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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.

Building Kubernetes

Official releases are built using Docker containers. To build Kubernetes using Docker please follow these instructions.

Go development environment

Kubernetes is written in the Go programming language. To build Kubernetes without using Docker containers, you'll need a Go development environment. Builds for Kubernetes 1.0 - 1.2 require Go version 1.4.2. Builds for Kubernetes 1.3 and higher require Go version 1.6.0. If you haven't set up a Go development environment, please follow these instructions to install the go tools and set up a GOPATH.

To build Kubernetes using your local Go development environment (generate linux binaries):

    hack/build-go.sh

You may pass build options and packages to the script as necessary. To build binaries for all platforms:

    hack/build-cross.sh

Workflow

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 the pre-commit hook into your .git directory. This will keep you from accidentally committing non-gofmt'd Go code. This hook will also do a build and test whether documentation generation scripts need to be executed.

The hook requires both Godep and etcd on your PATH.

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 vendor/ tree, and is required by a number of the build and test scripts. Please make sure that godep is installed and in your $PATH, and that godep version says it is at least v63.

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

Note: At this time, godep version >= v63 is known to work in the Kubernetes project

To check your version of godep:

$ godep version
godep v66 (linux/amd64/go1.6.2)

If it is not a valid version try, make sure you have updated the godep repo with go get -u github.com/tools/godep.

Using godep

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

  1. Devote a directory to this endeavor:

Devoting a separate directory is not strictly 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 $KPATH/src/k8s.io/kubernetes
git clone https://path/to/your/fork .
# Or copy your existing local repo here. IMPORTANT: making a symlink doesn't work.
  1. Set up your GOPATH.
# This will *not* let your local builds see packages that exist elsewhere on your system.
export GOPATH=$KPATH
  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 is simple (if a bit slow):

cd $KPATH/src/k8s.io/kubernetes
DEP=example.com/path/to/dependency
godep get $DEP/...
# Now change code in Kubernetes to use the dependency.
./hack/godep-save.sh

To update an existing dependency is a bit more complicated. Godep has an update command, but none of us can figure out how to actually make it work. Instead, this procedure seems to work reliably:

cd $KPATH/src/k8s.io/kubernetes
DEP=example.com/path/to/dependency
# NB: For the next step, $DEP is assumed be the repo root.  If it is actually a
# subdir of the repo, use the repo root here.  This is required to keep godep
# from getting angry because `godep restore` left the tree in a "detached head"
# state.
rm -rf $KPATH/src/$DEP # repo root
godep get $DEP/...
# Change code in Kubernetes, if necessary.
rm -rf Godeps
rm -rf vendor
./hack/godep-save.sh
git co -- $(git st -s | grep "^ D" | awk '{print $2}' | grep ^Godeps)

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 is unusual, but has been observed.

After all of this is done, git status should show you what files have been modified and added/removed. Make sure to git add and git rm them. It is commonly advised to make one git commit which includes just the dependency update and Godeps files, and another git commit that includes changes to Kubernetes code to use the new/updated dependency. These commits can go into a single pull request.

  1. Before sending your PR, it's a good idea to sanity check that your Godeps.json file and the contents of vendor/ are 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 hack/godep-save.sh to pick up the transitive dependency changes.

It is sometimes expedient to manually fix the /Godeps/Godeps.json file to minimize the changes. However without great care this can lead to failures with hack/verify-godeps.sh. This must pass for every PR.

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

Testing

Three basic commands let you run unit, integration and/or e2e tests:

cd kubernetes
hack/test-go.sh  # Run unit tests
hack/test-integration.sh  # Run integration tests, requires etcd
go run hack/e2e.go -v --build --up --test --down  # Run e2e tests

See the testing guide for additional information and scenarios.

Regenerating the CLI documentation

hack/update-generated-docs.sh

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