死信佇列處理
由於您無法預期使用者會如何處置死信訊息，因此框架未提供任何標準機制來處理它們。如果死信的原因是暫時性的，您可能會希望將訊息路由回原始佇列。但是，如果問題是永久性的，則可能會導致無限迴圈。以下 Spring Boot 應用程式展示了如何將這些訊息路由回原始佇列的範例，但在嘗試三次後將它們移動到第三個「停車場」佇列。第二個範例使用 RabbitMQ Delayed Message Exchange 來為重新排隊的訊息引入延遲。在此範例中，每次嘗試延遲都會增加。這些範例使用 @RabbitListener 從 DLQ 接收訊息。您也可以在批次處理中使用 RabbitTemplate.receive()。
這些範例假設原始目的地是 so8400in，而消費者群組是 so8400。
非分割目的地
前兩個範例適用於目的地未分割的情況
@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_RETRIES_HEADER = "x-retries";
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) {
Integer retriesHeader = (Integer) failedMessage.getMessageProperties().getHeaders().get(X_RETRIES_HEADER);
if (retriesHeader == null) {
retriesHeader = Integer.valueOf(0);
}
if (retriesHeader < 3) {
failedMessage.getMessageProperties().getHeaders().put(X_RETRIES_HEADER, retriesHeader + 1);
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 X_RETRIES_HEADER = "x-retries";
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) {
Map<String, Object> headers = failedMessage.getMessageProperties().getHeaders();
Integer retriesHeader = (Integer) headers.get(X_RETRIES_HEADER);
if (retriesHeader == null) {
retriesHeader = Integer.valueOf(0);
}
if (retriesHeader < 3) {
headers.put(X_RETRIES_HEADER, retriesHeader + 1);
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);
}
}分割目的地
對於分割目的地，所有分割區只有一個 DLQ。我們從標頭中確定原始佇列。
[[republishtodlq=false]] === republishToDlq=false
當 republishToDlq 為 false 時，RabbitMQ 會將訊息發布到 DLX/DLQ，並在 x-death 標頭中包含有關原始目的地的資訊，如下列範例所示
@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";
private static final String X_RETRIES_HEADER = "x-retries";
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();
Integer retriesHeader = (Integer) headers.get(X_RETRIES_HEADER);
if (retriesHeader == null) {
retriesHeader = Integer.valueOf(0);
}
if (retriesHeader < 3) {
headers.put(X_RETRIES_HEADER, retriesHeader + 1);
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]] === republishToDlq=true
當 republishToDlq 為 true 時，重新發布恢復器會將原始交換器和路由金鑰新增至標頭，如下列範例所示
@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_RETRIES_HEADER = "x-retries";
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();
Integer retriesHeader = (Integer) headers.get(X_RETRIES_HEADER);
if (retriesHeader == null) {
retriesHeader = Integer.valueOf(0);
}
if (retriesHeader < 3) {
headers.put(X_RETRIES_HEADER, retriesHeader + 1);
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);
}
}
