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Cassandra Horizontal Scaling

This guide will give an overview on how KubeDB Ops-manager operator scales up or down Cassandra cluster replicas of various component such as Combined, Broker, Controller.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • Cassandra
  • CassandraOpsRequest

How Horizontal Scaling Process Works

The following diagram shows how KubeDB Ops-manager operator scales up or down Cassandra database components. Open the image in a new tab to see the enlarged version.

  

The Horizontal scaling process consists of the following steps:

1. At first, a user creates a Cassandra Custom Resource (CR).

2. KubeDB Provisioner operator watches the Cassandra CR.

3. When the operator finds a Cassandra CR, it creates required number of PetSets and related necessary stuff like secrets, services, etc.

4. Then, in order to scale the various components (ie. ReplicaSet, Shard, ConfigServer, Mongos, etc.) of the Cassandra cluster, the user creates a CassandraOpsRequest CR with desired information.

5. KubeDB Ops-manager operator watches the CassandraOpsRequest CR.

6. When it finds a CassandraOpsRequest CR, it halts the Cassandra object which is referred from the CassandraOpsRequest. So, the KubeDB Provisioner operator doesn’t perform any operations on the Cassandra object during the horizontal scaling process.

7. Then the KubeDB Ops-manager operator will scale the related PetSet Pods to reach the expected number of replicas defined in the CassandraOpsRequest CR.

8. After the successfully scaling the replicas of the related PetSet Pods, the KubeDB Ops-manager operator updates the number of replicas in the Cassandra object to reflect the updated state.

9. After the successful scaling of the Cassandra replicas, the KubeDB Ops-manager operator resumes the Cassandra object so that the KubeDB Provisioner operator resumes its usual operations.

In the next docs, we are going to show a step by step guide on horizontal scaling of Cassandra cluster using CassandraOpsRequest CRD.