How to find number of subscriptions on jetstream

[YashasAnand]

I am using jetsream but instead of consuming messages I am subscribing to subjects with queue groups attached.

If i do nats consumer list i do not get list of consumers. If so how do i get number of subscribers?

I have tried to look in management console on 8222 port, but i do not get details like if its my own subscriptios or some server subscriptions as the numbers are not matching.

[Jarema]

In JetStream, you cannot subscribe to Stream Subjects without a Consumer, so you definately should see consumers in consumer list.

In CLI, you can use nats stream report and nats consumer report to get good info on JetStream.
In monitoring APIs, you can add flags to list more details, especially streams and consumers.

[YashasAnand]

Thank you for your reply @Jarema , pls see the attached screenshots of nats consumer report & nats stream report

I am using below snippet of code to do these operations. Is this a bug?

Pls refer to code below:

NatsOpts natsOptions = new NatsOpts
{
    Url = connectionInfo.BrokerUrl, 
    Name = connectionInfo.ClientName,
};

_natsConnection = new NatsConnection(natsOptions);

_natsJSContext = new NatsJSContext(_natsClient);

await foreach (var msg in _natsClient.SubscribeAsync(natsConsumerOptions.TopicName,natsConsumerOptions.ConsumerGroup,serializer:natsMesgSerializer))
{
    _logger.Log($"Received message on Subscriber {natsConsumerOptions.TopicName} in group {natsConsumerOptions.ConsumerGroup}: {msg.Data}");
    _ = Task.Run(async () => await ProcessMessageAsyncNew(natsConsumerOptions,consumerOptions,onMessageReceived,msg));
}

[Jarema]

I see you're craeting _natsJSContext, but you are not actually using it. I guess it's a bug in your code, but I'm not C# engineer.
@mtmk can help here for sure.

You can also use Pull Consumers, like here, to achieve the same goal:

[YashasAnand]

Ah I see, @Jarema thank you for pointing this out, but then how are the messages still persisiting to stream if i am not using jetstream context?

[Jarema]

you can publish messages to the stream with just Core NATS, but you will not get ACK, not a backpressure control (so it's not a good idea).
JetStream Publish sends a request instead, that will expect ack back.

[YashasAnand]

@Jarema thank you so much for your help. Much Aprreciated !!

[YashasAnand]

"You have 1 consumer with 6 clients binding to it. " . How does this work exactly? & which is preferred, to have 6 consumers or 1 consumers with 6 bindings for higher consumption rate?

[Jarema]

Please read the provided docs link and my previous responses.

If you bind 6 clients to 1 consumer, server will round-robin messages across them.
Having 6 consumers would result in different outcome - sending every messages to each, instead of round robin.

[YashasAnand]

@Jarema thank you for the response, what im asking is if i have 6 consumers with different names & different subject filters such that i make sure for a subject (orders.burgers becomes orders.burgers.1 with consumer 1 listening only to orders.burgers.1) one message goes only to one consumer using different subject filters, Will i get a better performance in this or will i get a better performance in round-robin binding consumer.

[Jarema]

That depends a lot on subject cardinality, replication factor, etc.
The best approach is to bench your specific scenario. NATS CLI has great tooling capabilities with nats bench.

[YashasAnand]

Thank you very much for your valuable inputs & time @Jarema