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Background tasks

Some operations in Ibexa DXP don’t have to run immediately when a user clicks a button, for example, re-indexing product prices or processing bulk data. Running such operations in real time could slow down the system and disrupt the user experience.

To solve this, Ibexa DXP provides a package called Ibexa Messenger, which is an overlay to Symfony Messenger, and it's job is to queue tasks and run them in the background. Ibexa DXP sends messages (or commands) that represent the work to be done later. These messages are stored in a queue and picked up by a background worker, which ensures that resource-heavy tasks are executed at a convenient time, without putting excessive load on the system.

Ibexa Messenger supports multiple storage backends, such as Doctrine, Redis/Valkey, and PostgreSQL, and gives developers the flexibility to create their own message handlers for custom use cases.

How it works

Ibexa Messenger uses a command bus as a queue that stores messages, or commands, which tell the system what you want to happen, and separates them from the handler, which is the code that actually performs the task.

The process works as follows:

1. A message PHP object is dispatched, for example, ProductPriceReindex.
2. The message is wrapped in an envelope, which may contain additional metadata, called stamps.
3. The message is placed in the transport queue. It can be a Doctrine table, a Redis/Valkey queue, and so on.
4. A worker process continuously reads messages from the queue, pulls them into the default bus ibexa.messenger.bus and assigns them to the right handler.
5. A handler service processes the message (executes the command). You can register multiple handlers for different jobs.

Here is an example of how you can extend your code and use Ibexa Messenger to process your tasks:

Configure package

Create a config file, for example, config/packages/ibexa_messenger.yaml and define your transport:

ibexa_messenger:

    # The DSN of the transport, as expected by Symfony Messenger transport factory.
    transport_dsn:        'doctrine://default?table_name=ibexa_messenger_messages&auto_setup=false'
    deduplication_lock_storage:
        enabled:              true

        # Doctrine DBAL primary connection or custom service
        type:                 doctrine # One of "doctrine"; "custom"; "service"

        # The service ID of a custom Lock Store, if "service" type is selected
        service:              null

        # The DSN of the lock store, if "custom" type is selected
        dsn:                  null

Supported transports

You can define different transports: Ibexa Messenger has been tested to work with Redis, MySQL, PostgreSQL. For more information, see Symfony Messenger documentation or Symfony Messenger tutorial.

Start worker

Use a process manager of your choice to run the following command, or make it start together with the server:

php bin/console messenger:consume ibexa.messenger.transport --bus=ibexa.messenger.bus --siteaccess=<OPTIONAL>

Use the --siteaccess option to set the default SiteAccess and repository for the worker process. The worker uses this SiteAccess for every message that doesn't have a SiteAccessStamp.

If a message has a SiteAccessStamp, the worker uses the SiteAccess from the stamp instead to process this message. Thanks to this, one worker process can handle messages coming from different SiteAccesses.

In multi-repository setups, run one worker process for each repository. With this setup, each worker process can connect to the right database.

Multi-repository setups

Doctrine transport works across multiple repositories without issues, but other transports may need to be adjusted, so that queues across different repositories are not accidentally shared.

Configure for production environment

In production, make sure that Ibexa Messenger keeps running. You can configure a process manager, such as Supervisor or systemd, to restart the worker if it stops.

To prevent issues with memory leaks or stale processes, run the worker with execution limits:

• --limit limits the number of messages the worker processes before exiting.
• --time-limit limits the execution time in seconds before the worker exits.
• --memory-limit restricts the maximum memory usage.

The following example shows how you can specify these limits:

php bin/console messenger:consume ibexa.messenger.transport --bus=ibexa.messenger.bus --limit=100 --time-limit=60 --memory-limit=256M

For more information, see Symfony production recommendation for the Messenger component.

If you deploy your application on Ibexa Cloud, using Workers is recommended.

Dispatch message

To have a task processed in the background by Ibexa Messenger:

1. Inject the ibexa.messenger.bus service as an object implementing the Symfony\Component\Messenger\MessageBusInterface interface. 2. Dispatch an appropriate message, for example a custom message, by using the MessageBusInterface::dispatch() method, exactly as described in Symfony Messenger documentation.

services:
    SomeClassThatSchedulesExecutionInTheBackground:
        arguments:
            $bus: '@ibexa.messenger.bus'

<?php declare(strict_types=1);

namespace App\Dispatcher;

use App\Message\SomeMessage;
use Symfony\Component\Messenger\MessageBusInterface;

final readonly class SomeClassThatSchedulesExecutionInTheBackground
{
    public function __construct(
        private MessageBusInterface $bus,
    ) {
    }

    public function schedule(): void
    {
        $this->bus->dispatch(new SomeMessage());
    }
}

3. Route the message to the background queue. Otherwise the bus calls the handler immediately, in the same process that dispatches the message.

4. Additionally, attach message metadata by using stamps.

Stamps

You can attach Stamps to a message envelope to add additional metadata and control processing of the message.

The ibexa.messenger.bus message bus uses the default Symfony Messenger middleware and doesn't support all stamps that are available in Symfony.

You can use the following Symfony stamps:

• DelayStamp
• DispatchAfterCurrentBusStamp
• HandlerArgumentsStamp
• SerializerStamp

On top of the supported Symfony stamps, Ibexa DXP provides the following ones:

• DeduplicateStamp
• SudoStamp
• UserPermissionStamp
• SiteAccessStamp

DeduplicateStamp

DeduplicateStamp prevents duplicate messages from being processed. When you attach it to a message, the system uses a lock to ensure that only one message with the same key is handled at a time.

