}
+
+	private function fetch_items( $limit = null ) {
+		global $wpdb;
+
+		if ( $limit ) {
+			$query_sql = $wpdb->prepare( "SELECT option_name AS id, option_value AS value FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT %d", "jpsq_{$this->id}-%", $limit );
+		} else {
+			$query_sql = $wpdb->prepare( "SELECT option_name AS id, option_value AS value FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC", "jpsq_{$this->id}-%" );
+		}
+
+		$items = $wpdb->get_results( $query_sql, OBJECT );
+		foreach ( $items as $item ) {
+			$item->value = maybe_unserialize( $item->value );
+		}
+
+		return $items;
+	}
+
+	private function validate_checkout( $buffer ) {
+		if ( ! $buffer instanceof Jetpack_Sync_Queue_Buffer ) {
+			return new WP_Error( 'not_a_buffer', 'You must checkin an instance of Jetpack_Sync_Queue_Buffer' );
+		}
+
+		$checkout_id = $this->get_checkout_id();
+
+		if ( ! $checkout_id ) {
+			return new WP_Error( 'buffer_not_checked_out', 'There are no checked out buffers' );
+		}
+
+		if ( $checkout_id != $buffer->id ) {
+			return new WP_Error( 'buffer_mismatch', 'The buffer you checked in was not checked out' );
+		}
+
+		return true;
+	}
+}
+
+class Jetpack_Sync_Utils {
+
+	static function get_item_values( $items ) {
+		return array_map( array( __CLASS__, 'get_item_value' ), $items );
+	}
+
+	static function get_item_ids( $items ) {
+		return array_map( array( __CLASS__, 'get_item_id' ), $items );
+	}
+
+	private static function get_item_value( $item ) {
+		return $item->value;
+	}
+
+	private static function get_item_id( $item ) {
+		return $item->id;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-sender.php b/plugins/jetpack/sync/class.jetpack-sync-sender.php
new file mode 100644
index 00000000..21f91481
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-sender.php
@@ -0,0 +1,416 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-queue.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-defaults.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-json-deflate-array-codec.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-simple-codec.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-modules.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-settings.php';
+
+/**
+ * This class grabs pending actions from the queue and sends them
+ */
+class Jetpack_Sync_Sender {
+
+	const NEXT_SYNC_TIME_OPTION_NAME = 'jetpack_next_sync_time';
+	const WPCOM_ERROR_SYNC_DELAY     = 60;
+	const QUEUE_LOCKED_SYNC_DELAY    = 10;
+
+	private $dequeue_max_bytes;
+	private $upload_max_bytes;
+	private $upload_max_rows;
+	private $max_dequeue_time;
+	private $sync_wait_time;
+	private $sync_wait_threshold;
+	private $enqueue_wait_time;
+	private $sync_queue;
+	private $full_sync_queue;
+	private $codec;
+	private $old_user;
+
+	// singleton functions
+	private static $instance;
+
+	public static function get_instance() {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+
+		return self::$instance;
+	}
+
+	// this is necessary because you can't use "new" when you declare instance properties >:(
+	protected function __construct() {
+		$this->set_defaults();
+		$this->init();
+	}
+
+	private function init() {
+		add_action( 'jetpack_sync_before_send_queue_sync', array( $this, 'maybe_set_user_from_token' ), 1 );
+		add_action( 'jetpack_sync_before_send_queue_sync', array( $this, 'maybe_clear_user_from_token' ), 20 );
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$module->init_before_send();
+		}
+	}
+
+	public function maybe_set_user_from_token() {
+		$jetpack       = Jetpack::init();
+		$verified_user = $jetpack->verify_xml_rpc_signature();
+		if ( Jetpack_Constants::is_true( 'XMLRPC_REQUEST' ) &&
+			! is_wp_error( $verified_user )
+			&& $verified_user
+		) {
+			$old_user       = wp_get_current_user();
+			$this->old_user = isset( $old_user->ID ) ? $old_user->ID : 0;
+			wp_set_current_user( $verified_user['user_id'] );
+		}
+	}
+
+	public function maybe_clear_user_from_token() {
+		if ( isset( $this->old_user ) ) {
+			wp_set_current_user( $this->old_user );
+		}
+	}
+
+	public function get_next_sync_time( $queue_name ) {
+		return (float) get_option( self::NEXT_SYNC_TIME_OPTION_NAME . '_' . $queue_name, 0 );
+	}
+
+	public function set_next_sync_time( $time, $queue_name ) {
+		return update_option( self::NEXT_SYNC_TIME_OPTION_NAME . '_' . $queue_name, $time, true );
+	}
+
+	public function do_full_sync() {
+		if ( ! Jetpack_Sync_Modules::get_module( 'full-sync' ) ) {
+			return;
+		}
+		$this->continue_full_sync_enqueue();
+		return $this->do_sync_and_set_delays( $this->full_sync_queue );
+	}
+
+	private function continue_full_sync_enqueue() {
+		if ( defined( 'WP_IMPORTING' ) && WP_IMPORTING ) {
+			return false;
+		}
+
+		if ( $this->get_next_sync_time( 'full-sync-enqueue' ) > microtime( true ) ) {
+			return false;
+		}
+
+		Jetpack_Sync_Modules::get_module( 'full-sync' )->continue_enqueuing();
+
+		$this->set_next_sync_time( time() + $this->get_enqueue_wait_time(), 'full-sync-enqueue' );
+	}
+
+	public function do_sync() {
+		return $this->do_sync_and_set_delays( $this->sync_queue );
+	}
+
+	public function do_sync_and_set_delays( $queue ) {
+		// don't sync if importing
+		if ( defined( 'WP_IMPORTING' ) && WP_IMPORTING ) {
+			return new WP_Error( 'is_importing' );
+		}
+
+		// don't sync if we are throttled
+		if ( $this->get_next_sync_time( $queue->id ) > microtime( true ) ) {
+			return new WP_Error( 'sync_throttled' );
+		}
+
+		$start_time = microtime( true );
+
+		Jetpack_Sync_Settings::set_is_syncing( true );
+
+		$sync_result = $this->do_sync_for_queue( $queue );
+
+		Jetpack_Sync_Settings::set_is_syncing( false );
+
+		$exceeded_sync_wait_threshold = ( microtime( true ) - $start_time ) > (float) $this->get_sync_wait_threshold();
+
+		if ( is_wp_error( $sync_result ) ) {
+			if ( 'unclosed_buffer' === $sync_result->get_error_code() ) {
+				$this->set_next_sync_time( time() + self::QUEUE_LOCKED_SYNC_DELAY, $queue->id );
+			}
+			if ( 'wpcom_error' === $sync_result->get_error_code() ) {
+				$this->set_next_sync_time( time() + self::WPCOM_ERROR_SYNC_DELAY, $queue->id );
+			}
+		} elseif ( $exceeded_sync_wait_threshold ) {
+			// if we actually sent data and it took a while, wait before sending again
+			$this->set_next_sync_time( time() + $this->get_sync_wait_time(), $queue->id );
+		}
+
+		return $sync_result;
+	}
+
+	public function get_items_to_send( $buffer, $encode = true ) {
+		// track how long we've been processing so we can avoid request timeouts
+		$start_time    = microtime( true );
+		$upload_size   = 0;
+		$items_to_send = array();
+		$items         = $buffer->get_items();
+		// set up current screen to avoid errors rendering content
+		require_once ABSPATH . 'wp-admin/includes/class-wp-screen.php';
+		require_once ABSPATH . 'wp-admin/includes/screen.php';
+		set_current_screen( 'sync' );
+		$skipped_items_ids = array();
+		// we estimate the total encoded size as we go by encoding each item individually
+		// this is expensive, but the only way to really know :/
+		foreach ( $items as $key => $item ) {
+			// Suspending cache addition help prevent overloading in memory cache of large sites.
+			wp_suspend_cache_addition( true );
+			/**
+			 * Modify the data within an action before it is serialized and sent to the server
+			 * For example, during full sync this expands Post ID's into full Post objects,
+			 * so that we don't have to serialize the whole object into the queue.
