tools/telemetry/third_party/webpagereplay/util.py

   1 #!/usr/bin/env python
   2 # Copyright 2012 Google Inc. All Rights Reserved.
   3 #
   4 # Licensed under the Apache License, Version 2.0 (the "License");
   5 # you may not use this file except in compliance with the License.
   6 # You may obtain a copy of the License at
   7 #
   8 #      http://www.apache.org/licenses/LICENSE-2.0
   9 #
  10 # Unless required by applicable law or agreed to in writing, software
  11 # distributed under the License is distributed on an "AS IS" BASIS,
  12 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13 # See the License for the specific language governing permissions and
  14 # limitations under the License.
  15
  16
  17 """Miscellaneous utility functions."""
  18
  19 import inspect
  20 import logging
  21 import time
  22
  23 try:
  24   # pkg_resources (part of setuptools) is needed when WPR is
  25   # distributed as a package. (Resources may need to be extracted from
  26   # the package.)
  27
  28   import pkg_resources
  29
  30   def resource_exists(resource_name):
  31     return pkg_resources.resource_exists(__name__, resource_name)
  32
  33   def resource_string(resource_name):
  34     return pkg_resources.resource_string(__name__, resource_name)
  35
  36 except ImportError:
  37   # Import of pkg_resources failed, so fall back to getting resources
  38   # from the file system.
  39
  40   import os
  41
  42   def _resource_path(resource_name):
  43     _replay_dir = os.path.dirname(os.path.abspath(__file__))
  44     return os.path.join(_replay_dir, resource_name)
  45
  46   def resource_exists(resource_name):
  47     return os.path.exists(_resource_path(resource_name))
  48
  49   def resource_string(resource_name):
  50     return open(_resource_path(resource_name)).read()
  51
  52
  53 class TimeoutException(Exception):
  54   pass
  55
  56
  57 def WaitFor(condition, timeout):
  58   """Waits for up to |timeout| secs for the function |condition| to return True.
  59
  60   Polling frequency is (elapsed_time / 10), with a min of .1s and max of 5s.
  61
  62   Returns:
  63     Result of |condition| function (if present).
  64   """
  65   min_poll_interval = 0.1
  66   max_poll_interval = 5
  67   output_interval = 300
  68
  69   def GetConditionString():
  70     if condition.__name__ == '<lambda>':
  71       try:
  72         return inspect.getsource(condition).strip()
  73       except IOError:
  74         pass
  75     return condition.__name__
  76
  77   start_time = time.time()
  78   last_output_time = start_time
  79   while True:
  80     res = condition()
  81     if res:
  82       return res
  83     now = time.time()
  84     elapsed_time = now - start_time
  85     last_output_elapsed_time = now - last_output_time
  86     if elapsed_time > timeout:
  87       raise TimeoutException('Timed out while waiting %ds for %s.' %
  88                                         (timeout, GetConditionString()))
  89     if last_output_elapsed_time > output_interval:
  90       logging.info('Continuing to wait %ds for %s. Elapsed: %ds.',
  91                    timeout, GetConditionString(), elapsed_time)
  92       last_output_time = time.time()
  93     poll_interval = min(max(elapsed_time / 10., min_poll_interval),
  94                         max_poll_interval)
  95     time.sleep(poll_interval)