RabbitMQ消息队列（五）：Routing 消息路由_多个queue对应一个routekey

作者：繁依Fanyi0 | 2024-04-16 02:18:51

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多个queue对应一个routekey

上篇文章中，我们构建了一个简单的日志系统。接下来，我们将丰富它：能够使用不同的severity来监听不同等级的log。比如我们希望只有error的log才保存到磁盘上。

1. Bindings绑定

上篇文章中我们是这么做的绑定：

[python] view plain copy

channel.queue_bind(exchange=exchange_name,
queue=queue_name)

绑定其实就是关联了exchange和queue。或者这么说：queue对exchagne的内容感兴趣，exchange要把它的Message deliver到queue中。实际上，绑定可以带 routing_key 这个参数。其实这个参数的名称和 basic_publish 的参数名是相同了。为了避免混淆，我们把它成为binding key。
使用一个key来创建binding :

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

对于fanout的exchange来说，这个参数是被忽略的。

2. Direct exchange

Direct exchange的路由算法非常简单：通过binding key的完全匹配，可以通过下图来说明。

exchange X和两个queue绑定在一起。Q1的binding key是orange。Q2的binding key是black和green。
当P publish key是orange时，exchange会把它放到Q1。如果是black或者green那么就会到Q2。其余的Message都会被丢弃。

3. Multiple bindings

多个queue绑定同一个key是可以的。对于下图的例子，Q1和Q2都绑定了black。也就是说，对于routing key是black的Message，会被deliver到Q1和Q2。其余的Message都会被丢弃。

4. Emitting logs

首先是我们要创建一个direct的exchange：

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

我们将使用log的severity作为routing key，这样Consumer可以针对不同severity的log进行不同的处理。
publish：

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channel.basic_publish(exchange='direct_logs',
routing_key=severity,
body=message)

我们使用三种severity：'info', 'warning', 'error'.

5. Subscribing

对于queue，我们需要绑定severity：

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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)

6. 最终版本

The code for emit_log_direct.py:

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#!/usr/bin/env python
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(
host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs',
type='direct')
severity = sys.argv[1] if len(sys.argv) > 1 else 'info'
message = ' '.join(sys.argv[2:]) or 'Hello World!'
channel.basic_publish(exchange='direct_logs',
routing_key=severity,
body=message)
print " [x] Sent %r:%r" % (severity, message)
connection.close()

The code for receive_logs_direct.py:

[python] view plain copy

#!/usr/bin/env python
import pika
import sys
connection = pika.BlockingConnection(pika.ConnectionParameters(
host='localhost'))
channel = connection.channel()
channel.exchange_declare(exchange='direct_logs',
type='direct')
result = channel.queue_declare(exclusive=True)
queue_name = result.method.queue
severities = sys.argv[1:]
if not severities:
print >> sys.stderr, "Usage: %s [info] [warning] [error]" % \
(sys.argv[0],)
sys.exit(1)
for severity in severities:
channel.queue_bind(exchange='direct_logs',
queue=queue_name,
routing_key=severity)
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()

我们想把warning和error的log记录到一个文件中：

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$ python receive_logs_direct.py warning error > logs_from_rabbit.log

打印所有log到屏幕：

[python] view plain copy

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

尊重原创，转载请注明出处 anzhsoft: http://blog.csdn.net/anzhsoft/article/details/19630147

参考资料：

1. http://www.rabbitmq.com/tutorials/tutorial-four-python.html

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