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Reconfigure ZooKeeper Ensemble

This guide will show you how to use KubeDB Ops-manager operator to reconfigure a ZooKeeper ensemble.

Before You Begin

At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster.
Install KubeDB Provisioner and Ops-manager operator in your cluster following the steps here.
You should be familiar with the following KubeDB concepts:

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in examples directory of kubedb/docs repository.

Now, we are going to deploy a ZooKeeper cluster using a supported version by KubeDB operator. Then we are going to apply ZooKeeperOpsRequest to reconfigure its configuration.

Prepare ZooKeeper Ensemble

Now, we are going to deploy a ZooKeeper cluster with version 3.8.3.

Deploy ZooKeeper Ensemble

At first, we will create secret named zk-configuration containing required configuration settings.

apiVersion: v1
stringData:
  zoo.cfg: |
    maxClientCnxns=70    
kind: Secret
metadata:
  name: zk-configuration
  namespace: demo

Here, maxClientCnxns is set to 70, whereas the default value is 60.

Now, we will apply the secret with custom configuration.

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.4.30/docs/examples/zookeeper/reconfiguration/secret.yaml
secret/zk-configuration created

In this section, we are going to create a ZooKeeper object specifying spec.configSecret field to apply this custom configuration. Below is the YAML of the ZooKeeper CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: ZooKeeper
metadata:
  name: zk-quickstart
  namespace: demo
spec:
  version: "3.8.3"
  adminServerPort: 8080
  replicas: 3
  configSecret:
    name: zk-configuration
  storage:
    resources:
      requests:
        storage: "1Gi"
    accessModes:
      - ReadWriteOnce
  deletionPolicy: "WipeOut"

Let’s create the ZooKeeper CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.4.30/docs/examples/zookeeper/reconfiguration/sample-zk-configuration.yaml
zookeeper.kubedb.com/zk-quickstart created

Now, wait until zk-quickstart has status Ready. i.e,

$ kubectl get zk -n demo
NAME               VERSION     STATUS    AGE
zk-quickstart      3.8.3      Ready     23s

Now, we will check if the database has started with the custom configuration we have provided.

Now, you can exec into the zookeeper pod and find if the custom configuration is there,

$ Defaulted container "zookeeper" out of: zookeeper, zookeeper-init (init)
zookeeper@zk-quickstart-0:/apache-zookeeper-3.8.3-bin$ echo conf | nc localhost 2181
clientPort=2181
secureClientPort=-1
dataDir=/data/version-2
dataDirSize=134218330
dataLogDir=/data/version-2
dataLogSize=134218330
tickTime=2000
maxClientCnxns=70
minSessionTimeout=4000
maxSessionTimeout=40000
clientPortListenBacklog=-1
serverId=1
initLimit=10
syncLimit=2
electionAlg=3
electionPort=3888
quorumPort=2888
peerType=0
membership: 
server.1=zk-quickstart-0.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
server.2=zk-quickstart-1.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
server.3=zk-quickstart-2.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
version=100000011zookeeper@zk-quickstart-0:/apache-zookeeper-3.8.3-bin$ exit
exit

As we can see from the configuration of running zookeeper, the value of maxClientCnxns has been set to 70.

Reconfigure using new secret

Now we will reconfigure this database to set maxClientCnxns to 100.

At first, we will create secret named new-configuration containing required configuration settings.

apiVersion: v1
stringData:
  zoo.cfg: |
    maxClientCnxns=100    
kind: Secret
metadata:
  name: zk-new-configuration
  namespace: demo

Here, maxClientCnxns is set to 100.

Now, we will apply the secret with custom configuration.

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.4.30/docs/examples/zookeeper/reconfiguration/new-secret.yaml
secret/zk-new-configuration created

Create ZooKeeperOpsRequest

Now, we will use this secret to replace the previous secret using a ZooKeeperOpsRequest CR. The ZooKeeperOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: ZooKeeperOpsRequest
metadata:
  name: zk-reconfig
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: zk-quickstart
  configuration:
    configSecret:
      name: zk-new-configuration

Here,

spec.databaseRef.name specifies that we are reconfiguring zk-quickstart database.
spec.type specifies that we are performing Reconfigure on our database.
spec.configuration.configSecret.name specifies the name of the new secret.

Let’s create the ZooKeeperOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2025.4.30/docs/examples/zookeeper/reconfiguration/zkops-reconfiguration.yaml
zookeeperopsrequest.ops.kubedb.com/zk-reconfig created

Verify the new configuration is working

If everything goes well, KubeDB Ops-manager operator will update the configSecret of ZooKeeper object.

Let’s wait for ZooKeeperOpsRequest to be Successful. Run the following command to watch ZooKeeperOpsRequest CR,

$ watch kubectl get zookeeperopsrequest -n demo
Every 2.0s: kubectl get zookeeperopsrequest -n demo
NAME               TYPE          STATUS       AGE
zk-reconfig        Reconfigure   Successful   1m

We can see from the above output that the ZooKeeperOpsRequest has succeeded. If we describe the ZooKeeperOpsRequest we will get an overview of the steps that were followed to reconfigure the database.

