Helm Operator Tutorial
- Go through the installation guide.
- User authorized with
We will create a sample project to let you know how it works and this sample will:
- Create a Memcached Deployment if it doesn’t exist
- Ensure that the Deployment size is the same as specified by the Memcached CR spec
- Update the Memcached CR status using the status writer with the names of the memcached pods
Create a new project
Use the CLI to create a new Helm-based nginx-operator project:
mkdir nginx-operator cd nginx-operator operator-sdk init --plugins helm --domain example.com --group demo --version v1alpha1 --kind Nginx
This creates the nginx-operator project specifically for watching the
Nginx resource with APIVersion
demo.example.com/v1alpha1 and Kind
For Helm-based projects,
operator-sdk init also generates the RBAC rules
config/rbac/role.yaml based on the resources that would be deployed by the
chart’s default manifest. Be sure to double check that the rules generated
config/rbac/role.yaml meet the operator’s permission requirements.
To learn more about the project directory structure, see the project layout doc.
Use an existing chart
Instead of creating your project with a boilerplate Helm chart, you can also use
--helm-chart-version to use an existing chart, either from your local filesystem or a remote chart repository.
--helm-chart is specified, the
--kind flags become optional. If left unset, the default will be:
|kind||deduce from the specified chart|
--helm-chart is a local chart archive (e.g
example-chart-1.2.0.tgz) or directory,
it will be validated and unpacked or copied into the project.
Otherwise, the SDK will attempt to fetch the specified helm chart from a remote repository.
If a custom repository URL is not specified by
--helm-chart-repo, the following chart reference formats are supported:
<repoName>/<chartName>: Fetch the helm chart named
chartNamefrom the helm chart repository named
repoName, as specified in the
helm repo addto configure this file.
<url>: Fetch the helm chart archive at the specified URL.
If a custom repository URL is specified by
--helm-chart-repo, the only supported format for
<chartName>: Fetch the helm chart named
chartNamein the helm chart repository specified by the
--helm-chart-version is not set, the SDK will fetch the latest available version of the helm chart. Otherwise, it will fetch the specified version. The option
--helm-chart-version is not used when
--helm-chart itself refers to a specific version, for example when it is a local path or a URL.
Note: For more details and examples run
operator-sdk init --plugins helm --help.
Customize the operator logic
For this example the nginx-operator will execute the following
reconciliation logic for each
Nginx Custom Resource (CR):
- Create a nginx Deployment if it doesn’t exist
- Create a nginx Service if it doesn’t exist
- Create a nginx Ingress if it is enabled and doesn’t exist
- Ensure that the Deployment, Service, and optional Ingress match the desired configuration (e.g. replica count, image, service type, etc) as specified by the
Watch the Nginx CR
By default, the nginx-operator watches
Nginx resource events as shown
watches.yaml and executes Helm releases using the specified chart:
# Use the 'create api' subcommand to add watches to this file. - group: demo version: v1alpha1 kind: Nginx chart: helm-charts/nginx #+kubebuilder:scaffold:watch
Reviewing the Nginx Helm Chart
When a Helm operator project is created, the SDK creates an example Helm chart that contains a set of templates for a simple Nginx release.
For this example, we have templates for deployment, service, and ingress
resources, along with a
NOTES.txt template, which Helm chart developers use
to convey helpful information about a release.
If you aren’t already familiar with Helm Charts, take a moment to review the Helm Chart developer documentation.
Understanding the Nginx CR spec
Helm uses a concept called values to provide customizations
to a Helm chart’s defaults, which are defined in the Helm chart’s
Overriding these defaults is as simple as setting the desired values in the CR spec. Let’s use the number of replicas as an example.
