Symfony2, RabbitMQ: I'm lost - symfony

Question

I've installed the RabbitMQ Bundle already. Now here is what I want to do:
Controller: Creates Redis-List, pushes message to client, afterwards send a message into queue, so heavier background task can be executed asynchronously.
But I'm lost.
$msg = array('userid' => $someid);
$this->get('old_sound_rabbit_mq.task_example_producer')->publish(serialize($msg));
This will send some data to a produce? And the according consumer will execute the heavy background task (DB queries etc, based on the "userid" from the producer)? Do I need a callback? What's the queue?! The queue forwards the messages from the producer to the consumer one by one? So can I have multiple consumers to handle more messages at the same time?!

Answer 1

Kinda old post but in case someone else comes looking for help:
It seems that you are using the old_sound's rabbitmq bundle. It has a somewhat helpful tutorial-type of documentation here: https://github.com/videlalvaro/RabbitMqBundle
It helped me get going with rabbitmq in symfony.
In a nutshell:
1: You need to have some configration in the config.yml-file. For example:
# RabbitMQ Configuration
old_sound_rabbit_mq:
connections:
default:
host: 'localhost'
port: 5672
user: 'guest'
password: 'guest'
vhost: '/'
lazy: true
connection_timeout: 3
read_write_timeout: 3
# requires php-amqplib v2.4.1+ and PHP5.4+
keepalive: false
# requires php-amqplib v2.4.1+
heartbeat: 0
producers:
task_example:
connection: default
exchange_options: {name: 'task_example', type: direct}
consumers:
task_example:
connection: default
exchange_options: {name: 'task_example', type: direct}
queue_options: {name: 'task_example'}
callback: test_class
Here the connection is defined, and one producer and one consumer. Both use the same "default" connection.
You will also need to define the callback as a service:
# My services
services:
test_class:
class: AppBundle\Testclasses\rabbittest\testclass
arguments: [#logger]
2: Now you need to have the consumer, which is the callback-option here, the "test_class". Simple consumer could look like this:
namespace AppBundle\Testclasses\rabbittest;
use OldSound\RabbitMqBundle\RabbitMq\ConsumerInterface;
use PhpAmqpLib\Message\AMQPMessage;
class testclass implements ConsumerInterface
{
private $logger; // Monolog-logger.
// Init:
public function __construct( $logger )
{
$this->logger = $logger;
echo "testclass is listening...";
}
public function execute(AMQPMessage $msg)
{
$message = unserialize($msg->body);
$userid = $message['userid'];
// Do something with the data. Save to db, write a log, whatever.
}
}
3: And now the producer that you already had:
$msg = array('userid' => $someid);
$this->get('old_sound_rabbit_mq.task_example_producer')->publish(serialize($msg));
4: And final piece of the puzzle is running the consumer. Consumer is started from the console, I was developing in a windows machine, and used Windows PowerShell. You can start up the consumer like this:
php app/console rabbitmq:consumer task_example
And it should give you the text:
testclass is listening...
, if you copied that from this example. That text is not necessary, and without it, the console will output nothing but will work just fine. Unless some error is presented.
But remember that you have to be in the directory where your symfony-application is. For example:
C:\wamp\www\symfony\my_project

Answer 2

A queue is a list of messages you want processed.
An exchange is a router of messages to queues. (you can have multiple queues listing to the same exchange, for example).
A producer pushes messages to an exchange.
A consumer reads messages from the queue.
Normally you have one producer and many consumers to process the messages in parallel.
The code you posted demonstrates a producer publishing to an exchange.

Answer 3

RabbitMQBundle expects you to have in-depth knowledge of the broker internals. That's not always what you want.
There is a solution that hides all those nitty-gritty details, leaving a simple but yet powerful interface for you to use. The doc is short. If you follow it you get working solution with zero knowledge of how RabbitMQ actually works.
P.S. Here's the blog post on how to migrate from RabbitMQBundle to EnqueueBundle.