ParallelExecutor.php
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ParallelExecutor.php
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	<?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] );
	}
	}
	}
	}