+			 *
+			 * @since 4.2.0
+			 *
+			 * @param array The action parameters
+			 * @param int The ID of the user who triggered the action
+			 */
+			$item[1] = apply_filters( 'jetpack_sync_before_send_' . $item[0], $item[1], $item[2] );
+			wp_suspend_cache_addition( false );
+			if ( $item[1] === false ) {
+				$skipped_items_ids[] = $key;
+				continue;
+			}
+			$encoded_item = $encode ? $this->codec->encode( $item ) : $item;
+			$upload_size += strlen( $encoded_item );
+			if ( $upload_size > $this->upload_max_bytes && count( $items_to_send ) > 0 ) {
+				break;
+			}
+			$items_to_send[ $key ] = $encoded_item;
+			if ( microtime( true ) - $start_time > $this->max_dequeue_time ) {
+				break;
+			}
+		}
+
+		return array( $items_to_send, $skipped_items_ids, $items, microtime( true ) - $start_time );
+	}
+
+	private function fastcgi_finish_request() {
+		if ( function_exists( 'fastcgi_finish_request' ) && version_compare( phpversion(), '7.0.16', '>=' ) ) {
+			fastcgi_finish_request();
+		}
+	}
+
+	public function do_sync_for_queue( $queue ) {
+		do_action( 'jetpack_sync_before_send_queue_' . $queue->id );
+		if ( $queue->size() === 0 ) {
+			return new WP_Error( 'empty_queue_' . $queue->id );
+		}
+		// now that we're sure we are about to sync, try to
+		// ignore user abort so we can avoid getting into a
+		// bad state
+		if ( function_exists( 'ignore_user_abort' ) ) {
+			ignore_user_abort( true );
+		}
+
+		/* Don't make the request block till we finish, if possible. */
+		if ( Jetpack_Constants::is_true( 'REST_REQUEST' ) || Jetpack_Constants::is_true('XMLRPC_REQUEST' ) ) {
+			$this->fastcgi_finish_request();
+		}
+
+		$checkout_start_time = microtime( true );
+
+		$buffer = $queue->checkout_with_memory_limit( $this->dequeue_max_bytes, $this->upload_max_rows );
+
+		if ( ! $buffer ) {
+			// buffer has no items
+			return new WP_Error( 'empty_buffer' );
+		}
+
+		if ( is_wp_error( $buffer ) ) {
+			return $buffer;
+		}
+
+		$checkout_duration = microtime( true ) - $checkout_start_time;
+
+		list( $items_to_send, $skipped_items_ids, $items, $preprocess_duration ) = $this->get_items_to_send( $buffer, true );
+		if ( ! empty( $items_to_send ) ) {
+			/**
+			 * Fires when data is ready to send to the server.
+			 * Return false or WP_Error to abort the sync (e.g. if there's an error)
+			 * The items will be automatically re-sent later
+			 *
+			 * @since 4.2.0
+			 *
+			 * @param array $data The action buffer
+			 * @param string $codec The codec name used to encode the data
+			 * @param double $time The current time
+			 * @param string $queue The queue used to send ('sync' or 'full_sync')
+			 */
+			Jetpack_Sync_Settings::set_is_sending( true );
+			$processed_item_ids = apply_filters( 'jetpack_sync_send_data', $items_to_send, $this->codec->name(), microtime( true ), $queue->id, $checkout_duration, $preprocess_duration );
+			Jetpack_Sync_Settings::set_is_sending( false );
+		} else {
+			$processed_item_ids = $skipped_items_ids;
+			$skipped_items_ids  = array();
+		}
+
+		if ( ! $processed_item_ids || is_wp_error( $processed_item_ids ) ) {
+			$checked_in_item_ids = $queue->checkin( $buffer );
+			if ( is_wp_error( $checked_in_item_ids ) ) {
+				error_log( 'Error checking in buffer: ' . $checked_in_item_ids->get_error_message() );
+				$queue->force_checkin();
+			}
+			if ( is_wp_error( $processed_item_ids ) ) {
+				return new WP_Error( 'wpcom_error', $processed_item_ids->get_error_code() );
+			}
+			// returning a WP_Error('wpcom_error') is a sign to the caller that we should wait a while
+			// before syncing again
+			return new WP_Error( 'wpcom_error', 'jetpack_sync_send_data_false' );
+		} else {
+			// detect if the last item ID was an error
+			$had_wp_error = is_wp_error( end( $processed_item_ids ) );
+			if ( $had_wp_error ) {
+				$wp_error = array_pop( $processed_item_ids );
+			}
+			// also checkin any items that were skipped
+			if ( count( $skipped_items_ids ) > 0 ) {
+				$processed_item_ids = array_merge( $processed_item_ids, $skipped_items_ids );
+			}
+			$processed_items = array_intersect_key( $items, array_flip( $processed_item_ids ) );
+			/**
+			 * Allows us to keep track of all the actions that have been sent.
+			 * Allows us to calculate the progress of specific actions.
+			 *
+			 * @since 4.2.0
+			 *
+			 * @param array $processed_actions The actions that we send successfully.
+			 */
+			do_action( 'jetpack_sync_processed_actions', $processed_items );
+			$queue->close( $buffer, $processed_item_ids );
+			// returning a WP_Error is a sign to the caller that we should wait a while
+			// before syncing again
+			if ( $had_wp_error ) {
+				return new WP_Error( 'wpcom_error', $wp_error->get_error_code() );
+			}
+		}
+		return true;
+	}
+
+	function get_sync_queue() {
+		return $this->sync_queue;
+	}
+
+	function get_full_sync_queue() {
+		return $this->full_sync_queue;
+	}
+
+	function get_codec() {
+		return $this->codec;
+	}
+	function set_codec() {
+		if ( function_exists( 'gzinflate' ) ) {
+			$this->codec = new Jetpack_Sync_JSON_Deflate_Array_Codec();
+		} else {
+			$this->codec = new Jetpack_Sync_Simple_Codec();
+		}
+	}
+
+	function send_checksum() {
+		require_once 'class.jetpack-sync-wp-replicastore.php';
+		$store = new Jetpack_Sync_WP_Replicastore();
+		do_action( 'jetpack_sync_checksum', $store->checksum_all() );
+	}
+
+	function reset_sync_queue() {
+		$this->sync_queue->reset();
+	}
+
+	function reset_full_sync_queue() {
+		$this->full_sync_queue->reset();
+	}
+
+	function set_dequeue_max_bytes( $size ) {
+		$this->dequeue_max_bytes = $size;
+	}
+
+	// in bytes
+	function set_upload_max_bytes( $max_bytes ) {
+		$this->upload_max_bytes = $max_bytes;
+	}
+
+	// in rows
+	function set_upload_max_rows( $max_rows ) {
+		$this->upload_max_rows = $max_rows;
+	}
+
+	// in seconds
+	function set_sync_wait_time( $seconds ) {
+		$this->sync_wait_time = $seconds;
+	}
+
+	function get_sync_wait_time() {
+		return $this->sync_wait_time;
+	}
+
+	function set_enqueue_wait_time( $seconds ) {
+		$this->enqueue_wait_time = $seconds;
+	}
+
+	function get_enqueue_wait_time() {
+		return $this->enqueue_wait_time;
+	}
+
+	// in seconds
+	function set_sync_wait_threshold( $seconds ) {
+		$this->sync_wait_threshold = $seconds;
+	}
+
+	function get_sync_wait_threshold() {
+		return $this->sync_wait_threshold;
+	}
+
+	// in seconds
+	function set_max_dequeue_time( $seconds ) {
+		$this->max_dequeue_time = $seconds;
+	}
+
+
+
+	function set_defaults() {
+		$this->sync_queue      = new Jetpack_Sync_Queue( 'sync' );
+		$this->full_sync_queue = new Jetpack_Sync_Queue( 'full_sync' );
+		$this->set_codec();
+
+		// saved settings
+		Jetpack_Sync_Settings::set_importing( null );
+		$settings = Jetpack_Sync_Settings::get_settings();
+		$this->set_dequeue_max_bytes( $settings['dequeue_max_bytes'] );
+		$this->set_upload_max_bytes( $settings['upload_max_bytes'] );
+		$this->set_upload_max_rows( $settings['upload_max_rows'] );
+		$this->set_sync_wait_time( $settings['sync_wait_time'] );
+		$this->set_enqueue_wait_time( $settings['enqueue_wait_time'] );
+		$this->set_sync_wait_threshold( $settings['sync_wait_threshold'] );
+		$this->set_max_dequeue_time( Jetpack_Sync_Defaults::get_max_sync_execution_time() );
+	}
+
+	function reset_data() {
+		$this->reset_sync_queue();
+		$this->reset_full_sync_queue();
+
+		foreach ( Jetpack_Sync_Modules::get_modules() as $module ) {
+			$module->reset_data();
+		}
+
+		foreach ( array( 'sync', 'full_sync', 'full-sync-enqueue' ) as $queue_name ) {
+			delete_option( self::NEXT_SYNC_TIME_OPTION_NAME . '_' . $queue_name );
+		}
+
+		Jetpack_Sync_Settings::reset_data();
+	}
+
+	function uninstall() {
+		// Lets delete all the other fun stuff like transient and option and the sync queue
+		$this->reset_data();
+
+		// delete the full sync status
+		delete_option( 'jetpack_full_sync_status' );
+
+		// clear the sync cron.
