Message Queue

What is the Message Queue

Shopware uses the Symfony Messenger component and Enqueue to handle asynchronous messages. This allows tasks to be processed in the background. Thus, tasks can be processed independently of timeouts or system crashes. By default, tasks in Shopware are stored in the database and processed via the browser, as long as you are logged into the administration. This is a simple and fast method for the development process, but not recommended for production systems. With multiple users logged into the administration, this can lead to high CPU load and interfere with the smooth execution of PHP FPM.

Message Queue on production systems

On a productive system, the message queue should not be processed via the browser in the administration, but via the CLI. This way, tasks are also completed when no one is logged into the administration and high CPU load due to multiple users in the admin is also avoided. Furthermore you can change the transport to another system like RabbitMQ for example. This would on the one hand relieve the database and on the other hand use a much more specialized service for handling message queues. The following are examples of the steps needed.

Consuming Messages

The recommended method for consuming messages is using the cli worker.

Cli worker

You can configure the command just to run a certain amount of time or to stop if it exceeds a certain memory limit like: ```shell script bin/console messenger:consume-messages default --time-limit=60

```shell script
bin/console messenger:consume-messages default --memory-limit=128M

For more information about the command and its configuration use the -h option: ```shell script bin/console messenger:consume-messages -h

You should use the limit option to periodically restart the worker processes, because of the memory leak issues of long-running php processes. To automatically start the processes again after they stopped because of exceeding the given limits you can use something like [upstart](http://upstart.ubuntu.com/getting-started.html) or [supervisor](http://supervisord.org/running.html). Alternatively you can configure a cron job that runs the command again shortly after the time limit exceeds.
If you have configured the cli-worker, you can turn off the admin worker in the shopware configuration file, therefore create or edit the configuration `shopware.yaml`.

```yaml
# config/packages/shopware.yaml
shopware:
    admin_worker:
        enable_admin_worker: false

Admin worker

The admin-worker, if used, can be configured in the general shopware.yml configuration. If you want to use the admin worker you have to specify each transport, that previously was configured. The poll interval is the time in seconds that the admin-worker polls messages from the queue. After the poll-interval is over the request terminates and the administration initiates a new request.

# config/packages/shopware.yaml
shopware:
    admin_worker:
        enable_admin_worker: true
        poll_interval: 30
        transports: ["default"]

Transport: RabbitMQ example

In this example we replace the standard transport, which stores the messages in the database, with RabbitMQ. Of course, other transports can be used as well. A detailed documentation of the parameters and possibilities can be found in the enqueue symfony documentation. In the following I assume that RabbitMQ is installed and started. Furthermore, a queue, here called shopware-queue, should be created inside RabbitMQ. The only thing left is to tell shopware about the new transport. Therefore we edit/create the configuration file enqueue.yaml with the following content:

# config/packages/enqueue.yaml
enqueue:
    rabbitmq:
        transport:
            dsn: "amqp://guest:guest@rabbitmq:5672/%2F?connection_timeout=1000&heartbeat=100"
        client: ~

Be sure to replace the login credentials, host and port with your correct parameters in the connection string. And now we activate that transport and replace the default one of shopware. This can be done by editing/creating the file framework.yaml.

# config/packages/framework.yaml
framework:
    messenger:
        transports:
            default:
                dsn: "enqueue://rabbitmq?queue[name]=shopware-queue"

Notice that shopware-queue is the name of the previously created queue in RabbitMQ. Also rabbitmq matches the name of the new transport in the previously created enqueue.yaml.