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ClickHouse Horizontal Scaling
This guide will give an overview on how KubeDB Ops-manager operator scales up or down ClickHouse
cluster replicas of various component such as Combined, Broker, Controller.
Before You Begin
- You should be familiar with the following
KubeDB
concepts:
How Horizontal Scaling Process Works
The following diagram shows how KubeDB Ops-manager operator scales up or down ClickHouse
database components. Open the image in a new tab to see the enlarged version.
The Horizontal scaling process consists of the following steps:
At first, a user creates a
ClickHouse
Custom Resource (CR).KubeDB
Provisioner operator watches theClickHouse
CR.When the operator finds a
ClickHouse
CR, it creates required number ofPetSets
and related necessary stuff like secrets, services, etc.Then, in order to scale the various components (ie. ReplicaSet, Shard, ConfigServer etc.) of the
ClickHouse
cluster, the user creates aClickHouseOpsRequest
CR with desired information.KubeDB
Ops-manager operator watches theClickHouseOpsRequest
CR.When it finds a
ClickHouseOpsRequest
CR, it halts theClickHouse
object which is referred from theClickHouseOpsRequest
. So, theKubeDB
Provisioner operator doesn’t perform any operations on theClickHouse
object during the horizontal scaling process.Then the
KubeDB
Ops-manager operator will scale the related PetSet Pods to reach the expected number of replicas defined in theClickHouseOpsRequest
CR.After the successfully scaling the replicas of the related PetSet Pods, the
KubeDB
Ops-manager operator updates the number of replicas in theClickHouse
object to reflect the updated state.After the successful scaling of the
ClickHouse
replicas, theKubeDB
Ops-manager operator resumes theClickHouse
object so that theKubeDB
Provisioner operator resumes its usual operations.
In the next docs, we are going to show a step by step guide on horizontal scaling of ClickHouse cluster using ClickHouseOpsRequest
CRD.