n context.
	 * @param bool      $valid_action If the action is valid.
	 *
	 * @return void
	 */
	private function handle_action_error( $action_id, $e, $context, $valid_action ) {
		if ( $valid_action ) {
			$this->store->mark_failure( $action_id );
			/**
			 * Runs when action execution fails.
			 *
			 * @param int       $action_id Action ID.
			 * @param Exception $e         Exception instance.
			 * @param string    $context   Execution context.
			 */
			do_action( 'action_scheduler_failed_execution', $action_id, $e, $context );
		} else {
			/**
			 * Runs when action validation fails.
			 *
			 * @param int       $action_id Action ID.
			 * @param Exception $e         Exception instance.
			 * @param string    $context   Execution context.
			 */
			do_action( 'action_scheduler_failed_validation', $action_id, $e, $context );
		}
	}

	/**
	 * Schedule the next instance of the action if necessary.
	 *
	 * @param ActionScheduler_Action $action
	 * @param int $action_id
	 */
	protected function schedule_next_instance( ActionScheduler_Action $action, $action_id ) {
		// If a recurring action has been consistently failing, we may wish to stop rescheduling it.
		if (
			ActionScheduler_Store::STATUS_FAILED === $this->store->get_status( $action_id )
			&& $this->recurring_action_is_consistently_failing( $action, $action_id )
		) {
			ActionScheduler_Logger::instance()->log(
				$action_id,
				__( 'This action appears to be consistently failing. A new instance will not be scheduled.', 'woocommerce' )
			);

			return;
		}

		try {
			ActionScheduler::factory()->repeat( $action );
		} catch ( Exception $e ) {
			do_action( 'action_scheduler_failed_to_schedule_next_instance', $action_id, $e, $action );
		}
	}

	/**
	 * Determine if the specified recurring action has been consistently failing.
	 *
	 * @param ActionScheduler_Action $action    The recurring action to be rescheduled.
	 * @param int                    $action_id The ID of the recurring action.
	 *
	 * @return bool
	 */
	private function recurring_action_is_consistently_failing( ActionScheduler_Action $action, $action_id ) {
		/**
		 * Controls the failure threshold for recurring actions.
		 *
		 * Before rescheduling a recurring action, we look at its status. If it failed, we then check if all of the most
		 * recent actions (upto the threshold set by this filter) sharing the same hook have also failed: if they have,
		 * that is considered consistent failure and a new instance of the action will not be scheduled.
		 *
		 * @param int $failure_threshold Number of actions of the same hook to examine for failure. Defaults to 5.
		 */
		$consistent_failure_threshold = (int) apply_filters( 'action_scheduler_recurring_action_failure_threshold', 5 );

		// This query should find the earliest *failing* action (for the hook we are interested in) within our threshold.
		$query_args = array(
			'hook'         => $action->get_hook(),
			'status'       => ActionScheduler_Store::STATUS_FAILED,
			'date'         => date_create( 'now', timezone_open( 'UTC' ) )->format( 'Y-m-d H:i:s' ),
			'date_compare' => '<',
			'per_page'     => 1,
			'offset'       => $consistent_failure_threshold - 1
		);

		$first_failing_action_id = $this->store->query_actions( $query_args );

		// If we didn't retrieve an action ID, then there haven't been enough failures for us to worry about.
		if ( empty( $first_failing_action_id ) ) {
			return false;
		}

		// Now let's fetch the first action (having the same hook) of *any status* within the same window.
		unset( $query_args['status'] );
		$first_action_id_with_the_same_hook = $this->store->query_actions( $query_args );

		/**
		 * If a recurring action is assessed as consistently failing, it will not be rescheduled. This hook provides a
		 * way to observe and optionally override that assessment.
		 *
		 * @param bool                   $is_consistently_failing If the action is considered to be consistently failing.
		 * @param ActionScheduler_Action $action                  The action being assessed.
		 */
		return (bool) apply_filters(
			'action_scheduler_recurring_action_is_consistently_failing',
			$first_action_id_with_the_same_hook === $first_failing_action_id,
			$action
		);
	}

	/**
	 * Run the queue cleaner.
	 *
	 * @author Jeremy Pry
	 */
	protected function run_cleanup() {
		$this->cleaner->clean( 10 * $this->get_time_limit() );
	}

	/**
	 * Get the number of concurrent batches a runner allows.
	 *
	 * @return int
	 */
	public function get_allowed_concurrent_batches() {
		return apply_filters( 'action_scheduler_queue_runner_concurrent_batches', 1 );
	}

	/**
	 * Check if the number of allowed concurrent batches is met or exceeded.
	 *
	 * @return bool
	 */
	public function has_maximum_concurrent_batches() {
		return $this->store->get_claim_count() >= $this->get_allowed_concurrent_batches();
	}

