distribution/docs/building.md

# Build the development environment

The first prequisite of properly building distribution targets is to have a Go
development environment setup. Please follow [How to Write Go Code](https://golang.org/doc/code.html)
for proper setup. If done correctly, you should have a GOROOT and GOPATH set in the
environment.

If a Go development environment is setup, one can use `go get` to install the
`registry` command from the current latest:

```sh
go get github.com/docker/distribution/cmd/registry
```

The above will install the source repository into the `GOPATH`. The `registry`
binary can then be run with the following:

```
$ $GOPATH/bin/registry -version
$GOPATH/bin/registry github.com/docker/distribution v2.0.0-alpha.1+unknown
```

> __NOTE:__ While you do not need to use `go get` to checkout the distribution
> project, for these build instructions to work, the project must be checked
> out in the correct location in the `GOPATH`. This should almost always be
> `$GOPATH/src/github.com/docker/distribution`.

The registry can be run with the default config using the following
incantantation:

```
$ $GOPATH/bin/registry $GOPATH/src/github.com/docker/distribution/cmd/registry/config.yml
INFO[0000] endpoint local-8082 disabled, skipping        app.id=34bbec38-a91a-494a-9a3f-b72f9010081f version=v2.0.0-alpha.1+unknown
INFO[0000] endpoint local-8083 disabled, skipping        app.id=34bbec38-a91a-494a-9a3f-b72f9010081f version=v2.0.0-alpha.1+unknown
INFO[0000] listening on :5000                            app.id=34bbec38-a91a-494a-9a3f-b72f9010081f version=v2.0.0-alpha.1+unknown
INFO[0000] debug server listening localhost:5001
```

If it is working, one should see the above log messages.

### Repeatable Builds

For the full development experience, one should `cd` into
`$GOPATH/src/github.com/docker/distribution`. From there, the regular `go`
commands, such as `go test`, should work per package (please see
[Developing](#developing) if they don't work).

A `Makefile` has been provided as a convenience to support repeatable builds.
Please install the following into `GOPATH` for it to work:

```
go get github.com/tools/godep github.com/golang/lint/golint
```

**TODO(stevvooe):** Add a `make setup` command to Makefile to run this. Have to think about how to interact with Godeps properly.

Once these commands are available in the `GOPATH`, run `make` to get a full
build:

```
$ GOPATH=`godep path`:$GOPATH make
+ clean
+ fmt
+ vet
+ lint
+ build
github.com/docker/docker/vendor/src/code.google.com/p/go/src/pkg/archive/tar
github.com/Sirupsen/logrus
github.com/docker/libtrust
...
github.com/yvasiyarov/gorelic
github.com/docker/distribution/registry/handlers
github.com/docker/distribution/cmd/registry
+ test
...
ok    github.com/docker/distribution/digest 7.875s
ok    github.com/docker/distribution/manifest 0.028s
ok    github.com/docker/distribution/notifications  17.322s
?     github.com/docker/distribution/registry [no test files]
ok    github.com/docker/distribution/registry/api/v2  0.101s
?     github.com/docker/distribution/registry/auth  [no test files]
ok    github.com/docker/distribution/registry/auth/silly  0.011s
...
+ /Users/sday/go/src/github.com/docker/distribution/bin/registry
+ /Users/sday/go/src/github.com/docker/distribution/bin/registry-api-descriptor-template
+ /Users/sday/go/src/github.com/docker/distribution/bin/dist
+ binaries
```

The above provides a repeatable build using the contents of the vendored
Godeps directory. This includes formatting, vetting, linting, building,
testing and generating tagged binaries. We can verify this worked by running
the registry binary generated in the "./bin" directory:

```sh
$ ./bin/registry -version
./bin/registry github.com/docker/distribution v2.0.0-alpha.2-80-g16d8b2c.m
```

### Developing

The above approaches are helpful for small experimentation. If more complex
tasks are at hand, it is recommended to employ the full power of `godep`.

The Makefile is designed to have its `GOPATH` defined externally. This allows
one to experiment with various development environment setups. This is
primarily useful when testing upstream bugfixes, by modifying local code. This
can be demonstrated using `godep` to migrate the `GOPATH` to use the specified
dependencies. The `GOPATH` can be migrated to the current package versions
declared in `Godeps` with the following command:

```sh
godep restore
```

> **WARNING:** This command will checkout versions of the code specified in
> Godeps/Godeps.json, modifying the contents of `GOPATH`. If this is
> undesired, it is recommended to create a workspace devoted to work on the
> _Distribution_ project.

With a successful run of the above command, one can now use `make` without
specifying the `GOPATH`:

```sh
$ make
```

If that is successful, standard `go` commands, such as `go test` should work,
per package, without issue.