Resolve race condition between multiple log archivers

data/model/build.py

@@ -248,3 +248,13 @@ def get_archivable_build():
     return RepositoryBuild.get(id=found_id)
   except RepositoryBuild.DoesNotExist:
     return None
+
+
+def mark_build_archived(build_uuid):
+  """ Mark a build as archived, and return True if we were the ones who actually
+      updated the row. """
+  return (RepositoryBuild
+          .update(logs_archived=True)
+          .where(RepositoryBuild.uuid == build_uuid,
+                  RepositoryBuild.logs_archived == False)
+          .execute()) > 0