PackagingDrafts/Go

This page is a draft only
It is still under construction and content may change. Do not rely on the information on this page.

Naming

Package Names

The package name idiom for the golang is that the import paths of libraries are fully qualified domain names. This way you have clarity to the precise upstream being used. We'll acknowledge this qualified path in the Provides, but also the package name should indicate the upstream project as much as possible. Truncating domain names and using '-' instead of '/'. For example, 'github.com/gorilla/context' would be 'golang-github-gorilla-context' for the base RPM name. Similarly, the 'code.google.com/p/go.net' repository would be 'golang-googlecode-net' base RPM name.

Import Path

In the golang library paths, are referenced in full URLs. Since this URL is referenced in several places throughout the rpmspec, as a standard, set the base import path as a global define at the top of the spec file

%global go_import_path     code.google.com/p/go.net

Versions

Many Go libraries do not use package versions or have regular releases, and are instead maintained in public version control. In this case, follow the standard Fedora version conventions. This means that often Go packages will have a version number of "0" and a release number like "0.10.git27435c6".

To make that version and release string easier to manage, set global defines for the project's revision (and short revision if needed).

Hashed revisions

For projects that use a hashed version control (git, hg/mecurial), then the defines would look like:

%global rev             84a4013f96e01fdd14b65d260a78b543e3702ee1                
%global shortrev        %(r=%{rev}; echo ${r:0:12})

Then the Release: can be set as:

Release:        0.10.hg%{shortrev}%{?dist}

Numerical revisions

For projects that use a numerical version control (bzr), then the defines would look like:

%global rev             53                

Then the Release: can be set as:

Release:        0.10.bzr%{rev}%{?dist}

Packaging Binaries

Applications that have a 'main' package name, are compiled to a binary. These should be named after the upstream project, and do not need a "golang" prefix.

If that project does also include source libraries, then a subpackage can be produced with the "golang" prefix and Provides: for the import paths that are packaged.

The golang compiler only produces static binaries for all native golang source code. There is a C bridge logic that allows golang source to dynamically linked to C compiled shared objects (e.g. libssl), the the golang compiler can not produce a shared object library. All golang binary packages have an automatic exception to the standard policy.

The GCC-Go compiler by default produces dynamically-linked binaries and is capable of statically linking as well.

At this stage, the reference compiler is the golang compiler, though gccgo is ready for use, and has demonstrated performance benefits for isolated use-cases.

Build ID

The golang compiler (gc) does provide by default the ".note.gnu.build-id" section that GCC does. Though, if the binary being built supports being compiled with gccgo, the gccgo compiler does support and include the .note.gnu.build-id.

Debuginfo

If you are using golang, DWZ is currently incompatible with binaries produced by it (Bug 995136). To get at least partial DWZ optimization use:

# https://bugzilla.redhat.com/show_bug.cgi?id=995136#c12
%global _dwz_low_mem_die_limit 0

If you are using golang, it does not produce build ID by default. Use this compilation command otherwise build ID packaging check would stop the package build:

# *** ERROR: No build ID note found in /.../BUILDROOT/etcd-2.0.0-1.rc1.fc22.x86_64/usr/bin/etcd
function gobuild { go build -a -ldflags "-B 0x$(head -c20 /dev/urandom|od -An -tx1|tr -d ' \n')" -v -x "$@"; }

There is still a bug the *.debug files in *-debuginfo.rpm will have incorrect reference to the source files directory - Bug 1184221.

Dependencies

Most of the golang-* packages are source code only, the *-devel sub-package that includes the source code, should explicitly have provides for the golang imports that it includes. (without single or double quotes) Binary builds that include these imports will use BuildRequires:

BuildRequires: golang(github.com/gorilla/context) >= 0-0.13

Go Language Architectures

The golang compiler currently only supports x86, x86_64, and Arm (32- and 64-bit). Binaries should set ExclusiveArch so that we only attempt to build packages on those arches. The golang package provides the %{go_arches} macro for this:

ExclusiveArch:  %{go_arches}

Packaging Libraries

At this time, Go libraries packaged in Fedora are primarily for the purpose of being BuildRequires for building Fedora binary RPMs, and not meant to be developed against otherwise -- for that, we encourage the upstream "go get" idiom and a per-user $GOPATH.

We do not provide or recommend a system-wide GOPATH that users should inherit and there is no notion of a "site" or "vendor" path for system libriaries.

