Introduction to Helm and Creating your first Helm Chart

Helm is a package manager for Kubernetes. Similar to yum but for Kubernetes. It bundles all related manifests(such as deployment, service, etc.) into a chart. When installing chart, helm creates a release. The helm’s benefits it provide templating, repeatability, reliability, multiple environments, and ease of collaboration.

Installing Helm

$ curl https://raw.githubusercontent.com/helm/helm/master/scripts/get-helm-3 |bash
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 11213  100 11213    0     0  58630      0 --:--:-- --:--:-- --:--:-- 59015
Helm v3.4.1 is available. Changing from version v3.3.4.
Downloading https://get.helm.sh/helm-v3.4.1-linux-amd64.tar.gz
Verifying checksum... Done.
Preparing to install helm into /usr/local/bin 
helm installed into /usr/local/bin/helm

• Verify helm version

$ helm version
version.BuildInfo{Version:"v3.4.1", GitCommit:"c4e74854886b2efe3321e185578e6db9be0a6e29", GitTreeState:"clean", GoVersion:"go1.14.11"}

• To check the current state of helm locally

$ helm env
HELM_BIN="helm"
HELM_CACHE_HOME="/home/cloud_user/.cache/helm"
HELM_CONFIG_HOME="/home/cloud_user/.config/helm"
HELM_DATA_HOME="/home/cloud_user/.local/share/helm"
HELM_DEBUG="false"
HELM_KUBEAPISERVER=""
HELM_KUBEASGROUPS=""
HELM_KUBEASUSER=""
HELM_KUBECONTEXT=""
HELM_KUBETOKEN=""
HELM_MAX_HISTORY="10"
HELM_NAMESPACE="default"
HELM_PLUGINS="/home/cloud_user/.local/share/helm/plugins"
HELM_REGISTRY_CONFIG="/home/cloud_user/.config/helm/registry.json"
HELM_REPOSITORY_CACHE="/home/cloud_user/.cache/helm/repository"
HELM_REPOSITORY_CONFIG="/home/cloud_user/.config/helm/repositories.yaml"
helm use the Kubernetes cluster/host via the config file
~/.kube/configHELM_DATA_HOME="/home/cloud_user/.local/share/helm"
HELM_DEBUG="false"
HELM_KUBEAPISERVER=""
HELM_KUBEASGROUPS=""
HELM_KUBEASUSER=""
HELM_KUBECONTEXT=""
HELM_KUBETOKEN=""
HELM_MAX_HISTORY="10"
HELM_NAMESPACE="default"
HELM_PLUGINS="/home/cloud_user/.local/share/helm/plugins"
HELM_REGISTRY_CONFIG="/home/cloud_user/.config/helm/registry.json"
HELM_REPOSITORY_CACHE="/home/cloud_user/.cache/helm/repository"
HELM_REPOSITORY_CONFIG="/home/cloud_user/.config/helm/repositories.yaml"

• helm use the Kubernetes cluster/host via the config file

~/.kube/config

Advantage of using helm 

• Traditional deployments in Kubernetes is done with Kubectl across files into separately managed items. Helm deploys units called charts as managed releases.
• We can search for charts https://helm.sh/ . Charts can be pulled(downloaded) and optionally unpacked(untar).

Chart Repo

• The location where Helm charts can be stored and shared
• Respond to REST API GET requests to get packages
• Many storage options available — cloud buckets, local storage, GH Pages, etc. or we can use Chartmuseum(open-source helm chart repository).

