RabbitMQ--RPC实现

不知道你有没有发现，生产者到消费者的流都是单向的，如果远程的机器执行完返回结果，这种模式叫什么呢，RPC（远程过程调用）

RabbitMQ能不能返回呢，怎么返回呢？

返回时，再建立一个queue，把结果发送新的queue里

 

RPC client

import pika
import uuid
import time
class FibonacciRpcClient(object):
    def __init__(self):
        self.connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
        self.channel = self.connection.channel()
        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)   # 只要一收到消息就调用on_response
                                                        
    def on_response(self, ch, method, props, body):  # 必须四个参数
        # 如果收到的ID和本机生成的相同，则返回的结果就是我想要的指令返回的结果
        if self.corr_id == props.correlation_id:
            self.response = body

    def call(self, n):
        self.response = None  # 初始self.response为None
        self.corr_id = str(uuid.uuid4())  # 随机唯一字符串
        self.channel.basic_publish(
                exchange='',
                routing_key='rpc_queue',  # 发消息到rpc_queue
                properties=pika.BasicProperties(  # 消息持久化
                    reply_to = self.callback_queue,  # 让服务端命令结果返回到callback_queue
                    correlation_id = self.corr_id,  # 把随机uuid同时发给服务器
                ),
                body=str(n)
        )
        while self.response is None:  # 当没有数据，就一直循环
            # 启动后，on_response函数接到消息，self.response 值就不为空了
            self.connection.process_data_events()  # 非阻塞版的start_consuming()
            # print("no msg……")
            # time.sleep(0.5)
        # 收到消息就调用on_response
        return int(self.response)

if __name__ == '__main__':
    fibonacci_rpc = FibonacciRpcClient()
    print(" Requesting fib(7)")
    response = fibonacci_rpc.call(7)
    print(" Got %r" % response)

RPC server

import pika
import time

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

def on_request(ch, method, props, body):
    n = int(body)
    print(" [.] fib(%s)" % n)
    response = fib(n)

    ch.basic_publish(
            exchange='',  # 把执行结果发回给客户端
            routing_key=props.reply_to,  # 客户端要求返回用的queue
            properties=pika.BasicProperties(correlation_id = props.correlation_id), # 返回客户端发过来的correction_id 为了让客户端验证消息一致性
            body=str(response)
    )
    ch.basic_ack(delivery_tag = method.delivery_tag)  # 任务完成时告诉客户端

if __name__ == '__main__':
    connection = pika.BlockingConnection(pika.ConnectionParameters(host='localhost'))
    channel = connection.channel()
    channel.queue_declare(queue='rpc_queue')  # 声明一个rpc_queue
    channel.basic_qos(prefetch_count=1)
    # 在rpc_queue里收消息,收到消息就调用on_request
    channel.basic_consume(on_request, queue='rpc_queue')
    print(" Awaiting RPC requests")
    channel.start_consuming()