KubeDB

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Replace Sentinel

This guide will show you how to use KubeDB Enterprise operator to replace Sentinel instance of Redis Database.

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. If you do not already have a cluster, you can create one by using kind.

  • Install KubeDB Community and Enterprise 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 docs/examples/redis directory of kubedb/docs repository.

Apply ReplaceSentinel

Here, we are going to deploy a Redis and RedisSentinel instance using a supported version by KubeDB operator. Then we are going to create another RedisSentinel, and it will replace the old sentinel.

Prepare RedisSentinel

Now, we are going to deploy a RedisSentinel version 8.2.2.

apiVersion: kubedb.com/v1
kind: RedisSentinel
metadata:
  name: sen-demo
  namespace: demo
spec:
  version: 8.2.2
  replicas: 3
  storageType: Durable
  storage:
    resources:
      requests:
        storage: 1Gi
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2026.6.19/docs/examples/redis/sentinel/sentinel.yaml
redissentinel.kubedb.com/sen-demo created

Now, wait until sen-dmo has status Ready. i.e. ,

$ kubectl get redissentinel -n demo
NAME       VERSION   STATUS   AGE
sen-demo   6.2.14     Ready    96s

Deploy Redis in Sentinel Mode

In this section, we are going to deploy a Redis database in Sentinel Mode.

apiVersion: kubedb.com/v1
kind: Redis
metadata:
  name: rd-demo
  namespace: demo
spec:
  version: 8.2.2
  replicas: 3
  sentinelRef:
    name: sen-demo
    namespace: demo
  mode: Sentinel
  storageType: Durable
  storage:
    resources:
      requests:
        storage: 1Gi
    storageClassName: "standard"
    accessModes:
      - ReadWriteOnce
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2026.6.19/docs/examples/redis/sentinel/redis.yaml
redis.kubedb.com/rd-demo created

Now, wait until rd-demo has status Ready. i.e. ,

NAME      VERSION   STATUS   AGE
rd-demo   6.2.14     Ready    67s

Lets exec into a sentinel pod, and make sure sentinel monitors redis master

$ kubectl exec -it -n demo sen-demo-0 -c redissentinel -- bash
root@sen-demo-0:/data# redis-cli -p 26379 sentinel masters
1)  1) "name"
    2) "demo/rd-demo"
    3) "ip"
    4) "rd-demo-0.rd-demo-pods.demo.svc"
    5) "port"
    6) "6379"
    7) "runid"
    8) "ae368ff430018c9ef2e4c418aa1d5af1869e01a6"
    9) "flags"
   10) "master"
   11) "link-pending-commands"
   12) "0"
   13) "link-refcount"
   14) "1"
   15) "last-ping-sent"
   16) "0"
   17) "last-ok-ping-reply"
   18) "144"
   19) "last-ping-reply"
   20) "145"
   21) "down-after-milliseconds"
   22) "5000"
   23) "info-refresh"
   24) "755"
   25) "role-reported"
   26) "master"
   27) "role-reported-time"
   28) "103241"
   29) "config-epoch"
   30) "0"
   31) "num-slaves"
   32) "2"
   33) "num-other-sentinels"
   34) "2"
   35) "quorum"
   36) "2"
   37) "failover-timeout"
   38) "5000"
   39) "parallel-syncs"
   40) "1"
root@sen-demo-0:/data# exit
exit

Replace Sentinel

We are going to create a new RedisSentinel object for replacing.

apiVersion: kubedb.com/v1
kind: RedisSentinel
metadata:
  name: new-sentinel
  namespace: demo
spec:
  version: 8.2.2
  replicas: 3
  storageType: Durable
  storage:
    resources:
      requests:
        storage: 1Gi
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2026.6.19/docs/examples/redis/sentinel/new-sentinel.yaml
redissentinel.kubedb.com/new-sentinel created

Now, wait until new-sentinel has status Ready. i.e. ,

$ kubectl get redissentinel -n demo
NAME           VERSION   STATUS   AGE
new-sentinel   6.2.14     Ready    60s
sen-demo       6.2.14     Ready    11m

