NATS Streaming

Fission uses NATS Streaming instead of pure NATS as the default message queue service.
Please ensure you use the correct library to connect to NATS Streaming service.


Fission installs the NATS streaming service by default when the fission-all helm chart is used for installation. And you can change the default setting in values.yaml before installation or upgrade.

You should see a pod with nats-streaming prefix with following command.

$ kubectl -n fission get pod -l svc=nats-streaming

If the NATS Streaming is enabled, a kubernetes deployment called mqtrigger-nats-streaming will be created as well.

$ kubectl -n fission get deploy|grep mqtrigger-nats-streaming

The Message Queue Trigger talks to NATS Streaming through Kubernetes service, you can get the service information with command.

$ kubectl -n fission get svc -l svc=nats-streaming
NAME             TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)    AGE
nats-streaming   ClusterIP   <none>        4222/TCP   6d
For further nats-streaming configuration/operation, please visit NATS docs.

Connection Information

Following are the default configuration while helm installation. (To change default configuration, see nats section of values.yaml.)

  • Authentication Token: defaultFissionAuthToken
  • NATS Streaming ClusterID: fissionMQTrigger

The FQDN of nats-streaming server by default is nats-streaming:4222 or using nats-streaming.fission:4222 if the producer is in different namespace. So the full connection information for NATS client is


If the connection information changed, please modify the environment variable of mqtrigger-nats-streaming deployment as well.

$ kubectl -n fission edit deployment mqtrigger-nats-streaming

Local Test

Create a message queue trigger that invokes any function you created before.

$ fission mqt create --name hello --function hello1 --topic foobar

To test the setup locally, we need to forward local ports traffic to nats-streaming server in kubernetes cluster.

$ export NATS_POD=$(kubectl -n fission get pod -l svc=nats-streaming -o name)
$ kubectl -n fission port-forward ${NATS_POD} 4222:4222

In this way we can connect to nats-streaming server locally with (NOTICE: for local test only)

$ cd ${GOPATH}/src/
$ go run stan-pub.go -s nats://defaultFissionAuthToken@ -c fissionMQTrigger -id clientPub foobar ""

Then, you should see the function invocation logs.

$ fission fn logs --name hello1
[2018-12-17 07:57:44.383563857 +0000 UTC] 2018/12/17 07:57:44 fetcher received fetch request and started downloading: {1 {hello-js-60kj  default    0 0001-01-01 00:00:00 +0000 UTC <nil> <nil> map[] map[] [] nil [] }   user [] [] false}
[2018-12-17 07:57:44.563666772 +0000 UTC] 2018/12/17 07:57:44 Successfully placed at /userfunc/user
[2018-12-17 07:57:44.563726739 +0000 UTC] 2018/12/17 07:57:44 Checking secrets/cfgmaps
[2018-12-17 07:57:44.563734156 +0000 UTC] 2018/12/17 07:57:44 Completed fetch request
[2018-12-17 07:57:44.563739212 +0000 UTC] 2018/12/17 07:57:44 elapsed time in fetch request = 299.120419ms
[2018-12-17 07:57:44.648270717 +0000 UTC] user code loaded in 0sec 0.240217ms
[2018-12-17 07:57:44.659143091 +0000 UTC] ::ffff: - - [17/Dec/2018:07:57:44 +0000] "POST /specialize HTTP/1.1" 202 - "-" "Go-http-client/1.1"
[2018-12-17 07:57:44.675180546 +0000 UTC] ::ffff: - - [17/Dec/2018:07:57:44 +0000] "POST / HTTP/1.1" 200 14 "-" "Go-http-client/1.1"


Following is the diagram of workable example. It demonstrates how to publish messages from a function and let message queue trigger to invoke another function.

The function publisher publishes a message to the target topic foobar. When message queue trigger receives the message, it then sends a POST request to the function hello.

You can find the fully workable example source code at here.

Last modified December 30, 2019: Add environment interface doc (#180) (c0e5b24)