NATS Streaming with Fault Tolerance.

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NATS Streaming Cluster with FT Mode on AWS
Preparation
First, we need a Kubernetes cluster with a provider that offers a service with a ReadWriteMany filesystem available. In this short guide, we will create the cluster on AWS and then use EFS for the filesystem:
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# Create 3 nodes Kubernetes cluster
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eksctl create cluster --name stan-k8s \
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  --nodes 3 \
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  --node-type=t3.large \ # t3.small
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  --region=us-east-2
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​
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# Get the credentials for your cluster
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eksctl utils write-kubeconfig --name stan-k8s --region us-east-2
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For the FT mode to work, we will need to create an EFS volume which can be shared by more than one pod. Go into the AWS console and create one and make the sure that it is in a security group where the k8s nodes will have access to it. In case of clusters created via eksctl, this will be a security group named ClusterSharedNodeSecurityGroup:
Screen Shot 2019-12-04 at 11 25 08 AM
Screen Shot 2019-12-04 at 12 40 13 PM
Creating the EFS provisioner
Confirm from the FilesystemID from the cluster and the DNS name, we will use those values to create an EFS provisioner controller within the K8S cluster:
Screen Shot 2019-12-04 at 12 08 35 PM
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---
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apiVersion: v1
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kind: ServiceAccount
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metadata:
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  name: efs-provisioner
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---
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kind: ClusterRole
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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  name: efs-provisioner-runner
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rules:
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  - apiGroups: [""]
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    resources: ["persistentvolumes"]
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    verbs: ["get", "list", "watch", "create", "delete"]
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  - apiGroups: [""]
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    resources: ["persistentvolumeclaims"]
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    verbs: ["get", "list", "watch", "update"]
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  - apiGroups: ["storage.k8s.io"]
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    resources: ["storageclasses"]
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    verbs: ["get", "list", "watch"]
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  - apiGroups: [""]
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    resources: ["events"]
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    verbs: ["create", "update", "patch"]
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---
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kind: ClusterRoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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  name: run-efs-provisioner
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subjects:
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  - kind: ServiceAccount
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    name:
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      efs-provisioner
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      # replace with namespace where provisioner is deployed
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    namespace: default
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roleRef:
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  kind: ClusterRole
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  name: efs-provisioner-runner
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  apiGroup: rbac.authorization.k8s.io
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---
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kind: Role
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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  name: leader-locking-efs-provisioner
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rules:
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  - apiGroups: [""]
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    resources: ["endpoints"]
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    verbs: ["get", "list", "watch", "create", "update", "patch"]
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---
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kind: RoleBinding
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apiVersion: rbac.authorization.k8s.io/v1
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metadata:
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  name: leader-locking-efs-provisioner
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subjects:
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  - kind: ServiceAccount
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    name: efs-provisioner
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    # replace with namespace where provisioner is deployed
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    namespace: default
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roleRef:
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  kind: Role
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  name: leader-locking-efs-provisioner
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  apiGroup: rbac.authorization.k8s.io
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---
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apiVersion: v1
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kind: ConfigMap
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metadata:
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  name: efs-provisioner
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data:
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  file.system.id: fs-c22a24bb
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  aws.region: us-east-2
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  provisioner.name: synadia.com/aws-efs
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  dns.name: ""
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---
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kind: Deployment
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apiVersion: apps/v1
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metadata:
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  name: efs-provisioner
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spec:
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  replicas: 1
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  selector:
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    matchLabels:
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      app: efs-provisioner
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  strategy:
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    type: Recreate
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  template:
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    metadata:
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      labels:
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        app: efs-provisioner
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    spec:
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      serviceAccountName: efs-provisioner
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      containers:
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        - name: efs-provisioner
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          image: quay.io/external_storage/efs-provisioner:latest
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          env:
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            - name: FILE_SYSTEM_ID
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              valueFrom:
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                configMapKeyRef:
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                  name: efs-provisioner
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                  key: file.system.id
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            - name: AWS_REGION
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              valueFrom:
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                configMapKeyRef:
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                  name: efs-provisioner
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                  key: aws.region
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            - name: DNS_NAME
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              valueFrom:
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                configMapKeyRef:
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                  name: efs-provisioner
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                  key: dns.name
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​
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            - name: PROVISIONER_NAME
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              valueFrom:
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                configMapKeyRef:
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                  name: efs-provisioner
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                  key: provisioner.name
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          volumeMounts:
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            - name: pv-volume
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              mountPath: /efs
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      volumes:
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        - name: pv-volume
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          nfs:
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            server: fs-c22a24bb.efs.us-east-2.amazonaws.com
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            path: /
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---
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kind: StorageClass
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apiVersion: storage.k8s.io/v1
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metadata:
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  name: aws-efs
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provisioner: synadia.com/aws-efs
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---
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kind: PersistentVolumeClaim
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apiVersion: v1
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metadata:
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  name: efs
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  annotations:
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    volume.beta.kubernetes.io/storage-class: "aws-efs"
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spec:
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  accessModes:
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    - ReadWriteMany
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  resources:
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    requests:
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      storage: 1Mi
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Result of deploying the manifest:
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serviceaccount/efs-provisioner                                        created
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clusterrole.rbac.authorization.k8s.io/efs-provisioner-runner          created
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clusterrolebinding.rbac.authorization.k8s.io/run-efs-provisioner      created
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role.rbac.authorization.k8s.io/leader-locking-efs-provisioner         created
