hyperhive/swarm-controller/README.md
atlas d3b40da1c8 deploy: give every option an enable, and name the controller one
Two corrections from review, applied forward on this branch rather than
by rewriting it.

`deploy.<service>` was a bare bool, which makes
`deploy.forgejo = { enable; ci; }` unrepresentable -- the nested
CI-runner sub-option this namespace was designed around. Every entry is
now an attrset with an `enable`, so a second per-host deployment
decision becomes an ordinary addition rather than a migration.

`deploy.controller` is now `deploy.swarm-controller`, consistent with
`deploy.swarm-ui`, which was introduced in the same commit.

89 references rewritten across 24 files -- nix, Rust, docs, and the
repo's own CLAUDE.md.

The prefix-anchored sweep missed exactly one, and it was live code:
hive-tls.nix spells it `hyperhiveCfg.deploy.controller` -- the only
`hyperhiveCfg` prefix among 45 references. A suffix grep
(`\.deploy\.<name>`) finds it; a path-anchored one cannot, because the
head of a reference is whatever alias the reading file happens to bind.
2026-08-30 04:23:22 +02:00

2.6 KiB

swarm-controller

The swarm-level daemon. Where hive-c0re owns the agents on one host, this owns what is true across hives — so a swarm runs one of them and most hives leave it off.

Opt-in per host via services.hyperhive.deploy.swarm-controller.enable, which is deliberately not derived from services.hyperhive.enable: turning it on is a statement about swarm topology, not about whether hyperhive is installed.

What it does today

Serves one /health endpoint and holds no state.

That is the whole intent of the first slice. The point is to make the unit real — service user, runtime and state directories, socket, nginx reachability — so the swarm-level surfaces that follow have somewhere to land. Inventing those surfaces before they are agreed would bake in a shape nobody chose. See #3066 and the hyperhive.swarm consolidation epic.

Why a unix socket, not a port

The hive-gateway's nginx is the only intended client and reaches the socket through a bind-mount. A listener that is never bound to an address cannot be reached from off-host by mistake.

The socket path is services.hyperhive.swarm.controller.socketPath, default /run/swarm-controller/controller.sock, exported to the process as SWARM_CONTROLLER_SOCKET.

⚠️ The socket's directory is its access control

The socket is 0666. It has to be: nginx runs as a different user and connect(2) needs write. This matches how hive-c0re publishes the per-agent sockets, and rests on the same argument — "the bind source dir is per-agent on host so blast radius is unchanged."

What keeps that safe is that the directory holds one socket. So:

Never point socketPath at a directory that carries anything else. /run/hyperhive above all — it holds host.sock, the host admin socket. Pointing nginx at that directory to reach this socket would put the admin socket within its reach too.

nginx is a host service, so nothing narrows what it can reach except the directory itself — that is the whole of the access control. A unit test pins the default path so a tidying edit fails instead of reviewing cleanly.

RuntimeDirectoryPreserve=yes and the daemon's stale-socket unlink on start are a pair: preserving the directory without the unlink means bind fails with EADDRINUSE after a restart.

Packaging

Built by the workspace derivation and extracted as its own package (nix build .#swarm-controller). Deliberately not in nix/packages' daemonBins — that list is the core stack and drives the bundle services.hyperhive.c0re.package points at, so folding this in would put a swarm-scoped service into every hive's closure.