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https://github.com/vshn/statefulset-resize-controller
Kubernetes Operator to enable StatefulSet resizing, independent of the underlying cloud.
https://github.com/vshn/statefulset-resize-controller
vshn-project-appcat vshn-team-schedar
Last synced: 28 days ago
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Kubernetes Operator to enable StatefulSet resizing, independent of the underlying cloud.
- Host: GitHub
- URL: https://github.com/vshn/statefulset-resize-controller
- Owner: vshn
- License: bsd-3-clause
- Created: 2021-07-12T08:17:39.000Z (over 3 years ago)
- Default Branch: master
- Last Pushed: 2024-05-22T16:00:24.000Z (7 months ago)
- Last Synced: 2024-05-22T17:26:17.647Z (7 months ago)
- Topics: vshn-project-appcat, vshn-team-schedar
- Language: Go
- Homepage:
- Size: 188 KB
- Stars: 4
- Watchers: 6
- Forks: 1
- Open Issues: 15
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
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# Statefulset Resize Controller
The Statefulset Resize Controller is a Kubernetes operator to enable resizing PVCs of Statefulsets.
## Concept
Statefulsets have the option to provide one or more `volumeClaimTemplates`.
For each of these `volumeClaimTemplates` k8s will create a persistent volume claim per pod.
What Statefulsets do not support however, is updating these `volumeClaimTemplates`.
Depending on the storage backends, PVCs are not mutable either and different features might or might not be available.
This means increasing the storage size of a Statefulset involves quite a lot of manual steps.
The Statefulset Resize Controller is general solution to this problem and does not require any additional support from the storage backend.
When recreating a Statefulset using `--cascade=orphan`, the controller will notice the change, scale down the Statefulset, recreate the PVCs, and migrate the data.
### Controller command line arguments
* `--sync-image`: A container image containing rsync, used to move data.
Default `instrumentisto/rsync-ssh`.
* `--sync-cluster-role`: A ClusterRole to use for the sync jobs.
If this is not specified, the sync jobs run with the default service account in the StatefulSet's namespace.
For example, this can be used to allow the sync job to run as root on a cluster with PSPs enabled by providing the name of a ClusterRole which allows usage of a privileged PSP.
Default `""`.
* `--metrics-bind-address`: The address the metric endpoint binds to.
Default `:8080`.
* `--health-probe-bind-address`: The address the probe endpoint binds to.
Default `:8081`.
* `--leader-elect`: Enable leader election for controller manager.
Enabling this will ensure there is only one active controller manager.
Default `false`.
### Example
Get access to a Kubernetes cluster that has support for automatic PV provisioning.
Start the controller with:
```
make run
```
Create a Statefulset using a `1G` volume, by applying:
```yaml
apiVersion: v1
kind: Service
metadata:
name: nginx
labels:
app: nginx
spec:
ports:
- port: 80
name: web
clusterIP: None
selector:
app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: web
spec:
selector:
matchLabels:
app: nginx
serviceName: "nginx"
replicas: 3
template:
metadata:
labels:
app: nginx
spec:
terminationGracePeriodSeconds: 10
containers:
- name: nginx
image: k8s.gcr.io/nginx-slim:0.8
ports:
- containerPort: 80
name: web
volumeMounts:
- name: www
mountPath: /usr/share/nginx/html
volumeClaimTemplates:
- metadata:
name: www
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 1Gi
```
Make sure the StatefulSet starts up successfully.
At this point you can write something to one of the volumes, the data will be persistent through the update.
To initiate the resizing, remove the StatefulSet without touching the pods by running:
```
kubectl delete sts web --cascade=orphan
```
Now increase the requested storage to `2G` and reapply the StatefulSet.
You should see the StatefulSet being scaled down to 0.
Then a backup of the volumes will be created, and the PVCs will be recreated and restored.
After a few seconds the StatefulSet should scale back up and its PVCs should be resized.
## Contributing
The Statefulset Resize Controller is written using the [Operator SDK](https://sdk.operatorframework.io/docs).
You'll need:
- A running Kubernetes cluster (minishift, minikube, k3s, ... you name it)
- [kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/) and [kustomize](https://kubernetes-sigs.github.io/kustomize/installation/)
- Go development environment
- Your favorite IDE (with a Go plugin)
- Docker
- make
These are the most common make targets: `build`, `test`, `run`.
Run `make help` to get an overview over the relevant targets and their intentions.