async_message_producer.md

Async Message Producer

Messaging becomes really interesting if you process your messages asynchronously. Prooph Service Bus can hide such an asynchronous workflow behind a unified interface. You can start with synchronous message dispatching by routing your messages directly to message handlers and if you later want to improve response times you can switch to async processing on a per message basis by routing the appropriate messages to a message producer which hands them over to a messaging system like RabbitMQ, ZeroMQ, Gearman, Beanstalkd or any other queue.

Available MessageProducer

• BernardProducer: Queue multi-backend providing different drivers like Doctrine DBAL and Predis (see https://github.com/bernardphp/bernard for a complete list of drivers)
• GuzzleHttpProducer: Send messages to a remote system using HTTP
• ZeroMQProducer: Async message handling using super fast and simple to set up ZeroMQ
• HumusAmqpProducer: Async handling using amqp protocol (f.e. with RabbitMQ). This also includes JSON-RPC features.
• EnqueueProducer: Async handling using Enqueue MQ library.

Usage

If you want to set up a bus that handles all messages asynchronously you can do so by attaching a Prooph\ServiceBus\Plugin\MessageProducerPlugin initialized with your message producer of choice to a message bus.

Let's look at a simple example using the psb-zeromq-producer

//app bootstrap
$container = new Container;
$container['config'] = [
    'prooph' => [
        'zeromq_producer' => [
            'dsn' => 'tcp://127.0.0.1:5555', // ZMQ Server Address.
            'persistent_id' => 'example', // ZMQ Persistent ID to keep connections alive between requests.
            'rpc' => false, // Use as Query Bus.
        ]
    ]
];

$factory = \Prooph\ServiceBus\Message\ZeroMQ\Container\ZeroMQMessageProducerFactory;
$zmqProducer = $factory($container);

$commandBus = new \Prooph\ServiceBus\CommandBus();

$messageProducerForwarder = new \Prooph\ServiceBus\Plugin\MessageProducerPlugin($zmqProducer);

$messageProducerForwarder->attachToMessageBus($commandBus);

$echoText = new ExampleCommand('It works');
$commandBus->dispatch($echoText);

You can also route individual messages to message producers by using a message router plugin.

Note: Prooph\ServiceBus\Plugin\Router\RegexRouter is a good choice if you want to handle all messages of a specific namespace async.

Async Querying

An async message producer for the QueryBus needs to provide a response by resolving the input React\Promise\Deferred. When using a messaging system like ZeroMQ for example you can make use of request/response mode or RPC mode. HTTP APIs provide responses naturally. So these are both good candidates to use for remote querying.