chore(builders): localize builders specification like Hydra does

Signed-off-by: Raito Bezarius <raito@lix.systems>

buildbot_nix/__init__.py

@@ -3,6 +3,7 @@ import multiprocessing
 import os
 import sys
 import graphlib
+import base64
 from collections.abc import Generator
 from dataclasses import dataclass
 from pathlib import Path
@@ -36,6 +37,26 @@ log = Logger()
 
 FLAKE_TARGET_ATTRIBUTE_FOR_JOBS = "buildbotJobs"
 
+@dataclass
+class NixBuilder:
+    protocol: str
+    hostName: str
+    maxJobs: int
+    speedFactor: int = 1
+    # without base64
+    publicHostKey: str | None = None
+    sshUser: str | None = None
+    sshKey: str | None = None
+    systems: list[str] = ["-"]
+    supportedFeatures: list[str] = ["-"]
+    mandatoryFeatures: list[str] = ["-"]
+
+    def to_nix_line(self):
+        encoded_public_key = base64.b64encode(self.publicHostKey.encode('ascii')).decode('ascii') if self.publicHostKey is not None else "-"
+        fullConnection = f"{self.protocol}://{self.sshUser}@{self.hostName}" if self.sshUser is not None else self.hostName
+        return f"{fullConnection} {",".join(self.systems)} {self.sshKey or "-"} {self.maxJobs} {self.speedFactor} {",".join(self.supportedFeatures)} {",".join(self.mandatoryFeatures)} {encoded_public_key}"
+
+
 @dataclass
 class OAuth2Config:
     name: str
@@ -499,6 +520,7 @@ def nix_build_config(
     project: GerritProject,
     worker_arch: str,
     worker_names: list[str],
+    builders_spec: str,
     signing_keyfile: str | None = None,
     binary_cache_config: S3BinaryCacheConfig | None = None
 ) -> util.BuilderConfig:
@@ -522,6 +544,8 @@ def nix_build_config(
                 "--max-silent-time",
                 str(60 * 20),
                 "--accept-flake-config",
+                "--builders",
+                builders_spec,
                 "--out-link",
                 util.Interpolate("result-%(prop:attr)s"),
                 util.Interpolate("%(prop:drv_path)s^*"),
@@ -618,6 +642,7 @@ def config_for_project(
     nix_eval_worker_count: int,
     nix_eval_max_memory_size: int,
     eval_lock: util.MasterLock,
+    builders_spec: str,
     signing_keyfile: str | None = None,
     binary_cache_config: S3BinaryCacheConfig | None = None
 ) -> Project:
@@ -680,6 +705,7 @@ def config_for_project(
                     project,
                     arch,
                     [ f"{w}-{arch}" for w in worker_names ],
+                    builders_spec,
                     signing_keyfile=signing_keyfile,
                     binary_cache_config=binary_cache_config
                 )
@@ -757,6 +783,7 @@ class GerritNixConfigurator(ConfiguratorBase):
         projects: list[str],
         url: str,
         allowed_origins: list[str],
+        nix_builders: list[dict[str, Any]],
         nix_supported_systems: list[str],
         nix_eval_worker_count: int | None,
         nix_eval_max_memory_size: int,
@@ -780,6 +807,7 @@ class GerritNixConfigurator(ConfiguratorBase):
         self.nix_eval_max_memory_size = nix_eval_max_memory_size
         self.nix_eval_worker_count = nix_eval_worker_count
         self.nix_supported_systems = nix_supported_systems
+        self.nix_builders: list[NixBuilder] = [NixBuilder(**builder_cfg) for builder_cfg in nix_builders]
 
         self.gerrit_change_source = GerritChangeSource(gerrit_server, gerrit_user, gerritport=gerrit_port, identity_file=gerrit_sshkey_path)
 
@@ -814,6 +842,7 @@ class GerritNixConfigurator(ConfiguratorBase):
 
         eval_lock = util.MasterLock("nix-eval")
 
+        builders_spec = " ; ".join(builder.to_nix_line() for builder in self.nix_builders)
         for project in self.projects:
             config_for_project(
                 config,
@@ -824,6 +853,7 @@ class GerritNixConfigurator(ConfiguratorBase):
                 self.nix_eval_worker_count or multiprocessing.cpu_count(),
                 self.nix_eval_max_memory_size,
                 eval_lock,
+                builders_spec,
                 signing_keyfile=self.signing_keyfile,
                 binary_cache_config=self.binary_cache_config
             )

nix/coordinator.nix

@@ -1,4 +1,5 @@
 { config
+, options
 , pkgs
 , lib
 , ...
@@ -15,11 +16,17 @@ in
         default = "postgresql://@/buildbot";
         description = "Postgresql database url";
       };
+
       workersFile = lib.mkOption {
         type = lib.types.path;
         description = "File containing a list of nix workers";
       };
 
+      buildMachines = lib.mkOption {
+        type = options.nix.buildMachines.type;
+        description = "List of local remote builders machines associated to that Buildbot instance";
+      };
+
       oauth2 = {
         name = lib.mkOption {
           type = lib.types.str;
@@ -216,6 +223,7 @@ in
               nix_eval_max_memory_size=${builtins.toJSON cfg.evalMaxMemorySize},
               nix_eval_worker_count=${if cfg.evalWorkerCount == null then "None" else builtins.toString cfg.evalWorkerCount},
               nix_supported_systems=${builtins.toJSON cfg.buildSystems},
+              nix_builders=${builtins.toJSON cfg.buildMachines},
               # Signing key file must be available on the workers and readable.
               signing_keyfile=${if cfg.signingKeyFile == null then "None" else builtins.toJSON cfg.signingKeyFile},
               binary_cache_config=${if (!cfg.binaryCache.enable) then "None" else builtins.toJSON {