Centralize the config for buildMachines.

nix/configuration/configuration.nix

@@ -16,6 +16,7 @@
     ./roles/boot
     ./roles/chromecast
     ./roles/chromium
+    ./roles/distributed_build
     ./roles/docker
     ./roles/ecc
     ./roles/emacs

nix/configuration/hosts/odo/distributed_build.nix

@@ -9,48 +9,19 @@
 
   config = lib.mkMerge [
     {
-      nix.distributedBuilds = true;
+      me.distributed_build.enable = true;
-      nix.buildMachines = [
+      me.distributed_build.machines.hydra = {
-        {
+        enable = true;
-          hostName = "hydra";
+        additional_config = {
-          sshUser = "nixworker";
-          systems = [
-            "x86_64-linux"
-            # "aarch64-linux"
-          ];
-          maxJobs = 1;
           speedFactor = 2;
-          supportedFeatures = [
+        };
-            # "nixos-test"
+      };
-            "benchmark"
+      me.distributed_build.machines.quark = {
-            "big-parallel"
+        enable = true;
-            # "kvm"
+        additional_config = {
-            "gccarch-x86-64-v3"
-            "gccarch-x86-64-v4"
-            "gccarch-znver4"
-          ];
-        }
-        {
-          hostName = "quark";
-          sshUser = "nixworker";
-          systems = [
-            "x86_64-linux"
-            # "aarch64-linux"
-          ];
-          maxJobs = 1;
           speedFactor = 2;
-          supportedFeatures = [
+        };
-            # "nixos-test"
+      };
-            "benchmark"
-            "big-parallel"
-            # "kvm"
-            "gccarch-x86-64-v3"
-            "gccarch-x86-64-v4"
-            "gccarch-znver4"
-            "gccarch-znver5"
-          ];
-        }
-      ];
     }
   ];
 }

nix/configuration/hosts/quark/distributed_build.nix

@@ -9,28 +9,13 @@
 
   config = lib.mkMerge [
     {
-      nix.distributedBuilds = true;
+      me.distributed_build.enable = true;
-      nix.buildMachines = [
+      me.distributed_build.machines.hydra = {
-        {
+        enable = true;
-          hostName = "hydra";
+        additional_config = {
-          sshUser = "nixworker";
-          systems = [
-            "x86_64-linux"
-            # "aarch64-linux"
-          ];
-          maxJobs = 1;
           speedFactor = 2;
-          supportedFeatures = [
+        };
-            # "nixos-test"
+      };
-            "benchmark"
-            "big-parallel"
-            # "kvm"
-            "gccarch-x86-64-v3"
-            "gccarch-x86-64-v4"
-            "gccarch-znver4"
-          ];
-        }
-      ];
     }
   ];
 }

nix/configuration/roles/distributed_build/default.nix

@@ -0,0 +1,104 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  make_machine_config = name: {
+    enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to use the ${name} machine during distributed builds.";
+    };
+
+    additional_config = lib.mkOption {
+      type = lib.types.attrs;
+      default = { };
+      example = lib.literalExpression {
+        speedFactor = 2;
+      };
+      description = "Additional config values for the buildMachines entry. For example, speedFactor.";
+    };
+  };
+in
+{
+  imports = [ ];
+
+  options.me = {
+    distributed_build.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to use multiple machines to perform a nixos-rebuild.";
+    };
+
+    distributed_build.machines.hydra = make_machine_config "hydra";
+    distributed_build.machines.quark = make_machine_config "quark";
+  };
+
+  config = lib.mkIf config.me.distributed_build.enable (
+    lib.mkMerge [
+      {
+        nix.distributedBuilds = true;
+      }
+      (lib.mkIf config.me.distributed_build.machines.hydra.enable {
+        nix.buildMachines = [
+          (
+            {
+              hostName = "hydra";
+              sshUser = "nixworker";
+              # sshKey = "";
+              # publicHostKey = "";
+              systems = [
+                "x86_64-linux"
+                # "aarch64-linux"
+              ];
+              maxJobs = 1;
+              supportedFeatures = [
+                # "nixos-test"
+                "benchmark"
+                "big-parallel"
+                # "kvm"
+                "gccarch-x86-64-v3"
+                "gccarch-x86-64-v4"
+                "gccarch-znver4"
+              ];
+            }
+            // config.me.distributed_build.machines.hydra.additional_config
+          )
+        ];
+      })
+      (lib.mkIf config.me.distributed_build.machines.quark.enable {
+        nix.buildMachines = [
+          (
+            {
+              hostName = "quark";
+              sshUser = "nixworker";
+              # sshKey = "";
+              # publicHostKey = "";
+              systems = [
+                "x86_64-linux"
+                # "aarch64-linux"
+              ];
+              maxJobs = 1;
+              supportedFeatures = [
+                # "nixos-test"
+                "benchmark"
+                "big-parallel"
+                # "kvm"
+                "gccarch-x86-64-v3"
+                "gccarch-x86-64-v4"
+                "gccarch-znver4"
+                "gccarch-znver5"
+              ];
+            }
+            // config.me.distributed_build.machines.quark.additional_config
+          )
+        ];
+      })
+    ]
+  );
+}