一、app开发定制公司死信的概念
死信,app开发定制公司顾名思义就是无法被消费的消息。一般来说,Producer app开发定制公司将消息投递到 Broker app开发定制公司或者直接到 Queue 里了,Consumer 从 Queue app开发定制公司取出消息进行消费,app开发定制公司但某些时候由于特定的原因导致 Queue app开发定制公司中的某些消息无法被消费,这样的消息如果没有后续的处理,就变成了死信,有死信自然就有了死信。
应用场景:为了保证订单业务的消息数据不丢失,需要使用到 的死信队列机制,档消息消费发生异常时,将消息投入到死信队列中。还有比如说:用户在商城下单成功并点击支付后再指定时间未支付时自动失效。
二、死信的来源
- 消息 TTL 过期
- 队列达到最大长度(队列满了,无法再添加数据到 mq 中)
- 消息被拒绝(basic.reject 或 basic.nack)并且 requeue=false(不再重新入队)
三、死信实战
3.1 代码架构图
3.2 消息 TTL 过期
生产者
public class DeadLetterProducer { private static String EXCHANGE_NAME = "normal_exchange"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); // 声明一个交换机 channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 设置消息 TTL 过期时间 AMQP.BasicProperties properties = new AMQP.BasicProperties().builder().expiration("10000").build(); String message = "info"; channel.basicPublish(EXCHANGE_NAME, "zhangsan", properties, message.getBytes()); System.out.println("消息发送完成:" + message); }}
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消费者1
public class DeadLetterConsumer1 { private static String NORMAL_EXCHANGE_NAME = "normal_exchange"; private static String NORMAL_QUEUE_NAME = "normal-queue"; private static String DEAD_EXCHANGE_NAME = "dead_exchange"; private static String DEAD_QUEUE_NAME = "dead-queue"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); // 声明一个死信队列 channel.queueDeclare(DEAD_QUEUE_NAME, false, false, false, null); // 声明一个死信交换机 channel.exchangeDeclare(DEAD_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 死信队列与死信交换机绑定 channel.queueBind(DEAD_QUEUE_NAME, DEAD_EXCHANGE_NAME, "lisi"); // 正常队列与死信交换机的绑定关系 Map<String, Object> deadLetterParams = new HashMap<>(2); deadLetterParams.put("x-dead-letter-exchange", DEAD_EXCHANGE_NAME); deadLetterParams.put("x-dead-letter-routing-key","lisi"); // 声明一个正常队列 channel.queueDeclare(NORMAL_QUEUE_NAME, false, false, false, deadLetterParams); // 声明一个正常交换机 channel.exchangeDeclare(NORMAL_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 把队列和交换机进行绑定 channel.queueBind(NORMAL_QUEUE_NAME, NORMAL_EXCHANGE_NAME, "zhangsan"); System.out.println("C1消费者启动等待消费消息:"); channel.basicConsume(NORMAL_QUEUE_NAME, true, (consumerTag, delivery) -> { String receivedMessage = new String(delivery.getBody()); System.out.println("消费者接收到消息:" + receivedMessage); },(consumerTag) -> { System.out.println(consumerTag + "消费者取消消费消息"); }); }}
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消费者2
public class DeadLetterConsumer2 { private static String NORMAL_EXCHANGE_NAME = "normal_exchange"; private static String DEAD_QUEUE_NAME = "dead-queue"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); channel.exchangeDeclare(NORMAL_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); System.out.println("C2消费者启动等待消费消息:"); channel.basicConsume(DEAD_QUEUE_NAME, true, (consumerTag, delivery) -> { String receivedMessage = new String(delivery.getBody()); System.out.println("消费者接收到死信:" + receivedMessage); },(consumerTag) -> { System.out.println(consumerTag + "消费者取消消费消息"); }); }}
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先启动消费者1,将正常交换机、死信交换机、正常队列、死信队列创建出来,否则会报错。接着启动消费者2,然后在启动生产者,观察控制台。
消费者1启动后进入RabbitMQ系统后台,可以看到队列 normal-queue 的 features 一列多了两个信息。其中 DLX 表示死信交换机,DLK 表示死信交换机的路由键(RoutingKey)。
此时由于消费者1可以正常消费消息,所以在消费者2中,死信队列是接收不到消息的。控制台情况如下:
将消费者1和消费者2的服务停止,重新运行生产者,10s 后消息会被进入到死信队列
再来看下后台系统:
生产者未发送消息
生产者发送了 1 条消息,此时正常队列中有 1 条未消费消息
时间过去 10 秒,正常队列里面的消息由于没有被消费,消息进入死信队列。
3.3 队列达到最大长度
生产者
public class DeadLetterLengthProducer { private static String EXCHANGE_NAME = "normal_exchange"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); // 声明一个交换机 channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 设置消息 TTL 过期时间 for (int i = 0; i < 10; i++) { String message = "info" + i; channel.basicPublish(EXCHANGE_NAME, "zhangsan", null, message.getBytes()); } System.out.println("消息发送完成"); }}
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消费者1
