clarkhale / helm-app-operator-kit

Tool for creating a Kubernetes Operator from a Helm Chart

This project is a component of the Operator Framework, an open source toolkit to manage Kubernetes native applications, called Operators, in an effective, automated, and scalable way. Read more in the introduction blog post.

Helm App Operator Kit

This repository serves as a template for easily creating managed stateless applications that run either Kubernetes Deployments or Helm charts. It was inspired by the Lostromos project. The underlying Operator was created using the operator-sdk new command.

Installing a custom Helm-based app

While the Operator Lifecycle Manager can only manage Operators, not all applications require developers to write a custom Operator. The Helm App Operator Kit makes it possible to leverage a pre-existing Helm chart to deploy Kubernetes resources as a unified application.

git clone https://github.com/coreos/helm-app-operator-kit
cd helm-app-operator-kit

Prerequisites

• Kubernetes 1.9+ cluster
• docker client
• kubectl client
• Helm Chart

Instructions

1. Run the following:

$ git checkout [e-mail]:operator-framework/helm-app-operator-kit.git && cd helm-app-operator-kit
$ cd helm-app-operator && dep ensure && cd ..
$ docker build -t quay.io/<namespace>/<chart>-operator --build-arg HELM_CHART=/path/to/helm/chart --build-arg API_VERSION=<group/version> --build-arg KIND=<Kind> .
$ docker push quay.io/<namespace>/<chart>-operator

2. Modify the following Kubernetes YAML manifest files in helm-app-operator/deploy:

File	Action
deploy/crd.yaml	Define your CRD (kind, spec.version, spec.group must match the docker build args)
deploy/cr.yaml	Make an instance of your custom resource (kind, apiVersion *must match the docker build args)
deploy/operator.yaml	Replace <namespace> and <chart> appropriately
deploy/rbac.yaml	Ensure the resources created by your chart are properly listed
deploy/olm-catalog/csv.yaml	Replace fields appropriately. Define RBAC in spec.install.spec.permissions. Ensure spec.customresourcedefinitions.owned correctly contains your CRD
deploy/olm-catalog/crd.yaml	Define your CRD (kind, spec.version, spec.group must match the docker build args)

3. Apply the manifests to your Kubernetes cluster (if using Operator Lifecycle Manager):

$ kubectl create -f helm-app-operator/deploy/olm-catalog/crd.yaml
$ kubectl create -n <operator-namespace> -f helm-app-operator/deploy/olm-catalog/csv.yaml

Otherwise, manually create the RBAC and deployment resources:

$ kubectl create -f helm-app-operator/deploy/crd.yaml
$ kubectl create -n <operator-namespace> -f helm-app-operator/deploy/rbac.yaml
$ kubectl create -n <operator-namespace> -f helm-app-operator/deploy/operator.yaml

Creating an instance of the example application

After the CustomResourceDefinition and ClusterServiceVersion-v1 resources for the new application have been applied, new instances of that app can be created:

$ kubectl create -n <operator-namespace> -f helm-app-operator/deploy/cr.yaml

Confirm the resources defined in the Helm Chart were created.