+		wp_clear_scheduled_hook( 'jetpack_sync_cron' );
+		wp_clear_scheduled_hook( 'jetpack_sync_full_cron' );
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-server.php b/plugins/jetpack/sync/class.jetpack-sync-server.php
new file mode 100644
index 00000000..dbd9172a
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-server.php
@@ -0,0 +1,106 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-json-deflate-array-codec.php';
+
+/**
+ * Simple version of a Jetpack Sync Server - just receives arrays of events and
+ * issues them locally with the 'jetpack_sync_remote_action' action.
+ */
+class Jetpack_Sync_Server {
+	private $codec;
+	const MAX_TIME_PER_REQUEST_IN_SECONDS = 15;
+	const BLOG_LOCK_TRANSIENT_PREFIX      = 'jp_sync_req_lock_';
+	const BLOG_LOCK_TRANSIENT_EXPIRY      = 60; // seconds
+
+	// this is necessary because you can't use "new" when you declare instance properties >:(
+	function __construct() {
+		$this->codec = new Jetpack_Sync_JSON_Deflate_Array_Codec();
+	}
+
+	function set_codec( iJetpack_Sync_Codec $codec ) {
+		$this->codec = $codec;
+	}
+
+	function attempt_request_lock( $blog_id, $expiry = self::BLOG_LOCK_TRANSIENT_EXPIRY ) {
+		$transient_name = $this->get_concurrent_request_transient_name( $blog_id );
+		$locked_time    = get_site_transient( $transient_name );
+		if ( $locked_time ) {
+			return false;
+		}
+		set_site_transient( $transient_name, microtime( true ), $expiry );
+
+		return true;
+	}
+
+	private function get_concurrent_request_transient_name( $blog_id ) {
+		return self::BLOG_LOCK_TRANSIENT_PREFIX . $blog_id;
+	}
+
+	function remove_request_lock( $blog_id ) {
+		delete_site_transient( $this->get_concurrent_request_transient_name( $blog_id ) );
+	}
+
+	function receive( $data, $token = null, $sent_timestamp = null, $queue_id = null ) {
+		$start_time = microtime( true );
+		if ( ! is_array( $data ) ) {
+			return new WP_Error( 'action_decoder_error', 'Events must be an array' );
+		}
+
+		if ( $token && ! $this->attempt_request_lock( $token->blog_id ) ) {
+			/**
+			 * Fires when the server receives two concurrent requests from the same blog
+			 *
+			 * @since 4.2.0
+			 *
+			 * @param token The token object of the misbehaving site
+			 */
+			do_action( 'jetpack_sync_multi_request_fail', $token );
+
+			return new WP_Error( 'concurrent_request_error', 'There is another request running for the same blog ID' );
+		}
+
+		$events           = wp_unslash( array_map( array( $this->codec, 'decode' ), $data ) );
+		$events_processed = array();
+
+		/**
+		 * Fires when an array of actions are received from a remote Jetpack site
+		 *
+		 * @since 4.2.0
+		 *
+		 * @param array Array of actions received from the remote site
+		 */
+		do_action( 'jetpack_sync_remote_actions', $events, $token );
+
+		foreach ( $events as $key => $event ) {
+			list( $action_name, $args, $user_id, $timestamp, $silent ) = $event;
+
+			/**
+			 * Fires when an action is received from a remote Jetpack site
+			 *
+			 * @since 4.2.0
+			 *
+			 * @param string $action_name The name of the action executed on the remote site
+			 * @param array $args The arguments passed to the action
+			 * @param int $user_id The external_user_id who did the action
+			 * @param bool $silent Whether the item was created via import
+			 * @param double $timestamp Timestamp (in seconds) when the action occurred
+			 * @param double $sent_timestamp Timestamp (in seconds) when the action was transmitted
+			 * @param string $queue_id ID of the queue from which the event was sent (sync or full_sync)
+			 * @param array $token The auth token used to invoke the API
+			 */
+			do_action( 'jetpack_sync_remote_action', $action_name, $args, $user_id, $silent, $timestamp, $sent_timestamp, $queue_id, $token );
+
+			$events_processed[] = $key;
+
+			if ( microtime( true ) - $start_time > self::MAX_TIME_PER_REQUEST_IN_SECONDS ) {
+				break;
+			}
+		}
+
+		if ( $token ) {
+			$this->remove_request_lock( $token->blog_id );
+		}
+
+		return $events_processed;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-settings.php b/plugins/jetpack/sync/class.jetpack-sync-settings.php
new file mode 100644
index 00000000..e77588a8
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-settings.php
@@ -0,0 +1,215 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-defaults.php';
+
+class Jetpack_Sync_Settings {
+	const SETTINGS_OPTION_PREFIX = 'jetpack_sync_settings_';
+
+	static $valid_settings = array(
+		'dequeue_max_bytes'        => true,
+		'upload_max_bytes'         => true,
+		'upload_max_rows'          => true,
+		'sync_wait_time'           => true,
+		'sync_wait_threshold'      => true,
+		'enqueue_wait_time'        => true,
+		'max_queue_size'           => true,
+		'max_queue_lag'            => true,
+		'queue_max_writes_sec'     => true,
+		'post_types_blacklist'     => true,
+		'disable'                  => true,
+		'network_disable'          => true,
+		'render_filtered_content'  => true,
+		'post_meta_whitelist'      => true,
+		'comment_meta_whitelist'   => true,
+		'max_enqueue_full_sync'    => true,
+		'max_queue_size_full_sync' => true,
+		'sync_via_cron'            => true,
+		'cron_sync_time_limit'     => true,
+		'known_importers'          => true,
+	);
+
+	static $is_importing;
+	static $is_doing_cron;
+	static $is_syncing;
+	static $is_sending;
+
+	static $settings_cache = array(); // some settings can be expensive to compute - let's cache them
+
+	static function get_settings() {
+		$settings = array();
+		foreach ( array_keys( self::$valid_settings ) as $setting ) {
+			$settings[ $setting ] = self::get_setting( $setting );
+		}
+
+		return $settings;
+	}
+
+	// Fetches the setting. It saves it if the setting doesn't exist, so that it gets
+	// autoloaded on page load rather than re-queried every time.
+	static function get_setting( $setting ) {
+		if ( ! isset( self::$valid_settings[ $setting ] ) ) {
+			return false;
+		}
+
+		if ( isset( self::$settings_cache[ $setting ] ) ) {
+			return self::$settings_cache[ $setting ];
+		}
+
+		if ( self::is_network_setting( $setting ) ) {
+			if ( is_multisite() ) {
+				$value = get_site_option( self::SETTINGS_OPTION_PREFIX . $setting );
+			} else {
+				// On single sites just return the default setting
+				$value = Jetpack_Sync_Defaults::get_default_setting( $setting );
+				self::$settings_cache[ $setting ] = $value;
+				return $value;
+			}
+		} else {
+			$value = get_option( self::SETTINGS_OPTION_PREFIX . $setting );
+		}
+
+		if ( false === $value ) { // no default value is set.
