Go Build Tools

Go Reference

This subrepository holds the source for various packages and tools that support Go's build system and the development of the Go programming language.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To contribute, see

The main issue tracker for the blog is located at Prefix your issue with "x/build/DIR: " in the subject line.


The main components of the Go build system are:

  • The dashboard, in app/, serves It runs on App Engine and holds the state for which builds passed or failed, and stores the build failure logs for post-submit failures. (Trybot build failure logs are stored elsewhere). The dashboard does not execute any builds on its own.

  • The coordinator, in cmd/coordinator/, serves It runs on GKE and coordinates the whole build system. It finds work to do (both pre-submit "TryBot" work, and post-submit work) and executes builds, allocating machines to run the builds. It is the owner of all machines.

  • The Go package in buildenv/ contains constants for where the dashboard and coordinator run, for prod, staging, and local development.

  • The buildlet, in cmd/buildlet/, is the HTTP server that runs on each worker machine to execute builds on the coordinator's behalf. This runs on every possible GOOS/GOARCH value. The buildlet binaries are stored on Google Cloud Storage and fetched per-build, so we can update the buildlet binary independently of the underlying machine images. The buildlet is the most insecure server possible: it has HTTP handlers to read & write arbitrary content to disk, and to execute any file on disk. It also has an SSH tunnel handler. The buildlet must never be exposed to the Internet. The coordinator provisions buildlets in one of three ways:

    1. by creating VMs on Google Compute Engine (GCE) with custom images configured to fetch & run the buildlet on boot, listening on port 80 in a private network.

    2. by running Linux containers (on either Google Kubernetes Engine or GCE with the Container-Optimized OS image), with the container images configured to fetch & run the buildlet on start, also listening on port 80 in a private network.

    3. by taking buildlets out of a pool of connected, dedicated machines. The buildlet can run in either listen mode (as on GCE and GKE) or in reverse mode. In reverse mode, the buildlet connects out to and registers itself with the coordinator. The TCP connection is then logically reversed (using revdial and when the coordinator needs to do a build, it makes HTTP requests to the coordinator over the already-open TCP connection.

    These three pools can be viewed at the coordinator's

  • The env/ directory describes build environments. It contains scripts to create VM images, Dockerfiles to create Kubernetes containers, and instructions and tools for dedicated machines.

  • maintner in maintner/ is a library for slurping all of Go's GitHub and Gerrit state into memory. The daemon maintnerd in maintner/maintnerd/ runs on GKE and serves The daemon watches GitHub and Gerrit and appends to a mutation log whenever it sees new activity. The logs are stored on GCS and served to clients.

  • The godata package in maintner/godata/ provides a trivial API to let anybody write programs against Go's maintner corpus (all of our GitHub and Gerrit history), live up to the second. It takes a few seconds to load into memory and a few hundred MB of RAM after it downloads the mutation log from the network.

  • pubsubhelper in cmd/pubsubhelper/ is a dependency of maintnerd. It runs on GKE, is available at, and runs an HTTP server to receive Webhook updates from GitHub on new activity and an SMTP server to receive new activity emails from Gerrit. It then is a pubsub system for maintnerd to subscribe to.

  • The gitmirror server in cmd/gitmirror/ mirrors Gerrit to GitHub, and also serves a mirror of the Gerrit code to the coordinator for builds, so we don't overwhelm Gerrit and blow our quota.

  • The Go gopherbot bot logic runs on GKE. The code is in cmd/gopherbot. It depends on maintner via the godata package.

  • The developer dashboard at runs on GKE. Its code is in devapp/. It also depends on maintner via the godata package.

  • cmd/retrybuilds: a Go client program to delete build results from the dashboard

Adding a Go Builder

If you wish to run a Go builder, please email first. There is documentation at, but depending on the type of builder, we may want to run it ourselves, after you prepare an environment description (resulting in a VM image) of it. See the env directory.

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Package build contains constants for the Go continuous build system.



