[英]ZeroTurnaround Process Executor (zt-exec) processes waiting for input on infinite loop, how?
[英]How to shutdown process with event loop and executor
考虑以下程序。
import asyncio
import multiprocessing
from multiprocessing import Queue
from concurrent.futures.thread import ThreadPoolExecutor
import sys
def main():
executor = ThreadPoolExecutor()
loop = asyncio.get_event_loop()
# comment the following line and the shutdown will work smoothly
asyncio.ensure_future(print_some(executor))
try:
loop.run_forever()
except KeyboardInterrupt:
print("shutting down")
executor.shutdown()
loop.stop()
loop.close()
sys.exit()
async def print_some(executor):
print("Waiting...Hit CTRL+C to abort")
queue = Queue()
loop = asyncio.get_event_loop()
some = await loop.run_in_executor(executor, queue.get)
print(some)
if __name__ == '__main__':
main()
当我点击“CTRL + C”时,我想要的只是一个优雅的关机。 但是,执行程序线程似乎阻止了(即使我调用shutdown
)
您需要发送一个毒丸,让工作人员停止侦听queue.get调用。 ThreadPoolExecutor
池中的工作线程将阻止Python退出,如果它们有活动的工作。 源代码中有一条注释描述了此行为的原因:
# Workers are created as daemon threads. This is done to allow the interpreter
# to exit when there are still idle threads in a ThreadPoolExecutor's thread
# pool (i.e. shutdown() was not called). However, allowing workers to die with
# the interpreter has two undesirable properties:
# - The workers would still be running during interpreter shutdown,
# meaning that they would fail in unpredictable ways.
# - The workers could be killed while evaluating a work item, which could
# be bad if the callable being evaluated has external side-effects e.g.
# writing to a file.
#
# To work around this problem, an exit handler is installed which tells the
# workers to exit when their work queues are empty and then waits until the
# threads finish.
这是一个干净利落的完整示例:
import asyncio
import multiprocessing
from multiprocessing import Queue
from concurrent.futures.thread import ThreadPoolExecutor
import sys
def main():
executor = ThreadPoolExecutor()
loop = asyncio.get_event_loop()
# comment the following line and the shutdown will work smoothly
fut = asyncio.ensure_future(print_some(executor))
try:
loop.run_forever()
except KeyboardInterrupt:
print("shutting down")
queue.put(None) # Poison pill
loop.run_until_complete(fut)
executor.shutdown()
loop.stop()
loop.close()
async def print_some(executor):
print("Waiting...Hit CTRL+C to abort")
loop = asyncio.get_event_loop()
some = await loop.run_in_executor(executor, queue.get)
print(some)
queue = None
if __name__ == '__main__':
queue = Queue()
main()
需要run_until_complete(fut)
调用以避免在asyncio eventloop退出时发出挂起待处理任务的警告。 如果你不关心这个,你可以把这个电话留下来。
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