+			$value = Jetpack_Sync_Defaults::get_default_setting( $setting );
+			if ( self::is_network_setting( $setting ) ) {
+				update_site_option( self::SETTINGS_OPTION_PREFIX . $setting, $value );
+			} else {
+				// We set one so that it gets autoloaded
+				update_option( self::SETTINGS_OPTION_PREFIX . $setting, $value, true );
+			}
+		}
+
+		if ( is_numeric( $value ) ) {
+			$value = intval( $value );
+		}
+		$default_array_value = null;
+		switch ( $setting ) {
+			case 'post_types_blacklist':
+				$default_array_value = Jetpack_Sync_Defaults::$blacklisted_post_types;
+				break;
+			case 'post_meta_whitelist':
+				$default_array_value = Jetpack_Sync_Defaults::get_post_meta_whitelist();
+				break;
+			case 'comment_meta_whitelist':
+				$default_array_value = Jetpack_Sync_Defaults::get_comment_meta_whitelist();
+				break;
+			case 'known_importers':
+				$default_array_value = Jetpack_Sync_Defaults::get_known_importers();
+				break;
+		}
+
+		if ( $default_array_value ) {
+			if ( is_array( $value ) ) {
+				$value = array_unique( array_merge( $value, $default_array_value ) );
+			} else {
+				$value = $default_array_value;
+			}
+		}
+
+		self::$settings_cache[ $setting ] = $value;
+
+		return $value;
+	}
+
+	static function update_settings( $new_settings ) {
+		$validated_settings = array_intersect_key( $new_settings, self::$valid_settings );
+		foreach ( $validated_settings as $setting => $value ) {
+
+			if ( self::is_network_setting( $setting ) ) {
+				if ( is_multisite() && is_main_site() ) {
+					update_site_option( self::SETTINGS_OPTION_PREFIX . $setting, $value );
+				}
+			} else {
+				update_option( self::SETTINGS_OPTION_PREFIX . $setting, $value, true );
+			}
+
+			unset( self::$settings_cache[ $setting ] );
+
+			// if we set the disabled option to true, clear the queues
+			if ( ( 'disable' === $setting || 'network_disable' === $setting ) && ! ! $value ) {
+				require_once dirname( __FILE__ ) . '/class.jetpack-sync-listener.php';
+				$listener = Jetpack_Sync_Listener::get_instance();
+				$listener->get_sync_queue()->reset();
+				$listener->get_full_sync_queue()->reset();
+			}
+		}
+	}
+
+	static function is_network_setting( $setting ) {
+		return strpos( $setting, 'network_' ) === 0;
+	}
+
+	// returns escapted SQL that can be injected into a WHERE clause
+	static function get_blacklisted_post_types_sql() {
+		return 'post_type NOT IN (\'' . join( '\', \'', array_map( 'esc_sql', self::get_setting( 'post_types_blacklist' ) ) ) . '\')';
+	}
+
+	static function get_whitelisted_post_meta_sql() {
+		return 'meta_key IN (\'' . join( '\', \'', array_map( 'esc_sql', self::get_setting( 'post_meta_whitelist' ) ) ) . '\')';
+	}
+
+	static function get_whitelisted_comment_meta_sql() {
+		return 'meta_key IN (\'' . join( '\', \'', array_map( 'esc_sql', self::get_setting( 'comment_meta_whitelist' ) ) ) . '\')';
+	}
+
+	static function get_comments_filter_sql() {
+		return "comment_approved <> 'spam'";
+	}
+
+	static function reset_data() {
+		$valid_settings       = self::$valid_settings;
+		self::$settings_cache = array();
+		foreach ( $valid_settings as $option => $value ) {
+			delete_option( self::SETTINGS_OPTION_PREFIX . $option );
+		}
+		self::set_importing( null );
+		self::set_doing_cron( null );
+		self::set_is_syncing( null );
+		self::set_is_sending( null );
+	}
+
+	static function set_importing( $is_importing ) {
+		// set to NULL to revert to WP_IMPORTING, the standard behavior
+		self::$is_importing = $is_importing;
+	}
+
+	static function is_importing() {
+		if ( ! is_null( self::$is_importing ) ) {
+			return self::$is_importing;
+		}
+
+		return defined( 'WP_IMPORTING' ) && WP_IMPORTING;
+	}
+
+	static function is_sync_enabled() {
+		return ! ( self::get_setting( 'disable' ) || self::get_setting( 'network_disable' ) );
+	}
+
+	static function set_doing_cron( $is_doing_cron ) {
+		// set to NULL to revert to WP_IMPORTING, the standard behavior
+		self::$is_doing_cron = $is_doing_cron;
+	}
+
+	static function is_doing_cron() {
+		if ( ! is_null( self::$is_doing_cron ) ) {
+			return self::$is_doing_cron;
+		}
+
+		return defined( 'DOING_CRON' ) && DOING_CRON;
+	}
+
+	static function is_syncing() {
+		return (bool) self::$is_syncing || ( defined( 'REST_API_REQUEST' ) && REST_API_REQUEST );
+	}
+
+	static function set_is_syncing( $is_syncing ) {
+		self::$is_syncing = $is_syncing;
+	}
+
+	static function is_sending() {
+		return (bool) self::$is_sending;
+	}
+
+	static function set_is_sending( $is_sending ) {
+		self::$is_sending = $is_sending;
+	}
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-simple-codec.php b/plugins/jetpack/sync/class.jetpack-sync-simple-codec.php
new file mode 100644
index 00000000..7bd9aaac
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-simple-codec.php
@@ -0,0 +1,24 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-json-deflate-array-codec.php';
+
+/**
+ * An implementation of iJetpack_Sync_Codec that uses gzip's DEFLATE
+ * algorithm to compress objects serialized using json_encode
+ */
+class Jetpack_Sync_Simple_Codec extends Jetpack_Sync_JSON_Deflate_Array_Codec {
+	const CODEC_NAME = 'simple';
+
+	public function name() {
+		return self::CODEC_NAME;
+	}
+
+	public function encode( $object ) {
+		return base64_encode( $this->json_serialize( $object ) );
+	}
+
+	public function decode( $input ) {
+		return $this->json_unserialize( base64_decode( $input ) );
+	}
+
+}
diff --git a/plugins/jetpack/sync/class.jetpack-sync-users.php b/plugins/jetpack/sync/class.jetpack-sync-users.php
new file mode 100644
index 00000000..de032e2d
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-users.php
@@ -0,0 +1,81 @@
+<?php
+
+/**
+ * Class Jetpack_Sync_Users
+ *
+ * Responsible for syncing user data changes.
+ */
+class Jetpack_Sync_Users {
+	static $user_roles = array();
+
+	static function init() {
+		if ( Jetpack::is_active() ) {
+			// Kick off synchronization of user role when it changes
+			add_action( 'set_user_role', array( __CLASS__, 'user_role_change' ) );
+		}
+	}
+
+	/**
+	 * Synchronize connected user role changes
+	 */
+	static function user_role_change( $user_id ) {
+		if ( Jetpack::is_user_connected( $user_id ) ) {
+			self::update_role_on_com( $user_id );
+			// try to choose a new master if we're demoting the current one
+			self::maybe_demote_master_user( $user_id );
+		}
+	}
+
+	static function get_role( $user_id ) {
+		if ( isset( self::$user_roles[ $user_id ] ) ) {
+			return self::$user_roles[ $user_id ];
+		}
+
+		$current_user_id = get_current_user_id();
+		wp_set_current_user( $user_id );
+		$role = Jetpack::translate_current_user_to_role();
+		wp_set_current_user( $current_user_id );
+		$user_roles[ $user_id ] = $role;
+
+		return $role;
+	}
+
+	static function get_signed_role( $user_id ) {
+		return Jetpack::sign_role( self::get_role( $user_id ), $user_id );
+	}
+
+	static function update_role_on_com( $user_id ) {
+		$signed_role = self::get_signed_role( $user_id );
+		Jetpack::xmlrpc_async_call( 'jetpack.updateRole', $user_id, $signed_role );
+	}
+
+	static function maybe_demote_master_user( $user_id ) {
+		$master_user_id = Jetpack_Options::get_option( 'master_user' );
+		$role           = self::get_role( $user_id );
+		if ( $user_id == $master_user_id && 'administrator' != $role ) {
+			$query      = new WP_User_Query(
+				array(
+					'fields'  => array( 'id' ),
+					'role'    => 'administrator',
+					'orderby' => 'id',
+					'exclude' => array( $master_user_id ),
+				)
+			);
+			$new_master = false;
+			foreach ( $query->results as $result ) {
+				$found_user_id = absint( $result->id );
+				if ( $found_user_id && Jetpack::is_user_connected( $found_user_id ) ) {
+					$new_master = $found_user_id;
+					break;
+				}
+			}
+
+			if ( $new_master ) {
+				Jetpack_Options::update_option( 'master_user', $new_master );
+			}
+			// else disconnect..?
