Merge pull request #43812 from binarin/epmd-systemd-pr

epmd: Introduce erlang port mapper daemon service

nixos/modules/module-list.nix

@@ -496,6 +496,7 @@
   ./services/networking/dnsdist.nix
   ./services/networking/dnsmasq.nix
   ./services/networking/ejabberd.nix
+  ./services/networking/epmd.nix
   ./services/networking/fakeroute.nix
   ./services/networking/ferm.nix
   ./services/networking/firefox/sync-server.nix

nixos/modules/services/networking/epmd.nix

@@ -0,0 +1,56 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.epmd;
+
+in
+
+{
+  ###### interface
+  options.services.epmd = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether to enable socket activation for Erlang Port Mapper Daemon (epmd),
+        which acts as a name server on all hosts involved in distributed
+        Erlang computations.
+      '';
+    };
+    package = mkOption {
+      type = types.package;
+      default = pkgs.erlang;
+      description = ''
+        The Erlang package to use to get epmd binary. That way you can re-use
+        an Erlang runtime that is already installed for other purposes.
+      '';
+    };
+  };
+
+  ###### implementation
+  config = mkIf cfg.enable {
+    systemd.sockets.epmd = rec {
+      description = "Erlang Port Mapper Daemon Activation Socket";
+      wantedBy = [ "sockets.target" ];
+      before = wantedBy;
+      socketConfig = {
+        ListenStream = "4369";
+        Accept = "false";
+      };
+    };
+
+    systemd.services.epmd = {
+      description = "Erlang Port Mapper Daemon";
+      after = [ "network.target" ];
+      requires = [ "epmd.socket" ];
+
+      serviceConfig = {
+        DynamicUser = true;
+        ExecStart = "${cfg.package}/bin/epmd -systemd";
+        Type = "notify";
+      };
+    };
+  };
+}

pkgs/development/interpreters/erlang/generic-builder.nix

@@ -3,6 +3,7 @@
 , openjdk ? null # javacSupport
 , unixODBC ? null # odbcSupport
 , libGLU_combined ? null, wxGTK ? null, wxmac ? null, xorg ? null # wxSupport
+, withSystemd ? stdenv.isLinux, systemd # systemd support in epmd
 }:
 
 { baseName ? "erlang"
@@ -53,6 +54,7 @@ in stdenv.mkDerivation ({
     ++ optionals wxSupport wxPackages2
     ++ optionals odbcSupport odbcPackages
     ++ optionals javacSupport javacPackages
+    ++ optional withSystemd systemd
     ++ optionals stdenv.isDarwin (with pkgs.darwin.apple_sdk.frameworks; [ Carbon Cocoa ]);
 
   debugInfo = enableDebugInfo;
@@ -84,6 +86,7 @@ in stdenv.mkDerivation ({
     ++ optional javacSupport "--with-javac"
     ++ optional odbcSupport "--with-odbc=${unixODBC}"
     ++ optional wxSupport "--enable-wx"
+    ++ optional withSystemd "--enable-systemd"
     ++ optional stdenv.isDarwin "--enable-darwin-64bit";
 
   # install-docs will generate and install manpages and html docs