python中RabbitMQ的使用（远程过程调用RPC）

在RabbitMQ消息队列中，往往接收者、发送者不止是一个身份。例如接接收者收到消息并且需要返回给发送者。

此时接收者、发送者的身份不再固定！

我们来模拟该情形：

假设有客户端client，服务端server。

我们需要从客户端发送数据，通过服务端的计算后再返回给客户端。

client.py

 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 import pika
 import uuid

 class Client(object):
     def __init__(self):
         hostname = '192.168.1.133'
         parameters = pika.ConnectionParameters(hostname)
         self.connection = pika.BlockingConnection(parameters)

         self.channel = self.connection.channel()
         # 定义接收返回消息的队列
         result = self.channel.queue_declare(exclusive=True)
         self.callback_queue = result.method.queue

         self.channel.basic_consume(self.on_response,
                                    no_ack=True,
                                    queue=self.callback_queue)
         self.response = None
         self.corr_id = ''

     # 定义接收到返回消息的处理方法
     def on_response(self, ch, method, props, body):
         if self.corr_id == props.correlation_id:
             self.response = body

     def request(self, n):
         # self.response = None
         self.corr_id = str(uuid.uuid4())
         # 发送计算请求，并声明返回队列
         self.channel.basic_publish(exchange='',
                                    routing_key='count_queue',
                                    properties=pika.BasicProperties(
                                        reply_to=self.callback_queue,
                                        correlation_id=self.corr_id,
                                    ),
                                    body=str(n))
         # 接收返回的数据
         while self.response is None:
             self.connection.process_data_events()
         return int(self.response)

 client = Client()

 print " [*] Requesting fib(30)"
 response = client.request(30)
 print " [*] Got fib(30)= %r" % response

server.py

 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 import pika

 hostname = '192.168.1.133'
 parameters = pika.ConnectionParameters(hostname)
 connection = pika.BlockingConnection(parameters)

 # 创建通道
 channel = connection.channel()
 # 声明队列
 channel.queue_declare(queue='count_queue')
 print ' [*] Waiting for n'

 # 算法
 def fib(n):
     if n == 0:
         return 0
     elif n == 1:
         return 1
     else:
         return fib(n - 1) + fib(n - 2)

 # 设置回调函数
 def on_request(ch, method, props, body):
     n = int(body)
     response = fib(n)
     print " [*] fib(%s)" % n, '=', response
     # 将结果反馈
     ch.basic_publish(exchange='',
                      routing_key=props.reply_to,
                      properties=pika.BasicProperties(correlation_id=props.correlation_id),
                      body=str(response))
     ch.basic_ack(delivery_tag=method.delivery_tag)

 #公平调度
 channel.basic_qos(prefetch_count=1)
 channel.basic_consume(on_request, queue='count_queue')
 print " [*] Awaiting count_queue requests"
 channel.start_consuming()

结果如下：

服务端：                                                                         客户端：