Barebones NATS JetStream clustering in Kubernetes with PVC and no Helm charts

README.md

Prerequisites:

1. kubectl ( https://kubernetes.io/docs/tasks/tools/install-kubectl-macos/#install-kubectl-binary-with-curl-on-macos )
2. nats cli ( https://github.com/nats-io/natscli )

$ nats context save tma-remote
$ vi ~/.config/nats/context/tma-remote.json
{
  "url": "nats://{CLOUD PROVIDER LOAD BALANCER EXTERNAL IP}", # kubectl get services
  "user": "admin",
  "password": "password"
}
$ nats context select tma-remote

$ while :; do clear; nats server ls --sort=name; sleep 1; done

nats-depl.yaml

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: nats
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nats
  # https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#stable-network-id
  serviceName: nats-headless
  template:
    metadata:
      labels:
        app: nats
    spec:
      containers:
        - name: nats
          image: nats:alpine
          args: ["-p", "4222", "-c", "/etc/nats/nats-server.conf"]
          ports:
            - name: nats-client
              containerPort: 4222
            - name: nats-cluster
              containerPort: 6222
          volumeMounts:
            - name: nats-server-configmap
              mountPath: /etc/nats/
            - name: nats-pvc
              mountPath: /data
      volumes:
        - name: nats-server-configmap
          configMap:
            name: nats-server-config-cm
  volumeClaimTemplates:
    - metadata:
        name: nats-pvc
      spec:
        accessModes: ["ReadWriteOnce"]
        # Consult your cloud provider with regards to available PVC classes
        # otherwise dynamic provisioning will probably fail
        storageClassName: do-block-storage
        resources:
          requests:
            storage: 5Gi
---
# StatefulSets currently require a Headless Service to be responsible 
# for the network identity of the Pods. You are responsible for creating this Service.

# https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#stable-network-id
apiVersion: v1
kind: Service
metadata:
  name: nats-headless
spec:
# $ kubectl -n kube-system get svc kube-dns
# NAME       TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)                  AGE
# kube-dns   ClusterIP   10.245.0.10   <none>        53/UDP,53/TCP,9153/TCP   4d22h
# $ kubectl get ep
# NAME            ENDPOINTS                                                          AGE
# kubernetes      100.65.58.7:443                                                    4d22h
# nats-headless   10.244.0.119:4222,10.244.0.195:4222,10.244.1.83:4222 + 3 more...   18m
# $ kubectl exec -it nats-0 -- /bin/ash
# # nslookup 10.244.0.119 10.245.0.10
  clusterIP: None
  selector:
    app: nats
  ports:
    - name: nats
      protocol: TCP
      port: 4222
      targetPort: 4222
    - name: nats-cluster
      protocol: TCP
      port: 6222
      targetPort: 6222
---
apiVersion: v1
kind: Service
metadata:
  name: nats-lb-srv
spec:
  type: LoadBalancer
  selector:
    app: nats
  ports:
    - name: http
      protocol: TCP
      port: 4222
      targetPort: 4222

server.conf.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: nats-server-config-cm
data:
  # https://github.com/nats-io/nats-docker/blob/256811340a89b8a3b78f1a144b6a87fba4424b67/2.10.x/scratch/Dockerfile#L9
  # https://docs.nats.io/running-a-nats-service/configuration/clustering/jetstream_clustering#raft
  nats-server.conf: |
    server_name=$HOSTNAME

    accounts: {
      $SYS: {
        users: [
          { user: admin, password: password }
        ]
      },
      TMA: {
        jetstream: enabled,
        users: [
          { user: me, password: admin }
        ]
      }
    }

    jetstream {
      "store_dir": "/data"
    }

    cluster: {
      name: EU,
      port: 6222,
      routes: [
        "nats://nats-0.nats-headless:6222"
      ]
    }

# Since the cluster uses a gossiping protocol to uncover other replicas, we don't need to specify
# the URL's for all seed servers in the routes array, we can keep only the first one

# The official deployment files however keep all the routes in the config
#     routes: [
#       "nats://nats-0.nats-headless:6222",
#       "nats://nats-1.nats-headless:6222",
#       "nats://nats-2.nats-headless:6222",
#     ]