RabbitMQ消费端ACK与重回队列机制，TTL，死信队列详解（十一）
消费端的手工ACK和NACK
消费端进行消费的时候，如果由于业务异常我们可以进行日志的记录，然后进行补偿。
如果由于服务器宕机等严重问题，那么我们就需要手工进行ACK保障消费端成功。
消费端重回队列
为了对没有处理成功的消息，把消息重新回递给Broker。
一般我们在实际应用中，都会关闭重回队列，也就是设置为false。
//生产端代码
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(5672);
connectionFactory.setVirtualHost("/");
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
String exchange = "test_ack_exchange";
String routingKey = "ack.save";
for(int i =0; i<5; i ++){
Map<String, Object> headers = new HashMap<String, Object>();
headers.put("num", i);
AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
.deliveryMode(2)
.contentEncoding("UTF-8")
.headers(headers)
.build();
String msg = "Hello RabbitMQ ACK Message " + i;
channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());
}
//消费端代码
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(5672);
connectionFactory.setVirtualHost("/");
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
String exchangeName = "test_ack_exchange";
String queueName = "test_ack_queue";
String routingKey = "ack.#";
channel.exchangeDeclare(exchangeName, "topic", true, false, null);
channel.queueDeclare(queueName, true, false, false, null);
channel.queueBind(queueName, exchangeName, routingKey);
// 手工签收 必须要关闭 autoAck = false
channel.basicConsume(queueName, false, new MyConsumer(channel));
//自定义消费者
private Channel channel ;
public MyConsumer(Channel channel) {
super(channel);
this.channel = channel;
}
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
System.err.println("-----------consume message----------");
System.err.println("body: " + new String(body));
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
if((Integer)properties.getHeaders().get("num") == 0) {
channel.basicNack(envelope.getDeliveryTag(), false, true);
} else {
channel.basicAck(envelope.getDeliveryTag(), false);
}
}
TTL队列/消息
TTL是time to live的缩写,也就是生存时间
RabbitMQ支持消息的过期时间，在消息发送时可以进行指定
RabbitMQ支持队列的过期时间，从消息入队列开始计算，只要超过了队列的超过时间配置，那么消息会自动的清除。
消息10s过期，TTL是队列过期时间。
DLX死信队列
DLX，Dead-Letter-Exchange
利用DLX，当消息在一个队列中变成死信之后，它能够被重新publish到另一个exchange，这个exchange就是DLX。
消息变成死信情况：
消息被拒绝（basic.reject/basic.nack）并且request=false
消息TTL过期
队列达到最大的长度
DLX也是一个正常的exchange，和一般的exchange没有区别，他能在任何的队列上被指定，实际上就是设置某个队列的属性。
当这个队列中有死信时，RabbitMQ就会自动的将这个消息重新发布到设置的exchange上去，进而被路由到另一个队列。
可以监听这个队列中消息做相应的处理，这个特性可以弥补RabbitMQ3.0以前支持的immediate参数的功能。
死信队列设置：
首先要设置死信队列的exchange和queue，然后进行绑定：
Exchange：dlx.exchange
Queue：dlx.queue
RoutingKey：#
然后我们进行正常声明交换机，队列，绑定，只不过我们需要在队列加上一个参数：arguments.put("x-dead-letter-exchange","dlx.exchange");
这样消息在过期、request、队列子啊达到最大长度时， 消息就可以直接路由到死信队列。
//生产者端代码
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(5672);
connectionFactory.setVirtualHost("/");
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
String exchange = "test_dlx_exchange";
String routingKey = "dlx.save";
String msg = "Hello RabbitMQ DLX Message";
for(int i =0; i<1; i ++){
AMQP.BasicProperties properties = new AMQP.BasicProperties.Builder()
.deliveryMode(2)
.contentEncoding("UTF-8")
.expiration("10000")
.build();
channel.basicPublish(exchange, routingKey, true, properties, msg.getBytes());
}
//消费者端代码
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(5672);
connectionFactory.setVirtualHost("/");
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
// 这就是一个普通的交换机 和 队列 以及路由
String exchangeName = "test_dlx_exchange";
String routingKey = "dlx.#";
String queueName = "test_dlx_queue";
channel.exchangeDeclare(exchangeName, "topic", true, false, null);
Map<String, Object> agruments = new HashMap<String, Object>();
agruments.put("x-dead-letter-exchange", "dlx.exchange");
//这个agruments属性，要设置到声明队列上
channel.queueDeclare(queueName, true, false, false, agruments);
channel.queueBind(queueName, exchangeName, routingKey);
//要进行死信队列的声明:
channel.exchangeDeclare("dlx.exchange", "topic", true, false, null);
channel.queueDeclare("dlx.queue", true, false, false, null);
channel.queueBind("dlx.queue", "dlx.exchange", "#");
channel.basicConsume(queueName, true, new MyConsumer(channel));
//自定义消费者
public MyConsumer(Channel channel) {
super(channel);
}
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
System.err.println("-----------consume message----------");
System.err.println("consumerTag: " + consumerTag);
System.err.println("envelope: " + envelope);
System.err.println("properties: " + properties);
System.err.println("body: " + new String(body));
}
