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Horizontal Scaling Overview
This guide will give you an overview of how KubeDB
Ops Manager scales up/down the number of members of a Postgres
instance.
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 used to scale up the number of members of a Postgres
cluster. Open the image in a new tab to see the enlarged version.
![Horizontal scaling Flow](/docs/v2024.4.27/guides/postgres/scaling/horizontal-scaling/overview/images/pg-horizontal-scaling.png)
The horizontal scaling process consists of the following steps:
At first, a user creates a
Postgres
cr.KubeDB
community operator watches for thePostgres
cr.When it finds one, it creates a
StatefulSet
and related necessary stuff like secret, service, etc.Then, in order to scale the cluster, the user creates a
PostgresOpsRequest
cr with the desired number of members after scaling.KubeDB
Ops Manager watches forPostgresOpsRequest
.When it finds one, it halts the
Postgres
object so that theKubeDB
community operator doesn’t perform any operation on thePostgres
during the scaling process.Then
KubeDB
Ops Manager will add nodes in case of scale up or remove nodes in case of scale down.Then the
KubeDB
Ops Manager will scale the StatefulSet replicas to reach the expected number of replicas for the cluster.After successful scaling of the StatefulSet’s replica, the
KubeDB
Ops Manager updates thespec.replicas
field ofPostgres
object to reflect the updated cluster state.After successful scaling of the
Postgres
replicas, theKubeDB
Ops Manager resumes thePostgres
object so that theKubeDB
community operator can resume its usual operations.
In the next doc, we are going to show a step by step guide on scaling of a Postgres cluster using Horizontal Scaling.