[Findit] Use a thread pool.

tools/findit/crash_utils.py

 # Copyright (c) 2014 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 cgi
 import ConfigParser
 import json
 import os
+import Queue
+import threading
 import time
 
 from common import utils
 from result import Result
 
 
 INFINITY = float('inf')
 
+MAX_THREAD_NUMBER = 10

[stgao, 2014/08/29 22:48:49]

How many threads do you guys prefer?

+TASK_QUEUE = None
+
+
+def Worker():
+  global TASK_QUEUE
+  while True:
+    function, args, kwargs, result_semaphore = TASK_QUEUE.get()
+    try:
+      function(*args, **kwargs)
+    except:
+      pass
+    finally:
+      # Signal one task is done in case of exception.
+      result_semaphore.release()
+
+
+def RunTasks(tasks):
+  """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()
+
 
 def GetRepositoryType(revision_number):
   """Returns the repository type of this revision number.
 
   Args:
     revision_number: A revision number or git hash.
 
   Returns:
     'git' or 'svn', depending on the revision_number.
   """
@@ skipping 475 matching lines @@
     review_url = None
     reviewers = None
     line_content = blame.line_content
     message = blame.message
 
     result = Result(suspected_cl, revision_url, component_name, author, reason,
                     review_url, reviewers, line_content, message)
     result_list.append(result)
 
   return result_list