grafana: add minecraft server stats

services/grafana/exporters.nix

@@ -10,6 +10,9 @@ let
   jellyfinExporterPort = service_configs.ports.private.jellyfin_exporter.port;
   qbitExporterPort = service_configs.ports.private.qbittorrent_exporter.port;
   igpuExporterPort = service_configs.ports.private.igpu_exporter.port;
+  minecraftExporterPort = service_configs.ports.private.minecraft_exporter.port;
+  minecraftServerName = service_configs.minecraft.server_name;
+  minecraftServerPort = service_configs.ports.public.minecraft.port;
 in
 {
   # -- Jellyfin Prometheus Exporter --
@@ -109,4 +112,45 @@ in
       REFRESH_PERIOD_MS = "30000";
     };
   };
+
+  # -- Minecraft Prometheus Exporter --
+  # itzg/mc-monitor queries the local server via SLP on each scrape and exposes
+  # minecraft_status_{healthy,response_time_seconds,players_online_count,players_max_count}.
+  # mc-monitor binds to 0.0.0.0 (no listen-address flag); the firewall keeps
+  # 9567 internal and IPAddressAllow pins the socket to loopback as defense-in-depth.
+  systemd.services.minecraft-exporter =
+    lib.mkIf (config.services.grafana.enable && config.services.minecraft-servers.enable)
+      {
+        description = "Prometheus exporter for Minecraft (mc-monitor SLP)";
+        after = [
+          "network.target"
+          "minecraft-server-${minecraftServerName}.service"
+        ];
+        wantedBy = [ "multi-user.target" ];
+        serviceConfig = {
+          ExecStart = "${lib.getExe pkgs.mc-monitor} export-for-prometheus";
+          Restart = "on-failure";
+          RestartSec = "10s";
+          DynamicUser = true;
+          NoNewPrivileges = true;
+          ProtectSystem = "strict";
+          ProtectHome = true;
+          PrivateTmp = true;
+          MemoryDenyWriteExecute = true;
+          RestrictAddressFamilies = [
+            "AF_INET"
+            "AF_INET6"
+          ];
+          IPAddressAllow = [
+            "127.0.0.0/8"
+            "::1/128"
+          ];
+          IPAddressDeny = "any";
+        };
+        environment = {
+          EXPORT_SERVERS = "127.0.0.1:${toString minecraftServerPort}";
+          EXPORT_PORT = toString minecraftExporterPort;
+          TIMEOUT = "5s";
+        };
+      };
 }