cmd/gitmirror: refactor

In preparation for adding a new mirror destination, refactor. A lot of
this is subjective, and arguably just my personal taste. Still, I think
it's an improvement.

Generally, I don't intend to change behavior here. Two small things:
first, the list of repositories to watch is read from the repos package
rather than Gerrit; I don't think that matters, but please correct me if
I'm wrong. Second, we start a repo Loop for every repository, not just
those being mirrored. I think this was an oversight, and it resulted in
the repository not being eagerly fetched.

Notable refactorings:
- Remove the package vars: "tickler" channels move into Repo, others
  into the new top-level mirror type.
- Remove some overly fancy logging; I personally don't mind reading
  "attempt 0" in a message, etc.
- Restructure initialization logic to hopefully be a little bit better
  grouped and more readable.
- Introduce the concept of multiple destinations, but don't use it yet.
- Rather than checking for the correct remotes during initialization,
  just blow them away and recreate them.

Change-Id: I906f45fb93e2e4a2552aea5560eeb244174bfe69
Reviewed-on: https://go-review.googlesource.com/c/build/+/323970
Trust: Heschi Kreinick <heschi@google.com>
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
2 files changed
tree: db98e9688d62d0bf4597f3cbf29dcace413ee690
  1. app/
  2. autocertcache/
  3. buildenv/
  4. buildlet/
  5. cloudfns/
  6. cmd/
  7. crfs/
  8. dashboard/
  9. devapp/
  10. doc/
  11. env/
  12. envutil/
  13. gerrit/
  14. internal/
  15. kubernetes/
  16. livelog/
  17. maintner/
  18. pargzip/
  19. repos/
  20. revdial/
  21. tarutil/
  22. types/
  23. vcs-test/
  24. version/
  25. .dockerignore
  26. .gcloudignore
  27. AUTHORS
  28. build.go
  29. codereview.cfg
  30. CONTRIBUTING.md
  31. CONTRIBUTORS
  32. go.mod
  33. go.sum
  34. LICENSE
  35. PATENTS
  36. README.md
  37. update-readmes.go
README.md

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 https://golang.org/doc/contribute.html.

The main issue tracker for the blog is located at https://github.com/golang/go/issues. Prefix your issue with “x/build/DIR: ” in the subject line.

Overview

The main components of the Go build system are:

  • The dashboard, in app/, serves https://build.golang.org/. 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 https://farmer.golang.org/. 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 https://farmer.golang.org/ 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 http://farmer.golang.org/#pools

  • 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 https://maintner.golang.org/. 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 https://pubsubhelper.golang.org/, 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 https://dev.golang.org/ 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 golang-dev@googlegroups.com first. There is documentation at https://golang.org/wiki/DashboardBuilders, 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.