Messenger: Sync & Queued Message Handling

5.0 version
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Messenger: Sync & Queued Message Handling

Messenger provides a message bus with the ability to send messages and then handle them immediately in your application or send them through transports (e.g. queues) to be handled later. To learn more deeply about it, read the Messenger component docs.

Installation

In applications using Symfony Flex, run this command to install messenger:

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$ composer require messenger

Creating a Message & Handler

Messenger centers around two different classes that you'll create: (1) a message class that holds data and (2) a handler(s) class that will be called when that message is dispatched. The handler class will read the message class and perform some task.

There are no specific requirements for a message class, except that it can be serialized:

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// src/Message/SmsNotification.php
namespace App\Message;

class SmsNotification
{
    private $content;

    public function __construct(string $content)
    {
        $this->content = $content;
    }

    public function getContent(): string
    {
        return $this->content;
    }
}

A message handler is a PHP callable, the recommended way to create it is to create a class that implements MessageHandlerInterface and has an __invoke() method that's type-hinted with the message class (or a message interface):

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// src/MessageHandler/SmsNotificationHandler.php
namespace App\MessageHandler;

use App\Message\SmsNotification;
use Symfony\Component\Messenger\Handler\MessageHandlerInterface;

class SmsNotificationHandler implements MessageHandlerInterface
{
    public function __invoke(SmsNotification $message)
    {
        // ... do some work - like sending an SMS message!
    }
}

Thanks to autoconfiguration and the SmsNotification type-hint, Symfony knows that this handler should be called when an SmsNotification message is dispatched. Most of the time, this is all you need to do. But you can also manually configure message handlers. To see all the configured handlers, run:

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$ php bin/console debug:messenger

Dispatching the Message

You're ready! To dispatch the message (and call the handler), inject the message_bus service (via the MessageBusInterface), like in a controller:

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// src/Controller/DefaultController.php
namespace App\Controller;

use App\Message\SmsNotification;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\Messenger\MessageBusInterface;

class DefaultController extends AbstractController
{
    public function index(MessageBusInterface $bus)
    {
        // will cause the SmsNotificationHandler to be called
        $bus->dispatch(new SmsNotification('Look! I created a message!'));

        // or use the shortcut
        $this->dispatchMessage(new SmsNotification('Look! I created a message!'));

        // ...
    }
}

Transports: Async/Queued Messages

By default, messages are handled as soon as they are dispatched. If you want to handle a message asynchronously, you can configure a transport. A transport is capable of sending messages (e.g. to a queueing system) and then receiving them via a worker. Messenger supports multiple transports.

Note

If you want to use a transport that's not supported, check out the Enqueue's transport, which supports things like Kafka, Amazon SQS and Google Pub/Sub.

A transport is registered using a "DSN". Thanks to Messenger's Flex recipe, your .env file already has a few examples.

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# MESSENGER_TRANSPORT_DSN=amqp://guest:[email protected]:5672/%2f/messages
# MESSENGER_TRANSPORT_DSN=doctrine://default
# MESSENGER_TRANSPORT_DSN=redis://localhost:6379/messages

Uncomment whichever transport you want (or set it in .env.local). See Transport Configuration for more details.

Next, in config/packages/messenger.yaml, let's define a transport called async that uses this configuration:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                async: "%env(MESSENGER_TRANSPORT_DSN)%"
    
                # or expanded to configure more options
                #async:
                #    dsn: "%env(MESSENGER_TRANSPORT_DSN)%"
                #    options: []
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:transport name="async">%env(MESSENGER_TRANSPORT_DSN)%</framework:transport>
    
                <!-- or expanded to configure more options -->
                <framework:transport name="async"
                    dsn="%env(MESSENGER_TRANSPORT_DSN)%"
                >
                    <option key="...">...</option>
                </framework:transport>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'transports' => [
                'async' => '%env(MESSENGER_TRANSPORT_DSN)%',
    
                // or expanded to configure more options
                'async' => [
                   'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%',
                   'options' => []
                ],
            ],
        ],
    ]);
    

Routing Messages to a Transport

Now that you have a transport configured, instead of handling a message immediately, you can configure them to be sent to a transport:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                async: "%env(MESSENGER_TRANSPORT_DSN)%"
    
            routing:
                # async is whatever name you gave your transport above
                'App\Message\SmsNotification':  async
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:routing message-class="App\Message\SmsNotification">
                    <!-- async is whatever name you gave your transport above -->
                    <framework:sender service="async"/>
                </framework:routing>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'routing' => [
                // async is whatever name you gave your transport above
                'App\Message\SmsNotification' => 'async',
            ],
        ],
    ]);
    

Thanks to this, the App\Message\SmsNotification will be sent to the async transport and its handler(s) will not be called immediately. Any messages not matched under routing will still be handled immediately.

