I would like to test my Rabbitmq implementation. I have a queue and consumer, and I would like to have a third element which listens/sniffs the queue response, so the test will fail in case of queue responds nack or pass in case of it is ack.
Do you know how I could do it?
Many thanks
You should try out the tracing plugin. Note that this plugin should never be used in production due to the performance overhead it incurs.
NOTE: the RabbitMQ team monitors the rabbitmq-users mailing list and only sometimes answers questions on StackOverflow.
Related
I need a queue with limited message inside considering not only message in queue but also the unacked ones. Is there a way to configure this server side? If yes is it possible using kobu as library?
Thank you
The RabbitMQ team monitors the rabbitmq-users mailing list and only sometimes answers questions on StackOverflow.
The documentation clearly states that queue length uses the count of ready messages: https://www.rabbitmq.com/maxlength.html
How do RabbitMQ taks perform one after another Not all the same time,
e.g.
We have 10 task that follow each other.
Task 1 end do task 2 etc..
The RabbitMQ team monitors the rabbitmq-users mailing list and only sometimes answers questions on StackOverflow.
Set your channel's prefetch (QoS) value to 1. Then, when you consume messages, RabbitMQ will only send one message and will not send more until that one message is acknowledged.
I suggest that you do all of the RabbitMQ tutorials, especially this one.
I need to use rabbitmq for a client requirement. Client suggested rabbit mq.
Based on some googling it looks like rabbitmq does not support replay of past messages from arbitary offsets unlike say kafka.
I just need a confirmation on whether this limitation is still valid. Any official url will be helpful.
Thanks.
R
The RabbitMQ team monitors the rabbitmq-users mailing list and only sometimes answers questions on StackOverflow.
Based on some googling it looks like rabbitmq does not support replay
of past messages
That's correct. Once a message is delivered and acknowledged (if the queue requires an ack) it is never available again and no trace of it remains in RabbitMQ.
I'm going through a few examples using NServiceBus and I've stumbled across a feature I'm hoping ships with MassTransit (As it is a free service).
The feature is based around 'poisoned' messages.
If, due to a bug in your system, these messages cant ever be handled, and end up permanently in the error queue.
NServiceBus has a cool feature whereby, once you have corrected the bugs in your code, allows those messages in the error queue to be 'redirected' to the original working queue, to be redelivered.
This is done by using a NServiceBus specific tool :- ReturnToSourceQueue.exe.
Does MassTransit have a similar tool for this kind of issue?
Or is there another workaround availble, preferbly to work with RabbitMQ.
With RabbitMQ, it's easy to move messages between queues. You can use the management console to do it manually, by installing the shovel plug-in.
You can also create shovels in RabbitMQ that are scheduled, and perform the message movement in response to that schedule. The visibility of having the shovels configured in RabbitMQ has been invaluable to our operations staff, since they rarely think that a Windows Scheduled Task (or other random scheduler) is going to be doing something as risky as moving previously failed messages back into the production queues.
I would suggest reading this blog post on how MassTransit deals with poison messages: Error Handling in MassTransit with RabbitMQ
The tooling around RabbitMQ is so much better than anything MSMQ provides, which is one of the reasons we have completely abandoned MSMQ for production queuing.
This functionality is easily recreated with nothing more than RabbitMQ and a bit of code. While it's nice that NServicebus includes it, building it with MassTransit should be easy enough.
(note: i haven't used .NET in a few years, so my knowledge of NSB and MT are a bit rusty... this will be high level answer only, no code)
The thing to start with, is a proper configuration of a dead letter exchange and a poison message queue. https://www.rabbitmq.com/dlx.html
Once you have knowledge that a message is causing errors and is a bad message, you can reject or nack (with no requeue) the message in order to send it through the dead letter exchange (DLX).
Once a message has gone through the DLX, you will have some additional properties on the message, including:
queue - the name of the queue the message was in before it was dead-lettered,
exchange - the exchange the message was published to (note that this will be a dead letter exchange if the message is dead lettered multiple times),
routing-keys - the routing keys (including CC keys but excluding BCC ones) the message was published with,
there will be more, but these are the things you want to pay attention to. by examining these properties on the message, you can re-send the original message back through the original exchange, with the original routing-keys. alternatively, you can re-send straight to the original destination queue... i think sending through the exchange would be better, personally, as the original queue might not exist anymore (depending on system configuration, consumers creating exclusive queues, etc).
with this information, recreating the feature set should not be too difficult. rabbitmq provides all of the features that you need, you just have to write a bit of code to take advantage of it.
I have two questions about RabbitMQ Work Queues:
As I understand it from the RabbitMQ tutorials, it seems that if I have a basic queue consumer client (just a basic "Hello, World!" consumer) and then I add a second consumer client for the same queue, then RabbitMQ will automatically dispatch the messages between those two queues in a round robin manner. Is that true (without adding in any extra configuration)?
My consumer clients are configured to only ever receive one message at a time, using (GetResponse response = channel.basicGet("my_queue", false). Since I am only ever receiving one message at a time, is it still necessary to set a prefetchCount (channel.basicQos(1)) for fair dispatch?
Answers to your questions:
Yes
No
However, your two questions 1 and 2 are not compatible. If you are using a consumer, it is designed to have messages pushed to it, and you don't use Basic.Get. When you use a consumer, you will need to use Basic.QoS to specify that the consumer can only "own" one unacknowledged message at a time. RabbitMQ will not push additional messages beyond the QoS limit.
Your alternative is to "pull" from the queue using Basic.Get, and you will control your own destiny as far as how many messages you run at a time.
Does this make sense?