Hello-Helm

Helm is the package manager for Kubernetes (like yum) that allows easily package, configure, and deploy applications onto Kubernetes clusters.

Helm charts are packages (like rpms) It contains pre-configured kubernetes resources such as ConfigMaps, Deployments, Services and editable settings for them.

Why do we need Helm?

Managing repeating Kubernetes manifest or copying from one to another, editing hardcode values and validating syntax, sharing across env like Dev, QA, Production etc. is hard.

Simple Sharing
Rollbacks

Install Helm (within Kubernetes Master/Control Node)

export VERIFY_CHECKSUM=false

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

helm version

Helm 3 Architeture

Helm installs charts into Kubernetes, creating a new release for each installation. And to find new charts, you can search Helm chart repositories.

Repository is the place where charts can be collected and shared.
Release is an instance of a chart running in a Kubernetes cluster.
Chart is a Helm package. It contains all of the resource definitions necessary to run an application on Kubernetes Cluster

helm search hub wordpress # searches Artifact Hub

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

helm show values bitnami/wordpress # shows that service type uses `LoadBalancer`

cat <<EOF > values.yaml
> service:
>  type: NodePort
> EOF

helm install -f values.yaml my-wordpress bitnami/wordpress --version 8.0.2

helm list

helm repo list

Creating Your Own Charts

helm create webapp

Delete below files

rm webapp/templates/tests/test-connection.yaml
rm webapp/templates/serviceaccount.yaml
rm webapp/templates/ingress.yaml
rm webapp/templates/hpa.yaml

Edit/Add

Chart.yaml,
values.yaml,
prod-values.yaml,
/template/deployment.yaml,
/template/service.yaml
and modify /template/NOTES.txt as required.

Folder Structure

root@node1:~# tree webapp
webapp
|-- Chart.yaml
|-- README.md
|-- prod-values.yaml
|-- templates
|   |-- NOTES.txt
|   |-- _helpers.tpl
|   |-- deployment.yaml
|   `-- service.yaml
`-- values.yaml

1 directory, 8 files

Dry-run (get the final output that would be sent to Kubernetes API Server)

helm template --debug webapp -f webapp/values.yaml

helm template --debug webapp -f webapp/prod-values.yaml

Install

helm install webapp-demo webapp/ -f webapp/values.yaml

NAME: webapp-demo
LAST DEPLOYED: Sat Feb 20 17:54:37 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None

Test - `Nginx` Welcome Page

export NODE_PORT=$(kubectl get --namespace default -o jsonpath="{.spec.ports[0].nodePort}" services app-svc }})
export NODE_IP=$(kubectl get nodes --namespace default -o jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT

curl http://$NODE_IP:$NODE_PORT

Upgrade

helm upgrade webapp-demo webapp/ -f webapp/prod-values.yaml

Release "webapp-demo" has been upgraded. Happy Helming!
NAME: webapp-demo
LAST DEPLOYED: Sat Feb 20 17:56:00 2021
NAMESPACE: default
STATUS: deployed
REVISION: 2
TEST SUITE: None

Test - `HTTPD` Welcome Page

export NODE_PORT=$(kubectl get --namespace default -o jsonpath="{.spec.ports[0].nodePort}" services app-svc }})
export NODE_IP=$(kubectl get nodes --namespace default -o jsonpath="{.items[0].status.addresses[0].address}")
echo http://$NODE_IP:$NODE_PORT

curl http://$NODE_IP:$NODE_PORT

Rollback

helm ls

NAME            NAMESPACE       REVISION        UPDATED                                 STATUS          CHART                   APP VERSION
webapp-demo     default         2               2021-02-20 17:56:00.166067482 +0000 UTC deployed        hello-helm-0.1.0        latest

helm rollback webapp-demo 1

Rollback was a success! Happy Helming!

Delete

helm delete webapp-demo

sidd-harth/helm