Redis Replication Cluster Lifecycle Management

This guide demonstrates how to manage a Redis Replication Cluster's operational state in KubeBlocks, including:

Stopping the cluster to conserve resources
Starting a stopped cluster
Restarting cluster components

These operations help optimize resource usage and reduce operational costs in Kubernetes environments.

Lifecycle management operations in KubeBlocks:

Operation	Effect	Use Case
Stop	Suspends cluster, retains storage	Cost savings, maintenance
Start	Resumes cluster operation	Restore service after pause
Restart	Recreates pods for component	Configuration changes, troubleshooting

Prerequisites

Before proceeding, ensure the following:

Environment Setup:
- A Kubernetes cluster is up and running.
- The kubectl CLI tool is configured to communicate with your cluster.
- KubeBlocks CLI and KubeBlocks Operator are installed. Follow the installation instructions here.
Namespace Preparation: To keep resources isolated, create a dedicated namespace for this tutorial:

kubectl create ns demo
namespace/demo created

Deploy a Redis Replication Cluster

KubeBlocks uses a declarative approach for managing Redis Replication Clusters. Below is an example configuration for deploying a Redis Replication Cluster with two components, redis and redis sentinel.

Apply the following YAML configuration to deploy the cluster:

apiVersion: apps.kubeblocks.io/v1
kind: Cluster
metadata:
  name: redis-replication
  namespace: demo
spec:
  terminationPolicy: Delete
  clusterDef: redis
  topology: replication
  componentSpecs:
    - name: redis
      serviceVersion: "7.2.4"
      disableExporter: false
      replicas: 2
      resources:
        limits:
          cpu: '0.5'
          memory: 0.5Gi
        requests:
          cpu: '0.5'
          memory: 0.5Gi
      volumeClaimTemplates:
        - name: data
          spec:
            storageClassName: ""
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi
    - name: redis-sentinel
      replicas: 3
      resources:
        limits:
          cpu: '0.5'
          memory: 0.5Gi
        requests:
          cpu: '0.5'
          memory: 0.5Gi
      volumeClaimTemplates:
        - name: data
          spec:
            storageClassName: ""
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 20Gi

Verifying the Deployment

Monitor the cluster status until it transitions to the Running state:

kubectl get cluster redis-replication -n demo -w

Expected Output:

NAME                CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS    AGE
redis-replication   redis                Delete               Running   3m49s

Check the pod status and roles:

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

Expected Output:

NAME                                 READY   STATUS    RESTARTS   AGE     ROLE
redis-replication-redis-0            3/3     Running   0          3m38s   primary
redis-replication-redis-1            3/3     Running   0          3m16s   secondary
redis-replication-redis-sentinel-0   2/2     Running   0          4m35s
redis-replication-redis-sentinel-1   2/2     Running   0          4m17s
redis-replication-redis-sentinel-2   2/2     Running   0          3m59s

Once the cluster status becomes Running, your Redis cluster is ready for use.

TIP

If you are creating the cluster for the very first time, it may take some time to pull images before running.

Cluster Lifecycle Operations

Stopping the Cluster

Stopping a Redis Replication Cluster in KubeBlocks will:

Terminates all running pods
Retains persistent storage (PVCs)
Maintains cluster configuration

This operation is ideal for:

Temporary cost savings
Maintenance windows
Development environment pauses

Option 1: OpsRequest API

Create a Stop operation request:

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: redis-replication-stop-ops
  namespace: demo
spec:
  clusterName: redis-replication
  type: Stop

Option 2: Cluster API Patch

Modify the cluster spec directly by patching the stop field:

kubectl patch cluster redis-replication -n demo --type='json' -p='[
{
  "op": "add",
  "path": "/spec/componentSpecs/0/stop",
  "value": true
},
{
  "op": "add",
  "path": "/spec/componentSpecs/1/stop",
  "value": true
}
]'

Verifying Cluster Stop

To confirm a successful stop operation:

Check cluster status transition:

kubectl get cluster redis-replication -n demo -w

Example Output:

NAME                CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
redis-replication   redis                Delete               Stopping   6m3s
redis-replication   redis                Delete               Stopped    6m55s

Verify no running pods:

kubectl get pods -n demo

Example Output:

No resources found in demo namespace.

