Feeds: Cache RSS feeds in global transients.

Moves the caching of RSS feeds requested via `fetch_feed()` from single site transients (`get|set|delete_transient()`) to global transients (`get|set|delete_site_transient()`).

On multisite installs of WordPress, this replaces per site caching with the global multisite cache to allow a single cache to be shared between all sites. This reduces the amount of data stored in the database and improves performance of feeds when multiple sites are ingesting the same URL.

Props rollybueno, spacedmonkey, peterwilsoncc.
Fixes #63719.


git-svn-id: https://develop.svn.wordpress.org/trunk@60524 602fd350-edb4-49c9-b593-d223f7449a82

Author: peterwilsoncc

src/wp-includes/class-wp-feed-cache-transient.php

@@ -12,6 +12,7 @@
  *
  * @since 2.8.0
  * @since 6.7.0 Now properly implements the SimplePie\Cache\Base interface.
+ * @since 6.9.0 Switched to Multisite's global cache via the `*_site_transient()` functions.
  */
 #[AllowDynamicProperties]
 class WP_Feed_Cache_Transient implements SimplePie\Cache\Base {
@@ -84,8 +85,8 @@ public function save( $data ) {
 			$data = $data->data;
 		}
 
-		set_transient( $this->name, $data, $this->lifetime );
-		set_transient( $this->mod_name, time(), $this->lifetime );
+		set_site_transient( $this->name, $data, $this->lifetime );
+		set_site_transient( $this->mod_name, time(), $this->lifetime );
 		return true;
 	}
 
@@ -97,7 +98,7 @@ public function save( $data ) {
 	 * @return array Data for `SimplePie::$data`.
 	 */
 	public function load() {
-		return get_transient( $this->name );
+		return get_site_transient( $this->name );
 	}
 
 	/**
@@ -108,7 +109,7 @@ public function load() {
 	 * @return int Timestamp.
 	 */
 	public function mtime() {
-		return get_transient( $this->mod_name );
+		return get_site_transient( $this->mod_name );
 	}
 
 	/**
@@ -119,7 +120,7 @@ public function mtime() {
 	 * @return bool False if value was not set and true if value was set.
 	 */
 	public function touch() {
-		return set_transient( $this->mod_name, time(), $this->lifetime );
+		return set_site_transient( $this->mod_name, time(), $this->lifetime );
 	}
 
 	/**
@@ -130,8 +131,8 @@ public function touch() {
 	 * @return true Always true.
 	 */
 	public function unlink() {
-		delete_transient( $this->name );
-		delete_transient( $this->mod_name );
+		delete_site_transient( $this->name );
+		delete_site_transient( $this->mod_name );
 		return true;
 	}
 }

tests/phpunit/tests/feed/fetchFeed.php

@@ -57,6 +57,31 @@ public function test_fetch_feed_cached() {
 		$this->assertEquals( 1, $filter->get_call_count(), 'The feed should be cached on the second call. For SP 1.8.x upgrades, backport simplepie/simplepie#830 to resolve.' );
 	}
 
+	/**
+	 * Ensure that fetch_feed uses the global cache on Multisite.
+	 *
+	 * @ticket 63719
+	 *
+	 * @group feed
+	 * @group ms-required
+	 *
+	 * @covers ::fetch_feed
+	 * @covers WP_Feed_Cache_Transient
+	 */
+	public function test_fetch_feed_uses_global_cache() {
+		$second_blog_id = self::factory()->blog->create();
+
+		$filter = new MockAction();
+		add_filter( 'pre_http_request', array( $filter, 'filter' ) );
+
+		fetch_feed( 'https://wordpress.org/news/feed/' );
+
+		switch_to_blog( $second_blog_id );
+
+		fetch_feed( 'https://wordpress.org/news/feed/' );
+		$this->assertEquals( 1, $filter->get_call_count(), 'The feed cache should be global.' );
+	}
+
 	/**
 	 * Mock response for `fetch_feed()`.
 	 *