Deploy etcd packaged with the Db2 installation

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You can use a YAML file to configure the etcd store that comes packaged with Db2 for your HADR configuration on a Red Hat OpenShift cluster.

About this task

The etcd store enables automated failover.

Procedure

Set the following environment variables:
1. Set the RWO_STORAGE_CLASS environment variable to the volume used for the etcd:
```
export RWO_STORAGE_CLASS=<storage_volume>
```
2. Set the DB2UCLUSTER_PRIMARY environment variable to the name of the cluster with your Db2 installation:
```
export DB2UCLUSTER_PRIMARY=<Db2uCluster_name>
```
3. Set the ETCD_ID environment variable to the name of the etcd service and StatefulSet:
```
ETCD_ID=<ETCD_service_and_StatefulSet_name>
```
4. Set other environment variables to generate the required etcd YAML files.
  Set DB2U_SA to the Service Account used for the primary Db2U deployment:
```
DB2U_SA=account-${PROJECT_CPD_INST_OPERANDS}-${DB2UCLUSTER_PRIMARY}
```
  Set DB2U_VERSION to the etcd image for your release:
```
DB2U_VERSION=$(oc get db2ucluster ${DB2UCLUSTER_PRIMARY} -n ${PROJECT_CPD_INST_OPERANDS} -ojsonpath="{.status.version}")
```
  Set ETCD_IMAGE to the Db2 version being used for the primary Db2UCluster.
```
ETCD_IMAGE=$(oc get configmap db2u-release -n ${PROJECT_CPD_INST_OPERATORS} -ojsonpath="{.data.json}" | jq -r ".databases.db2u.\"${DB2U_VERSION}\".images.etcd")
```

Run the following command to create a StatefulSet:

The following YAML file creates a StatefulSet with three replicas for the following reasons:

Deploying the etcd store.
A persistent volume using volumeClaimTemplates to store the etcd data.
Creating a service endpoint.


cat << EOF > ext_etcd.yaml
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: ${ETCD_ID}
  name: ${ETCD_ID}
  namespace: ${PROJECT_CPD_INST_OPERANDS}
spec:
  clusterIP: None
  clusterIPs:
  - None
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - name: etcd
    port: 2379
    protocol: TCP
    targetPort: 2379
  - name: peer
    port: 2380
    protocol: TCP
    targetPort: 2380
  publishNotReadyAddresses: true
  selector:
    app: ${ETCD_ID}
  sessionAffinity: None
  type: ClusterIP
status:
  loadBalancer: {}
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    app: ${ETCD_ID}
  name: ${ETCD_ID}
  namespace: ${PROJECT_CPD_INST_OPERANDS}
spec:
  podManagementPolicy: Parallel
  replicas: 3
  revisionHistoryLimit: 10
  selector:
    matchLabels:
      app: ${ETCD_ID}
  serviceName: ${ETCD_ID}
  template:
    metadata:
      labels:
        app: ${ETCD_ID}
    spec:
     # affinity:                                              # nodeSelector can be used to deploy etcd on a set of nodes
     #   nodeAffinity:                                        # Label the nodes in the nodegroup for etcd and use the labels 
     #     requiredDuringSchedulingIgnoredDuringExecution:    # in this yaml
     #       nodeSelectorTerms:
     #       - matchExpressions:
     #         - key: db2u
     #           operator: In
     #           values:
     #           - etcd
      containers:
      - command:
        - /scripts/start.sh
        env:
        - name: SERVICENAME
          value: ${ETCD_ID}
        - name: role
          value: etcd
        - name: INITIAL_CLUSTER_SIZE
          value: "3"
        - name: SET_NAME
          value: ${ETCD_ID}
        - name: RUNTIME_ENV
          value: LOCAL
        - name: ETCDCTL_API
          value: "3"
        image: ${ETCD_IMAGE}
        imagePullPolicy: IfNotPresent
        lifecycle:
          preStop:
            exec:
              command:
              - /scripts/stop.sh
        livenessProbe:
          failureThreshold: 5
          initialDelaySeconds: 30
          periodSeconds: 30
          successThreshold: 1
          tcpSocket:
            port: 2379
          timeoutSeconds: 1
        name: etcd
        readinessProbe:
          failureThreshold: 5
          initialDelaySeconds: 15
          periodSeconds: 15
          successThreshold: 1
          tcpSocket:
            port: 2379
          timeoutSeconds: 3
        resources:
          limits:
            cpu: 500m
            ephemeral-storage: 10Mi
            memory: 512Mi
          requests:
            cpu: 100m
            ephemeral-storage: 5Mi
            memory: 256Mi
        securityContext:
          allowPrivilegeEscalation: false
          capabilities:
            drop:
            - ALL
          privileged: false
          readOnlyRootFilesystem: false
        terminationMessagePath: /dev/termination-log
        terminationMessagePolicy: File
        volumeMounts:
        - mountPath: /persistence
          name: etcd
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext:
        runAsNonRoot: true
        runAsUser: 1001
        runAsGroup: 2001
        fsGroup: 2001
      serviceAccount: ${DB2U_SA}            # !!!!! replace the serviceAccount and serviceAccountName
      serviceAccountName: ${DB2U_SA}        # !!!!!  with the one created with your db2oltp deployment
      terminationGracePeriodSeconds: 120
     # tolerations:                                      # Use tolerations if you're planning to taint the nodes created
     # - effect: NoSchedule                              # in the etcd nodegroup
     #   key: db2u
     #   operator: Equal
     #   value: etcd
  volumeClaimTemplates:
  - apiVersion: v1
    kind: PersistentVolumeClaim
    metadata:
      annotations:
        app: ${ETCD_ID}
      name: etcd
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 5Gi
      storageClassName: ${RWO_STORAGE_CLASS}              # Storage class for the volume used for etcd. Replace with any RWO storage class
      volumeMode: Filesystem
  updateStrategy:
    rollingUpdate:
      partition: 0
    type: RollingUpdate
EOF

Update the nodeSelector and tolerations fields to deploy etcd on dedicated nodes by adding the required labels.
Create the resources by running the following command:
```
oc apply -f ext_etcd.yaml
```