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Helm 201

Overview

An 201 introduction in Helm (v3) with the following topics

  • Templating

  • Charts and Subcharts

  • Life Cycle and Hooks

  • OCI Registry

Action

The entire intro is prepared as Jupyter Notebook, helm-201.ipynb or Kui Guidebook, helm-201.md.

Advanced

The following section covers additional topics like

  • charts dependency

  • how to structure charts for various stage installations but expecting always only values.yaml

  • need of various values file (app-specific and global values)

$ cd hierarchy

$ tree . -L 3
.
├── comp1
│   ├── Chart.yaml
│   ├── charts
│   ├── templates
│   │   ├── NOTES.txt
│   │   ├── _helpers.tpl
│   │   ├── deployment.yaml
│   │   ├── hpa.yaml
│   │   ├── ingress.yaml
│   │   ├── route.yaml
│   │   ├── service.yaml
│   │   └── serviceaccount.yaml
│   └── values.yaml
├── comp2
│   ├── Chart.yaml
│   ├── charts
│   ├── templates
│   │   ├── NOTES.txt
│   │   ├── _helpers.tpl
│   │   ├── deployment.yaml
│   │   ├── hpa.yaml
│   │   ├── ingress.yaml
│   │   ├── route.yaml
│   │   ├── service.yaml
│   │   └── serviceaccount.yaml
│   └── values.yaml
└── systemA
    ├── stage-prod
    │   ├── Chart.lock
    │   ├── Chart.yaml
    │   ├── charts
    │   └── values.yaml
    └── stage-test
        ├── Chart.lock
        ├── Chart.yaml
        ├── charts
        └── values.yaml

11 directories, 26 files

In the above example we have 2 components and 1 system including the components as dependency. The system (systemA) will be installed in 2 stags stage-test and stage-prod.

Chart.yaml contains the information which component/chart and version is needed.

The following commands are necessary to deploy the e.g. systemA in stage-test

$ cd hierarchy/systemA/stage-test

$ helm dependency build

$ helm template sys-a-test . --output-dir ../../../work/systemA-test --debug

The result is

systemA-test
└── comp1
    └── charts
        └── comp1
            └── templates
                ├── deployment.yaml
                ├── route.yaml
                ├── service.yaml
                └── serviceaccount.yaml

4 directories, 4 files

Verifying the value files

cat systemA/stage-test/values.yaml

comp1:
  config:
    probe:
      enabled: false
    route:
      enabled: true
    envs:
      A: "some content"
      TEKTON_101_ENV_NAME: App3-TEST
      TEKTON_101_ENV_EXAMPLE: Version-0.3-TEST

and the resulting template

cat systemA-test/comp1/charts/comp1/templates/deployment.yaml| grep -i 'env:' -A6
          env:
            - name: A
              value: some content
            - name: TEKTON_101_ENV_EXAMPLE
              value: Version-0.3-TEST
            - name: TEKTON_101_ENV_NAME
              value: App3-TEST

Summary

Helm is a de-facto standard in providing Kubernetes resources to deploy an application with all resources in a Kubernetes/OpenShift cluster. This article provides an introduction in some specific Helm topics.

License

This article and project are licensed under the Apache License, Version 2. Separate third-party code objects invoked within this code pattern are licensed by their respective providers pursuant to their own separate licenses. Contributions are subject to the Developer Certificate of Origin, Version 1.1 and the Apache License, Version 2.

See also Apache License FAQ .