GOROOT is reserved for golang standard library only. This way developers do not need to be concerned with library path conflicts, but instead can choose to include the system path in their per-user path (e.g. export GOPATH=$HOME/go:/usr/share/gocode). This way a call to go get ... would land new source in the $HOME/go directory

The standard golang compiler only produces static libraries. There is little value in shipping these prebuilt, especially since these libraries are very specifically tied to the exact minor release of the golang compiler. Instead, each library package should consist of a -devel subpackage which installs .go source code to /usr/share/gocode/src, under the appropriate import path.

Binary packages which build against this source will set $GOPATH to '%{_datadir}/gocode' ( or '%{gopath}' in golang > 1.2.1-1)

Shared-object libraries

There has been talk of golang having shared-object libraries at some point, but that is still presently only a discussion [1] and somewhat stale review [2]. Also, presently the shared object libraries produced by GCC-Go are not usable [3].

Neither of these cases are a blocker for supported architectures using cgo to have dynamic links to a C/C++ compiled shared-object library [4].

Dependencies

To match the fully qualified import paths of the projects and source, utilize the meta wrapper / virtual provides in the golang namespace to provide the import paths being packaged.

Most of the golang-* packages are source code only, the *-devel sub-package that includes the source code, should explicitly have provides for the golang imports that it includes. (without single or double quotes)

Provides: golang(%{go_import_path}) = %{version}-%{release}

Then other source packages that reference these imports can have Requires: matching that:

Requires: golang(github.com/gorilla/context)

Libraries and Arch

Because these packages contain no compiled code, they should be made noarch. However, since they require golang, they need to only be built on the architectures supported by the language. For that reason, follow the standard guidelines for noarch packages with unported dependencies:

BuildArch: noarch
ExclusiveArch: %{go_arches} noarch

Security in Go Language Packages

If there is a security issue in the standard Go library or in a library built into binary Go programs, all affected RPMs will need to be rebuilt.

In the event that a security issue is found in a library, all packages which have that library as a BuildRequires must be identified and rebuilt with the version and release of the fixed library added to the BuildRequires.

repoquery -q --disablerepo='*' --enablerepo=fedora-source --enablerepo=updates-source --enablerepo=updates-testing-source --archlist=src --whatrequires 'golang($SOME_IMPORT_PATH)'

Additionally, other golang-*-devel packages may directly require their own dependencies; check for such packages with

repoquery -q --disablerepo='*' --enablerepo=fedora --enablerepo=updates --enablerepo=updates-testing --whatrequires 'golang($SOME_IMPORT_PATH)'

and, if any of the results are golang-*-devel RPMs, repeat the previous step to find packages which may have that as a BuildRequires.

Optional

List of dependencies

Some projects like kubernetes, cadvisor or etcd ship a list of dependencies they require for building. The list is located under Godeps directory in Godeps.json file. It maps each imported path to its corresponding commit. The list can be used by scripts to automatically check if all imported paths are packaged and up-to-date in Fedora.

Other projects like docker use vendor directory to store a list of dependencies instead of Godeps.

If the list of dependencies is provided it is good to include it in %doc in %files section of the spec file.

Branching macros

For some packaged binaries it is impossible to provide debugging information, some binaries can not be built from de-bundled dependencies, provided tests need internet connection in order to work properly. For these use cases it is convenient to add with_debug, with_bundled and with_check macros, wrap parts of spec file and set the macros accordingly. Other macros as with_devel can be used to wrap devel subpackage parts and install commands. E.g.

%if 0%{?fedora}
%global with_devel 1
%global with_bundled 0
%global with_debug 1
%global with_check 1
%else
%global with_devel 0
%global with_bundled 1
%global with_debug 0
%global with_check 0
%endif

# [...]

%if 0%{?with_debug}
%global _dwz_low_mem_die_limit 0
%else
%global debug_package   %{nil}
%endif

# [...]

%if 0%{?with_devel}
%package devel
BuildRequires:  golang >= 1.2.1-3
# [...]

