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Helm 201
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Helm 201

A deep-dive into Helm (v3) and details like

Init

helm version
export wd_init="/Users/haddouti/Documents/Data/workspaces/repos/haf-tech/helm-201/work/helm-init3"

Let's create a new Helm chart

echo $wd_init
mkdir -p $wd_init
helm create $wd_init/demo-helm-201
tree $wd_init

Chart Structure and Overview

  • Chart.yaml common meta information
    • avoid using appVersion - handle version in env-specific value-files or as field which will be overwritten during helm execution
cat $wd_init/demo-helm-201/Chart.yaml | grep -B2 -i 'version:'

???+ tip "Goal" Templating * include output/result from namespaced functions * Whitespaces and new lines, indent

???+ tip "Action" Action / Scripts #00 * Intro template and include * modify service template

Render template and generate Kubernetes resource files

helm template demo-helm-201-common $wd_init/demo-helm-201 -f $wd_init/demo-helm-201/values.yaml --output-dir=work/out/common

???+ tip "Goal" Templates and Variables * .Values.* holds all variables (from file and command line) * values.yaml and any additional values-file will be merged

???+ tip "Action" Action / Scripts #01 * image.version * env-specific values file

Render template and generate Kubernetes resource files for TEST stage

helm template demo-helm-201-test $wd_init/demo-helm-201 -f $wd_init/demo-helm-201/values.test.yaml --output-dir=work/out/test

???+ tip "Goal" Templating, Functions * _helpers.tpl holds set of helper functions used in template files * common Go template functions are included (and, or, len, ...)

???+ tip "Action" Action / Scripts * go through _helpers.tpl

cat $wd_init/demo-helm-201/templates/_helpers.tpl

???+ tip "Goal" Templating, Functions * with set the scope * range iterate

???+ tip "Action" Action / Scripts #02 * new sa.yaml * values in values.test.yaml

Render template and generate Kubernetes resource files for TEST stage

helm template demo-helm-201-test $wd_init/demo-helm-201 -f $wd_init/demo-helm-201/values.test.yaml --output-dir=work/out/test

Charts and Subcharts

???+ tip "Goal" Charts and Subcharts * Subchart is a standalone chart * only parent knows the subcharts / childrens * ...and only parent can override fields

???+ tip "Action" Action * checkout existing chart * create a new chart in parent/chart directory * configure dependency

Print out existing chart (without subchart)

tree $wd_init

Create new (sub)chart in the charts dir

helm create $wd_init/demo-helm-201/charts/demo-subchart
rm -rf $wd_init/demo-helm-201/charts/demo-subchart/templates/*
tree $wd_init

???+ tip "Action" Action / Scripts #03 * template for ConfigMap in subchart * value file in subchart * override options

Dry-Run subchart - with local value file

helm install --generate-name --dry-run --debug $wd_init/demo-helm-201/charts/demo-subchart

Render entire chart - with pre value file, to override subchart fields

helm template demo-helm-201-pre $wd_init/demo-helm-201 -f $wd_init/demo-helm-201/values.pre.yaml --output-dir=work/out/pre

Render entire chart - with test value file, to NOT override subchart fields

helm template demo-helm-201-test $wd_init/demo-helm-201 -f $wd_init/demo-helm-201/values.test.yaml --output-dir=work/out/test

??? tip "Be aware to consider that fields/values are not available/null in your template"

Life Cycle and Hooks

Hooks allows to execute specific resource definitions at defined points in the Helm life cycle. Available hooks

  • pre-install
  • post-install
  • pre-delete
  • post-delete
  • pre-upgrade
  • post-upgrade
  • pre-rollback
  • post-rollback
  • test

Examples

  • prepare the installation and create specific resources beforehand (ConfigMap, Job etc)
  • clean up database before uninstalling application
  • return a license or deregister/unsubscribe

Pre-Install and Post-Delete

Example for pre-install and post-delete hook. Hooks are usual Kubernetes resource definitions with special annotations.

metadata:
  annotations:
    "helm.sh/hook": pre-install, post-delete
    "helm.sh/hook-weight": "-5"
    "helm.sh/hook-delete-policy": hook-succeeded

