How to retrieve the status of a consumer.

[qyzxcswbll]

Observed behavior

During usage, we discovered that certain topics within the consumer were not functioning properly. Although we attempted to reconnect, we were uncertain when a topic became unavailable.

Expected behavior

We hope for an interface or method that can monitor the consumer's status, ideally providing information on the status of each individual topic.

Server and client version

nats-server ：2.10.14
nats.go :1.34.1

Host environment

No response

Steps to reproduce

No response

[Jarema]

You can call Info() on a consumer instance, which is equivalent of CLI's nats consumer info. This is all the info you have for a consumer.

To check what subjects (topics) are in stream, you need to check stream subjects. Keep in mind tht Consumer is just a "view" into the stream. Consumers do not store the messages.

What you mean by topic being unavailable, or not acting properly?

[qyzxcswbll]

I had six topics previously. Due to unknown reasons, a reconnection was triggered, and I'm unsure why the disconnection occurred in the first place. After reconnecting, all topics were supposed to be subscribed to again, but only five were subscribed to. One particular topic consistently failed to consume properly. This occurrence is sporadic, but unfortunately, we are unable to perceive the subscription status of this topic.

[qyzxcswbll]

Using consumer's info() did not provide the method to check the subscription topic status that I want.

[Jarema]

When consumer is consuming messages, it does not subscribe separately to subjects.
It consumes all messages for given filter(s) leveraging only one subscription.

Maybe the messages were about to be redelivered due to reconnect?
Could you describe the behavior you see that is invalid and share consumer/stream info?

[qyzxcswbll]

Because the names of the topics are all different, and no * or > is used, there are 6 similar subscriptions in a loop. Therefore, in case of disconnection, I will reconnect. I use the CreateOrUpdateConsumer method.

The reason for considering it ineffective is that subscriptions can be received normally on other nodes, but cannot be received properly on this reconnected node.

Based on your description, I checked the info method and did not find a method to obtain the status of the topic.

[Jarema]

You do not have to do anything if client disconnects. It will automatically reconnect on it's own and resume all subscriptions and consumers. What you mean that you do reconnect? Maybe this is source of a problem.

Regarding the subscriptions:
Even if you have a consumer with multiple subjects, like this:

ConsumerConfig {
  Durable: "Consumer",
  FilterSubjects: []string{"foo.>", "bar.>", "baz.*"},
}

its still one subscription because of how JetStream consumer API works and why you will get messages in order.

Can you please share your Consumer and Stream configs, so we can better understand your config the issue you're facing?