appserver-io/concurrency

It introduces abstract services and objects that provides easy handling for thread-safety, concurrency and sharing.

0.3.0 2015-06-24 14:46 UTC

README

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What is it?

The concurrency toolkit introduces abstract services and objects that provides easy handling for thread-safety, concurrency programming and data sharing all written in PHP-Userland.

Why?

If you are implementing multithreaded functionality you're always fighting against the same problems called Race-Conditions, Deadlocks etc... When sharing simple data or even plain PHP objects between threads you have to make sure, that everything is synchronized (Thread-safe) in any logic of your code. This Toolkit mostly helps you to avoid those problems by providing abstract services and object written in PHP-Userland.

How to use?

This toolkit is in early-stage development. Please use with caution.

The ExecutorService

It allows you to hold plain PHP objects persistent as singleton in memory accessible everywhere in your code even in different thread contexts. You can keep those plain PHP objects easily thread-safe or call certain methods asynchronous by using simple annotations like @Synchronized or @Asynchronous in method docblocks.

How it works

If you want to use the concurrency toolkit in your project you have to add it to the composer dependencies composer.json and do a composer update afterwards.

{
    "require": {
        "appserver-io/concurrency": "~0.2"
    },
}

At first you have to initialise the ExecutorService in a main PHP script main.php.

<?php

define(AUTOLOADER, 'vendor/autoload.php');
require_once(AUTOLOADER);

// init executor service
\AppserverIo\Concurrecy\ExecutorService::__init(AUTOLOADER);

Lets say you want to build a simple storage PHP object to share data all over your multithreaded implementations. The storage object could look like this. Create Storage.php and add:

<?php

class Storage
{
    public $data = array();

    /**
     * @Synchronized
     */
    public function all() {
        return $this->data;
    }

    /**
     * @Synchronized
     */
    public function set($key, $value) {
        $this->data[$key] = $value;
    }

    /**
     * @Synchronized
     */
    public function get($key) {
        if ($this->has($key)) {
            return $this->data[$key];
        }
    }

    /**
     * @Synchronized
     */
    public function has($key) {
        return isset($this->data[$key]);
    }

    /**
     * @Synchronized
     */
    public function del($key) {
        unset($this->data[$key]);
    }

    /**
     * @Synchronized
     */
    public function inc($key) {
        if ($this->has($key)) {
            ++$this->data[$key];
        }
    }

    /**
     * @Asynchronous
     */
    public function dump() {
        echo var_export($this->all(), true) . PHP_EOL;
    }
}

Maybe you've noticed the method docblock annotations we used here. Methods marked with @Synchronized can not be called more than once at the same time. That means the $data array will always be synchronized when using all(), set(), get(), del() or inc(). Methods using @Asynchronous are called asynchronously. So if the dump() method is called it will dump the $data array while not blocking your main logic execution.

To make use of the storage object we have to create a multithreaded task simulation that should represent multithreaded business logic. So create Task.php and add:

<?php
class Task extends Thread {

    public static function simulate($maxThreads) {
        $t = array();
        for ($i=0; $i<$maxThreads; $i++) {
            $t[$i] = new self();
            $t[$i]->start(PTHREADS_INHERIT_ALL | PTHREADS_ALLOW_GLOBALS);
        }
        for ($i=0; $i<$maxThreads; $i++) {
            $t[$i]->join();
        }
    }

    public function run() {
        // get the storage object
        $storage = \AppserverIo\Concurrency\ExecutorService::__getEntity('data');
        // add thread signature
        $storage->set($this->getThreadId(), __METHOD__);
        // increase internal counter
        $storage->inc('counter');
    }
}

Now bring all together and enhance the main script main.php:

<?php

define('AUTOLOADER', 'vendor/autoload.php');
require_once(AUTOLOADER);
require_once('Storage.php');
require_once('Task.php');

use \AppserverIo\Concurrency\ExecutorService as ExS;

// init executor service
ExS\Core::init(AUTOLOADER);

// create storage instance with alias data
$data = ExS\Core::newFromEntity('Storage', 'data');

// preinit counter
$data->set('counter', 0);

// simulate multithreaded tasks
Task::simulate(10);

// dump data async
$data->dump();

echo 'finished' . PHP_EOL;

// shutdown executor service and its entities
ExS\Core::shutdown();

If you call main.php with a thread-safe compiled php version where pthreads ext is installed as it`s provided by appserver.io runtime for example the result should look like this:

$ /opt/appserver/bin/php bootstrap.php 
finished
array (
  'counter' => 10,
  140470559000320 => 'Task::run',
  140470550284032 => 'Task::run',
  140470541891328 => 'Task::run',
  140470327965440 => 'Task::run',
  140470319572736 => 'Task::run',
  140470311180032 => 'Task::run',
  140470302787328 => 'Task::run',
  140470294394624 => 'Task::run',
  140470286001920 => 'Task::run',
  140470277609216 => 'Task::run',
)

The executor service has some internal function as described here:

Method Description
__return Returns the plain entity object from executor thread context if its serializable in its actual state
__invoke(closure) Executes the callable in executor thread context. It will provide $self as function argument which references the plain entity object. Example usage:
$executorServiceEntity->__invoke(function($self) { $self->doSomething() }); 
__reset() Resets the plaing entity object in executor service context
__shutdown() Shutdown the executor service thread

Issues

In order to bundle our efforts we would like to collect all issues regarding this package in the main project repository's issue tracker. Please reference the originating repository as the first element of the issue title e.g.: [appserver-io/<ORIGINATING_REPO>] A issue I am having