Modifications to Action Scheduler in order to run higher volumes of actions.

ActionSchedulerHighVolume.php

<?php
/**
 * High volume modifications to Action Scheduler.
 *
 * Adapted from https://github.com/woocommerce/action-scheduler-high-volume/
 *
 * Increase Action Scheduler batch size, concurrency, timeout period, and claim action query
 * ORDER BY to process large queues of actions more quickly on servers with more server resources.
 *
 * @package UniversalYums\ActionScheduler
 */

namespace UniversalYums\ActionScheduler;

class ActionSchedulerHighVolume {

	/**
	 * The single instance of the class.
	 *
	 * @var mixed
	 */
	protected static $instance;

	/**
	 * Ensures only one instance of ActionSchedulerHighVolume is loaded or can be loaded.
	 *
	 * @return ActionSchedulerHighVolume - Main instance.
	 */
	public static function instance() {
		if ( is_null( self::$instance ) ) {
			self::$instance = new self();
		}

		return self::$instance;
	}

	/**
	 * ActionSchedulerHighVolume constructor.
	 */
	public function __construct() {
		add_filter( 'action_scheduler_queue_runner_batch_size', [ $this, 'increase_queue_batch_size' ] );
		add_filter( 'action_scheduler_queue_runner_concurrent_batches', [ $this, 'increase_concurrent_batches' ], 10000 );
		add_filter( 'action_scheduler_timeout_period', [ $this, 'increase_timeout' ] );
		add_filter( 'action_scheduler_failure_period', [ $this, 'increase_timeout' ] );
		add_filter( 'action_scheduler_queue_runner_time_limit', [ $this, 'increase_time_limit' ] );
		add_filter( 'action_scheduler_claim_actions_order_by', [ $this, 'remove_order_by_date' ] );
	}

	/**
	 * Action scheduler claims a batch of actions to process in each request. It keeps the batch
	 * fairly small (by default, 25) in order to prevent errors, like memory exhaustion.
	 *
	 * This method increases it so that more actions are processed in each queue, which speeds up the
	 * overall queue processing time due to latency in requests and the minimum 1 minute between each
	 * queue being processed.
	 *
	 * For more details, see: https://actionscheduler.org/perf/#increasing-batch-size
	 *
	 * @param int $batch_size
	 */
	public function increase_queue_batch_size( $batch_size ) {
		return $batch_size * 2;
	}

	/**
	 * Action scheduler processes queues of actions in parallel to speed up the processing of large numbers
	 * If each queue takes a long time, this will result in multiple PHP processes being used to process actions,
	 * which can prevent PHP processes being available to serve requests from visitors. This is why it defaults to
	 * only 1 (as of Action Scheduler 3.4.0). However, on high volume sites, this can be increased to speed up the
	 * processing time for actions.
	 *
	 * Use with caution as doing this can take down your site completely depending on your PHP configuration.
	 *
	 * For more details, see: https://actionscheduler.org/perf/#increasing-concurrent-batches
	 *
	 * @param int $concurrent_batches
	 */
	public function increase_concurrent_batches( $concurrent_batches ) {
		return 20;
	}

	/**
	 * Action scheduler reset actions claimed for more than 5 minutes (300 seconds).
	 * Because we're increasing the batch size, we also want to increase the amount of time
	 * given to queues before reseting claimed actions.
	 *
	 * @param int $timeout
	 */
	public function increase_timeout( $timeout ) {
		return $timeout * 2;
	}

	/**
	 * Action Scheduler provides a default maximum of 30 seconds in which to process actions. Increase this to 120
	 * seconds for hosts like Pantheon which support such a long time limit, or if you know your PHP and Apache, Nginx
	 * or other web server configs support a longer time limit.
	 *
	 * Note, WP Engine only supports a maximum of 60 seconds - if using WP Engine, this will need to be decreased to 60.
	 *
	 * @param int $time_limit
	 */
	public function increase_time_limit( $time_limit ) {
		return 60;
	}

	/**
	 * Action Scheduler by default marks actions claimed in the order:
	 * `ORDER BY attempts ASC, scheduled_date_gmt ASC, action_id ASC`.
	 * We can improve improve the performance of this query by modifying the ORDER BY clause
	 * to remove, for example, ordering by `scheduled_date_gmt`, which, according to the docs,
	 * "considerably improves the speed of execution of the query and reduces the probability of deadlocks."
	 *
	 * @see https://developer.woocommerce.com/2021/11/01/action-scheduler-3-4-0/
	 *
	 * @param string $order_clause
	 */
	public function remove_order_by_date( $order_clause ) {
		return 'ORDER BY attempts ASC, action_id ASC';
	}

}