为什么使用 python 的进程池处理并发的 TCP 请求，会导致客户端并发卡住？

Question

服务端代码：

import os
import socket
import sys
import time
import threading
from loguru import logger
from concurrent.futures import ThreadPoolExecutor
from concurrent.futures._base import Future
import multiprocessing

default_encoding: str = 'utf-8'

pool = ThreadPoolExecutor(
    max_workers=20,
    thread_name_prefix='simple-work-thread-pool'
)


def init_serversocket() -> socket.socket:
    serversocket = socket.socket(
        family=socket.AF_INET,
        type=socket.SOCK_STREAM
    )

    # 获取本地主机名
    host = socket.gethostname()

    logger.debug(f'host {host}')

    port = 6001

    # 绑定端口号
    serversocket.bind(('0.0.0.0', port))

    # 设置最大连接数，超过后排队
    serversocket.listen(2048)

    return serversocket


def send_response(clientsocket: socket.socket, addr: tuple, response_body: bytes) -> int:
    send_len: int = clientsocket.send(response_body)
    clientsocket.close()
    return send_len


def start_request(clientsocket: socket.socket, addr: tuple) -> int:
    try:
        pid = os.getpid()
        logger.debug(f'pid: {pid}, get message from {addr}')
        request_body: bytes = clientsocket.recv(2048)
        request_text: str = request_body.decode(encoding=default_encoding)

        response_text: str = f'server get message: {request_text}'

        response_body: bytes = response_text.encode(default_encoding)
        # time.sleep(1)
        send_len = send_response(
            clientsocket=clientsocket, addr=addr, response_body=response_body)
        logger.debug(f'发送了响应')
        return send_len
    except Exception as error:
        logger.exception(error)


def start_request_callback(future: Future) -> None:
    send_len: int = future.result()
    logger.debug(
        f'{threading.current_thread().name}, send payload len is {send_len}')


if __name__ == "__main__":
    serversocket = init_serversocket()

    pool = multiprocessing.Pool(processes=16)

    while True:
        clientsocket, addr = serversocket.accept()

        clientsocket: socket.socket
        addr: tuple

        # future: Future = pool.submit(start_request, clientsocket, addr)
        # future.add_done_callback(start_request_callback)

        pool.apply_async(start_request, (clientsocket, addr))

    pool.close()
    pool.join()

服务端使用进程池并发处理来自客户端的 TCP 请求

客户端代码：

from base64 import encode
import socket  # 客户端 发送一个数据，再接收一个数据
import json
from loguru import logger
from concurrent.futures import ThreadPoolExecutor


failture_requests = []


def send_request(index:int):
    try:
        # 声明socket类型，同时生成链接对象
        clientsocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        clientsocket.connect(('127.0.0.1', 6001))  # 建立一个链接，连接到本地的6969端口

        payload = b'ponponon'

        clientsocket.send(payload)

        data = clientsocket.recv(1024)

        payload = data.decode()
        logger.debug(index)

        clientsocket.close()
        logger.debug('请求完成')
    except Exception as error:
        failture_requests.append(index)
        logger.exception(error)


pool = ThreadPoolExecutor(max_workers=2)
for index in range(100):
    pool.submit(send_request,index)

pool.shutdown(wait=True)
logger.debug(failture_requests)
logger.debug(len(failture_requests))

因为我的客户端使用线程池并发，只要 max_workers 大于 1 就会一直卡死

测试平台是 macos 13.3.1 (22E261) + python3.10.10，会卡死
但是我在 ubuntu20.04 + python3.11.3 上就是一切正常，不会出现卡死的问题

但是 max_workers 是 1 就没有问题，我怀疑问题出在服务端，但是具体原因我分析不出来

服务端如果用线程池，就一切正常，服务端和客户端都正常。
但是我只想用多进程

Answer 1

import os
import socket
import sys
import time
import threading
from loguru import logger
from concurrent.futures import ThreadPoolExecutor
from concurrent.futures._base import Future
import multiprocessing

default_encoding: str = 'utf-8'

def init_serversocket() -> socket.socket:
    serversocket = socket.socket(
        family=socket.AF_INET,
        type=socket.SOCK_STREAM
    )

    # 获取本地主机名
    host = socket.gethostname()

    logger.debug(f'host {host}')

    port = 6001

    # 绑定端口号
    serversocket.bind(('0.0.0.0', port))

    # 设置最大连接数，超过后排队
    serversocket.listen(2048)

    return serversocket

def send_response(clientsocket: socket.socket, addr: tuple, response_body: bytes) -> int:
    send_len: int = clientsocket.send(response_body)
    clientsocket.close()
    return send_len

def start_request(clientsocket_fd: int, addr: tuple) -> int:
    clientsocket = socket.fromfd(clientsocket_fd, socket.AF_INET, socket.SOCK_STREAM)
    os.close(clientsocket_fd)

    try:
        pid = os.getpid()
        logger.debug(f'pid: {pid}, get message from {addr}')
        request_body: bytes = clientsocket.recv(2048)
        request_text: str = request_body.decode(encoding=default_encoding)

        response_text: str = f'server get message: {request_text}'

        response_body: bytes = response_text.encode(default_encoding)
        # time.sleep(1)
        send_len = send_response(
            clientsocket=clientsocket, addr=addr, response_body=response_body)
        logger.debug(f'发送了响应')
        return send_len
    except Exception as error:
        logger.exception(error)
    finally:
        clientsocket.close()

def worker_process(clientsocket_fd, addr):
    start_request(clientsocket_fd, addr)

if __name__ == "__main__":
    serversocket = init_serversocket()

    pool = multiprocessing.Pool(processes=16)

    while True:
        try:
            clientsocket, addr = serversocket.accept()

            clientsocket_fd = clientsocket.fileno()
            pool.apply_async(worker_process, (clientsocket_fd, addr))

        except Exception as error:
            logger.exception(error)

    pool.close()
    pool.join()