You can also route classes by their parent class or interface. Or send messages to multiple transport:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            routing:
                # route all messages that extend this example base class or interface
                'App\Message\AbstractAsyncMessage': async
                'App\Message\AsyncMessageInterface': async
    
                'My\Message\ToBeSentToTwoSenders': [async, audit]
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <!-- route all messages that extend this example base class or interface -->
                <framework:routing message-class="App\Message\AbstractAsyncMessage">
                    <framework:sender service="async"/>
                </framework:routing>
                <framework:routing message-class="App\Message\AsyncMessageInterface">
                    <framework:sender service="async"/>
                </framework:routing>
                <framework:routing message-class="My\Message\ToBeSentToTwoSenders">
                    <framework:sender service="async"/>
                    <framework:sender service="audit"/>
                </framework:routing>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'routing' => [
                // route all messages that extend this example base class or interface
                'App\Message\AbstractAsyncMessage' => 'async',
                'App\Message\AsyncMessageInterface' => 'async',
                'My\Message\ToBeSentToTwoSenders' => ['async', 'audit'],
            ],
        ],
    ]);
    

Doctrine Entities in Messages

If you need to pass a Doctrine entity in a message, it's better to pass the entity's primary key (or whatever relevant information the handler actually needs, like email, etc) instead of the object:

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class NewUserWelcomeEmail
{
    private $userId;

    public function __construct(int $userId)
    {
        $this->userId = $userId;
    }

    public function getUserId(): int
    {
        return $this->userId;
    }
}

Then, in your handler, you can query for a fresh object:

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// src/MessageHandler/NewUserWelcomeEmailHandler.php
namespace App\MessageHandler;

use App\Message\NewUserWelcomeEmail;
use App\Repository\UserRepository;
use Symfony\Component\Messenger\Handler\MessageHandlerInterface;

class NewUserWelcomeEmailHandler implements MessageHandlerInterface
{
    private $userRepository;

    public function __construct(UserRepository $userRepository)
    {
        $this->userRepository = $userRepository;
    }

    public function __invoke(NewUserWelcomeEmail $welcomeEmail)
    {
        $user = $this->userRepository->find($welcomeEmail->getUserId());

        // ... send an email!
    }
}

This guarantees the entity contains fresh data.

Handling Messages Synchronously

If a message doesn't match any routing rules, it won't be sent to any transport and will be handled immediately. In some cases (like when binding handlers to different transports), it's easier or more flexible to handle this explicitly: by creating a sync transport and "sending" messages there to be handled immediately:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                # ... other transports
    
                sync: 'sync://'
    
            routing:
                App\Message\SmsNotification: sync
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <!-- ... other transports -->
    
                <framework:transport name="sync" dsn="sync://"/>
    
                <framework:routing message-class="App\Message\SmsNotification">
                    <framework:sender service="sync"/>
                </framework:routing>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'transports' => [
                // ... other transports
    
                'sync' => 'sync://',
            ],
            'routing' => [
                'App\Message\SmsNotification' => 'sync',
            ],
        ],
    ]);
    

Creating your Own Transport

You can also create your own transport if you need to send or receive messages from something that is not supported. See How to Create Your own Messenger Transport.

Consuming Messages (Running the Worker)

Once your messages have been routed, in most cases, you'll need to "consume" them. You can do this with the messenger:consume command:

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$ php bin/console messenger:consume async

# use -vv to see details about what's happening
$ php bin/console messenger:consume async -vv

The first argument is the receiver's name (or service id if you routed to a custom service). By default, the command will run forever: looking for new messages on your transport and handling them. This command is called your "worker".

