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Upgrading MongoDB version Overview

This guide will give you an overview on how KubeDB Enterprise operator upgrade the version of MongoDB database.

Before You Begin

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

How Upgrade Process Works

The following diagram shows how KubeDB Enterprise operator used to upgrade the version of MongoDB. Open the image in a new tab to see the enlarged version.

  

The upgrading process consists of the following steps:

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

2. KubeDB Community 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. Then, in order to upgrade the version of the MongoDB database the user creates a MongoDBOpsRequest CR with the desired version.

5. KubeDB Enterprise operator watches the MongoDBOpsRequest CR.

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

7. By looking at the target version from MongoDBOpsRequest CR, KubeDB Enterprise operator updates the images of all the StatefulSets. After each image update, the operator performs some checks such as if the oplog is synced and database size is almost same or not.

8. After successfully updating the StatefulSets and their Pods images, the KubeDB Enterprise operator updates the image of the MongoDB object to reflect the updated state of the database.

9. After successfully updating of MongoDB object, the KubeDB Enterprise operator resumes the MongoDB object so that the KubeDB Community operator can resume its usual operations.

In the next doc, we are going to show a step by step guide on upgrading of a MongoDB database using upgrade operation.