includes/libraries/wp-background-process.php
<?php // @codingStandardsIgnoreLine.
/**
* Abstract WP_Background_Process class.
*
* @package WP-Background-Processing
* @extends WP_Async_Request
*/
defined( 'ABSPATH' ) || exit;
/**
* Abstract WP_Background_Process class.
*/
abstract class WP_Background_Process extends WP_Async_Request {
/**
* Action
*
* (default value: 'background_process')
*
* @var string
* @access protected
*/
protected $action = 'background_process';
/**
* Start time of current process.
*
* (default value: 0)
*
* @var int
* @access protected
*/
protected $start_time = 0;
/**
* Cron_hook_identifier
*
* @var mixed
* @access protected
*/
protected $cron_hook_identifier;
/**
* Cron_interval_identifier
*
* @var mixed
* @access protected
*/
protected $cron_interval_identifier;
/**
* Initiate new background process
*/
public function __construct() {
parent::__construct();
$this->cron_hook_identifier = $this->identifier . '_cron';
$this->cron_interval_identifier = $this->identifier . '_cron_interval';
add_action( $this->cron_hook_identifier, array( $this, 'handle_cron_healthcheck' ) );
add_filter( 'cron_schedules', array( $this, 'schedule_cron_healthcheck' ) );
}
/**
* Dispatch
*
* @access public
* @return void
*/
public function dispatch() {
// Schedule the cron healthcheck.
$this->schedule_event();
// Perform remote post.
return parent::dispatch();
}
/**
* Push to queue
*
* @param mixed $data Data.
*
* @return $this
*/
public function push_to_queue( $data ) {
$this->data[] = $data;
return $this;
}
/**
* Save queue
*
* @return $this
*/
public function save() {
$key = $this->generate_key();
if ( ! empty( $this->data ) ) {
update_site_option( $key, $this->data );
}
return $this;
}
/**
* Update queue
*
* @param string $key Key.
* @param array $data Data.
*
* @return $this
*/
public function update( $key, $data ) {
if ( ! empty( $data ) ) {
update_site_option( $key, $data );
}
return $this;
}
/**
* Delete queue
*
* @param string $key Key.
*
* @return $this
*/
public function delete( $key ) {
delete_site_option( $key );
return $this;
}
/**
* Generate key
*
* Generates a unique key based on microtime. Queue items are
* given a unique key so that they can be merged upon save.
*
* @param int $length Length.
*
* @return string
*/
protected function generate_key( $length = 64 ) {
$unique = md5( microtime() . rand() );
$prepend = $this->identifier . '_batch_';
return substr( $prepend . $unique, 0, $length );
}
/**
* Maybe process queue
*
* Checks whether data exists within the queue and that
* the process is not already running.
*/
public function maybe_handle() {
// Don't lock up other requests while processing
session_write_close();
if ( $this->is_process_running() ) {
// Background process already running.
wp_die();
}
if ( $this->is_queue_empty() ) {
// No data to process.
wp_die();
}
check_ajax_referer( $this->identifier, 'nonce' );
$this->handle();
wp_die();
}
/**
* Is queue empty
*
* @return bool
*/
protected function is_queue_empty() {
global $wpdb;
$table = $wpdb->options;
$column = 'option_name';
if ( is_multisite() ) {
$table = $wpdb->sitemeta;
$column = 'meta_key';
}
$key = $this->identifier . '_batch_%';
$count = $wpdb->get_var( $wpdb->prepare( "
SELECT COUNT(*)
FROM {$table}
WHERE {$column} LIKE %s
", $key ) );
return ! ( $count > 0 );
}
/**
* Is process running
*
* Check whether the current process is already running
* in a background process.
*/
protected function is_process_running() {
if ( get_site_transient( $this->identifier . '_process_lock' ) ) {
// Process already running.
return true;
}
return false;
}
/**
* Lock process
*
* Lock the process so that multiple instances can't run simultaneously.
* Override if applicable, but the duration should be greater than that
* defined in the time_exceeded() method.
*/
protected function lock_process() {
$this->start_time = time(); // Set start time of current process.
$lock_duration = ( property_exists( $this, 'queue_lock_time' ) ) ? $this->queue_lock_time : 60; // 1 minute
$lock_duration = apply_filters( $this->identifier . '_queue_lock_time', $lock_duration );
set_site_transient( $this->identifier . '_process_lock', microtime(), $lock_duration );
}
/**
* Unlock process
*
* Unlock the process so that other instances can spawn.
*
* @return $this
*/
protected function unlock_process() {
delete_site_transient( $this->identifier . '_process_lock' );
return $this;
}
/**
* Get batch
*
* @return stdClass Return the first batch from the queue
*/
protected function get_batch() {
global $wpdb;
$table = $wpdb->options;
$column = 'option_name';
$key_column = 'option_id';
$value_column = 'option_value';
if ( is_multisite() ) {
$table = $wpdb->sitemeta;
$column = 'meta_key';
$key_column = 'meta_id';
$value_column = 'meta_value';
}
$key = $this->identifier . '_batch_%';
$query = $wpdb->get_row( $wpdb->prepare( "
SELECT *
FROM {$table}
WHERE {$column} LIKE %s
ORDER BY {$key_column} ASC
LIMIT 1
", $key ) );
$batch = new stdClass();
$batch->key = $query->$column;
$batch->data = maybe_unserialize( $query->$value_column );
return $batch;
}
/**
* Handle
*
* Pass each queue item to the task handler, while remaining
* within server memory and time limit constraints.
