Upgrade SSTables

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Run this operation when the server version is upgraded or when changing compression options. If the SSTables are already on the current version, the command returns immediately and no action is taken. To run the nodetool upgradesstables operation, modify and submit the upgradesstables CassandraTask manifest (object).

Performance impact

While this task is running additional disk pressure occurs as all SSTables are rewritten to the correct format (if required). Upon completion of the SSTable format upgrade the read performance is improved.

Prerequisites

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

Example

A single datacenter deployed in the Data Plane Kubernetes cluster.

Workflow of user and operators

User defines a upgradesstables CassandraTask.
User submits an upgradesstables CassandraTask with kubectl to the Data Plane Kubernetes cluster where the datacenter is deployed.
DC-operator detects new task custom resource definition (CRD).
DC-operator iterates one rack at a time.
DC-operator triggers and monitors replacement operations one pod at a time.
DC-operator reports task progress and status.
User requests a status report of the replace-node CassandraTask with the kubectl command, and views the status response.

Procedure

Modify the demo-dse.cassandratask.yaml file to define an upgradesstables CassandraTask.

Here is a sample:
```
apiVersion: control.k8ssandra.io/v1alpha1
kind: CassandraTask
metadata:
  name: upgradesstables-dc1
spec:
  datacenter:
    name: dc1
    namespace: demo
  jobs:
    - name: upgradesstables-dc1
      command: upgradesstables
      args:
        keyspace_name: my_keyspace
```
Key options:
- metadata.name: a unique identifer within the Kubernetes namespace where the task is submitted. While the name can be any value, consider including the cluster name to prevent collision with other options.
- spec.datacenter: a unique namespace and name combination used to determine which datacenter to target with this operation
- spec.jobs[0].command: MUST be `upgradesstables for this operation
- Optional: spec.jobs[0].args.keyspace_name: restricts this operation to a particular keyspace. Omitting this value results in ALL keyspaces being updated. By default all keyspaces are rebuilt.
Submit the upgradesstables CassandraTask custom resource definition to the Control Plane Kubernetes cluster with this command:
```
kubectl apply -f demo-dse.casssandratask.yaml -n mission-control
```
Use the -n flag to indicate the Kubernetes namespace, which MUST be mission-control.

Submit the rebuild CassandraTask object to the Kubernetes cluster where the specified datacenter is deployed.

Sample output:
```
...
status:
  completionTime: "2022-10-20T18:07:08Z"
  conditions:
  - lastTransitionTime: "2022-10-20T18:06:57Z"
    status: "True"
    type: Running
  - lastTransitionTime: "2022-10-20T18:07:08Z"
    status: "True"
    type: Complete
  startTime: "2022-10-20T18:06:57Z"
  succeeded: 3
```
DC-level operators set the startTime field prior to starting the upgradesstables operation. They update the completionTime field when the upgradesstables operation is completed.

The sample output indicates that the task is completed with the type: Complete status condition set to True. The succeeded: 3 field indicates that three (3) nodes (or pods) completed the requested task successfully. A failed field tracks a running count of pods that failed the upgradesstables operation.

Monitor the SSTables upgrade progress with this command:

kubectl get cassandratask upgradesstables-dc1 | yq .status