2. A simple chart

In this lab we are going to create our very first Helm chart and deploy it.

Task 2.1: Create Chart

First, let’s create our chart. Open your favorite terminal and make sure you’re in the workspace for this lab, e.g. cd ~/<workspace-helm-training>:

helm create mychart

You will now find a mychart directory with the newly created chart. It already is a valid and fully functional chart which deploys a nginx instance. Have a look at the generated files and their content. For an explanation of the files, visit the Helm Developer Documentation . In a later section you’ll find all the information about Helm templates.

Task 2.2: Install Release

Before actually deploying our generated chart, we can check the (to be) generated Kubernetes resources with the following command:

helm install --dry-run --debug --namespace $USER myfirstrelease ./mychart

Finally, the following command creates a new release and deploys the application:

helm install --namespace $USER myfirstrelease ./mychart

With kubectl get pods --namespace $USER you should see a new Pod:

NAME                                     READY   STATUS    RESTARTS   AGE
myfirstrelease-mychart-6d4956b75-ng8x4   1/1     Running   0          2m21s

You can list the newly created Helm release with the following command:

helm ls --namespace $USER

NAME            NAMESPACE       REVISION  UPDATED                                   STATUS    CHART        APP VERSION
myfirstrelease  <namespace>     1         2021-04-14 14:29:58.808282266 +0200 CEST  deployed  mychart-0.1.01.16.0  

Task 2.3: Expose the application

Our freshly deployed nginx is not yet accessible from outside the Kubernetes cluster. To expose it, we have to make sure a so called ingress resource will be deployed as well.

Also make sure the application is accessible via TLS.

A look into the file templates/ingress.yaml reveals that the rendering of the ingress and its values is configurable through values(values.yaml):

{{- if .Values.ingress.enabled -}}
{{- $fullName := include "mychart.fullname" . -}}
{{- $svcPort := .Values.service.port -}}
{{- if semverCompare ">=1.14-0" .Capabilities.KubeVersion.GitVersion -}}
apiVersion: networking.k8s.io/v1
{{- else -}}
apiVersion: extensions/v1beta1
{{- end }}
kind: Ingress
metadata:
  name: {{ $fullName }}
  labels:
    {{- include "mychart.labels" . | nindent 4 }}
  {{- with .Values.ingress.annotations }}
  annotations:
    {{- toYaml . | nindent 4 }}
  {{- end }}
spec:
  {{- if .Values.ingress.tls }}
  tls:
    {{- range .Values.ingress.tls }}
    - hosts:
        {{- range .hosts }}
        - {{ . | quote }}
        {{- end }}
      secretName: {{ .secretName }}
    {{- end }}
  {{- end }}
  rules:
    {{- range .Values.ingress.hosts }}
    - host: {{ .host | quote }}
      http:
        paths:
          {{- range .paths }}
          - path: {{ .path }}
            backend:
              serviceName: {{ $fullName }}
              servicePort: {{ $svcPort }}
          {{- end }}
    {{- end }}
  {{- end }}

Thus, we need to change this value inside our mychart/values.yaml file. This is also where we enable the TLS part:

ingress:
  enabled: true
  hosts:
    - host: mychart-<namespace>.training.cluster.acend.ch
      paths:
        - path: /
          pathType: ImplementationSpecific
  tls:
    - hosts:
        - mychart-<namespace>.training.cluster.acend.ch

Apply the change by upgrading our release:

helm upgrade --namespace $USER myfirstrelease ./mychart

This will result in something similar to:

Release "myfirstrelease" has been upgraded. Happy Helming!
NAME: myfirstrelease
LAST DEPLOYED: Wed Dec  2 14:44:42 2020
NAMESPACE: <namespace>
STATUS: deployed
REVISION: 2
NOTES:
1. Get the application URL by running these commands:
  http://mychart-<namespace>.training.cluster.acend.ch/

Check whether the ingress was successfully deployed by accessing the URL https://mychart-<namespace>.training.cluster.acend.ch/

You should see the Nginx welcome page.

Task 2.4: Overwrite value using commandline param

An alternative way to set or overwrite values for charts we want to deploy is the --set name=value parameter. --set name=value can be used when installing a chart as well as upgrading.

Update the replica count of your nginx Deployment to 2 using --set name=value

Solution Task 2.4

helm upgrade --namespace $USER --set replicaCount=2 myfirstrelease ./mychart

Values that have been set using --set can be reset by helm upgrade with --reset-values.

Verify the replicaCount with the following command:

kubectl get pods --namespace $USER

NAME                                     READY   STATUS    RESTARTS   AGE
myfirstrelease-mychart-c95cb97d6-g76rc   1/1     Running   0          10m
myfirstrelease-mychart-c95cb97d6-tqztc   1/1     Running   0          8m25s

Task 2.5: Rollback a release

Helm also provides the functionality to roll back a release to a specific revision number. Every change you make to a release by installing, upgrading and even rollback, it will increase the REVISION. The deployed revision can be displayed with the following command:

helm ls --namespace $USER

NAME            NAMESPACE       REVISION  UPDATED                                   STATUS    CHART        APP VERSION
myfirstrelease  <namespace>     3         2021-04-14 14:29:58.808282266 +0200 CEST  deployed  mychart-0.1.01.16.0  

Let’s now rollback our release myfirstrelease to revision 2.

helm rollback myfirstrelease 2 --namespace $USER

The replicaCount should be back down to 1 after the rollback. Check if that’s true with the following command:

kubectl get pods --namespace $USER

NAME                                     READY   STATUS    RESTARTS   AGE
myfirstrelease-mychart-c95cb97d6-g76rc   1/1     Running   0          10m

Task 2.6 Explore values.yaml

Have a look at the values.yaml file in your chart and study all the possible configuration params introduced in a freshly created chart.

Task 2.7: Remove release

To remove an application, simply remove the Helm release with the following command:

helm uninstall myfirstrelease --namespace $USER

Do this with our deployed release. With kubectl get pods --namespace $USER you should no longer see your application Pod.