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