Why deploy k8s using Helm

Normal:

Your app -> hard-code yaml (deployment/service/ingress) -> Kubectl -> AKS => Use Helm to simplify the application deployment process and avoid hardcoded deployment variables and settings. => Repeatable, reliable, manageable, resuable across mutil teams and env

New:

Your app -> Helm chart -> AKS

Helm components:

Client: is where helm was installed and responsible for creating and submitting the manifest files required to deploy aks application. (Communicate between user and k8s cluster)
Charts: file to describe how the application deployed (chart/value/template)
Releases: The application or a group of application deployed using Chart
Repositories: discoverability and reusability of helm pacakges

Concept

If 2 component depends on each other, try to use 1 chart and set the dependency If 2 component are independent, create 1 chart for each component (Easier for bugfix and upgrade)

Commands

Create your own chart

helm create <name> (Will create chart file template)

Work with repos

Helm repo cli

helm repo add azure-marketplace https://marketplace.azurecr.io/helm/v1/repo
helm repo update
helm repo list
helm search repo <?partialname>

To install a chart (This similar to `kubectl apply` command)

Run helm install to install a chart from:

Chart folder: helm install <release-name> ./drone-webapp
A packaged .tgz tar archive chart: helm install <release-name> ./drone-webapp.tgz
A Helm repository: helm install <release-name> azure-marketplace/aspnet-core

Debuging cli

helm install --debug --dry-run <release-name> ./drone-webapp

Lets install aspnet

Step to release using helm

az aks get-credentials -g learn-helm-deploy-aks-rg -n learn-helm-deploy-aks
# To release
helm install <release-name> azure-marketplace/aspnet-core
# To query all the installed release on the cluster
helm list
 
helm get manifest <release-name> (To get manifest file of a release, optional --revision)
 
helm delete <release-name> (To delete a realease)
 
# Install with set values
 
helm install --set replicaCount=5 <release-name> azure-marketplace/aspnet-core
 
# Upgrade a release
 
helm upgrade <release-name> ./app-chart (This bassically create new revision)
 
helm history <release-name>
 
helm rollback <release-name> <revision-id> (Run helm history to check first)

Write a custom chart or extends it

Template and function

To display the value as a string, you use {{ quote .Values.ingress.enabled }} or {{ .Values.ingress.enabled | quote }} Chaning mutiple function: {{ .Values.ingress.enabled | upper | quote }} Helm chart template support ~60 built-in function

Conditional

{{- if | pipeline | -}}
  # Do something
{{- else if | other pipeline | -}}
  # Do something else
{{- else -}}
  # Default case
{{- end }}

List

ingress:
  enabled: true
  extraHosts:
    - name: host1.local
      path: /
    - name: host2.local
      path: /
    - name: host3.local
      path: /

apiVersion: extensions/v1
kind: Ingress
metadata:
spec:
  rules:
    ...
    {{- range .Values.ingress.extraHosts }}
    - host: {{ .name }}
      http:
        paths:
          - path: {{ .path }}
            ...
    {{- end }}
  ...