nixos/hail: init (#28442)

nixos/modules/module-list.nix

@@ -165,6 +165,7 @@
   ./services/continuous-integration/buildbot/master.nix
   ./services/continuous-integration/buildbot/worker.nix
   ./services/continuous-integration/buildkite-agent.nix
+  ./services/continuous-integration/hail.nix
   ./services/continuous-integration/hydra/default.nix
   ./services/continuous-integration/gitlab-runner.nix
   ./services/continuous-integration/gocd-agent/default.nix

nixos/modules/services/continuous-integration/hail.nix

@@ -0,0 +1,61 @@
+{ config, lib, pkgs, ...}:
+
+with lib;
+
+let
+  cfg = config.services.hail;
+in {
+
+
+  ###### interface
+
+  options.services.hail = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Enables the Hail Auto Update Service. Hail can automatically deploy artifacts
+        built by a Hydra Continous Integration server. A common use case is to provide
+        continous deployment for single services or a full NixOS configuration.'';
+    };
+    profile = mkOption {
+      type = types.str;
+      default = "hail-profile";
+      description = "The name of the Nix profile used by Hail.";
+    };
+    hydraJobUri = mkOption {
+      type = types.str;
+      description = "The URI of the Hydra Job.";
+    };
+    netrc = mkOption {
+      type = types.nullOr types.path;
+      description = "The netrc file to use when fetching data from Hydra.";
+      default = null;
+    };
+    package = mkOption {
+      type = types.package;
+      default = pkgs.haskellPackages.hail;
+      defaultText = "pkgs.haskellPackages.hail";
+      description = "Hail package to use.";
+    };
+  };
+
+
+  ###### implementation
+
+  config = mkIf cfg.enable {
+    systemd.services.hail = {
+      description = "Hail Auto Update Service";
+      wants = [ "network-online.target" ];
+      wantedBy = [ "multi-user.target" ];
+      path = with pkgs; [ nix ];
+      environment = {
+        HOME = "/var/lib/empty";
+      };
+      serviceConfig = {
+        ExecStart = "${cfg.package}/bin/hail --profile ${cfg.profile} --job-uri ${cfg.hydraJobUri}"
+          + lib.optionalString (cfg.netrc != null) " --netrc-file ${cfg.netrc}";
+      };
+    };
+  };
+}