Create new (sub)chart in the charts dir

helm create $wd_init/demo-helm-201/charts/demo-hook
rm -rf $wd_init/demo-helm-201/charts/demo-hook/templates/ingress.yaml && \
rm -rf $wd_init/demo-helm-201/charts/demo-hook/templates/service.yaml && \
rm -rf $wd_init/demo-helm-201/charts/demo-hook/templates/tests && \
tree $wd_init

???+ tip "Action" Action / Scripts #04 * create 2 jobs for different hooks * install and upgrade

Install subchart for hook testing ...some OCP permissions adjustments (for nginx)...

oc adm policy add-scc-to-user anyuid -z demo-hook-dev
helm upgrade --install demo-hook-dev $wd_init/demo-helm-201/charts/demo-hook -n demo-helm

Update subchart for hook testing now with job definitions

helm upgrade --install demo-hook-dev $wd_init/demo-helm-201/charts/demo-hook -n demo-helm

???+ tip "Action" Action * current pods and jobs * events * clean-up and check out the job with post-delete

Delete subchart which triggers hook

helm delete demo-hook-dev -n demo-helm

OCI Registry

Helm 3 provides the option to store helm charts not only on a HTTP server, but also in a OCI Registry. This allows the option to hold the artifacts (container image and helm charts) in the same registry.

Testing

???+ tip "Action" Action * use a local registry * push a local helm chart * install from OCI registry

Run a local registry

docker run -dp 5000:5000 --restart=always --name registry registry

Create helm package from the hook subchart ...helm package...

helm package $wd_init/demo-helm-201/charts/demo-hook --version 1.0.3 --destination $wd_init && \
helm package $wd_init/demo-helm-201/charts/demo-hook --version 1.0.4 --destination $wd_init

Push helm package to registry ...helm registry login...

helm registry login -u testuser -p testpassword localhost:5000

...helm package push...

helm push $wd_init/demo-hook-1.0.3.tgz oci://localhost:5000/helm-charts && \
helm push $wd_init/demo-hook-1.0.4.tgz oci://localhost:5000/helm-charts

Verify helm package in OCI registry ...show chart details...

helm show chart oci://localhost:5000/helm-charts/demo-hook

Install (render) helm package directly from OCI registry ...render existing chart from registry...

helm template release-demo-hook-oci oci://localhost:5000/helm-charts/demo-hook --version 1.0.3 --output-dir=work/out/oci

...try to render non-existing chart from registry...

helm template release-demo-hook-oci oci://localhost:5000/helm-charts/demo-hook --version 2.2.2 --output-dir=work/out/oci

Misc

Some additional details

Internal/Release State

With Helm3 not Tiller exists anymore. All configuration and release state, including value files, is now stored in a Secret instead of a ConfigMap.

Install subchart

helm upgrade --install release-demo-hook-state $wd_init/demo-helm-201/charts/demo-hook -n demo-helm

List all existing helm releases

helm list

Print out release information from Helm Release Secret

oc get secret sh.helm.release.v1.release-demo-hook-state.v1 -o jsonpath='{.data.release}' -n demo-helm | base64 --decode | base64 --decode | gunzip -c | jq

Helm Upgrade and force re-deployment

Helm determines the relevant changes and updates only the necessary resources. In case the content of a ConfigMap changed, but not the image version, a redeployment or restart of the deployment will be not triggered. To trigger a redeployment a relation between ConfigMap content and Deployment is needed

kind: Deployment
spec:
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}

The idea is, that the Deployment contains an annotation with a checksum of the related ConfigMap. Any changes in the content, results in an other sha256sum, results in an other annotation, which results in modified Deployment definition.

IBM Cloud Container Registry

The IBM Cloud Container Registry is OCI compliant and could also be used for Helm packages

Push chart to IBM CR

ibmcloud login --sso
ibmcloud cr login
helm registry login -u iamapikey

helm push $wd_init/demo-hook-1.0.1.tgz oci://de.icr.io/demo-helm

VS Code Extensions

  • yaml
  • kubernetes understands also the helm template syntax

Summary

This was a walkthrough for Helm 201 with covering topics like

  • templating
  • charts and subcharts
  • OCI Registry

References