shalm

README

Scriptable helm charts

This project brings the starlark scripting language to helm charts.

Features

• Ease orchestration of deployments
• Strict separation of templates and logic
• Define APIs for helm charts
• Control deployment by overriding methods
• Compatible with helm
• Use starlark methods in templates (replacement for _helpers.tpl)
• Interact with kubernetes during installation
• Manage user credentials
• Manage certificates
• Act as glue code between helm charts
• Rendering of ytt templates
• Also available as kubernetes controller
• Easy embeddable and extendable
• Integration of kapp

Installation

Installing shalm can be done in various ways

Architecture

Usage

How to start shalm from the command line is described here

Getting started

There is a small tutorial available.

Tutorial

You can find a small tutorial, which guides you through the basic features here

User Guide

Solutions for a set of problems are shown here

Repos

Shalm can load charts from a various set of locations.

Kubernetes Controller

Shalm can also run as controller inside a kubernets cluster

Reference

A reference for the complete shalm starlark API

Testing

Shalm also supports unit testing

Comparison

	shalm	helm	ytt/kapp	kustomize
Scripting	+	(3.1)	+	-
API definition	+	-	(+)	-
Reuse of existing charts	+	+	(+)	?
Only simple logic in templates	+	+	-	+
Interaction with k8s	+	+	-	-
Repository	+	+	-	-
Mature technology	-	+	+	+
Manage user credentials	+	-	-	-
Manage user certificate	+	-	-	-
Controller based installation	+	-	+	-
Remove outdated objects	+(1)	+	+	-
Migrate existing objects	+(1)	-	-	-

⁽¹⁾: Must be implemented inside apply method or by using kapp as installer.

Difference to helm

• Subcharts are not loaded automatically. They must be loaded using the chart command
• Global variables are not supported.
• The --set command line parameters are passed to the init method of the corresponding chart. It's not possible to set values (from values.yaml) directly. If you would like to set a lot of values, it's more convenient to write a separate shalm chart.
• shalm doesn't track installed charts on a kubernetes cluster (except you are using kapp for deployment). It works more like kubectl apply
• The .Release.Name value is build as follows: <chart.name>-<chart.suffix>. If no suffix is given, the hyphen is also ommited.