jetstream newbie questions: How do I inspect the contents of a workqueue stream to see what all messages are pending?

[vamshiaruru]

Hi everyone, I am exploring nats to see if we can use it in our product as queue system. I created a stream with workqueue retention policy and published a bunch of messages into it. Now, I want to see the messages in the stream that are yet to be consumed. I tried this: (EVENTS is the name of stream)

nats stream view EVENTS

I get the following error:

nats: error: work queue stream contents can not be viewed

So how do I view all messages in the stream without consuming them, say for debugging reasons? Do I have to write a consumer that fetches all messages, prints them, but doesn't ack them? Is there a CLI utility for this? In general, is there a UI that helps with management of streams/KV/objects?

Similarly, if I do nack with delay of say, 10 days, is there a way to check what all messages are waiting to be delivered again like this? Or how many times a message has been nacked, or how many delivery attempts have been made for this message?

Unrelated question: I need to be able to implement deadletter queues as well, and the official documentation says to listen on $JS.EVENT.ADVISORY.CONSUMER.MAX_DELIVERIES.<STREAM>.<CONSUMER> subject. Is there a collection of such recipes for nats that help implementing common queue related stuff like this?

Thanks in advance!

[ripienaar]

The latest NATS CLI version supports viewing WQs if you enable direct get option when creating the stream.

[vamshiaruru]

thanks, I will open an issue for this.

Until a new version of nats-cli is released, the way to inspect is to fetch all messages and not ack them? Is there a way to check how many times the message has been nacked, or when it is expected to be delivered again? If I nack with delay of 10 days, will it still appear when I fetch all messages?

Any tips on the second part of my question?

I need to be able to implement deadletter queues as well, and the official documentation says to listen on $JS.EVENT.ADVISORY.CONSUMER.MAX_DELIVERIES.<STREAM>.<CONSUMER> subject. Is there a collection of such recipes for nats that help implementing common queue related stuff like this?

[ripienaar]

Data such as redelivery etc would be in the consumer. You can not see that by inspecting messages only have access to that when a delivery is done. Same for when next it will be delivered.

Only place for that kind of hints is docs, natsbyexample.com and the community slack.

[vamshiaruru]

So is there a way to get that info from the consumer then? I don't see any methods in the code that I have seen so far.

In general, how would you debug these sort of things, where you need visibility into the message lifetime (as in who all processed this, how many times was this processed, when will it be processed again etc)?

[ripienaar]

Answered above. Only available when delivered.

[vamshiaruru]

Oops, sorry, missed that.

I raised an issue in the nats-cli repo here: nats-io/natscli#920 for the first bug.

[pySilver]

@vamshiaruru did you manage to find an easy way to view messages in a queue?

[derekcollison]

Use nats cli from top of main and stream view or SCP.

[pySilver]

@derekcollison it complains about filtered consumer not unique on workqueue stream when I invoke nats stream view

[pySilver]

to be exact: nats: error: multiple non-filtered consumers not allowed on workqueue stream (10099)

[derekcollison]

You need the cli from top of main which uses direct gets vs consumers.

curl -sf https://binaries.nats.dev/nats-io/natscli/nats@main | sh

[pySilver]

oh! @derekcollison thanks! this one works!