Perform a Canary Upgrade on TiDB Operator

Perform a Canary Upgrade on TiDB Operator

If you want to upgrade TiDB Operator to a new version, and hope to limit the impact of the upgrade to avoid the unpredictable impact on all TiDB clusters in the entire Kubernetes cluster, you can perform a canary upgrade on TiDB Operator. After the canary upgrade, you can check the impact of the TiDB Operator upgrade on the canary cluster. After you confirm that the new version of TiDB Operator is working stably, you can then upgrade TiDB Operator normally.

You can perform a canary upgrade only on two components: tidb-controller-manager and tidb-scheduler. Canary upgrades for the advanced StatefulSet controller and the admission controller are not supported.

When you use TiDB Operator, tidb-scheduler is not mandatory. Refer to tidb-scheduler and default-scheduler to confirm whether you need to deploy tidb-scheduler.

Step 1: Configure selector for the current TiDB Operator and perform an upgrade

In values.yaml of the current TiDB Operator, add the following selector configuration:

controllerManager:
  selector:
  - version!=canary

Refer to Online upgrade or Offline upgrade to upgrade the current TiDB Operator:

helm upgrade tidb-operator pingcap/tidb-operator --version=${chart_version} -f ${HOME}/tidb-operator/values-tidb-operator.yaml

Step 2: Deploy the canary TiDB Operator

Refer to Step 1~2 in Online deployment and obtain the values.yaml file of the version you want to upgrade to. Add the following configuration in values.yaml:
```
controllerManager:
  selector:
  - version=canary
appendReleaseSuffix: true
#scheduler:
#  create: false # If you do not need tidb-scheduler, set this value to false.
advancedStatefulset:
  create: false
admissionWebhook:
  create: false
```
appendReleaseSuffix must be set to true.

If you do not need to perform a canary upgrade on tidb-scheduler, configure scheduler.create: false. If you need to perform a canary upgrade on tidb-scheduler, configuring scheduler.create: true creates a scheduler named {{ .scheduler.schedulerName }}-{{.Release.Name}}. To use this scheduler in the canary TiDB Operator, in the TidbCluster CR, configure spec.schedulerName to the name of this scheduler.

Because canary upgrades for the advanced StatefulSet controller and the admission controller are not supported, you need to set advancedStatefulset.create: false and admissionWebhook.create: false.

For details on the parameters related to canary upgrade, refer to related parameters.
Deploy the canary TiDB Operator in a different namespace (such as tidb-admin-canary) with a different Helm Release name (such as helm install tidb-operator-canary ...):
```
helm install tidb-operator-canary pingcap/tidb-operator --namespace=tidb-admin-canary --version=${operator_version} -f ${HOME}/tidb-operator/${operator_version}/values-tidb-operator.yaml
```
Replace ${operator_version} with the version of TiDB Operator you want to upgrade to.

Step 3: Test the canary TiDB Operator (optional)

Before you upgrade TiDB Operator in a normal way, you can test whether the canary TiDB Operator works stably. You can test tidb-controller-manager and tidb-scheduler.

To test the canary tidb-controller-manager, set a label for a TiDB cluster by running the following command:
```
kubectl -n ${namespace} label tc ${cluster_name} version=canary
```
Check the logs of the two deployed tidb-controller-managers, and you can see this TiDB cluster with the canary label is now managed by the canary TiDB Operator. The steps to check logs are as follows:
1. View the log of tidb-controller-manager of the current TiDB Operator:
```
kubectl -n tidb-admin logs tidb-controller-manager-55b887bdc9-lzdwv
```
  Expected output:
```
I0305 07:52:04.558973       1 tidb_cluster_controller.go:148] TidbCluster has been deleted tidb-cluster-1/basic1
```
2. View the log of tidb-controller-manager of the canary TiDB Operator:
```
kubectl -n tidb-admin-canary logs tidb-controller-manager-canary-6dcb9bdd95-qf4qr
```
  Expected output:
```
I0113 03:38:43.859387       1 tidbcluster_control.go:69] TidbCluster: [tidb-cluster-1/basic1] updated successfully
```
To test the canary upgrade of tidb-scheduler, modify spec.schedulerName of a TiDB cluster to tidb-scheduler-canary by running the following command:
```
kubectl -n ${namespace} edit tc ${cluster_name}
```
After the modification, all components in the cluster will be rolling updated.

Check the logs of tidb-scheduler of the canary TiDB Operator, and you can see this TiDB cluster is now using the canary tidb-scheduler:
```
kubectl -n tidb-admin-canary logs tidb-scheduler-canary-7f7b6c7c6-j5p2j -c tidb-scheduler
```
After the tests, you can revert the changes in the previous two steps so that the TiDB cluster is again managed by the current TiDB Operator.
```
kubectl -n ${namespace} label tc ${cluster_name} version-
```
```
kubectl -n ${namespace} edit tc ${cluster_name}
```

Step 4: Upgrade TiDB Operator normally

After you confirm that the canary TiDB Operator works stably, you can upgrade the TiDB Operator normally.

Delete the canary TiDB Operator:

helm -n tidb-admin-canary uninstall ${release_name}

Upgrade TiDB Operator normally.