helm-charts/nginx/values.yaml, we see that the chart has a
replicaCount and it is set to
1 by default. If we want to have
2 nginx instances in our deployment, we would need to make sure our CR spec
config/samples/demo_v1alpha1_nginx.yaml to look like the following:
apiVersion: demo.example.com/v1alpha1 kind: Nginx metadata: name: nginx-sample spec: replicaCount: 2
Similarly, we see that the default service port is set to
80, but we would
like to use
8080, so we’ll again update
by adding the service port override:
apiVersion: demo.example.com/v1alpha1 kind: Nginx metadata: name: nginx-sample spec: replicaCount: 2 service: port: 8080
As you may have noticed, the Helm operator simply applies the entire spec as if
it was the contents of a values file, just like
helm install -f ./overrides.yaml
Run the operator
There are three ways to run the operator:
- As Go program outside a cluster
- As a Deployment inside a Kubernetes cluster
- Managed by the Operator Lifecycle Manager (OLM) in bundle format
1. Run locally outside the cluster
Execute the following command, which install your CRDs and run the manager locally:
make install run
2. Run as a Deployment inside the cluster
Build and push the image
Build and push the image:
export USERNAME=<quay-namespace> make docker-build docker-push IMG=quay.io/$USERNAME/nginx-operator:v0.0.1
Note: The name and tag of the image (
IMG=<some-registry>/<project-name>:tag) in both the commands can also be set in the Makefile.
Modify the line which has
IMG ?= controller:latest to set your desired default image name.
Deploy the operator
By default, a new namespace is created with name
<project-name>-system, i.e. nginx-operator-system and will be used for the deployment.
Run the following to deploy the operator. This will also install the RBAC manifests from
make deploy IMG=quay.io/$USERNAME/nginx-operator:v0.0.1
Verify that the nginx-operator is up and running:
$ kubectl get deployment -n nginx-operator-system NAME READY UP-TO-DATE AVAILABLE AGE nginx-operator-controller-manager 1/1 1 1 8m
3. Deploy your Operator with OLM
First, install OLM:
operator-sdk olm install
Then bundle your operator and push the bundle image:
make bundle IMG=$OPERATOR_IMG # Note the "-bundle" component in the image name below. export BUNDLE_IMG="quay.io/$USERNAME/nginx-operator-bundle:v0.0.1" make bundle-build BUNDLE_IMG=$BUNDLE_IMG make docker-push IMG=$BUNDLE_IMG
Finally, run your bundle:
operator-sdk run bundle $BUNDLE_IMG
Check out the docs for a deep dive into
operator-sdk's OLM integration.
Deploy the Nginx custom resource
Apply the nginx CR that we modified earlier:
kubectl apply -f config/samples/demo_v1alpha1_nginx.yaml
Ensure that the nginx-operator creates the deployment for the CR:
$ kubectl get deployment NAME READY UP-TO-DATE AVAILABLE AGE nginx-sample 2/2 2 2 2m13s
Check the pods to confirm 2 replicas were created:
$ kubectl get pods NAME READY STATUS RESTARTS AGE nginx-sample-c786bfdcf-4g6md 1/1 Running 0 81s nginx-sample-c786bfdcf-6bhmx 1/1 Running 0 81s
Check that the service port is set to
$ kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE nginx-sample ClusterIP 10.96.26.3 <none> 8080/TCP 1m
Update the replicaCount and remove the port
spec.replicaCount field from 2 to 3, remove the
$ cat config/samples/demo_v1alpha1_nginx.yaml apiVersion: demo.example.com/v1alpha1 kind: Nginx metadata: name: nginx-sample spec: replicaCount: 3
And apply the change:
kubectl apply -f config/samples/demo_v1alpha1_nginx.yaml
Confirm that the operator changes the deployment size:
$ kubectl get deployment NAME DESIRED CURRENT UP-TO-DATE AGE nginx-sample 3/3 3 3 7m29s
Check that the service port is set to the default (
$ kubectl get service NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE nginx-sample ClusterIP 10.96.152.76 <none> 80/TCP 7m54s
Use the following command to check the operator logs.
kubectl logs deployment.apps/nginx-operator-controller-manager -n nginx-operator-system -c manager
Use the following command to check the CR status and events.
kubectl describe nginxes.demo.example.com
Clean up the resources:
kubectl delete -f config/samples/demo_v1alpha1_nginx.yaml
Note: Make sure the above custom resource has been deleted before proceeding to
make undeploy, as helm-operator’s controller adds finalizers to the custom resources.
Otherwise your cluster may have dangling custom resource objects that cannot be deleted.