Messenger! Queue work for Later

Overview

Symfony's Messenger component gives you a beautiful system for designing your code around "message" objects and decoupled "handlers" that do the work!

... wait... that's not right, it's really...

Symfony's Messenger component gives you the power to execute code asynchronously via queues and workers!

Actually, it's both! Messenger is one of the newest parts of Symfony and we absolutely ❤️ it. In this tutorial, we'll create an important application that asynchronously adds our favorite cat (Ponka) to all of your favorite photos. Along the way, we'll learn to:

Create a messages classes
Add & configure "handler" classes that do the work
Dispatch messages through the bus
Configure "transports" for async messages
Route messages to transports
Execute "worker" processes that "consume" queued messages
Things fail!? Retry message and set up the "failure transport"
Middleware
Add & understand message stamps
Prioritized transports
A little CQRS: a Query bus
Testing & Dev: handling messages "sync"
Deployment and supervisor
RabbitMQ & AMQP

Let's get to work!

Syllabus

Installing Messenger
Message, Handler & the Bus
Doing Work in the Handler
Message, Handler & debug:messenger
Transport: Do Work Later (Async)
Worker Command
Problems with Entities in Messages
Passing Entity Ids inside of Messages
Dispatching a Message inside a Handler?
Partial Handler Failures & Advanced Routing
Envelopes & Stamps
Retrying on Failure
Retry Delay & Retry Strategy
The Failure Transport
Investigating & Retrying Failed Messages
Middleware
Tracking Messages with Middleware & a Stamp
Logger Channel Setup and Autowiring
Middleware Message Lifecycle Logging
High Priority Transports
Handling Messages Sync while Developing
Functional Test for the Upload Endpoint
Testing with the "in-memory" Transport
Deployment & Supervisor
Killing Workers Early & on Deploy
Events & Event Bus
Creating & Handling Events
Dispatching the Event & No Handlers
Messenger vs EventDispatcher
Doctrine Transaction & Validation Middleware
Event & Command Bus Organization
Query Bus
Advanced Handler Config: Handler Subscribers
Sending Handlers to Different Transports: from_transport
AMQP with RabbitMQ
AMQP Internals: Exchanges & Queues
AMQP Priority Exchange
Delaying in AMQP: Dead Letter Exchange
Exchange Routing and Binding Keys
Dynamic AMQP Routing Key (AmqpStamp)
Serializing Messages as JSON
JSON, Message Headers & Serializer Options
Setup for Messages from an Outside System
Transport for Consuming External Messages
Custom Transport Serializer
The Lifecycle of a Message & its Stamps
Graceful Failure in the Transport Serializer
Mapping Messages to Classes in a Transport Serializer

Taught by

Ryan Weaver

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An Introduction to Symfony Messenger

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