[Feature]: Support for Setting Tenant Variables via ObTenant CR in ob-operator

[qchenzi]

In OceanBase, users often modify tenant variables by executing SET commands within the tenant environment. Currently, the ob-operator does not support setting these tenant variables directly in the ObTenant Custom Resource (CR). This limitation means that users cannot leverage the ob-operator's reconciliation functions to manage and apply tenant variable changes automatically. For instance, to modify the sql_mode variable for a tenant, users must manually execute the command, rather than specifying it in the ObTenant CR.

Proposal:

Add support in ob-operator to allow users to specify tenant variables directly within the ObTenant CR. The ob-operator should detect these specifications and reconcile the tenant's variables accordingly, applying any changes automatically.

Use Case:

A user wants to set the sql_mode variable for a tenant. Instead of logging into the tenant and executing:

SET sql_mode = 'STRICT_TRANS_TABLES';

the user can specify this variable in the ObTenant CR:

apiVersion: oceanbase.com/v1
kind: ObTenant
metadata:
  name: my-tenant
spec:
  variables:
    sql_mode: 'STRICT_TRANS_TABLES'

The ob-operator would detect this change and apply the variable to the tenant automatically during the reconciliation process.

Conclusion: Implementing this feature would enhance the ob-operator's functionality by allowing users to manage tenant variables declaratively. It would align the operator more closely with Kubernetes principles of declarative configuration and automation, improving the overall user experience.