lighttpd: add collectd submodule

nixos/modules/module-list.nix

@@ -586,6 +586,7 @@
   ./services/web-servers/fcgiwrap.nix
   ./services/web-servers/jboss/default.nix
   ./services/web-servers/lighttpd/cgit.nix
+  ./services/web-servers/lighttpd/collectd.nix
   ./services/web-servers/lighttpd/default.nix
   ./services/web-servers/lighttpd/gitweb.nix
   ./services/web-servers/lighttpd/inginious.nix

nixos/modules/services/web-servers/lighttpd/collectd.nix

@@ -0,0 +1,58 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.lighttpd.collectd;
+
+  collectionConf = pkgs.writeText "collection.conf" ''
+    datadir: "${config.services.collectd.dataDir}"
+    libdir: "${config.services.collectd.package}/lib/collectd"
+  '';
+
+  defaultCollectionCgi = config.services.collectd.package.overrideDerivation(old: {
+    name = "collection.cgi";
+    configurePhase = "true";
+    buildPhase = "true";
+    installPhase = ''
+      substituteInPlace contrib/collection.cgi --replace '"/etc/collection.conf"' '$ENV{COLLECTION_CONF}'
+      cp contrib/collection.cgi $out
+    '';
+  });
+in
+{
+
+  options.services.lighttpd.collectd = {
+
+    enable = mkEnableOption "collectd subservice accessible at http://yourserver/collectd";
+
+    collectionCgi = mkOption {
+      type = types.path;
+      default = defaultCollectionCgi;
+      description = ''
+        Path to collection.cgi script from (collectd sources)/contrib/collection.cgi
+        This option allows to use a customized version
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    services.lighttpd.enableModules = [ "mod_cgi" "mod_alias" "mod_setenv" ];
+
+    services.lighttpd.extraConfig = ''
+      $HTTP["url"] =~ "^/collectd" {
+        cgi.assign = (
+          ".cgi" => "${pkgs.perl}/bin/perl"
+        )
+        alias.url = (
+          "/collectd" => "${cfg.collectionCgi}"
+        )
+        setenv.add-environment = (
+          "PERL5LIB" => "${with pkgs; lib.makePerlPath [ perlPackages.CGI perlPackages.HTMLParser perlPackages.URI rrdtool ]}",
+          "COLLECTION_CONF" => "${collectionConf}"
+        )
+      }
+    '';
+  };
+
+}