Deployment with Helm Charts

Deployment with Helm

Helm is a package manager for Kubernetes same as yum/rpm for RHEL.

Helm has below capabilities :-

• Install software.
• Automatically install software dependencies.
• Upgrade software.
• Configure software deployments.
• Fetch software packages from repositories.

Download for https://github.com/helm/helm/releases  

It has two binary : helm and tiller

• HELM is client which can create Helm chart as well install them. 
• TILLER is server which runs inside the k8s cluster as pod.

TILLER

Tiller is server which runs as pod and mange helm installation

Installation 

Create new project (Or use existing ) for tiller project.

Download below YAML

https://github.com/openshift/origin/raw/master/examples/helm/tiller-template.yaml 

Set TILLER_NAMESPACE to project name and install tiller as below command.

oc process -f tiller-template.yaml -p TILLER_NAMESPACE="${TILLER_NAMESPACE}" -p HELM_VERSION=v2.14.2| oc create -f –

Add permission for deployment ( Tiller service account in Tiller installation must have the cluser-admin role) 

oc policy add-role-to-user edit "system:serviceaccount:${TILLER_NAMESPACE}:tiller"

To validate command is :-  

oc get sa

TILLER Repo

Tiller repo is location where all Helm packages are present. 

Few well known opensource example

• ChartMuseum https://chartmuseum.com/ 
• JFrog Artifactory https://www.jfrog.com/confluence/display/RTF/Helm+Chart+Repositories 
• Git hub

Apart from repo can be set by using any local web server like apache web server / nginx

Configuration

For sample below we setup AHS 

Run helm as client only (No Internet access then use --skip-refresh and remove stable)

            helm init --client-only --skip-refresh

            helm repo remove stable 

# this will remove repo coming from https://kubernetes-charts.storage.googleapis.com. 

Install Apache and add the URL to HELM repo by below command.

           helm repo add gaurav http://gauravw:8080/

validate it as below

         helm repo list

Creating Helm Chart 

Helm usage Charts as packaging format
For creating chart run below command

helm create microserivce

This will create directory structure like below

charts/  :-       A directory containing any charts upon which this chart templates/   : A directory of templates that, when combined with values,   will generate valid Kubernetes manifest files. Chart.yaml :- A YAML file containing information about the chart values.yaml  :- The default configuration values for this chart  depends.

Chart.yaml

This file contains basic details for helm charts like chart name and version.

             cat microservice/Chart.yaml

                          apiVersion: v1  # Its always v1 (default same as yaml)

                          appVersion: "1.0“  # [Optional] for applicaton version

                          description: A Helm chart for Kubernetes  # Description of application

                          name: microservice   # Name of Chart.

                           version: 0.1.0  # Version of Chart. 

templates/  : Directory contain templates for all deployables.

It should be delete and created based on need.

            rm -f templates/*

By default it contains below files and should be deleted before creating own application

deployment.yaml  : Deplyments template with image and other details

_helpers.tpl  : for partial module

ingress.yaml  : Ingress template

NOTES.txt  : Notes

serviceaccount.yaml  : Create service account

               service.yaml  : Create service


Below is sample yaml file which can create tomcat pod while running command

On OpenShift : 
              oc create -f  tomcat-pod.yaml                     
On vanila Kuberenetes

             kubectl apply -f  tomcat-pod.yaml

Values.yaml

This file makes helm charts dynamic. On this file we set values for variables which can be used in templates. 

Below is sample where we replace values with variables.

as example we define .Values.image.name in values.yaml file as tomcat which replace while installation.

Packaging Helm Chart

To package run command 

                     helm package <Chart> 

Validation commands: 

                     helm lint <Chart>

                     helm inspect <Chart>

                     helm install --dry-run --debug <Chart>

Adding package to Helm Repo

Once package created simply copy file to repo 

For apache its under apache home (/var/www/html) 

And reindex the repo by running below command.

                     helm repo index  /var/www/html --url http://gauravw:8080/

And refresh repo to use them

             helm repo update

Installing Helm Chart.

Once package added to repo it can be installed by below command.

                      helm install microservice

This will install microsevice on K8s / openshift.