Stats: add filter to allow customizing the cache duration (#35421)

This would allow third-parties to change the default caching duration from 5 minutes to something else, when they need their site to make less queries to WordPress.com in general.

projects/packages/stats/changelog/update-stats-pulling-jetpack-filter

@@ -0,0 +1,4 @@
+Significance: patch
+Type: added
+
+Stats fetching mechanism: add filter allowing one to customize how long we cache results.

projects/packages/stats/src/class-wpcom-stats.php

@@ -398,7 +398,20 @@ protected function fetch_stats( $args = array() ) {
 
 		// To reduce size in storage: store with time as key, store JSON encoded data.
 		$cached_value = is_wp_error( $wpcom_stats ) ? $wpcom_stats : wp_json_encode( $wpcom_stats );
-		$expiration   = self::STATS_CACHE_EXPIRATION_IN_MINUTES * MINUTE_IN_SECONDS;
+
+		/**
+		 * Filters the expiration time for the stats cache.
+		 *
+		 * @module stats
+		 *
+		 * @since $$next-version$$
+		 *
+		 * @param int $expiration The expiration time in minutes.
+		 */
+		$expiration = apply_filters(
+			'jetpack_fetch_stats_cache_expiration',
+			self::STATS_CACHE_EXPIRATION_IN_MINUTES * MINUTE_IN_SECONDS
+		);
 		set_transient( $transient_name, array( time() => $cached_value ), $expiration );
 
 		return $wpcom_stats;
@@ -428,8 +441,13 @@ protected function fetch_post_stats( $args, $post_id ) {
 				return $data;
 			}
 
-			$time       = key( $data );
-			$expiration = self::STATS_CACHE_EXPIRATION_IN_MINUTES * MINUTE_IN_SECONDS;
+			$time = key( $data );
+
+			/** This filter is already documented in projects/packages/stats/src/class-wpcom-stats.php */
+			$expiration = apply_filters(
+				'jetpack_fetch_stats_cache_expiration',
+				self::STATS_CACHE_EXPIRATION_IN_MINUTES * MINUTE_IN_SECONDS
+			);
 
 			if ( ( time() - $time ) < $expiration ) {
 				return array_merge( array( 'cached_at' => $time ), $data[ $time ] );