Building your own Helm Charts

If you have not installed helm yet, do so by using

curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 |  bash 

helm

Part I - Generating a Chart with One Service

Create a namespace and switch to it

kubectl create namespace dev
kubectl config set-context --current --namespace=dev
kubectl config get-contexts

Generate a helm chart scaffold and change into the directory created to create a copy of values.yaml

cd ~
helm create instavote
cd instavote/
cp values.yaml values.dev.yaml 

Edit values.dev.yaml  to update replicaCount, image and tag as


replicaCount: 4 
image: 
  repository: schoolofdevops/vote 
  pullPolicy: IfNotPresent
  # Overrides the image tag whose default is the chart appVersion. 
  tag: "v5" 

Update service type to Node Port

service:
  type: NodePort
  port: 80
  nodePort: 30300

Also update the service.yaml template with the additional property for nodePort defined as ,

File : service.yaml

apiVersion: v1
kind: Service
metadata:
  name: vote
  labels:
    {{- include "instavote.labels" . | nindent 4 }}
spec:
  type: {{ .Values.service.type }}
  ports:
    - port: {{ .Values.service.port }}
      targetPort: http
      protocol: TCP
      name: http
      nodePort: {{ .Values.service.nodePort }}
  selector:
    {{- include "instavote.selectorLabels" . | nindent 4 }}

Install this chart with helm to deploy the vote service as:

helm install instavote -n dev --values=values.dev.yaml  . --dry-run
helm install instavote -n dev --values=values.dev.yaml  .

Validate with

helm list -A
kubectl get all

Part II - Adding support for More Microservices

Create copy of the templates so that you could add support for one more service e.g. redis


cd templates/
mkdir vote redis
mv deployment.yaml  hpa.yaml  ingress.yaml  service.yaml vote/
cp vote/*.yaml redis/

You will start editing the templates so that template variables such as Values.replicaCount will be replaced with Values.vote.replicaCount. Thats the theme you will have to follow from here on.

e.g. this is the exisinng code

{{- if not .Values.autoscaling.enabled }}
replicas: {{ .Values.replicaCount }}
{{- end }}

which should be changes to


spec:
  {{- if not .Values.autoscaling.enabled }}
  replicas: {{ .Values.vote.replicaCount }}
  {{- end }}

To make it easier, you could use text replacement feature of sed

cd templates/vote/
sed -i 's/Values./Values.vote./g' deployment.yaml
sed -i 's/Values./Values.vote./g' service.yaml

and then

cd templates/redis/
sed -i 's/Values./Values.redis./g' deployment.yaml
sed -i 's/Values./Values.redis./g' service.yaml

You will also need to change a few things in the deployments and services including,

  • change the name in the metadata field for the deplyoments and services for both apps
  • remove nodePort configuration from service spec of redis
  • update the spec.template.spec.labels as well as spec.selectors.labelSelectors with application specific labels for both apps
  • update the spec.selectors and add the same label in the services as well

e.g.

update 

templates/vote/deployment.yaml
templates/vote/service.yaml

from

metadata:
  name: {{ include "instavote.fullname" . }}

to

metadata:
  name: vote

And similarly in the following files

templates/redis/deployment.yaml
templates/redis/service.yaml

from

metadata:
  name: {{ include "instavote.fullname" . }}

to

metadata:
  name: redis

Also change the selector in templates/redis/deployment.yaml along with template labels as, 

  selector:
    matchLabels:
      {{- include "instavote.selectorLabels" . | nindent 6 }}
      app: redis
  template:
    metadata:
      {{- with .Values.redis.podAnnotations }}
      annotations:
        {{- toYaml . | nindent 8 }}
      {{- end }}
      labels:
        {{- include "instavote.labels" . | nindent 8 }}
        {{- with .Values.redis.podLabels }}
        {{- toYaml . | nindent 8 }}
        {{- end }}
        app: redis

and selector spec in templates/redis/service.yaml as, 

spec:
  type: {{ .Values.redis.service.type }}
  ports:
    - port: {{ .Values.redis.service.port }}
      targetPort: http
      protocol: TCP
      name: http
  selector:
    {{- include "instavote.selectorLabels" . | nindent 4 }}
    app: redis

Now update instavote/values.yaml to support multiple services 

  • add vote as top level key 
  • indent all properties so that those become sub properties of key added above i.e.  vote
  • copy over and create blocks for redis

Use this file as a reference values.yaml

Now go ahead and deploy by

  • Creating your own copy of values.yaml
  • Providing values specific to those services

You could download this file with sample values values.dev.yaml using the following command :

wget -c https://gist.githubusercontent.com/initcron/67e104f3a2949f20c2da06e19c854faa/raw/90c7b0c330f133efae43ea71efb1beba314ea451/values.dev.yaml

And apply

helm uninstall instavote
helm install instavote -n dev --values=values.dev.yaml  .
helm list -A
kubectl get all

Validate that vote and redis are running with the values that you provided.

Part III : Overriding Values, Rollbacks

Lets learn how to override values from the command line. To do so, lets add one property

File : templates/vote/deployment.yaml

containers:
  - name: vote
    env:
      - name: OPTION_A
        value: {{ .Values.vote.options.A }}
      - name: OPTION_B
        value: {{ .Values.vote.options.B }}

This will read from values file and set those as environmnt variables. Lets set the default values.

File: values.dev.yaml

vote:
  replicaCount: 2

  options:
    A: MacOS
    B: Windows

now upgrade the release as

helm upgrade  instavote -n dev --values=values.dev.yaml  .

Check the application to see the default values being visible.

You could override the values from the command line as

helm upgrade instavote --values values.dev.yaml --set vote.options.A=Green --set vote.options.B=Yellow .

check the web app now

try one more time

helm upgrade instavote --values values.dev.yaml --set vote.options.A=Orange --set vote.options.B=Blue .

you should see the values change every time.

Check the release now

helm list -A

[sample output]

NAME        NAMESPACE   REVISION    UPDATED                                 STATUS      CHART           APP VERSION
instavote   dev            7        2024-05-14 03:31:34.717912894 +0000 UTC deployed    instavote-0.1.0 1.16.0

try rolling back a version

e.g.

helm rollback instavote

you could also go back to a specific version using the revision number as 

helm rollback instavote xx

where replace xx with the revision number you wish to roll back to.

Exercise

Now that you have deployed vote and redis, go ahead and add the code to deploy  worker, db and result as well.