maintner/maintnerd/maintapi: look for TRY= in inline comments

The Gerrit UI has changed its default behavior when leaving top-level
comments on a CL. Previously, that text was a part of the CL-scoped
messages, but now it is located in a patchset-level inline comment.

This change updates the logic in maintapi to look for TRY= comments
in the new place. This requires making an additional Gerrit API call
to the new ListChangeComments endpoint, because the inline comment
data is not tracked by the maintner corpus, and it can't be fetched
via the existing QueryChanges API call.

Start using the patch set number as returned by the Gerrit API,
instead of parsing it out of the message prefix with a regexp,
as this is simpler and should be more robust.

Document and simplify tryWorkItem slightly by removing support for
nil *gerrit.ChangeInfo. This was only needed for tests, but it's easy
to adjust tests to not depend on this. That makes the code in the
helper less indented and less complicated.

During these changes, the unintentional pitfall where the TRY= comment
had to be preceded by a blank link has also been removed. It only needs
to be on its own line now, as it was likely originally intended.

Fixes golang/go#40106.
Fixes golang/go#38747.

Change-Id: I64e85c18fefc23e1796de61dd8ba7025ea411706
Reviewed-by: Filippo Valsorda <>
5 files changed
tree: c9bed2f0d2c22f9d352c3f8fa01e559af631d439
  1. .dockerignore
  2. .gcloudignore
  9. app/
  10. autocertcache/
  11. build.go
  12. buildenv/
  13. buildlet/
  14. cloudfns/
  15. cmd/
  16. codereview.cfg
  17. crfs/
  18. dashboard/
  19. devapp/
  20. doc/
  21. env/
  22. envutil/
  23. gerrit/
  24. go.mod
  25. go.sum
  26. internal/
  27. kubernetes/
  28. livelog/
  29. maintner/
  30. pargzip/
  31. repos/
  32. revdial/
  33. tarutil/
  34. 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.