statsd: restore support for {influx,librato,stackdriver} backends

These packages will be placed into an environment using
`backendsToPackages`. This function explicitly maps backends to
`pkgs.nodePackages.${type}` unless it's a builtin. This ensures that only
valid backends that work on NixOS are used (if not, the build already
breaks at evaluation time).

The log will be redirected to `stdout` to be able to watch the entire
output using `journalctl`.

Configuration parameters for the backends need to be set using
`services.statsd.extraConfig` as each backend has its own options and
all of them shouldn't be validated and checked explicitly and manually.

1 files changed, 22 insertions, 9 deletions

diff --git a/nixos/modules/services/monitoring/statsd.nix b/nixos/modules/services/monitoring/statsd.nix
index df2adb9f2766..7b0e9981cbb1 100644
--- a/nixos/modules/services/monitoring/statsd.nix
+++ b/nixos/modules/services/monitoring/statsd.nix
@@ -9,6 +9,12 @@ let
   isBuiltinBackend = name:
     builtins.elem name [ "graphite" "console" "repeater" ];
 
+  backendsToPackages = let
+    mkMap = list: name:
+      if isBuiltinBackend name then list
+      else list ++ [ pkgs.nodePackages.${name} ];
+  in foldl mkMap [];
+
   configFile = pkgs.writeText "statsd.conf" ''
     {
       address: "${cfg.listenAddress}",
@@ -27,13 +33,21 @@ let
         prettyprint: false
       },
       log: {
-        backend: "syslog"
+        backend: "stdout"
       },
       automaticConfigReload: false${optionalString (cfg.extraConfig != null) ","}
       ${cfg.extraConfig}
     }
   '';
 
+  deps = pkgs.buildEnv {
+    name = "statsd-runtime-deps";
+    pathsToLink = [ "/lib" ];
+    ignoreCollisions = true;
+
+    paths = backendsToPackages cfg.backends;
+  };
+
 in
 
 {
@@ -42,11 +56,7 @@ in
 
   options.services.statsd = {
 
-    enable = mkOption {
-      description = "Whether to enable statsd stats aggregation service";
-      default = false;
-      type = types.bool;
-    };
+    enable = mkEnableOption "statsd";
 
     listenAddress = mkOption {
       description = "Address that statsd listens on over UDP";
@@ -110,6 +120,11 @@ in
 
   config = mkIf cfg.enable {
 
+    assertions = map (backend: {
+      assertion = !isBuiltinBackend backend -> hasAttrByPath [ backend ] pkgs.nodePackages;
+      message = "Only builtin backends (graphite, console, repeater) or backends enumerated in `pkgs.nodePackages` are allowed!";
+    }) cfg.backends;
+
     users.extraUsers = singleton {
       name = "statsd";
       uid = config.ids.uids.statsd;
@@ -120,9 +135,7 @@ in
       description = "Statsd Server";
       wantedBy = [ "multi-user.target" ];
       environment = {
-        NODE_PATH=concatMapStringsSep ":"
-          (pkg: "${builtins.getAttr pkg pkgs.statsd.nodePackages}/lib/node_modules")
-          (filter (name: !isBuiltinBackend name) cfg.backends);
+        NODE_PATH = "${deps}/lib/node_modules";
       };
       serviceConfig = {
         ExecStart = "${pkgs.statsd}/bin/statsd ${configFile}";