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Kafka Combined Volume Expansion

This guide will show you how to use KubeDB Ops-manager operator to expand the volume of a Kafka Combined Cluster.

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.

  • You must have a StorageClass that supports volume expansion.

  • 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: The yaml files used in this tutorial are stored in docs/examples/kafka folder in GitHub repository kubedb/docs.

Expand Volume of Combined Kafka Cluster

Here, we are going to deploy a Kafka combined using a supported version by KubeDB operator. Then we are going to apply KafkaOpsRequest to expand its volume.

Prepare Kafka Combined CLuster

At first verify that your cluster has a storage class, that supports volume expansion. Let’s check,

$ kubectl get storageclass
NAME                 PROVISIONER            RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
standard (default)   kubernetes.io/gce-pd   Delete          Immediate           true                   2m49s

We can see from the output the standard storage class has ALLOWVOLUMEEXPANSION field as true. So, this storage class supports volume expansion. We can use it.

Now, we are going to deploy a Kafka combined cluster with version 3.6.1.

Deploy Kafka

In this section, we are going to deploy a Kafka combined cluster with 1GB volume. Then, in the next section we will expand its volume to 2GB using KafkaOpsRequest CRD. Below is the YAML of the Kafka CR that we are going to create,

apiVersion: kubedb.com/v1
kind: Kafka
metadata:
  name: kafka-dev
  namespace: demo
spec:
  replicas: 2
  version: 3.6.1
  storage:
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
    storageClassName: standard
  storageType: Durable
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/kafka/volume-expansion/kafka-combined.yaml
kafka.kubedb.com/kafka-dev created

Now, wait until kafka-dev has status Ready. i.e,

$ kubectl get kf -n demo -w
NAME         TYPE            VERSION   STATUS         AGE
kafka-dev    kubedb.com/v1   3.6.1     Provisioning   0s
kafka-dev    kubedb.com/v1   3.6.1     Provisioning   24s
.
.
kafka-dev    kubedb.com/v1   3.6.1     Ready          92s

Let’s check volume size from petset, and from the persistent volume,

$ kubectl get petset -n demo kafka-dev -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"1Gi"

$ kubectl get pv -n demo                                       
NAME                   CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                             STORAGECLASS   REASON   AGE
pvc-23778f6015324895   1Gi        RWO            Delete           Bound    demo/kafka-dev-data-kafka-dev-1   standard                33s
pvc-30b34f642f994e13   1Gi        RWO            Delete           Bound    demo/kafka-dev-data-kafka-dev-0   standard                58s

You can see the petset has 1GB storage, and the capacity of all the persistent volumes are also 1GB.

We are now ready to apply the KafkaOpsRequest CR to expand the volume of this database.

Volume Expansion

Here, we are going to expand the volume of the kafka combined cluster.

Create KafkaOpsRequest

In order to expand the volume of the database, we have to create a KafkaOpsRequest CR with our desired volume size. Below is the YAML of the KafkaOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: KafkaOpsRequest
metadata:
  name: kf-volume-exp-combined
  namespace: demo
spec:
  type: VolumeExpansion  
  databaseRef:
    name: kafka-dev
  volumeExpansion:
    node: 2Gi
    mode: Online

Here,

  • spec.databaseRef.name specifies that we are performing volume expansion operation on kafka-dev.
  • spec.type specifies that we are performing VolumeExpansion on our database.
  • spec.volumeExpansion.node specifies the desired volume size.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/kafka/volume-expansion/kafka-volume-expansion-combined.yaml
kafkaopsrequest.ops.kubedb.com/kf-volume-exp-combined created

Verify Kafka Combined volume expanded successfully

If everything goes well, KubeDB Ops-manager operator will update the volume size of Kafka object and related PetSets and Persistent Volumes.

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

$ kubectl get kafkaopsrequest -n demo
NAME                     TYPE              STATUS       AGE
kf-volume-exp-combined   VolumeExpansion   Successful   2m4s

