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WARNING WARNING WARNING WARNING WARNING

PLEASE NOTE: This document applies to the HEAD of the source tree

If you are using a released version of Kubernetes, you should refer to the docs that go with that version.

The latest release of this document can be found [here](http://releases.k8s.io/release-1.1/docs/devel/development.md).

Documentation for other releases can be found at releases.k8s.io.

Development Guide

This document is intended to be the canonical source of truth for things like supported toolchain versions for building Kubernetes. If you find a requirement that this doc does not capture, please file a bug. If you find other docs with references to requirements that are not simply links to this doc, please file a bug.

This document is intended to be relative to the branch in which it is found. It is guaranteed that requirements will change over time for the development branch, but release branches of Kubernetes should not change.

Releases and Official Builds

Official releases are built in Docker containers. Details are here. You can do simple builds and development with just a local Docker installation. If you want to build go code locally outside of docker, please continue below.

Go development environment

Kubernetes is written in the Go programming language. If you haven't set up a Go development environment, please follow these instructions to install the go tools and set up a GOPATH.

Go versions

Requires Go version 1.4.x or 1.5.x

Git setup

Below, we outline one of the more common git workflows that core developers use. Other git workflows are also valid.

Visual overview

Git workflow

Fork the main repository

  1. Go to https://github.com/kubernetes/kubernetes
  2. Click the "Fork" button (at the top right)

Clone your fork

The commands below require that you have $GOPATH set ($GOPATH docs). We highly recommend you put Kubernetes' code into your GOPATH. Note: the commands below will not work if there is more than one directory in your $GOPATH.

mkdir -p $GOPATH/src/k8s.io
cd $GOPATH/src/k8s.io
# Replace "$YOUR_GITHUB_USERNAME" below with your github username
git clone https://github.com/$YOUR_GITHUB_USERNAME/kubernetes.git
cd kubernetes
git remote add upstream 'https://github.com/kubernetes/kubernetes.git'

Create a branch and make changes

git checkout -b myfeature
# Make your code changes

Keeping your development fork in sync

git fetch upstream
git rebase upstream/master

Note: If you have write access to the main repository at github.com/kubernetes/kubernetes, you should modify your git configuration so that you can't accidentally push to upstream:

git remote set-url --push upstream no_push

Committing changes to your fork

Before committing any changes, please link/copy these pre-commit hooks into your .git directory. This will keep you from accidentally committing non-gofmt'd go code.

cd kubernetes/.git/hooks/
ln -s ../../hooks/pre-commit .

Then you can commit your changes and push them to your fork:

git commit
git push -f origin myfeature

Creating a pull request

  1. Visit https://github.com/$YOUR_GITHUB_USERNAME/kubernetes
  2. Click the "Compare and pull request" button next to your "myfeature" branch.
  3. Check out the pull request process for more details

When to retain commits and when to squash

Upon merge, all git commits should represent meaningful milestones or units of work. Use commits to add clarity to the development and review process.

Before merging a PR, squash any "fix review feedback", "typo", and "rebased" sorts of commits. It is not imperative that every commit in a PR compile and pass tests independently, but it is worth striving for. For mass automated fixups (e.g. automated doc formatting), use one or more commits for the changes to tooling and a final commit to apply the fixup en masse. This makes reviews much easier.

See Faster Reviews for more details.

godep and dependency management

Kubernetes uses godep to manage dependencies. It is not strictly required for building Kubernetes but it is required when managing dependencies under the Godeps/ tree, and is required by a number of the build and test scripts. Please make sure that godep is installed and in your $PATH.

Installing godep

There are many ways to build and host go binaries. Here is an easy way to get utilities like godep installed:

  1. Ensure that mercurial is installed on your system. (some of godep's dependencies use the mercurial source control system). Use apt-get install mercurial or yum install mercurial on Linux, or brew.sh on OS X, or download directly from mercurial.

  2. Create a new GOPATH for your tools and install godep:

export GOPATH=$HOME/go-tools
mkdir -p $GOPATH
go get github.com/tools/godep
  1. Add $GOPATH/bin to your path. Typically you'd add this to your ~/.profile:
export GOPATH=$HOME/go-tools
export PATH=$PATH:$GOPATH/bin

Using godep

Here's a quick walkthrough of one way to use godeps to add or update a Kubernetes dependency into Godeps/_workspace. For more details, please see the instructions in godep's documentation.

