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65 lines
2.3 KiB
65 lines
2.3 KiB
# The Kubernetes Helm Architecture
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This document describes the Helm architecture at a high level.
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## The Purpose of Helm
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Helm is a tool for managing Kubernetes packages called _charts_. Helm
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can do the following:
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- Create new charts from scratch
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- Package charts into chart archive (tgz) files
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- Interact with chart repositories where charts are stored
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- Install and uninstall charts into an existing Kubernetes cluster
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- Manage the release cycle of charts that have been installed with Helm
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For Helm, there are three important concepts:
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1. The _chart_ is a bundle of information necessary to create an
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instance of a Kubernetes application.
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2. The _config_ contains configuration information that can be merged
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into a packaged chart to create a releasable object.
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3. A _release_ is a running instance of a _chart_, combined with a
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specific _config_.
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## Components
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Helm has two major components:
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**The Helm Client** is a command-line client for end users. The client
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is responsible for the following domains:
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- Local chart development
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- Managing repositories
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- Interacting with the Tiller server
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- Sending charts to be installed
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- Asking for information about releases
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- Requesting upgrading or uninstalling of existing releases
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**The Tiller Server** is an in-cluster server that interacts with the
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Helm client, and interfaces with the Kubernetes API server. The server
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is responsible for the following:
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- Listening for incoming requests from the Helm client
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- Combining a chart and configuration to build a release
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- Installing charts into Kubernetes, and then tracking the subsequent
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release
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- Upgrading and uninstalling charts by interacting with Kubernetes
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In a nutshell, the client is responsible for managing charts, and the
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server is responsible for managing releases.
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## Implementation
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The Helm client is written in the Go programming language, and uses the
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gRPC protocol suite to interact with the Tiller server.
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The Tiller server is also written in Go. It provides a gRPC server to
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connect with the client, and it uses the Kubernetes client library to
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communicate with Kubernetes. Currently, that library uses REST+JSON.
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The Tiller server stores information in ConfigMaps located inside of
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Kubernetes. It does not need its own database.
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Configuration files are, when possible, written in YAML.
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