RTC: Use transients for awareness state (KISS approach).

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

@@ -25,12 +25,12 @@ class WP_Sync_Post_Meta_Storage implements WP_Sync_Storage {
 	const POST_TYPE = 'wp_sync_storage';
 
 	/**
-	 * Meta key for awareness state.
+	 * Transient prefix for awareness state.
 	 *
 	 * @since 7.0.0
 	 * @var string
 	 */
-	const AWARENESS_META_KEY = 'wp_sync_awareness';
+	const AWARENESS_TRANSIENT_PREFIX = 'wp_sync_awareness';
 
 	/**
 	 * Meta key for sync updates.
@@ -123,6 +123,24 @@ static function ( $update ): bool {
 		return $updates;
 	}
 
+	/**
+	 * Gets the transient key for awareness state for a given post ID.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int $post_id Post ID.
+	 * @return string Transient key for awareness state.
+	 */
+	public function get_awareness_transient_key( $post_id ) {
+		$cache_key = self::AWARENESS_TRANSIENT_PREFIX . '_' . $post_id;
+		if ( strlen( $cache_key ) <= 172 ) {
+			// Safe length for a transient key.
+			return $cache_key;
+		}
+		// If the cache key is too long, hash it to ensure it fits within limits.
+		return md5( $cache_key );
+	}
+
 	/**
 	 * Gets awareness state for a given room.
 	 *
@@ -137,7 +155,7 @@ public function get_awareness_state( string $room ): array {
 			return array();
 		}
 
-		$awareness = get_post_meta( $post_id, self::AWARENESS_META_KEY, true );
+		$awareness = get_transient( $this->get_awareness_transient_key( $post_id ) );
 
 		if ( ! is_array( $awareness ) ) {
 			return array();
@@ -161,8 +179,8 @@ public function set_awareness_state( string $room, array $awareness ): bool {
 			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 );
+		// set_transient() can return false if the value is the same as the existing value, which is considered a success regardless.
+		set_transient( $this->get_awareness_transient_key( $post_id ), $awareness, HOUR_IN_SECONDS );
 		return true;
 	}