l 3: add telegraf service

lass/3modules/default.nix

@@ -9,5 +9,6 @@ _:
     ./urxvtd.nix
     ./usershadow.nix
     ./xresources.nix
+    ./telegraf.nix
   ];
 }

lass/3modules/telegraf.nix

@@ -0,0 +1,67 @@
+{ config, lib, pkgs, ... }:
+
+with builtins;
+with lib;
+
+let
+  cfg = config.lass.telegraf;
+
+  out = {
+    options.lass.telegraf = api;
+    config = mkIf cfg.enable imp;
+  };
+
+  api = {
+    enable = mkEnableOption "telegraf";
+    dataDir = mkOption {
+      type = types.str;
+      default = "/var/lib/telegraf";
+    };
+    user = mkOption {
+      type = types.str;
+      default = "telegraf";
+    };
+    config = mkOption {
+      type = types.str;
+      #TODO: find a good default
+      default = ''
+        [agent]
+            interval = "1s"
+
+        [outputs]
+
+        # Configuration to send data to InfluxDB.
+        [outputs.influxdb]
+            urls = ["http://localhost:8086"]
+            database = "kapacitor_example"
+            user_agent = "telegraf"
+
+        # Collect metrics about cpu usage
+        [cpu]
+            percpu = false
+            totalcpu = true
+            drop = ["cpu_time"]
+      '';
+      description = "configuration telegraf is started with";
+    };
+  };
+
+  configFile = pkgs.writeText "telegraf.conf" cfg.config;
+
+  imp = {
+
+    systemd.services.telegraf = {
+      description = "telegraf";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      restartIfChanged = true;
+
+      serviceConfig = {
+        Restart = "always";
+        ExecStart = "${pkgs.telegraf}/bin/telegraf -config ${configFile}";
+      };
+    };
+  };
+
+in out