harivemula / chartexample

helm 3 chart example

Creating a Helm Chart using helm3 for an application.

Install helm (version >3.x) cli, Follow the steps described in this link. Run the below command to ensure the version.

$ helm version --short

Go to the directory where you would like to create the chart. Run the below command, which creates chart with pre-defined templates. Use the name of the chart as your application/module name.

$ helm create <name>

$ helm create chartexample

This will create the folder with the name of the chart in current working directory. Change to the newly created directory (chartexample) and view the contents

$ cd chartexample

$ tree
.
├── Chart.yaml
├── charts
├── templates
│   ├── NOTES.txt
│   ├── _helpers.tpl
│   ├── deployment.yaml
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── service.yaml
│   ├── serviceaccount.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml

• Chart.yaml
  • This defines the chart and its key properties.
• values.yaml
  • Define all the configurable properties for the chart deployment.
• charts
  • You may add any dependent chart(s) into this directory
• templates
  • A directory of templates that, when combined with values, will generate valid Kubernetes manifest files. The templates are written using Go Template Language.

Chart.yaml

apiVersion: v2 - v2 represents helm3 compatible charts name: chartexample - name of the chart type: application - Default is application. Other supported value is Library version: 0.1.0 - This is the chart version, increment this version if you change the app version or any change to the deployment templates. appVersion: 1.16.0 - Your application version. Change whenver there is any change to the application.

Apart from the above there are many optional fields available.

values.yaml

The default configuration values for this chart. This comes with pre-defined set of properties which are used in the templates. You may add or modify them, remember to change the templates which depends on these default properties.

In my example, i would like to change the below in values.yaml

image:
  repository: harivemula/kubeconfigexample
...
serviceAccount:
  create: false
...

resources:
  limits:
    cpu: 500m
    memory: 750Mi
  requests:
    cpu: 500m
    memory: 750Mi

...
autoscaling:
  enabled: true
  minReplicas: 1
  maxReplicas: 2
  targetCPUUtilizationPercentage: 80

I'm introducing few more properties in values.yaml

port:
  containerPort: 8080

volumeMounts:
  - name: cache-volume
    mountPath: /cache
    
volumes:
  - name: cache-volume
    emptyDir: {}
    
env:
  - name: DEMO_ENV_PROP
    value: mydemoenvproperty
  - name: ENV_PROP
    value: justenvprop

In the above content, i have used the same structure of kubernetes manifest for adding new properties, however it is not manadatory. It all depends on how you want to use the property in templates.

Example, we have defined port.containerPort in the above example, and going to use this in the templates/deployments.yaml as

ports:
- name: http
  containerPort: {{ .Values.port.containerPort }}

Instead you may define simply as container_port: 8080 in values.yaml and refer it in templates/deployment.yaml like below

ports:
- name: http
  containerPort: {{ .Values.container_port }}

templates

By default templates directory contains templates for below kubernetes objects.

• deployment
• service
• service account
• ingress
• horizontal pod autoscaling

You may add any other objects you need, like configmap.

The _helpers.tpl file defines named templates. Example, it defines a templete to derive name of the chart. Go to the link.

{{- define  "chartexample.name" -}}
{{- default .Chart.Name .Values.nameOverride | trunc  63 | trimSuffix  "-" }}
{{- end }}

Modifying the templates

Modify the provided templates to suite to your requirement. In my case i have modified the deployment.yaml with highlighted fields below.

...
          ports:
            - name: http
              containerPort: {{ .Values.port.containerPort }}
              protocol: TCP
...
          env:
            {{- toYaml .Values.env | nindent 12 }}
...
          volumeMounts:
            - name: config-volume
              mountPath: /workspace/config
            {{- toYaml .Values.volumeMounts | nindent 12 }}
...
      volumes:
        - name: config-volume
          configMap:
            name: {{ .Release.Name }}-samplespringconfig
        {{- toYaml .Values.volumes | nindent 8 }}

...

In the above lets take couple of examples

env:
  {{- toYaml .Values.env | nindent 12 }}

env: As in my values.yaml, i have defined the same structure it should be in kubernetes manifest, now i am trying to simply get the env property values and copying here as yaml output with indent 12.

volumes:
  - name: config-volume
    configMap:
      name: {{ .Release.Name }}-samplespringconfig
  {{- toYaml .Values.volumes | nindent 8 }}

volumes: I have defined a volume with configmap as source here in the template directly and if any other volumes defined on values.yaml, all will be added here as yaml with indent 8. And the name of the configmap is based on the chart release name.

Adding new object template

I would like to create configmap to pass some properties to my application and use the configmap as volume to deployment. For that, i am adding a new file in templates directory as configmap.yaml.

apiVersion: v1
kind: ConfigMap
metadata:
name: {{ .Release.Name }}-samplespringconfig
data:
application.properties: |
demo.file.prop=ValueFromConfig

In the configmap, i am using the name as Release.Name prefix, which is the name we give when we deploy the chart. So, the configmap object name is dynamic. You can use templates in the data section as well.

Package Chart

Once you have completed with your modifications, you can package the chart. Before packaging, verify if the chart is well formed by running

helm lint

Run the below to package chart

helm package .

This will package your chart with name < chartname >-< chartversion >.tgz. Example, chartexample-0.1.0.tgz