How to connect nats streaming cluster - kubernetes

Question

I am new to kubernetes and trying to setup nats streaming cluster. I am using following manifest file. But I am confused with how can I access nats streaming server in my application. I am using azure kubernetes service.
---
apiVersion: v1
kind: ConfigMap
metadata:
name: stan-config
data:
stan.conf: |
# listen: nats-streaming:4222
port: 4222
http: 8222
streaming {
id: stan
store: file
dir: /data/stan/store
cluster {
node_id: $POD_NAME
log_path: /data/stan/log
# Explicit names of resulting peers
peers: ["nats-streaming-0", "nats-streaming-1", "nats-streaming-2"]
}
}
---
apiVersion: v1
kind: Service
metadata:
name: nats-streaming
labels:
app: nats-streaming
spec:
type: ClusterIP
selector:
app: nats-streaming
ports:
- port: 4222
targetPort: 4222
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: nats-streaming
labels:
app: nats-streaming
spec:
selector:
matchLabels:
app: nats-streaming
serviceName: nats-streaming
replicas: 3
volumeClaimTemplates:
- metadata:
name: stan-sts-vol
spec:
accessModes:
- ReadWriteOnce
volumeMode: "Filesystem"
resources:
requests:
storage: 1Gi
template:
metadata:
labels:
app: nats-streaming
spec:
# Prevent NATS Streaming pods running in same host.
affinity:
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- topologyKey: "kubernetes.io/hostname"
labelSelector:
matchExpressions:
- key: app
operator: In
values:
- nats-streaming
# STAN Server
containers:
- name: nats-streaming
image: nats-streaming
ports:
- containerPort: 8222
name: monitor
- containerPort: 7777
name: metrics
args:
- "-sc"
- "/etc/stan-config/stan.conf"
# Required to be able to define an environment variable
# that refers to other environment variables. This env var
# is later used as part of the configuration file.
env:
- name: POD_NAME
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: POD_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
volumeMounts:
- name: config-volume
mountPath: /etc/stan-config
- name: stan-sts-vol
mountPath: /data/stan
# Disable CPU limits.
resources:
requests:
cpu: 0
livenessProbe:
httpGet:
path: /
port: 8222
initialDelaySeconds: 10
timeoutSeconds: 5
volumes:
- name: config-volume
configMap:
name: stan-config
I tried using nats://nats-streaming:4222, but it gives following error.
stan: connect request timeout (possibly wrong cluster ID?)
I am referring https://docs.nats.io/nats-on-kubernetes/minimal-setup

Answer 1

You did not specified client port 4222 of nats in the StatefulSet, which you are calling inside your Service
...
ports:
- port: 4222
targetPort: 4222
...
As you can see from the simple-nats.yml they have setup the following ports:
...
containers:
- name: nats
image: nats:2.1.0-alpine3.10
ports:
- containerPort: 4222
name: client
hostPort: 4222
- containerPort: 7422
name: leafnodes
hostPort: 7422
- containerPort: 6222
name: cluster
- containerPort: 8222
name: monitor
- containerPort: 7777
name: metrics
command:
- "nats-server"
- "--config"
- "/etc/nats-config/nats.conf"
...
As for exposing the service outside, I would recommend reading Using a Service to Expose Your App and Exposing an External IP Address to Access an Application in a Cluster.
There is also nice article, maybe a bit old (2017) Exposing ports to Kubernetes pods on Azure, you can also check Azure docs about Quickstart: Deploy an Azure Kubernetes Service cluster using the Azure CLI