wikimedia/mediawiki-extensions-Translate

<?php
declare( strict_types = 1 );

namespace MediaWiki\Extension\Translate\Utilities;

use MediaWiki\MediaWikiServices;

/**
 * Helper class for maintenance scripts to run things in parallel.
 *
 * See also ForkContoller and https://phabricator.wikimedia.org/T201970.
 *
 * @since 2020.11
 * @license GPL-2.0-or-later
 * @author Niklas Laxström
 */
class ParallelExecutor {
    /** @var true[] */
    private $pids = [];
    /** @var int */
    private $threads;

    public function __construct( int $threads = 1 ) {
        $this->threads = $threads;
    }

    public function runInParallel( callable $mainThread, callable $forkThread ): void {
        // Fork to increase speed with parallelism. Also helps with memory usage if there are leaks.
        $pid = -1;
        if ( function_exists( 'pcntl_fork' ) ) {
            $pid = pcntl_fork();
        }

        if ( $pid === 0 ) {
            MediaWikiServices::resetChildProcessServices();
            $forkThread();
            exit();
        } elseif ( $pid === -1 ) {
            // Fork failed do it serialized
            $forkThread();
        } else {
            // Main thread
            $mainThread( $pid );
            $this->pids[$pid] = true;

            // If we hit the thread limit, wait for any child to finish.
            if ( count( $this->pids ) >= $this->threads ) {
                $status = 0;
                $pid = pcntl_wait( $status );
                unset( $this->pids[$pid] );
            }
        }
    }
}