Handle multiple modifications to distribution metrics correctly.

infra_libs/ts_mon/common/metric_store.py

 # Copyright 2015 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.
 
 import collections
 import logging
 import operator
 import threading
 import time
 
 from infra_libs.ts_mon.common import errors
 
 
 """A light-weight representation of a set or an incr.
 
 Args:
   name: The metric name.
   fields: The normalized field tuple.
   mod_type: Either 'set' or 'incr'.  Other values will raise
             UnknownModificationTypeError when it's used.
   args: (value, enforce_ge) for 'set' or (delta, modify_fn) for 'incr'.
 """  # pylint: disable=pointless-string-statement
 Modification = collections.namedtuple(
     'Modification', ['name', 'fields', 'mod_type', 'args'])
 
 
-def combine_modifications(old, new):
-  """Combines two modifications into one.
-
-  The returned modification will be the result as if the second modification had
-  been applied after the first.
-  """
-
-  if old is None or new.mod_type == 'set':
-    # A 'set' will override any previous value.
-    return new
-  elif new.mod_type == 'incr':
-    # For two 'incr's sum their delta args, for an 'incr' on top of a 'set' add
-    # the delta to the set value.
-    return Modification(
-        old.name, old.fields, old.mod_type,
-        (old.args[0] + new.args[0], old.args[1]))
-  else:
-    raise errors.UnknownModificationTypeError(new.mod_type)
-
-
 class MetricStore(object):
   """A place to store values for each metric.
 
   Several methods take "a normalized field tuple".  This is a tuple of
   (key, value) tuples sorted by key.  (The reason this is given as a tuple
   instead of a dict is because tuples are hashable and can be used as dict keys,
   dicts can not).
 
   The MetricStore is also responsible for keeping the start_time of each metric.
   This is what goes into the start_timestamp_us field in the MetricsData proto
@@ skipping 147 matching lines @@
 
   def reset_for_unittest(self, name=None):
     if name is not None:
       self._reset(name)
     else:
       for name in self._values.keys():
         self._reset(name)
 
   def _reset(self, name):
     self._values[name] = (self._start_time(name), {})