使用 pika 时消息队列中的 exchange 和 routing_key 是什么？

Question

I was setting uprabitMQ as message queue to use with my Django application. According to the documentation I need to specify the exchange and routing key to the queue. What I don't understand is what exactly are both of them and what do we use it for. Also can one queue only have one routing key?

#!/usr/bin/env python
import pika
credentials = pika.PlainCredentials('username', 'password')
parameters = pika.ConnectionParameters('IPADDRESS', 5672, 'vhostcheck', credentials)

connection = pika.BlockingConnection(parameters)
channel = connection.channel()

channel.queue_declare(queue='testqueue')
channel.basic_publish(exchange='',
                  routing_key='hello',
                  body='Hello W0rld!!')
print("Sent 'Hello World!'")
connection.close()

In channel.basic_publish(exchange='', routing_key='hello', body='Hello W0rld!!') , what are exchange and routing_key and what do we use it for?

Answer 1

This is explained nicely in the relevant documentation( https://www.rabbitmq.com/tutorials/tutorial-one-python.html ). For exchange='': this is the "default exchange identified by an empty string. This exchange is special ‒ it allows us to specify exactly to which queue the message should go". And for routing_key='hello': "the queue name needs to be specified in the routing_key parameter". The documentation also explains the related terms clearly, such as "exchange", "queue", and so on. This is one of the simplest possible configurations for Rabbit - just to get you started.