CAPL

Comuto Asynchronous Process Launcher/Consumer

• CAPL is a command used internally by BlaBlaCar to launch a worker for consuming an AMQP Queue from RabbitMQ.
• CAPL doesn't manage process creation, it is based on Symfony/Command component and SupervisorD is used for process management.
• CAPL is based on ext/amqp from pecl PHP. Please, use the latest version as this lib still has bugs and is under development.

Details

Let's explain what are the problems we met so that you understand the design rules and the architecture that led to our code.

• We actually only use "direct" exchanges
• We publish "Message" (Capl\AMQP\Message\Message.php), this is an abstract view of our business stuff, it contains data such as 'branding' and 'media' which are used by CAPL to boot some Symfony Kernels.
  • Then the Message contains the Payload and the 'processor' which is just a string naming a service that will handle that message in the dispatched Kernel's DIC and be passed the Payload as incoming data.
• Kernels have to implement our CaplKernelInterface, this is the code we have in our kernel :

    public function getAsyncMessageProcessor($processorName)
    {
        $processorId = "comuto.amqp.processor.$processorName";
        if (!$this->container->has($processorId)) {
            throw new \RuntimeException("Service $processorId not found");
        }

        return $this->container->get($processorId);
    }

CAPL Command workflow

• Parse config, find AMQP adapter credentials, connect, use a logger (GrayLog of file based)
• Read the queue name from command line, then listen to it
• When message comes :
  • Unserialize it
  • Check the validity (is it a Capl\AMQP\Message\Message ?)
  • Calls the processor
    • Boots the right Kernel depending on 'branding' and 'media' found into the Message
    • Gets the DIC service that can process the message
    • Process message passing it payload
• ACK if no exception
• NACK if exception (requeued in a Dead Letter Queue) and log exception

Documentation

RabbitMQ Getting started : http://www.rabbitmq.com/getstarted.html ext/amqp : http://pecl.php.net/package/amqp librabbitmq : http://hg.rabbitmq.com/rabbitmq-c/ supervisor: http://supervisord.org/

Licence

See Licence

Warning: We distribute this project as is. It may not have been designed for distribution, though may not be usable as is.