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Requirements | Installation | Usage

A simple library to make forking a processes as easy as possible.

thelevti/phpfork follows semantic versioning. Read more on semver.org.

Requirements

PHP 7.2 or above
php-pcntl to allow this library forking processes.
php-posix to allow this library getting process information.
php-shmop to allow this library doing interprocess communication.

Installation

Composer

To use this library with composer, run the following terminal command inside your repository's root folder.

composer require "thelevti/phpfork"

Usage

This library uses the namespace TheLevti\phpfork.

Example: Basic process forking

<?php

use TheLevti\phpfork\Fork;
use TheLevti\phpfork\ProcessManager;
use TheLevti\phpfork\SharedMemory;

$manager = new ProcessManager();
$fork = $manager->fork(function (SharedMemory $shm) {
    // Do something in a forked process!
    return 'Hello from ' . posix_getpid();
})->then(function (Fork $fork) {
    // Do something in the parent process when the fork is done!
    echo "{$fork->getPid()} says '{$fork->getResult()}'\n";
});

$manager->wait();

Example: Upload images to a CDN

Feed an iterator into the process manager and it will break the job into multiple batches and spread them across many processes.

<?php

use TheLevti\phpfork\ProcessManager;
use SplFileInfo;

$files = new RecursiveDirectoryIterator('/path/to/images');
$files = new RecursiveIteratorIterator($files);

$manager = new ProcessManager();
$batchJob = $manager->process($files, function(SplFileInfo $file) {
    // upload this file
});

$manager->wait();

Example: Working with Doctrine DBAL

When working with database connections, there is a known issue regarding parent/child processes. See php doc for pcntl_fork:

The reason for the MySQL "Lost Connection during query" issue when forking is the fact that the child process inherits the parent's database connection. When the child exits, the connection is closed. If the parent is performing a query at this very moment, it is doing it on an already closed connection, hence the error.

This will mean that in our example, we will see a SQLSTATE[HY000]: General error: 2006 MySQL server has gone away exception being thrown in the parent process.

One work-around for this situation is to force-close the DB connection before forking, by using the PRE_FORK event.

<?php

use Doctrine\DBAL\DriverManager;
use TheLevti\phpfork\Batch\Strategy\ChunkStrategy;
use TheLevti\phpfork\EventDispatcher\Events;
use TheLevti\phpfork\EventDispatcher\SignalEventDispatcher;
use TheLevti\phpfork\ProcessManager;

$params = array(
    'dbname'    => '...',
    'user'      => '...',
    'password'  => '...',
    'host'      => '...',
    'driver'    => 'pdo_mysql',
);

$forks = 4;
$dataArray = range(0, 15);

$callback = function ($value) use ($params) {
    // Child process acquires its own DB connection
    $conn = DriverManager::getConnection($params);
    $conn->connect();

    $sql = 'SELECT NOW() AS now';
    $stmt = $conn->prepare($sql);
    $stmt->execute();
    $dbResult = $stmt->fetch();
    $conn->close();

    return ['pid' => getmypid(), 'value' => $value, 'result' => $dbResult];
};

// Get DB connection in parent
$parentConnection = DriverManager::getConnection($params);
$parentConnection->connect();

$dispatcher = new SignalEventDispatcher();
$dispatcher->addListener(Events::PRE_FORK, function () use ($parentConnection) {
    $parentConnection->close();
});

$manager = new ProcessManager($dispatcher, null, true);

/** @var TheLevti\phpfork\Fork $fork */
$fork = $manager->process($dataArray, $callback, new ChunkStrategy($forks));
$manager->wait();

$result = $fork->getResult();

// Safe to use now
$sql = 'SELECT NOW() AS now_parent';
$stmt = $parentConnection->prepare($sql);
$stmt->execute();
$dbResult = $stmt->fetch();
$parentConnection->close();

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