Here, we are going to replace sen-demo with new-sentinel

Create RedisOpsRequest

In order to replace sentinel, we have to create a RedisOpsRequest CR with our desired resources. Below is the YAML of the RedisOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: RedisOpsRequest
metadata:
  name: replace-sentinel
  namespace: demo
spec:
  type: ReplaceSentinel
  databaseRef:
    name: rd-demo
  sentinel:
    ref:
      name: new-sentinel
      namespace: demo
    removeUnusedSentinel: true

Here,

  • spec.databaseRef.name specifies that we are performing vertical scaling operation on redis database.
  • spec.type specifies that we are performing ReplaceSentinel on our database.
  • spec.sentinel.ref specifies reference of new sentinel.
  • spec.sentienl.removeUnusedSentinel specifies whether KubeDB operator should remove orphan Sentinel instance after replacing

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2026.6.19/docs/examples/redis/sentinel/replace-sentinel.yaml
redisopsrequest.ops.kubedb.com/replace-sentinel created

Verify Replacement

If everything goes well, KubeDB Enterprise operator will update the sentinel of Redis object.

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

$ kubectl get redisopsrequest -n demo 
NAME               TYPE              STATUS       AGE
replace-sentinel   ReplaceSentinel   Successful   2m34s

We can see from the above output that the RedisOpsRequest has succeeded.

Now, we are going to verify from the Pod whether the sentinel of the database has updated, Let’s check. Lets exec into one of the new-sentinel pod and verify if it is following the master. And we can additionally check if old sentinel still following the database if it exists.

$ kubectl exec -it -n demo new-sentinel-0 -c redissentinel -- bash
root@new-sentinel-0:/data# redis-cli -p 26379 sentinel masters
1)  1) "name"
    2) "demo/rd-demo"
    3) "ip"
    4) "rd-demo-0.rd-demo-pods.demo.svc"
    5) "port"
    6) "6379"
    7) "runid"
    8) "8af7fc2d42da77f92745b30c9e6bf7d2c21e3d33"
    9) "flags"
   10) "master"
   11) "link-pending-commands"
   12) "0"
   13) "link-refcount"
   14) "1"
   15) "last-ping-sent"
   16) "0"
   17) "last-ok-ping-reply"
   18) "798"
   19) "last-ping-reply"
   20) "798"
   21) "down-after-milliseconds"
   22) "5000"
   23) "info-refresh"
   24) "1350"
   25) "role-reported"
   26) "master"
   27) "role-reported-time"
   28) "240103"
   29) "config-epoch"
   30) "0"
   31) "num-slaves"
   32) "2"
   33) "num-other-sentinels"
   34) "2"
   35) "quorum"
   36) "2"
   37) "failover-timeout"
   38) "5000"
   39) "parallel-syncs"
   40) "1"
root@new-sentinel-0:/data# exit
exit

The above output verifies that we have successfully replaced sentinel of Redis database.

Cleaning up

First set termination policy to WipeOut all the things created by KubeDB operator for this Redis instance is deleted. Then delete the redis instance to clean what you created in this tutorial.

$ kubectl patch -n demo rd/rd-demo -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
redis.kubedb.com/rd-demo patched

$ kubectl delete rd rd-demo -n demo
redis.kubedb.com "rd-demo" deleted

$ kubectl delete -n demo redisopsrequest replace-sentinel
redisopsrequest.ops.kubedb.com "replace-sentinel" deleted

Now delete the RedisSentinel instance similarly.

$ kubectl patch -n demo redissentinel/sen-demo -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
redissentinel.kubedb.com/sen-demo patched

$ kubectl delete redissentinel sen-demo -n demo
redis.kubedb.com "sen-demo" deleted

$ kubectl patch -n demo redissentinel/new-sentinel -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
redissentinel.kubedb.com/new-sentinel patched

$ kubectl delete redissentinel new-sentinel -n demo
redis.kubedb.com "new-sentinel" deleted

Next Steps

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