Upgrading the Minor Version of a ZooKeeper Cluster in KubeBlocks

This guide walks you through upgrading a ZooKeeper cluster to a newer minor version managed by KubeBlocks.

KubeBlocks performs a rolling upgrade: followers are upgraded one by one first, and the leader is upgraded last. This ensures the ensemble maintains quorum and client connections are not interrupted during the upgrade.

Prerequisites

Before proceeding, verify your environment meets these requirements:

• A functional Kubernetes cluster (v1.21+ recommended)
• kubectl v1.21+ installed and configured with cluster access
• Helm installed (installation guide)
• KubeBlocks installed (installation guide)
• ZooKeeper Add-on installed and a ZooKeeper cluster running (see Quickstart)

List Available ZooKeeper Versions

kubectl get componentversion zookeeper

NAME        VERSIONS                               STATUS      AGE
zookeeper   3.9.4,3.9.2,3.8.4,3.7.2,3.6.4,3.4.14   Available   6h

Step 1: Check the Current Version

kubectl get cluster zookeeper-cluster -n demo \
  -o jsonpath='{.spec.componentSpecs[0].serviceVersion}' && echo ""

3.9.2

Check the current pod roles:

kubectl get pods -n demo -l app.kubernetes.io/instance=zookeeper-cluster -L kubeblocks.io/role

NAME                            READY   STATUS    RESTARTS   AGE    ROLE
zookeeper-cluster-zookeeper-0   2/2     Running   0          12m    follower
zookeeper-cluster-zookeeper-1   2/2     Running   0          13m    follower
zookeeper-cluster-zookeeper-2   2/2     Running   0          14m    leader

Step 2: Apply the Upgrade

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: zk-upgrade
  namespace: demo
spec:
  clusterName: zookeeper-cluster
  type: Upgrade
  upgrade:
    components:
    - componentName: zookeeper
      serviceVersion: "3.9.4"

kubectl apply -f https://raw.githubusercontent.com/apecloud/kubeblocks-addons/refs/heads/main/examples/zookeeper/upgrade.yaml

kubectl get ops zk-upgrade -n demo -w

NAME         TYPE      CLUSTER             STATUS    PROGRESS   AGE
zk-upgrade   Upgrade   zookeeper-cluster   Running   0/3        6s
zk-upgrade   Upgrade   zookeeper-cluster   Running   1/3        74s
zk-upgrade   Upgrade   zookeeper-cluster   Running   2/3        2m25s
zk-upgrade   Upgrade   zookeeper-cluster   Running   3/3        3m34s
zk-upgrade   Upgrade   zookeeper-cluster   Succeed   3/3        3m34s

kubectl patch cluster zookeeper-cluster -n demo --type=json \
  -p='[{"op": "replace", "path": "/spec/componentSpecs/0/serviceVersion", "value": "3.9.4"}]'

kubectl get cluster zookeeper-cluster -n demo -w

Step 3: Verify the Upgrade

Check that all pods are running with the new version:

kubectl get pods -n demo -l app.kubernetes.io/instance=zookeeper-cluster -L kubeblocks.io/role

NAME                            READY   STATUS    RESTARTS   AGE    ROLE
zookeeper-cluster-zookeeper-0   2/2     Running   0          135m   follower
zookeeper-cluster-zookeeper-1   2/2     Running   0          137m   leader
zookeeper-cluster-zookeeper-2   2/2     Running   0          138m   follower

Confirm the image version:

kubectl get pods -n demo zookeeper-cluster-zookeeper-0 \
  -o jsonpath='{.spec.containers[?(@.name=="zookeeper")].image}' && echo ""

docker.io/apecloud/zookeeper:3.9.4

Cleanup

kubectl delete cluster zookeeper-cluster -n demo
kubectl delete ns demo