• To show all the repos

$ helm repo list
NAME URL 
istio.io https://storage.googleapis.com/istio-release/releases/1.4.2/charts/

• To add a repo

helm repo add <repo> url
helm repo add stable https://charts.helm.sh/stable
"stable" has been added to your repositories

• Search a repo

$ helm search repo mysql
NAME                             CHART VERSION APP VERSION DESCRIPTION                                       
stable/mysql                     1.6.7         5.7.30      Fast, reliable, scalable, and easy to use open-...
stable/mysqldump                 2.6.2         2.4.1       DEPRECATED! - A Helm chart to help backup MySQL...
stable/prometheus-mysql-exporter 0.7.1         v0.11.0     DEPRECATED A Helm chart for prometheus mysql ex...
stable/percona                   1.2.1         5.7.26      free, fully compatible, enhanced, open source d...
stable/percona-xtradb-cluster    1.0.6         5.7.19      free, fully compatible, enhanced, open source d...
stable/phpmyadmin                4.3.5         5.0.1       DEPRECATED phpMyAdmin is an mysql administratio...
stable/gcloud-sqlproxy           0.6.1         1.11        DEPRECATED Google Cloud SQL Proxy                 
stable/mariadb                   7.3.14        10.3.22     DEPRECATED Fast, reliable, scalable, and easy t...

• Search in hub

$ helm search hub |head
URL                                                CHART VERSION                         APP VERSION                           DESCRIPTION                                       
https://hub.helm.sh/charts/gabibbo97/389ds         0.1.0                                 fedora-32                             389 Directory Server                              
https://hub.helm.sh/charts/arhatdev/abbot          0.1.0                                 latest                                Network Manager Living at Edge                    
https://hub.helm.sh/charts/restorecommerce/acce... 0.1.2                                 0.1.6                                 A Helm chart for restorecommerce access-control...
https://hub.helm.sh/charts/ckotzbauer/access-ma... 0.4.1                                 0.4.1                                 Kubernetes-Operator to simplify RBAC configurat...
https://hub.helm.sh/charts/a10-prometheus-expor... 0.1.0                                 1.0                                   A Helm chart of A10 acos prometheus exporter fo...
https://hub.helm.sh/charts/k8s-at-home/adguard-... 2.2.0                                 v0.102.0                              DNS proxy as ad-blocker for local network         
https://hub.helm.sh/charts/mogaal/adminer          0.1.0                                 4.7.3                                 A Helm chart for Adminer                          
https://hub.helm.sh/charts/cetic/adminer           0.1.6                                 4.7.7                                 Adminer is a full-featured database management ...
https://hub.helm.sh/charts/graviteeio/ae           1.1.11                                1.2.13                                Official Gravitee.io Helm chart for Alert Engine

Creating your first chart

The easiest way to get started with chart is by using helm create command. The below command creates a new chart named myhelmchart.

helm create myhelmchart
Creating myhelmchart

• If you drill down inside the myhelmchart directory, you will see the structure like this. Let take a look at each of these files/directory one by one

myhelmchart
├── charts
├── Chart.yaml
├── templates
│   ├── deployment.yaml
│   ├── _helpers.tpl
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── NOTES.txt
│   ├── serviceaccount.yaml
│   ├── service.yaml
│   └── tests
│       └── test-connection.yaml
└── values.yaml

templates

Templates are one of the most important directories, and this is where helm looks for your Kubernetes object yaml definitions(Deployment, Services,etc.). 

values.yaml

If templates hold the resource definition, then values provide the way to parameterize it. 

_helpers.tpl

Helm allows the use of Go templating in the resources files for Kubernetes. The _helpers.tpl is used to define Go template helpers.

NOTES.txt

This is the plain text file that gets printed out when the chart is successfully deployed. Usually, this contains the next step for using the chart.

Chart.yaml

This file contains the metadata such as chart version, application version, or constraints like a minimum version of Kubernetes/Helm, which is required to manage this chart. Some required fields in chart.yaml.

Now you understand all the chart structure and all the corresponding files, it’s time to create your first chart. I will start with a simple Nginx application, and later on, we will parameterize it using values.yaml.

