pvc-autoscaler

pvc-autoscaler is a Kubernetes controller which periodically monitors persistent volumes and resizes them, if the available space or number of inodes drops below a certain threshold.

Requirements

• Kubernetes cluster
• Storage class with enabled volume expansion
• Metrics source (currently only Prometheus is supported)
• minikube (for local development)

Installation

There are a few ways to install pvc-autoscaler.

In order to install pvc-autoscaler within an existing Kubernetes cluster, please refer to the included dist/install.yaml bundle.

kubectl apply -f dist/install.yaml

Or you can install it this way instead.

kubectl apply -f https://raw.githubusercontent.com/gardener/pvc-autoscaler/master/dist/install.yaml

Note, that the provided install bundle uses cert-manager for issuing TLS certificates for the admission webhook server. If you intend on using another approach for issuing TLS certificates, make sure to adjust the default kustomization instead.

In addition to that you could also install pvc-autoscaler using the default kustomization located in config/default. Note that the default kustomization is meant to be used in dev setups. For non-dev setups it is recommended that you create an overlay using the default kustomization as a base.

kustomize build config/default | kubectl apply -f -

pvc-autoscaler uses Prometheus as a metrics source in order to monitor the persistent volumes usage. By default it will use the http://prometheus-k8s.monitoring.svc.cluster.local:9090 endpoint.

If your Prometheus instance is running at a different endpoint, make sure that you configure the --prometheus-address option for the pvc-autoscaler-controller-manager deployment.

Usage

In order to start monitoring and automatically resize a persistent volume, when the available space or inodes drop below a certain threshold you need to create a new PersistentVolumeClaimAutoscaler resource, e.g.

---
apiVersion: autoscaling.gardener.cloud/v1alpha1
kind: PersistentVolumeClaimAutoscaler
metadata:
  name: my-pvca
spec:
  increaseBy: "10%"
  threshold: "20%"
  maxCapacity: 10Gi
  scaleTargetRef:
    name: my-pvc

The following properties must be specified when creating a new PersistentVolumeClaimAutoscaler resource.

Property	Description	Default
.spec.increaseBy	Specifies how much to increase the PVC in percentage during resize	10%
.spec.threshold	Specify the threshold in percentage, which once reached will cause a resize	10%
.spec.maxCapacity	Max capacity up to which a PVC can be resized	N/A
.spec.scaleTargetRef.name	Name of the PVC to monitor and autoscale	N/A

In order to watch the status of the autoscaler you can kubectl describe your PersistentVolumeClaimAutoscaler resource, where you will find information about the latest observed state, last and next scheduled check, status conditions, etc.

Local development

The local environment of pvc-autoscaler uses minikube for bootstrapping a dev Kubernetes cluster.

In order to start a new local environment execute the following command.

make minukube-start

The command above will install OpenEBS, the LVM-LocalPV CSI driver and configure the openebs-lvm storage class with volume expansion support.

Along with that it also installs kube-prometheus, which provides Prometheus, Grafana and Alert Manager.

By default the minikube profile will be named pvc-autoscaler, which can be configured via the MINIKUBE_PROFILE env variable, e.g.

MINIKUBE_PROFILE=my-dev-env make minikube-start

The default minikube driver is set to qemu, which can be configured via the MINIKUBE_DRIVER env variable.

For example, if you are on GNU/Linux and have KVM you would set the driver to kvm2, e.g.

MINIKUBE_DRIVER=kvm2 make minikube-start

In order to build and load an image of pvc-autoscaler into your minikube nodes execute the following command.

make minikube-load-image

The following command will deploy pvc-autoscaler in the cluster.

make deploy

If you want to run pvc-autoscaler outside of the Kubernetes cluster you can run this command instead.

make run

When done with the local environment you can delete it using the following command.

make minikube-stop

Also, make sure to check the help information about each Makefile target by executing this command.

make help

Tests

Run the unit tests.

make test

In order to run the end-to-end tests we need a clean test environment. The following command will create a new test environment, build and deploy the operator image, run the e2e tests against it and finally destroy the test environment.

make test-e2e

If you need to create a clean environment for e2e tests and run the tests manually, then you can run the following command which will setup the test environment, load the Docker images into the minikube nodes and deploy the operator in the cluster.

make e2e-env-setup

Then you can manually run the e2e tests by executing the following script.

./hack/run-e2e-tests.sh

In order to remove the test e2e environment execute the following.

make e2e-env-teardown

Contributing

pvc-autoscaler is hosted on Github. Please contribute by reporting issues, suggesting features or by sending patches using pull requests.

License

This project is Open Source and licensed under Apache License 2.0.