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How To Use RabbitMQ With Symfony Messenger

13 mai 2020

In this article I will first explain how the queues work and in the second part we will install Symfony, messenger component and rabbitMQ and we will create a simple project example of product order basket in the store.

As a rule, new queue items are added as last ones (enqueue) and then they are removed as they move to the beginning of a queue (dequeue).

(First In, First Out, FIFO)

Type of queue:

  • Cyclic
  • Double-sided
  • Priority

Cyclic queue has a wheel structure, if it comes down to the last element of the list it automatically starts from the beginning.

Double-sided queue – both sides can be used for adding as well as deleting nodes.

In case of priority queue, elements are added according to a given pre-defined priority which means that element with a higher priority will be moved up higher in a hierarchy and will be serviced earlier, not like in a classic queue when it is added up to the end of a queue.

The examples of such queues are the services with free accounts and fee-paying subscribed accounts, or insurance application where you report a damage and it is pre-defined that more serious damages (like accidents) are serviced with a higher priority than just regular bumps.

Symfony Messenger

Main concepts:

  • Message – any object
  • Bus – dispatching messages
  • Message Handler – processes for servicing messages
  • Transport – sending and receiving messages, sending to queues for example via RabbitMQ
  • Worker – processing and consuming messages

Stack: Symfony 4.3.11, PHP 7.3.16, MySQL 5.7.29

  1. Create a project with the following command.
    composer create-project symfony/website-skeleton queue-project «4.3.*»
  2. Start the server with the command.
    bin/console server:run
  3. Install Messenger component.
    composer require symfony/messenger
  4. Create controller.
    bin/console make:controller
  5. In method basket messages are dispatching.
    <?php
    declare(strict_types=1);
    
    namespace AppController;
    
    use AppMessageCommandOrderProduct;
    use SymfonyBundleFrameworkBundleControllerAbstractController;
    use SymfonyComponentHttpFoundationResponse;
    use SymfonyComponentMessengerMessageBusInterface;
    use SymfonyComponentRoutingAnnotationRoute;
    
    class ShopBasketController extends AbstractController
    {
        private $messageBus;
    
        /**
         * ShopBasketController constructor.
         * @param MessageBusInterface $messageBus
         */
        public function __construct(MessageBusInterface $messageBus)
        {
            $this->messageBus = $messageBus;
        }
    
        /**
         * @Route("/", name="shop")
         */
        public function index(): Response
        {
            return $this->render('shop_basket/index.html.twig', [
                'controller_name' => 'ShopBasketController',
            ]);
        }
    
        /**
         * @Route("/shop/basket", name="shop_basket")
         * @throws Exception
         */
        public function basket(): Response
        {
            $productNumber = 1;
            $productAmount = 9.90;
    
            try {
                $this->messageBus->dispatch(
                    new OrderProduct($productNumber, $productAmount
                    ));
            } catch (Exception $exception) {
                throw new Exception('Error buy product.');
            }
    
            return new Response(sprintf(
                ' success add to basket!' . self::randProduct()
            ));
        }
    
        public function randProduct()
        {
            define('PRODUCTS', [
                'Backpack',
                'Cap',
                'Bag'
            ]);
            echo PRODUCTS[array_rand(PRODUCTS)];
        }
    }
  6. Next, we create OrderProductHandler. This handler evokes $orderProduct, and in example time interval 9 second, it consumes messages. Here your domain logic is located.
    <?php
    declare(strict_types=1);
    
    namespace AppMessageHandlerCommand;
    
    use AppMessageCommandOrderProduct;
    use SymfonyComponentMessengerHandlerMessageHandlerInterface;
    
    final class OrderProductHandler implements MessageHandlerInterface
    {
        public function __invoke(OrderProduct $orderProduct)
        {
            sleep(9);
            var_dump($orderProduct);
        }
    }
  7. Create directory Message/Command and PHP class OrderProduct. This is a class where there is a PHP object that can be handled by a handler.
    <?php
    declare(strict_types=1);
    
    namespace AppMessageCommand;
    
    
    class OrderProduct
    {
        private $productNumber;
        private $productAmount;
    
        public function __construct(int $productNumber, float    $productAmount)
        {
            $this->productNumber = $productNumber;
            $this->productAmount = $productAmount;
        }
    
        public function getProductNumber(): int
        {
            return $this->productNumber;
        }
    
        public function getProductAmount(): float
        {
            return $this->productAmount;
        }
    }
  8. Register handler.
    #config/service.yaml
    AppMessageHandler:
        resource: '../src/MessageHandler'
        tags: ['messenger.message_handler']
  9. Doctrine transport configuration.
    #config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                 async:
                   dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
            routing:
                 'AppMessageCommandOrderProduct': async
  10. We also need to define the messenger transport. Doctrine transport was introduced in Symfony 4.3.
    #.env
    MESSENGER_TRANSPORT_DSN=doctrine://default
  11. The following command will consume the messages from the queue.
    bin/console messenger:consum
  1. Then install RabbitMQ, login and password default is guest/guest.
    brew install rabbitmq
    brew services start rabbitmq
    http://localhost:15672/
  2. You still need to install AMQP transport and add to php.ini extension=amqp.so (configuration below it works on Symfony 4.2).
    composer require symfony/amqp-pack
  3. Define the transport.
    #.env
    MESSENGER_TRANSPORT_DSN=amqp://guest:guest@localhost:5672///messages
  4. In case of RabbitMQ transport, the remaining part of its configuration is analogous to Doctrine transport.
    config/packages/messenger.yaml
    framework:
        messenger:
          transports:
              amqp: '%env(MESSENGER_TRANSPORT_DSN)%'
    
          routing:
            'AppMessageCommandOrderProduct': amqp

Summary

You have learned the Messenger component. We used the two transports Doctrine and RabbitMQ.

 

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