如何通过Python实现RabbitMQ延迟队列

"""
Created on Fri Aug 3 17:00:44 2018

@author: Bge
"""
import pika,json,logging
class RabbitMQClient:
  def __init__(self, conn_str='amqp://user:pwd@host:port/%2F'):
    self.exchange_type = "direct"
    self.connection_string = conn_str
    self.connection = pika.BlockingConnection(pika.URLParameters(self.connection_string))
    self.channel = self.connection.channel()
    self._declare_retry_queue() #RetryQueue and RetryExchange
    logging.debug("connection established")
  def close_connection(self):
    self.connection.close()
    logging.debug("connection closed")
  def declare_exchange(self, exchange):
    self.channel.exchange_declare(exchange=exchange,
                   exchange_type=self.exchange_type,
                   durable=True)
  def declare_queue(self, queue):
    self.channel.queue_declare(queue=queue,
                  durable=True,)
  def declare_delay_queue(self, queue,DLX='RetryExchange',TTL=60000):
    """
    创建延迟队列
    :param TTL: ttl的单位是us，ttl=60000 表示 60s
    :param queue:
    :param DLX:死信转发的exchange
    :return:
    """
    arguments={}
    if DLX:
      #设置死信转发的exchange
      arguments[ 'x-dead-letter-exchange']=DLX
    if TTL:
      arguments['x-message-ttl']=TTL
    print(arguments)
    self.channel.queue_declare(queue=queue,
                  durable=True,
                  arguments=arguments)
  def _declare_retry_queue(self):
    """
    创建异常交换器和队列，用于存放没有正常处理的消息。
    :return:
    """
    self.channel.exchange_declare(exchange='RetryExchange',
                   exchange_type='fanout',
                   durable=True)
    self.channel.queue_declare(queue='RetryQueue',
                  durable=True)
    self.channel.queue_bind('RetryQueue', 'RetryExchange','RetryQueue')
  def publish_message(self,routing_key, msg,exchange='',delay=0,TTL=None):
    """
    发送消息到指定的交换器
    :param exchange: RabbitMQ交换器
    :param msg: 消息实体，是一个序列化的JSON字符串
    :return:
    """
    if delay==0:
      self.declare_queue(routing_key)
    else:
      self.declare_delay_queue(routing_key,TTL=TTL)
    if exchange!='':
      self.declare_exchange(exchange)
    self.channel.basic_publish(exchange=exchange,
                  routing_key=routing_key,
                  body=msg,
                  properties=pika.BasicProperties(
                    delivery_mode=2,
                    type=exchange
                  ))
    self.close_connection()
    print("message send out to %s" % exchange)
    logging.debug("message send out to %s" % exchange)
  def start_consume(self,callback,queue='#',delay=1):
    """
    启动消费者，开始消费RabbitMQ中的消息
    :return:
    """
    if delay==1:
      queue='RetryQueue'
    else:
      self.declare_queue(queue)
    self.channel.basic_qos(prefetch_count=1)
    try:
      self.channel.basic_consume( # 消费消息
        callback, # 如果收到消息，就调用callback函数来处理消息
        queue=queue, # 你要从那个队列里收消息
      )
      self.channel.start_consuming()
    except KeyboardInterrupt:
      self.stop_consuming()
  def stop_consuming(self):
    self.channel.stop_consuming()
    self.close_connection()
  def message_handle_successfully(channel, method):
    """
    如果消息处理正常完成，必须调用此方法，
    否则RabbitMQ会认为消息处理不成功，重新将消息放回待执行队列中
    :param channel: 回调函数的channel参数
    :param method: 回调函数的method参数
    :return:
    """
    channel.basic_ack(delivery_tag=method.delivery_tag)
  def message_handle_failed(channel, method):
    """
    如果消息处理失败，应该调用此方法，会自动将消息放入异常队列
    :param channel: 回调函数的channel参数
    :param method: 回调函数的method参数
    :return:
    """
    channel.basic_reject(delivery_tag=method.delivery_tag, requeue=False)

from MQ.RabbitMQ import RabbitMQClient
print("start program")
client = RabbitMQClient()
msg1 = '{"key":"value"}'
client.publish_message('test-delay',msg1,delay=1,TTL=10000)
print("message send out")

from MQ.RabbitMQ import RabbitMQClient
import json
print("start program")
client = RabbitMQClient()
def callback(ch, method, properties, body):
    msg = body.decode()
    print(msg)
    # 如果处理成功，则调用此消息回复ack，表示消息成功处理完成。
    RabbitMQClient.message_handle_successfully(ch, method)
queue_name = "RetryQueue"
client.start_consume(callback,queue_name,delay=0)