RabbitMQ

RabbitMQ From High-level Prospective

RabbitMQ is a message broker that implements an advanced message queuing protocol (AMQP)

AMQP: standardizes messaging using Producers, Brokers, and Consumers

Messaging increases loose coupling and scalability

Main components: Producers, Consumers, Exchange, Queue, Binding key, Message

Core Concepts:

• Producer emits messages to exchange
• The consumer receives messages from the queue
• Exchange compares routing key with Binding key
• Binding connects an exchange with a queue using a binding key

Binding exchange with queue through binding key

Messages distribution depends on the exchange type

Exchange type

• Default is nameless: send direct to queue name

• Fanout: broadcast message to all queues

• Direct: to specific queue if routing key = binding key 

• Topic: partial match if the binding key contains routing i.e (binding key ="red. green" and routing key ="red.*"

• Headers: message header instead of routing key

Queue characteristics:

• Name

• Durable (option allows the queue to survive even the RabbitMQ is down and restarted)

• Exclusive (used only by one connection (current connection) and will be deleted when that connection closes from the consumer side)

• Auto-delete (queue that has had at least one consumer is deleted when the last consumer unsubscribed)

• Arguments (optional; used by plugins and broker-specific features such as message TTL, queue length limit, etc)
• Transient: is the opposite of Durable as it is deleted if the broker restarted as it stored including messages in memory not like Durable stored in desk

Queue Types:

• Distributed and Replicated Queues

            - Queue can be classic or replicated in multiple clusters for load-balancing purposes

• Temporary Queues

              - Instead of deleting the queues you have created before you can declare or configure the queue to be temporary in 3 ways :

1. Exclusive queue 
2. TTLS (time to live)
3. Auto-delete queue

• Exclusive Queues

                - Get deleted by ending the connection after consuming

• Server-named Queues

                - Broker or rabbitMQ can generate a unique name for the queue by sending an empty string in the queue name argument as the queue name is required

Note:

- when you need to name the queue it should not start with "amq" as it reserved for internal use by rabbitmq or broker

Resources :

• https://www.rabbitmq.com/queues.html
• https://www.tutlane.com/tutorial/rabbitmq
• https://www.youtube.com/watch?v=deG25y_r6OY
• https://hevodata.com/learn/rabbitmq-queue-types/#t9