Confirm persistent volumes remain:

kubectl get pvc -n demo

Example Output:

NAME                                      STATUS   VOLUME     CAPACITY   ACCESS MODES
data-redis-replication-redis-0            Bound    pvc-uuid   20Gi       RWO
data-redis-replication-redis-1            Bound    pvc-uuid   20Gi       RWO
data-redis-replication-redis-sentinel-0   Bound    pvc-uuid   20Gi       RWO
data-redis-replication-redis-sentinel-1   Bound    pvc-uuid   20Gi       RWO
data-redis-replication-redis-sentinel-2   Bound    pvc-uuid   20Gi       RWO

Starting the Cluster

Starting a stopped Redis Replication Cluster:

Recreates all pods
Reattaches persistent storage
Restores service endpoints

Expected behavior:

Cluster returns to previous state
No data loss occurs
Services resume automatically

Initiate a Start operation request:

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: redis-replication-start-ops
  namespace: demo
spec:
  # Specifies the name of the Cluster resource that this operation is targeting.
  clusterName: redis-replication
  type: Start

Modify the cluster spec to resume operation:

Set stop: false, or

Remove the stop field entirely

kubectl patch cluster redis-replication -n demo --type='json' -p='[
{
  "op": "remove",
  "path": "/spec/componentSpecs/0/stop"
},
{
  "op": "remove",
  "path": "/spec/componentSpecs/1/stop"
}
]'

Verifying Cluster Start

To confirm a successful start operation:

Check cluster status transition:

kubectl get cluster redis-replication -n demo -w

Example Output:

NAME                CLUSTER-DEFINITION   TERMINATION-POLICY   STATUS     AGE
redis-replication   redis                Delete               Updating   22m
redis-replication   redis                Delete               Running    22m

Verify pod recreation:

kubectl get pods -n demo -l app.kubernetes.io/instance=redis-replication

Example Output:

NAME                       READY   STATUS    RESTARTS   AGE
redis-replication-redis-0   1/1     Running   0          2m
redis-replication-redis-1   1/1     Running   0          1m

Check service endpoints:

kubectl get endpoints redis-replication-redis-redis -n demo

Restarting Cluster

Restart operations provide:

Pod recreation without full cluster stop
Component-level granularity
Minimal service disruption

Use cases:

Configuration changes requiring restart
Resource refresh
Troubleshooting

Using OpsRequest API

Target specific components redis and redis-sentinel for restart:

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: redis-replication-restart-ops
  namespace: demo
spec:
  clusterName: redis-replication
  type: Restart
  restart:
  - componentName: redis
  - componentName: redis-sentinel

Verifying Restart Completion

To verify a successful component restart:

Track OpsRequest progress:

kubectl get opsrequest redis-replication-restart-ops -n demo -w

Example Output:

NAME                     TYPE      CLUSTER      STATUS    PROGRESS   AGE
redis-replication-restart-ops   Restart   redis-replication   Running   0/2        10s
redis-replication-restart-ops   Restart   redis-replication   Running   1/2        65s
redis-replication-restart-ops   Restart   redis-replication   Running   2/2        2m5s
redis-replication-restart-ops   Restart   redis-replication   Succeed   2/2        2m5s

Check pod status:
```
kubectl get pods -n demo -l app.kubernetes.io/instance=redis-replication
```
Note: Pods will show new creation timestamps after restart

Verify component health:

kbcli cluster describe redis-replication -n demo

Once the operation is complete, the cluster will return to the Running state.

To restart pods for Redis Component only, you can use:

apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: redis-replication-restart-redis
  namespace: demo
spec:
  clusterName: redis-replication
  type: Restart
  restart:
  - componentName: redis

Summary

In this guide, you learned how to:

Stop a Redis Replication Cluster to suspend operations while retaining persistent storage.
Start a stopped cluster to bring it back online.
Restart specific cluster components to recreate their Pods without stopping the entire cluster.

By managing the lifecycle of your Redis Replication Cluster, you can optimize resource utilization, reduce costs, and maintain flexibility in your Kubernetes environment. KubeBlocks provides a seamless way to perform these operations, ensuring high availability and minimal disruption.