死信队列常用于订单超时自动取消，会议预订提前提醒等等。

• 发布者代码：

import pika
import json
import time

credentials = pika.PlainCredentials('admin', 'admin')  # mq用户名和密码
# 虚拟队列需要指定参数 virtual_host，如果是默认的可以不填。
connection = pika.BlockingConnection(pika.ConnectionParameters(host='127.0.0.1', port=5672, credentials=credentials))
channel = connection.channel()
# 声明消息队列，消息将在这个队列传递，如不存在，则创建
queue_name = "delay_queue_a"
exchange = 'delay_exchange_a'
routing_key = 'delay_routing_key_a'
dead_letter_exchange = 'dead_exchange_a'  # 'amq.direct'#'dead_exchange_a'
dead_letter_routing_key = 'dead_letter_routing_key_a'  # 'dead_queue_a'#'dead_letter_routing_key_a'
arguments = {
    "x-message-ttl": 5000,
    'x-dead-letter-exchange': dead_letter_exchange,
    'x-dead-letter-routing-key': dead_letter_routing_key
}

channel.confirm_delivery()

channel.exchange_declare(exchange=exchange, durable=True, exchange_type='direct')
result = channel.queue_declare(queue=queue_name, durable=False, arguments=arguments)
channel.queue_bind(exchange=exchange, queue=queue_name, routing_key=routing_key)
for i in range(10):
    message = json.dumps({'OrderId': i})
    # 向队列插入数值 routing_key是队列名
    channel.basic_publish(exchange=exchange, routing_key=routing_key, body=message,
                          properties=pika.BasicProperties(delivery_mode=2))
    print(message)
    time.sleep(1.5)

connection.close()

• 消费端代码

import pika
import json

credentials = pika.PlainCredentials('admin', 'admin')

connection = pika.BlockingConnection(pika.ConnectionParameters(host='127.0.0.1', port=5672, credentials=credentials))

channel = connection.channel()
# 申明消息队列，消息在这个队列传递，如果不存在，则创建队列
queue_name = "dead_queue_a"
# dead_letter_exchange = 'amq.direct'#'dead_exchange_a'
dead_letter_exchange = 'dead_exchange_a'
dead_letter_routing_key = 'dead_letter_routing_key_a'
# queue_name = dead_letter_routing_key
channel.exchange_declare(exchange=dead_letter_exchange, durable=False, exchange_type='direct')
result = channel.queue_declare(queue=queue_name, durable=False)

channel.queue_bind(exchange=dead_letter_exchange, queue=queue_name, routing_key=dead_letter_routing_key)


# 定义一个回调函数来处理消息队列中的消息，这里是打印出来
def callback(ch, method, properties, body):
    data = json.loads(body.decode())
    print(data)
    ch.basic_ack(delivery_tag=method.delivery_tag)


# 告诉rabbitmq，用callback来接收消息
channel.basic_consume(queue_name, callback,  
                      auto_ack=False)
print('开始监听')

try:
    channel.start_consuming()
except KeyboardInterrupt:
    channel.stop_consuming()
    connection.close()
    print('close')