CODEWITHSUNDEEP
nats.io
Jono
Jono

Reputation: 91

NATS.IO NATSNoRespondersException

I'm new to NATS and I have taken over an almost finshed application in NetCore 5.0. When I'm startning the application a Connection is set to an docker NATS server and this properties are set in appsettings.

"NatsSettings": {
  "Url": "nats://localhost:4222",
  "StreamName": "nats-server",
  "Timeout": 10000,
  "Verbose": true,
  "StreamReceivedSubject": "TestData.received.Subject",
  "ReceivedConsumerName": "TestData.Received.Consumer.Name",
  "ConsumerReceivedSubject": "TestData.Consumer.Received.Subject",
  "ConsumerReceivedFilter": "TestData.Received.Filter",
  "Subjects": [
    "TestData.*"
  ]
}

What am I missing in the settings for the connection? The error message I keep on getting is NATS.Client.NATSNoRespondersException: 'No responders are available for the request.'

Can anyone help me?

KR Jörgen

Upvotes: 4

Views: 12995

Answers (5)

JNM
JNM

Reputation: 321

You get a 'no responder' when the server knows that there are no processes currently listening for your request. Rather than publishing the request and getting a timeout if no-one listening for those requests, this exception is there to let you know right away that there is currently no-one to service your request.

See this link for more information.

Upvotes: 5

IbrarMumtaz
IbrarMumtaz

Reputation: 4393

I ran into this issue in a c# code base and the way I solved it was by ensuring the sub' method was active first before the requester method was called.

I started by narrowing my runtime code down to the 2️⃣ tasks that were causing the issue to replicate it first. Then re-did the order they were executed in. Then I observed that order matters when it comes to NATs.

Quite different to how Azure Service Bus, things can start in any order but NATs based on localhost debugging,

I have had to re-order by background worker class to ensure any tasks that had a _natsClient.SubscribeAsync() call within were ran first then any tasks that a _natsClient.RequestAsync() call within were ran second.

Hope this helps someone.

Upvotes: 1

Ibrahim Bou Ncoula
Ibrahim Bou Ncoula

Reputation: 61

This could be too late now, but this Error also pops up when you push to a NON-EXISTING Subject!

Upvotes: 1

Rupak
Rupak

Reputation: 119

I got this error because I haven't enabled jetstreams

Run docker image with -js tag. It will work

 docker run -p 5555:4444 nats -p 4444 -js

For More reference https://hub.docker.com/_/nats/

Upvotes: 9

Jono
Jono

Reputation: 91

more specific, this is where it happens

    private bool StreamExists(IConnection connection, string streamName)
    {
        string json = "{\"offset\":0}";
        Msg message = connection.Request(NatsConstants.STREAMNAMESCMD, Encoding.UTF8.GetBytes(json), 3000); // HERE
        string responseString = Encoding.UTF8.GetString(message.Data);

        return responseString.Contains(streamName);
    }

Upvotes: 0

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