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helm/docs/developers.md

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Developers Guide

This guide explains how to set up your environment for developing on Helm and Tiller.

Prerequisites

  • Go 1.6.0 or later
  • Glide 0.12.0 or later
  • kubectl 1.2 or later
  • A Kubernetes cluster (optional)
  • The gRPC toolchain

Building Helm/Tiller

We use Make to build our programs. The simplest way to get started is:

$ make bootstrap build

This will build both Helm and Tiller. make bootstrap will attempt to install certain tools if they are missing.

To run all of the tests (without running the tests for vendor/), run make test.

To run Helm and Tiller locally, you can run bin/helm or bin/tiller.

  • Helm and Tiller are known to run on Mac OSX and most Linuxes, including Alpine.
  • Tiller must have access to a Kubernets cluster. It learns about the cluster by examining the Kube config files that kubectl uses.

gRPC and Protobuf

Helm and Tiller communicate using gRPC. To get started with gRPC, you will need to...

  • Install protoc for compiling protobuf files. Releases are here
  • Run Helm's make bootstrap to generate the protoc-gen-go plugin and place it in bin/.

Note that you need to be on protobuf 3.x (protoc --version). The version of protoc-gen-go is tied to the version of gRPC used in Kubernetes. So the plugin is maintained locally.

While the gRPC and ProtoBuf specs remain silent on indentation, we require that the indentation style matches the Go format specification. Namely, protocol buffers should use tab-based indentation and rpc declarations should follow the style of Go function declarations.

The Helm API (HAPI)

We use gRPC as an API layer. See pkg/proto/hapi for the generated Go code, and _proto for the protocol buffer definitions.

To regenerate the Go files from the protobuf source, make protoc.

Docker Images

To build Docker images, use make docker-build.

Pre-build images are already available in the official Kubernetes Helm GCR registry.

Running a Local Cluster

For development, we highly recommend using the Kubernetes Minikube developer-oriented distribution. Once this is installed, you can use helm init to install into the cluster.

For developing on Tiller, it is sometimes more expedient to run Tiller locally instead of packaging it into an image and running it in-cluster. You can do this by telling the Helm client to us a local instance.

$ make build
$ bin/tiller

And to configure the Helm client, use the --host flag or export the HELM_HOST environment variable:

$ export HELM_HOST=localhost:44134
$ helm install foo

(Note that you do not need to use helm init when you are running Tiller directly)

Tiller should run on any >= 1.3 Kubernetes cluster.

Contribution Guidelines

We welcome contributions. This project has set up some guidelines in order to ensure that (a) code quality remains high, (b) the project remains consistent, and (c) contributions follow the open source legal requirements. Our intent is not to burden contributors, but to build elegant and high-quality open source code so that our users will benefit.

Make sure you have read and understood the main CONTRIBUTING guide:

https://github.com/kubernetes/helm/blob/master/CONTRIBUTING.md

Structure of the Code

The code for the Helm project is organized as follows:

  • The individual programs are located in cmd/. Code inside of cmd/ is not designed for library re-use.
  • Shared libraries are stored in pkg/.
  • The raw ProtoBuf files are stored in _proto/hapi (where hapi stands for the Helm Application Programming Interface).
  • The Go files generated from the proto definitions are stored in pkg/proto.
  • The scripts/ directory contains a number of utility scripts. Most of these are used by the CI/CD pipeline.
  • The rootfs/ folder is used for Docker-specific files.
  • The docs/ folder is used for documentation and examples.

Go dependencies are managed with Glide and stored in the vendor/ directory.

Git Conventions

We use Git for our version control system. The master branch is the home of the current development candidate. Releases are tagged.

We accept changes to the code via GitHub Pull Requests (PRs). One workflow for doing this is as follows:

  1. Go to your $GOPATH/k8s.io directory and git clone the github.com/kubernetes/helm repository.
  2. Fork that repository into your GitHub account
  3. Add your repository as a remote for $GOPATH/k8s.io/helm
  4. Create a new working branch (git checkout -b feat/my-feature) and do your work on that branch.
  5. When you are ready for us to review, push your branch to GitHub, and then open a new pull request with us.

For Git commit messages, we follow the Semantic Commit Messages:

fix(helm): add --foo flag to 'helm install'

When 'helm install --foo bar' is run, this will print "foo" in the
output regardless of the outcome of the installation.

Closes #1234

Common commit types:

  • fix: Fix a bug or error
  • feat: Add a new feature
  • docs: Change documentation
  • test: Improve testing

Common scopes:

  • helm: The Helm CLI
  • tiller: The Tiller server
  • proto: Protobuf definitions
  • pkg/lint: The lint package. Follow a similar convention for any package
  • *: two or more scopes

Read more:

  • The Deis Guidelines were the inspiration for this section.
  • Karma Runner defines the semantic commit message idea.

Go Conventions

We follow the Go coding style standards very closely. Typically, running go fmt will make your code beautiful for you.

We also typically follow the conventions recommended by go lint and gometalinter. Run make test-style to test the style conformance.

Read more:

Protobuf Conventions

Because this project is largely Go code, we format our Protobuf files as closely to Go as possible. There are currently no real formatting rules or guidelines for Protobuf, but as they emerge, we may opt to follow those instead.

Standards:

  • Tabs for indentation, not spaces.
  • Spacing rules follow Go conventions (curly braces at line end, spaces around operators).

Conventions:

  • Files should specify their package with option go_package = "...";
  • Comments should translate into good Go code comments (since protoc copies comments into the destination source code file).
  • RPC functions are defined in the same file as their request/response messages.
  • Deprecated RPCs, messages, and fields are marked deprecated in the comments (// UpdateFoo DEPRECATED updates a foo.).