kubernetes/docs/devel/development.md

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<h2>PLEASE NOTE: This document applies to the HEAD of the source tree</h2>

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

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<strong>
The latest release of this document can be found
[here](http://releases.k8s.io/release-1.3/docs/devel/development.md).

Documentation for other releases can be found at
[releases.k8s.io](http://releases.k8s.io).
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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](http://releases.k8s.io/HEAD/build/README.md).

### Local OS/shell environment

Many of the Kubernetes development helper scripts rely on a fairly up-to-date GNU tools
environment, so most recent Linux distros should work just fine
out-of-the-box.  Note that Mac OS X ships with somewhat outdated
BSD-based tools, some of which may be incompatible in subtle ways, so we recommend
[replacing those with modern GNU tools](https://www.topbug.net/blog/2013/04/14/install-and-use-gnu-command-line-tools-in-mac-os-x/).

### Go development environment

Kubernetes is written in the [Go](http://golang.org) 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](http://golang.org/doc/code.html) to install the go tools and set
up a GOPATH.

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

```sh
        make
```

You may pass build options and packages to the script as necessary. For example,
to build with optimizations disabled for enabling use of source debug tools:

```sh
        make GOGCFLAGS="-N -l"
```

To build binaries for all platforms:

```sh
        make cross
```

### How to update the Go version used to test & build k8s

The kubernetes project tries to stay on the latest version of Go so it can
benefit from the improvements to the language over time and can easily
bump to a minor release version for security updates.

Since kubernetes is mostly built and tested in containers, there are a few
unique places you need to update the go version.

- The image for cross compiling in [build/build-image/cross/](../../build/build-image/cross/). The `VERSION` file and `Dockerfile`.
- The jenkins test-image in
  [hack/jenkins/test-image/](../../hack/jenkins/test-image/). The `Dockerfile` and `Makefile`.
- The docker image being run in [hack/jenkins/dockerized-e2e-runner.sh](../../hack/jenkins/dockerized-e2e-runner.sh) and [hack/jenkins/gotest-dockerized.sh](../../hack/jenkins/gotest-dockerized.sh).
- The cross tag `KUBE_BUILD_IMAGE_CROSS_TAG` in [build/common.sh](../../build/common.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](git_workflow.png)

### 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](https://golang.org/doc/code.html#GOPATH)). 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`.

```sh
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

```sh
git checkout -b myfeature
# Make your code changes
```

### Keeping your development fork in sync

```sh
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:

```sh
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`.

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

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

```sh
git commit
git push -f origin myfeature
```

### Creating a pull request

1. Visit https://github.com/$YOUR_GITHUB_USERNAME/kubernetes
2. Click the "Compare & pull request" button next to your "myfeature" branch.
3. Check out the pull request [process](pull-requests.md) 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](faster_reviews.md) for more details.

## godep and dependency management

Kubernetes uses [godep](https://github.com/tools/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](http://mercurial.selenic.com/wiki/Download) 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](http://brew.sh) on OS X, or download directly
from mercurial.

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

```sh
export GOPATH=$HOME/go-tools
mkdir -p $GOPATH
go get -u github.com/tools/godep
```

3) Add this $GOPATH/bin to your path. Typically you'd add this to your ~/.profile:

```sh
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:

```sh
$ 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](https://github.com/tools/godep).

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._

```sh
export KPATH=$HOME/code/kubernetes
mkdir -p $KPATH/src/k8s.io
cd $KPATH/src/k8s.io
git clone https://github.com/$YOUR_GITHUB_USERNAME/kubernetes.git # assumes your fork is 'kubernetes'
# Or copy your existing local repo here. IMPORTANT: making a symlink doesn't work.
```

2) Set up your GOPATH.

```sh
# This will *not* let your local builds see packages that exist elsewhere on your system.
export GOPATH=$KPATH
```

3) Populate your new GOPATH.

```sh
cd $KPATH/src/k8s.io/kubernetes
godep restore
```

4) Next, you can either add a new dependency or update an existing one.

To add a new dependency is simple (if a bit slow):

```sh
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:

```sh
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.

5) 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.

6) 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:

```sh
cd kubernetes
make test # Run every unit test
make test WHAT=pkg/util/cache GOFLAGS=-v # Run tests of a package verbosely
make test-integration # Run integration tests, requires etcd
make test-e2e # Run e2e tests
```

See the [testing guide](testing.md) and [end-to-end tests](e2e-tests.md) for additional information and scenarios.

## Regenerating the CLI documentation

```sh
hack/update-generated-docs.sh
```




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