README

Yii Mutex

This package provides mutex implementation and allows mutual execution of concurrent processes in order to prevent "race conditions".

This is achieved by using a "lock" mechanism. Each possibly concurrent processes cooperates by acquiring a lock before accessing the corresponding data.

Requirements

PHP 7.4 or higher.

Installation

The package could be installed with composer:

composer require yiisoft/mutex --prefer-dist

Usage

There are multiple ways you can use the package. You can execute a callback in a synchronized mode i.e. only a single instance of the callback is executed at the same time:

/** @var \Yiisoft\Mutex\Synchronizer $synchronizer */
$newCount = $synchronizer->execute('critical', function () {
    return $counter->increase();
}, 10);

Another way is to manually open and close mutex:

/** @var \Yiisoft\Mutex\SimpleMutex $simpleMutex */
if (!$simpleMutex->acquire('critical', 10)) {
    throw new \Yiisoft\Mutex\Exception\MutexLockedException('Unable to acquire the "critical" mutex.');
}
$newCount = $counter->increase();
$simpleMutex->release('critical');

It could be done on lower level:

/** @var \Yiisoft\Mutex\MutexFactoryInterface $mutexFactory */
$mutex = $mutexFactory->createAndAcquire('critical', 10);
$newCount = $counter->increase();
$mutex->release();

And if you want even more control, you can acquire mutex manually:

/** @var \Yiisoft\Mutex\MutexFactoryInterface $mutexFactory */
$mutex = $mutexFactory->create('critical');
if (!$mutex->acquire(10)) {
    throw new \Yiisoft\Mutex\Exception\MutexLockedException('Unable to acquire the "critical" mutex.');
}
$newCount = $counter->increase();
$mutex->release();

Mutex drivers

There are some mutex drivers available as separate packages:

If you want to provide your own driver, you need to implement MutexFactoryInterface and MutexInterface. There is ready to extend Mutex, MutexFactory and a RetryAcquireTrait that contains retryAcquire() method implementing the "wait for a lock for a certain time" functionality.

When implementing your own drivers, you need to take care of automatic unlocking. For example using a destructor:

public function __destruct()
{
    $this->release();
}

and shutdown function:

public function __construct()
{
    register_shutdown_function(function () {
        $this->release();
    });
}

Note that you should not call the exit() or die() functions in the destructor or shutdown function. Since calling these functions in the destructor and shutdown function will prevent all subsequent completion functions from executing.