[英]Gevent: how to wait for set of greenlets finished
我有几个任务生产者之间共享的gevent.pool(大小固定)。 如果有空闲插槽,每个任务生产者都可以将新的greenlet应用于池。 在将任务添加到池中之后,任务生产者应等待所有添加的任务完成。
我尝试使用gevent.queue.JoinableQueue等待所有任务完成。 它工作正常,除了在等待结束时出现一个非常烦人的异常。
如何解决以下代码以避免这种情况? 也许我做错了什么?
from gevent import monkey, sleep; monkey.patch_all()
from gevent.queue import JoinableQueue
from gevent.pool import Pool
pool = Pool(3)
def worker(n):
print 'Worker {} started'.format(n)
sleep(1)
print 'Worker {} finished'.format(n)
return n
def main():
results = []
queue = JoinableQueue()
for job_no in range(5):
pool.wait_available()
greenlet = pool.apply_async(worker, kwds=dict(n=job_no), callback=lambda ret: results.append(ret))
queue.put(greenlet)
sleep(.05)
print 'All workers added'
queue.join()
print 'All workers finished', results
if __name__ == '__main__':
main()
输出:
Worker 0 started
Worker 1 started
Worker 2 started
Worker 0 finished
Worker 3 started
Worker 1 finished
Worker 4 started
All workers added
Worker 2 finished
Worker 3 finished
Worker 4 finished
Traceback (most recent call last):
File "main.py", line 32, in <module>
main()
File "main.py", line 27, in main
queue.join()
File "C:\Python\2.7.10\x64\lib\site-packages\gevent\queue.py", line 492, in join
return self._cond.wait(timeout=timeout)
File "C:\Python\2.7.10\x64\lib\site-packages\gevent\event.py", line 219, in wait
return self._wait(timeout)
File "C:\Python\2.7.10\x64\lib\site-packages\gevent\event.py", line 129, in _wait
gotit = self._wait_core(timeout)
File "C:\Python\2.7.10\x64\lib\site-packages\gevent\event.py", line 106, in _wait_core
result = self.hub.switch()
File "C:\Python\2.7.10\x64\lib\site-packages\gevent\hub.py", line 630, in switch
return RawGreenlet.switch(self)
gevent.hub.LoopExit: ('This operation would block forever', <Hub at 0x26c1c28 select default pending=0 ref=0>)
您会收到“此操作将永远阻止”错误,因为队列中没有绿帽消耗任务, queue.join()
仅阻塞直到所有绿帽都完成,然后引发异常。
这里不需要JoinableQueue
,请使用gevent.joinall()
等待所有greenlet完成:
import gevent
def main():
results = []
gs = []
for job_no in range(5):
greenlet = ..
gs.append(greenlet)
gevent.joinall(gs)
print 'All workers finished', results
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