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rolebinding.rbac.authorization.k8s.io/leader-locking-efs-provisioner  created
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configmap/efs-provisioner                                             created
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deployment.extensions/efs-provisioner                                 created
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storageclass.storage.k8s.io/aws-efs                                   created
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persistentvolumeclaim/efs                                             created
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Setting up the NATS Streaming cluster
Now create a NATS Streaming cluster with FT mode enabled and using NATS embedded mode that is mounting the EFS volume:
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---
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apiVersion: v1
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kind: Service
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metadata:
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  name: stan
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  labels:
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    app: stan
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spec:
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  selector:
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    app: stan
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  clusterIP: None
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  ports:
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    - name: client
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      port: 4222
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    - name: cluster
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      port: 6222
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    - name: monitor
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      port: 8222
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    - name: metrics
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      port: 7777
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---
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apiVersion: v1
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kind: ConfigMap
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metadata:
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  name: stan-config
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data:
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  stan.conf: |
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    http: 8222
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​
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    cluster {
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      port: 6222
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      routes [
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        nats://stan-0.stan:6222
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        nats://stan-1.stan:6222
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        nats://stan-2.stan:6222
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      ]
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      cluster_advertise: $CLUSTER_ADVERTISE
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      connect_retries: 10
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    }
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​
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    streaming {
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      id: test-cluster
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      store: file
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      dir: /data/stan/store
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      ft_group_name: "test-cluster"
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      file_options {
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          buffer_size: 32mb
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          sync_on_flush: false
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          slice_max_bytes: 512mb
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          parallel_recovery: 64
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      }
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      store_limits {
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          max_channels: 10
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          max_msgs: 0
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          max_bytes: 256gb
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          max_age: 1h
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          max_subs: 128
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      }  
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    }
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---
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apiVersion: apps/v1
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kind: StatefulSet
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metadata:
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  name: stan
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  labels:
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    app: stan
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spec:
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  selector:
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    matchLabels:
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      app: stan
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  serviceName: stan
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  replicas: 3
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  volumeClaimTemplates:
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  template:
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    metadata:
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      labels:
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        app: stan
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    spec:
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      # STAN Server
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      terminationGracePeriodSeconds: 30
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​
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      containers:
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        - name: stan
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          image: nats-streaming:alpine
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​
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          ports:
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            # In case of NATS embedded mode expose these ports
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            - containerPort: 4222
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              name: client
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            - containerPort: 6222
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              name: cluster
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            - containerPort: 8222
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              name: monitor
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          args:
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            - "-sc"
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            - "/etc/stan-config/stan.conf"
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​
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          # Required to be able to define an environment variable
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          # that refers to other environment variables.  This env var
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          # is later used as part of the configuration file.
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          env:
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            - name: POD_NAME
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              valueFrom:
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                fieldRef:
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                  fieldPath: metadata.name
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            - name: POD_NAMESPACE
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              valueFrom:
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                fieldRef:
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                  fieldPath: metadata.namespace
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            - name: CLUSTER_ADVERTISE
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              value: $(POD_NAME).stan.$(POD_NAMESPACE).svc
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          volumeMounts:
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            - name: config-volume
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              mountPath: /etc/stan-config
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            - name: efs
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              mountPath: /data/stan
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          resources:
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            requests:
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              cpu: 0
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          livenessProbe:
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            httpGet:
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              path: /
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              port: 8222
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            initialDelaySeconds: 10
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            timeoutSeconds: 5
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        - name: metrics
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          image: synadia/prometheus-nats-exporter:0.5.0
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          args:
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            - -connz
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            - -routez
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            - -subz
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            - -varz
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            - -channelz
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            - -serverz
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            - http://localhost:8222
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          ports:
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            - containerPort: 7777
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              name: metrics
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      volumes:
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        - name: config-volume
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          configMap:
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            name: stan-config
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        - name: efs
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          persistentVolumeClaim:
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            claimName: efs
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Your cluster now will look something like this:
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kubectl get pods
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NAME                                     READY   STATUS    RESTARTS   AGE
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efs-provisioner-6b7866dd4-4k5wx          1/1     Running   0          21m
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stan-0                                   2/2     Running   0          6m35s
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stan-1                                   2/2     Running   0          4m56s
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stan-2                                   2/2     Running   0          4m42s
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If everything was setup properly, one of the servers will be the active node.
