rabbitmq应用

 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 """
 @author: zengchunyun
 """
 import pika

 class MQServer(object):
     def __init__(self, host, port=5672, exchange=None, exchange_type="topic"):
         """
         初始化MQ设置
         :param host: MQ服务器地址
         :param port: MQ端口
         :param exchange: 交换器名称
         :param exchange_type: 交换器类型,默认关键字类型
         :return:
         """
         self.host = host
         self.port = port
         self.exchange = exchange
         self.exchange_type = exchange_type
         self.queue = None
         self.connection = self.connect()
         self.channel = self.connect_channel()
         self.create_exchange()

     def connect(self):
         """
         连接MQ服务器
         :return:
         """
         return pika.BlockingConnection(pika.ConnectionParameters(host=self.host, port=self.port))

     def connect_channel(self):
         """
         创建频道
         :return:
         """
         return self.connection.channel()

     def create_exchange(self):
         """
         定义交换器名称,防止发布时,如果交换器不存在,异常
         :return:
         """
         self.channel.exchange_declare(exchange=self.exchange, type=self.exchange_type)

     def publish(self, exchange=None, routing_key=None, body=None):
         """
         创建发布者
         :param exchange: 交换器名称
         :param routing_key: 路由KEY
         :param body:消息主体
         :return:
         """
         if exchange:
             self.exchange = exchange
         self.channel.basic_publish(exchange=self.exchange, routing_key=routing_key, body=body)
         self.close()

     def consumer(self, exchange=None, routing_key=None, callback=None):
         """
         创建消费者
         :param exchange:
         :param routing_key:
         :param callback:
         :return:
         """
         if exchange:
             self.exchange = exchange
         self.create_queue()
         self.channel.queue_bind(queue=self.queue, exchange=self.exchange, routing_key=routing_key)
         self.channel.basic_consume(consumer_callback=callback, queue=self.queue, no_ack=True)
         self.start()

     def create_queue(self):
         """
         生成队列,当关闭consumer时,加上exclusive=True,queue也会被删除
         :return:
         """
         self.queue = self.channel.queue_declare(exclusive=True).method.queue  # 为每个消费者生成不同的队列

     def close(self):
         """
         关闭消息连接
         :return:
         """
         self.connection.close()

     def start(self):
         self.channel.start_consuming()

1.消息持久化存储

　　虽然有了消息反馈机制，但如果rabbitmq自身挂掉的话，那么任务还是会丢失，所以需要将任务持久化存储起来，

durable=True  # 开启持久化设置，rabbitmq不允许使用不同的参数来重新定义存在的队列

self.queue = self.channel.queue_declare(exclusive=True,durable=True)  

self.channel.exchange_declare(exchange=self.exchange, type=self.exchange_type, durable=True)
在发送任务的时候，用delivery_mode＝2来标记任务为持久化存储

 self.channel.basic_publish(exchange='',
                       routing_key=routing_key,
                       body=message,
                       properties=pika.BasicProperties(
                          delivery_mode = 2, # make message persistent
                       ))

2.公平调度（fair dispatch)

虽然每个工作者是依次分配到任务，但是每个任务不一定一样，可能有到任务比较重，执行时间长，有的任务比较轻，执行时间短，如果能公平调度最好了，使用basic_qos设置prefetch_count=1，使得rabbitmq不会在同一时间给工作者分配多个任务，即只有工作者完成任务之后，才会再次接收到任务

 channel.basic_qos(prefetch_count=1)

完整示例代码

 #!/usr/bin/env python
 import pika
 import sys

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

 channel.queue_declare(queue='task_queue', durable=True)

 message = ' '.join(sys.argv[1:]) or "Hello World!"
 channel.basic_publish(exchange='',
                       routing_key='task_queue',
                       body=message,
                       properties=pika.BasicProperties(
                          delivery_mode = 2, # make message persistent
                       ))
 print (" [x] Sent %r" % (message,))
 connection.close()

消费者代码

 #!/usr/bin/env python
 import pika
 import time

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

 channel.queue_declare(queue='task_queue', durable=True)
 print( ' [*] Waiting for messages. To exit press CTRL+C')

 def callback(ch, method, properties, body):
     print (" [x] Received %r" % (body,))
     time.sleep( body.count('.') )
     print (" [x] Done")
     ch.basic_ack(delivery_tag = method.delivery_tag)

 channel.basic_qos(prefetch_count=1)
 channel.basic_consume(callback,
                       queue='task_queue')

 channel.start_consuming()