hyperhive/nix/module-eval/forge-placement.nix

# `checks.module-eval-forge-placement` — see ./lib.nix for the shared
# rationale (why this suite exists, naming convention, "evaluates
# not executes").
#
# Where the forge runs. A swarm has one, on the host with
# `deploy.forgejo.enable`; every other hive is a client of it, and the parts
# of a split deployment that used to lean on every host running a forge
# (the OIDC client, the controller's token, the CI runner) still have to
# hold.
{
  pkgs,
  lib,
  self,
  nixosSystem,
}:
let
  inherit
    (import ./lib.nix {
      inherit
        pkgs
        lib
        self
        nixosSystem
        ;
    })
    hive
    runGroup
    ;

  bare = hive { };
  allLocal = hive { deploy.singleHostSwarm = true; };
  servicesHere = hive { deploy.allSwarmServices = true; };
  forgeHere = hive { deploy.forgejo.enable = true; };

  # The shared services here, the forge somewhere else. Every derivation in
  # ../host-modules/swarm-required-services.nix is `mkDefault`, so this stays
  # expressible — and it is also the authelia-without-forge host the OIDC
  # client case needs.
  servicesForgeElsewhere = hive {
    deploy.allSwarmServices = true;
    deploy.forgejo.enable = false;
  };

  # The forge without authelia: the other half of the split.
  forgeNoAuthelia = hive {
    deploy.forgejo.enable = true;
    deploy.forgejo.sso.clientSecretFile = "/var/lib/forgejo-oidc/by-hand.secret";
  };

  ciNoForge = hive { deploy.forgejo.ci.enable = true; };
  ciWithForge = hive {
    deploy.forgejo.enable = true;
    deploy.forgejo.ci.enable = true;
  };

  runsForge = m: m.services.hyperhive.deploy.forgejo.enable && m.containers ? hive-forge;

  forgeClientIds =
    m:
    map (c: c.id) (
      lib.filter (
        c: c.id == m.services.hyperhive.swarm.forge.sso.clientId
      ) m.services.hyperhive.swarm.authelia.oidc.clients
    );

  # Matched on the option the message names, same reasoning as
  # ./grafana.nix's `grafanaRefusedFor`.
  refusedOver = m: needle: lib.any (a: !a.assertion && lib.hasInfix needle a.message) m.assertions;

  tokenFile = m: m.services.hyperhive.deploy.swarm-controller.forgeTokenFile;
  forgePath = "/var/lib/hyperhive-forge/swarm-controller.token";

  cases = [
    {
      # The absence the whole option exists for: a second forge in a swarm
      # is a split brain nobody notices, so a hive that has not been told it
      # is the forge's host runs none of its surface.
      name = "a hive that is not the forge's host runs no forge";
      ok =
        !bare.services.hyperhive.deploy.forgejo.enable
        && !(bare.containers ? hive-forge)
        && !(bare.systemd.services ? hive-forge-swarm-controller-token)
        && !(lib.elem "forge.t.local" bare.services.hyperhive.gateway.localNames)
        && !(refusedOver bare "deploy.forgejo.sso.clientSecretFile");
    }
    {
      name = "hosting the swarm's shared services runs the forge";
      ok = runsForge servicesHere;
    }
    {
      name = "the all-local mode runs the forge";
      ok = runsForge allLocal && lib.elem "forge.t.local" allLocal.services.hyperhive.gateway.localNames;
    }
    {
      name = "an explicit deploy.forgejo.enable runs the forge on its own";
      ok = runsForge forgeHere && !forgeHere.services.hyperhive.deploy.allSwarmServices;
    }
    {
      # `mkDefault`, not a plain assignment: the forge stays placeable on a
      # host of its own. `nats` is the control, so the case cannot pass on a
      # fixture where nothing came on.
      name = "placing the forge elsewhere survives the switch that would enable it";
      ok =
        !(servicesForgeElsewhere.containers ? hive-forge)
        && servicesForgeElsewhere.services.hyperhive.deploy.nats.enable;
    }
    {
      # A client is a row in authelia's config, so it is declared where
      # authelia runs. With the forge's module gated, registering it from
      # there would leave a split swarm's forge unknown to its IdP.
      name = "the forge's OIDC client is registered wherever authelia runs, and only there";
      ok =
        forgeClientIds servicesForgeElsewhere == [ "forgejo" ]
        && forgeClientIds allLocal == [ "forgejo" ]
        && forgeClientIds forgeNoAuthelia == [ ];
    }
    {
      name = "the forge's OIDC callback is the one forgejo sends";
      ok =
        servicesForgeElsewhere.services.hyperhive.swarm.forge.sso.redirectUri
        == "https://forge.t.local/user/oauth2/authelia/callback";
    }
    {
      # The runner reaches the forge through this host's gateway and is
      # registered through the local container. The second arm is the
      # control: a refusal that fires everywhere is not a check.
      name = "CI is refused on a host that does not run the forge";
      ok =
        refusedOver ciNoForge "deploy.forgejo.enable on the same host"
        && !(refusedOver ciWithForge "deploy.forgejo.enable on the same host");
    }
    {
      # Nothing writes the delivery path away from the forge, and a
      # `LoadCredential=` naming a missing path is fatal to the unit.
      name = "the controller's forge token defaults to the delivery path only where the forge runs";
      ok =
        tokenFile bare == null
        && tokenFile servicesForgeElsewhere == null
        && tokenFile forgeHere == forgePath
        && tokenFile allLocal == forgePath;
    }
  ];
in
runGroup "forge-placement" cases