View Source
const DevCoordinatorCA = `` /* 955-byte string literal not displayed */

DevCoordinatorCA is the cert used by the coordinator and buildlet in development mode. (Not to be confused with the staging "dev" instance under GCE project "go-dashboard-dev")

View Source
const DevCoordinatorKey = `` /* 1674-byte string literal not displayed */

DevCoordinatorKey is the key used by the coordinator and buildlet in development mode. (Not to be confused with the staging "dev" instance under GCE project "go-dashboard-dev")

View Source
const ProdCoordinatorCA = `` /* 1114-byte string literal not displayed */

ProdCoordinatorCA is the production CA cert for

View Source
const StagingCoordinatorCA = `` /* 1073-byte string literal not displayed */

StagingCoordinatorCA is the cert used on GCE for the go-dashboard-dev project.


This section is empty.


This section is empty.


type CoordinatorInstance

type CoordinatorInstance string

CoordinatorInstance is either "prod", "staging", or "localhost:<port>".

const (
	ProdCoordinator    CoordinatorInstance = "prod"
	StagingCoordinator CoordinatorInstance = "staging"

func (CoordinatorInstance) CACert

func (ci CoordinatorInstance) CACert() string

CACert returns the public certificate of the CA used to sign this coordinator instance's certificate.

func (CoordinatorInstance) TLSDialer

func (ci CoordinatorInstance) TLSDialer() func(network, addr string) (net.Conn, error)

func (CoordinatorInstance) TLSHostPort

func (ci CoordinatorInstance) TLSHostPort() (string, error)