Step1: Cleanup all the files inside the templates directory so that we will start from scratch.

rm -rf templates/*

Step2: Create deployment file

kubectl create deployment nginx --image=nginx --dry-run=client -o yaml >> templates/deployment.yaml

Step3: Expose your deployment 

kubectl expose deploy nginx --port 80 --type NodePort --dry-run=client -o yaml > /tmp/service.yaml
Error from server (NotFound): deployments.apps "nginx" not found

Now the catch is that if you try to expose the deployment without creating it, you will encounter this error, fix it, and create deployment temporarily(as we want to deploy it using helm).

kubectl create deployment nginx --image=nginx                                                      
deployment.apps/nginx created

kubectl expose deploy nginx --port 80 --type NodePort --dry-run=client -o yaml > templates/service.yaml

As this my first chart, I want to keep it bare bone and define only the required values inside chart.yaml.

cat Chart.yaml               
apiVersion: v2
name: myhelmchart
description: A Helm chart for Kubernetes
version: 0.1.0

• One more additional file I need to create is NOTES.txt inside the templates directory.

echo "This is first helm chart and it will deploy nginx application" >>templates/NOTES.txt

• I also cleanup rest of the files and directory to draw the clean slate

rm -rf values.yaml charts

Deploying your first chart

With all the config in place, it’s time to deploy the first helm chart. We can also set the release name so that we can refer it back at the later stages. 

• It is always a good idea to run linter before deploying your chart to ensure there is no syntax error or follow all the best practices.

helm lint ./myhelmchart 
==> Linting ./myhelmchart
[INFO] Chart.yaml: icon is recommended
[INFO] values.yaml: file does not exist

1 chart(s) linted, 0 chart(s) failed

• Let’s now start with a dry-run to make sure everything looks good

helm install demochart ./myhelmchart --dry-run
NAME: demochart
LAST DEPLOYED: Thu Feb  4 09:46:19 2021
NAMESPACE: default
STATUS: pending-install
REVISION: 1
TEST SUITE: None
HOOKS:
MANIFEST:
---
# Source: myhelmchart/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 80
  selector:
    app: nginx
  type: NodePort
status:
  loadBalancer: {}
---
# Source: myhelmchart/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        resources: {}
status: {}

NOTES:
This is first helm chart and it will deploy nginx application

• If things good deploy your helm chart without dry-run option

helm install demochart ./myhelmchart          
NAME: demochart
LAST DEPLOYED: Thu Feb  4 09:47:56 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
This is first helm chart and it will deploy nginx application

• To verify it

helm list                           
NAME      NAMESPACE REVISION UPDATED                                 STATUS   CHART             APP VERSION
demochart default   1        2021-02-04 09:47:56.949383215 -0800 PST deployed myhelmchart-0.1.0

• Or you can access your application via hitting any of the Kubernetes nodes

curl http://172.19.0.2:32544/                  
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

• We have created and deployed our first helm chart; it’s time to parameterize these values using values.yaml. Let target the deployment.yaml and parameterize the image 

templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx
        name: nginx
        resources: {}
status: {}

• But before that how to uninstall your application using helm

helm uninstall demochart
release "demochart" uninstalled

helm list               
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION

• Now go to values.yaml, and add key as imagename and its value as nginx

cat values.yaml              
imagename: nginx

• Now to refer this value, you can specify it via Values and key so it should be like (.Values.imagename)

cat templates/deployment.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    app: nginx
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: nginx
    spec:
      containers:
      - image: {{ .Values.imagename }}
        name: nginx
        resources: {}
status: {}

• We can also bump up the version of helm chart

cat myhelmchart/Chart.yaml   
apiVersion: v2
name: myhelmchart
description: A Helm chart for Kubernetes
version: 0.2.0

• Deploy it again

helm install demochart ./myhelmchart
NAME: demochart
LAST DEPLOYED: Thu Feb  4 10:38:25 2021
NAMESPACE: default
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
This is first helm chart and it will deploy nginx application

Packaging Chart

You have your chart ready at this stage, but if you want to share these charts with your team or the rest of the community. To do that, use the helm package command.

helm package ./myhelmchart      
Successfully packaged chart and saved it to: /home/prashant/Documents/helm/myhelmchart-0.2.0.tgz

• If your teammate need to install this chart, he can do it via helm install

helm install mychart myhelmchart-0.2.0.tgz

Wrapping Up

Helm is a powerful tool, and it greatly simplifies how you package your Kubernetes manifests. I barely scratched the surface in this blog, but if there is any helm feature you liked and want to share with the rest of the community, please mention that in the comment section.