+		}
+	}
+}
+
+Jetpack_Sync_Users::init();
diff --git a/plugins/jetpack/sync/class.jetpack-sync-wp-replicastore.php b/plugins/jetpack/sync/class.jetpack-sync-wp-replicastore.php
new file mode 100644
index 00000000..99826bd0
--- /dev/null
+++ b/plugins/jetpack/sync/class.jetpack-sync-wp-replicastore.php
@@ -0,0 +1,820 @@
+<?php
+
+require_once dirname( __FILE__ ) . '/interface.jetpack-sync-replicastore.php';
+require_once dirname( __FILE__ ) . '/class.jetpack-sync-defaults.php';
+
+/**
+ * An implementation of iJetpack_Sync_Replicastore which returns data stored in a WordPress.org DB.
+ * This is useful to compare values in the local WP DB to values in the synced replica store
+ */
+class Jetpack_Sync_WP_Replicastore implements iJetpack_Sync_Replicastore {
+
+
+	public function reset() {
+		global $wpdb;
+
+		$wpdb->query( "DELETE FROM $wpdb->posts" );
+		$wpdb->query( "DELETE FROM $wpdb->comments" );
+
+		// also need to delete terms from cache
+		$term_ids = $wpdb->get_col( "SELECT term_id FROM $wpdb->terms" );
+		foreach ( $term_ids as $term_id ) {
+			wp_cache_delete( $term_id, 'terms' );
+		}
+
+		$wpdb->query( "DELETE FROM $wpdb->terms" );
+
+		$wpdb->query( "DELETE FROM $wpdb->term_taxonomy" );
+		$wpdb->query( "DELETE FROM $wpdb->term_relationships" );
+
+		// callables and constants
+		$wpdb->query( "DELETE FROM $wpdb->options WHERE option_name LIKE 'jetpack_%'" );
+		$wpdb->query( "DELETE FROM $wpdb->postmeta WHERE meta_key NOT LIKE '\_%'" );
+	}
+
+	function full_sync_start( $config ) {
+		$this->reset();
+	}
+
+	function full_sync_end( $checksum ) {
+		// noop right now
+	}
+
+	public function post_count( $status = null, $min_id = null, $max_id = null ) {
+		global $wpdb;
+
+		$where = '';
+
+		if ( $status ) {
+			$where = "post_status = '" . esc_sql( $status ) . "'";
+		} else {
+			$where = '1=1';
+		}
+
+		if ( null != $min_id ) {
+			$where .= ' AND ID >= ' . intval( $min_id );
+		}
+
+		if ( null != $max_id ) {
+			$where .= ' AND ID <= ' . intval( $max_id );
+		}
+
+		return $wpdb->get_var( "SELECT COUNT(*) FROM $wpdb->posts WHERE $where" );
+	}
+
+	// TODO: actually use max_id/min_id
+	public function get_posts( $status = null, $min_id = null, $max_id = null ) {
+		$args = array(
+			'orderby'        => 'ID',
+			'posts_per_page' => -1,
+		);
+
+		if ( $status ) {
+			$args['post_status'] = $status;
+		} else {
+			$args['post_status'] = 'any';
+		}
+
+		return get_posts( $args );
+	}
+
+	public function get_post( $id ) {
+		return get_post( $id );
+	}
+
+	public function upsert_post( $post, $silent = false ) {
+		global $wpdb;
+
+		// reject the post if it's not a WP_Post
+		if ( ! $post instanceof WP_Post ) {
+			return;
+		}
+
+		$post = $post->to_array();
+
+		// reject posts without an ID
+		if ( ! isset( $post['ID'] ) ) {
+			return;
+		}
+
+		$now     = current_time( 'mysql' );
+		$now_gmt = get_gmt_from_date( $now );
+
+		$defaults = array(
+			'ID'                    => 0,
+			'post_author'           => '0',
+			'post_content'          => '',
+			'post_content_filtered' => '',
+			'post_title'            => '',
+			'post_name'             => '',
+			'post_excerpt'          => '',
+			'post_status'           => 'draft',
+			'post_type'             => 'post',
+			'comment_status'        => 'closed',
+			'comment_count'         => '0',
+			'ping_status'           => '',
+			'post_password'         => '',
+			'to_ping'               => '',
+			'pinged'                => '',
+			'post_parent'           => 0,
+			'menu_order'            => 0,
+			'guid'                  => '',
+			'post_date'             => $now,
+			'post_date_gmt'         => $now_gmt,
+			'post_modified'         => $now,
+			'post_modified_gmt'     => $now_gmt,
+		);
+
+		$post = array_intersect_key( $post, $defaults );
+
+		$post = sanitize_post( $post, 'db' );
+
+		unset( $post['filter'] );
+
+		$exists = $wpdb->get_var( $wpdb->prepare( "SELECT EXISTS( SELECT 1 FROM $wpdb->posts WHERE ID = %d )", $post['ID'] ) );
+
+		if ( $exists ) {
+			$wpdb->update( $wpdb->posts, $post, array( 'ID' => $post['ID'] ) );
+		} else {
+			$wpdb->insert( $wpdb->posts, $post );
+		}
+
+		clean_post_cache( $post['ID'] );
+	}
+
+	public function delete_post( $post_id ) {
+		wp_delete_post( $post_id, true );
+	}
+
+	public function posts_checksum( $min_id = null, $max_id = null ) {
+		global $wpdb;
+		return $this->table_checksum( $wpdb->posts, Jetpack_Sync_Defaults::$default_post_checksum_columns, 'ID', Jetpack_Sync_Settings::get_blacklisted_post_types_sql(), $min_id, $max_id );
+	}
+
+	public function post_meta_checksum( $min_id = null, $max_id = null ) {
+		global $wpdb;
+		return $this->table_checksum( $wpdb->postmeta, Jetpack_Sync_Defaults::$default_post_meta_checksum_columns, 'meta_id', Jetpack_Sync_Settings::get_whitelisted_post_meta_sql(), $min_id, $max_id );
+	}
+
+	public function comment_count( $status = null, $min_id = null, $max_id = null ) {
+		global $wpdb;
+
+		$comment_approved = $this->comment_status_to_approval_value( $status );
+
+		if ( $comment_approved !== false ) {
+			$where = "comment_approved = '" . esc_sql( $comment_approved ) . "'";
+		} else {
+			$where = '1=1';
+		}
+
+		if ( $min_id != null ) {
+			$where .= ' AND comment_ID >= ' . intval( $min_id );
+		}
+
+		if ( $max_id != null ) {
+			$where .= ' AND comment_ID <= ' . intval( $max_id );
+		}
+
+		return $wpdb->get_var( "SELECT COUNT(*) FROM $wpdb->comments WHERE $where" );
+	}
+
+	private function comment_status_to_approval_value( $status ) {
+		switch ( $status ) {
+			case 'approve':
+				return '1';
+			case 'hold':
+				return '0';
+			case 'spam':
+				return 'spam';
+			case 'trash':
+				return 'trash';
+			case 'any':
+				return false;
+			case 'all':