%description devel
# [...]
%endif

# [...]

%build
%if ! 0%{?with_bundled}
# Make link for etcd itself
mkdir -p src/github.com/coreos
ln -s ../../../ src/github.com/coreos/etcd
# [...]
%if 0%{?with_debug}
function gobuild { go build -a -ldflags "-B 0x$(head -c20 /dev/urandom|od -An -tx1|tr -d ' \n')" -v -x "$@"; }
%else
function gobuild { go build -a "$@" -ldflags "-X %{import_path}/version.GitSHA %{shortcommit}"; }
%endif
gobuild -o bin/etcd %{import_path}
gobuild -o bin/etcdctl %{import_path}/etcdctl
gobuild -o bin/etcd-migrate %{import_path}/tools/%{name}-migrate
%else
./build
%endif

# [...]

%install
# [...]
%if 0%{?with_devel}
# Install files for devel sub-package
install -d %{buildroot}/%{gopath}/src/%{import_path}
cp -pav main.go %{buildroot}/%{gopath}/src/%{import_path}/
for dir in client discovery error; do
    cp -rpav ${dir} %{buildroot}/%{gopath}/src/%{import_path}/
done
%endif

# [...]

%check
%if 0%{?with_check}
%if 0%{?with_bundled}
export GOPATH=$(pwd)/Godeps/_workspace:%{gopath}
%else
export GOPATH=%{buildroot}%{gopath}:%{gopath}
%endif
go test %{import_path}/client
go test %{import_path}/discovery
%endif

# [...]

Check of dependencies

After an update of a package a list of provided and imported packages can change. In order to get a list of missing or superfluous provided and imported packages, one can use gofed tool by runing 'gofed lint' in a repository directory:

$ basename $(pwd)
golang-googlecode-net
$ ls
golang-googlecode-net.spec  net-7dbad50.tar.gz  sources
$ gofed lint
1 golang specfile checked; 0 errors, 0 warnings.

If some 'Provides' or 'BuildRequires' are missing:

$ gofed lint
W: Missing BuildRequires: golang(golang.org/x/text/encoding/korean)
W: Missing BuildRequires: golang(golang.org/x/text/encoding/simplifiedchinese)
W: Missing BuildRequires: golang(golang.org/x/text/encoding/traditionalchinese)
W: Missing Provides: golang(golang.org/x/net/internal/iana)
W: Missing Provides: golang(golang.org/x/net/internal/nettest)
W: Missing Provides: golang(golang.org/x/net/ipv4)
W: Missing Provides: golang(golang.org/x/net/ipv6)
1 golang specfile checked; 0 errors, 7 warnings.

The command inspects project's tarball, sources file and compares a list of provided/imported packages in spec file with those in tarball. As some packages have different name for a devel subpackage (e.g. golang-googlecode-net package has golang-golangorg-net-devel devel subpackage), which subpackage is the devel subpackage has to be specified by setting devel_main macro. At the same time if a devel subpackage has different import path than the one specified in %{import_path} macro, devel_prefix macro has to be set in order for 'gofed lint' to check the correct subpackage.

%global provider_tld    com
%global provider        github
%global project         golang
%global repo            net
%global import_path     code.google.com/p/go.net
%global commit          7dbad50ab5b31073856416cdcfeb2796d682f844
%global shortcommit     %(c=%{commit}; echo ${c:0:7})

# primary devel subpackage
%global x_provider      golang
%global x_provider_tld  org
%global x_repo          net
%global x_import_path   %{x_provider}.%{x_provider_tld}/x/%{x_repo}
%global x_name          golang-%{x_provider}%{x_provider_tld}-%{repo}

# here the package name is golang-googlecode-net
# but the devel subpackage is golang-golangorg-net-devel
%global devel_main      golang-golangorg-net-devel
# all macros belonging to golang-golangorg-net-devel subpackage
# are defined by the same macros names as for main package
# but prefixed with x_, i.e. x_provider, x_import_path, ...
%global devel_prefix    x

# [...]

Name:       golang-googlecode-net
Version:    0
Release:    0.21.git%{shortcommit}%{?dist}
Summary:    Supplementary Go networking libraries

# [...]

If your package has different devel subpackage or use different %{import_path} macro, please specify devel_main and devel_prefix macros.

Spec file generators

Spec files for 'packaging a library' as described above can be generated via gofed tool. At the moment it supports generators for github.com, code.google.com and bitbucket.org. Generated spec files conform to the current golang packaging guidelines and are ready to use.

Summary and License has to be modified manually. Generated spec file can be further extended based on a specific projects (some directories has to be removed,

description or summary extended, %doc extended for other important documents, etc.). Some projects provide main packages which can be built. As a building process for each project is specific (via go build, make, hack/make.sh etc.) the generator keeps %build section empty. Neither debuginfo nor with_* macros are generated.

