Function _process_worker

Lib/concurrent/futures/process.py:218–269

Evaluates calls from call_queue and places the results in result_queue. This worker is run in a separate process. Args: call_queue: A ctx.Queue of _CallItems that will be read and evaluated by the worker. result_queue: A ctx.Queue of _ResultItems that will writt

(call_queue, result_queue, initializer, initargs, max_tasks=None)

def _process_worker(call_queue, result_queue, initializer, initargs, max_tasks=None):
    """Evaluates calls from call_queue and places the results in result_queue.

    This worker is run in a separate process.

    Args:
        call_queue: A ctx.Queue of _CallItems that will be read and
            evaluated by the worker.
        result_queue: A ctx.Queue of _ResultItems that will written
            to by the worker.
        initializer: A callable initializer, or None
        initargs: A tuple of args for the initializer
    """
    if initializer is not None:
        try:
            initializer(*initargs)
        except BaseException:
            _base.LOGGER.critical('Exception in initializer:', exc_info=True)
            # The parent will notice that the process stopped and
            # mark the pool broken
            return
    num_tasks = 0
    exit_pid = None
    while True:
        call_item = call_queue.get(block=True)
        if call_item is None:
            # Wake up queue management thread
            result_queue.put(os.getpid())
            return

        if max_tasks is not None:
            num_tasks += 1
            if num_tasks >= max_tasks:
                exit_pid = os.getpid()

        try:
            r = call_item.fn(*call_item.args, **call_item.kwargs)
        except BaseException as e:
            exc = _ExceptionWithTraceback(e, e.__traceback__)
            _sendback_result(result_queue, call_item.work_id, exception=exc,
                             exit_pid=exit_pid)
        else:
            _sendback_result(result_queue, call_item.work_id, result=r,
                             exit_pid=exit_pid)
            del r

        # Liberate the resource as soon as possible, to avoid holding onto
        # open files or shared memory that is not needed anymore
        del call_item

        if exit_pid is not None:
            return


class _ExecutorManagerThread(threading.Thread):