RabbitMQ Wait for a message with a timeout

Question

I'd like to send a message to a RabbitMQ server and then wait for a reply message (on a "reply-to" queue). Of course, I don't want to wait forever in case the application processing these messages is down - there needs to be a timeout. It sounds like a very basic task, yet I can't find a way to do this. I've now run into this problem with Java API.

Answer 1

The RabbitMQ Java client library now supports a timeout argument to its QueueConsumer.nextDelivery() method.

For instance, the RPC tutorial uses the following code:

channel.basicPublish("", requestQueueName, props, message.getBytes());

while (true) {
    QueueingConsumer.Delivery delivery = consumer.nextDelivery();
    if (delivery.getProperties().getCorrelationId().equals(corrId)) {
        response = new String(delivery.getBody());
        break;
    }
}

Now, you can use consumer.nextDelivery(1000) to wait for maximum one second. If the timeout is reached, the method returns null.

channel.basicPublish("", requestQueueName, props, message.getBytes());

while (true) {
    // Use a timeout of 1000 milliseconds
    QueueingConsumer.Delivery delivery = consumer.nextDelivery(1000);

    // Test if delivery is null, meaning the timeout was reached.
    if (delivery != null &&
        delivery.getProperties().getCorrelationId().equals(corrId)) {
        response = new String(delivery.getBody());
        break;
    }
}

Answer 2

com.rabbitmq.client.QueueingConsumer has a nextDelivery(long timeout) method, which will do what you want. However, this has been deprecated. Writing your own timeout isn't so hard, although it may be better to have an ongoing thread and a list of in-time identifiers, rather than adding and removing consumers and associated timeout threads all the time.

Edit to add: Noticed the date on this after replying!