[Findit] Add a sub-pipeline to detect first-known failure.

appengine/findit/model/base_build_model.py

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from google.appengine.ext import ndb
+
+
+class BaseBuildModel(ndb.Model):  # pragma: no cover
+  """A base class to provide computed properties from the key.
+
+  The computed properties are master name, builder name, and build number.
+  Subclasses should set its key as:
+    build_id = BaseBuildModel.CreateBuildId(
+        master_name, builder_name, build_number)
+    ndb.Key('KindName', build_id, 'Optional_KindName', optional_id, ...)
+  """
+
+  @staticmethod
+  def CreateBuildId(master_name, builder_name, build_number):
+    return '%s/%s/%s' % (master_name, builder_name, build_number)
+
+  @ndb.ComputedProperty
+  def master_name(self):
+    return self.key.pairs()[0][1].split('/')[0]
+
+  @ndb.ComputedProperty
+  def builder_name(self):
+    return self.key.pairs()[0][1].split('/')[1]
+
+  @ndb.ComputedProperty
+  def build_number(self):
+    return int(self.key.pairs()[0][1].split('/')[2])