fuuko/binary-cache: Add nar-serve

machines/fuuko/services/binary-cache.nix

@@ -8,7 +8,7 @@
 # ${XDG_CACHE_HOME:-$HOME/.cache}/.cache/nix/binary-cache-v6.sqlite and does
 # not re-check or invalidate them. Devices that often are not at home should
 # ensure that the cached priority is 50 to avoid slow substitutions.
-{ config, lib, ... }:
+{ config, lib, pkgs, ... }:
 let
   binaryCachePath = "/data/cache/nix-binary-cache";
 in
@@ -52,9 +52,43 @@ in
               auth_basic_user_file ${config.sops.secrets.nix-binary-cache-htpasswd.path};
           }
         '';
+        "/nix/store/".proxyPass = "http://localhost:${config.systemd.services.nar-serve.environment.PORT}";
       };
     };
   };
 
   systemd.services.nginx.serviceConfig.ReadWritePaths = lib.singleton binaryCachePath;
+
+  # TODO 21.05: Replace with upstream module
+  systemd.services.nar-serve =
+    let
+      # TODO: remove once new version is released and in nixpkgs
+      nar-serve = pkgs.unstable.nar-serve.overrideAttrs (o: o // {
+        version = "unstable-2021-04-08";
+
+        src = pkgs.fetchFromGitHub {
+          owner = "numtide";
+          repo = "nar-serve";
+          rev = "4243b0efa41910dfa4be8b9936ae460699d3f8f0";
+          sha256 = "0mjs3yilf5rixm67wk4h4jji54dsc0w3vfxd561pvfbxplbmgh3c";
+        };
+      });
+    in
+    {
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      environment = {
+        PORT = "8383";
+        NAR_CACHE_URL = "file://${binaryCachePath}";
+      };
+
+      serviceConfig = {
+        Restart = "always";
+        RestartSec = "5s";
+        ExecStart = "${nar-serve}/bin/nar-serve";
+        DynamicUser = true;
+        StandardOutput = "null"; # nar-server logs multiple lines on every request
+      };
+    };
 }