+				return false;
+			default:
+				return false;
+		}
+	}
+
+	// TODO: actually use max_id/min_id
+	public function get_comments( $status = null, $min_id = null, $max_id = null ) {
+		$args = array(
+			'orderby' => 'ID',
+			'status'  => 'all',
+		);
+
+		if ( $status ) {
+			$args['status'] = $status;
+		}
+
+		return get_comments( $args );
+	}
+
+	public function get_comment( $id ) {
+		return WP_Comment::get_instance( $id );
+	}
+
+	public function upsert_comment( $comment ) {
+		global $wpdb;
+
+		$comment = $comment->to_array();
+
+		// filter by fields on comment table
+		$comment_fields_whitelist = array(
+			'comment_ID',
+			'comment_post_ID',
+			'comment_author',
+			'comment_author_email',
+			'comment_author_url',
+			'comment_author_IP',
+			'comment_date',
+			'comment_date_gmt',
+			'comment_content',
+			'comment_karma',
+			'comment_approved',
+			'comment_agent',
+			'comment_type',
+			'comment_parent',
+			'user_id',
+		);
+
+		foreach ( $comment as $key => $value ) {
+			if ( ! in_array( $key, $comment_fields_whitelist ) ) {
+				unset( $comment[ $key ] );
+			}
+		}
+
+		$exists = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT EXISTS( SELECT 1 FROM $wpdb->comments WHERE comment_ID = %d )",
+				$comment['comment_ID']
+			)
+		);
+
+		if ( $exists ) {
+			$wpdb->update( $wpdb->comments, $comment, array( 'comment_ID' => $comment['comment_ID'] ) );
+		} else {
+			$wpdb->insert( $wpdb->comments, $comment );
+		}
+
+		wp_update_comment_count( $comment['comment_post_ID'] );
+	}
+
+	public function trash_comment( $comment_id ) {
+		wp_delete_comment( $comment_id );
+	}
+
+	public function delete_comment( $comment_id ) {
+		wp_delete_comment( $comment_id, true );
+	}
+
+	public function spam_comment( $comment_id ) {
+		wp_spam_comment( $comment_id );
+	}
+
+	public function trashed_post_comments( $post_id, $statuses ) {
+		wp_trash_post_comments( $post_id );
+	}
+
+	public function untrashed_post_comments( $post_id ) {
+		wp_untrash_post_comments( $post_id );
+	}
+
+	public function comments_checksum( $min_id = null, $max_id = null ) {
+		global $wpdb;
+		return $this->table_checksum( $wpdb->comments, Jetpack_Sync_Defaults::$default_comment_checksum_columns, 'comment_ID', Jetpack_Sync_Settings::get_comments_filter_sql(), $min_id, $max_id );
+	}
+
+	public function comment_meta_checksum( $min_id = null, $max_id = null ) {
+		global $wpdb;
+		return $this->table_checksum( $wpdb->commentmeta, Jetpack_Sync_Defaults::$default_comment_meta_checksum_columns, 'meta_id', Jetpack_Sync_Settings::get_whitelisted_comment_meta_sql(), $min_id, $max_id );
+	}
+
+	public function options_checksum() {
+		global $wpdb;
+
+		$options_whitelist = "'" . implode( "', '", Jetpack_Sync_Defaults::$default_options_whitelist ) . "'";
+		$where_sql         = "option_name IN ( $options_whitelist )";
+
+		return $this->table_checksum( $wpdb->options, Jetpack_Sync_Defaults::$default_option_checksum_columns, null, $where_sql, null, null );
+	}
+
+
+	public function update_option( $option, $value ) {
+		return update_option( $option, $value );
+	}
+
+	public function get_option( $option, $default = false ) {
+		return get_option( $option, $default );
+	}
+
+	public function delete_option( $option ) {
+		return delete_option( $option );
+	}
+
+	public function set_theme_support( $theme_support ) {
+		// noop
+	}
+
+	public function current_theme_supports( $feature ) {
+		return current_theme_supports( $feature );
+	}
+
+	public function get_metadata( $type, $object_id, $meta_key = '', $single = false ) {
+		return get_metadata( $type, $object_id, $meta_key, $single );
+	}
+
+	/**
+	 *
+	 * Stores remote meta key/values alongside an ID mapping key
+	 *
+	 * @param $type
+	 * @param $object_id
+	 * @param $meta_key
+	 * @param $meta_value
+	 * @param $meta_id
+	 *
+	 * @return bool
+	 */
+	public function upsert_metadata( $type, $object_id, $meta_key, $meta_value, $meta_id ) {
+
+		$table = _get_meta_table( $type );
+		if ( ! $table ) {
+			return false;
+		}
+
+		global $wpdb;
+
+		$exists = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT EXISTS( SELECT 1 FROM $table WHERE meta_id = %d )",
+				$meta_id
+			)
+		);
+
+		if ( $exists ) {
+			$wpdb->update(
+				$table,
+				array(
+					'meta_key'   => $meta_key,
+					'meta_value' => maybe_serialize( $meta_value ),
+				),
+				array( 'meta_id' => $meta_id )
+			);
+		} else {
+			$object_id_field = $type . '_id';
+			$wpdb->insert(
+				$table,
+				array(
+					'meta_id'        => $meta_id,
+					$object_id_field => $object_id,
+					'meta_key'       => $meta_key,
+					'meta_value'     => maybe_serialize( $meta_value ),
+				)
+			);
+		}
+
+		wp_cache_delete( $object_id, $type . '_meta' );
+
+		return true;
+	}
+
+	public function delete_metadata( $type, $object_id, $meta_ids ) {
+		global $wpdb;
+
+		$table = _get_meta_table( $type );
+		if ( ! $table ) {
+			return false;
+		}
+
+		foreach ( $meta_ids as $meta_id ) {
+			$wpdb->query( $wpdb->prepare( "DELETE FROM $table WHERE meta_id = %d", $meta_id ) );
+		}
+
+		// if we don't have an object ID what do we do - invalidate ALL meta?
+		if ( $object_id ) {
+			wp_cache_delete( $object_id, $type . '_meta' );
+		}
+	}
+
+	// todo: test this out to make sure it works as expected.
+	public function delete_batch_metadata( $type, $object_ids, $meta_key ) {
+		global $wpdb;
+
+		$table = _get_meta_table( $type );
+		if ( ! $table ) {
+			return false;
+		}
+		$column = sanitize_key( $type . '_id' );
+		$wpdb->query( $wpdb->prepare( "DELETE FROM $table WHERE $column IN (%s) && meta_key = %s", implode( ',', $object_ids ), $meta_key ) );
+
+		// if we don't have an object ID what do we do - invalidate ALL meta?
