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消息路由

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消息路由

很多时候某个消费者只应该接受某些消息，对于这种情况广播就不适用，最简单的消息路由是direct exchange

Binding Key

可以额外传递参数routing_key给binding，为了与队列的routing_key区分，这个参数被称为binding key 

channel.queue_bind(exchange=exchange_name,
                   queue=queue_name,
                   routing_key='black')

Direct Exchange

对于fanout exchange来说，binding key毫无意义，但对于direct exchange来说，只有当队列的routing_key与exchange的binding key相同的时候，exchange才会把消息推送给这个队列

direct-exchange.png

Figure 1: direct exchanges

多重Binding　

可以把一个direct exchange绑定到多个具有相同routing key的队列上

direct-exchange-multiple.png

Figure 2: multiple binding

根据日志级别做路由

route.png

Figure 3: route by log serverity

  • 生产者创建direct exchange 
    channel.exchange_declare(exchange='direct_logs',
                         type='direct')
  • 生产者根据日志级别发送给不同的队列，队列的routing key就是日志级别 
    channel.basic_publish(exchange='direct_logs',
                      routing_key=severity,
                      body=message)
  • 消费者为每个日志级别分别建立一个binding 
    result = channel.queue_declare(exclusive=True)
queue_name = result.method.queue

for severity in severities:
    channel.queue_bind(exchange='direct_logs',
                       queue=queue_name,
                       routing_key=severity)

测试

启动一个消费者只接受warning和error级别日志到文件 

$ python receive_logs_direct.py warning error > logs_from_rabbit.log

启动另外一个消费者接受所有级别日志，并打印到终端 

$ python receive_logs_direct.py info warning error
 [*] Waiting for logs. To exit press CTRL+C

生产一条error级别的日志 

$ python emit_log_direct.py error "Run. Run. Or it will explode."
[x] Sent 'error':'Run. Run. Or it will explode.'

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