make version of ts_mon compatible with appengine

infra_libs/ts_mon/interface.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.
 
 """Classes representing the monitoring interface for tasks or devices.
 
 Usage:
   import argparse
   from infra_libs import ts_mon
 
@@ skipping 21 matching lines @@
 """
 
 import logging
 import os
 import random
 import threading
 import time
 
 from monacq.proto import metrics_pb2
 
-from infra_libs.ts_mon import errors
+from infra_libs.ts_mon.common import errors
 
 # The maximum number of MetricsData messages to include in each HTTP request.
 # MetricsCollections larger than this will be split into multiple requests.
 METRICS_DATA_LENGTH_LIMIT = 5000
 
 
 class State(object):
   """Package-level state is stored here so that it is easily accessible.
 
   Configuration is kept in this one object at the global level so that all
@@ skipping 56 matching lines @@
 
 
 def register(metric):
   """Adds the metric to the list of metrics sent by flush().
 
   This is called automatically by Metric's constructor - you don't need to call
   it manually.
   """
   # If someone is registering the same metric object twice, that's okay, but
   # registering two different metric objects with the same metric name is not.
-  if metric in state.metrics:
-    return
+  for m in state.metrics:
+    if metric == m:
+      return

[agable, 2015/08/19 01:14:42]

I don't think this does what we want: This means that the registration will be
successful, but the newly-created Metric object will not be added to the global
state, so when flush() is called any data points which have been added to it
won't get sent.

I think what we actually want to do is

here:
if metric == m:
  return m

and in the Metric constructor call interface.register() and if that returns
something then replace ourselves with that. Note that this may require
implementing __new__ as well as __init__.

   if any([metric._name == m._name for m in state.metrics]):
     raise errors.MonitoringDuplicateRegistrationError(metric._name)
 
   state.metrics.add(metric)
 
 
 def unregister(metric):
   """Removes the metric from the list of metrics sent by flush()."""
   state.metrics.remove(metric)
 
@@ skipping 45 matching lines @@
             'Last monitoring flush took %f seconds (longer than '
             '--ts-mon-flush-interval-secs = %f seconds)',
             flush_duration, self.interval_secs)
         next_timeout = 0
 
   def stop(self):
     """Stops the background thread and performs a final flush."""
 
     self.stop_event.set()
     self.join()