public class DeadLetterLengthConsumer1 { private static String NORMAL_EXCHANGE_NAME = "normal_exchange"; private static String NORMAL_QUEUE_NAME = "normal-queue"; private static String DEAD_EXCHANGE_NAME = "dead_exchange"; private static String DEAD_QUEUE_NAME = "dead-queue"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); // 声明一个死信队列 channel.queueDeclare(DEAD_QUEUE_NAME, false, false, false, null); // 声明一个死信交换机 channel.exchangeDeclare(DEAD_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 死信队列与死信交换机绑定 channel.queueBind(DEAD_QUEUE_NAME, DEAD_EXCHANGE_NAME, "lisi"); // 正常队列与死信交换机的绑定关系 Map<String, Object> deadLetterParams = new HashMap<>(2); deadLetterParams.put("x-dead-letter-exchange", DEAD_EXCHANGE_NAME); deadLetterParams.put("x-dead-letter-routing-key","lisi"); deadLetterParams.put("x-max-length", 6); // 声明一个正常队列 channel.queueDeclare(NORMAL_QUEUE_NAME, false, false, false, deadLetterParams); // 声明一个正常交换机 channel.exchangeDeclare(NORMAL_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 把队列和交换机进行绑定 channel.queueBind(NORMAL_QUEUE_NAME, NORMAL_EXCHANGE_NAME, "zhangsan"); System.out.println("C1消费者启动等待消费消息:"); channel.basicConsume(NORMAL_QUEUE_NAME, true, (consumerTag, delivery) -> { String receivedMessage = new String(delivery.getBody()); System.out.println("消费者接收到消息:" + receivedMessage); },(consumerTag) -> { System.out.println(consumerTag + "消费者取消消费消息"); }); }}
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消费者2
public class DeadLetterLengthConsumer2 { private static String NORMAL_EXCHANGE_NAME = "normal_exchange"; private static String DEAD_QUEUE_NAME = "dead-queue"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); channel.exchangeDeclare(NORMAL_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); System.out.println("C2消费者启动等待消费消息:"); channel.basicConsume(DEAD_QUEUE_NAME, true, (consumerTag, delivery) -> { String receivedMessage = new String(delivery.getBody()); System.out.println("消费者接收到死信:" + receivedMessage); },(consumerTag) -> { System.out.println(consumerTag + "消费者取消消费消息"); }); }}
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由于消费者1中修改了队列参数,所以启动前需要先将原先的队列删除,然后再启动消费者1,创建相关的队列及交换机。接着关闭消费者 1,启动生产者。打开后台系统:
普通队列中有 6 条消息未消费,超出队列长度的 4 条消息进入到了死信队列。
然后启动消费者1 和消费者2
3.4 消息被拒
生产者和消费者2 的代码不需要修改,修改消费者1 的代码,修改后的代码如下:
消费者2
public class DeadLetterRejectConsumer1 { private static String NORMAL_EXCHANGE_NAME = "normal_exchange"; private static String NORMAL_QUEUE_NAME = "normal-queue"; private static String DEAD_EXCHANGE_NAME = "dead_exchange"; private static String DEAD_QUEUE_NAME = "dead-queue"; public static void main(String[] args) throws IOException, TimeoutException { Channel channel = RabbitMqUtil.getChannel(); // 声明一个死信队列 channel.queueDeclare(DEAD_QUEUE_NAME, false, false, false, null); // 声明一个死信交换机 channel.exchangeDeclare(DEAD_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 死信队列与死信交换机绑定 channel.queueBind(DEAD_QUEUE_NAME, DEAD_EXCHANGE_NAME, "lisi"); // 正常队列与死信交换机的绑定关系 Map<String, Object> deadLetterParams = new HashMap<>(2); deadLetterParams.put("x-dead-letter-exchange", DEAD_EXCHANGE_NAME); deadLetterParams.put("x-dead-letter-routing-key","lisi"); // 声明一个正常队列 channel.queueDeclare(NORMAL_QUEUE_NAME, false, false, false, deadLetterParams); // 声明一个正常交换机 channel.exchangeDeclare(NORMAL_EXCHANGE_NAME, BuiltinExchangeType.DIRECT); // 把队列和交换机进行绑定 channel.queueBind(NORMAL_QUEUE_NAME, NORMAL_EXCHANGE_NAME, "zhangsan"); System.out.println("C1消费者启动等待消费消息:"); channel.basicConsume(NORMAL_QUEUE_NAME, false, (consumerTag, delivery) -> { String receivedMessage = new String(delivery.getBody()); if ("info5".equals(receivedMessage)) { System.out.println("C1接收到消息:" + receivedMessage+"并且拒绝签收了"); // 禁止重新入队 channel.basicReject(delivery.getEnvelope().getDeliveryTag(), false); } else { System.out.println("消费者接收到消息:" + receivedMessage); channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false); } },(consumerTag) -> { System.out.println(consumerTag + "消费者取消消费消息"); }); }}
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将原先的队列删除,重新启动消费者2,接着启动生产者
最后启动消费者2