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MongoDB Volume Expansion

This guide will give an overview on how KubeDB Ops-manager operator expand the volume of various component of MongoDB such as ReplicaSet, Shard, ConfigServer, Mongos, etc.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • MongoDB
  • MongoDBOpsRequest

How Volume Expansion Process Works

The following diagram shows how KubeDB Ops-manager operator expand the volumes of MongoDB database components. Open the image in a new tab to see the enlarged version.

  

The Volume Expansion process consists of the following steps:

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

2. KubeDB Provisioner operator watches the MongoDB CR.

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

4. Each StatefulSet creates a Persistent Volume according to the Volume Claim Template provided in the statefulset configuration. This Persistent Volume will be expanded by the KubeDB Ops-manager operator.

5. Then, in order to expand the volume of the various components (ie. ReplicaSet, Shard, ConfigServer, Mongos, etc.) of the MongoDB database the user creates a MongoDBOpsRequest CR with desired information.

6. KubeDB Ops-manager operator watches the MongoDBOpsRequest CR.

7. When it finds a MongoDBOpsRequest CR, it halts the MongoDB object which is referred from the MongoDBOpsRequest. So, the KubeDB Provisioner operator doesn’t perform any operations on the MongoDB object during the volume expansion process.

8. Then the KubeDB Ops-manager operator will expand the persistent volume to reach the expected size defined in the MongoDBOpsRequest CR.

9. After the successfully expansion of the volume of the related StatefulSet Pods, the KubeDB Ops-manager operator updates the new volume size in the MongoDB object to reflect the updated state.

10. After the successful Volume Expansion of the MongoDB components, the KubeDB Ops-manager operator resumes the MongoDB 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 Volume Expansion of various MongoDB database components using MongoDBOpsRequest CRD.