[Common] Move WaitFor from telemetry to common/py_utils

common/py_utils/py_utils/__init__.py

 #!/usr/bin/env python
 
 # Copyright (c) 2016 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 functools
+import inspect
+import logging
 import os
 import sys
+import time
 
 
 def GetCatapultDir():
   return os.path.normpath(
       os.path.join(os.path.dirname(__file__), '..', '..', '..'))
 
 
 def IsRunningOnCrosDevice():
   """Returns True if we're on a ChromeOS device."""
   lsb_release = '/etc/lsb-release'
@@ skipping 58 matching lines @@
     if 'timeout' in kwargs:
       timeout = kwargs['timeout']
     else:
       timeout = default_timeout
     try:
       return timeout_retry.Run(func, timeout, 0, args=args)
     except reraiser_thread.TimeoutError:
       print '%s timed out.' % func.__name__
       return False
   return RunWithTimeout
+
+
+MIN_POLL_INTERVAL_IN_SECONDS = 0.1
+MAX_POLL_INTERVAL_IN_SECONDS = 5
+OUTPUT_INTERVAL_IN_SECONDS = 300
+
+def WaitFor(condition, timeout):
+  """Waits for up to |timeout| secs for the function |condition| to return True.
+
+  Polling frequency is (elapsed_time / 10), with a min of .1s and max of 5s.
+
+  Returns:
+    Result of |condition| function (if present).
+  """
+  def GetConditionString():
+    if condition.__name__ == '<lambda>':
+      try:
+        return inspect.getsource(condition).strip()
+      except IOError:
+        pass
+    return condition.__name__
+
+  start_time = time.time()
+  last_output_time = start_time
+  elapsed_time = time.time() - start_time
+  while elapsed_time < timeout:
+    res = condition()
+    if res:
+      return res
+    now = time.time()
+    elapsed_time = now - start_time
+    last_output_elapsed_time = now - last_output_time
+    if last_output_elapsed_time > OUTPUT_INTERVAL_IN_SECONDS:
+      logging.info('Continuing to wait %ds for %s. Elapsed: %ds.', timeout,
+                   GetConditionString(), elapsed_time)

[nednguyen, 2016/10/26 18:59:40]

pings about remove this log

+      last_output_time = time.time()
+    poll_interval = min(max(elapsed_time / 10., MIN_POLL_INTERVAL_IN_SECONDS),
+                        MAX_POLL_INTERVAL_IN_SECONDS)
+    time.sleep(poll_interval)
+  raise TimeoutException('Timed out while waiting %ds for %s.' %
+                         (timeout, GetConditionString()))
+
+class TimeoutException(Exception):
+  """The operation failed to complete because of a timeout.
+
+  It is possible that waiting for a longer period of time would result in a
+  successful operation.
+  """
+  pass