predis.md

Predis queue

Queues are designed to distribute the load and delay execution of commands or transfer their execution to separate processes.

The queue stores events in Redis, using the Predis library to access it.

Predis must be installed separately with Composer:

composer require predis/predis

This queue uses a serializer to convert command objects to strings and back while waiting for the transport of objects across the Redis. The serializer uses the predis format as a default. You can change format if you need. You can make messages more optimal for a Redis than JSON.

If the message could not be deserialized, then a critical message is written to the log so that the administrator can react quickly to the problem and the message is placed again at the end of the queue, so as not to lose it.

Configure queue:

use GpsLab\Component\Command\Queue\Pull\PredisPullCommandQueue;
use GpsLab\Component\Command\Queue\Serializer\SymfonySerializer;
use Symfony\Component\Serializer\Serializer;
use Predis\Client;

//$predis = new Client('tcp://10.0.0.1:6379'); // Predis client
//$symfony_serializer = new Serializer(); // Symfony serializer
//$logger = new Logger(); // PSR-3 logger
$queue_name = 'article_queue';
$format = 'json'; // default: predis
// you can create another implementation of serializer
$serializer = new SymfonySerializer($symfony_serializer, $format);
$queue = new PredisPullCommandQueue($predis, $serializer, $logger, $queue_name);

Make command and publish it into queue:

$command = new RenameArticleCommand();
$command->new_name = $new_name;

$queue->publish($command);

In latter pull commands from queue:

use GpsLab\Component\Command\Bus\HandlerLocatedCommandBus;
use GpsLab\Component\Command\Handler\Locator\DirectBindingCommandHandlerLocator;

$locator = new DirectBindingCommandHandlerLocator();
$bus = new HandlerLocatedCommandBus($locator);

while ($command = $queue->pull()) {
    $bus->handle($command);
}