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reference

  • https://chat.deepseek.com/a/chat/s/3d8b4d99-81b7-4dac-ad69-519f9bc33dea
  • https://chatgpt.com/c/be9c3fd6-6caf-40c0-82c6-a7c28814284c

HELM

  • install : https://helm.sh/docs/intro/quickstart/
  • install docker + kubeCTL + having Cluster running
  • stores release info in configMap/Secret in same namespace where release done
  • export HELM_DRIVER=configmap
  • helm install myrelease ./mychart --debug --dry-run
  • doesn't directly call kubectl behind the scenes. Helm has its own Go client libraries that communicate directly with the Kubernetes API server.
  • Smart Update Detection
  • It compares the current state in Kubernetes with your new manifests
  • Only resources with actual changes will be updated
  • single-release-multiple-revisions model
  • release-blue : revision 1, 2,....
  • release-green : revision 1, 2,....

Intro

  • definition:
  • template engine for K8s manifest yml files.
  • package manager for Kubernetes.
  • benefit/s:
  • simplifies the process of defining, installing, and managing Kubernetes applications.
  • reuse across env and clusters.

Key Components

  • chart : collections of files that describe a related set of Kubernetes resources.
  • Chart.yaml: metadata - name, version, and description.
  • Values.yaml:
    • default configuration values.
    • Users can override these values based on env while installing chart.
    • values-dev,prod,etc.
  • Templates:
    • A directory that contains the Kubernetes resource definitions.
    • yml : deployment/service/configmap/PersistentVolume
  • Charts: dependencies
    • directory that can contain dependent charts.

commands:

  • helm repo add bitnami https://charts.bitnami.com/bitnami

  • helm repo list ```

    • NAME URL
      bitnami https://charts.bitnami.com/bitnami
      puppet https://puppetlabs.github.io/puppetserver-helm-chart hashicorp https://helm.releases.hashicorp.com ```

  • create or pull

  • helm create spring-helm.
  • helm pull --untar bitnami/wordpress
  • helm list
  • helm install release-v2 spring-helm # uninstall
  • -f custom-values.yaml
  • --set key1=value1,key2=value2
  • each release has name. here release-v2
  • --set image.repository=,image.tag=
  • helm upgrade release-v2 spring-helm
  • Each upgrade creates a new revision of the same release 👈
  • helm delete release-v2
  • helm history release-v2
  • hows all revisions for release-2
  • helm rollback release-v2 revision-n

img.png

Scenario / JT

  1. deploy in order : pod-2(kafka) > then, pod-3(Database) > then, pod-1(SB)
  2. issues without helm:
  3. so many deployment/service manifest yml : single chart with nested child chart
  4. deploy them in order : chart with dependent chart.
  5. rollout/rollback/version them all together : rollback, history, etc
  6. run deployment with env specific values :