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[Messenger] Dispatch events before & after each handler #52425

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[Messenger] Dispatch events before & after each handler #52425

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2 changes: 2 additions & 0 deletions src/Symfony/Bundle/FrameworkBundle/Resources/config/messenger.php
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,8 @@
->abstract()
->args([
abstract_arg('bus handler resolver'),
false,
service('event_dispatcher'),
])
->tag('monolog.logger', ['channel' => 'messenger'])
->call('setLogger', [service('logger')->ignoreOnInvalid()])
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5 changes: 5 additions & 0 deletions src/Symfony/Component/Messenger/CHANGELOG.md
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@@ -1,6 +1,11 @@
CHANGELOG
=========

7.1
---

* New events: `HandlerStartingEvent`, `HandlerSuccessEvent`, `HandlerFailureEvent`

7.0
---

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24 changes: 24 additions & 0 deletions src/Symfony/Component/Messenger/Event/AbstractHandlerEvent.php
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@@ -0,0 +1,24 @@
<?php

/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <[email protected]>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/

namespace Symfony\Component\Messenger\Event;

use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\Handler\HandlerDescriptor;

abstract class AbstractHandlerEvent
{
public function __construct(
public readonly Envelope $envelope,
public readonly HandlerDescriptor $handlerDescriptor,
Comment on lines +20 to +21
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Do you mean no abstract? What about AbstractWorkerMessageEvent?

) {
}
}
29 changes: 29 additions & 0 deletions src/Symfony/Component/Messenger/Event/HandlerFailureEvent.php
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@@ -0,0 +1,29 @@
<?php

/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <[email protected]>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/

namespace Symfony\Component\Messenger\Event;

use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\Handler\HandlerDescriptor;

/**
* Event dispatched after a handler fails.
*/
final class HandlerFailureEvent extends AbstractHandlerEvent
{
public function __construct(
Envelope $envelope,
HandlerDescriptor $handlerDescriptor,
public readonly \Throwable $exception,
) {
parent::__construct($envelope, $handlerDescriptor);
}
}
19 changes: 19 additions & 0 deletions src/Symfony/Component/Messenger/Event/HandlerStartingEvent.php
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@@ -0,0 +1,19 @@
<?php

/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <[email protected]>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/

namespace Symfony\Component\Messenger\Event;

/**
* Event dispatched before a handler is called.
*/
final class HandlerStartingEvent extends AbstractHandlerEvent
Comment on lines +15 to +17
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The name of the class does not make it clear, that it is dispatched before.

Maybe BeforeHandlerStartEvent?

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I actually thought about this, but wanted to keep things organized by prefix, like Worker* events. I don't mind though, what about just BeforeHandlerEvent?

{
}
19 changes: 19 additions & 0 deletions src/Symfony/Component/Messenger/Event/HandlerSuccessEvent.php
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@@ -0,0 +1,19 @@
<?php

/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <[email protected]>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/

namespace Symfony\Component\Messenger\Event;

/**
* Event dispatched after a handler succeeds.
*/
final class HandlerSuccessEvent extends AbstractHandlerEvent
{
}
17 changes: 17 additions & 0 deletions src/Symfony/Component/Messenger/Middleware/HandleMessageMiddleware.php
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Expand Up @@ -11,8 +11,12 @@

namespace Symfony\Component\Messenger\Middleware;

use Psr\EventDispatcher\EventDispatcherInterface;
use Psr\Log\LoggerAwareTrait;
use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\Event\HandlerFailureEvent;
use Symfony\Component\Messenger\Event\HandlerStartingEvent;
use Symfony\Component\Messenger\Event\HandlerSuccessEvent;
use Symfony\Component\Messenger\Exception\HandlerFailedException;
use Symfony\Component\Messenger\Exception\LogicException;
use Symfony\Component\Messenger\Exception\NoHandlerForMessageException;
Expand All @@ -35,6 +39,7 @@ class HandleMessageMiddleware implements MiddlewareInterface
public function __construct(
private HandlersLocatorInterface $handlersLocator,
private bool $allowNoHandlers = false,
private ?EventDispatcherInterface $eventDispatcher = null,
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Suggested change
private ?EventDispatcherInterface $eventDispatcher = null,
private ?EventDispatcherInterface $dispatcher = null,

I like it more, but lets see what the others say

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Actually SendMessageMiddleware uses $eventDispatcher, so I guess it's better to keep it consistent here?

