predis_unique.md

Predis unique queue

It works just like the Predis queue, but it only allows storing unique commands. All duplicates will be ignored.

What is it for

A queue of unique commands is needed when you need to perform an action once after a domain event. But since there can be many domain events, and the action must be performed only once, you need to remove all duplicate actions from the queue.

Examples:

• Action: Update a block of popular articles
• Event: View article

Views come regularly, and the block needs to be updated no more often than 10 minutes. If there are no views, then there is no need to update the block.

Usage

Configure queue:

use GpsLab\Component\Command\Queue\Pull\PredisUniquePullCommandQueue;
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);
$queue = new PredisUniquePullCommandQueue($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);
}