Journey with Helm charts

I have been working on kubernetes, docker and helm charts for quite sometime installing elasticsearch, jaeger and spark applications in kubernetes cluster. despite having been worked, never created a helm chart from the k8s files.

It is getting too much clutter despite the reduction of k8s files moving away from pods, services, deployments, ingress towards Operators. Helm charts seems inevitable to produce our product as one single deployable file with few no. of parameters.

So far i have used helm,
Just 3 steps,
1. Install helm & minikube or point to existing k8s cluster from local
2. Install Helm Repository
3. Install required application 

I use to install helm repo and install applications of required version and configuration.
 
https://hub.helm.sh/ - Wonderful helm repository with all charts required. Just like maven repository for jars.

Post getting familiar with Operators, I happen to install Operators.
https://operatorhub.io/ - Wonderful Operators repository. 

The specialty of Operators is that every application has its own Custom Resource Definition (i.e., provides its own API and plugs it under Kubectl Command line tool once it is installed in our k8s cluster) just like the local machine installation, if we are familiar with the application we can easily handle without going through Kubernetes API.

Life cycle management in Operators is very easy. Helm can also handle lifecycle of application but it can mostly uninstall and install or do compatible upgrades, otherwise for incompatible upgrades & downgrades the custom operators provided by application developers will surpass. Helm can manage Operator life cycle which is going to see less changes unlike real applications.

Today I happen to create my own HELM chart,

Raw Yaml Chart

To create a simple chart, I followed the below guide.

$ helm create mychart
Creating mychart
I remove all the values and templates. I just dropped all my yaml files into templates folder and made a dry run

$ helm install blahblah --dry-run --deploy ./mychart -n somenamespace
All the yaml files just raw once could be installed now with helm command. I only did dry run to check what will be the output. Finished, my chart was ready :)

Templating

I tried to replace only one repeated string in the value and made a template out of it.


template.yaml  (random yaml file in templates)

key: {{ .Values.name }}
values.yaml

name: blahblah
$ helm install blahblah --dry-run --deploy ./mychart -n somenamespace
Done. The value replaced template returned out of the dry run command. 

Control Structures
Now I was in requirement to loop to generate multiple yaml syntaxes. Before that I had conditional execution requirement, I used if and if not constructs in template. 

Looping was little tough, but the below page helped. Initially i was not able to get any clue as helm command did not throw any error pointing the issue what went wrong with the template, it is little frustrating. I came over the frustration by creating another helm chart to try out example given in the link. I did missed out something called as SCOPE of the variables in template with and without $


Loops and Object access with range & with template syntax introduces something called Local Scope, within the envelope of code which the syntax cover. In order to access the Global values present in Values.yaml, we are supposed to make use of $, a way to access global scope.

Everything fell into place

Almost 4 to 5 years ago i used mustache js https://github.com/janl/mustache.js/. Go templates are not very different from it. I happen to used it along with backbone js and angular 1.0.

I have also used angular 2.0, the scoping part of go templates is same it is present in angular.

String manipulations that are required to use in templates of helm are available in below link. I used something called kebabcase :D, the name refers to food dish and someone had named it for purpose and its funny.

Journey Continues

My sojourn to helm world has just started. Below are some interesting spots in helm to visit.

https://helm.sh/docs/topics/charts/ - Lot many things to learn about dependencies in Charts.

https://helm.sh/docs/topics/charts_hooks/ - Just like installation phase of maven, we have phases like pre-install, pre-upgrade, pre-rollback and its post counterpart and test. Hooks available to perform some operation.

https://helm.sh/docs/topics/chart_tests/ - A bit of integration testing, setup, run and disassemble.

https://helm.sh/docs/topics/library_charts/ - Refactoring charts with libraries

https://helm.sh/docs/topics/provenance/ - To transfer artifact securely and with integrity without any loss.


Experimental supports

https://helm.sh/docs/topics/registries/ - OCI instead of tar or zip :) Many people including java is moving away from zips (for jars) towards images.

System

Advanced Users Options

K8S - Many Platforms

User Control

Plugins

SQL Storage

hmmmm... And many many more, an endless list. I am done for the day. 

Comments

Post a Comment

Popular posts from this blog

JavaScript Debut as a Full Fledged Language for Production in the Age of Cloud, Big Data and IoT

Dated: 11-4-2014  "YUI","DHTMLX","JQuery","ProtoType", "GWT" & "DOJO" are few JavaScript Libraries and Frameworks which I will mention, if have been asked to state any. Mostly all the libraries and frameworks mentioned so far are building client end User Interfaces, Widgets and for applying Unobstructed JavaScripting either with CSS selectors as in JQuery or by extending the attribute for decorating the UI elements, i.e., nothing but the HTML Tag elements or XML Tag elements. During the year 2005, AJAX became a hit to bind the user data to the server asynchronously with XML to create Dynamic responsive Web pages. All the above framework do support AJAX for binding data. But, it seems that it has been lately realized irrespective of what kind of UI/Widget being employed on the front end, it has to do nothing but to collect the data from the User and pass it to server, hence data binding seems to have found its importance. I...
Read more

Make Raspberry Pi Independent of Peripheral Devices & Connector Cables

Image
I had posted " Raspberry Pi & DIY IoT " & " Pre-requisites to get started with Raspberry Pi " earlier. This post is a continuation of the series, here we shall investigate how to make Raspberry Pi Independent of peripheral devices & Connector Cables. The Idea here is to make Raspberry Pi portable & mobile and to connect to Raspberry Pi via Remote Connection or Remote Desktop Option. What components are required for making Raspberry Pi Independent of peripheral devices & Connector Cables? we require connector replacements like 1. Wifi USB Adapter. 2. Power Bank / Rechargeable power supply. Experience: I bought 2  WiFi USB Adapters . Actually 1 is enough, I used the other one for my desktop. I have not bought any power bank so far. Still dependent on wired power supply. We will require an another Laptop or Computer to connect with Raspberry Pi as a Remote component. In this post we shall see how to use Wifi Adapter and connect to Laptop/Desktop via...
Read more

Following Java, Exploring Projects JIGSAW and KULLA - Intro

After my last post on  Following Java, Post Java 8 Release , I was able to Introduce  Value Types ,  HTTP 2  to Java Enthusiasts attending  MadrasJUG  Sessions and there by I too learned about them. Value Type Feature has been deferred to Java 10 Version, any way we had a sneak peek. Click  Here  to checkout the list of features proposed for JDK 9. JDK 9 will be hopefully released on 23-Mar-2017. Check Takipi's  page  to see more information on the dates of various phases of JDK development. In  August, 2016 Madras JUG meet , I was able to run few Quick Start Programs of  Project Jigsaw  to learn how Modular JDK is going to look like and how to write Modules in JAVA in Java 9. We also saw how Jshell works and  Project Kulla . Here are Steps to get a Sneak Peek of Modules of JDK 9, 1. Download  JDK 9  EA edition 2. Set JDK bin path in PATH variable and ensure Java version is Java 9 EA version 2. As per...
Read more