Merge pull request #5157 from Automattic/fix/sync-alternate-cron

Sync: Fix issue where listener/sender not loading for alternate cron

sync/class.jetpack-sync-actions.php

@@ -317,9 +317,18 @@ static function initialize_sender() {
 	}
 }
 
-// Allow other plugins to add filters before we initialize the actions.
-// Load the listeners if before modules get loaded so that we can capture version changes etc.
-add_action( 'init', array( 'Jetpack_Sync_Actions', 'init' ), 90 );
+/**
+ * If the site is using alternate cron, we need to init the listener and sender before cron
+ * runs. So, we init at a priority of 9.
+ * 
+ * If the site is using a regular cron job, we init at a priority of 90 which gives plugins a chance
+ * to add filters before we initialize.
+ */
+if ( defined( 'ALTERNATE_WP_CRON' ) && ALTERNATE_WP_CRON ) {
+	add_action( 'init', array( 'Jetpack_Sync_Actions', 'init' ), 9 );
+} else {
+	add_action( 'init', array( 'Jetpack_Sync_Actions', 'init' ), 90 );
+}
 
 // We need to define this here so that it's hooked before `updating_jetpack_version` is called
 add_action( 'updating_jetpack_version', array( 'Jetpack_Sync_Actions', 'schedule_initial_sync' ), 10, 2 );