Deploying to Production

On production, there are a few important things to think about:

Use Supervisor to keep your worker(s) running
You'll want one or more "workers" running at all times. To do that, use a process control system like Supervisor.
Don't Let Workers Run Forever
Some services (like Doctrine's EntityManager) will consume more memory over time. So, instead of allowing your worker to run forever, use a flag like messenger:consume --limit=10 to tell your worker to only handle 10 messages before exiting (then Supervisor will create a new process). There are also other options like --memory-limit=128M and --time-limit=3600.
Restart Workers on Deploy
Each time you deploy, you'll need to restart all your worker processes so that they see the newly deployed code. To do this, run messenger:stop-workers on deploy. This will signal to each worker that it should finish the message it's currently handling and shut down gracefully. Then, Supervisor will create new worker processes. The command uses the app cache internally - so make sure this is configured to use an adapter you like.

Prioritized Transports

Sometimes certain types of messages should have a higher priority and be handled before others. To make this possible, you can create multiple transports and route different messages to them. For example:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                async_priority_high:
                    dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
                    options:
                        # queue_name is specific to the doctrine transport
                        queue_name: high
    
                        # for amqp send to a separate exchange then queue
                        #exchange:
                        #    name: high
                        #queues:
                        #    messages_high: ~
                        # or redis try "group"
                async_priority_low:
                    dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
                    options:
                        queue_name: low
    
            routing:
                'App\Message\SmsNotification':  async_priority_low
                'App\Message\NewUserWelcomeEmail':  async_priority_high
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:transport name="async_priority_high" dsn="%env(MESSENGER_TRANSPORT_DSN)%">
                    <option key="queue_name">high</option>
                </framework:transport>
                <framework:transport name="async_priority_low" dsn="%env(MESSENGER_TRANSPORT_DSN)%">
                    <option key="queue_name">low</option>
                </framework:transport>
    
                <framework:routing message-class="App\Message\SmsNotification">
                    <framework:sender service="async_priority_low"/>
                </framework:routing>
                <framework:routing message-class="App\Message\NewUserWelcomeEmail">
                    <framework:sender service="async_priority_high"/>
                </framework:routing>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'transports' => [
                'async_priority_high' => [
                    'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%',
                    'options' => [
                        'queue_name' => 'high',
                    ],
                ],
                'async_priority_low' => [
                    'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%',
                    'options' => [
                        'queue_name' => 'low',
                    ],
                ],
            ],
            'routing' => [
                'App\Message\SmsNotification' => 'async_priority_low',
                'App\Message\NewUserWelcomeEmail' => 'async_priority_high',
            ],
        ],
    ]);
    

You can then run individual workers for each transport or instruct one worker to handle messages in a priority order:

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$ php bin/console messenger:consume async_priority_high async_priority_low

The worker will always first look for messages waiting on async_priority_high. If there are none, then it will consume messages from async_priority_low.

Supervisor Configuration

Supervisor is a great tool to guarantee that your worker process(es) is always running (even if it closes due to failure, hitting a message limit or thanks to messenger:stop-workers). You can install it on Ubuntu, for example, via:

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$ sudo apt-get install supervisor

Supervisor configuration files typically live in a /etc/supervisor/conf.d directory. For example, you can create a new messenger-worker.conf file there to make sure that 2 instances of messenger:consume are running at all times:

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;/etc/supervisor/conf.d/messenger-worker.conf
[program:messenger-consume]
command=php /path/to/your/app/bin/console messenger:consume async --time-limit=3600
user=ubuntu
numprocs=2
autostart=true
autorestart=true
process_name=%(program_name)s_%(process_num)02d

Change the async argument to use the name of your transport (or transports) and user to the Unix user on your server. Next, tell Supervisor to read your config and start your workers:

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$ sudo supervisorctl reread

$ sudo supervisorctl update

$ sudo supervisorctl start messenger-consume:*

See the Supervisor docs for more details.

Retries & Failures

If an exception is thrown while consuming a message from a transport it will automatically be re-sent to the transport to be tried again. By default, a message will be retried 3 times before being discarded or sent to the failure transport. Each retry will also be delayed, in case the failure was due to a temporary issue. All of this is configurable for each transport:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                async_priority_high:
                    dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
    
                    # default configuration
                    retry_strategy:
                        max_retries: 3
                        # milliseconds delay
                        delay: 1000
                        # causes the delay to be higher before each retry
                        # e.g. 1 second delay, 2 seconds, 4 seconds
                        multiplier: 2
                        max_delay: 0
                        # override all of this with a service that
                        # implements Symfony\Component\Messenger\Retry\RetryStrategyInterface
                        # service: null
    

Avoiding Retrying

Sometimes handling a message might fail in a way that you know is permanent and should not be retried. If you throw UnrecoverableMessageHandlingException, the message will not be retried.

