问题
Its like "Houston we have a problem here" where I need to schedule/delay a message for 5 minutes after it fails on the first attempt to process an event. I have implemented dead letter exchange in this scenario.
The messages on failing, route to the DLX --> Retry Queue and comes back to work queue after a TTL of 5 minutes for another attempt.
Here is the configuration I am using:
public class RabbitMQConfig {
@Bean(name = "work")
@Primary
Queue workQueue() {
return new Queue(WORK_QUEUE, true, false, false, null);
}
@Bean(name = "workExchange")
@Primary
TopicExchange workExchange() {
return new TopicExchange(WORK_EXCHANGE, true, false);
}
@Bean
Binding workBinding(Queue queue, TopicExchange exchange) {
return BindingBuilder.bind(workQueue()).to(workExchange()).with("#");
}
@Bean(name = "retryExchange")
FanoutExchange retryExchange() {
return new FanoutExchange(RETRY_EXCHANGE, true, false);
}
@Bean(name = "retry")
Queue retryQueue() {
Map<String, Object> args = new HashMap<String, Object>();
args.put("x-dead-letter-exchange", WORK_EXCHANGE);
args.put("x-message-ttl", RETRY_DELAY); //delay of 5 min
return new Queue(RETRY_QUEUE, true, false, false, args);
}
@Bean
Binding retryBinding(Queue queue,FanoutExchange exchange) {
return BindingBuilder.bind(retryQueue()).to(retryExchange());
}
@Bean
public SimpleRabbitListenerContainerFactory rabbitListenerContainerFactory(ConnectionFactory connectionFactory) {
SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
factory.setConnectionFactory(connectionFactory);
return factory;
}
@Bean
Consumer receiver() {
return new Consumer();
}
@Bean
MessageListenerAdapter listenerAdapter(Consumer receiver) {
return new MessageListenerAdapter(receiver, "receiveMessage");
}
}
Producer.java:
@GetMapping(path = "/hello")
public String sayHello() {
// Producer operation
String messages[];
messages = new String[] {" hello "};
for (int i = 0; i < 5; i++) {
String message = util.getMessage(messages)+i;
rabbitTemplate.convertAndSend("WorkExchange","", message);
System.out.println(" Sent '" + message + "'");
}
return "hello";
}
Consumer.java:
public class Consumer {
@RabbitListener(queues = "WorkQueue")
public void receiveMessage(String message, Channel channel,
@Header(AmqpHeaders.DELIVERY_TAG) Long tag) throws IOException, InterruptedException {
try {
System.out.println("message to be processed: " + message);
doWorkTwo(message);
channel.basicAck(tag, false);
} catch (Exception e) {
System.out.println("In the exception catch block");
System.out.println("message in dead letter exchange: " + message);
channel.basicPublish("RetryExchange", "", null, message.getBytes());
}
}
private void doWorkTwo(String task) throws InterruptedException {
int c = 0;
int b = 5;
int d = b / c;
}
}
Is it the correct way to use a dead letter exchange for my scenario and after waiting once in the RETRY QUEUE for 5 min, on the second time attempt it does not wait for 5 min in the RETRY QUEUE (I have mentioned TTL as 5 min) and moves to the WORK QUEUE immediately.
I am running this application by hitting localhost:8080/hello url.
Here is my updated configuration.
RabbitMQConfig.java:
@EnableRabbit
public class RabbitMQConfig {
final static String WORK_QUEUE = "WorkQueue";
final static String RETRY_QUEUE = "RetryQueue";
final static String WORK_EXCHANGE = "WorkExchange"; // Dead Letter Exchange
final static String RETRY_EXCHANGE = "RetryExchange";
final static int RETRY_DELAY = 60000; // in ms (1 min)
@Bean(name = "work")
@Primary
Queue workQueue() {
Map<String, Object> args = new HashMap<String, Object>();
args.put("x-dead-letter-exchange", RETRY_EXCHANGE);
return new Queue(WORK_QUEUE, true, false, false, args);
}
@Bean(name = "workExchange")
@Primary
DirectExchange workExchange() {
return new DirectExchange(WORK_EXCHANGE, true, false);
}
@Bean
Binding workBinding(Queue queue, DirectExchange exchange) {
return BindingBuilder.bind(workQueue()).to(workExchange()).with("");
}
@Bean(name = "retryExchange")
DirectExchange retryExchange() {
return new DirectExchange(RETRY_EXCHANGE, true, false);
}
// Messages will drop off RetryQueue into WorkExchange for re-processing
// All messages in queue will expire at same rate
@Bean(name = "retry")
Queue retryQueue() {
Map<String, Object> args = new HashMap<String, Object>();
//args.put("x-dead-letter-exchange", WORK_EXCHANGE);
//args.put("x-message-ttl", RETRY_DELAY);
return new Queue(RETRY_QUEUE, true, false, false, null);
}
@Bean
Binding retryBinding(Queue queue, DirectExchange exchange) {
return BindingBuilder.bind(retryQueue()).to(retryExchange()).with("");
}
@Bean
public SimpleRabbitListenerContainerFactory rabbitListenerContainerFactory(ConnectionFactory connectionFactory) {
SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
factory.setConnectionFactory(connectionFactory);
factory.setDefaultRequeueRejected(false);
/*factory.setAdviceChain(new Advice[] {
org.springframework.amqp.rabbit.config.RetryInterceptorBuilder
.stateless()
.maxAttempts(2).recoverer(new RejectAndDontRequeueRecoverer())
.backOffOptions(1000, 2, 5000)
.build()
});*/
return factory;
}
@Bean
Consumer receiver() {
return new Consumer();
}
@Bean
MessageListenerAdapter listenerAdapter(Consumer receiver) {
return new MessageListenerAdapter(receiver, "receiveMessage");
}
}
Consumer.java:
public class Consumer {
@RabbitListener(queues = "WorkQueue")
public void receiveMessage(String message, Channel channel,
@Header(AmqpHeaders.DELIVERY_TAG) Long tag,
@Header(required = false, name = "x-death") HashMap<String, String> xDeath)
throws IOException, InterruptedException {
doWorkTwo(message);
channel.basicAck(tag, false);
}
private void doWorkTwo(String task) {
int c = 0;
int b = 5;
if (c < b) {
throw new AmqpRejectAndDontRequeueException(task);
}
}
}
回答1:
If you reject the message so the broker routes it to a DLQ, you can examine the x-death header. In this scenario, I have a DLQ with a TTL of 5 seconds and the consumer of the message from the main queue rejects it; the broker routes it to the DLQ, then it expires and is routed back to the main queue - the x-death header shows the number of re-routing operations:
来源：https://stackoverflow.com/questions/41258684/spring-amqp-message-re-queuing-using-dead-letter-mechanism-with-ttl