$ kubectl describe zookeeperopsrequest -n demo zk-reconfig
Name:         zk-reconfig
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         ZooKeeperOpsRequest
Metadata:
  Creation Timestamp:  2024-10-30T08:27:00Z
  Generation:          1
  Resource Version:    1548116
  UID:                 4f3daa11-c41b-4079-a8d8-1040931284ef
Spec:
  Apply:  IfReady
  Configuration:
    Config Secret:
      Name:  zk-new-configuration
  Database Ref:
    Name:  zk-quickstart
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2024-10-30T08:27:00Z
    Message:               ZooKeeper ops-request has started to reconfigure ZooKeeper nodes
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2024-10-30T08:27:08Z
    Message:               successfully reconciled the ZooKeeper with new configure
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2024-10-30T08:29:18Z
    Message:               Successfully restarted all nodes
    Observed Generation:   1
    Reason:                RestartNodes
    Status:                True
    Type:                  RestartNodes
    Last Transition Time:  2024-10-30T08:27:13Z
    Message:               get pod; ConditionStatus:True; PodName:zk-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--zk-quickstart-0
    Last Transition Time:  2024-10-30T08:27:13Z
    Message:               evict pod; ConditionStatus:True; PodName:zk-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--zk-quickstart-0
    Last Transition Time:  2024-10-30T08:27:18Z
    Message:               running pod; ConditionStatus:False
    Observed Generation:   1
    Status:                False
    Type:                  RunningPod
    Last Transition Time:  2024-10-30T08:27:58Z
    Message:               get pod; ConditionStatus:True; PodName:zk-quickstart-1
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--zk-quickstart-1
    Last Transition Time:  2024-10-30T08:27:58Z
    Message:               evict pod; ConditionStatus:True; PodName:zk-quickstart-1
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--zk-quickstart-1
    Last Transition Time:  2024-10-30T08:28:38Z
    Message:               get pod; ConditionStatus:True; PodName:zk-quickstart-2
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--zk-quickstart-2
    Last Transition Time:  2024-10-30T08:28:38Z
    Message:               evict pod; ConditionStatus:True; PodName:zk-quickstart-2
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--zk-quickstart-2
    Last Transition Time:  2024-10-30T08:29:18Z
    Message:               Successfully completed reconfigure ZooKeeper
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:                    <none>

Now need to check the new configuration we have provided.

Now, wait until zk-quickstart has status Ready. i.e,

$ kubectl get zk -n demo
NAME            VERSION     STATUS    AGE
zk-quickstart   3.8.3      Ready     20s

Now let’s exec into the zookeeper pod and check the new configuration we have provided.

$ Defaulted container "zookeeper" out of: zookeeper, zookeeper-init (init)
zookeeper@zk-quickstart-0:/apache-zookeeper-3.8.3-bin$ echo conf | nc localhost 2181
clientPort=2181
secureClientPort=-1
dataDir=/data/version-2
dataDirSize=134218330
dataLogDir=/data/version-2
dataLogSize=134218330
tickTime=2000
maxClientCnxns=100
minSessionTimeout=4000
maxSessionTimeout=40000
clientPortListenBacklog=-1
serverId=1
initLimit=10
syncLimit=2
electionAlg=3
electionPort=3888
quorumPort=2888
peerType=0
membership: 
server.1=zk-quickstart-0.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
server.2=zk-quickstart-1.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
server.3=zk-quickstart-2.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
version=100000011zookeeper@zk-quickstart-0:/apache-zookeeper-3.8.3-bin$ exit
exit

As we can see from the configuration of running zookeeper, the value of maxClientCnxns has been changed from 70 to 100. So the reconfiguration of the zookeeper is successful.

Reconfigure using apply config

Now we will reconfigure this database again to set maxClientCnxns to 90. This time we won’t use a new secret. We will use the applyConfig field of the ZooKeeperOpsRequest. This will merge the new config in the existing secret.

Create ZooKeeperOpsRequest

Now, we will use the new configuration in the data field in the ZooKeeperOpsRequest CR. The ZooKeeperOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: ZooKeeperOpsRequest
metadata:
  name: zk-reconfig-apply
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: zk-quickstart
  configuration:
    applyConfig:
      zoo.cfg: |
        maxClientCnxns=90

Here,

spec.databaseRef.name specifies that we are reconfiguring zk-quickstart database.
spec.type specifies that we are performing Reconfigure on our database.
spec.configuration.applyConfig specifies the new configuration that will be merged in the existing secret.

