New to KubeDB? Please start here.
Horizontal Scale Redis Cluster With Horizon DNS
This guide will give an overview on how KubeDB Ops-manager operator scales up or down Redis database shards and replicas Redis in Cluster mode which are running with Announces.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectlcommand-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
KubeDBCommunity and Enterprise operator in your cluster following the steps here.You should be familiar with the following
KubeDBconcepts:
Apply Horizontal Scaling on Cluster
Here, we are going to deploy a Redis/Valkey cluster using a supported version by KubeDB operator. Then we are going to apply horizontal scaling on it.
Prepare Redis Cluster Database
Deploy Redis/Valkey cluster as shown in External Connection Exposer.
After it gets Ready check the number of shards and replicas this database has from the Redis object
$ kubectl get redis -n demo redis-announce -o json | jq '.spec.cluster.shards'
3
$ kubectl get redis -n demo redis-announce -o json | jq '.spec.cluster.replicas'
2
Now let’s connect to redis-cluster using redis-cli and verify master and replica count of the cluster
$ kubectl exec -it -n demo redis-announce-shard0-0 -c redis -- redis-cli -c cluster nodes | grep master
fc7c635c745b8c74c4422300e945eadb4251add6 10.2.0.87:10050@10056,rd0-0.kubedb.appscode myself,master - 0 1754481552000 1 connected 0-5460
e45749edaf324b980bbf5148644d500d6842ff5c 10.2.0.87:10054@10060,rd0-0.kubedb.appscode master - 0 1754481555065 3 connected 10923-16383
673060b3b589f06fe6a12e6f47ea8910042b6be6 10.2.0.87:10052@10058,rd0-0.kubedb.appscode master - 0 1754481555000 2 connected 5461-10922
$ kubectl exec -it -n demo redis-cluster-shard0-0 -c redis -- redis-cli -c cluster nodes | grep slave | wc -l
3
We can see from above output that there are 3 masters and each master has 2 replicas. So, total 6 replicas in the cluster. Each master and its two replicas belongs to a shard.
We are now ready to apply the RedisOpsRequest CR to update the resources of this database.
Horizontal Scaling
Here, we are going to scale up the shards and replicas of the redis cluster to meet the desired resources after scaling.
Create RedisOpsRequest
In order to scale up the shards and replicas of the redis cluster, we have to create a RedisOpsRequest CR with our desired number of shards and replicas and with desired FQDN. Below is the YAML of the RedisOpsRequest CR that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: RedisOpsRequest
metadata:
name: redisops-horizontal-external
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: redis-announce
horizontalScaling:
replicas: 3
shards: 4
announce:
shards:
- endpoints:
- rd0-0.kubedb.appscode
- endpoints:
- rd0-0.kubedb.appscode
- endpoints:
- rd0-0.kubedb.appscode
- endpoints:
- rd0-0.kubedb.appscode
- rd0-0.kubedb.appscode
- rd0-0.kubedb.appscode
Here,
spec.databaseRef.namespecifies that we are performing horizontal scaling operation onredis-announcedatabase.spec.typespecifies that we are performingHorizontalScalingon our database.spec.horizontalScaling.shardsspecifies the desired number of shards after scaling.spec.horizontalScaling.replicasspecifies the desired number of replicas after scaling.spec.horizontalScaling.announce.shardsspecifies endpoints for newly created replicas and shards. As we have two replicas in the first shard, and we will increase it by one and make it 3, we have added one FQDN for this.
Let’s create the RedisOpsRequest CR we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2025.7.31/docs/examples/redis/scaling/horizontal-scaling/horizontal-cluster.yaml
redisopsrequest.ops.kubedb.com/redisops-horizontal-external created
Verify Redis Cluster resources updated successfully
If everything goes well, KubeDB Enterprise operator will update the replicas and shards of Redis object and related PetSets.
Note: Newly created pod will be started with the Governing Service DNS and will wait for anotherannounceOpsRequest
Let’s wait for RedisOpsRequest to be Successful. Run the following command to watch RedisOpsRequest CR,
$ watch kubectl get redisopsrequest -n demo redisops-horizontal
NAME TYPE STATUS AGE
redisops-horizontal-external HorizontalScaling Successful 3m8s
Now, we are going to verify if the number of shards and replicas the redis cluster has updated to meet up the desired state, Let’s check,
$ kubectl get redis -n demo redis-anounce -o json | jq '.spec.cluster.shards'
4
$ kubectl get redis -n demo redis-anounce -o json | jq '.spec.cluster.replicas'
3
Let’s wait for the new Announce opsRequest to be created and Successful
$ watch kubectl get rdops -n demo
NAME TYPE STATUS AGE
rd-at86h7 Announce Successful 2m
redisops-horizontal-external HorizontalScaling Successful 4m
Now let’s connect to redis-anounce using redis-cli and verify master and replica count of the cluster
$ kubectl exec -it -n demo redis-anounce-shard0-0 -c redis -- redis-cli -c cluster nodes | grep master
fc7c635c745b8c74c4422300e945eadb4251add6 10.2.0.87:10050@10056,rd0-0.kubedb.appscode myself,master - 0 1754484135000 1 connected 1365-5460
039d9b38874ee6dca807836646bbdc8b25f544d5 10.2.0.87:10065@10071,rd0-0.kubedb.appscode master - 0 1754484137945 4 connected 0-1364 5461-6826 10923-12287
e45749edaf324b980bbf5148644d500d6842ff5c 10.2.0.87:10054@10060,rd0-0.kubedb.appscode master - 0 1754484137000 3 connected 12288-16383
673060b3b589f06fe6a12e6f47ea8910042b6be6 10.2.0.87:10052@10058,rd0-0.kubedb.appscode master - 0 1754484136539 2 connected 6827-10922
$ kubectl exec -it -n demo redis-cluster-shard0-0 -c redis -- redis-cli -c cluster nodes | grep slave | wc -l
8
The above output verifies that we have successfully scaled up the shards and scaled down the replicas of the Redis cluster database. The slots in redis shard is also distributed among 4 master.
Cleaning up
To clean up the Kubernetes resources created by this tutorial, run:
$ kubectl patch -n demo rd/redis-announce -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
redis.kubedb.com/redis-announce patched
$ kubectl delete -n demo redis redis-announce
redis.kubedb.com "redis-announce" deleted
$ kubectl delete -n demo redisopsrequest redisops-horizontal-external rd-at86h7
redisopsrequest.ops.kubedb.com "redisops-horizontal-external" deleted
redisopsrequest.ops.kubedb.com "rd-at86h7" deleted