Using the Symfony Messenger

Slides for my workshop at Dutch PHP Conference 2019.

Transcript

1. Dutch PHP Conference 2019
   USING THE SYMFONY MESSENGER
   

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2. AGENDA
   1. Quick introduction round
   2. Setting up the project skeleton,
   while I guide you through the example code
   3. Presentation: Introduction to messenger-concepts
   4. Task 1: Introduce synchronous message processing
   5. Presentation: Transports for async processing
   6. Task 2: Pick your challenge(s)
   7. Questions
   

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3. GOALS
   Have fun
   Learn about the Messenger component
   Just 3 hours won't make you an expert, but hopefully you:
   • have a feeling whether this component is useful to you
   • maybe you get interested in message-based architecture
   Feel free to ask questions at any time.
   If you have suggestions how I can better suit your learning style,
   please let me know and I will adjust
   

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4. WHO AM I
   Denis Brumann
   Software Developer at SensioLabs Germany in Berlin
   Twitter: @dbrumann Email: denis.brumann@sensiolabs.de
   Personal Focus:
   • Migrating client's legacy projects
   Symfony experience:
   • started with 2.0
   • currently using 3.4 in client project
   • for private projects I try to use latest version possible
   

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5. SETTING UP THE PROJECT
   git remote add dpc2019 \
   https://github.com/dbrumann/dpc2019-workshop.git
   git fetch dpc2019
   git checkout -b develop dpc2019/master \
   --no-track
   

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6. CORE CONCEPTS
   Message
   Data Object containing all relevant data
   Message Bus
   Takes a message and delegates it to the right recipient
   Message Handler
   Takes a Message-object and handles it, i.e. processes it
   

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7. ADVANCED CONCEPTS
   Envelope
   Wrapper for a Message and contextual info (stamps)
   Stamp
   Provides context to/from a Middleware
   Middleware
   Controls the behavior of the Message Bus
   

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8. MESSAGE BUS
   interface MessageBusInterface
   {
   /**
   * Dispatches the given message.
   *
   * @param object|Envelope $message The message or the message
   * pre-wrapped in an envelope
   * @param StampInterface[] $stamps
   */
   public function dispatch($message, array $stamps = []): Envelope;
   }
   

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9. SENDING A MESSAGE
   class MyService
   {
   private $messageBus;
   public function __construct(MessageBusInterface $messageBus)
   {
   $this->messageBus = $messageBus;
   }
   public function doSomething(string $url)
   {
   $this->messageBus->dispatch(new TakeScreenshotMessage($url));
   }
   }
   

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10. SENDING A MESSAGE
    public function index(Request $request): Response
    {
    if ($request->isMethod('POST')) {
    $url = trim($request->request->get('url'));
    $this->dispatchMessage(new TakeScreenshotMessage($url));
    }
    return $this->render('screenshot.html.twig');
    }
    

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11. TASK 1
    • Install the Messenger component
    • Modify
    App\Registration\Registration::register()
    or the corresponding Controller-action
    App\Controller\RegistrationController::register()
    to use the Messenger instead
    • Create a Message-object (you can take the Form-object as a reference point)
    • Dispatch the Message using the MessageBus
    

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13. TASK 1
    • Install the Messenger component
    • Modify
    App\Registration\Registration::register()
    or the corresponding Controller-action
    App\Controller\RegistrationController::register()
    to use the Messenger instead
    • Create a Message-object (you can take the Form-object as a reference point)
    • Dispatch the Message using the MessageBus
    • Create a MessageHandler
    

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14. HANDLING MESSAGES
    class TakeScreenshotHandler implements MessageHandlerInterface
    {
    public function __invoke(TakeScreenshotMessage $message)
    {
    ...
    }
    }
    

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15. HANDLING MESSAGES
    class ScreenshotMessageSubscriber implements MessageSubscriberInterface
    {
    public static function getHandledMessages(): iterable
    {
    yield TakeScreenshotMessage::class => [
    'method' => 'takeScreenshot'
    ];
    }
    public function takeScreenshot(TakeScreenshotMessage $message)
    {
    ...
    }
    }
    

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17. https://github.com/dbrumann/dpc2019-workshop/tree/task1/sync_register
    git checkout dpc2019/task1/sync_register
    https://github.com/dbrumann/dpc2019-workshop/tree/task1/split_handler
    git checkout dpc2019/task1/split_handler
    

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18. Message
    Broker
    publish
    subscribe
    

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22. AVAILABLE TRANSPORTS
    AMQP (RabbitMQ)
    Redis
    Doctrine (using a DBAL-Connection)
    InMemory (for tests)
    Need more? Enqueue provides many more adapters
    

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23. IMPORTANT COMMANDS
    bin/console messenger:setup-transports
    bin/console messenger:consume
    

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24. PICK YOUR CHALLENGE(S)
    • Validating messages inside the MessageBus
    • Sending registration mails with Symfony Mailer
    (using async transport)
    • Creating an implicit workflow using many sync/async-handled
    messages
    • Adding capability to deal with failing messages
    • Looking into CQRS
    • Creating a CommandBus, (QueryBus), EventBus
    

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26. framework:
    messenger:
    transports:
    sync: 'sync://'
    async: '%env(MESSENGER_TRANSPORT_DSN)%'
    routing:
    # Route your messages to the transports
    App\Message\RequestRegistrationQuery: 'sync'
    App\Message\RegisterUserCommand: 'async'
    App\Message\UserRegisteredEvent: 'async'
    

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27. # default configuration
    retry_strategy:
    max_retries: 3
    delay: 1000 # delay for first retry
    multiplier: 2 # multiply delay with each try
    max_delay: 0
    # service: null
    # id for custom RetryStrategy
    

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28. framework:
    messenger:
    failure_transport: 'failed'
    transports:
    ...
    failed: 'doctrine://default?queue_name=failed'
    routing:
    ...
    

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29. bin/console messenger:failed:show
    bin/console messenger:failed:retry
    bin/console messenger:failed:remove
    

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30. $envelope = $this->dispatchMessage($form->getData());
    $token = $envelope->last(HandledStamp::class)->getResult();
    ENVELOPES & STAMPS
    

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31. Questions?
    

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32. Thank You!
    

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