Messages lost if queue does not exist - rabbitmq

Question

When we send the messages to RabbitMQ and if queue doesn't exist, messages are lost without throwing any error.
Where the messages will be posted to? Dead queue?

Answer 1

That is the way RabbitMQ is designed - publishers publish to exchanges, not queues.
If there is no queue bound (with a matching routing key if the exchange requires one), the message is simply discarded.
You can enable publisher returns and set the mandatory flag when publishing and the broker will return the message (but it arrives on a different thread, not the publishing thread).

Answer 2

Your messages can be returned back to you
If there are no queues bound to an exchange. To receive them back and not to lose these messages, you must do the following:
1. Add these properties to your application.yml
spring:
rabbitmq:
publisher-confirm-type: correlated
publisher-returns: true
template:
mandatory: true
2. Create RabbitConfirmCallback
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.stereotype.Component;
#Component
public class RabbitConfirmCallback implements RabbitTemplate.ConfirmCallback {
private static final Logger logger = LoggerFactory.getLogger(RabbitConfirmCallback.class);
#Override
public void confirm(CorrelationData correlationData, boolean ack, String cause) {
if (ack && correlationData != null && correlationData.getId() != null) {
Message returnedMessage = correlationData.getReturnedMessage();
String dataId = correlationData.getId();
if (returnedMessage != null) {
logger.error("Message wasn't delivered to Consumer; " + returnedMessage + "\nCorrelationData id = " + dataId);
} else {
logger.info("CorrelationData with id " + dataId + " acknowledged;");
}
} else {
if (ack) {
logger.warn("Unknown message acknowledgement received: " + correlationData);
} else {
logger.info("Broker didn't accept message: " + cause);
}
}
}
}
This callback method confirm(...) will be triggered, right after trial of sending message in such an exchange without bounded queues.
In correlationData object, you will find returnedMessage field where will be messageProperties and body of your message
3. Set RabbitConfirmCallback to RabbitTemplate
#Autowired
public void post(RabbitTemplate rabbitTemplate, RabbitConfirmCallback rabbitConfirmCallback){
rabbitTemplate.setConfirmCallback(rabbitConfirmCallback);
}
4. When you are sending your messages, add CorrelationDate object
With some unique identifier
rabbitTemplate.convertAndSend(exchange, routingKey, wrapMessage(message),
new CorrelationData(stringId));