init prometheus module

modules/nixos/default.nix

@@ -3,5 +3,6 @@
   imports = [
     ./restic.nix
     ./vaultwarden.nix
+    ./prometheus.nix
   ];
 }

modules/nixos/prometheus.nix

@@ -0,0 +1,48 @@
+
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.custom.prometheus;
+in
+{
+  options = {
+    custom.prometheus = {
+      enable = mkEnableOption "Prometheus instance";
+      exporters = {
+        enable = mkOption {
+          type = types.bool;
+          default = false;
+          description = "Enable Prometheus exporter on every supported services";
+        };
+      };
+    };
+  };
+
+  config = {
+    services.prometheus = mkIf cfg.enable {
+      enable = true;
+      port = 9091;
+      exporters = {
+        node = {
+          enable = true;
+          enabledCollectors = [ "systemd" ];
+          port = 9100;
+        };
+      };
+      scrapeConfigs = [
+        { job_name = "prometheus";
+          static_configs = [
+            { targets = [ "localhost:${toString config.services.prometheus.port}" ]; }
+          ];
+        }
+        { job_name = "node";
+          static_configs = [
+            { targets = [ "localhost:${toString config.services.prometheus.exporters.node.port}" ]; }
+          ];
+        }
+      ];
+    };
+  };
+}