Saving & Retrying Failed Messages

If a message fails it is retried multiple times (max_retries) and then will be discarded. To avoid this happening, you can instead configure a failure_transport:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            # after retrying, messages will be sent to the "failed" transport
            failure_transport: failed
    
            transports:
                # ... other transports
    
                failed: 'doctrine://default?queue_name=failed'
    

In this example, if handling a message fails 3 times (default max_retries), it will then be sent to the failed transport. While you can use messenger:consume failed to consume this like a normal transport, you'll usually want to manually view the messages in the failure transport and choose to retry them:

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# see all messages in the failure transport
$ php bin/console messenger:failed:show

# see details about a specific failure
$ php bin/console messenger:failed:show 20 -vv

# view and retry messages one-by-one
$ php bin/console messenger:failed:retry -vv

# retry specific messages
$ php bin/console messenger:failed:retry 20 30 --force

# remove a message without retrying it
$ php bin/console messenger:failed:remove 20

If the message fails again, it will be re-sent back to the failure transport due to the normal retry rules. Once the max retry has been hit, the message will be discarded permanently.

Transport Configuration

Messenger supports a number of different transport types, each with their own options.

AMQP Transport

The amqp transport configuration looks like this:

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# .env
MESSENGER_TRANSPORT_DSN=amqp://guest:[email protected]:5672/%2f/messages

To use Symfony's built-in AMQP transport, you need the AMQP PHP extension.

Note

By default, the transport will automatically create any exchanges, queues and binding keys that are needed. That can be disabled, but some functionality may not work correctly (like delayed queues).

The transport has a number of other options, including ways to configure the exchange, queues binding keys and more. See the documentation on Connection.

You can also configure AMQP-specific settings on your message by adding AmqpStamp to your Envelope:

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use Symfony\Component\Messenger\Transport\AmqpExt\AmqpStamp;
// ...

$attributes = [];
$bus->dispatch(new SmsNotification(), [
    new AmqpStamp('custom-routing-key', AMQP_NOPARAM, $attributes)
]);

Caution

The consumers do not show up in an admin panel as this transport does not rely on \AmqpQueue::consume() which is blocking. Having a blocking receiver makes the --time-limit/--memory-limit options of the messenger:consume command as well as the messenger:stop-workers command inefficient, as they all rely on the fact that the receiver returns immediately no matter if it finds a message or not. The consume worker is responsible for iterating until it receives a message to handle and/or until one of the stop conditions is reached. Thus, the worker's stop logic cannot be reached if it is stuck in a blocking call.

Doctrine Transport

The Doctrine transport can be used to store messages in a database table.

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# .env
MESSENGER_TRANSPORT_DSN=doctrine://default

The format is doctrine://<connection_name>, in case you have multiple connections and want to use one other than the "default". The transport will automatically create a table named messenger_messages (this is configurable) when the transport is first used. You can disable that with the auto_setup option and set the table up manually by calling the messenger:setup-transports command.

Tip

To avoid tools like Doctrine Migrations from trying to remove this table because it's not part of your normal schema, you can set the schema_filter option:

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# config/packages/doctrine.yaml
doctrine:
    dbal:
        schema_filter: '~^(?!messenger_messages)~'

The transport has a number of options:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                async_priority_high: "%env(MESSENGER_TRANSPORT_DSN)%?queue_name=high_priority"
                async_normal:
                    dsn: "%env(MESSENGER_TRANSPORT_DSN)%"
                    options:
                        queue_name: normal_priority
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:transport name="async_priority_high" dsn="%env(MESSENGER_TRANSPORT_DSN)%?queue_name=high_priority"/>
                <framework:transport name="async_priority_low" dsn="%env(MESSENGER_TRANSPORT_DSN)%">
                    <framework:option queue_name="normal_priority"/>
                </framework:transport>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'transports' => [
                'async_priority_high' => 'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%?queue_name=high_priority',
                'async_priority_low' => [
                    'dsn' => '%env(MESSENGER_TRANSPORT_DSN)%',
                    'options' => [
                        'queue_name' => 'normal_priority'
                    ]
                ],
            ],
        ],
    ]);
    

Options defined under options take precedence over ones defined in the DSN.