Source Files


Path Synopsis
autocertcache Package autocertcache contains autocert.Cache implementations for
buildenv Package buildenv contains definitions for the environments the Go build system can run in.
buildlet Package buildlet contains client tools for working with a buildlet server.
cmd/buildlet The buildlet is an HTTP server that untars content to disk and runs commands it has untarred, streaming their output back over HTTP.
cmd/buildlet/stage0 The stage0 command looks up the buildlet's URL from its environment (GCE metadata service, scaleway, etc), downloads it, and runs it.
cmd/buildlet/testssh The testssh binary exists to verify that a buildlet container's ssh works, without running the whole coordinator binary in the staging environment.
cmd/buildstats The buildstats command syncs build logs from Datastore to Bigquery.
cmd/cl CL prints a list of open Go code reviews (also known as change lists, or CLs).
cmd/coordinator The coordinator runs the majority of the Go build system.
cmd/coordinator/internal/dashboard Package dashboard contains the implementation of the build dashboard for the Coordinator.
cmd/coordinator/metrics Package metrics enumerates the set of Stackdriver metrics used by the Go build system.
cmd/debugnewvm The debugnewvm command creates and destroys a VM-based buildlet with lots of logging for debugging.
cmd/docker2boot The docker2boot command converts a Docker image into a bootable GCE VM image.
cmd/fetchlogs Fetchlogs downloads build failure logs from the Go dashboard so they can be accessed and searched from the local file system.
cmd/genbootstrap The genbootstrap command prepares GOROOT_BOOTSTRAP tarballs suitable for use on builders.
cmd/genbuilderkey The genbuilderkey binary generates a builder key or gomote user key from the build system's master key.
cmd/gerritbot The gerritbot binary converts GitHub Pull Requests to Gerrit Changes, updating the PR and Gerrit Change as appropriate.
cmd/gitmirror The gitmirror binary watches the specified Gerrit repositories for new commits and syncs them to GitHub.
cmd/gomote The gomote command is a client for the Go builder infrastructure.
cmd/gopherbot The gopherbot command runs Go's gopherbot role account on GitHub and Gerrit.
cmd/makemac The makemac command starts OS X VMs for the builders.
cmd/perfrun perfrun interacts with the buildlet coordinator to run the go1 benchmarks on a buildlet slave for the most recent successful commits according to the build dashboard.
cmd/pubsubhelper The pubsubhelper is an SMTP server for Gerrit updates and an HTTP server for Github webhook updates.
cmd/pubsubhelper/pubsubtypes Package pubsubtypes contains types published by pubsubhelper.
cmd/racebuild racebuild builds the race runtime (syso files) on all supported OSes using gomote.
cmd/release Command release builds a Go release.
cmd/releasebot Releasebot manages the process of defining, packaging, and publishing Go releases.
cmd/relnote The relnote command summarizes the Go changes in Gerrit marked with RELNOTE annotations for the release notes.
cmd/relui relui is a web interface for managing the release process of Go.
cmd/retrybuilds The retrybuilds command clears build failures from the dashboard to force them to be rebuilt.
cmd/rmplaysnippet The rmplaysnippet binary removes a code snippet from given its URL or ID.
cmd/rundockerbuildlet The rundockerbuildlet command loops forever and creates and cleans up Docker containers running reverse buildlets.
cmd/scaleway The scaleway command creates ARM servers on
cmd/tip Command tip is the server, serving the latest HEAD straight from the Git oven.
cmd/updatecontrib The updateac command updates the CONTRIBUTORS file in the Go repository.
cmd/updatedisks The updatedisks command creates & deletes VM disks as needed across the various GCP zones.
cmd/updatestd updatestd is an experimental program that has been used to update the standard library modules as part of in CL 255860 and CL 266898.
cmd/upload The upload command writes a file to Google Cloud Storage.
cmd/xb The xb command wraps GCP deployment commands such as gcloud, kubectl, and docker push and verifies they're interacting with the intended prod-vs-staging environment.
dashboard Package dashboard contains shared configuration and logic used by various pieces of the Go continuous build system.
devapp Devapp is the server running
envutil Package envutil provides utilities for working with environment variables.
gerrit Package gerrit contains code to interact with Gerrit servers.
internal/buildgo Package buildgo provides tools for pushing and building the Go distribution on buildlets.
internal/buildstats Package buildstats contains code to sync the coordinator's build logs from Datastore to BigQuery.
internal/foreach Package foreach provides allocation-conscious helpers for iterating over lines of text.
internal/gitauth Package gitauth writes gitcookies files so git will authenticate to Gerrit as gopherbot for quota purposes.
internal/gophers Package gophers is a list of names, emails, and GitHub usernames of people from the Go git repos and issue trackers.
internal/httpdl Package httpdl downloads things from HTTP to local disk.
internal/https Package https contains helpers for starting an HTTPS server.
internal/loghash Package loghash provides the shared information for computing a log hash (as in
internal/lru Package lru implements an LRU cache.