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$ kubectl logs stan-0 -c stan
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[1] 2019/12/04 20:40:40.429359 [INF] STREAM: Starting nats-streaming-server[test-cluster] version 0.16.2
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[1] 2019/12/04 20:40:40.429385 [INF] STREAM: ServerID: 7j3t3Ii7e2tifWqanYKwFX
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[1] 2019/12/04 20:40:40.429389 [INF] STREAM: Go version: go1.11.13
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[1] 2019/12/04 20:40:40.429392 [INF] STREAM: Git commit: [910d6e1]
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[1] 2019/12/04 20:40:40.454212 [INF] Starting nats-server version 2.0.4
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[1] 2019/12/04 20:40:40.454360 [INF] Git commit [c8ca58e]
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[1] 2019/12/04 20:40:40.454522 [INF] Starting http monitor on 0.0.0.0:8222
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[1] 2019/12/04 20:40:40.454830 [INF] Listening for client connections on 0.0.0.0:4222
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[1] 2019/12/04 20:40:40.454841 [INF] Server id is NB3A5RSGABLJP3WUYG6VYA36ZGE7MP5GVQIQVRG6WUYSRJA7B2NNMW57
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[1] 2019/12/04 20:40:40.454844 [INF] Server is ready
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[1] 2019/12/04 20:40:40.456360 [INF] Listening for route connections on 0.0.0.0:6222
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[1] 2019/12/04 20:40:40.481927 [INF] STREAM: Starting in standby mode
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[1] 2019/12/04 20:40:40.488193 [ERR] Error trying to connect to route (attempt 1): dial tcp: lookup stan on 10.100.0.10:53: no such host
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[1] 2019/12/04 20:40:41.489688 [INF] 192.168.52.76:40992 - rid:6 - Route connection created
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[1] 2019/12/04 20:40:41.489788 [INF] 192.168.52.76:40992 - rid:6 - Router connection closed
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[1] 2019/12/04 20:40:41.489695 [INF] 192.168.52.76:6222 - rid:5 - Route connection created
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[1] 2019/12/04 20:40:41.489955 [INF] 192.168.52.76:6222 - rid:5 - Router connection closed
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[1] 2019/12/04 20:40:41.634944 [INF] STREAM: Server is active
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[1] 2019/12/04 20:40:41.634976 [INF] STREAM: Recovering the state...
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[1] 2019/12/04 20:40:41.655526 [INF] STREAM: No recovered state
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[1] 2019/12/04 20:40:41.671435 [INF] STREAM: Message store is FILE
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[1] 2019/12/04 20:40:41.671448 [INF] STREAM: Store location: /data/stan/store
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[1] 2019/12/04 20:40:41.671524 [INF] STREAM: ---------- Store Limits ----------
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[1] 2019/12/04 20:40:41.671527 [INF] STREAM: Channels:                   10
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[1] 2019/12/04 20:40:41.671529 [INF] STREAM: --------- Channels Limits --------
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[1] 2019/12/04 20:40:41.671531 [INF] STREAM:   Subscriptions:           128
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[1] 2019/12/04 20:40:41.671533 [INF] STREAM:   Messages     :     unlimited
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[1] 2019/12/04 20:40:41.671535 [INF] STREAM:   Bytes        :     256.00 GB
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[1] 2019/12/04 20:40:41.671537 [INF] STREAM:   Age          :        1h0m0s
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[1] 2019/12/04 20:40:41.671539 [INF] STREAM:   Inactivity   :     unlimited *
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[1] 2019/12/04 20:40:41.671541 [INF] STREAM: ----------------------------------
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[1] 2019/12/04 20:40:41.671546 [INF] STREAM: Streaming Server is ready
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NATS Streaming Cluster with FT Mode on Azure
First need to create a PVC (PersistentVolumeClaim), in Azure we can use azurefile to get a volume with ReadWriteMany:
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---
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kind: PersistentVolumeClaim
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apiVersion: v1
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metadata:
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  name: stan-efs
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  annotations:
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    volume.beta.kubernetes.io/storage-class: "azurefile"
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spec:
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  accessModes:
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    - ReadWriteMany
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  resources:
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    requests:
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      storage: 100Mi
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Next create a NATS cluster using the Helm charts:
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helm repo add nats https://nats-io.github.io/k8s/helm/charts/
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helm install nats nats/nats
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To create an FT setup using AzureFile you can use the following Helm chart values file:
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stan:
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  image: nats-streaming:alpine
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  replicas: 2
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  nats:
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    url: nats://nats:4222
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store:
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  type: file
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  ft:
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    group: my-group
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  file:
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    path: /data/stan/store
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  volume:
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    enabled: true
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​
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    # Mount path for the volume.
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    mount: /data/stan
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​
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    # FT mode requires a single shared ReadWriteMany PVC volume.
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    persistentVolumeClaim:
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      claimName: stan-efs
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Now deploy with Helm:
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helm install stan nats/stan -f ./examples/deploy-stan-ft-file.yaml
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Send a few commands to the NATS Server to which STAN/NATS Streaming is connected:
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kubectl port-forward nats-0 4222:4222 &
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​
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stan-pub -c stan foo bar.1
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stan-pub -c stan foo bar.2
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stan-pub -c stan foo bar.3
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Subscribe to get all the messages:
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stan-sub -c stan  -all foo
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Contents
NATS Streaming Cluster with FT Mode on AWS
Preparation
NATS Streaming Cluster with FT Mode on Azure