手把手教你寫一個自己的 master-slave 架構的 TCP 伺服器

nginx、uvicorn、gunicorn 這些 HTTP sever 都是 master-slave 架構

你好奇他們是怎麼實現的嗎？

如果你是也是一個好奇寶寶，就接著往下看吧

多程式

使用 multiprocessing.Pool 的實現

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
    )

    # 獲取本地主機名
    host = socket.gethostname()

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

    port = 6001

    # 繫結埠號
    serversocket.bind(('0.0.0.0', port))

    # 設定最大連線數，超過後排隊
    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'傳送了響應')
        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()

使用 ProcessPoolExecutor 的實現

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

default_encoding: str = 'utf-8'


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

    # 獲取本地主機名
    host = socket.gethostname()

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

    port = 6001

    # 繫結埠號
    serversocket.bind(('0.0.0.0', port))

    # 設定最大連線數，超過後排隊
    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'傳送了響應')
        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,
    #     mp_context=multiprocessing.get_context('spawn')
    # )

    pool = ProcessPoolExecutor(
        max_workers=multiprocessing.cpu_count(),
        mp_context=multiprocessing.get_context('spawn')
    )

    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.submit(start_request,clientsocket, addr)

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

    pool.close()
    pool.join()

上訴兩種實現的潛在問題

問題一：無法完美執行在 mac 平臺

上面兩種方式在 Linux 上都可以工作的良好，但是在 mac 上卻不行

服務端會有很大機率報錯（客戶端請求的時候，隨機出現報錯）：

ConnectionRefusedError: [Errno 61] Connection refused
concurrent.futures.process.BrokenProcessPool: A child process terminated abruptly, the process pool is not usable anymore

問題二：master 負載太高，容易成為瓶頸，無法實現橫向擴充套件

master 程式都乾冒煙了，slave 都閒著

圖片.png

為什麼呢？因為 slave 乾的事情太少了，而 master 程式負責了 serversocket.accept 等等操作，壓力山大