From 13a3b25ee8a24ac6d7a5e0b7cb5021d89b09e365 Mon Sep 17 00:00:00 2001
From: oxalica <oxalicc@pm.me>
Date: Fri, 28 Mar 2025 14:22:35 -0400
Subject: [PATCH] Update nix module and config examples for socket activation

---
 blahd/config.example.toml |  2 --
 contrib/module.nix        | 21 ++++++++++++++++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/blahd/config.example.toml b/blahd/config.example.toml
index b96691a..7f4e062 100644
--- a/blahd/config.example.toml
+++ b/blahd/config.example.toml
@@ -24,8 +24,6 @@ address = "localhost:8080"
 
 # Use systemd socket activation mechanism to get listener fd from envvars.
 # See also sd_listen_fds(3) and systemd.socket(5).
-# NB. Currently only TCP sockets are supported. UNIX domain socket support is
-# blocked by axum 0.5, see https://github.com/tokio-rs/axum/pull/2941
 #systemd = true
 
 [server]
diff --git a/contrib/module.nix b/contrib/module.nix
index 5c05313..8e90e67 100644
--- a/contrib/module.nix
+++ b/contrib/module.nix
@@ -47,6 +47,17 @@ in
       defaultText = literalMD "blahd package from its flake output";
     };
 
+    listen = mkOption {
+      description = mdDoc ''
+        The address:port or an absolute UNIX socket path to listen on.
+
+        If not null, it sets {option}`services.blahd.settings.listen.systemd`
+        to `true`, and systemd socket activation is configured.
+      '';
+      type = types.nullOr types.str;
+      default = "/run/blahd/blahd.sock";
+    };
+
     settings = mkOption {
       description = ''
         blahd configuration.
@@ -70,14 +81,22 @@ in
     systemd.packages = [ cfg.package ];
     environment.systemPackages = [ cfg.package ];
 
+    systemd.sockets."blahd" = lib.mkIf (cfg.listen != null) {
+      wantedBy = [ "sockets.target" ];
+      listenStreams = [ cfg.listen ];
+    };
+
     systemd.services."blahd" = lib.mkDefault {
       overrideStrategy = "asDropin";
 
-      wantedBy = [ "multi-user.target" ];
       restartIfChanged = true; # We support graceful shutdown.
       stopIfChanged = false;
     };
 
     environment.etc."blahd/blahd.toml".source = cfg.settingsFile;
+
+    services.blahd.settings = lib.mkIf (cfg.listen != null) {
+      listen.systemd = true;
+    };
   };
 }