死信队列处理
由于无法预知用户希望如何处理死信消息，框架没有提供任何标准机制来处理它们。
如果死信的原因是暂时的，您可能希望将消息路由回原始队列。
但是，如果问题是永久性的，则可能导致无限循环。
以下 Spring Boot 应用程序展示了一个示例，说明如何将这些消息路由回原始队列，但在三次尝试后将其移动到第三个“停放区”队列。
第二个示例使用 RabbitMQ 延迟消息交换器 为重新排队的消息引入延迟。
在此示例中，延迟会随着每次尝试而增加。
这些示例使用 @RabbitListener 从 DLQ 接收消息。
您也可以在批处理中使用 RabbitTemplate.receive()。
这些示例假设原始目标是 so8400in，消费者组是 so8400。
非分区目的地
前两个示例适用于目的地 未 分区的情况：
@SpringBootApplication
public class ReRouteDlqApplication {
private static final String ORIGINAL_QUEUE = "so8400in.so8400";
private static final String DLQ = ORIGINAL_QUEUE + ".dlq";
private static final String PARKING_LOT = ORIGINAL_QUEUE + ".parkingLot";
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(ReRouteDlqApplication.class, args);
System.out.println("Press enter to exit");
System.in.read();
context.close();
}
@Autowired
private RabbitTemplate rabbitTemplate;
@RabbitListener(queues = DLQ)
public void rePublish(Message failedMessage) {
long retries = failedMessage.getMessageProperties().getRetryCount();
if (retries < 3) {
failedMessage.getMessageProperties().incrementRetryCount();
this.rabbitTemplate.send(ORIGINAL_QUEUE, failedMessage);
}
else {
this.rabbitTemplate.send(PARKING_LOT, failedMessage);
}
}
@Bean
public Queue parkingLot() {
return new Queue(PARKING_LOT);
}
}@SpringBootApplication
public class ReRouteDlqApplication {
private static final String ORIGINAL_QUEUE = "so8400in.so8400";
private static final String DLQ = ORIGINAL_QUEUE + ".dlq";
private static final String PARKING_LOT = ORIGINAL_QUEUE + ".parkingLot";
private static final String DELAY_EXCHANGE = "dlqReRouter";
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(ReRouteDlqApplication.class, args);
System.out.println("Press enter to exit");
System.in.read();
context.close();
}
@Autowired
private RabbitTemplate rabbitTemplate;
@RabbitListener(queues = DLQ)
public void rePublish(Message failedMessage) {
long retries = failedMessage.getMessageProperties().getRetryCount();
if (retries < 3) {
failedMessage.getMessageProperties().incrementRetryCount();
Map<String, Object> headers = failedMessage.getMessageProperties().getHeaders();
headers.put("x-delay", 5000 * retriesHeader);
this.rabbitTemplate.send(DELAY_EXCHANGE, ORIGINAL_QUEUE, failedMessage);
}
else {
this.rabbitTemplate.send(PARKING_LOT, failedMessage);
}
}
@Bean
public DirectExchange delayExchange() {
DirectExchange exchange = new DirectExchange(DELAY_EXCHANGE);
exchange.setDelayed(true);
return exchange;
}
@Bean
public Binding bindOriginalToDelay() {
return BindingBuilder.bind(new Queue(ORIGINAL_QUEUE)).to(delayExchange()).with(ORIGINAL_QUEUE);
}
@Bean
public Queue parkingLot() {
return new Queue(PARKING_LOT);
}
}分区目的地
对于分区目的地，所有分区共享一个 DLQ。 我们从消息头中确定原始队列。
republishToDlq=false
当 republishToDlq 为 false 时，RabbitMQ 将消息发布到 DLX/DLQ，其中包含一个 x-death 消息头，该消息头包含有关原始目的地的信息，如以下示例所示：
@SpringBootApplication
public class ReRouteDlqApplication {
private static final String ORIGINAL_QUEUE = "so8400in.so8400";
private static final String DLQ = ORIGINAL_QUEUE + ".dlq";
private static final String PARKING_LOT = ORIGINAL_QUEUE + ".parkingLot";
private static final String X_DEATH_HEADER = "x-death";
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(ReRouteDlqApplication.class, args);
System.out.println("Press enter to exit");
System.in.read();
context.close();
}
@Autowired
private RabbitTemplate rabbitTemplate;
@RabbitListener(queues = DLQ)
public void rePublish(Message failedMessage) {
Map<String, Object> headers = failedMessage.getMessageProperties().getHeaders();
long retries = failedMessage.getMessageProperties().getRetryCount();
if (retries < 3) {
failedMessage.getMessageProperties().incrementRetryCount();
List<Map<String, ?>> xDeath = (List<Map<String, ?>>) headers.get(X_DEATH_HEADER);
String exchange = (String) xDeath.get(0).get("exchange");
List<String> routingKeys = (List<String>) xDeath.get(0).get("routing-keys");
this.rabbitTemplate.send(exchange, routingKeys.get(0), failedMessage);
}
else {
this.rabbitTemplate.send(PARKING_LOT, failedMessage);
}
}
@Bean
public Queue parkingLot() {
return new Queue(PARKING_LOT);
}
}republishToDlq=true
当 republishToDlq 为 true 时，重新发布恢复器将原始交换器和路由键添加到消息头中，如以下示例所示：
@SpringBootApplication
public class ReRouteDlqApplication {
private static final String ORIGINAL_QUEUE = "so8400in.so8400";
private static final String DLQ = ORIGINAL_QUEUE + ".dlq";
private static final String PARKING_LOT = ORIGINAL_QUEUE + ".parkingLot";
private static final String X_ORIGINAL_EXCHANGE_HEADER = RepublishMessageRecoverer.X_ORIGINAL_EXCHANGE;
private static final String X_ORIGINAL_ROUTING_KEY_HEADER = RepublishMessageRecoverer.X_ORIGINAL_ROUTING_KEY;
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(ReRouteDlqApplication.class, args);
System.out.println("Press enter to exit");
System.in.read();
context.close();
}
@Autowired
private RabbitTemplate rabbitTemplate;
@RabbitListener(queues = DLQ)
public void rePublish(Message failedMessage) {
Map<String, Object> headers = failedMessage.getMessageProperties().getHeaders();
long retries = failedMessage.getMessageProperties().getRetryCount();
if (retries < 3) {
failedMessage.getMessageProperties().incrementRetryCount();
String exchange = (String) headers.get(X_ORIGINAL_EXCHANGE_HEADER);
String originalRoutingKey = (String) headers.get(X_ORIGINAL_ROUTING_KEY_HEADER);
this.rabbitTemplate.send(exchange, originalRoutingKey, failedMessage);
}
else {
this.rabbitTemplate.send(PARKING_LOT, failedMessage);
}
}
@Bean
public Queue parkingLot() {
return new Queue(PARKING_LOT);
}
}