) {
}

Expand All @@ -58,6 +63,10 @@ public function handle(Envelope $envelope, StackInterface $stack): Envelope
continue;
}

$this->eventDispatcher?->dispatch(new HandlerStartingEvent($envelope, $handlerDescriptor));

$e = null;

try {
$handler = $handlerDescriptor->getHandler();
$batchHandler = $handlerDescriptor->getBatchHandler();
Expand Down Expand Up @@ -97,6 +106,14 @@ public function handle(Envelope $envelope, StackInterface $stack): Envelope
} catch (\Throwable $e) {
$exceptions[$handlerDescriptor->getName()] = $e;
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Suggested change
$exceptions[$handlerDescriptor->getName()] = $e;
$exceptions[$handlerDescriptor->getName()] = $e;
$this->eventDispatcher?->dispatch(new HandlerFailureEvent($envelope, $handlerDescriptor->getName(), $e));

Same for the success case and remove the $e variable?

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I don't mind dispatching the failure event in the catch block, however I'm a bit reluctant about dispatching the success event in the try block, as a failure in any listener/subscriber of this event would mark the handler as failed.

That's why I kept things outside the try/catch.

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@ruudk ruudk Nov 3, 2023 •
edited by OskarStark
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It would be great if a HandlerFailureEvent subscriber could silence an exception.

Right now, it's only possible to log them. But by always passing the exception to the HandlerFailureEvent and dispatching that, a subscriber could say "ignore this".

A use case could be to annotate #[IgnoreException(SomeTimeoutException::class)] on the handler. In case of an exception, a HandlerFailureEvent subscriber would see that the handler wants to ignore this exception, and it will silence it.

From Messenger perspective all will be fine again.

Related to

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@BenMorel BenMorel Nov 3, 2023 •
edited
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We could add a HandlerFailureEvent::ignoreException(bool $ignore) method indeed. I don't mind adding this feature, and again I'll leave it to others to decide if adding it is a good idea.

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@ro0NL @OskarStark What do you think?

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Also fine, but then we should let a subscriber mutate the handler descriptor. See my previous comment.

}

if (null !== $this->eventDispatcher) {
$event = (null !== $e)
? new HandlerFailureEvent($envelope, $handlerDescriptor, $e)
: new HandlerSuccessEvent($envelope, $handlerDescriptor);

$this->eventDispatcher->dispatch($event);
}
}

/** @var FlushBatchHandlersStamp $flushStamp */
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43 changes: 43 additions & 0 deletions src/Symfony/Component/Messenger/Tests/Middleware/HandleMessageMiddlewareTest.php
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Expand Up @@ -11,7 +11,11 @@

namespace Symfony\Component\Messenger\Tests\Middleware;

use Psr\EventDispatcher\EventDispatcherInterface;
use Symfony\Component\Messenger\Envelope;
use Symfony\Component\Messenger\Event\HandlerFailureEvent;
use Symfony\Component\Messenger\Event\HandlerStartingEvent;
use Symfony\Component\Messenger\Event\HandlerSuccessEvent;
use Symfony\Component\Messenger\Exception\HandlerFailedException;
use Symfony\Component\Messenger\Exception\LogicException;
use Symfony\Component\Messenger\Exception\NoHandlerForMessageException;
Expand Down Expand Up @@ -356,6 +360,45 @@ public function testHandlerArgumentsStampNamedArgument()

$middleware->handle($envelope, $this->getStackMock());
}

public function testDispatchHandlerEvents()
{
$message = new DummyMessage('Hey');
$envelope = new Envelope($message);

$successHandler = $this->createMock(HandleMessageMiddlewareTestCallable::class);
$successHandler->expects($this->once())->method('__invoke');

$failureHandler = $this->createMock(HandleMessageMiddlewareTestCallable::class);
$failureHandler->expects($this->once())->method('__invoke')->willThrowException(
$exception = new \RuntimeException('Handler failed'),
);

$handlersLocator = new HandlersLocator([
DummyMessage::class => [
$successHandlerDescriptor = new HandlerDescriptor($successHandler, ['alias' => 'successHandler']),
$failureHandlerDescriptor = new HandlerDescriptor($failureHandler, ['alias' => 'failureHandler']),
],
]);

$dispatcher = $this->createMock(EventDispatcherInterface::class);

$handledStamp = new HandledStamp(null, $successHandlerDescriptor->getName());

$dispatcher->expects($this->exactly(4))
->method('dispatch')
->withConsecutive(
[new HandlerStartingEvent($envelope, $successHandlerDescriptor)],
[new HandlerSuccessEvent($envelope->with($handledStamp), $successHandlerDescriptor)],
[new HandlerStartingEvent($envelope->with($handledStamp), $failureHandlerDescriptor)],
[new HandlerFailureEvent($envelope->with($handledStamp), $failureHandlerDescriptor, $exception)],
);

$middleware = new HandleMessageMiddleware($handlersLocator, eventDispatcher: $dispatcher);

$this->expectException(HandlerFailedException::class);
$middleware->handle($envelope, new StackMiddleware());
}
}

class HandleMessageMiddlewareTestCallable
Expand Down