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

$ kubectl describe kafkaopsrequest -n demo kf-volume-exp-combined   
Name:         kf-volume-exp-combined
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         KafkaOpsRequest
Metadata:
  Creation Timestamp:  2024-07-30T10:45:57Z
  Generation:          1
  Resource Version:    91816
  UID:                 0febb459-3373-4f75-b7da-46391edf557f
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  kafka-dev
  Type:    VolumeExpansion
  Volume Expansion:
    Mode:  Online
    Node:  2Gi
Status:
  Conditions:
    Last Transition Time:  2024-07-30T10:45:57Z
    Message:               Kafka ops-request has started to expand volume of kafka nodes.
    Observed Generation:   1
    Reason:                VolumeExpansion
    Status:                True
    Type:                  VolumeExpansion
    Last Transition Time:  2024-07-30T10:46:05Z
    Message:               get pet set; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  GetPetSet
    Last Transition Time:  2024-07-30T10:46:05Z
    Message:               is petset deleted; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  IsPetsetDeleted
    Last Transition Time:  2024-07-30T10:46:15Z
    Message:               successfully deleted the petSets with orphan propagation policy
    Observed Generation:   1
    Reason:                OrphanPetSetPods
    Status:                True
    Type:                  OrphanPetSetPods
    Last Transition Time:  2024-07-30T10:46:20Z
    Message:               get pvc; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  GetPvc
    Last Transition Time:  2024-07-30T10:46:20Z
    Message:               is pvc patched; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  IsPvcPatched
    Last Transition Time:  2024-07-30T10:46:25Z
    Message:               compare storage; ConditionStatus:True
    Observed Generation:   1
    Status:                True
    Type:                  CompareStorage
    Last Transition Time:  2024-07-30T10:46:40Z
    Message:               successfully updated combined node PVC sizes
    Observed Generation:   1
    Reason:                UpdateCombinedNodePVCs
    Status:                True
    Type:                  UpdateCombinedNodePVCs
    Last Transition Time:  2024-07-30T10:46:45Z
    Message:               successfully reconciled the Kafka resources
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2024-07-30T10:46:51Z
    Message:               PetSet is recreated
    Observed Generation:   1
    Reason:                ReadyPetSets
    Status:                True
    Type:                  ReadyPetSets
    Last Transition Time:  2024-07-30T10:46:51Z
    Message:               Successfully completed volumeExpansion for kafka
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                                   Age   From                         Message
  ----     ------                                   ----  ----                         -------
  Normal   Starting                                 24m   KubeDB Ops-manager Operator  Start processing for KafkaOpsRequest: demo/kf-volume-exp-combined
  Normal   Starting                                 24m   KubeDB Ops-manager Operator  Pausing Kafka databse: demo/kafka-dev
  Normal   Successful                               24m   KubeDB Ops-manager Operator  Successfully paused Kafka database: demo/kafka-dev for KafkaOpsRequest: kf-volume-exp-combined
  Warning  get pet set; ConditionStatus:True        24m   KubeDB Ops-manager Operator  get pet set; ConditionStatus:True
  Warning  is petset deleted; ConditionStatus:True  24m   KubeDB Ops-manager Operator  is petset deleted; ConditionStatus:True
  Warning  get pet set; ConditionStatus:True        23m   KubeDB Ops-manager Operator  get pet set; ConditionStatus:True
  Normal   OrphanPetSetPods                         23m   KubeDB Ops-manager Operator  successfully deleted the petSets with orphan propagation policy
  Warning  get pvc; ConditionStatus:True            23m   KubeDB Ops-manager Operator  get pvc; ConditionStatus:True
  Warning  is pvc patched; ConditionStatus:True     23m   KubeDB Ops-manager Operator  is pvc patched; ConditionStatus:True
  Warning  get pvc; ConditionStatus:True            23m   KubeDB Ops-manager Operator  get pvc; ConditionStatus:True
  Warning  compare storage; ConditionStatus:True    23m   KubeDB Ops-manager Operator  compare storage; ConditionStatus:True
  Warning  get pvc; ConditionStatus:True            23m   KubeDB Ops-manager Operator  get pvc; ConditionStatus:True
  Warning  is pvc patched; ConditionStatus:True     23m   KubeDB Ops-manager Operator  is pvc patched; ConditionStatus:True
  Warning  get pvc; ConditionStatus:True            23m   KubeDB Ops-manager Operator  get pvc; ConditionStatus:True
  Warning  compare storage; ConditionStatus:True    23m   KubeDB Ops-manager Operator  compare storage; ConditionStatus:True
  Normal   UpdateCombinedNodePVCs                   23m   KubeDB Ops-manager Operator  successfully updated combined node PVC sizes
  Normal   UpdatePetSets                            23m   KubeDB Ops-manager Operator  successfully reconciled the Kafka resources
  Warning  get pet set; ConditionStatus:True        23m   KubeDB Ops-manager Operator  get pet set; ConditionStatus:True
  Normal   ReadyPetSets                             23m   KubeDB Ops-manager Operator  PetSet is recreated
  Normal   Starting                                 23m   KubeDB Ops-manager Operator  Resuming Kafka database: demo/kafka-dev
  Normal   Successful                               23m   KubeDB Ops-manager Operator  Successfully resumed Kafka database: demo/kafka-dev for KafkaOpsRequest: kf-volume-exp-combined

Now, we are going to verify from the Petset, and the Persistent Volumes whether the volume of the database has expanded to meet the desired state, Let’s check,

$ kubectl get petset -n demo kafka-dev -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"2Gi"

$ kubectl get pv -n demo                                       
NAME                   CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                             STORAGECLASS   REASON   AGE
pvc-23778f6015324895   2Gi        RWO            Delete           Bound    demo/kafka-dev-data-kafka-dev-1   standard                7m2s
pvc-30b34f642f994e13   2Gi        RWO            Delete           Bound    demo/kafka-dev-data-kafka-dev-0   standard                7m9s

The above output verifies that we have successfully expanded the volume of the Kafka.

Cleaning Up

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

kubectl delete kafkaopsrequest -n demo kf-volume-exp-combined
kubectl delete kf -n demo kafka-dev
kubectl delete ns demo

Next Steps