internal/secret Package secret provides a client interface for interacting with the GCP Secret Management service.
internal/singleflight Package singleflight provides a duplicate function call suppression mechanism.
internal/sourcecache Package sourcecache provides a cache of code found in Git repositories.
internal/spanlog Package spanlog provides span and event logger interfaces.
internal/untar Package untar untars a tarball to disk.
kubernetes Package kubernetes contains a minimal client for the Kubernetes API.
kubernetes/api Package api contains the Kubernetes v1 API types.
kubernetes/gke Package gke contains code for interacting with Google Container Engine (GKE), the hosted version of Kubernetes on Google Cloud Platform.
livelog Package livelog provides a buffer that can be simultaneously written to by one writer and read from by many readers.
maintner Package maintner mirrors, searches, syncs, and serves Git, Github, and Gerrit metadata.
maintner/godata Package godata loads the Go project's corpus of Git, Github, and Gerrit activity into memory to allow easy analysis without worrying about APIs and their pagination, quotas, and other nuisances and limitations.
maintner/gostats The gostats command computes stats about the Go project.
maintner/maintnerd The maintnerd command serves project maintainer data from Git, Github, and/or Gerrit.
maintner/maintnerd/apipb Package apipb is a generated protocol buffer package.
maintner/maintnerd/gcslog Package gcslog is an implementation of maintner.MutationSource and Logger for Google Cloud Storage.
maintner/maintnerd/maintapi Package maintapi exposes a gRPC maintner service for a given corpus.
maintner/maintnerd/maintapi/version Package version implements logic to parse version of Go tags and release branches.
maintner/maintpb Package maintpb is a generated protocol buffer package.
maintner/maintq The maintq command queries a maintnerd gRPC server.
maintner/maintwatch The maintwatch commands tails the maintner mutation log.
maintner/reclog Package reclog contains readers and writers for a record wrapper format used by maintner.
pargzip Package pargzip contains a parallel gzip writer implementation.
repos Package repos contains information about Go source repositories.
revdial/v2 Package revdial implements a Dialer and Listener which work together to turn an accepted connection (for instance, a Hijacked HTTP request) into a Dialer which can then create net.Conns connecting back to the original dialer, which then gets a net.Listener accepting those conns.
tarutil Package tarutil contains utilities for working with tar archives.
types Package types contains common types used by the Go continuous build system.
version The version package permits running a specific version of Go.
version/go1.10 The go1.10 command runs the go command from go1.10.
version/go1.10.1 The go1.10.1 command runs the go command from Go 1.10.1.
version/go1.10.2 The go1.10.2 command runs the go command from go1.10.2.
version/go1.10.3 The go1.10.3 command runs the go command from go1.10.3.
version/go1.10beta1 The go1.10beta1 command runs the go command from go1.10beta1.
version/go1.10beta2 The go1.10beta2 command runs the go command from go1.10beta2.
version/go1.10rc1 The go1.10rc1 command runs the go command from go1.10rc1.
version/go1.10rc2 The go1.10rc2 command runs the go command from go1.10rc2.
version/go1.11beta1 The go1.11beta1 command runs the go command from go1.11beta1.
version/go1.8 The go1.8 command runs the go command from go1.8.
version/go1.8.1 The go1.8.1 command runs the go command from go1.8.1.
version/go1.8.2 The go1.8.2 command runs the go command from go1.8.2.
version/go1.8.3 The go1.8.3 command runs the go command from go1.8.3.
version/go1.8.4 The go1.8.4 command runs the go command from go1.8.4.
version/go1.8.5 The go1.8.5 command runs the go command from go1.8.5.
version/go1.8.6 The go1.8.6 command runs the go command from go1.8.6.
version/go1.8.7 The go1.8.7 command runs the go command from go1.8.7.
version/go1.8beta1 The go1.8beta1 command runs the go command from go1.8beta1.
version/go1.8beta2 The go1.8beta2 command runs the go command from go1.8beta2.
version/go1.8rc1 The go1.8rc1 command runs the go command from go1.8rc1.
version/go1.8rc2 The go1.8rc2 command runs the go command from go1.8rc2.
version/go1.8rc3 The go1.8rc3 command runs the go command from go1.8rc3.
version/go1.9 The go1.9 command runs the go command from go1.9.
version/go1.9.1 The go1.9.1 command runs the go command from go1.9.1.
version/go1.9.2 The go1.9.2 command runs the go command from go1.9.2.
version/go1.9.3 The go1.9.3 command runs the go command from go1.9.3.
version/go1.9.4 The go1.9.4 command runs the go command from go1.9.4.
version/go1.9.5 The go1.9.5 command runs the go command from Go 1.9.5.
version/go1.9.6 The go1.9.6 command runs the go command from go1.9.6.
version/go1.9.7 The go1.9.7 command runs the go command from go1.9.7.
version/go1.9beta1 The go1.9beta1 command runs the go command from go1.9beta1.
version/go1.9beta2 The go1.9beta2 command runs the go command from go1.9beta2.
version/go1.9rc1 The go1.9rc1 command runs the go command from go1.9rc1.
version/go1.9rc2 The go1.9rc2 command runs the go command from go1.9rc2.
MODULE cloudfns/issueswebhook
MODULE cloudfns/sendwikidiff
MODULE cloudfns/wikiwebhook
MODULE maintner/cmd/maintserve