EventLoop Component

Event loop abstraction layer that libraries can use for evented I/O.

Table of Contents

• Quickstart example
• Usage
• Loop implementations
• Install
• Tests
• License

Quickstart example

Here is an async HTTP server built with just the event loop.

$loop = React\EventLoop\Factory::create();

$server = stream_socket_server('tcp://127.0.0.1:8080');
stream_set_blocking($server, 0);

$loop->addReadStream($server, function ($server) use ($loop) {
    $conn = stream_socket_accept($server);
    $data = "HTTP/1.1 200 OK\r\nContent-Length: 3\r\n\r\nHi\n";
    $loop->addWriteStream($conn, function ($conn) use (&$data, $loop) {
        $written = fwrite($conn, $data);
        if ($written === strlen($data)) {
            fclose($conn);
            $loop->removeStream($conn);
        } else {
            $data = substr($data, $written);
        }
    });
});

$loop->addPeriodicTimer(5, function () {
    $memory = memory_get_usage() / 1024;
    $formatted = number_format($memory, 3).'K';
    echo "Current memory usage: {$formatted}\n";
});

$loop->run();

Usage

In order for async based libraries to be interoperable, they need to use the same event loop. This component provides a common LoopInterface that any library can target. This allows them to be used in the same loop, with one single run() call that is controlled by the user.

// [1]
$loop = React\EventLoop\Factory::create();

// [2]
$loop->addPeriodicTimer(1, function () {
    echo "Tick\n";
});

$stream = new React\Stream\ReadableResourceStream(
    fopen('file.txt', 'r'),
    $loop
);

// [3]
$loop->run();

1. The loop instance is created at the beginning of the program. A convenience factory React\EventLoop\Factory::create() is provided by this library which picks the best available loop implementation.
2. The loop instance is used directly or passed to library and application code. In this example, a periodic timer is registered with the event loop which simply outputs Tick every second and a readable stream is created by using ReactPHP's stream component for demonstration purposes.
3. The loop is run with a single $loop->run() call at the end of the program.

Loop implementations

In addition to the interface there are the following implementations provided:

• StreamSelectLoop: This is the only implementation which works out of the box with PHP. It does a simple select system call. It's not the most performant of loops, but still does the job quite well.

• LibEventLoop: This uses the libevent pecl extension. libevent itself supports a number of system-specific backends (epoll, kqueue).

• LibEvLoop: This uses the libev pecl extension (github). It supports the same backends as libevent.

• ExtEventLoop: This uses the event pecl extension. It supports the same backends as libevent.

All of the loops support these features:

• File descriptor polling
• One-off timers
• Periodic timers
• Deferred execution of callbacks

Install

The recommended way to install this library is through Composer. New to Composer?

This will install the latest supported version:

$ composer require react/event-loop

Tests

To run the test suite, you first need to clone this repo and then install all dependencies through Composer:

$ composer install

To run the test suite, go to the project root and run:

$ php vendor/bin/phpunit

License

MIT, see LICENSE file.