[Predator] Run predator.

appengine/findit/util_scripts/script_util.py

 # Copyright 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.
 
 """This module contains util functions that local scripts can use."""
 
-import logging
+import atexit
+import functools
 import os
+import Queue
 import subprocess
 import sys
+import threading
+import time
+import traceback
 
-from lib.cache_decorator import Cached
-from local_cache import LocalCacher  # pylint: disable=W
+MAX_THREAD_NUMBER = 15
+TASK_QUEUE = None
 
 
 def SetUpSystemPaths():  # pragma: no cover
   """Sets system paths so as to import modules in findit, third_party and
   appengine."""
   findit_root_dir = os.path.join(os.path.dirname(__file__), os.path.pardir)
+  first_party_dir = os.path.join(findit_root_dir, 'first_party')
   third_party_dir = os.path.join(findit_root_dir, 'third_party')
   appengine_sdk_dir = os.path.join(findit_root_dir, os.path.pardir,
                                    os.path.pardir, os.path.pardir,
                                    'google_appengine')
 
   # Add App Engine SDK dir to sys.path.
+  sys.path.insert(1, third_party_dir)
+  sys.path.insert(1, first_party_dir)
   sys.path.insert(1, appengine_sdk_dir)
-  sys.path.insert(1, third_party_dir)
   import dev_appserver
   dev_appserver.fix_sys_path()
 
   # Add Findit root dir to sys.path so that modules in Findit is available.
   sys.path.insert(1, findit_root_dir)
 
 
+SetUpSystemPaths()
+
+# The lib is in predator/ root dir, and can be imported only when sys.path gets
+# set up.
+from lib.cache_decorator import Cached
+from local_cache import LocalCacher  # pylint: disable=W
+
+
+def SignalWorkerThreads():  # pragma: no cover
+  """Puts signal worker threads into task queue."""
+  global TASK_QUEUE  # pylint: disable=W0602
+  if not TASK_QUEUE:
+    return
+
+  for _ in range(MAX_THREAD_NUMBER):
+    TASK_QUEUE.put(None)
+
+  # Give worker threads a chance to exit.
+  # Workaround the harmless bug in python 2.7 below.
+  time.sleep(1)
+
+
+atexit.register(SignalWorkerThreads)
+
+
+def Worker():  # pragma: no cover
+  global TASK_QUEUE  # pylint: disable=W0602
+  while True:
+    try:
+      task = TASK_QUEUE.get()
+      if not task:
+        return
+    except TypeError:
+      # According to http://bugs.python.org/issue14623, this is a harmless bug
+      # in python 2.7 which won't be fixed.
+      # The exception is raised on daemon threads when python interpreter is
+      # shutting down.
+      return
+
+    function, args, kwargs, result_semaphore = task
+    try:
+      function(*args, **kwargs)
+    except Exception:
+      print 'Caught exception in thread.'
+      print traceback.format_exc()
+      # Continue to process tasks in queue, in case every thread fails, the
+      # main thread will be waiting forever.
+      continue
+    finally:
+      # Signal one task is done in case of exception.
+      result_semaphore.release()
+
+
+def RunTasks(tasks):  # pragma: no cover
+  """Run given tasks. Not thread-safe: no concurrent calls of this function.
+
+  Return after all tasks were completed. A task is a dict as below:
+    {
+      'function': the function to call,
+      'args': the positional argument to pass to the function,
+      'kwargs': the key-value arguments to pass to the function,
+    }
+  """
+  if not tasks:
+    return
+
+  global TASK_QUEUE
+  if not TASK_QUEUE:
+    TASK_QUEUE = Queue.Queue()
+    for index in range(MAX_THREAD_NUMBER):
+      thread = threading.Thread(target=Worker, name='worker_%s' % index)
+      # Set as daemon, so no join is needed.
+      thread.daemon = True
+      thread.start()
+
+  result_semaphore = threading.Semaphore(0)
+  # Push task to task queue for execution.
+  for task in tasks:
+    TASK_QUEUE.put((task['function'], task.get('args', []),
+                    task.get('kwargs', {}), result_semaphore))
+
+  # Wait until all tasks to be executed.
+  for _ in tasks:
+    result_semaphore.acquire()
+
+
 @Cached(namespace='Command-output', cacher=LocalCacher())
 def GetCommandOutput(command):  # pragma: no cover
   """Gets the output stream of executable command.
 
   Args:
     command (str): Command to execute to get output.
 
   Return:
     Output steam of the command.
   """
   p = subprocess.Popen(
       command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
   stdoutdata, stderrdata = p.communicate()
 
   if p.returncode != 0:
-    logging.error('Error running command %s: %s', command, stderrdata)
-    return None
+    raise Exception('Error running command %s: %s' % (command, stderrdata))
 
   return stdoutdata
+
+
+def GetLockedMethod(cls, method_name, lock):  # pragma: no cover
+  """Returns a class/object method serialized with lock."""
+  method = getattr(cls, method_name)
+
+  def LockedMethod(cls, *args, **kwargs):  # pylint: disable=W
+    with lock:
+      return method(*args, **kwargs)
+
+  return functools.partial(LockedMethod, cls)