Option Description Default
table_name Name of the table messenger_messages
queue_name Name of the queue (a column in the table, to use one table for multiple transports) default
redeliver_timeout Timeout before retrying a message that's in the queue but in the "handling" state (if a worker died for some reason, this will occur, eventually you should retry the message) - in seconds. 3600
auto_setup Whether the table should be created automatically during send / get. true

Redis Transport

The Redis transport uses streams to queue messages.

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# .env
MESSENGER_TRANSPORT_DSN=redis://localhost:6379/messages
# Full DSN Example
MESSENGER_TRANSPORT_DSN=redis://[email protected]:6379/messages/symfony/consumer?auto_setup=true&serializer=1&stream_max_entries=0&dbindex=0

To use the Redis transport, you will need the Redis PHP extension (>=4.3) and a running Redis server (^5.0).

A number of options can be configured via the DSN or via the options key under the transport in messenger.yaml:

Option Description Default
stream The Redis stream name messages
group The Redis consumer group name symfony
consumer Consumer name used in Redis consumer
auto_setup Create the Redis group automatically? true
auth The Redis password  
serializer How to serialize the final payload in Redis (the Redis::OPT_SERIALIZER option) Redis::SERIALIZER_PHP
stream_max_entries The maximum number of entries which the stream will be trimmed to. Set it to a large enough number to avoid losing pending messages 0 (which means "no trimming")

In Memory Transport

The in-memory transport does not actually delivery messages. Instead, it holds them in memory during the request, which can be useful for testing. For example, if you have an async_priority_normal transport, you could override it in the test environment to use this transport:

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# config/packages/test/messenger.yaml
framework:
    messenger:
        transports:
            async_priority_normal: 'in-memory:///'

Then, while testing, messages will not be delivered to the real transport. Even better, in a test, you can check that exactly one message was sent during a request:

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// tests/DefaultControllerTest.php
namespace App\Tests;

use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
use Symfony\Component\Messenger\Transport\InMemoryTransport;

class DefaultControllerTest extends WebTestCase
{
    public function testSomething()
    {
        $client = static::createClient();
        // ...

        $this->assertSame(200, $client->getResponse()->getStatusCode());

        /* @var InMemoryTransport $transport */
        $transport = self::$container->get('messenger.transport.async_priority_normal');
        $this->assertCount(1, $transport->getSent());
    }
}

Note

All in-memory transports will be reset automatically after each test in test classes extending KernelTestCase or WebTestCase.

Serializing Messages

When messages are sent to (and received from) a transport, they're serialized using PHP's native serialize() & unserialize() functions. You can change this globally (or for each transport) to a service that implements SerializerInterface:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            serializer:
                default_serializer: messenger.transport.symfony_serializer
                symfony_serializer:
                    format: json
                    context: { }
    
            transports:
                async_priority_normal:
                    dsn: # ...
                    serializer: messenger.transport.symfony_serializer
    

The messenger.transport.symfony_serializer is a built-in service that uses the Serializer component and can be configured in a few ways. If you do choose to use the Symfony serializer, you can control the context on a case-by-case basis via the SerializerStamp (see Envelopes & Stamps).

Customizing Handlers

Manually Configuring Handlers

Symfony will normally find and register your handler automatically. But, you can also configure a handler manually - and pass it some extra config - by tagging the handler service with messenger.message_handler

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    # config/services.yaml
    services:
        App\MessageHandler\SmsNotificationHandler:
            tags: [messenger.message_handler]
    
            # or configure with options
            tags:
                -
                    name: messenger.message_handler
                    # only needed if can't be guessed by type-hint
                    handles: App\Message\SmsNotification
    
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    <!-- config/services.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd">
    
        <services>
            <service id="App\MessageHandler\SmsNotificationHandler">
                 <!-- handles is only needed if it can't be guessed by type-hint -->
                 <tag name="messenger.message_handler"
                      handles="App\Message\SmsNotification"/>
            </service>
        </services>
    </container>
    
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    // config/services.php
    use App\Message\SmsNotification;
    use App\MessageHandler\SmsNotificationHandler;
    