Sample RPM Spec

Following a couple of example RPM spec files to give a sample layout for future packagers of libraries or applications written in golang.

Packaging a library

%global go_import_path     code.google.com/p/go.net
%global rev             84a4013f96e01fdd14b65d260a78b543e3702ee1
%global shortrev        %(r=%{rev}; echo ${r:0:12})

Name:           golang-googlecode-net
Version:        0
Release:        0.15.hg%{shortrev}%{?dist}
Summary:        Supplementary Go networking libraries
License:        BSD
URL:            http://%{go_import_path}
Source0:        https://net.go.googlecode.com/archive/%{rev}.zip
%if 0%{?fedora} >= 19
BuildArch:      noarch
%else
ExclusiveArch:  %{go_arches}
%endif
BuildRequires:  golang

%description
%{summary}

%package devel
Requires:       golang
Summary:        Supplementary Go networking libraries
Provides:       golang(%{go_import_path}) = %{version}-%{release}
Provides:       golang(%{go_import_path}/dict) = %{version}-%{release}
# [...]

%description devel
%{summary}

This package contains library source intended for building other packages
which use the supplementary Go networking libraries.


%prep

%setup -n net.go-%{shortrev}
cp html/testdata/webkit/README README-webkit

%build

%install
install -d %{buildroot}/%{gopath}/src/%{go_import_path}
for d in dict html idna ipv4 ipv6 proxy publicsuffix spdy websocket; do
   cp -avp $d %{buildroot}/%{gopath}/src/%{go_import_path}/
done

%check
GOPATH=%{buildroot}/%{gopath} go test %{go_import_path}/html
# [...]

%files devel
%defattr(-,root,root,-)
%doc AUTHORS CONTRIBUTORS LICENSE PATENTS README
%doc README-webkit
%dir %attr(755,root,root) %{gopath}/src/%{go_import_path}
%dir %attr(755,root,root) %{gopath}/src/%{go_import_path}/dict
%dir %attr(755,root,root) %{gopath}/src/%{go_import_path}/html
# [...]
%{gopath}/src/%{go_import_path}/dict/*.go
%{gopath}/src/%{go_import_path}/html/*.go
# [...]

%changelog
* Fri Jul 11 2014 Vincent Batts <vbatts@fedoraproject.org> - 0-0.15.hg84a4013f96e0
- don't fail on ipv6 test bz1056185
# [...]

Packaging a binary

%global commit      63fe64c471e7d76be96a625350468dfc65c06c31
%global shortcommit %(c=%{commit}; echo ${c:0:7})

Name:           example-app
Version:        1.0.0
Release:        6%{?dist}
Summary:        This application is an example for the golang binary RPM spec
License:        ASL 2.0 
URL:            http://www.example-app.io
Source0:        https://github.com/example/app/archive/v%{version}.tar.gz
Source1:        example-app.service
Source2:        example-app.sysconfig

BuildRequires:  gcc

BuildRequires:  golang >= 1.2-7

# pull in golang libraries by explicit import path, inside the meta golang()
BuildRequires:  golang(github.com/gorilla/mux) >= 0-0.13
[...]

%description
# include your full description of the application here.

%prep
%setup -q -n example-app-%{version}

# many golang binaries are "vendoring" (bundling) sources, so remove them. Those dependencies need to be packaged independently.
rm -rf vendor

%build
# set up temporary build gopath, and put our directory there
mkdir -p ./_build/src/github.com/example
ln -s $(pwd) ./_build/src/github.com/example/app

export GOPATH=$(pwd)/_build:%{gopath}
go build -o example-app .

%install
install -d %{buildroot}%{_bindir}
install -p -m 0755 ./example-app %{buildroot}%{_bindir}/example-app

%files
%defattr(-,root,root,-)
%doc AUTHORS CHANGELOG.md CONTRIBUTING.md FIXME LICENSE MAINTAINERS NOTICE README.md
%{_bindir}/example-app

%changelog
* Tue Jul 01 2014 Jill User <jill.user@fedoraproject.org> - 1.0.0-6
- package the example-app

Thanks

These guidelines are Fedora-specific but are intended to match Debian practice where that is reasonable.

Discussion

See Talk:PackagingDrafts/Go for discussion.