Terminologies

• Queue: what you receive messages from
• Exchange: what you send messages to
• Binding: binds queues to exchanges
• Routing Key:
  - binding routing key: routing key is associated with a Binding
  - message routing key: routing key is specified when publishing a message

Exchange Types

• direct: sends messages to all bindings that the binding routing key matches the message routing key exactly
• fanout: sends messages to all bindings it knows about regardless of the routing key
• topic: is a more complex direct exchange where
  binding routing key can contain
  • *(star) which matches exactly one word
  • #(hash) which matchs zero or more word
  • example binding key: .orange., lazy.# message routing key: doted words for example lazy.orange.dog message are routed from exchange to bindings that matches the routing key according to the * and # rule

The default exchange:

An direct exchange with an empty string name which binds to all queues and a binding routing key set to the name of the queue.

#Message patterns:

Producer Consumer:

• message is only delivered to one consumer
• producer publish to a direct exchange(can also be the default exchange)
• consumer attached its queue to the exchange that producer is publishing
• can also use topic exchange

  PubSub:

• message delivered to multiple subscribers
• publisher publishes message to a fanout exchange
• subscriber creates a queue and bind it to the exchange
• subscriber listens to the queue

Topic:

In case of fanout exchange. the name of the exchange is the topic. Any listener interested in the topic connects its own queue to the exchange.

RPC:

can be done with any exchange as long as the message can arrive at the server’s listening queue client sends a request with a replyQueue and a correlationId
problems:

• PRC hides remote call cost. solution is to make it clear what call is RPC and what call is Local
• how should client react if client is not running
• request time out
• error feed back
• how should client react to a response with a not recognized correlationId( should be ignored because of duplicated response from server is a valid case)