nixos: add collectd module

nixos/modules/misc/ids.nix

@@ -151,6 +151,7 @@
       dnsmasq = 141;
       uhub = 142;
       yandexdisk=143;
+      collectd=144;
 
       # When adding a uid, make sure it doesn't match an existing gid. And don't use uids above 399!
 

nixos/modules/module-list.nix

@@ -179,6 +179,7 @@
   ./services/misc/uhub.nix
   ./services/misc/zookeeper.nix
   ./services/monitoring/apcupsd.nix
+  ./services/monitoring/collectd.nix
   ./services/monitoring/dd-agent.nix
   ./services/monitoring/graphite.nix
   ./services/monitoring/monit.nix

nixos/modules/services/monitoring/collectd.nix

@@ -0,0 +1,104 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.services.collectd;
+
+  conf = pkgs.writeText "collectd.conf" ''
+    BaseDir "${cfg.dataDir}"
+    PIDFile "${cfg.dataDir}/collectd.pid"
+    AutoLoadPlugin ${if cfg.autoLoadPlugin then "true" else "false"}
+    Hostname ${config.networking.hostName}
+
+    LoadPlugin syslog
+    <Plugin "syslog">
+      LogLevel "info"
+      NotifyLevel "OKAY"
+    </Plugin>
+
+    ${concatMapStrings (f: ''
+    Include "${f}"
+    '') cfg.include}
+
+    ${cfg.extraConfig}
+  '';
+
+in {
+  options.services.collectd = with types; {
+    enable = mkOption {
+      default = false;
+      description = ''
+        Whether to enable collectd agent.
+      '';
+      type = bool;
+    };
+
+    user = mkOption {
+      default = "collectd";
+      description = ''
+        User under which to run collectd.
+      '';
+      type = nullOr str;
+    };
+
+    dataDir = mkOption {
+      default = "/var/lib/collectd";
+      description = ''
+        Data directory for collectd agent.
+      '';
+      type = path;
+    };
+
+    autoLoadPlugin = mkOption {
+      default = false;
+      description = ''
+        Enable plugin autoloading.
+      '';
+      type = bool;
+    };
+
+    include = mkOption {
+      default = [];
+      description = ''
+        Additional paths to load config from.
+      '';
+      type = listOf str;
+    };
+
+    extraConfig = mkOption {
+      default = "";
+      description = ''
+        Extra configuration for collectd.
+      '';
+      type = lines;
+    };
+
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.collectd = {
+      description = "Collectd Monitoring Agent";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      serviceConfig = {
+        ExecStart = "${pkgs.collectd}/sbin/collectd -C ${conf} -P ${cfg.dataDir}/collectd.pid";
+        Type = "forking";
+        PIDFile = "${cfg.dataDir}/collectd.pid";
+        User = optional (cfg.user!="root") cfg.user;
+        PermissionsStartOnly = true;
+      };
+
+      preStart = ''
+        mkdir -m 0700 -p ${cfg.dataDir}
+        if [ "$(id -u)" = 0 ]; then chown -R ${cfg.user} ${cfg.dataDir}; fi
+      '';
+    }; 
+
+    users.extraUsers = optional (cfg.user == "collectd") {
+      name = "collectd";
+      uid = config.ids.uids.collectd;
+    };
+  };
+}