I'm using rabbitTemplate.convertAndSend() for sending my object to queue. the problem is, I need that queue to store unique data. is there any mechanism to check whether such data is exist in a queue, before putting it to said queue?
No; there is no such mechanism.
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Context: I have an Azure storage queue that is used as the input queue for a Queue Trigger Function. So, whenever a message gets added to the queue, some function X is triggered and starts running. I want to test that the message was successfully put in the queue and consumed. How can I do that from the queue only (assuming I do not have visibility into my function X, and I can not change the settings for the Queue Trigger Function)? To further break down this question:
After the Queue Trigger Function dequeues the message, would the message still be available for me to read from it when testing? If yes, how can I access it?
Since there is a race condition here, if I dequeue the message when testing before the Queue Trigger Function gets to do it, how would that interfere with the function of the Queue Trigger? Is it possible to dequeue the message when testing, but at the same time, have it available for Queue Trigger to dequeue it and trigger my function X with no interference at all?
Bottom line, I have a queue message in Azure storage queue that I want to read twice from two different sources, with no interference between the two operations. Is this possible and supported? If yes, how can I do it?
Thanks!
I don't think the way you're trying to do this will work. You can get part of the way by using Peek Messages to read queue messages without dequeuing them, but if the Function gets to a message before you then you'll never see it in the first place.
However, you might might be able to get the information you need by using Storage Analytics Logging to track queue activity, or by using Service Bus topics instead of a queue so your messages can have multiple subscribers.
I am using RabbitMQ to send notifications to the user. The user can read his queue at any time.
The problem I am facing is that the queue is filled with lots of notifications during the night, and when the user returns in the morning, he has to process these messages sequentially. A lot of these notifications are even duplicates.
I guess it would make sense to improve this at the publisher side. That is, before adding a new notification, we investigate if there are already pending notifications in the queue. If this is the case, we only queue a new notification if it is really a new notification, hence avoiding duplicates.
We might even go further and extend this by combining notifications: instead of simply queuing a new notification, we could replace the present notifications from the queue by a new one which holds the sum of these notifications and the new one (for example in an array of inner notifications).
Is this possible with AMQP/RabbitMQ?
This rabbitmq plugin has been written to tackle your issue.
You can enable de-duplication on a queue via setting its x-message-deduplication argument to true.
Then, your publishers will need to provide the x-deduplication-header message header with a value meaningful for de-duplication. The value could be a unique message ID or the MD5/SHA1 hash of the body for example.
No, by default you can't replace an existing message.
Is there a way in EasyNetQ to set the routing key [x-dead-letter-routing-key] argument when creating a Queue? (as far as I can see you can only set a DeadLetterExchange.)
IQueue updateCacheQueue = advancedBus.QueueDeclare(name: "UpdateCache", deadLetterExchange: "UpdatesDeadLetter");
RabbitMQ assumes that exchanges are superior to queues. You can create an exchange that delivers to exactly one queue, and thus your DLQ addressing issue is solved. Should you decide you need to take additional actions in the future (e.g. store the message for potential reprocessing AND ALSO alert operations via email), you can do that in the exchange without mucking up the queue processor.
I Added another parameter to the QueueDeclare method and created a pull request, and you can set it after version 0.40.6.355
If I see some queue in rabbitmq (f.e. foobar), where is no activity, how I can find who created that queue, or, at least, which channel?
You can't find out creator except it was declared as exclusive and thus it has only one consumer.
Alternatively, you can find all channels (and thus connections) which utilize specific queue with management plugin.
If you set x-expires on a queue to auto-delete the queue if it has been unused for a period of time, is it possible to be notified of that event in any way? I would like to take some cleanup action when a queue is deleted in this fashion. Ideally, by a message being posted to some exchange/queue that I can consume.
For reference, x-expires with queues:
The x-expires argument to queue.declare controls for how long a queue can be unused before it is automatically deleted. Unused means the queue has no consumers, the queue has not been redeclared, and basic.get has not been invoked for a duration of at least the expiration period. The server guarantees that the queue will be deleted, if unused for at least the expiration period.
AFAIK, there is no built-in way to do this on the RabbitMQ-side. You would need to use the API to get a list of queues, and then compare snapshots of this list over time.
I can't think of a scenario where it would be useful to know when a queue is auto-deleted. In my view, that is already an automatic resource cleanup feature. Who would want to know about this event (client or server)? How would you expect to recover if you somehow "missed" one of these notifications? Perhaps there is a better, more deterministic way of achieving your goals.
Would you be able to provide your use-case, so possibly a more useful alternative solution can be suggested?