    $container->register(SmsNotificationHandler::class)
        ->addTag('messenger.message_handler', [
            // only needed if can't be guessed by type-hint
            'handles' => SmsNotification::class,
        ]);
    

Possible options to configure with tags are:

  • bus
  • from_transport
  • handles
  • method
  • priority

Handler Subscriber & Options

A handler class can handle multiple messages or configure itself by implementing MessageSubscriberInterface:

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// src/MessageHandler/SmsNotificationHandler.php
namespace App\MessageHandler;

use App\Message\OtherSmsNotification;
use App\Message\SmsNotification;
use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;

class SmsNotificationHandler implements MessageSubscriberInterface
{
    public function __invoke(SmsNotification $message)
    {
        // ...
    }

    public function handleOtherSmsNotification(OtherSmsNotification $message)
    {
        // ...
    }

    public static function getHandledMessages(): iterable
    {
        // handle this message on __invoke
        yield SmsNotification::class;

        // also handle this message on handleOtherSmsNotification
        yield OtherSmsNotification::class => [
            'method' => 'handleOtherSmsNotification',
            //'priority' => 0,
            //'bus' => 'messenger.bus.default',
        ];
    }
}

Binding Handlers to Different Transports

Each message can have multiple handlers, and when a message is consumed all of its handlers are called. But you can also configure a handler to only be called when it's received from a specific transport. This allows you to have a single message where each handler is called by a different "worker" that's consuming a different transport.

Suppose you have an UploadedImage message with two handlers:

  • ThumbnailUploadedImageHandler: you want this to be handled by a transport called image_transport
  • NotifyAboutNewUploadedImageHandler: you want this to be handled by a transport called async_priority_normal

To do this, add the from_transport option to each handler. For example:

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// src/MessageHandler/ThumbnailUploadedImageHandler.php
namespace App\MessageHandler;

use App\Message\UploadedImage;
use Symfony\Component\Messenger\Handler\MessageSubscriberInterface;

class ThumbnailUploadedImageHandler implements MessageSubscriberInterface
{
    public function __invoke(UploadedImage $uploadedImage)
    {
        // do some thumbnailing
    }

    public static function getHandledMessages(): iterable
    {
        yield UploadedImage::class => [
            'from_transport' => 'image_transport',
        ];
    }
}

And similarly:

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// src/MessageHandler/NotifyAboutNewUploadedImageHandler.php
// ...

class NotifyAboutNewUploadedImageHandler implements MessageSubscriberInterface
{
    // ...

    public static function getHandledMessages(): iterable
    {
        yield UploadedImage::class => [
            'from_transport' => 'async_priority_normal',
        ];
    }
}

Then, make sure to "route" your message to both transports:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            transports:
                async_priority_normal: # ...
                image_transport: # ...
    
            routing:
                # ...
                'App\Message\UploadedImage': [image_transport, async_priority_normal]
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:transport name="async_priority_normal" dsn="..."/>
                <framework:transport name="image_transport" dsn="..."/>
    
                <framework:routing message-class="App\Message\UploadedImage">
                    <framework:sender service="image_transport"/>
                    <framework:sender service="async_priority_normal"/>
                </framework:routing>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'transports' => [
                'async_priority_normal' => '...',
                'image_transport' => '...',
            ],
            'routing' => [
                'App\Message\UploadedImage' => ['image_transport', 'async_priority_normal']
            ]
        ],
    ]);
    

That's it! You can now consume each transport:

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# will only call ThumbnailUploadedImageHandler when handling the message
$ php bin/console messenger:consume image_transport -vv

$ php bin/console messenger:consume async_priority_normal -vv

Caution

If a handler does not have from_transport config, it will be executed on every transport that the message is received from.

Extending Messenger

Envelopes & Stamps

A message can be any PHP object. Sometimes, you may need to configure something extra about the message - like the way it should be handled inside Amqp or adding a delay before the message should be handled. You can do that by adding a "stamp" to your message:

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use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\MessageBusInterface;
use Symfony\Component\Messenger\Stamp\DelayStamp;

public function index(MessageBusInterface $bus)
{
    $bus->dispatch(new SmsNotification('...'), [
        // wait 5 seconds before processing
        new DelayStamp(5000)
    ]);

    // or explicitly create an Envelope
    $bus->dispatch(new Envelope(new SmsNotification('...'), [
        new DelayStamp(5000)
    ]));

    // ...
}

Internally, each message is wrapped in an Envelope, which holds the message and stamps. You can create this manually or allow the message bus to do it. There are a variety of different stamps for different purposes and they're used internally to track information about a message - like the message bus that's handling it or if it's being retried after failure.

