buildbot-nix/README.md

# Buildbot-nix

Buildbot-nix is a NixOS module designed to integrate
[Buildbot](https://www.buildbot.net/), a continuous integration (CI) framework,
into the Nix ecosystem. This module is under active development, and while it's
generally stable and widely used, please be aware that some APIs may change over
time.

## Getting Started with Buildbot Setup

To set up Buildbot using Buildbot-nix, you can start by exploring the provided
examples:

- Check out the basic setup in [example](./examples/default.nix).
- Learn about configuring the Buildbot master in
  [master module](./nix/master.nix).
- Understand how to set up a Buildbot worker in
  [worker module](./nix/worker.nix).

Additionally, you can find real-world examples at the end of this document.

Buildbot masters and workers can be deployed either on the same machine or on
separate machines. To support multiple architectures, configure them as
[nix remote builders](https://nixos.org/manual/nix/stable/advanced-topics/distributed-builds).
For a practical NixOS example, see
[this remote builder configuration](https://github.com/Mic92/dotfiles/blob/main/nixos/eve/modules/remote-builder.nix).

## Using Buildbot in Your Project

Buildbot-nix automatically triggers builds for your project under these
conditions:

- When a pull request is opened.
- When a commit is pushed to the default git branch.

It does this by evaluating the `.#checks` attribute of your project's flake in
parallel. Each attribute found results in a separate build step. You can test
these builds locally using `nix flake check -L` or
[nix-fast-build](https://github.com/Mic92/nix-fast-build).

If you need to build other parts of your flake, such as packages or NixOS
machines, you should re-export these into the `.#checks` output. Here are two
examples to guide you:

- Using
  [flake-parts](https://github.com/Mic92/dotfiles/blob/10890601a02f843b49fe686d7bc19cb66a04e3d7/flake.nix#L139).
- A
  [plain flake example](https://github.com/nix-community/nixos-images/blob/56b52791312edeade1e6bd853ce56c778f363d50/flake.nix#L53).

### Integration with GitHub

Buildbot-nix primarily supports GitHub, with plans to extend support to other
platforms like Gitea.

To integrate with GitHub:

1. **GitHub App**: Set up a GitHub app for Buildbot to enable GitHub user
   authentication on the Buildbot dashboard.
2. **OAuth Credentials**: After installing the app, generate OAuth credentials
   and configure them in the buildbot-nix NixOS module. Set the callback url to
   `https://<your-domain>/auth/login`.
3. **GitHub Token**: Obtain a GitHub token with `admin:repo_hook` and `repo`
   permissions. For GitHub organizations, it's advisable to create a separate
   GitHub user for managing repository webhooks.

### Binary caches

To access the build results on other machines there are two options at the
moment

#### Local binary cache (harmonia)

You can set up a binary cache on your buildbot-worker machine to make its nix
store accessible from other machines. Check out the README of the
[project](https://github.com/nix-community/harmonia/?tab=readme-ov-file#configuration-for-public-binary-cache-on-nixos),
for an example configuration

#### Cachix

Buildbot-nix also supports pushing packages to cachix. Check out the comment out
[example configuration](https://github.com/Mic92/buildbot-nix/blob/main/examples/master.nix)
in our repository.

### Real-World Deployments

See Buildbot-nix in action in these deployments:

- **Nix-community infra**:
  [Configuration](https://github.com/nix-community/infra/tree/master/modules/nixos)
  | [Instance](https://buildbot.nix-community.org/)
- **Mic92's dotfiles**:
  [Configuration](https://github.com/Mic92/dotfiles/blob/main/nixos/eve/modules/buildbot.nix)
  | [Instance](https://buildbot.thalheim.io/)
- **Technical University Munich**:
  [Configuration](https://github.com/TUM-DSE/doctor-cluster-config/tree/master/modules/buildbot)
  | [Instance](https://buildbot.dse.in.tum.de/)
- **Numtide**: [Instance](https://buildbot.numtide.com)