python使用rabbitMQ介绍四（路由模式）

一、模式介绍

路由模式，与发布-订阅模式一样，消息发送到exchange中，消费者把队列绑定到exchange上。

这种模式在exchange上添加添加了一个路由键（routing-key），生产者发布消息的时候添加路由键（routing-key），消费者绑定队列到交换机时添加键值（routing-key），这样就可以接收到对应的消息。

路由模式的direct exchange。

队列模型：

与发布-订阅模式不同的是，每个消费者队列接收的消息不同，根据消息的routing-key把消息发送到不同的队列中。

当所有的消费队列绑定的routing-key一样时，路由模式行为与发布-订阅模式一样。

二、代码示意 

发布者：不再创建队列，发送消息到exchange（交换机）中。exchange_type为direct。

import pika
import sys

connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
channel = connection.channel()

channel.exchange_declare(exchange='direct_logs',
                         exchange_type='direct')

severity = ['info', 'warning', 'error']
for i in range(20):
    message = '{} Hello World! {}'.format(i, severity[i % 3])
    channel.basic_publish(exchange='direct_logs',
                          routing_key=severity[i % 3],
                          body=message)
    print(" [x] Sent: {}".format(message))
connection.close()

每个消费者绑定的队列定义不同的routing-key，接收到不同的消息。

以info为示例：

import pika
import sys

connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
channel = connection.channel()

channel.exchange_declare(exchange='direct_logs',
                         exchange_type='direct')

result = channel.queue_declare(exclusive=True)
queue_name = result.method.queue

channel.queue_bind(exchange='direct_logs',
                   queue=queue_name,
                   routing_key='info')

print(' [*] Waiting for logs. To exit press CTRL+C')

def callback(ch, method, properties, body):
    print(" [x] %r:%r" % (method.routing_key, body))

channel.basic_consume(callback,
                      queue=queue_name,
                      no_ack=True)

channel.start_consuming()

执行结果输出：

发布者：

[x] Sent: 0 Hello World! info
 [x] Sent: 1 Hello World! warning
 [x] Sent: 2 Hello World! error
 [x] Sent: 3 Hello World! info
 [x] Sent: 4 Hello World! warning
 [x] Sent: 5 Hello World! error
 [x] Sent: 6 Hello World! info
 [x] Sent: 7 Hello World! warning
 [x] Sent: 8 Hello World! error
 [x] Sent: 9 Hello World! info
 [x] Sent: 10 Hello World! warning
 [x] Sent: 11 Hello World! error
 [x] Sent: 12 Hello World! info
 [x] Sent: 13 Hello World! warning
 [x] Sent: 14 Hello World! error
 [x] Sent: 15 Hello World! info
 [x] Sent: 16 Hello World! warning
 [x] Sent: 17 Hello World! error
 [x] Sent: 18 Hello World! info
 [x] Sent: 19 Hello World! warning

Info输出：

[*] Waiting for logs. To exit press CTRL+C
 [x] 'info':b'0 Hello World! info'
 [x] 'info':b'3 Hello World! info'
 [x] 'info':b'6 Hello World! info'
 [x] 'info':b'9 Hello World! info'
 [x] 'info':b'12 Hello World! info'
 [x] 'info':b'15 Hello World! info'
 [x] 'info':b'18 Hello World! info'

Warning输出：

[*] Waiting for logs. To exit press CTRL+C
 [x] 'warning':b'1 Hello World! warning'
 [x] 'warning':b'4 Hello World! warning'
 [x] 'warning':b'7 Hello World! warning'
 [x] 'warning':b'10 Hello World! warning'
 [x] 'warning':b'13 Hello World! warning'
 [x] 'warning':b'16 Hello World! warning'
 [x] 'warning':b'19 Hello World! warning'

Error输出：

[*] Waiting for logs. To exit press CTRL+C
 [x] 'error':b'2 Hello World! error'
 [x] 'error':b'5 Hello World! error'
 [x] 'error':b'8 Hello World! error'
 [x] 'error':b'11 Hello World! error'
 [x] 'error':b'14 Hello World! error'
 [x] 'error':b'17 Hello World! error'

可以看到，不同的消费者收到不同级别的日志信息。

三、队列信息

管理页面，exchange页面，点击“direct_logs”上查看队列情况，可以看到三个不同routing_key的队列

routing key列展示了对应的key。