Stop creating stoppage alerts once a group has reached a certain size.

dashboard/dashboard/models/stoppage_alert.py

Index: dashboard/dashboard/models/stoppage_alert.py
diff --git a/dashboard/dashboard/models/stoppage_alert.py b/dashboard/dashboard/models/stoppage_alert.py
index 19240907d88bd38a396da7a10879580092c118e7..1055b67a7aac035e7852dfd31b2dae985d71a452 100644
--- a/dashboard/dashboard/models/stoppage_alert.py
+++ b/dashboard/dashboard/models/stoppage_alert.py
@@ -12,6 +12,8 @@ from dashboard import utils
 from dashboard.models import alert
 from dashboard.models import alert_group
 
+_MAX_GROUP_SIZE = 20
+
 
 class StoppageAlert(alert.Alert):
   """A stoppage alert is an alert for a Test no longer receiving new points.
@@ -90,8 +92,13 @@ def CreateStoppageAlert(test, row):
       id=row.revision,
       internal_only=test.internal_only,
       sheriff=test.sheriff)
+  alert_group.GroupAlerts([new_alert], test.suite_name, 'StoppageAlert')
+  grouped_alert_keys = StoppageAlert.query(
+      StoppageAlert.group == new_alert.group).fetch(keys_only=True)
+  if len(grouped_alert_keys) >= _MAX_GROUP_SIZE:
+    # Too many stoppage alerts in this group; we don't want to put any more.
+    return None

[chrisphan, 2015/11/06 18:06:42]

Does this need to always return an entity?

[qyearsley, 2015/11/06 18:11:08]

Nope, as is in this CL, CreateStoppageAlert decides whether or not an alert
should be created and returns None if there should be none created, and the
caller is then responsible for checking if it's None. (Docstring updated.) Does
this seem OK? 

   test.stoppage_alert = new_alert.key
   test.put()
-  alert_group.GroupAlerts([new_alert], test.suite_name, 'StoppageAlert')
   return new_alert