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[Real-time collaboration] Fix race condition in compaction #75835

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[Real-time collaboration] Fix race condition in compaction #75835

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e43e415
Switch to targetd update deletion
maxschmeling Feb 23, 2026
7e38795
Return false early if deletion fails
maxschmeling Feb 23, 2026
4bad38d
More efficient meta deletion (using ID)
maxschmeling Feb 23, 2026
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178 changes: 110 additions & 68 deletions lib/compat/wordpress-7.0/class-wp-sync-post-meta-storage.php
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
* @package gutenberg
*/

if ( ! class_exists( 'WP_Sync_Post_Meta_Storage' ) ) {
if (!class_exists('WP_Sync_Post_Meta_Storage')) {

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/**
* Core class that provides an interface for storing and retrieving sync
Expand All @@ -17,7 +17,8 @@
*
* @access private
*/
class WP_Sync_Post_Meta_Storage implements WP_Sync_Storage {
class WP_Sync_Post_Meta_Storage implements WP_Sync_Storage
{

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/**
* Post type for sync storage.
*
Expand Down Expand Up @@ -75,19 +76,20 @@
* @param mixed $update Sync update.
* @return bool True on success, false on failure.
*/
public function add_update( string $room, $update ): bool {
$post_id = $this->get_storage_post_id( $room );
if ( null === $post_id ) {
public function add_update(string $room, $update): bool

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{

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$post_id = $this->get_storage_post_id($room);
if (null === $post_id) {
return false;
}

// Create an envelope and stamp each update to enable cursor-based filtering.
$envelope = array(
'timestamp' => $this->get_time_marker(),
'value' => $update,
'value' => $update,

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);

return (bool) add_post_meta( $post_id, self::SYNC_UPDATE_META_KEY, $envelope, false );
return (bool) add_post_meta($post_id, self::SYNC_UPDATE_META_KEY, $envelope, false);
}

/**
Expand All @@ -98,29 +100,30 @@
* @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.
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 ) {
$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 );
$updates = get_post_meta($post_id, self::SYNC_UPDATE_META_KEY, false);

if ( ! is_array( $updates ) ) {
if (!is_array($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( $update['timestamp'] );
static function ($update): bool {
return is_array($update) && isset($update['timestamp'], $update['value']) && is_int($update['timestamp']);
}
);

$this->room_update_counts[ $room ] = count( $updates );
$this->room_update_counts[$room] = count($updates);

return $updates;
}
Expand All @@ -133,19 +136,20 @@
* @param string $room Room identifier.
* @return array<int, mixed> Awareness state.
*/
public function get_awareness_state( string $room ): array {
$post_id = $this->get_storage_post_id( $room );
if ( null === $post_id ) {
public function get_awareness_state(string $room): array
{
$post_id = $this->get_storage_post_id($room);
if (null === $post_id) {
return array();
}

$awareness = get_post_meta( $post_id, self::AWARENESS_META_KEY, true );
$awareness = get_post_meta($post_id, self::AWARENESS_META_KEY, true);

if ( ! is_array( $awareness ) ) {
if (!is_array($awareness)) {
return array();
}

return array_values( $awareness );
return array_values($awareness);
}

/**
Expand All @@ -157,14 +161,15 @@
* @param array<int, mixed> $awareness Serializable awareness state.
* @return bool True on success, false on failure.
*/
public function set_awareness_state( string $room, array $awareness ): bool {
$post_id = $this->get_storage_post_id( $room );
if ( null === $post_id ) {
public function set_awareness_state(string $room, array $awareness): bool
{
$post_id = $this->get_storage_post_id($room);
if (null === $post_id) {
return false;
}

// update_post_meta returns false if the value is the same as the existing value.
update_post_meta( $post_id, self::AWARENESS_META_KEY, $awareness );
update_post_meta($post_id, self::AWARENESS_META_KEY, $awareness);
return true;
}

Expand All @@ -180,8 +185,9 @@
* @param string $room Room identifier.
* @return int Current cursor for the room.
*/
public function get_cursor( string $room ): int {
return $this->room_cursors[ $room ] ?? 0;
public function get_cursor(string $room): int
{
return $this->room_cursors[$room] ?? 0;
}

/**
Expand All @@ -195,42 +201,43 @@
* @param string $room Room identifier.
* @return int|null Post ID.
*/
private function get_storage_post_id( string $room ): ?int {
$room_hash = md5( $room );
private function get_storage_post_id(string $room): ?int
{
$room_hash = md5($room);

if ( isset( self::$storage_post_ids[ $room_hash ] ) ) {
return self::$storage_post_ids[ $room_hash ];
if (isset(self::$storage_post_ids[$room_hash])) {
return self::$storage_post_ids[$room_hash];
}