+		foreach ( $object_ids as $object_id ) {
+			wp_cache_delete( $object_id, $type . '_meta' );
+		}
+	}
+
+	// constants
+	public function get_constant( $constant ) {
+		$value = get_option( 'jetpack_constant_' . $constant );
+
+		if ( $value ) {
+			return $value;
+		}
+
+		return null;
+	}
+
+	public function set_constant( $constant, $value ) {
+		update_option( 'jetpack_constant_' . $constant, $value );
+	}
+
+	public function get_updates( $type ) {
+		$all_updates = get_option( 'jetpack_updates', array() );
+
+		if ( isset( $all_updates[ $type ] ) ) {
+			return $all_updates[ $type ];
+		} else {
+			return null;
+		}
+	}
+
+	public function set_updates( $type, $updates ) {
+		$all_updates          = get_option( 'jetpack_updates', array() );
+		$all_updates[ $type ] = $updates;
+		update_option( 'jetpack_updates', $all_updates );
+	}
+
+	// functions
+	public function get_callable( $name ) {
+		$value = get_option( 'jetpack_' . $name );
+
+		if ( $value ) {
+			return $value;
+		}
+
+		return null;
+	}
+
+	public function set_callable( $name, $value ) {
+		update_option( 'jetpack_' . $name, $value );
+	}
+
+	// network options
+	public function get_site_option( $option ) {
+		return get_option( 'jetpack_network_' . $option );
+	}
+
+	public function update_site_option( $option, $value ) {
+		return update_option( 'jetpack_network_' . $option, $value );
+	}
+
+	public function delete_site_option( $option ) {
+		return delete_option( 'jetpack_network_' . $option );
+	}
+
+	// terms
+	// terms
+	public function get_terms( $taxonomy ) {
+		return get_terms( $taxonomy );
+	}
+
+	public function get_term( $taxonomy, $term_id, $is_term_id = true ) {
+		$t = $this->ensure_taxonomy( $taxonomy );
+		if ( ! $t || is_wp_error( $t ) ) {
+			return $t;
+		}
+
+		return get_term( $term_id, $taxonomy );
+	}
+
+	private function ensure_taxonomy( $taxonomy ) {
+		if ( ! taxonomy_exists( $taxonomy ) ) {
+			// try re-registering synced taxonomies
+			$taxonomies = $this->get_callable( 'taxonomies' );
+			if ( ! isset( $taxonomies[ $taxonomy ] ) ) {
+				// doesn't exist, or somehow hasn't been synced
+				return new WP_Error( 'invalid_taxonomy', "The taxonomy '$taxonomy' doesn't exist" );
+			}
+			$t = $taxonomies[ $taxonomy ];
+
+			return register_taxonomy(
+				$taxonomy,
+				$t->object_type,
+				(array) $t
+			);
+		}
+
+		return true;
+	}
+
+	public function get_the_terms( $object_id, $taxonomy ) {
+		return get_the_terms( $object_id, $taxonomy );
+	}
+
+	public function update_term( $term_object ) {
+		$taxonomy = $term_object->taxonomy;
+		global $wpdb;
+		$exists = $wpdb->get_var(
+			$wpdb->prepare(
+				"SELECT EXISTS( SELECT 1 FROM $wpdb->terms WHERE term_id = %d )",
+				$term_object->term_id
+			)
+		);
+		if ( ! $exists ) {
+			$term_object   = sanitize_term( clone( $term_object ), $taxonomy, 'db' );
+			$term          = array(
+				'term_id'    => $term_object->term_id,
+				'name'       => $term_object->name,
+				'slug'       => $term_object->slug,
+				'term_group' => $term_object->term_group,
+			);
+			$term_taxonomy = array(
+				'term_taxonomy_id' => $term_object->term_taxonomy_id,
+				'term_id'          => $term_object->term_id,
+				'taxonomy'         => $term_object->taxonomy,
+				'description'      => $term_object->description,
+				'parent'           => (int) $term_object->parent,
+				'count'            => (int) $term_object->count,
+			);
+			$wpdb->insert( $wpdb->terms, $term );
+			$wpdb->insert( $wpdb->term_taxonomy, $term_taxonomy );
+
+			return true;
+		}
+
+		return wp_update_term( $term_object->term_id, $taxonomy, (array) $term_object );
+	}
+
+	public function delete_term( $term_id, $taxonomy ) {
+		return wp_delete_term( $term_id, $taxonomy );
+	}
+
+	public function update_object_terms( $object_id, $taxonomy, $terms, $append ) {
+		wp_set_object_terms( $object_id, $terms, $taxonomy, $append );
+	}
+
+	public function delete_object_terms( $object_id, $tt_ids ) {
+		global $wpdb;
+
+		if ( is_array( $tt_ids ) && ! empty( $tt_ids ) ) {
+			// escape
+			$tt_ids_sanitized = array_map( 'intval', $tt_ids );
+
+			$taxonomies = array();
+			foreach ( $tt_ids_sanitized as $tt_id ) {
+				$term                            = get_term_by( 'term_taxonomy_id', $tt_id );
+				$taxonomies[ $term->taxonomy ][] = $tt_id;
+			}
+			$in_tt_ids = implode( ', ', $tt_ids_sanitized );
+
+			/**
+			 * Fires immediately before an object-term relationship is deleted.
+			 *
+			 * @since 2.9.0
+			 *
+			 * @param int $object_id Object ID.
+			 * @param array $tt_ids An array of term taxonomy IDs.
+			 */
+			do_action( 'delete_term_relationships', $object_id, $tt_ids_sanitized );
+			$deleted = $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->term_relationships WHERE object_id = %d AND term_taxonomy_id IN ($in_tt_ids)", $object_id ) );
+			foreach ( $taxonomies as $taxonomy => $taxonomy_tt_ids ) {
+				$this->ensure_taxonomy( $taxonomy );
+				wp_cache_delete( $object_id, $taxonomy . '_relationships' );
+				/**
+				 * Fires immediately after an object-term relationship is deleted.
+				 *
+				 * @since 2.9.0
+				 *
+				 * @param int $object_id Object ID.
+				 * @param array $tt_ids An array of term taxonomy IDs.
+				 */
+				do_action( 'deleted_term_relationships', $object_id, $taxonomy_tt_ids );
+				wp_update_term_count( $taxonomy_tt_ids, $taxonomy );
+			}
+
+			return (bool) $deleted;
+		}
+
+		return false;
+	}
+
+	// users
+	public function user_count() {
+
+	}
+
+	public function get_user( $user_id ) {
+		return WP_User::get_instance( $user_id );
+	}
+
+	public function upsert_user( $user ) {
+		$this->invalid_call();
+	}
+
+	public function delete_user( $user_id ) {
+		$this->invalid_call();
+	}
+
+	public function upsert_user_locale( $user_id, $local ) {
+		$this->invalid_call();
+	}
+
+	public function delete_user_locale( $user_id ) {
+		$this->invalid_call();
+	}
+
+	public function get_user_locale( $user_id ) {
+		return get_user_locale( $user_id );
+	}
+
+	public function get_allowed_mime_types( $user_id ) {
+
+	}
+
+	public function checksum_all() {
+		$post_meta_checksum    = $this->checksum_histogram( 'post_meta', 1 );
+		$comment_meta_checksum = $this->checksum_histogram( 'comment_meta', 1 );
+
+		return array(
+			'posts'        => $this->posts_checksum(),
+			'comments'     => $this->comments_checksum(),
+			'post_meta'    => reset( $post_meta_checksum ),
+			'comment_meta' => reset( $comment_meta_checksum ),
+		);
+	}
+
+	function checksum_histogram( $object_type, $buckets, $start_id = null, $end_id = null, $columns = null, $strip_non_ascii = true, $salt = '' ) {
+		global $wpdb;
+
+		$wpdb->queries = array();
+
+		switch ( $object_type ) {
+			case 'posts':
+				$object_count = $this->post_count( null, $start_id, $end_id );
+				$object_table = $wpdb->posts;
+				$id_field     = 'ID';
+				$where_sql    = Jetpack_Sync_Settings::get_blacklisted_post_types_sql();
+				if ( empty( $columns ) ) {
+					$columns = Jetpack_Sync_Defaults::$default_post_checksum_columns;
+				}
+				break;
+			case 'post_meta':
+				$object_table = $wpdb->postmeta;
+				$where_sql    = Jetpack_Sync_Settings::get_whitelisted_post_meta_sql();
+				$object_count = $this->meta_count( $object_table, $where_sql, $start_id, $end_id );
+				$id_field     = 'meta_id';
+
+				if ( empty( $columns ) ) {
+					$columns = Jetpack_Sync_Defaults::$default_post_meta_checksum_columns;
+				}
+				break;
+			case 'comments':
+				$object_count = $this->comment_count( null, $start_id, $end_id );
+				$object_table = $wpdb->comments;
+				$id_field     = 'comment_ID';
+				$where_sql    = Jetpack_Sync_Settings::get_comments_filter_sql();
+				if ( empty( $columns ) ) {
+					$columns = Jetpack_Sync_Defaults::$default_comment_checksum_columns;
+				}
+				break;
+			case 'comment_meta':
+				$object_table = $wpdb->commentmeta;
+				$where_sql    = Jetpack_Sync_Settings::get_whitelisted_comment_meta_sql();
+				$object_count = $this->meta_count( $object_table, $where_sql, $start_id, $end_id );
+				$id_field     = 'meta_id';
+				if ( empty( $columns ) ) {
+					$columns = Jetpack_Sync_Defaults::$default_post_meta_checksum_columns;
+				}
+				break;
+			default:
+				return false;
+		}
+
+		$bucket_size     = intval( ceil( $object_count / $buckets ) );
+		$previous_max_id = 0;
+		$histogram       = array();
+
+		$where = '1=1';
+
+		if ( $start_id ) {
+			$where .= " AND $id_field >= " . intval( $start_id );
+		}
+
+		if ( $end_id ) {
+			$where .= " AND $id_field <= " . intval( $end_id );
+		}
+
+		do {
+			list( $first_id, $last_id ) = $wpdb->get_row(
+				"SELECT MIN($id_field) as min_id, MAX($id_field) as max_id FROM ( SELECT $id_field FROM $object_table WHERE $where AND $id_field > $previous_max_id ORDER BY $id_field ASC LIMIT $bucket_size ) as ids",
+				ARRAY_N
+			);
+
+			if ( null === $first_id || null === $last_id  ) {
+				// Nothing to checksum here...
