Helm Architecture

The Kubernetes Helm Architecture

This document describes the Helm architecture at a high level.

The Purpose of Helm

Helm is a tool for managing Kubernetes packages called charts. Helm can do thefollowing:

Create new charts from scratch
Package charts into chart archive (tgz) files
Interact with chart repositories where charts are stored
Install and uninstall charts into an existing Kubernetes cluster
Manage the release cycle of charts that have been installed with HelmFor Helm, there are three important concepts:
The chart is a bundle of information necessary to create an instance of aKubernetes application.
The config contains configuration information that can be merged into apackaged chart to create a releasable object.
A release is a running instance of a chart, combined with a specificconfig.

Components

Helm is an executable which is implemented into two distinct parts:

The Helm Client is a command-line client for end users. The client isresponsible for the following:

Local chart development
Managing repositories
Managing releases
Interfacing with the Helm library
- Sending charts to be installed
- Requesting upgrading or uninstalling of existing releasesThe Helm Library provides the logic for executing all Helm operations. Itinterfaces with the Kubernetes API server and provides the following capability:
Combining a chart and configuration to build a release
Installing charts into Kubernetes, and providing the subsequent release object
Upgrading and uninstalling charts by interacting with KubernetesThe standalone Helm library encapsulates the Helm logic so that it can beleveraged by different clients.

Implementation

The Helm client and library is written in the Go programming language.

The library uses the Kubernetes client library to communicate with Kubernetes.Currently, that library uses REST+JSON. It stores information in Secrets locatedinside of Kubernetes. It does not need its own database.

Configuration files are, when possible, written in YAML.