Is there anyway to look at the next message in RabbitMq without actually dequeuing the message. From what I understand that only thing you can do is dequeue the message without acknowledging and letting the message TTL expire and then it will be made active again (keeping its original priority) in the queue.
No, there is no.
You can dequeue the message and nack it with the option requeue=true
as:
channel.basicNack(envelope.getDeliveryTag(), false, true);
or you can use the basicGet function
Related
If a Rabbit MQ consumer receives a message from a queue that has manual acknowledgement but the message gets lost somehow (never gets acked or nacked), is there a way to set a time before the message gets automatically requeued?
This is done immediately, also that's the only thing that makes sense.
The messages remain in the queue until they are ACKed, or until message TTL expires.
First of all i declare exchange,queue and bind them togerther. i basicPublish a message to this queue, so there are one message you in the queue. At this time i start my consumer program(with autoAck = true) and debug it, when i run to basicConsume(xxx), the message was lost! In my opinion consumer will send basic.ack to broker when it run to the method nextDelivery(), but in fact when i will declare a consumer, the message in queue is taken. why? Can someone tell me when rabbitmq delete message from queue? after the method basicConsume() or nextDelivery()??? thx~~~
autoAck = true
because of this
you are telling RabbitMQ to automatically acknowledge the message when it is consumed. acknowledging a message tells RabbitMQ that it has been taken care of and RabbitMQ can delete it now.
set autoAck to false if you want to manually acknowledge the message after you are done processing it.
I am throwing an AmqpException inside of my consumer.
My expectation is that the message will return back to the queue in FIFO order and will be reprocessed sometime in the future.
It seems as if Spring AMQP does not release the message back to the queue. But instead tries to reprocess the failed messages over and over again.
This blocks the newly arrived messages from being processed. The ones that are stuck appear in the "unpacked" state forever inside of the AMQP console.
Any thoughts?
That's the way rabbitmq/Spring AMQP works; if a message is rejected (any exception is thrown) the message is requeued by default and is put back at the head of the queue so it is retried immediately.
... reprocessed sometime in the future.
You have to configure things appropriately to make that happen.
First, you have to tell the broker to NOT requeue the message. That is done by setting defaultRequeueRejected on the listener container to false (it's true by default). Or, you can throw an AmqpRejectAndDontRequeueException which instructs the container to reject (and not requeue) an individual message.
But that's not the end of it; just doing that will simply cause the rejected message to be discarded.
To avoid that, you have to set up a Dead Letter Exchange/Queue for the queue - rejected messages are then sent to the DLX/DLQ instead of being discarded. Using a policy rather than queue arguments is generally recommended.
Finally, you can set a message time to live on the the DLQ so, after that time, the message is removed from the queue. If you set up an another appropriate dead letter exchange on that queue (the DLQ), you can cause the message to be requeued back to the original queue after the time expires.
Note that this will only work for rejected deliveries from the original queue; it will not work when expiring messages in that queue.
See this answer and some of the links from its question for more details.
You can use the contents of the x-death header to decide if you should give up completely after some number of attempts (catch the exception and somehow dispose of the bad message; don't thrown an exception and the container will ack the message).
Here is a solution I used to solve this. I setup an Interceptor to retry the message x number of times while applying a backoff policy.
http://trippstech.blogspot.com/2016/03/rabbitmq-deadletter-queue-with.html
I have thousands of unacked messages in my dev environment which I can't restart.
Is there a way to remove (purge) all messages even if they are unacknowledged?
Close the channel that the unacked messages reside on, which will nack them back into the queue, then call purge.
You have to make consumer ack them (or nack) and only after that they will be removed. Alternatively you can shutdown consumers and purge the queue completely.
If you are looking for some way to purge all unacked messages - there are no such feature nor in AMQP protocol neither in RabbitMQ.
It looks like your consumer is the cause of the problem, so you have to adjust it (rewrite) to release message immediately after it processed or failed.
Once there are no "ready" messages in the queue, delete it and recreate.
YOU WILL LOSE THE QUEUE CONTENTS with this method.
You need to put messages back into the queue before you can purge them:
close the channel
close the connection (the script doesn't work for me)
As an alternative, this doesn't require to wait:
delete and recreate the queue
restart the server
You need to call basic.recover to force all unacked messages to be re-enqueued to a channel that failed. Be aware of the errata concerning this function specifying that only the requeue mode is supported by RabbitMQ.
For software developer use below code.
channel.purgeQueue(queue-name);
if we use this code the Queue will be clear and same queue will exist.
One way this can happen is if the consumer is stuck recycling the same messages due to a processing error. In this case, the RabbitMQ queue management interface may show the messages as Unacked, but really they are being read from the queue and processed (to the point of the failure) then requeued (to enable a retry) at a rapid pace -- maybe thousands of times per second.
During this loop, the messages exist briefly in the Ready state, but are immediately removed again by you application -- and the cycle begins again. As an example, this auto-requeue behavior is the default for Spring AMQP.
Since the messages are never left in the Ready state, the Management Interface's Get Message(s) button is unlikely work. What can work, if you have queue access, is to run a separate custom consumer instance, perhaps locally, but with the specific intent of removing and not requeuing the messages in question.
By RabbitMQ's Fair Dispatch mechanism, your additional consumer will likely receive the messages in question and have the opportunity to perform your custom handling.
You might even write a custom utility to do this, with logic to filter, analyze, or deadletter the messages of interest.
If you want to clear the contents of the queue, then you can use the AMQP method queue.purge: There is queue purge in AMQP: http://www.rabbitmq.com/amqp-0-9-1-reference.html#queue.purge
You could do similar using the management plugin.
I am using RabbitMq really amazing message broker, but what i need is to have long message back up time in the queue. So that if a message is not reached to certain consumers who were inactive at that time and they are active after few mins eventually the message should be delivered to the respective consumer through fanout exchange.
What i tried is i had increased TTL in queue. Whether it is the correct way or some other tricks can be done?
Thanks in advance
You could try to use a queue with x-message-ttl, and x-dead-letter-exchange
args.put("x-message-ttl", 10000);
args.put("x-dead-letter-exchange",exchange_dead_letter);
channel.queueDeclare(queue, false, false, false, args);
x-dead-letter-exchange is an exchange and if the message is expired by the TTL time, the message is redirect to the x-dead-letter-exchange.
Then you can handle the message as you prefer.
You can find more detail here: http://www.rabbitmq.com/dlx.html.