Some questions about NATS

[wf-soft]

Why are duplicate IDs associated with consumers rather than streams, even though messages are consumed and cannot be re-added?

Why doesn't Limit Stream support deleting messages while acknowledging them?

Why don't push-based consumers support attaching metadata when pushing?

Why don't Stream and Consumer traversal support query conditions or pagination?

Why must the Fetch wait expiration be greater than 1 second?

Why is there no API to check whether a Stream or Consumer exists, and you can only detect it by exceptions thrown during retrieval or creation?

Use PurgeStreamAsynchronous to clear messages that are not locked by consumers

[neilalexander]

Why are duplicate IDs associated with consumers rather than streams, even though messages are consumed and cannot be re-added?

Not sure I understand the question?

[neilalexander]

Why doesn't Limit Stream support deleting messages while acknowledging them?

If you want this behaviour, then you want an Interest-based stream, not Limits. Note that you can still set limits like max age, max msgs etc on an Interest-based stream.

[neilalexander]

Why don't Stream and Consumer traversal support query conditions or pagination?

Consumers deliver messages based on the consumer configuration. You can query a stream directly using the message get APIs, through which you can effectively paginate by combining the sequence with the batch size. https://pkg.go.dev/github.com/nats-io/[email protected]/api#JSApiMsgGetRequest

[neilalexander]

Why is there no API to check whether a Stream or Consumer exists, and you can only detect it by exceptions thrown during retrieval or creation?

You can call stream info or consumer info to check whether an asset exists or not. (You may not want to call it too often though, since there is a serverside cost to these calls.)

[wf-soft]

@neilalexander If push-based consumers could deliver more information to subscribers, it would be beneficial. Currently, I need to use Limit Stream to acknowledge and consume messages. After retrieving and processing messages, I pass the message sequence numbers (Seq) and processing results to the final queue for batch database insertion and counting operations, followed by deletion from Limit Stream. However, it appears that when using push consumers, subscribers can only obtain the ReplyTo identifier, which cannot be used to delete messages. Ideally, if the consumer's metadata could also be pushed to subscribers, this would further enhance functionality.

[wf-soft]

@ripienaar This seems to only exist when pulling consumers, and when using push consumers, the metadata received by subscribers is null

[ripienaar]

All consumers support the metadata. It’s best you ask the specific language users how it works - I have not used .net but I do know nats server sends the metadata on push consumer delivery.

[wf-soft]

@ripienaar Okay, thank you.

[ripienaar]

Then you are probably not making a push consumer at all but subscribing to the stream ingest subject.

Again, ask for help with the .net users please.

[wf-soft]

@ripienaar My description might not be entirely accurate. I configured a persistent consumer with DeliverGroup and DeliverSubject, then subscribed to messages via SubscribeAsync.

[wf-soft]

@ripienaar I found that subscribing to messages in Nats.NET returns NatsMsg, while consumers pull back NatsJSMsg, and there is no Metadata attribute in NatsMsg

[jnmoyne]

Why must the Fetch wait expiration be greater than 1 second?

It doesn't, you can certainly specify less than 1s fetch max wait times (if you can't it's an issue with the client library you are using not the server)