RabbitMQ（二）：实例demo



             和任何的Hello world一样，它们都不复杂。我们将会设计两个程序，一个发送Hello world，另一个接收这个数据并且打印到屏幕。
     整体的设计如下图：

1. 环境配置

RabbitMQ 实现了AMQP。因此，我们需要安装AMPQ的library。幸运的是对于多种编程语言都有实现。我们可以使用以下lib的任何一个：

• py-amqplib 
  
• txAMQP
  
• pika

在这里我们将使用pika. 可以通过 pip 包管理工具来安装:

$ sudo pip install pika==0.9.8

<span style="font-size:18px;">$ sudo pip install pika==0.9.8</span>

这个安装依赖于pip和Git-core。

• On Ubuntu:

  $ sudo apt-get install python-pip git-core
  

• On Debian:

  $ sudo apt-get install python-setuptools git-core
  $ sudo easy_install pip
  

• On Windows:To install easy_install, run the MS Windows Installer forsetuptools

  > easy_install pip
  > pip install pika==0.9.8
  

2. Sending

第一个program send.py：发送Hello world 到queue。正如我们在上篇文章提到的，你程序的第一句话就是建立连接，第二句话就是创建channel：

#!/usr/bin/env python
import pika

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

<span style="font-size:18px;">#!/usr/bin/env python
import pika

connection = pika.BlockingConnection(pika.ConnectionParameters(
               'localhost'))
channel = connection.channel()</span>

创建连接传入的参数就是RabbitMQ Server的ip或者name。

关于谁创建queue，上篇文章也讨论过：Producer和Consumer都应该去创建。

接下来我们创建名字为hello的queue：

channel.queue_declare(queue='hello')

<span style="font-size:18px;">channel.queue_declare(queue='hello')</span>

创建了channel，我们可以通过相应的命令来list queue：

$ sudo rabbitmqctl list_queues
Listing queues ...
hello    0
...done.

<span style="font-size:18px;">$ sudo rabbitmqctl list_queues
Listing queues ...
hello    0
...done.</span>

现在我们已经准备好了发送了。
从架构图可以看出，Producer只能发送到exchange，它是不能直接发送到queue的。现在我们使用默认的exchange（名字是空字符）。这个默认的exchange允许我们发送给指定的queue。routing_key就是指定的queue名字。

channel.basic_publish(exchange='',
                      routing_key='hello',
                      body='Hello World!')
print " [x] Sent 'Hello World!'"

<span style="font-size:18px;">channel.basic_publish(exchange='',
                      routing_key='hello',
                      body='Hello World!')
print " [x] Sent 'Hello World!'"
</span>

退出前别忘了关闭connection。

connection.close()

<span style="font-size:18px;">connection.close()</span>

3. Receiving

第二个program receive.py 将从queue中获取Message并且打印到屏幕。

第一步还是创建connection。第二步创建channel。第三步创建queue，name = hello：

channel.queue_declare(queue='hello')

<span style="font-size:18px;">channel.queue_declare(queue='hello')</span>

接下来要subscribe了。在这之前，需要声明一个回调函数来处理接收到的数据。

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

<span style="font-size:18px;">def callback(ch, method, properties, body):
    print " [x] Received %r" % (body,)</span>

subscribe：

channel.basic_consume(callback,
                      queue='hello',
                      no_ack=True)

<span style="font-size:18px;">channel.basic_consume(callback,
                      queue='hello',
                      no_ack=True)</span>

最后，准备好无限循环监听吧：

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

<span style="font-size:18px;">print ' [*] Waiting for messages. To exit press CTRL+C'
channel.start_consuming()</span>

4. 最终版本

send.py:

#!/usr/bin/env python
import pika

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

channel.queue_declare(queue='hello')

channel.basic_publish(exchange='',
                      routing_key='hello',
                      body='Hello World!')
print " [x] Sent 'Hello World!'"
connection.close()

<span style="font-size:18px;">#!/usr/bin/env python
import pika

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

channel.queue_declare(queue='hello')

channel.basic_publish(exchange='',
                      routing_key='hello',
                      body='Hello World!')
print " [x] Sent 'Hello World!'"
connection.close()</span>

 receive.py:

#!/usr/bin/env python
import pika

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

channel.queue_declare(queue='hello')

print ' [*] Waiting for messages. To exit press CTRL+C'

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

channel.basic_consume(callback,
                      queue='hello',
                      no_ack=True)

channel.start_consuming()

<span style="font-size:18px;">#!/usr/bin/env python
import pika

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

channel.queue_declare(queue='hello')

print ' [*] Waiting for messages. To exit press CTRL+C'

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

channel.basic_consume(callback,
                      queue='hello',
                      no_ack=True)

channel.start_consuming()</span>

5. 最终运行

先运行 send.py program:

$ python send.py
[x] Sent 'Hello World!'

<span style="font-size:18px;"> $ python send.py
 [x] Sent 'Hello World!'</span>

send.py 每次运行完都会停止。注意：现在数据已经存到queue里了。接收它：

$ python receive.py
[*] Waiting for messages. To exit press CTRL+C
[x] Received 'Hello World!'