58 lines
2.7 KiB
Markdown
58 lines
2.7 KiB
Markdown
# swarm-builder
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The swarm builder's build service, in the `swarm-builder` container on the
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host that sets `deploy.builder.enable`. The design is
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[`docs/swarm/builder.md`](../docs/swarm/builder.md).
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swarm-controller sends one request per config PR head: an agent, a commit and
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the PR. This service builds that agent config on the agent base this host was
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deployed with, through the host's nix daemon, and answers with the system
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closure's store path or the tail of what `nix` printed. The controller turns
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the answer into a `swarm-builder` commit status on the PR's head.
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## What a build is
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- `nix build` of `nix/builder/check-flake`'s `check` output, with its three
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inputs overridden: `hyperhive` and `nixpkgs` to this host's own sources,
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and `agent` to `git+https://<forge>/agent-configs/<agent>?ref=refs/pull/<pr>/head&rev=<rev>`.
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- The evaluation runs here, pure; the builds run in the host daemon's sandbox
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as an untrusted client, so a config can neither set daemon options nor read
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this service's environment.
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- Nothing is pushed and nothing is recorded: the closure stays in the host's
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store until it is collected.
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## Meta builds
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The service also builds one agent from `internal/meta` on request: an agent and
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a commit of the repo. It runs `nix build` of
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`nixosConfigurations.<agent>.config.system.build.toplevel` from that commit,
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with every input at the flake's own lock, and answers with the store path and
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the platform it builds for. The controller records the answer; the service
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writes nothing. It takes the same one-build slot as the PR checks. See
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[`docs/swarm/builder.md`](../docs/swarm/builder.md#deploy-gate).
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## Credentials
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The container holds one credential: its own store certificate, which nspawn
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hands in at start without a copy on disk. With it the service reads its
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queue client secret at start and again when authelia refuses it, and its
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read-only forge token at every build.
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`git` gets the token through a credential helper reading the child's
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environment, never in a URL or an argument, and the helper answers only an
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`https` request for the forge's host. Its store role reads exactly
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those two paths.
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## Archetypes
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The service also answers archetype evaluations: `nix eval` of the `meta` of
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every `hyperhiveArchetypes` entry in this host's hyperhive source, with
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nixpkgs pointed at this host's. It fetches nothing and uses no token, and it
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doesn't wait for a running build. See
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[`docs/swarm/archetypes.md`](../docs/swarm/archetypes.md).
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## Meta-flake lock
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The service also locks the swarm meta flake on request: `nix flake lock` of
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the `flake.nix` it was sent, in a scratch directory, with the build's forge
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credential. It answers with the lock and commits nothing. See
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[`docs/swarm/builder.md`](../docs/swarm/builder.md#meta-flake-lock).
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