Generalize the ephemeral build managers so that any manager may manage a builder spawned by any other manager.

buildman/jobutil/buildjob.py

@@ -1,6 +1,9 @@
+import json
+
+from cachetools import lru_cache
+
 from data import model
 
-import json
 
 class BuildJobLoadException(Exception):
   """ Exception raised if a build job could not be instantiated for some reason. """
@@ -18,14 +21,22 @@ class BuildJob(object):
           'Could not parse build queue item config with ID %s' % self.job_details['build_uuid']
       )
 
+  @lru_cache(maxsize=1)
+  def _load_repo_build(self):
     try:
-      self.repo_build = model.get_repository_build(self.job_details['build_uuid'])
+      return model.get_repository_build(self.job_details['build_uuid'])
     except model.InvalidRepositoryBuildException:
       raise BuildJobLoadException(
           'Could not load repository build with ID %s' % self.job_details['build_uuid'])
 
+  @property
+  def repo_build(self):
+    return self._load_repo_build()
+
+  @property
+  def build_config(self):
     try:
-      self.build_config = json.loads(self.repo_build.job_config)
+      return json.loads(self.repo_build.job_config)
     except ValueError:
       raise BuildJobLoadException(
           'Could not parse repository build job config with ID %s' % self.job_details['build_uuid']