Gunicorn多Worker环境下DRF集成python-socketio仅单连接问题排查

我在Django REST Framework（DRF）中使用python-socketio客户端，DRF通过Gunicorn在CentOS服务器上以3个Worker运行。启动服务后仅能看到一个Socket连接，导致聊天服务无法正常使用。请问如何在DRF中确保Socket客户端连接正常维护？

相关代码 #

settings.py #

from socket_utils import SocketClientClass

sio = SocketClientClass()
sio.connect_to_server()

socket_utils.py #

import os
import time
import socketio

class SocketClientClass:
    def __init__(self):
        self.sio = socketio.Client()
        self.socket_url = os.environ.get("SOCKET_URL")

    def connect_to_server(self):
        socket_connect_cnt = 0

        while not self.sio.connected:
            socket_connect_cnt += 1
            try:
                self.sio.connect(self.socket_url)
                time.sleep(0.05)
                logger.info(f"[socket_client] connect success!")
            except Exception as ex:
                logger.error(f"[socket_client] connect exception : {str(ex)}")
            if socket_connect_cnt > 1:
                break

    def disconnect_to_server(self):
        if self.sio.connected:
            try:
                self.sio.disconnect()
                time.sleep(0.05)
                logger.info(f"[socket_client] disconnect success!")
            except Exception as ex:
                logger.error(f"[socket_client] disconnect exception : {str(ex)}")

    def message(self, event, data):
        try:
            if self.sio.connected:
                self.sio.emit(event, data)
                logger.info(f"[socket_client] send message success! : {data}")
            else:
                self.connect_to_server()
                logger.error(f"[socket_client] not connected to server!")
        except Exception as ex:
            if self.sio.connected:
                self.disconnect_to_server()
            self.connect_to_server()
            logger.error(f"[socket_client] send message exception : {str(ex)}")

服务器日志 #

1) Gunicorn服务日志 #

● gunicorn.service - gunicorn daemon
   Loaded: loaded (/etc/systemd/system/gunicorn.service; enabled; vendor preset: disabled)
   Active: active (running) since Tue 2024-06-18 09:37:14 KST; 6min ago
 Main PID: 1269661 (python3.11)
    Tasks: 7 (limit: 23684)
   Memory: 260.6M
   CGroup: /system.slice/gunicorn.service
           ├─1269661 /home/dev/anaconda3/envs/snappy/bin/python3.11 -m gunicorn --preload --workers>
           ├─1269666 /home/dev/anaconda3/envs/snappy/bin/python3.11 -m gunicorn --preload --workers>
           ├─1269667 /home/dev/anaconda3/envs/snappy/bin/python3.11 -m gunicorn --preload --workers>
           └─1269668 /home/dev/anaconda3/envs/snappy/bin/python3.11 -m gunicorn --preload --workers>

2) Socket服务器日志 #

...
[2024-06-18 09:37:14,061][INFO][pid:1269257] [disconnect] sid: ddOuhjZZM1bOeSUBAAAT
[2024-06-18 09:37:14,065][INFO][pid:1269257] [disconnect] sid: IyrGaoh0s7zxJ-ICAAAV
[2024-06-18 09:37:14,927][INFO][pid:1269257] [connect] sid: Jojy3GmCCCWYAppkAAAX, remote: localhost:5002

3) Socket客户端日志 #

...
[2024-06-18 09:37:15,019][INFO][pid:1269661] [socket_client] connect success!

问题原因与解决方法 #

核心原因 #

你使用了Gunicorn的--preload参数，该参数会在fork Worker进程前预加载整个应用。settings.py中的sio.connect_to_server()在预加载阶段仅由主进程执行并建立Socket连接，而fork出的Worker进程会继承这个连接，但Socket连接是进程绑定的，Worker进程无法复用主进程的连接，最终只有主进程的连接有效，导致日志中仅显示一个连接。

解决步骤 #

1. 移除Gunicorn的--preload参数
   修改Gunicorn启动命令，去掉--preload，让每个Worker进程独立加载应用并建立Socket连接：

   gunicorn --workers 3 your_project.wsgi:application
   

2. 延迟Socket连接初始化
   不在settings.py中直接初始化连接，而是通过Django的AppConfig在Worker进程启动后再建立连接：

   • 创建/修改应用的apps.py：

     from django.apps import AppConfig
     from socket_utils import SocketClientClass
     import os
     
     class YourAppConfig(AppConfig):
         default_auto_field = 'django.db.models.BigAutoField'
         name = 'your_app_name'
     
         def ready(self):
             # 仅在Worker进程中执行，避免主进程重复初始化
             if os.environ.get('RUN_MAIN') == 'true':
                 global sio
                 sio = SocketClientClass()
                 sio.connect_to_server()
     

   • 在settings.py的INSTALLED_APPS中替换为自定义的AppConfig：

     INSTALLED_APPS = [
         # ...其他应用
         'your_app_name.apps.YourAppConfig',
     ]
     

3. 优化Socket连接维护逻辑

   • 增加连接重试次数与间隔：

     def connect_to_server(self):
         socket_connect_cnt = 0
         max_retry = 3
         while not self.sio.connected and socket_connect_cnt < max_retry:
             socket_connect_cnt += 1
             try:
                 self.sio.connect(self.socket_url)
                 time.sleep(0.05)
                 logger.info(f"[socket_client] connect success! (attempt {socket_connect_cnt})")
             except Exception as ex:
                 logger.error(f"[socket_client] connect exception (attempt {socket_connect_cnt}) : {str(ex)}")
                 time.sleep(1)
     

   • 添加心跳与断开重连监听：

     def __init__(self):
         self.sio = socketio.Client()
         self.socket_url = os.environ.get("SOCKET_URL")
     
         @self.sio.on('connect')
         def on_connect():
             logger.info("[socket_client] connected to server")
     
         @self.sio.on('disconnect')
         def on_disconnect():
             logger.warning("[socket_client] disconnected from server, reconnecting...")
             self.connect_to_server()
     

4. 验证连接状态
   修改配置后重启Gunicorn，查看Socket服务器日志，应该会看到3个新的连接（对应3个Worker进程），此时每个Worker都能独立处理Socket消息，聊天服务即可正常运行。

内容的提问来源于stack exchange，提问作者Hyeonwoo Park