Getting started with Helm on Kubernetes

Deploying applications to Kubernetes – the powerful and popular container-orchestration system – can be complex. Setting up a single application can involve creating multiple interdependent Kubernetes resources – such as pods, services, deployments, and replicasets – each requiring you to write a detailed YAML manifest file.

Helm is a package manager for Kubernetes that allows developers and operators to more easily package, configure, and deploy applications and services onto Kubernetes clusters.

Helm is the first application package manager running atop Kubernetes. It allows describing the application structure through convenient helm-charts and managing it with simple commands.

Why is Helm important? 

Because it’s a huge shift in the way the server-side applications are defined, stored and managed. Adoption of Helm might well be the key to mass adoption of microservices, as using this package manager simplifies their management greatly.

Helm charts are built atop Kubernetes and benefit from its cluster architecture. The main benefit of this approach is the ability to consider scalability from the start. The charts of all the images used by Helm are stored in a registry called Helm Workspace, so the DevOps teams can search them and add to their projects with ease.

Helm is a tool for managing Kubernetes charts. Charts are packages of pre-configured Kubernetes resources. 

Use Helm to:

• Find and use popular software packaged as Helm charts to run in Kubernetes
• Share your own applications as Helm charts
• Create reproducible builds of your Kubernetes applications
• Intelligently manage your Kubernetes manifest files
• Manage releases of Helm packages

Helm is a tool that streamlines installing and managing Kubernetes applications.

• Helm has two parts: a client (helm) and a server (tiller).
• Tiller runs inside of your Kubernetes cluster, and manages releases (installations) of your charts.
• Helm runs on your laptop, CI/CD, or wherever you want it to run.
• Charts are Helm packages that contain at least two things:
  • A description of the package (Chart.yml)
  • One or more templates, which contain Kubernetes manifest files
• Charts can be stored on disk, or fetched from remote chart repositories (like Debian or RedHat packages)

Charts

Helm packages are called charts, and they consist of a few YAML configuration files and some templates that are rendered into Kubernetes manifest files. Here is the basic directory structure of a chart:

Example chart directory

package-name/

  charts/

  templates/

  Chart.yaml

  LICENSE

  README.md

  requirements.yaml

  values.yaml

These directories and files have the following functions:

• charts/: Manually managed chart dependencies can be placed in this directory, though it is typically better to use requirements.yaml to dynamically link dependencies.

• templates/: This directory contains template files that are combined with configuration values (from values.yaml and the command line) and rendered into Kubernetes manifests. The templates use the Go programming language's template format.

• Chart.yaml: A YAML file with metadata about the chart, such as chart name and version, maintainer information, a relevant website, and search keywords.

• LICENSE: A plaintext license for the chart.

• README.md: A readme file with information for users of the chart.

• requirements.yaml: A YAML file that lists the chart's dependencies.

• values.yaml: A YAML file of default configuration values for the chart.

The helm command can install a chart from a local directory, or from a .tar.gz packaged version of this directory structure. These packaged charts can also be automatically downloaded and installed from chart repositories or repos.

Pre-requisites

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1. Kubernetes Cluster

Installing Helm

Download helm tar file

#####################

master $ wget https://get.helm.sh/helm-v2.14.1-linux-386.tar.gz

Untar zip file
############

master $ tar -xvf helm-v2.14.1-linux-386.tar.gz

Move helm binary from extracted directory to /usr/bin/

############################################

master $ mv helm /usr/bin/

Initialize the tiller on kubernetes master

###############################

master $ helm init

Creating helm chart

#######################

master $ helm create hello

Creating hello

Edit values.yml file as below

##########################

Replace repository in image as per your application image and add tag as per your image tag as below:

master $ vim values.yaml

replicaCount: 1

image:

 repository: shashanksr/myapp

 tag: latest

 pullPolicy: IfNotPresent

service:

 type: ClusterIP

 port: 80

Note: This application service will run on ClusterIP not on NodePort

Install your Hello app

##################

master $ helm install hello/

Check kubernetes pods & service

##############################

master $ kubectl get pods

NAME                                    READY STATUS RESTARTS AGE

lovely-whippet-hello-6568cf6554-5crkv   1/1 Running 0 10m

master $ kubectl get svc

NAME                   TYPE CLUSTER-IP      EXTERNAL-IP PORT(S) AGE

kubernetes             ClusterIP 10.96.0.1      <none> 443/TCP 50m

lovely-whippet-hello   ClusterIP 10.108.244.226   <none> 80/TCP 11m

Check helm release and status

###############################

master $ helm ls

NAME            REVISION UPDATED                         STATUS CHART APP VERSION NAMESPACE

lovely-whippet  1 Tue Jun 11 09:59:48 2019        DEPLOYED hello-0.1.0 1.0 default

master $ helm status lovely-whippet

LAST DEPLOYED: Tue Jun 11 09:59:48 2019

NAMESPACE: default

STATUS: DEPLOYED

Run the necessary commands as given above

########################################

master $ export POD_NAME=$(kubectl get pods --namespace default -l "app=hello,release=

lovely-whippet" -o jsonpath="{.items[0].metadata.name}")

master $ echo $POD_NAME

lovely-whippet-hello-6568cf6554-5crkv

master $ echo "Visit http://127.0.0.1:8080 to use your application"

Visit http://127.0.0.1:8080 to use your application

Forward port as below before curl your application

##########################################

master $ kubectl port-forward $POD_NAME 8080:80

Forwarding from 127.0.0.1:8080 -> 80

Forwarding from [::1]:8080 -> 80

Handling connection for 8080

Curl your website with the local IP in a new terminal

##########################################

master $ curl http://127.0.0.1:8080

Welcome to IBM Cloud DevOps with Docker, Kubernetes and Helm Charts. Lets go use the Continuous Delivery Servicemaster