RabbitMq死信隊列

死信隊列的作用

死信交換機有什麼用呢？ 在創建隊列的時候 可以給這個隊列附帶一個交換機， 那麼這個隊列作廢的消息就會被重新發到附帶的交換機，然後讓這個交換機重新路由這條消息。

死信消息產生的來源

• 消息被拒絕（basic.reject或basic.nack）並且requeue=false
• 消息TTL過期
• 隊列達到最大長度（隊列滿了，無法再添加數據到mq中）

死信隊列處理的方式

• 丟棄，如果不是很重要，可以選擇丟棄
• 記錄死信入庫，然後做後續的業務分析或處理
• 通過死信隊列，由負責監聽死信的應用程序進行處理
  

消息超時進入死信隊列

通俗的說，就是消息產生之後，因爲設置了超時時間，在這段時間內消息沒有被消費就會被扔到死信隊列裏面。

 // 交換機名稱
    private static final String DESTINATION_NAME = "rabbitMq_topic";
    //消息隊列
    private static final String queueName = "topic_queue";
    //routingKey
    private static final String routingKey = "topic.#";

    //配置死信隊列
    private static final String dlxExchangeName = "dlx.exchange";
    private static final String dlxQueueName = "dlx.queue";
    private static final String dlxRoutingKey = "#";

    @Test
    public void producer() throws IOException, TimeoutException {
        //獲取連接
        Connection connection = MQConnectionUtils.newConnection();
        //創建通道
        Channel channel = connection.createChannel();
        Map<String, Object> arguments = new HashMap<String, Object>(16);
        // 爲隊列設置隊列交換器
        arguments.put("x-dead-letter-exchange", dlxExchangeName);
        // 設置隊列中的消息 60s 鍾後過期
        arguments.put("x-message-ttl", 60000);
        //正常生產者綁定交換機 參數1 交換機名稱 參數2 交換機類型
        channel.exchangeDeclare(DESTINATION_NAME, "topic", true, false, null);
        //消費聲明隊列
        channel.queueDeclare(queueName, true, false, false, arguments);
        //消費者隊列綁定交換機 綁定路由件 路由鍵
        channel.queueBind(queueName, DESTINATION_NAME, routingKey);

        String message = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + " 測試消息超時，傳遞到死信隊列";

        // 創建死信交換器和隊列
        channel.exchangeDeclare(dlxExchangeName, "topic", true, false, null);
        channel.queueDeclare(dlxQueueName, true, false, false, null);
        channel.queueBind(dlxQueueName, dlxExchangeName, dlxRoutingKey);

        //生產者發送消息者
        channel.basicPublish(DESTINATION_NAME, routingKey, MessageProperties.PERSISTENT_TEXT_PLAIN, message.getBytes());
        System.err.println("消息發送完成......");

    }

只監聽了死信隊列的消息，正常消息無需監聽接收

    /**
     * 監聽死信隊列
     *
     * @throws IOException
     * @throws TimeoutException
     * @throws InterruptedException
     */
    @Test
    public void dlxConsumer() throws IOException, TimeoutException, InterruptedException {
        //獲取連接
        Connection connection = MQConnectionUtils.newConnection();
        //創建通道
        Channel channel = connection.createChannel();
        System.out.println("死信消費者啓動 ..........");
        Thread.sleep(65000);
        com.rabbitmq.client.Consumer consumer = new DefaultConsumer(channel) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
                System.err.println("死信隊列接收到消息：" + new String(body));
                System.err.println("deliveryTag:" + envelope.getDeliveryTag());
                channel.basicAck(envelope.getDeliveryTag(), false);
            }
        };
        channel.basicConsume(dlxQueueName, consumer);
    }

消息被退回

這個我在之前的整合SpringBoot的時候有實驗過。

channel.basicNack(envelope.getDeliveryTag(),false,false);

隊列達到最大長度

這個和消息超時差不多，只不過是設置了隊列的最大容量而已。
只需要把上面的代碼修改一下就可以了。

    @Test
    public void producer() throws IOException, TimeoutException {
        //獲取連接
        Connection connection = MQConnectionUtils.newConnection();
        //創建通道
        Channel channel = connection.createChannel();

        Map<String, Object> arguments = new HashMap<String, Object>(16);
        // 爲隊列設置隊列交換器
        arguments.put("x-dead-letter-exchange", dlxExchangeName);
        //設置隊列長度爲3
        arguments.put("x-max-length", 3);
        //正常生產者綁定交換機 參數1 交換機名稱 參數2 交換機類型
        channel.exchangeDeclare(DESTINATION_NAME, "topic", true, false, null);
        //消費聲明隊列
        channel.queueDeclare(queueName, true, false, false, arguments);
        //消費者隊列綁定交換機 綁定路由件 路由鍵
        channel.queueBind(queueName, DESTINATION_NAME, routingKey);

        String message = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) + " 測試消息超時，傳遞到死信隊列";

        // 創建死信交換器和隊列
        channel.exchangeDeclare(dlxExchangeName, "topic", true, false, null);
        channel.queueDeclare(dlxQueueName, true, false, false, null);
        channel.queueBind(dlxQueueName, dlxExchangeName, dlxRoutingKey);

        //生產者發送消息者
        for (int i = 0; i < 5; i++) {
            channel.basicPublish(DESTINATION_NAME, routingKey, MessageProperties.PERSISTENT_TEXT_PLAIN, (message+i).getBytes());
        }
        System.out.println("消息發送完成......");
    }

 @Test
    public void consumer() throws IOException, TimeoutException, InterruptedException {
        //獲取連接
        Connection connection = MQConnectionUtils.newConnection();
        //創建通道
        Channel channel = connection.createChannel();
        //此處設置一次只消費1個,且必須是ASK之後的消息才能算
        channel.basicQos(1);
        System.out.println("消費者啓動 ..........");
        com.rabbitmq.client.Consumer consumer = new DefaultConsumer(channel) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
                System.out.println("正常隊列：" + new String(body));
                System.out.println("deliveryTag:" + envelope.getDeliveryTag());
                channel.basicAck(envelope.getDeliveryTag(), false);
            }
        };
        channel.basicConsume(queueName, consumer);
    }

    /**
     * 監聽死信隊列
     *
     * @throws IOException
     * @throws TimeoutException
     * @throws InterruptedException
     */
    @Test
    public void dlxConsumer() throws IOException, TimeoutException, InterruptedException {
        //獲取連接
        Connection connection = MQConnectionUtils.newConnection();
        //創建通道
        Channel channel = connection.createChannel();
        System.out.println("死信消費者啓動 ..........");
        com.rabbitmq.client.Consumer consumer = new DefaultConsumer(channel) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
                System.err.println("死信隊列接收到消息：" + new String(body));
                System.err.println("deliveryTag:" + envelope.getDeliveryTag());
                channel.basicAck(envelope.getDeliveryTag(), false);
            }
        };
        channel.basicConsume(dlxQueueName, consumer);
    }