// Try to find an existing post for this room.
$posts = get_posts(
array(
'post_type' => self::POST_TYPE,
'post_type' => self::POST_TYPE,

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'posts_per_page' => 1,
'post_status' => 'publish',
'name' => $room_hash,
'fields' => 'ids',
'post_status' => 'publish',

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'name' => $room_hash,

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'fields' => 'ids',

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)
);

$post_id = array_first( $posts );
if ( is_int( $post_id ) ) {
self::$storage_post_ids[ $room_hash ] = $post_id;
$post_id = array_first($posts);
if (is_int($post_id)) {
self::$storage_post_ids[$room_hash] = $post_id;
return $post_id;
}

// Create new post for this room.
$post_id = wp_insert_post(
array(
'post_type' => self::POST_TYPE,
'post_type' => self::POST_TYPE,

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'post_status' => 'publish',
'post_title' => 'Sync Storage',
'post_name' => $room_hash,
'post_title' => 'Sync Storage',

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'post_name' => $room_hash,

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)
);

if ( is_int( $post_id ) ) {
self::$storage_post_ids[ $room_hash ] = $post_id;
if (is_int($post_id)) {
self::$storage_post_ids[$room_hash] = $post_id;
return $post_id;
}

Expand All @@ -244,8 +251,9 @@
*
* @return int Current time in milliseconds.
*/
private function get_time_marker(): int {
return (int) floor( microtime( true ) * 1000 );
private function get_time_marker(): int
{
return (int) floor(microtime(true) * 1000);
}

/**
Expand All @@ -256,8 +264,9 @@
* @param string $room Room identifier.
* @return int Number of updates stored for the room.
*/
public function get_update_count( string $room ): int {
return $this->room_update_counts[ $room ] ?? 0;
public function get_update_count(string $room): int
{
return $this->room_update_counts[$room] ?? 0;
}

/**
Expand All @@ -270,23 +279,24 @@
* @param int $cursor Return updates after this cursor.
* @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();
public function get_updates_after_cursor(string $room, int $cursor): array
{
$all_updates = $this->get_all_updates($room);
$updates = array();

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foreach ( $all_updates as $update ) {
if ( $update['timestamp'] > $cursor ) {
foreach ($all_updates as $update) {
if ($update['timestamp'] > $cursor) {
$updates[] = $update;
}
}

// Sort by timestamp to ensure order.
usort(
$updates,
fn ( $a, $b ) => $a['timestamp'] <=> $b['timestamp']
fn($a, $b) => $a['timestamp'] <=> $b['timestamp']
);

return wp_list_pluck( $updates, 'value' );
return wp_list_pluck($updates, 'value');
}

/**
Expand All @@ -298,28 +308,60 @@
* @param int $cursor Remove updates with markers < this cursor.
* @return bool True on success, false on failure.
*/
public function remove_updates_before_cursor( string $room, int $cursor ): bool {
$post_id = $this->get_storage_post_id( $room );
if ( null === $post_id ) {
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) {
return false;
}

$all_updates = $this->get_all_updates( $room );
// Fetch all metas for the sync update meta key for this post, including meta_id and value.
$meta_key = self::SYNC_UPDATE_META_KEY;
$metas = $wpdb->get_results(

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$wpdb->prepare(
"
SELECT meta_id, meta_value
FROM $wpdb->postmeta
WHERE post_id = %d
AND meta_key = %s
",
$post_id,
$meta_key
),
ARRAY_A
);

// Remove all updates for the room and re-store only those that are newer than the cursor.
if ( ! delete_post_meta( $post_id, self::SYNC_UPDATE_META_KEY ) ) {
return false;
if (!is_array($metas)) {
return true;
}

$delete_ids = array();
foreach ($metas as $meta) {
$envelope = maybe_unserialize($meta['meta_value']);
if (
is_array($envelope) &&
isset($envelope['timestamp']) &&
is_int($envelope['timestamp']) &&
$envelope['timestamp'] < $cursor
) {
$delete_ids[] = (int) $meta['meta_id'];
}
}

// 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, $envelope, false );
if (empty($delete_ids)) {
return true;
}

foreach ($delete_ids as $meta_id) {
$deleted = delete_metadata_by_mid('post', $meta_id);
if (! $deleted) {
return false;
}
}

return $add_result;
return true;
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@chriszarate chriszarate Feb 23, 2026

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This is still not failing if delete_post_meta fails

}
}
}
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