@H_404_1@我正在使用来自RabbitMQ频道的消息,我希望我一次可以消耗n个元素.我想我可以使用ProcessPoolExecutor(或ThreadPoolExecutor).
我只是想知道是否可以知道池中是否有免费执行程序.

@H_404_1@这就是我想写的：

@H_404_1@

executor = futures.ProcessPoolExecutor(max_workers=5)
running = []
def consume(message):
    print "actually consuming a single message"

def on_message(channel,method_frame,header_frame,message):
    # this method is called once per incoming message
    future = executor.submit(consume,message)
    block_until_a_free_worker(executor,future)

def block_until_a_free_worker(executor,future):
    running.append(future) # this grows forever!
    futures.wait(running,timeout=5,return_when=futures.FIRST_COMPLETED)

[...]
channel.basic_consume(on_message,'my_queue')
channel.start_consuming()

@H_404_1@我需要编写函数block_until_a_free_worker.
此方法应该能够检查是否所有正在运行的工作程序都在使用中.

@H_404_1@在替代方案中,我可以使用任何阻塞executor.submit选项(如果可用).

@H_404_1@我尝试了一种不同的方法,并在完成后改变期货清单.
我试图从列表中明确添加和删除期货,然后像这样等待：

@H_404_1@

futures.wait(running,return_when=futures.FIRST_COMPLETED)

@H_404_1@这似乎不是解决方案.

@H_404_1@我可以设置future.add_done_callback,并可能计算正在运行的实例…

@H_404_1@任何提示或想法？
谢谢.

from threading import Semaphore
from concurrent.futures import ProcessPoolExecutor 

class TaskManager:
    def __init__(self,workers):
        self.pool = ProcessPoolExecutor(max_workers=workers)
        self.workers = Semaphore(workers)

    def new_task(self,function):
        """Start a new task,blocks if all workers are busy."""
        self.workers.acquire()  # flag a worker as busy

        future = self.pool.submit(function,... )

        future.add_task_done(self.task_done)

    def task_done(self,future):
        """Called once task is done,releases one worker."""
        self.workers.release()