Changeset 62064 for trunk/src/wp-includes/collaboration/class-wp-sync-post-meta-storage.php

Timestamp:

03/19/2026 01:13:06 PM (4 months ago)

Author:

ellatrix

Message:

Real-time collaboration: fix race condition in default polling provider.

See also: ​https://github.com/WordPress/wordpress-develop/pull/11067.
Developed in: ​https://github.com/WordPress/wordpress-develop/pull/11292.

Fixes #64887.
Props czarate, westonruter, mindctrl, peterwilsoncc, joefusco.

File:

• trunk/src/wp-includes/collaboration/class-wp-sync-post-meta-storage.php (modified) (6 diffs)

trunk/src/wp-includes/collaboration/class-wp-sync-post-meta-storage.php

@@ -80 +80 @@
                 }
 
-                // Create an envelope and stamp each update to enable cursor-based filtering.
-                $envelope = array(
-                        'timestamp' => $this->get_time_marker(),
-                        'value'     => $update,
-                );
-
-                return (bool) add_post_meta( $post_id, wp_slash( self::SYNC_UPDATE_META_KEY ), wp_slash( $envelope ), false );
-        }
-
-        /**
-         * Retrieves all sync updates for a given room.
-         *
-         * @since 7.0.0
-         *
-         * @param string $room Room identifier.
-         * @return array<int, array{ timestamp: int, value: mixed }> Sync updates.
-         */
-        private function get_all_updates( string $room ): array {
-                $this->room_cursors[ $room ] = $this->get_time_marker() - 100; // Small buffer to ensure consistency.
-
-                $post_id = $this->get_storage_post_id( $room );
-                if ( null === $post_id ) {
-                        return array();
-                }
-
-                $updates = get_post_meta( $post_id, self::SYNC_UPDATE_META_KEY, false );
-
-                if ( ! is_array( $updates ) ) {
-                        $updates = array();
-                }
-
-                // Filter out any updates that don't have the expected structure.
-                $updates = array_filter(
-                        $updates,
-                        static function ( $update ): bool {
-                                return is_array( $update ) && isset( $update['timestamp'], $update['value'] ) && is_int( $update['timestamp'] );
-                        }
-                );
-
-                $this->room_update_counts[ $room ] = count( $updates );
-
-                return $updates;
+                $meta_id = add_post_meta( $post_id, self::SYNC_UPDATE_META_KEY, $update, false );
+
+                return (bool) $meta_id;
         }
 
@@ -171 +132 @@
          *
          * The cursor is set during get_updates_after_cursor() and represents the
-         * point in time just before the updates were retrieved, with a small buffer
-         * to ensure consistency.
+         * highest meta_id seen for the room's sync updates.
          *
          * @since 7.0.0
@@ -237 +197 @@
 
         /**
-         * Gets the current time in milliseconds as a comparable time marker.
-         *
-         * @since 7.0.0
-         *
-         * @return int Current time in milliseconds.
-         */
-        private function get_time_marker(): int {
-                return (int) floor( microtime( true ) * 1000 );
-        }
-
-        /**
          * Gets the number of updates stored for a given room.
          *
@@ -260 +209 @@
 
         /**
-         * Retrieves sync updates from a room for a given client and cursor. Updates
-         * from the specified client should be excluded.
+         * Retrieves sync updates from a room after the given cursor.
          *
          * @since 7.0.0
          *
          * @param string $room   Room identifier.
-         * @param int    $cursor Return updates after this cursor.
+         * @param int    $cursor Return updates after this cursor (meta_id).
          * @return array<int, mixed> Sync updates.
          */
         public function get_updates_after_cursor( string $room, int $cursor ): array {
-                $all_updates = $this->get_all_updates( $room );
-                $updates     = array();
-
-                foreach ( $all_updates as $update ) {
-                        if ( $update['timestamp'] > $cursor ) {
-                                $updates[] = $update;
-                        }
-                }
-
-                // Sort by timestamp to ensure order.
-                usort(
-                        $updates,
-                        fn ( $a, $b ) => $a['timestamp'] <=> $b['timestamp']
-                );
-
-                return wp_list_pluck( $updates, 'value' );
+                global $wpdb;
+
+                $post_id = $this->get_storage_post_id( $room );
+                if ( null === $post_id ) {
+                        $this->room_cursors[ $room ]       = 0;
+                        $this->room_update_counts[ $room ] = 0;
+                        return array();
+                }
+
+                // Capture the current room state first so the returned cursor is race-safe.
+                $stats = $wpdb->get_row(
+                        $wpdb->prepare(
+                                "SELECT COUNT(*) AS total_updates, COALESCE( MAX(meta_id), 0 ) AS max_meta_id FROM {$wpdb->postmeta} WHERE post_id = %d AND meta_key = %s",
+                                $post_id,
+                                self::SYNC_UPDATE_META_KEY
+                        )
+                );
+
+                $total_updates = $stats ? (int) $stats->total_updates : 0;
+                $max_meta_id   = $stats ? (int) $stats->max_meta_id : 0;
+
+                $this->room_update_counts[ $room ] = $total_updates;
+                $this->room_cursors[ $room ]       = $max_meta_id;
+
+                if ( $max_meta_id <= $cursor ) {
+                        return array();
+                }
+
+                $rows = $wpdb->get_results(
+                        $wpdb->prepare(
+                                "SELECT meta_value FROM {$wpdb->postmeta} WHERE post_id = %d AND meta_key = %s AND meta_id > %d AND meta_id <= %d ORDER BY meta_id ASC",
+                                $post_id,
+                                self::SYNC_UPDATE_META_KEY,
+                                $cursor,
+                                $max_meta_id
+                        )
+                );
+
+                if ( ! $rows ) {
+                        return array();
+                }
+
+                $updates = array();
+                foreach ( $rows as $row ) {
+                        $updates[] = maybe_unserialize( $row->meta_value );
+                }
+
+                return $updates;
         }
 
@@ -294 +274 @@
          *
          * @param string $room   Room identifier.
-         * @param int    $cursor Remove updates with markers < this cursor.
+         * @param int    $cursor Remove updates with meta_id < this cursor.
          * @return bool True on success, false on failure.
          */
         public function remove_updates_before_cursor( string $room, int $cursor ): bool {
+                global $wpdb;
+
                 $post_id = $this->get_storage_post_id( $room );
                 if ( null === $post_id ) {
@@ -303 +285 @@
                 }
 
-                $all_updates = $this->get_all_updates( $room );
-
-                // Remove all updates for the room and re-store only those that are newer than the cursor.
-                if ( ! delete_post_meta( $post_id, wp_slash( self::SYNC_UPDATE_META_KEY ) ) ) {
+                $deleted_rows = $wpdb->query(
+                        $wpdb->prepare(
+                                "DELETE FROM {$wpdb->postmeta} WHERE post_id = %d AND meta_key = %s AND meta_id < %d",
+                                $post_id,
+                                self::SYNC_UPDATE_META_KEY,
+                                $cursor
+                        )
+                );
+
+                if ( false === $deleted_rows ) {
                         return false;
                 }
 
-                // Re-store envelopes directly to avoid double-wrapping by add_update().
-                $add_result = true;
-                foreach ( $all_updates as $envelope ) {
-                        if ( $add_result && $envelope['timestamp'] >= $cursor ) {
-                                $add_result = (bool) add_post_meta( $post_id, self::SYNC_UPDATE_META_KEY, $envelope, false );
-                        }
-                }
-
-                return $add_result;
+                return true;
         }
 }