v1.24 blog post: Volume populators beta
Ben Swartzlander
parent
132fece161
commit
e7089f9c40
|
|
@ -0,0 +1,162 @@
|
||||||
|
---
|
||||||
|
layout: blog
|
||||||
|
title: "Kubernetes 1.24: Volume Populators Graduate to Beta"
|
||||||
|
date: 2022-05-16
|
||||||
|
slug: volume-populators-beta
|
||||||
|
---
|
||||||
|
|
||||||
|
**Author:**
|
||||||
|
Ben Swartzlander (NetApp)
|
||||||
|
|
||||||
|
The volume populators feature is now two releases old and entering beta! The `AnyVolumeDataSouce` feature
|
||||||
|
gate defaults to enabled in Kubernetes v1.24, which means that users can specify any custom resource
|
||||||
|
as the data source of a PVC.
|
||||||
|
|
||||||
|
An [earlier blog article](/blog/2021/08/30-volume-populators-redesigned/) detailed how the
|
||||||
|
volume populators feature works. In short, a cluster administrator can install a CRD and
|
||||||
|
associated populator controller in the cluster, and any user who can create instances of
|
||||||
|
the CR can create pre-populated volumes by taking advantage of the populator.
|
||||||
|
|
||||||
|
Multiple populators can be installed side by side for different purposes. The SIG storage
|
||||||
|
community is already seeing some implementations in public, and more prototypes should
|
||||||
|
appear soon.
|
||||||
|
|
||||||
|
Cluster administrations are **strongly encouraged** to install the
|
||||||
|
volume-data-source-validator controller and associated `VolumePopulator` CRD before installing
|
||||||
|
any populators so that users can get feedback about invalid PVC data sources.
|
||||||
|
|
||||||
|
## New Features
|
||||||
|
|
||||||
|
The [lib-volume-populator](https://github.com/kubernetes-csi/lib-volume-populator) library
|
||||||
|
on which populators are built now includes metrics to help operators monitor and detect
|
||||||
|
problems. This library is now beta and latest release is v1.0.1.
|
||||||
|
|
||||||
|
The [volume data source validator](https://github.com/kubernetes-csi/volume-data-source-validator)
|
||||||
|
controller also has metrics support added, and is in beta. The `VolumePopulator` CRD is
|
||||||
|
beta and the latest release is v1.0.1.
|
||||||
|
|
||||||
|
## Trying it out
|
||||||
|
|
||||||
|
To see how this works, you can install the sample "hello" populator and try it
|
||||||
|
out.
|
||||||
|
|
||||||
|
First install the volume-data-source-validator controller.
|
||||||
|
|
||||||
|
```shell
|
||||||
|
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/volume-data-source-validator/v1.0.1/client/config/crd/populator.storage.k8s.io_volumepopulators.yaml
|
||||||
|
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/volume-data-source-validator/v1.0.1/deploy/kubernetes/rbac-data-source-validator.yaml
|
||||||
|
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/volume-data-source-validator/v1.0.1/deploy/kubernetes/setup-data-source-validator.yaml
|
||||||
|
```
|
||||||
|
|
||||||
|
Next install the example populator.
|
||||||
|
|
||||||
|
```shell
|
||||||
|
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/lib-volume-populator/v1.0.1/example/hello-populator/crd.yaml
|
||||||
|
kubectl apply -f https://raw.githubusercontent.com/kubernetes-csi/lib-volume-populator/87a47467b86052819e9ad13d15036d65b9a32fbb/example/hello-populator/deploy.yaml
|
||||||
|
```
|
||||||
|
|
||||||
|
Your cluster now has a new CustomResourceDefinition that provides a test API named Hello.
|
||||||
|
Create an instance of the `Hello` custom resource, with some text:
|
||||||
|
|
||||||
|
```yaml
|
||||||
|
apiVersion: hello.example.com/v1alpha1
|
||||||
|
kind: Hello
|
||||||
|
metadata:
|
||||||
|
name: example-hello
|
||||||
|
spec:
|
||||||
|
fileName: example.txt
|
||||||
|
fileContents: Hello, world!
|
||||||
|
```
|
||||||
|
|
||||||
|
Create a PVC that refers to that CR as its data source.
