telegraf: init module

modules/module-list.nix

@@ -48,6 +48,7 @@
   ./services/lorri.nix
   ./services/mail/offlineimap.nix
   ./services/mopidy.nix
+  ./services/monitoring/telegraf.nix
   ./services/nix-daemon.nix
   ./services/nix-gc
   ./services/ofborg

modules/services/monitoring/telegraf.nix

@@ -0,0 +1,71 @@
+{ config, lib, pkgs, ... }:
+
+let
+  inherit (lib) mkEnableOption mkOption types mkIf;
+
+  cfg = config.services.telegraf;
+
+  settingsFormat = pkgs.formats.toml { };
+  configFile = settingsFormat.generate "config.toml" cfg.extraConfig;
+in {
+  options = {
+    services.telegraf = {
+      enable = mkEnableOption "telegraf agent";
+
+      package = mkOption {
+        default = pkgs.telegraf;
+        defaultText = lib.literalExpression "pkgs.telegraf";
+        description = "Which telegraf derivation to use";
+        type = types.package;
+      };
+
+      environmentFiles = mkOption {
+        type = types.listOf types.path;
+        default = [ ];
+        example = [ "/run/keys/telegraf.env" ];
+        description = ''
+          File to load as environment file.
+          This is useful to avoid putting secrets into the nix store.
+        '';
+      };
+
+      extraConfig = mkOption {
+        default = { };
+        description = "Extra configuration options for telegraf";
+        type = settingsFormat.type;
+        example = {
+          outputs.influxdb = {
+            urls = [ "http://localhost:8086" ];
+            database = "telegraf";
+          };
+          inputs.statsd = {
+            service_address = ":8125";
+            delete_timings = true;
+          };
+        };
+      };
+
+      configUrl = mkOption {
+        default = null;
+        description = "Url to fetch config from";
+        type = types.nullOr types.str;
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    launchd.daemons.telegraf = {
+      script = ''
+        ${lib.concatStringsSep "\n"
+        (map (file: "source ${file}") cfg.environmentFiles)}
+        ${cfg.package}/bin/telegraf --config ${
+          if cfg.configUrl == null then configFile else cfg.configUrl
+        }
+      '';
+      serviceConfig = {
+        KeepAlive = true;
+        RunAtLoad = true;
+      };
+    };
+  };
+}