mehr-it/system-broadcast

Broadcast library for internal communication in distributed systems using Redis

1.0.0 2019-05-20 21:25 UTC

Requires

• php: ^7.0
• predis/predis: ^1.1

Requires (Dev)

• phpunit/phpunit: ^7.4
• spatie/async: ^1.0

MIT

• Christopher Mieger

• redis
• system
• Broadcast
• internal
• distributed systems
• distributed system

README

This package implements internal broadcasting for distributed systems using Redis.

Internally Redis publish/subscribe commands are used. This library offers an easy interface for publishing and receiving messages and provides a mechanism to check whether some messages were missed while the broadcast channel was not subscribed.

Basic usage

Implementing a publisher is very easy:

$broadcast = new SystemBroadcast(['host' => '127.0.0.1'], 'my-channel');
$broadcast->publish('my-message');

The corresponding listener would look like this:

$broadcast = new SystemBroadcast(['host' => '127.0.0.1'], 'my-channel');
$broadcast->handler('my-message', function() {
	// do something
})
$broadcast->listen();

Passing data together with messages

You may pass any JSON serializable data together with messages:

$broadcast->publish('my-message', $data);

The handler will receive the data as first parameter:

$broadcast->handler('my-message', function($data) {
	// do something
})

Missed messages

While listening for broadcasts, listeners receive all messages. However if your listener process is not running for whatever reason, all messages published meanwhile are irrevocably lost for this client.

Even if you cannot recover missed messages, you can check if you missed any published messages on the broadcast channel. Your handler can receive a sequence value and save it to a file:

$broadcast->handler('my-message', function($data, $broadcast) {
	$seq = $broadcast->sequence();
	
	/* ... save it to file */
})

Before you start listening, you can register an onListen-callback, which receives the current sequence value right after listening is established. If this value does not equal the last value stored by the handler, you missed some messages:

$broadcast->onListen(function($sequence) {

	$expected = /* ... load last sequence value from file */
	
	if ($sequence != $expected) {
		/* handle inconsitency */
	}

});

Signing messages

Since messages can be very critical, you may sign messages. To do so, use the setSignKey method to set the same secret for publishers and listeners.

See class documentation for additional signing parameters.