|
||||||
|
|
||||||
|
```yaml
|
||||||
|
apiVersion: v1
|
||||||
|
kind: PersistentVolumeClaim
|
||||||
|
metadata:
|
||||||
|
name: example-pvc
|
||||||
|
spec:
|
||||||
|
accessModes:
|
||||||
|
- ReadWriteOnce
|
||||||
|
resources:
|
||||||
|
requests:
|
||||||
|
storage: 10Mi
|
||||||
|
dataSourceRef:
|
||||||
|
apiGroup: hello.example.com
|
||||||
|
kind: Hello
|
||||||
|
name: example-hello
|
||||||
|
volumeMode: Filesystem
|
||||||
|
```
|
||||||
|
|
||||||
|
Next, run a Job that reads the file in the PVC.
|
||||||
|
|
||||||
|
```yaml
|
||||||
|
apiVersion: batch/v1
|
||||||
|
kind: Job
|
||||||
|
metadata:
|
||||||
|
name: example-job
|
||||||
|
spec:
|
||||||
|
template:
|
||||||
|
spec:
|
||||||
|
containers:
|
||||||
|
- name: example-container
|
||||||
|
image: busybox:latest
|
||||||
|
command:
|
||||||
|
- cat
|
||||||
|
- /mnt/example.txt
|
||||||
|
volumeMounts:
|
||||||
|
- name: vol
|
||||||
|
mountPath: /mnt
|
||||||
|
restartPolicy: Never
|
||||||
|
volumes:
|
||||||
|
- name: vol
|
||||||
|
persistentVolumeClaim:
|
||||||
|
claimName: example-pvc
|
||||||
|
```
|
||||||
|
|
||||||
|
Wait for the job to complete (including all of its dependencies).
|
||||||
|
|
||||||
|
```shell
|
||||||
|
kubectl wait --for=condition=Complete job/example-job
|
||||||
|
```
|
||||||
|
|
||||||
|
And last examine the log from the job.
|
||||||
|
|
||||||
|
```shell
|
||||||
|
kubectl logs job/example-job
|
||||||
|
```
|
||||||
|
|
||||||
|
The output should be:
|
||||||
|
|
||||||
|
```terminal
|
||||||
|
Hello, world!
|
||||||
|
```
|
||||||
|
|
||||||
|
Note that the volume already contained a text file with the string contents from
|
||||||
|
the CR. This is only the simplest example. Actual populators can set up the volume
|
||||||
|
to contain arbitrary contents.
|
||||||
|
|
||||||
|
## How to write your own volume populator
|
||||||
|
|
||||||
|
Developers interested in writing new poplators are encouraged to use the
|
||||||
|
[lib-volume-populator](https://github.com/kubernetes-csi/lib-volume-populator) library
|
||||||
|
and to only supply a small controller wrapper around the library, and a pod image
|
||||||
|
capable of attaching to volumes and writing the appropriate data to the volume.
|
||||||
|
|
||||||
|
Individual populators can be extremely generic such that they work with every type
|
||||||
|
of PVC, or they can do vendor specific things to rapidly fill a volume with data
|
||||||
|
if the volume was provisioned by a specific CSI driver from the same vendor, for
|
||||||
|
example, by communicating directly with the storage for that volume.
|
||||||
|
|
||||||
|
## How can I learn more?
|
||||||
|
|
||||||
|
The enhancement proposal,
|
||||||
|
[Volume Populators](https://github.com/kubernetes/enhancements/tree/master/keps/sig-storage/1495-volume-populators), includes lots of detail about the history and technical implementation
|
||||||
|
of this feature.
|
||||||
|
|
||||||
|
[Volume populators and data sources](/docs/concepts/storage/persistent-volumes/#volume-populators-and-data-sources), within the documentation topic about persistent volumes,
|
||||||
|
explains how to use this feature in your cluster.
|
||||||
|
|
||||||
|
Please get involved by joining the Kubernetes storage SIG to help us enhance this
|
||||||
|
feature. There are a lot of good ideas already and we'd be thrilled to have more!
|
||||||
|
|
||||||
Loading…
Reference in New Issue