feat(gs/mugwump): Run xanthous server

Add a nixos module for running the xanthous server in a docker
container, and install it on mugwump including a prometheus scrape
config.

Change-Id: Ifeb315845b7eef2ee33af98fa3f71acdd3d9fe6b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3812
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

users/grfn/system/system/machines/mugwump.nix

@@ -7,6 +7,7 @@ with lib;
     ../modules/common.nix
     (modulesPath + "/installer/scan/not-detected.nix")
     "${depot.path}/ops/modules/prometheus-fail2ban-exporter.nix"
+    "${depot.path}/users/grfn/xanthous/server/module.nix"
   ];
 
   networking.hostName = "mugwump";
@@ -200,6 +201,12 @@ with lib;
       static_configs = [{
         targets = ["localhost:${toString config.services.prometheus.exporters.nginx.port}"];
       }];
+    } {
+      job_name = "xanthous_server";
+      scrape_interval = "1s";
+      static_configs = [{
+        targets = ["localhost:${toString config.services.xanthous-server.metricsPort}"];
+      }];
     } {
       job_name = "blackbox";
       metrics_path = "/probe";
@@ -226,6 +233,8 @@ with lib;
     }];
   };
 
+  services.xanthous-server.enable = true;
+
   virtualisation.docker.enable = true;
 
   services.buildkite-agents = listToAttrs (map (n: rec {

users/grfn/xanthous/server/docker.nix

@@ -6,7 +6,6 @@
 let
   inherit (depot.users.grfn) xanthous;
   xanthous-server = xanthous.server;
-
 in pkgs.dockerTools.buildLayeredImage {
   name = "xanthous-server";
   tag = "latest";
@@ -17,5 +16,4 @@ in pkgs.dockerTools.buildLayeredImage {
       "--xanthous-binary-path" "${xanthous}/bin/xanthous"
     ];
   };
-  ci = false;
 }

users/grfn/xanthous/server/module.nix

@@ -0,0 +1,41 @@
+{ config, lib, pkgs, depot, ... }:
+
+let
+  cfg = config.services.xanthous-server;
+in {
+  options = with lib; {
+    services.xanthous-server = {
+      enable = mkEnableOption "xanthous server";
+
+      port = mkOption {
+        type = types.int;
+        default = 2222;
+        description = "Port to listen to for SSH connections";
+      };
+
+      metricsPort = mkOption {
+        type = types.int;
+        default = 9000;
+        description = "Port to listen to for prometheus metrics";
+      };
+
+      image = mkOption {
+        type = types.package;
+        default = depot.users.grfn.xanthous.server.docker;
+        description = "OCI image file to run";
+      };
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    virtualisation.oci-containers.containers."xanthous-server" = {
+      autoStart = true;
+      image = "${cfg.image.imageName}:${cfg.image.imageTag}";
+      imageFile = cfg.image;
+      ports = [
+        "${toString cfg.port}:22"
+        "${toString cfg.metricsPort}:9000"
+      ];
+    };
+  };
+}