cmd/release: embed releaselet.go source code statically

Previously, the release binary dynamically looked for the releaselet.go
source code. It first checked in the current working directory, and
then used the go/build package to find the location of source code of package on disk.

The release binary is not generally executed by hand, rather it is used
internally by releasebot command. That makes it hard to know in advance
where the current working directory for release will be (that directory
is $HOME/go-releasebot-work/<release> that releasebot creates itself).

Further, with the proliferation of module mode, it's no longer viable
to be able to find the location of a package by its import path via
go/build.Import. As a result, there's now a higher risk of cmd/release
not finding, or finding a wrong version of releaselet.go.

Change the release binary to instead statically embed the releaselet.go
source code as a constant string, in a static.go file that is generated
via a go:generate directive.

Add a test to ensure the embedded copy of releaselet.go doesn't get out
of sync.

The embedding approach was loosely based on approach taken in package, but it was simplified for the smaller
needs of cmd/release (i.e., embedding a single text file). We rely on
fmt's %q verb to do the escaping, which has the risk of changing between
Go versions, but it's unlikely to happen often to warrant worrying yet.

Fixes golang/go#33443

Change-Id: Ie7a9481c33a7d9668d696d3827e5681b07b37094
Reviewed-by: Filippo Valsorda <>
4 files changed
tree: ea15f8830d2b862e9d56acd850d34eff714842dd
  1. .dockerignore
  8. app/
  9. autocertcache/
  10. build.go
  11. buildenv/
  12. buildlet/
  13. cloudfns/
  14. cmd/
  15. codereview.cfg
  16. crfs/
  17. dashboard/
  18. devapp/
  19. doc/
  20. env/
  21. envutil/
  22. gerrit/
  23. go.mod
  24. go.sum
  25. internal/
  26. kubernetes/
  27. livelog/
  28. maintner/
  29. pargzip/
  30. revdial/
  31. status/
  32. tarutil/
  33. types/
  35. update-readmes.go
  36. vcs-test/
  37. version/

Go Build Tools

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.