	/**
	 * Get the maximum number of seconds a batch can run for.
	 *
	 * @return int The number of seconds.
	 */
	protected function get_time_limit() {

		$time_limit = 30;

		// Apply deprecated filter from deprecated get_maximum_execution_time() method
		if ( has_filter( 'action_scheduler_maximum_execution_time' ) ) {
			_deprecated_function( 'action_scheduler_maximum_execution_time', '2.1.1', 'action_scheduler_queue_runner_time_limit' );
			$time_limit = apply_filters( 'action_scheduler_maximum_execution_time', $time_limit );
		}

		return absint( apply_filters( 'action_scheduler_queue_runner_time_limit', $time_limit ) );
	}

	/**
	 * Get the number of seconds the process has been running.
	 *
	 * @return int The number of seconds.
	 */
	protected function get_execution_time() {
		$execution_time = microtime( true ) - $this->created_time;

		// Get the CPU time if the hosting environment uses it rather than wall-clock time to calculate a process's execution time.
		if ( function_exists( 'getrusage' ) && apply_filters( 'action_scheduler_use_cpu_execution_time', defined( 'PANTHEON_ENVIRONMENT' ) ) ) {
			$resource_usages = getrusage();

			if ( isset( $resource_usages['ru_stime.tv_usec'], $resource_usages['ru_stime.tv_usec'] ) ) {
				$execution_time = $resource_usages['ru_stime.tv_sec'] + ( $resource_usages['ru_stime.tv_usec'] / 1000000 );
			}
		}

		return $execution_time;
	}

	/**
	 * Check if the host's max execution time is (likely) to be exceeded if processing more actions.
	 *
	 * @param int $processed_actions The number of actions processed so far - used to determine the likelihood of exceeding the time limit if processing another action
	 * @return bool
	 */
	protected function time_likely_to_be_exceeded( $processed_actions ) {
		$execution_time     = $this->get_execution_time();
		$max_execution_time = $this->get_time_limit();

		// Safety against division by zero errors.
		if ( 0 === $processed_actions ) {
			return $execution_time >= $max_execution_time;
		}

		$time_per_action       = $execution_time / $processed_actions;
		$estimated_time        = $execution_time + ( $time_per_action * 3 );
		$likely_to_be_exceeded = $estimated_time > $max_execution_time;

		return apply_filters( 'action_scheduler_maximum_execution_time_likely_to_be_exceeded', $likely_to_be_exceeded, $this, $processed_actions, $execution_time, $max_execution_time );
	}

	/**
	 * Get memory limit
	 *
	 * Based on WP_Background_Process::get_memory_limit()
	 *
	 * @return int
	 */
	protected function get_memory_limit() {
		if ( function_exists( 'ini_get' ) ) {
			$memory_limit = ini_get( 'memory_limit' );
		} else {
			$memory_limit = '128M'; // Sensible default, and minimum required by WooCommerce
		}

		if ( ! $memory_limit || -1 === $memory_limit || '-1' === $memory_limit ) {
			// Unlimited, set to 32GB.
			$memory_limit = '32G';
		}

		return ActionScheduler_Compatibility::convert_hr_to_bytes( $memory_limit );
	}

	/**
	 * Memory exceeded
	 *
	 * Ensures the batch process never exceeds 90% of the maximum WordPress memory.
	 *
	 * Based on WP_Background_Process::memory_exceeded()
	 *
	 * @return bool
	 */
	protected function memory_exceeded() {

		$memory_limit    = $this->get_memory_limit() * 0.90;
		$current_memory  = memory_get_usage( true );
		$memory_exceeded = $current_memory >= $memory_limit;

		return apply_filters( 'action_scheduler_memory_exceeded', $memory_exceeded, $this );
	}

	/**
	 * See if the batch limits have been exceeded, which is when memory usage is almost at
	 * the maximum limit, or the time to process more actions will exceed the max time limit.
	 *
	 * Based on WC_Background_Process::batch_limits_exceeded()
	 *
	 * @param int $processed_actions The number of actions processed so far - used to determine the likelihood of exceeding the time limit if processing another action
	 * @return bool
	 */
	protected function batch_limits_exceeded( $processed_actions ) {
		return $this->memory_exceeded() || $this->time_likely_to_be_exceeded( $processed_actions );
	}

	/**
	 * Process actions in the queue.
	 *
	 * @author Jeremy Pry
	 * @param string $context Optional identifer for the context in which this action is being processed, e.g. 'WP CLI' or 'WP Cron'
	 *        Generally, this should be capitalised and not localised as it's a proper noun.
	 * @return int The number of actions processed.
	 */
	abstract public function run( $context = '' );
}