Let’s create the ZooKeeperOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2025.4.30/docs/examples/zookeeper/reconfiguration/zkops-apply-reconfiguration.yaml
zookeeperopsrequest.ops.kubedb.com/zk-reconfig-apply created

Verify the new configuration is working

If everything goes well, KubeDB Ops-manager operator will merge this new config with the existing configuration.

Let’s wait for ZooKeeperOpsRequest to be Successful. Run the following command to watch ZooKeeperOpsRequest CR,

$ watch kubectl get zookeeperopsrequest -n demo
NAME                 TYPE          STATUS       AGE
zk-reconfig-apply    Reconfigure   Successful   38s

$ kubectl describe zookeeperopsrequest -n demo zk-reconfig-apply
Name:         zk-reconfig-apply
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         ZooKeeperOpsRequest
Metadata:
  Creation Timestamp:  2024-10-30T08:27:00Z
  Generation:          1
  Resource Version:    1548116
  UID:                 4f3daa11-c41b-4079-a8d8-1040931284ef
Spec:
  Apply:  IfReady
  Configuration:
    Config Secret:
      Name:  zk-new-configuration
  Database Ref:
    Name:  zk-quickstart
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2024-10-30T08:27:00Z
    Message:               ZooKeeper ops-request has started to reconfigure ZooKeeper nodes
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2024-10-30T08:27:08Z
    Message:               successfully reconciled the ZooKeeper with new configure
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2024-10-30T08:29:18Z
    Message:               Successfully restarted all nodes
    Observed Generation:   1
    Reason:                RestartNodes
    Status:                True
    Type:                  RestartNodes
    Last Transition Time:  2024-10-30T08:27:13Z
    Message:               get pod; ConditionStatus:True; PodName:zk-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--zk-quickstart-0
    Last Transition Time:  2024-10-30T08:27:13Z
    Message:               evict pod; ConditionStatus:True; PodName:zk-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--zk-quickstart-0
    Last Transition Time:  2024-10-30T08:27:18Z
    Message:               running pod; ConditionStatus:False
    Observed Generation:   1
    Status:                False
    Type:                  RunningPod
    Last Transition Time:  2024-10-30T08:27:58Z
    Message:               get pod; ConditionStatus:True; PodName:zk-quickstart-1
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--zk-quickstart-1
    Last Transition Time:  2024-10-30T08:27:58Z
    Message:               evict pod; ConditionStatus:True; PodName:zk-quickstart-1
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--zk-quickstart-1
    Last Transition Time:  2024-10-30T08:28:38Z
    Message:               get pod; ConditionStatus:True; PodName:zk-quickstart-2
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--zk-quickstart-2
    Last Transition Time:  2024-10-30T08:28:38Z
    Message:               evict pod; ConditionStatus:True; PodName:zk-quickstart-2
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--zk-quickstart-2
    Last Transition Time:  2024-10-30T08:29:18Z
    Message:               Successfully completed reconfigure ZooKeeper
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:                    <none>

Now need to check the new configuration we have provided.

Now, wait until zk-quickstart has status Ready. i.e,

$ kubectl get zk -n demo
NAME            VERSION     STATUS    AGE
zk-quickstart   3.8.3      Ready     20s

Now let’s exec into the zookeeper pod and check the new configuration we have provided.

$ Defaulted container "zookeeper" out of: zookeeper, zookeeper-init (init)
zookeeper@zk-quickstart-0:/apache-zookeeper-3.8.3-bin$ echo conf | nc localhost 2181
clientPort=2181
secureClientPort=-1
dataDir=/data/version-2
dataDirSize=134218330
dataLogDir=/data/version-2
dataLogSize=134218330
tickTime=2000
maxClientCnxns=90
minSessionTimeout=4000
maxSessionTimeout=40000
clientPortListenBacklog=-1
serverId=1
initLimit=10
syncLimit=2
electionAlg=3
electionPort=3888
quorumPort=2888
peerType=0
membership: 
server.1=zk-quickstart-0.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
server.2=zk-quickstart-1.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
server.3=zk-quickstart-2.zk-quickstart-pods.demo.svc.cluster.local:2888:3888:participant;0.0.0.0:2181
version=100000011zookeeper@zk-quickstart-0:/apache-zookeeper-3.8.3-bin$ exit
exit

As we can see from the configuration of running zookeeper, the value of maxClientCnxns has been changed from 100 to 90. So, the reconfiguration of the database using the applyConfig field is successful.

Cleaning Up

To clean up the Kubernetes resources created by this tutorial, run:

kubectl delete zk -n demo zk-quickstart
kubectl delete zookeeperopsrequest -n demo zk-reconfig zk-reconfig-apply

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Reconfigure ZooKeeper Ensemble

Before You Begin

Prepare ZooKeeper Ensemble

Deploy ZooKeeper Ensemble

Reconfigure using new secret

Create ZooKeeperOpsRequest

Verify the new configuration is working

Reconfigure using apply config

Create ZooKeeperOpsRequest

Verify the new configuration is working

Cleaning Up

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