[Culprit-Finder] Add generator cache decorator.

appengine/findit/util_scripts/crash_queries/crash_iterator.py

Index: appengine/findit/util_scripts/crash_queries/crash_iterator.py
diff --git a/appengine/findit/util_scripts/crash_queries/crash_iterator.py b/appengine/findit/util_scripts/crash_queries/crash_iterator.py
index 3a02e9a610a80dbda5f5d71b6a97e48b5d0dde4c..ffae0d1d2f03d2700cfc975fb4588b05da9c9811 100644
--- a/appengine/findit/util_scripts/crash_queries/crash_iterator.py
+++ b/appengine/findit/util_scripts/crash_queries/crash_iterator.py
@@ -8,27 +8,16 @@ from datetime import timedelta
 
 from crash.type_enums import CrashClient
 import iterator
+from libs.cache_decorator import GeneratorCached
+from local_cache import LocalCache
 from model.crash.cracas_crash_analysis import CracasCrashAnalysis
 from model.crash.fracas_crash_analysis import FracasCrashAnalysis
 
 _DEFAULT_BATCH_SIZE = 1000
 _TODAY = date.today().strftime('%Y-%m-%d')
 _A_YEAR_AGO = (date.today() - timedelta(days=365)).strftime('%Y-%m-%d')
-
-
-# TODO(katesonia): Switch to use fuction of objects encapsulating CrashClients,
-# after the refactoring is done.
-# TODO(crbug.com/662540): Add unittests.
-def GetAnalysisClassForClient(client_id):  # pragma: no cover.
-  if client_id == CrashClient.FRACAS:
-    return FracasCrashAnalysis
-  elif client_id == CrashClient.CRACAS:
-    return CracasCrashAnalysis
-  elif client_id == CrashClient.CLUSTERFUZZ:
-    # TODO(katesonia): Define ClusterfuzzCrashAnalysis.
-    return None
-
-  return None
+_CLIENT_TO_ANALYSIS_CLASS = {CrashClient.FRACAS: FracasCrashAnalysis,
+                             CrashClient.CRACAS: CracasCrashAnalysis}
 
 
 # TODO(crbug.com/662540): Add unittests.
@@ -39,7 +28,10 @@ def GetQueryForClient(client_id, property_values, start_date, end_date,
 
   start_date = datetime.strptime(start_date, datetime_pattern)
   end_date = datetime.strptime(end_date, datetime_pattern)
-  cls = GetAnalysisClassForClient(client_id)
+  cls = _CLIENT_TO_ANALYSIS_CLASS.get(client_id)
+  if not cls:
+    return None
+
   query = cls.query()
   for property_name, value in property_values.iteritems():
     query = query.filter(getattr(cls, property_name) == value)
@@ -80,7 +72,43 @@ def IterateCrashes(client_id,
     property_values = {}
 
   query = GetQueryForClient(client_id, property_values, start_date, end_date)
+  if not query:
+    return
+
   for crash in iterator.Iterate(query, app_id, fields=fields,
                                 batch_size=batch_size,
                                 batch_run=batch_run):
     yield crash
+
+
+@GeneratorCached(LocalCache(), namespace='Crash-iterator')  # pragma: no cover.
+def CachedCrashIterator(client_id, app_id,
+                        fields=None, property_values=None,
+                        start_date=_A_YEAR_AGO, end_date=_TODAY,
+                        batch_size=_DEFAULT_BATCH_SIZE, batch_run=False):
+  """Genrates query to query crashes and iterates crashes.
+
+  This iterator will check local cache first, if there is cache, iterate cached
+  values, else it will visit datastore of appengine app to yield data.
+
+  Args:
+    client_id (CrashClient): One of CrashClient.FRACAS, CrashClient.CRACAS,
+      CrashClient.CLUSTERFUZZ.
+    app_id (str): App engine app id.
+    fields (list): Field names of CrashAnalysis entity to project.
+    property_values (dict): Property values to filter.
+    start_date (str): Only iterate testcases after this date including this
+      date, format '%Y-%m-%d'.
+    end_date (str): Only iterate testcases before this date excluding this date,
+      format '%Y-%m-%d'.
+    batch_size (int): The number of crashes to query at one time.
+    batch_run (bool): If True, iterate batches of crashes, if
+      False, iterate each crash.
+
+    An example is available in crash_printer/print_crash.py.
+  """
+  for crash in IterateCrashes(client_id, app_id, fields=fields,
+                              property_values=property_values,
+                              start_date=start_date, end_date=end_date,
+                              batch_size=batch_size, batch_run=batch_run):
+    yield crash