fix: recover the database refresh chain a killed run ends

classes/Visualizer/Module/Setup.php

@@ -31,6 +31,27 @@ class Visualizer_Module_Setup extends Visualizer_Module {
 
 	const NAME = __CLASS__;
 
+	/**
+	 * Hook that refreshes database charts.
+	 */
+	const REFRESH_DB_HOOK = 'visualizer_schedule_refresh_db';
+
+	/**
+	 * Action Scheduler group that owns the refresh.
+	 */
+	const REFRESH_DB_GROUP = 'visualizer';
+
+	/**
+	 * When the refresh trigger was last checked.
+	 */
+	const REFRESH_DB_CHECK_OPTION = 'visualizer-refresh-db-checked';
+
+	/**
+	 * How long a check stays good for. Action Scheduler needs the same 300s to mark a
+	 * killed run failed, so a shorter window cannot recover one any sooner.
+	 */
+	const REFRESH_DB_CHECK_WINDOW = 300;
+
 	/**
 	 * Constructor.
 	 *
@@ -44,8 +65,9 @@ public function __construct( Visualizer_Plugin $plugin ) {
 
 		register_activation_hook( VISUALIZER_BASEFILE, array( $this, 'activate' ) );
 		register_deactivation_hook( VISUALIZER_BASEFILE, array( $this, 'deactivate' ) );
-		$this->_addAction( 'visualizer_schedule_refresh_db', 'refreshDbChart' );
+		$this->_addAction( self::REFRESH_DB_HOOK, 'refreshDbChart' );
 		$this->_addAction( 'init', 'maybe_reschedule_refresh_db' );
+		$this->_addAction( 'action_scheduler_ensure_recurring_actions', 'ensure_refresh_db_action' );
 		$this->_addFilter( 'visualizer_schedule_refresh_chart', 'refresh_db_for_chart', 10, 3 );
 
 		$this->_addAction( 'admin_init', 'adminInit' );
@@ -485,8 +507,8 @@ public function custom_cron_schedules( $schedules ) {
 	 * Schedule the recurring DB refresh action.
 	 */
 	private function schedule_refresh_db_action(): void {
-		$hook         = 'visualizer_schedule_refresh_db';
-		$group        = 'visualizer';
+		$hook         = self::REFRESH_DB_HOOK;
+		$group        = self::REFRESH_DB_GROUP;
 		$interval_key = apply_filters( 'visualizer_chart_schedule_interval', 'visualizer_ten_minutes' );
 		$interval     = $this->get_schedule_interval_seconds( $interval_key );
 		$timestamp    = strtotime( 'midnight' ) - get_option( 'gmt_offset' ) * HOUR_IN_SECONDS;
@@ -498,45 +520,84 @@ private function schedule_refresh_db_action(): void {
 		) {
 			$next = as_next_scheduled_action( $hook, array(), $group );
 			if ( false === $next ) {
-				as_schedule_recurring_action( $timestamp, $interval, $hook, array(), $group );
+				// Unique: this runs on every request, and Action Scheduler only creates the next
+				// recurrence once the current one completes, so a concurrent request can arrive
+				// while nothing is pending. Uniqueness is enforced in the insert itself.
+				as_schedule_recurring_action( $timestamp, $interval, $hook, array(), $group, true );
+
+				// The call returns 0 and stores nothing when creation fails, so ask the store.
+				$next = as_next_scheduled_action( $hook, array(), $group );
 			}
+
+			// Drop the WP-Cron fallback only once the action is there to replace it.
+			if ( false !== $next ) {
+				wp_clear_scheduled_hook( $hook );
+				return;
+			}
+		}
+
+		// Re-arm only when the event is missing or set to a different interval. This runs on
+		// every request while Action Scheduler keeps refusing, and re-arming a live event
+		// would pin it to a past timestamp and make the refresh due on every cron spawn.
+		$event = wp_get_scheduled_event( $hook );
+		if ( ! $event || $event->schedule !== $interval_key ) {
 			wp_clear_scheduled_hook( $hook );
+			wp_schedule_event( $timestamp, $interval_key, $hook );
+		}
+	}
+
+	/**
+	 * Check once per window that something still fires the refresh.
+	 *
+	 * Hooked to `init`, so it runs on every request. The timestamp is autoloaded and costs
+	 * no query, and the daily `action_scheduler_ensure_recurring_actions` hook is the floor
+	 * under it on a site that serves few requests.
+	 */
+	public function maybe_reschedule_refresh_db(): void {
+		$checked = (int) get_option( self::REFRESH_DB_CHECK_OPTION, 0 );
+		if ( time() - $checked < self::REFRESH_DB_CHECK_WINDOW ) {
 			return;
 		}
 
