Upgrading a DataStax Enterprise Cluster With Zero Downtime

DataStax Mission Control is current in Private Preview. It is subject to the beta agreement executed between you and DataStax. DataStax Mission Control is not intended for production use, has not been certified for production workloads, and might contain bugs and other functional issues. There is no guarantee that DataStax Mission Control will ever become generally available. DataStax Mission Control is provided on an “AS IS” basis, without warranty or indemnity of any kind.

If you are interested in trying out DataStax Mission Control please contact your DataStax account team.

Apply and deploy a new version of DataStax Enterprise to an existing cluster. Modify the DSECluster manifest, updating the DSE version from 6.8.25 to 6.8.26.

Prerequisites

The kubectl CLI tool.
Kubeconfig file` or context pointing to a Control Plane Kubernetes cluster.

Example

The existing deployment consists of 1 datacenter (dc1) with 3 nodes, each node on a separate rack.

Workflow of user and operators

User submits a modified DSECluster manifest to the Control Plane Kubernetes cluster.
Cluster-level operator detects the change and modifies the datacenter-level resource.
Datacenter-level operator detects the change and modifies the rack-level resource.
Datacenter-level operator terminates the instance in the rack.
Datacenter-level operator bootstraps a replacement node.
Datacenter-level operator repeats steps c-e for all racks in one datacenter.
Cluster-level operator repeats steps b-e for all datacenters in a cluster, one dc at a time, in the case of a multi-datacenter cluster.
User follows Upgrade SSTables steps, if required.

Upgrades of DataStax Enterprise versions follow the same process as configuration change deployments. See Deploying Configuration Changes to a DataStax Enterprise Cluster.

Procedure

Modify the existing DSECluster YAML (demo-dse.yaml) in the Control Plane Kubernetes cluster, overwriting the value 6.8.25 in the spec.serverVersion field with 6.8.26:
```
apiVersion: missioncontrol.datastax.com/v1alpha1
kind: DSECluster
metadata:
  name: demo
spec:
  serverVersion: 6.8.26
...
```
Submit the version change to the Kubernetes Control Plane cluster with the following command:
```
kubectl apply -f demo-dse.yaml
```
The DSE version upgrade is done as a rolling update.
Monitor the progress of the upgrade from the Data Plane east cluster, looking at the status of the CassandraDatacenter with this command:
```
kubectl get cassandradatacenter dc1 -o yaml
```
Here is a partial sample of the results:
```
status:
  cassandraOperatorProgress: Updating
  conditions:
  - lastTransitionTime: "2022-10-20T16:07:10Z"
    message: ""
    reason: ""
    status: "True"
    type: Healthy
  - lastTransitionTime: "2022-10-20T16:07:10Z"
    message: ""
    reason: ""
    status: "False"
    type: Stopped
...
```
The Updating conditions:status field value of "True" indicates that the update is in progress. Upon completion of the Updating operation, the Cass-Operator changes the Updating conditions:status field value to "False".

What’s next

Users may trigger an Upgrade SSTables operation to rewrite SSTables into newer formats, if required.