*/
protected function handle() {
$this->lock_process();
do {
$batch = $this->get_batch();
foreach ( $batch->data as $key => $value ) {
$task = $this->task( $value );
if ( false !== $task ) {
$batch->data[ $key ] = $task;
} else {
unset( $batch->data[ $key ] );
}
if ( $this->time_exceeded() || $this->memory_exceeded() ) {
// Batch limits reached.
break;
}
}
// Update or delete current batch.
if ( ! empty( $batch->data ) ) {
$this->update( $batch->key, $batch->data );
} else {
$this->delete( $batch->key );
}
} while ( ! $this->time_exceeded() && ! $this->memory_exceeded() && ! $this->is_queue_empty() );
$this->unlock_process();
// Start next batch or complete process.
if ( ! $this->is_queue_empty() ) {
$this->dispatch();
} else {
$this->complete();
}
wp_die();
}
/**
* Memory exceeded
*
* Ensures the batch process never exceeds 90%
* of the maximum WordPress memory.
*
* @return bool
*/
protected function memory_exceeded() {
$memory_limit = $this->get_memory_limit() * 0.9; // 90% of max memory
$current_memory = memory_get_usage( true );
$return = false;
if ( $current_memory >= $memory_limit ) {
$return = true;
}
return apply_filters( $this->identifier . '_memory_exceeded', $return );
}
/**
* Get memory limit
*
* @return int
*/
protected function get_memory_limit() {
if ( function_exists( 'ini_get' ) ) {
$memory_limit = ini_get( 'memory_limit' );
} else {
// Sensible default.
$memory_limit = '128M';
}
if ( ! $memory_limit || -1 === $memory_limit ) {
// Unlimited, set to 32GB.
$memory_limit = '32000M';
}
return intval( $memory_limit ) * 1024 * 1024;
}
/**
* Time exceeded.
*
* Ensures the batch never exceeds a sensible time limit.
* A timeout limit of 30s is common on shared hosting.
*
* @return bool
*/
protected function time_exceeded() {
$finish = $this->start_time + apply_filters( $this->identifier . '_default_time_limit', 20 ); // 20 seconds
$return = false;
if ( time() >= $finish ) {
$return = true;
}
return apply_filters( $this->identifier . '_time_exceeded', $return );
}
/**
* Complete.
*
* Override if applicable, but ensure that the below actions are
* performed, or, call parent::complete().
*/
protected function complete() {
// Unschedule the cron healthcheck.
$this->clear_scheduled_event();
}
/**
* Schedule cron healthcheck
*
* @access public
* @param mixed $schedules Schedules.
* @return mixed
*/
public function schedule_cron_healthcheck( $schedules ) {
$interval = apply_filters( $this->identifier . '_cron_interval', 5 );
if ( property_exists( $this, 'cron_interval' ) ) {
$interval = apply_filters( $this->identifier . '_cron_interval', $this->cron_interval );
}
// Adds every 5 minutes to the existing schedules.
$schedules[ $this->identifier . '_cron_interval' ] = array(
'interval' => MINUTE_IN_SECONDS * $interval,
'display' => sprintf( __( 'Every %d minutes', 'woocommerce' ), $interval ),
);
return $schedules;
}
/**
* Handle cron healthcheck
*
* Restart the background process if not already running
* and data exists in the queue.
*/
public function handle_cron_healthcheck() {
if ( $this->is_process_running() ) {
// Background process already running.
exit;
}
if ( $this->is_queue_empty() ) {
// No data to process.
$this->clear_scheduled_event();
exit;
}
$this->handle();
exit;
}
/**
* Schedule event
*/
protected function schedule_event() {
if ( ! wp_next_scheduled( $this->cron_hook_identifier ) ) {
wp_schedule_event( time(), $this->cron_interval_identifier, $this->cron_hook_identifier );
}
}
/**
* Clear scheduled event
*/
protected function clear_scheduled_event() {
$timestamp = wp_next_scheduled( $this->cron_hook_identifier );
if ( $timestamp ) {
wp_unschedule_event( $timestamp, $this->cron_hook_identifier );
}
}
/**
* Cancel Process
*
* Stop processing queue items, clear cronjob and delete batch.
*
*/
public function cancel_process() {
if ( ! $this->is_queue_empty() ) {
$batch = $this->get_batch();
$this->delete( $batch->key );
wp_clear_scheduled_hook( $this->cron_hook_identifier );
}
}
/**
* Task
*
* Override this method to perform any actions required on each
* queue item. Return the modified item for further processing
* in the next pass through. Or, return false to remove the
* item from the queue.
*
* @param mixed $item Queue item to iterate over.
*
* @return mixed
*/
abstract protected function task( $item );
}