-		wp_clear_scheduled_hook( $hook );
-		wp_schedule_event( $timestamp, $interval_key, $hook );
+		update_option( self::REFRESH_DB_CHECK_OPTION, time(), true );
+		$this->ensure_refresh_db_action();
 	}
 
 	/**
-	 * Keep the DB refresh scheduled when Action Scheduler is not available.
+	 * Keep the DB refresh scheduled on whichever scheduler the site can use.
 	 *
-	 * The migration to Action Scheduler clears the WP-Cron event, so a site that
-	 * already migrated and then lost the library would have nothing left running
-	 * the refresh. Re-arms WP-Cron in that case; no-op whenever the library is up.
+	 * This is the only way back. Action Scheduler creates the next occurrence of a recurring
+	 * action inside schedule_next_instance(), which a killed run never reaches, so the chain
+	 * ends there and nothing but a reactivation used to restore it. Also covers a site that
+	 * lost Action Scheduler, and a legacy WP-Cron event that never migrated.
 	 */
-	public function maybe_reschedule_refresh_db(): void {
+	public function ensure_refresh_db_action(): void {
+		$hook = self::REFRESH_DB_HOOK;
+
 		if (
 			visualizer_can_use_action_scheduler()
 			&& function_exists( 'as_next_scheduled_action' )
 			&& function_exists( 'as_schedule_recurring_action' )
 		) {
-			return;
+			// Settled only once Action Scheduler holds the action and no WP-Cron event fires
+			// the same hook beside it; a site keeping both refreshes twice per interval.
+			$scheduled = false !== as_next_scheduled_action( $hook, array(), self::REFRESH_DB_GROUP )
+				&& ! wp_next_scheduled( $hook );
+		} else {
+			$scheduled = (bool) wp_next_scheduled( $hook );
 		}
 
-		if ( wp_next_scheduled( 'visualizer_schedule_refresh_db' ) ) {
-			return;
+		if ( ! $scheduled ) {
+			$this->schedule_refresh_db_action();
 		}
-
-		$this->schedule_refresh_db_action();
 	}
 
 	/**
 	 * Unschedule the recurring DB refresh action.
 	 */
 	private function unschedule_refresh_db_action(): void {
-		$hook  = 'visualizer_schedule_refresh_db';
-		$group = 'visualizer';
+		$hook  = self::REFRESH_DB_HOOK;
+		$group = self::REFRESH_DB_GROUP;
 		if ( function_exists( 'as_unschedule_all_actions' ) ) {
 			as_unschedule_all_actions( $hook, array(), $group );
 		}

classes/Visualizer/Module/Upgrade.php

@@ -24,11 +24,6 @@ public static function upgrade() {
 			$upgraded = true;
 		}
 
-		if ( wp_next_scheduled( 'visualizer_schedule_refresh_db' ) ) {
-			self::migrate_action_scheduler();
-			$upgraded = true;
-		}
-
 		if ( ! $upgraded ) {
 			return;
 		}
@@ -79,41 +74,4 @@ private static function makeAllTableChartsTabular() {
 		);
 		// phpcs:enable WordPress.DB.PreparedSQL.NotPrepared
 	}
-
-	/**
-	 * Migrate recurring WP-Cron jobs to Action Scheduler.
-	 */
-	private static function migrate_action_scheduler(): void {
-		if ( ! function_exists( 'as_schedule_recurring_action' ) || ! function_exists( 'as_next_scheduled_action' ) ) {
-			return;
-		}
-
-		$hook         = 'visualizer_schedule_refresh_db';
-		$group        = 'visualizer';
-		$interval_key = apply_filters( 'visualizer_chart_schedule_interval', 'visualizer_ten_minutes' );
-		$interval     = self::get_schedule_interval_seconds( $interval_key );
-		$timestamp    = strtotime( 'midnight' ) - get_option( 'gmt_offset' ) * HOUR_IN_SECONDS;
-
-		$next = as_next_scheduled_action( $hook, array(), $group );
-		if ( false === $next ) {
-			as_schedule_recurring_action( $timestamp, $interval, $hook, array(), $group );
-		}
-
-		wp_clear_scheduled_hook( $hook );
-	}
-
-	/**
-	 * Resolve a cron schedule key to seconds.
-	 *
-	 * @param string $interval_key Cron schedule key.
-	 * @return int Interval in seconds.
-	 */
-	private static function get_schedule_interval_seconds( $interval_key ) {
-		$schedules = wp_get_schedules();
-		if ( isset( $schedules[ $interval_key ]['interval'] ) ) {
-			return (int) $schedules[ $interval_key ]['interval'];
-		}
-
-		return 600;
-	}
 }