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：