Middleware

What happens when you dispatch a message to a message bus depends on its collection of middleware and their order. By default, the middleware configured for each bus looks like this:

  1. add_bus_name_stamp_middleware - adds a stamp to record which bus this message was dispatched into;
  2. dispatch_after_current_bus- see Transactional Messages: Handle New Messages After Handling is Done;
  3. failed_message_processing_middleware - processes messages that are being retried via the failure transport to make them properly function as if they were being received from their original transport;
  4. Your own collection of middleware;
  5. send_message - if routing is configured for the transport, this sends messages to that transport and stops the middleware chain;
  6. handle_message - calls the message handler(s) for the given message.

Note

These middleware names are actually shortcuts names. The real service ids are prefixed with messenger.middleware..

You can add your own middleware to this list, or completely disable the default middleware and only include your own:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            buses:
                messenger.bus.default:
                    middleware:
                        # service ids that implement Symfony\Component\Messenger\Middleware
                        - 'App\Middleware\MyMiddleware'
                        - 'App\Middleware\AnotherMiddleware'
    
                    #default_middleware: false
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:middleware id="App\Middleware\MyMiddleware"/>
                <framework:middleware id="App\Middleware\AnotherMiddleware"/>
                <framework:bus name="messenger.bus.default" default-middleware="false"/>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'buses' => [
                'messenger.bus.default' => [
                    'middleware' => [
                        'App\Middleware\MyMiddleware',
                        'App\Middleware\AnotherMiddleware',
                    ],
                    'default_middleware' => false,
                ],
            ],
        ],
    ]);
    

Note

If a middleware service is abstract, a different instance of the service will be created per bus.

Middleware for Doctrine

New in version 1.11: The following Doctrine middleware were introduced in DoctrineBundle 1.11.

If you use Doctrine in your app, a number of optional middleware exist that you may want to use:

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    # config/packages/messenger.yaml
    framework:
        messenger:
            buses:
                command_bus:
                    middleware:
                        # each time a message is handled, the Doctrine connection
                        # is "pinged" and reconnected if it's closed. Useful
                        # if your workers run for a long time and the database
                        # connection is sometimes lost
                        - doctrine_ping_connection
    
                        # After handling, the Doctrine connection is closed,
                        # which can free up database connections in a worker,
                        # instead of keeping them open forever
                        - doctrine_close_connection
    
                        # wraps all handlers in a single Doctrine transaction
                        # handlers do not need to call flush() and an error
                        # in any handler will cause a rollback
                        - doctrine_transaction
    
                        # or pass a different entity manager to any
                        #- doctrine_transaction: ['custom']
    
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    <!-- config/packages/messenger.xml -->
    <?xml version="1.0" encoding="UTF-8" ?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            https://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            https://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <framework:messenger>
                <framework:bus name="command_bus">
                    <framework:middleware id="doctrine_transaction"/>
                    <framework:middleware id="doctrine_ping_connection"/>
                    <framework:middleware id="doctrine_close_connection"/>
    
                    <!-- or pass a different entity manager to any -->
                    <!--
                    <framework:middleware id="doctrine_transaction">
                        <framework:argument>custom</framework:argument>
                    </framework:middleware>
                    -->
                </framework:bus>
            </framework:messenger>
        </framework:config>
    </container>
    
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    // config/packages/messenger.php
    $container->loadFromExtension('framework', [
        'messenger' => [
            'buses' => [
                'command_bus' => [
                    'middleware' => [
                        'doctrine_transaction',
                        'doctrine_ping_connection',
                        'doctrine_close_connection',
                        // Using another entity manager
                        ['id' => 'doctrine_transaction', 'arguments' => ['custom']],
                    ],
                ],
            ],
        ],
    ]);
    

Messenger Events

In addition to middleware, Messenger also dispatches several events. You can create an event listener to hook into various parts of the process. For each, the event class is the event name:

Multiple Buses, Command & Event Buses

Messenger gives you a single message bus service by default. But, you can configure as many as you want, creating "command", "query" or "event" buses and controlling their middleware. See Multiple Buses.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.