首先建立 工作exchange和工作queue，指定工作隊列的x-dead-letter-exchange到重試exchenge

    
      var 
    
    
      workQueueArgs = 
    
    
      new 
    
    
      Dictionary
    
    
      <
    
    
      string
    
    
      , 
    
    
      object
    
    
      > {

    { 
    
    
      "x-dead-letter-exchange"
    
    
      , RETRY_EXCHANGE },

};



channel.ExchangeDeclare(WORK_EXCHANGE, 
    
    
      "direct"
    
    
      );

channel.QueueDeclare(WORK_QUEUE, 
    
    
      true
    
    
      , 
    
    
      false
    
    
      , 
    
    
      false
    
    
      , workQueueArgs);

channel.QueueBind(WORK_QUEUE, WORK_EXCHANGE, 
    
    
      ""
    
    
      , 
    
    
      null
    
    
      );
    
  

之后建立重試exchange和重試queue

    
      var 
    
    
      queueArgs = 
    
    
      new 
    
    
      Dictionary
    
    
      <
    
    
      string
    
    
      , 
    
    
      object
    
    
      > {

    { 
    
    
      "x-dead-letter-exchange"
    
    
      , WORK_EXCHANGE },

    { 
    
    
      "x-message-ttl"
    
    
      , RETRY_DELAY }

};



channel.ExchangeDeclare(RETRY_EXCHANGE, 
    
    
      "direct"
    
    
      );

channel.QueueDeclare(RETRY_QUEUE, 
    
    
      true
    
    
      , 
    
    
      false
    
    
      , 
    
    
      false
    
    
      , queueArgs);

channel.QueueBind(RETRY_QUEUE, RETRY_EXCHANGE, 
    
    
      ""
    
    
      , 
    
    
      null
    
    
      );
    
  

重試隊列需要2個屬性，一個是 x-dead-letter-exchange，指向到工作exchange

一個是過期時間（這里等于是多少秒后重試）

?

監聽工作隊列，處理消息

    
      QueueingBasicConsumer 
    
    
      consumer = 
    
    
      new 
    
    
      QueueingBasicConsumer
    
    
      (channel);

channel.BasicConsume(WORK_QUEUE, 
    
    
      false
    
    
      , consumer);




    
    
      while 
    
    
      (
    
    
      true
    
    
      )

{

    
    
    
      BasicDeliverEventArgs 
    
    
      e = (
    
    
      BasicDeliverEventArgs
    
    
      )consumer.Queue.Dequeue();

    
    
    
      var 
    
    
      message = 
    
    
      Encoding
    
    
      .UTF8.GetString(e.Body);

    
    
    
      try

    
    
    
      {

        
    
    
      //throw new Exception("");

        
    
    
      channel.BasicAck(e.DeliveryTag, 
    
    
      false
    
    
      );

    }

    
    
    
      catch

    
    
    
      {

        channel.BasicNack(e.DeliveryTag, 
    
    
      false
    
    
      , 
    
    
      false
    
    
      );

    }

}
    
  

處理成功調用ack，處理不成功調用nack，

調用nack后，會根據工作隊列的x-dead-letter-exchange自動把消息發到重試隊列

重試隊列等幾秒（x-message-ttl）后，就認為是自動失敗了，又會根據重試隊列的x-dead-letter-exchange發送回工作隊列

rabbitmq使用dead letter機制來進行retry