hyperhive/nix/host-modules/local-defaults.nix

# The all-local deployment mode.
#
# `enableAllLocalDefaults` is a *mode*, not a default other options read:
# it says "this box is the whole deployment" and then asserts the values
# that follow from that. mara, on the issue: it is "more of a deployment
# mode via settings set, less a default setting".
#
# That distinction is why the derivations live here as `mkDefault` in a
# `config` block rather than as `default =` inside each option. An option
# declares what IT is and what it is when nobody asks; a mode declares
# what a deployment shape implies. Written the other way round, every
# service option had to name a flag it has no relationship to, and the
# answer to "what does all-local turn on?" was spread across five files.
#
# Adding an autoconfigurable thing later means one line here — not a
# `default =` in the new module pointing back at this flag.
{
  lib,
  config,
  ...
}:
let
  cfg = config.services.hyperhive;
in
{
  options.services.hyperhive.enableAllLocalDefaults = lib.mkOption {
    type = lib.types.bool;
    default = false;
    example = true;
    description = ''
      Run the whole swarm on this host. Turning this on asserts the
      toggles that an all-on-one-box deployment implies: the swarm's
      shared services
      (`services.hyperhive.swarm.enableRequiredServices`), the swarm
      CA (`services.hyperhive.swarm.ca.autoConfigure`), the swarm
      controller (`services.hyperhive.swarm.controller.enable`), and the
      host's `/etc/hosts` entries for the names this hive serves
      (`services.hyperhive.gateway.localHostsEntry`) — with no real DNS
      for those names, the operator is browsing them from the same box
      that answers for them.

      **Off by default, and that is the load-bearing part.** A swarm's
      services and its hives can live on different hosts, and a host has
      no way to tell which ones it is meant to be — so this is an
      operator saying "this is that box", never something inferred.
      Turn it on for a dev box or a single-hive swarm and get a working
      deployment with no further configuration; leave it off and every
      swarm-level artifact is operator-provided.

      Each toggle it asserts can still be set explicitly, which wins —
      so "all local except X" needs no new option.
    '';
  };

  # What the mode asserts. `mkDefault` (priority 1000) beats an option's
  # own `default` (1500) and loses to any explicit definition, which is
  # exactly the precedence a deployment mode wants: it fills in for an
  # operator who hasn't spoken, and never argues with one who has.
  # The gateway's own all-local bit. `localHostsEntry` maps every name
  # this hive answers for to 127.0.0.1 in the HOST's /etc/hosts, which is
  # exactly what "this box is the whole deployment" implies: there is no
  # real DNS for these names, and the operator is browsing them from the
  # same machine that serves them.
  #
  # ⚠️ It does NOT affect what containers resolve. dnsmasq sets
  # `no-hosts = true` unconditionally (see hive-gateway/dnsmasq.nix), so
  # agents keep getting the bridge IP from the authoritative `address=`
  # rules rather than the host's 127.0.0.1 — an entry that would point
  # every agent at its own netns. That guard already existing is what
  # makes turning this on by default safe; without it this line would
  # break every agent's access to the forge.
  config.services.hyperhive.gateway.localHostsEntry = lib.mkDefault cfg.enableAllLocalDefaults;

  config.services.hyperhive.swarm = {
    enableRequiredServices = lib.mkDefault cfg.enableAllLocalDefaults;
    ca.autoConfigure = lib.mkDefault cfg.enableAllLocalDefaults;
    # The queue's auth-callout nkeys. Generating them is safe exactly
    # when one operator owns both the queue and its responder, which is
    # what this mode asserts. On any other topology the seeds have to
    # reach whoever runs the responder, and minting them here would move
    # that hand-off somewhere less visible rather than removing it.
    nats.autoGenerateCallout = lib.mkDefault cfg.enableAllLocalDefaults;
    # The controller is asserted by the MODE and by nothing else. Its own
    # option stays `default = false` precisely because running it is a
    # statement about swarm topology — but "this box is the whole
    # deployment" IS that statement, and it is the one shape where the
    # answer isn't ambiguous. Deriving it from `enableRequiredServices`
    # instead would be wrong: a hive in a larger swarm can legitimately
    # want the shared services without being the host that controls them.
    controller.enable = lib.mkDefault cfg.enableAllLocalDefaults;

    # The controller's queue coordinates. Co-location is what makes these
    # derivable at all — loopback only reaches the queue when the queue is
    # here, and the minted client secret only exists on the host authelia
    # ran its first boot on — so they belong to the mode that asserts this
    # box is the whole deployment, not to the options' own `default`.
    #
    # Deriving them from `swarm.nats.enable` / `swarm.authelia.enable`
    # inside those defaults is the mixing this file exists to prevent: the
    # option would be describing a deployment shape instead of describing
    # itself, and "what does all-local turn on?" would stop having one
    # answer.
    #
    # ⚠️ Must live INSIDE this attrset, not as a second
    # `config.services.hyperhive.swarm.…` path beside it — written that
    # way the two definitions of `swarm` collide and the nested one is
    # silently lost. The gate caught exactly that: mode on, `natsUrl`
    # still "".
    #
    # The *requirement* stays in `swarm-controller.nix` as an assertion:
    # needing a queue is the controller's own property in every topology,
    # and only the convenience is local.
    controller.queue.natsUrl = lib.mkIf cfg.enableAllLocalDefaults (
      lib.mkDefault "nats://127.0.0.1:${toString config.services.hyperhive.swarm.nats.port}"
    );
    controller.queue.clientSecretFile = lib.mkIf cfg.enableAllLocalDefaults (
      lib.mkDefault "${config.services.hyperhive.swarm.authelia.hostClientSecretDir}/swarm-controller.secret"
    );
  };
}