Added gsutil/gslib to depot_tools/third_party

third_party/gsutil/gslib/thread_pool.py

Index: third_party/gsutil/gslib/thread_pool.py
diff --git a/third_party/gsutil/gslib/thread_pool.py b/third_party/gsutil/gslib/thread_pool.py
new file mode 100644
index 0000000000000000000000000000000000000000..b9fcfd4e705c0a1a3877f9be427d739e81e94947
--- /dev/null
+++ b/third_party/gsutil/gslib/thread_pool.py
@@ -0,0 +1,79 @@
+# Copyright 2011 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Basic thread pool with exception handler."""
+
+import logging
+import Queue
+import threading
+
+
+# Magic values used to cleanly bring down threads.
+_THREAD_EXIT_MAGIC = ('Clean', 'Thread', 'Exit')
+
+
+def _DefaultExceptionHandler(e):
+  logging.exception(e)
+
+
+class Worker(threading.Thread):
+  """Thread executing tasks from a given task's queue."""
+
+  def __init__(self, tasks, exception_handler):
+    threading.Thread.__init__(self)
+    self.tasks = tasks
+    self.daemon = True
+    self.exception_handler = exception_handler
+    self.start()
+
+  def run(self):
+    while True:
+      func, args, kargs = self.tasks.get()
+
+      # Listen for magic value indicating thread exit.
+      if (func, args, kargs) == _THREAD_EXIT_MAGIC:
+        break
+
+      try:
+        func(*args, **kargs)
+      except Exception, e:
+        self.exception_handler(e)
+      finally:
+        self.tasks.task_done()
+
+
+class ThreadPool(object):
+  """Pool of threads consuming tasks from a queue."""
+
+  def __init__(self, num_threads, exception_handler=_DefaultExceptionHandler):
+    self.tasks = Queue.Queue(num_threads)
+    self.threads = []
+    for _ in range(num_threads):
+      self.threads.append(Worker(self.tasks, exception_handler))
+
+  def AddTask(self, func, *args, **kargs):
+    """Add a task to the queue."""
+    self.tasks.put((func, args, kargs))
+
+  def WaitCompletion(self):
+    """Wait for completion of all the tasks in the queue."""
+    self.tasks.join()
+
+  def Shutdown(self):
+    """Shutdown the thread pool."""
+    for thread in self.threads:
+      self.tasks.put(_THREAD_EXIT_MAGIC)
+
+    for thread in self.threads:
+      thread.join()