Chromium Infra Go Area

Get the code

The steps for getting the code are:

  1. Install depot_tools

  2. Run fetch infra

  3. Run

    eval `infra/go/`

    On Windows

    call infra\go\env.cmd

Quick Setup

If you are on Linux you can run the quicksetup script (instead of the above) like so:

cd /where/you/want/source/code
wget -O- "" | base64 -d | bash

This will create a self-contained cr-infra-go-area directory and populate it will all necessary tools and source for using or contributing to Chromium's Go Infrastructure. Once run, look in cr-infra-go-area/infra/go/src for the editable source code.


infra/go knows how to bootstrap itself from scratch (i.e. from a fresh checkout) by downloading pinned version of Go toolset, and installing pinned versions of third party packages and adding a bunch of third party tools (like goconvey and protoc-gen-go) to $PATH.

The bootstrap (and self-update) procedure is invoked whenever go/ or go/ run. There‘s no DEPS hook for this. We only want the Go toolset to be present on systems that need it, since it’s somewhat big and platform-specific.

go/ can be used in two ways. If invoked without arguments, it verifies that everything is up-to-date and then just emits a small shell script that tweaks the environment. This script can be executed in the current shell process to modify its environment. Once it's done, Go tools can be invoked directly. This is the recommended way of “entering” infra/go build environment.

For example:

cd infra/go
eval `./`
cd src/infra
go install ./cmd/bqupload
../../bin/bqupload --help  # infra/go/bin is where executables are installed
bqupload --help            # infra/go/bin is also in $PATH

To see what environment is being changed, run ./ with a positional argument that is path to a file. Passing - instead of file path would print to standard output.

./ -

Alternatively go/ can be used as a wrapping command that sets up an environment and invokes some other process. It is particularly useful on Windows.

If the INFRA_PROMPT_TAG environment variable is exported while running go/, the new environment will include a modified PS1 prompt containing the INFRA_PROMPT_TAG value to indicate that the modified environment is being used. By default, this value is "[cr go] ", but it can be changed by exporting a different value or disabled by exporting an empty value.

Dependency management

Infra Go code uses a mix of gclient DEPS and Go Modules to manage dependencies.

There are two kinds of dependencies: dependencies between first-party code (like infra.git code depending on luci-go.git code) and dependencies between first-party and third-party code (like infra.git code depending on Google Cloud libraries).

Dependencies between first-party code are managed in the DEPS file, which is usually updated automatically by autoroller bots (e.g. luci-go => infra autoroller). This ensures changes to first-party code propagate quickly through the dependency tree.

Dependencies on third-party code are managed in go.mod and go.sum files. Each Chrome infra repository has them (for infra.git they are go/src/infra/go.mod and go/src/infra/go.sum), which turns these repositories into Go modules. Thus an infra gclient checkout is a checkout of a bunch of Go modules on disk side-by-side (according to the DEPS file). go build is made aware of this structure via replace directives in the go.mod file, which tells it to use locally checked out modules (at revisions precisely controlled by the DEPS), instead of trying to figure out their intended versions using some version selection algorithm. This structure also allows to make changes to one locally checked out module (like from luci-go.git), and verifying they don't break another module (like infra from infra.git, which depends on

Note that when building a specific Go target using Infra builders, only go.mod of its enclosing module is considered when fetching dependencies. For example, if you setup a CIPD package builder (or a Docker image builder, or GAE tarball builder) that builds, the builder will use dependencies specified in the go.mod in luci-go.git repository (using the luci-go's revision currently checked out on disk according to the DEPS in infra.git). If the same builder then tries to build e.g. infra/something, it will use the go.mod from the infra.git repository. And it even may end up using a different version of some third party dependency.

Adding or updating a dependency

Navigate to the directory with go.mod file (go/src/infra) and use regular Go modules commands to update go.mod and go.sum files. See Managing dependencies.

Making a DEPS roll that picks up go.mod changes

If a DEPS roll picks up a change to a go.mod file in a first party dependency, infra's go.sum (and sometimes go.mod) need to be modified too to pick up updated version pins and module checksums.

Ensure your local checkout matches DEPS and run go mod tidy in the infra module directory:

cd go/src/infra
go mod tidy

Add the resulting go.mod and go.sum changes to the CL.