+				break;
+			}
+
+			// get the checksum value
+			$value = $this->table_checksum( $object_table, $columns, $id_field, $where_sql, $first_id, $last_id, $strip_non_ascii, $salt );
+
+			if ( is_wp_error( $value ) ) {
+				return $value;
+			}
+
+			if ( null === $first_id || null === $last_id  ) {
+				break;
+			} elseif ( $first_id === $last_id ) {
+				$histogram[ $first_id ] = $value;
+			} else {
+				$histogram[ "{$first_id}-{$last_id}" ] = $value;
+			}
+
+			$previous_max_id = $last_id;
+		} while ( true );
+
+		return $histogram;
+	}
+
+	private function table_checksum( $table, $columns, $id_column, $where_sql = '1=1', $min_id = null, $max_id = null, $strip_non_ascii = true, $salt = '' ) {
+		global $wpdb;
+
+		// sanitize to just valid MySQL column names
+		$sanitized_columns = preg_grep( '/^[0-9,a-z,A-Z$_]+$/i', $columns );
+
+		if ( $strip_non_ascii ) {
+			$columns_sql = implode( ',', array_map( array( $this, 'strip_non_ascii_sql' ), $sanitized_columns ) );
+		} else {
+			$columns_sql = implode( ',', $sanitized_columns );
+		}
+
+		if ( null !== $min_id && null !== $max_id ) {
+			if ( $min_id === $max_id ) {
+				$min_id = intval( $min_id );
+				$where_sql .= " AND $id_column = $min_id LIMIT 1";
+			} else {
+				$min_id = intval( $min_id );
+				$max_id = intval( $max_id );
+				$size = $max_id - $min_id;
+				$where_sql .= " AND $id_column >= $min_id AND $id_column <= $max_id LIMIT $size";
+			}
+		} else {
+			if ( null !== $min_id ) {
+				$min_id = intval( $min_id );
+				$where_sql .= " AND $id_column >= $min_id";
+			}
+
+			if ( null !== $max_id ) {
+				$max_id = intval( $max_id );
+				$where_sql .= " AND $id_column <= $max_id";
+			}
+		}
+
+		$query = <<<ENDSQL
+			SELECT CAST( SUM( CRC32( CONCAT_WS( '#', '%s', {$columns_sql} ) ) ) AS UNSIGNED INT )
+			FROM $table
+			WHERE $where_sql;
+ENDSQL;
+		$result = $wpdb->get_var( $wpdb->prepare( $query, $salt ) );
+		if ( $wpdb->last_error ) {
+			return new WP_Error( 'database_error', $wpdb->last_error );
+		}
+
+		return $result;
+	}
+
+	public function get_checksum_type() {
+		return 'sum';
+	}
+
+	private function meta_count( $table, $where_sql, $min_id, $max_id ) {
+		global $wpdb;
+
+		if ( $min_id != null ) {
+			$where_sql .= ' AND meta_id >= ' . intval( $min_id );
+		}
+
+		if ( $max_id != null ) {
+			$where_sql .= ' AND meta_id <= ' . intval( $max_id );
+		}
+
+		return $wpdb->get_var( "SELECT COUNT(*) FROM $table WHERE $where_sql" );
+	}
+
+	/**
+	 * Wraps a column name in SQL which strips non-ASCII chars.
+	 * This helps normalize data to avoid checksum differences caused by
+	 * badly encoded data in the DB
+	 */
+	function strip_non_ascii_sql( $column_name ) {
+		return "REPLACE( CONVERT( $column_name USING ascii ), '?', '' )";
+	}
+
+	private function invalid_call() {
+		$backtrace = debug_backtrace();
+		$caller    = $backtrace[1]['function'];
+		throw new Exception( "This function $caller is not supported on the WP Replicastore" );
+	}
+}
diff --git a/plugins/jetpack/sync/interface.jetpack-sync-codec.php b/plugins/jetpack/sync/interface.jetpack-sync-codec.php
new file mode 100644
index 00000000..1405d90c
--- /dev/null
+++ b/plugins/jetpack/sync/interface.jetpack-sync-codec.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * Very simple interface for encoding and decoding input
+ * This is used to provide compression and serialization to messages
+ **/
+interface iJetpack_Sync_Codec {
+	// we send this with the payload so we can select the appropriate decoder at the other end
+	public function name();
+
+	public function encode( $object );
+
+	public function decode( $input );
+}
diff --git a/plugins/jetpack/sync/interface.jetpack-sync-replicastore.php b/plugins/jetpack/sync/interface.jetpack-sync-replicastore.php
new file mode 100644
index 00000000..c22f4e51
--- /dev/null
+++ b/plugins/jetpack/sync/interface.jetpack-sync-replicastore.php
@@ -0,0 +1,140 @@
+<?php
+/**
+ * Sync architecture prototype
+ *
+ * @author Dan Walmsley
+ * To run tests: phpunit --testsuite sync --filter New_Sync
+ */
+
+/**
+ * A high-level interface for objects that store synced WordPress data
+ * Useful for ensuring that different storage mechanisms implement the
+ * required semantics for storing all the data that we sync
+ */
+interface iJetpack_Sync_Replicastore {
+	// remove all data
+	public function reset();
+
+	// trigger setup for sync start/end
+	public function full_sync_start( $config );
+
+	public function full_sync_end( $checksum );
+
+	// posts
+	public function post_count( $status = null, $min_id = null, $max_id = null );
+
+	public function get_posts( $status = null, $min_id = null, $max_id = null );
+
+	public function get_post( $id );
+
+	public function upsert_post( $post, $silent = false );
+
+	public function delete_post( $post_id );
+
+	public function posts_checksum( $min_id = null, $max_id = null );
+	public function post_meta_checksum( $min_id = null, $max_id = null );
+
+	// comments
+	public function comment_count( $status = null, $min_id = null, $max_id = null );
+
+	public function get_comments( $status = null, $min_id = null, $max_id = null );
+
+	public function get_comment( $id );
+
+	public function upsert_comment( $comment );
+
+	public function trash_comment( $comment_id );
+
+	public function spam_comment( $comment_id );
+
+	public function delete_comment( $comment_id );
+
+	public function trashed_post_comments( $post_id, $statuses );
+
+	public function untrashed_post_comments( $post_id );
+
+	public function comments_checksum( $min_id = null, $max_id = null );
+	public function comment_meta_checksum( $min_id = null, $max_id = null );
+
+	// options
+	public function update_option( $option, $value );
+
+	public function get_option( $option, $default = false );
+
+	public function delete_option( $option );
+
+	// themes
+	public function set_theme_support( $theme_support );
+
+	public function current_theme_supports( $feature );
+
+	// meta
+	public function get_metadata( $type, $object_id, $meta_key = '', $single = false );
+
+	public function upsert_metadata( $type, $object_id, $meta_key, $meta_value, $meta_id );
+
+	public function delete_metadata( $type, $object_id, $meta_ids );
+
+	public function delete_batch_metadata( $type, $object_ids, $meta_key );
+
+	// constants
+	public function get_constant( $constant );
+
+	public function set_constant( $constant, $value );
+
+	// updates
+	public function get_updates( $type );
+
+	public function set_updates( $type, $updates );
+
+	// functions
+	public function get_callable( $callable );
+
+	public function set_callable( $callable, $value );
+
+	// network options
+	public function get_site_option( $option );
+
+	public function update_site_option( $option, $value );
+
+	public function delete_site_option( $option );
+
+	// terms
+	public function get_terms( $taxonomy );
+
+	public function get_term( $taxonomy, $term_id, $is_term_id = true );
+
+	public function update_term( $term_object );
+
+	public function delete_term( $term_id, $taxonomy );
+
+	public function get_the_terms( $object_id, $taxonomy );
+
+	public function update_object_terms( $object_id, $taxonomy, $terms, $append );
+
+	public function delete_object_terms( $object_id, $tt_ids );
+
+	// users
+	public function user_count();
+
+	public function get_user( $user_id );
+
+	public function upsert_user( $user );
+
+	public function delete_user( $user_id );
+
+	public function upsert_user_locale( $user_id, $locale );
+
+	public function delete_user_locale( $user_id );
+
+	public function get_user_locale( $user_id );
+
+	public function get_allowed_mime_types( $user_id );
+
+
+	// full checksum
+	public function checksum_all();
+
+	// histogram
+	public function checksum_histogram( $object_type, $buckets, $start_id = null, $end_id = null );
+}