/usr/share/pyshared/arcom/threadpool.py is in nordugrid-arc-python 1.1.1-1.
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from time import sleep
# Slightly modified from http://code.activestate.com/recipes/203871/
class ThreadPool:
"""Flexible thread pool class. Creates a pool of threads, then
accepts tasks that will be dispatched to the next available
thread."""
def __init__(self, numThreads):
"""Initialize the thread pool with numThreads workers."""
self.__threads = []
self.__resizeLock = threading.Condition(threading.Lock())
self.__taskLock = threading.Condition(threading.Lock())
self.__tasks = []
self.__isJoining = False
self.setThreadCount(numThreads)
def setThreadCount(self, newNumThreads):
""" External method to set the current pool size. Acquires
the resizing lock, then calls the internal version to do real
work."""
# Can't change the thread count if we're shutting down the pool!
if self.__isJoining:
return False
self.__resizeLock.acquire()
try:
self.__setThreadCountNolock(newNumThreads)
finally:
self.__resizeLock.release()
return True
def __setThreadCountNolock(self, newNumThreads):
"""Set the current pool size, spawning or terminating threads
if necessary. Internal use only; assumes the resizing lock is
held."""
# If we need to grow the pool, do so
while newNumThreads > len(self.__threads):
newThread = ThreadPoolThread(self)
self.__threads.append(newThread)
newThread.start()
# If we need to shrink the pool, do so
while newNumThreads < len(self.__threads):
self.__threads[0].goAway()
del self.__threads[0]
def getThreadCount(self):
"""Return the number of threads in the pool."""
self.__resizeLock.acquire()
try:
return len(self.__threads)
finally:
self.__resizeLock.release()
def queueTask(self, task, args=None, taskCallback=None):
"""Insert a task into the queue. task must be callable;
args and taskCallback can be None."""
if self.__isJoining == True:
return False
if not callable(task):
return False
self.__taskLock.acquire()
try:
self.__tasks.append((task, args, taskCallback))
return True
finally:
self.__taskLock.release()
def getNextTask(self):
""" Retrieve the next task from the task queue. For use
only by ThreadPoolThread objects contained in the pool."""
self.__taskLock.acquire()
try:
if self.__tasks == []:
return (None, None, None)
else:
return self.__tasks.pop(0)
finally:
self.__taskLock.release()
def joinAll(self, waitForTasks = True, waitForThreads = True):
""" Clear the task queue and terminate all pooled threads,
optionally allowing the tasks and threads to finish."""
# Mark the pool as joining to prevent any more task queueing
self.__isJoining = True
# Wait for tasks to finish
if waitForTasks:
while self.__tasks != []:
sleep(0.1)
# Tell all the threads to quit
self.__resizeLock.acquire()
try:
# Wait until all threads have exited
if waitForThreads:
for t in self.__threads:
t.goAway()
for t in self.__threads:
t.join()
# print t,"joined"
del t
self.__setThreadCountNolock(0)
self.__isJoining = True
# Reset the pool for potential reuse
self.__isJoining = False
finally:
self.__resizeLock.release()
class ThreadPoolThread(threading.Thread):
""" Pooled thread class. """
threadSleepTime = 0.1
def __init__(self, pool):
""" Initialize the thread and remember the pool. """
threading.Thread.__init__(self)
self.__pool = pool
self.__isDying = False
def run(self):
""" Until told to quit, retrieve the next task and execute
it, calling the callback if any. """
while self.__isDying == False:
cmd, args, callback = self.__pool.getNextTask()
# If there's nothing to do, just sleep a bit
if cmd is None:
sleep(ThreadPoolThread.threadSleepTime)
elif callback is None:
if args is None:
cmd()
elif isinstance(args,list):
cmd(*args)
else:
cmd(args)
else:
if args is None:
callback(cmd())
elif isinstance(args,list):
callback(cmd(*args))
else:
callback(cmd(args))
def goAway(self):
""" Exit the run loop next time through."""
self.__isDying = True
# from http://my.safaribooksonline.com/0596001673/pythoncook-CHP-6-SECT-4
class ReadWriteLock:
""" A lock object that allows many simultaneous "read locks", but
only one "write lock." """
def __init__(self):
self._read_ready = threading.Condition(threading.Lock())
self._readers = 0
def acquire_read(self):
""" Acquire a read lock. Blocks only if a thread has
acquired the write lock. """
self._read_ready.acquire()
try:
self._readers += 1
finally:
self._read_ready.release()
def release_read(self):
""" Release a read lock. """
self._read_ready.acquire()
try:
self._readers -= 1
if not self._readers:
self._read_ready.notifyAll()
finally:
self._read_ready.release()
def acquire_write(self):
""" Acquire a write lock. Blocks until there are no
acquired read or write locks. """
self._read_ready.acquire()
while self._readers > 0:
self._read_ready.wait()
def release_write(self):
""" Release a write lock. """
self._read_ready.release()
COUNTER = 0
# Usage example
if __name__ == "__main__":
from random import randrange
# Sample task 1: given a start and end value, shuffle integers,
# then sort them
def sortTask(data):
print "SortTask starting for ", data
numbers = range(data[0], data[1])
for a in numbers:
rnd = randrange(0, len(numbers) - 1)
a, numbers[rnd] = numbers[rnd], a
print "SortTask sorting for ", data
numbers.sort()
print "SortTask done for ", data
return "Sorter ", data
# Sample task 2: just sleep for a number of seconds.
def waitTask(data):
print "WaitTask starting for ", data
print "WaitTask sleeping for %d seconds" % data
sleep(data)
return "Waiter", data
locker = ReadWriteLock()
def addTask(data):
global COUNTER
nadds = 10000
for i in range(nadds):
# re-acquiring lock for every add
# don't do this at home...
locker.acquire_write()
COUNTER += data
locker.release_write()
print "Added %d to counter, counter is now %d"%(data*nadds,COUNTER)
return "addTask", data
# Both tasks use the same callback
def taskCallback(data):
print "Callback called for", data
# Create a pool with three worker threads
pool = ThreadPool(3)
# Insert tasks into the queue and let them run
pool.queueTask(sortTask, (1000, 100000), taskCallback)
pool.queueTask(waitTask, 5, taskCallback)
pool.queueTask(sortTask, (200, 200000), taskCallback)
pool.queueTask(waitTask, 2, taskCallback)
pool.queueTask(sortTask, (3, 30000), taskCallback)
pool.queueTask(waitTask, 7, taskCallback)
pool.joinAll()
pool = ThreadPool(5)
pool.queueTask(addTask, 10, taskCallback)
pool.queueTask(addTask, 10, taskCallback)
pool.queueTask(addTask, 10, taskCallback)
pool.queueTask(addTask, 10, taskCallback)
print "before join", COUNTER
# When all tasks are finished, allow the threads to terminate
pool.joinAll()
print "after join", COUNTER
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