Message Broker

• A postal service.
  • A service which gets our messages from A -> B.
• Producer:
  • Sender of the message.
  • The sender of the letter in postal service example.
• Consumers:
  • The party who receives the message.

Async

• RabbitMQ works in async fashion.
  • Neither sender/receiver has to wait for the response.

Exchange

• The brain of our RabbitMQ.
• Makes the decision on who should receives which message.
• Inner working of a postal service.
• Different exchange types offers different types of services.
• A producer always sends its messages to an exchange.
  • Exchange pushes the messages to one or more queues.
  • Messages will remain in the queue until it is consumed by a consumer.

Queue

• Our letterbox.
• Consumer is responsible to consumes the messages.
• A message broker can have multiple queues.
• Queue declaration is an idempotent operation:
  • This means that we can define same queue as many times as we want to, but RabbitMQ will create it only once.

(Exchange) N:M (Queue)

• We can have queue who ain’t bound to any exchange.

Connection

• Every producer/consumer should open a single TCP connection to our RabbitMQ broker.
• A connection can have multiple channel.
  • Our producer can send messages to our broker using different isolated channels without having to interfering with each other.
  • Channels our resource friendlier than opening new connections.

AMQP

• Advanced Messaging Queuing Protocol.
• An open standard protocol for passing messages between apps.
• Implemented in Azure Server Bus, and RabbitMQ.
• Uses Remote Procedure Call.
  • Bidirectional.
• RabbitMQ uses commands to communicate between client (our python app) and RabbiMQ (broker).
  • Commands are classes, e.g. channel and declare is a method of channel.
  • All the data necessary for executing a command is in a data structure called frame.

Frames

• Method frame:
• Content header frame:
• Body frame:
• Heartbeat frame:

Different Patterns

• Competing consumer pattern.
• Pubsub pattern.