  1. Devote a directory to this endeavor:

Devoting a separate directory is not required, but it is helpful to separate dependency updates from other changes.

export KPATH=$HOME/code/kubernetes
mkdir -p $KPATH/src/k8s.io/kubernetes
cd $KPATH/src/k8s.io/kubernetes
git clone https://path/to/your/fork .
# Or copy your existing local repo here. IMPORTANT: making a symlink doesn't work.
  1. Set up your GOPATH.
# Option A: this will let your builds see packages that exist elsewhere on your system.
export GOPATH=$KPATH:$GOPATH
# Option B: This will *not* let your local builds see packages that exist elsewhere on your system.
export GOPATH=$KPATH
# Option B is recommended if you're going to mess with the dependencies.
  1. Populate your new GOPATH.
cd $KPATH/src/k8s.io/kubernetes
godep restore
  1. Next, you can either add a new dependency or update an existing one.
# To add a new dependency, do:
cd $KPATH/src/k8s.io/kubernetes
go get path/to/dependency
# Change code in Kubernetes to use the dependency.
godep save ./...

# To update an existing dependency, do:
cd $KPATH/src/k8s.io/kubernetes
go get -u path/to/dependency
# Change code in Kubernetes accordingly if necessary.
godep update path/to/dependency/...

If go get -u path/to/dependency fails with compilation errors, instead try go get -d -u path/to/dependency to fetch the dependencies without compiling them. This can happen when updating the cadvisor dependency.

  1. Before sending your PR, it's a good idea to sanity check that your Godeps.json file is ok by running hack/verify-godeps.sh

If hack/verify-godeps.sh fails after a godep update, it is possible that a transitive dependency was added or removed but not updated by godeps. It then may be necessary to perform a godep save ./... to pick up the transitive dependency changes.

It is sometimes expedient to manually fix the /Godeps/godeps.json file to minimize the changes.

Please send dependency updates in separate commits within your PR, for easier reviewing.

  1. If you updated the Godeps, please also update Godeps/LICENSES.md by running hack/update-godep-licenses.sh.

If Godep does not automatically vendor the proper license file for a new dependency, be sure to add an exception entry to hack/update-godep-licenses.sh.

Unit tests

cd kubernetes
hack/test-go.sh

Alternatively, you could also run:

cd kubernetes
godep go test ./...

If you only want to run unit tests in one package, you could run godep go test under the package directory. For example, the following commands will run all unit tests in package kubelet:

$ cd kubernetes # step into the kubernetes directory.
$ cd pkg/kubelet
$ godep go test
# some output from unit tests
PASS
ok      k8s.io/kubernetes/pkg/kubelet   0.317s

Coverage

Currently, collecting coverage is only supported for the Go unit tests.

To run all unit tests and generate an HTML coverage report, run the following:

cd kubernetes
KUBE_COVER=y hack/test-go.sh

At the end of the run, an the HTML report will be generated with the path printed to stdout.

To run tests and collect coverage in only one package, pass its relative path under the kubernetes directory as an argument, for example:

cd kubernetes
KUBE_COVER=y hack/test-go.sh pkg/kubectl

Multiple arguments can be passed, in which case the coverage results will be combined for all tests run.

Coverage results for the project can also be viewed on Coveralls, and are continuously updated as commits are merged. Additionally, all pull requests which spawn a Travis build will report unit test coverage results to Coveralls. Coverage reports from before the Kubernetes Github organization was created can be found here.

Integration tests

You need an etcd in your path. To download a copy of the latest version used by Kubernetes, either

  • run hack/install-etcd.sh, which will download etcd to third_party/etcd, and then set your PATH to include third_party/etcd.
  • inspect cluster/saltbase/salt/etcd/etcd.manifest for the correct version, and then manually download and install it to some place in your PATH.
cd kubernetes
hack/test-integration.sh

End-to-End tests

See End-to-End Testing in Kubernetes.

Testing out flaky tests

Instructions here

Benchmarking

To run benchmark tests, you'll typically use something like:

$ godep go test ./pkg/apiserver -benchmem -run=XXX -bench=BenchmarkWatch

The -run=XXX prevents normal unit tests for running, while -bench is a regexp for selecting which benchmarks to run. See go test -h for more instructions on generating profiles from benchmarks.

Regenerating the CLI documentation

hack/update-generated-docs.sh

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