GenericHTTPPopulator

A Kubernetes volume populator to populate the volumes with content of an HTTP endpoint. This document can be referred to read more about the Volume Populators.

Install

Installing custom populator's (GenericHTTPPopulator) CRD

Install the CRD for our new volume populator (GenericHTTPPopulator). A CR of this type (GenericHTTPPopulator) can be used in the PVC's dataSourceRef field to specify this type of populator.

kubectl apply -f https://raw.githubusercontent.com/viveksinghggits/generichttppopulator/master/manifests/genrichttppopulator-crd.yaml

Register custom populator by creating VolumePopulator resource

Make sure the proper CRD is available on the cluster that provides the VolumePopulator CR.

Create an instance of VolumePopulator CR to register our populator (GenericHTTPPopulator).

kubectl apply -f https://raw.githubusercontent.com/viveksinghggits/generichttppopulator/master/manifests/volumepopulator.yaml

Install GenericHTTPPopulator controller

Below command can be used to create a namespace controller and install the populator controller in that namespace. This command will also setup the RBAC required to run the contoller.

kubectl apply -f https://github.com/viveksinghggits/generichttppopulator/raw/master/manifests/controller-deploy.yaml

Make sure the controller is running by checking the status of the pod in controller namespace.

Install data source validator

Data source validator can also optionally be installed to know if the data source specified in the PVC is valid populator or not.

This link can be followed to install the Data source validator.

Usage

To create a PVC in default namespace and populate it with the content of this README file, create a resource of type GenericHTTPPopulator using below command

kubectl apply -f https://raw.githubusercontent.com/viveksinghggits/generichttppopulator/master/manifests/akcessreadmepopulator.yaml

Once GenericHTTPPopulator named akcess-readme-pop is created, it can be referred in a PVC resource like below

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myclaim
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
  resources:
    requests:
      storage: 8Gi
  dataSourceRef:
    apiGroup: k8s.viveksingh.dev
    kind: GenericHTTPPopulator
    name: akcess-readme-pop

Create the PVC resource using the command below

kubectl apply -f https://github.com/viveksinghggits/generichttppopulator/raw/master/manifests/pvc.yaml

PVC would be initially in Pending state and the controller that we have deployed above in controller namespace would create a populator pod that would actually populate the data into the PVC.

Check the status of that pod to make sure that population has succeeded and then check the status of the PVC to make sure that it's in Bound state.

Check the populated data

After the PVC myclaim is in Bound state, create a test pod that would mount this volume at location /mnt/check. So that, the data can be verified by execing into the pod.

kubectl apply -f https://github.com/viveksinghggits/generichttppopulator/raw/master/manifests/checker.yaml

Once the pod is running exec into it, and then cd to /mnt/check and make sure there is a file called README.md with correct content.

YouTube Video

First version of this project was written as a tutorial and the recordings are available at this link.