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 to generate the yaml files with the appropriate values:

RWO_STORAGE_CLASS="<RWO storage class for the volume used for etcd>"

DB2UCLUSTER_PRIMARY="<Primary Db2uCluster CR name>"

ETCD_ID="<New ETCD service and StatefulSet name>"

Set other environment variables to generate the required etcd yaml files:

DB2U_SA=account-${PROJECT_CPD_INSTANCE}-${DB2UCLUSTER_PRIMARY}

DB2U_VERSION=$(oc get db2ucluster ${DB2UCLUSTER_PRIMARY} -n ${PROJECT_CPD_INSTANCE} -ojsonpath="{.status.version}")

ETCD_IMAGE=$(oc get configmap db2u-release -n ${PROJECT_CPFS_OPS} -ojsonpath="{.data.json}" | jq -r ".databases.db2u.\"${DB2U_VERSION}\".images.etcd")

The following yaml file creates a StatefulSet with three replicas for deploying the etcd store, a persistent volume using volumeClaimTemplates to store the etcd data, and a service endpoint:


cat << EOF > ext_etcd.yaml
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: ${ETCD_ID}
  name: ${ETCD_ID}
  namespace: ${PROJECT_CPD_INSTANCE}
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_INSTANCE}
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

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