For more information, see Symfony documentation about message deduplication.

Caution

The ibexa.messenger.bus bus doesn't support the Symfony\Component\Messenger\Stamp\DeduplicateStamp stamp.

You must use the Ibexa\Contracts\Messenger\Stamp\DeduplicateStamp stamp instead.

The following example shows how you can attach the DeduplicateStamp to the message:

use Ibexa\Contracts\Core\Repository\PermissionResolver;
use Ibexa\Contracts\Messenger\Stamp\UserPermissionStamp;


$deduplicationKey = 'my_message.project.<key_based_on_message>';

SudoStamp

SudoStamp causes the handler to use sudo mode, bypassing all permission checks when processing the message.

It's automatically attached to every dispatched message.

Caution

Starting with Ibexa DXP 5.0.9, the behavior of automatically attaching a SudoStamp to every message is deprecated and will be removed in 6.0. For messages that should be processed without taking permissions into account, always attach the SudoStamp manually to keep your code forward-compatible.

The following example shows how you can attach the SudoStamp to the message:

use Ibexa\Contracts\Messenger\Stamp\DeduplicateStamp;
use Ibexa\Contracts\Messenger\Stamp\UserPermissionStamp;
use Symfony\Component\Messenger\MessageBusInterface;

$this->bus->dispatch(new SomeMessage(), [new UserPermissionStamp($currentUserId)]);

UserPermissionStamp

UserPermissionStamp allows you to set the repository user to process the message. When the user is set, handlers execute actions on their behalf and take their permissions into account.

If you don't attach this stamp, the messages are processed by the default repository user called anonymous user. By combing this stamp with SudoStamp, you can set the repository user and skip the permission checks at the same time.

The following example shows how you can use UserPermissionStamp to preserve the current repository user after the message is dispatched.

use App\Message\SomeMessage;
use Ibexa\Contracts\Messenger\Stamp\SudoStamp;
use Ibexa\Contracts\Messenger\Stamp\UserPermissionStamp;
use Symfony\Component\Messenger\MessageBusInterface;


$currentUserId = $this->permissionResolver->getCurrentUserReference()->getUserId();

SiteAccessStamp

Ibexa\Contracts\Messenger\Stamp\SiteAccessStamp contains the name of the SiteAccess that dispatched the message.

You don't need to add this stamp manually, Ibexa Messenger attaches this stamp to each dispatched message automatically. The stamp contains the SiteAccess that is current at the moment of dispatch.

Before the worker calls the handler, it changes the configuration scope to the SiteAccess from the stamp. The handler then reads SiteAccess-aware configuration for the SiteAccess that dispatched the message, and not for the SiteAccess that the worker process started with.

The stamp doesn't change the current SiteAccess

The stamp changes the configuration scope only. It doesn't change the SiteAccess in the Ibexa\Core\MVC\Symfony\SiteAccess\SiteAccessServiceInterface service. SiteAccessServiceInterface::getCurrent() always returns the SiteAccess that the worker process started with, for all messages.

To get a SiteAccess-aware value in a handler, use the ConfigResolverInterface service.

Extend Ibexa Messenger

To handle a custom use case with background tasks, you need the following elements:

• a message class to hold the data
• a handler class to perform the task, registered on the ibexa.messenger.bus bus
• a message provider to route the message to the transport queue
• code to dispatch the message

If you don't route the message to the transport queue, the bus calls the handler synchronously, in the same process that dispatches the message.

Register custom message and handler

To handle additional use cases with background tasks, first create a custom message and handler class:

<?php declare(strict_types=1);

namespace App\Message;

class SomeMessage
{
    // Add properties and methods as needed for your message.
}

<?php declare(strict_types=1);

namespace App\MessageHandler;

use App\Message\SomeMessage;

final class SomeHandler
{
    public function __invoke(SomeMessage $message): void
    {
        // Handle message.
    }
}

Add a service definition to config/services.yaml and set the bus to ibexa.messenger.bus:

services:
    App\MessageHandler\SomeHandler:
        tags:
            - name: messenger.message_handler
              bus: ibexa.messenger.bus

At this point the handler processes the messages synchronously. To move the work to the background, route the message to the background queue.

Route message to background queue

To process the message in the background, send it to a transport queue. Ibexa Messenger uses message providers instead of Symfony framework.messenger.routing configuration.

A message provider is a service that implements the MessageProviderInterface interface, and the getHandledClasses() method must return the list of message classes that Ibexa Messenger must send to the queue to process in the background.

The getHandledClasses() method can also return a parent class or an interface. In this case, all messages that extend this class, or implement this interface, go to the background queue.

To send SomeMessage to the background queue, create the following provider:

<?php declare(strict_types=1);

namespace App\Messenger;

use App\Message\SomeMessage;
use Ibexa\Contracts\Messenger\Transport\MessageProviderInterface;

final class SomeMessageProvider implements MessageProviderInterface
{
    public function getHandledClasses(): iterable
    {
        return [SomeMessage::class];
    }
}

If you're not using service autoconfiguration, add the ibexa.messenger.sender_message_provider tag to the service:

services:
    App\Messenger\SomeMessageProvider:
        tags:
            - name: ibexa.messenger.sender_message_provider

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