解决django.db.utils.OperationalError: (1213, 'Deadlock found when trying to get lock; try restarting transaction') 死锁问题

原因：因为设置了SESSION_SAVE_EVERY_REQUEST=Ture,导致每个接口没有修改的状态下也更改session的过期时间。

1. 查看代码发现SessionMiddleware源码,遇到UpdateError异常直接抛出。

   try:
       request.session.save()
   except UpdateError:
       raise SuspiciousOperation(
           "The request's session was deleted before the "
           "request completed. The user may have logged "
           "out in a concurrent request, for example."
       )
   

2. 创建一个新的中间件类，继承自SessionMiddleware

   import time
   from django.db import transaction
   from django.contrib.sessions.backends.base import UpdateError
   from django.contrib.sessions.middleware import SessionMiddleware
   
   
   class CustomSessionMiddleware(SessionMiddleware):
       # 继承SessionMiddleware 遇到异常重试3次
   
       def process_response(self, request, response):
           try:
               return super().process_response(request, response)
           except Exception as e:
               print('errors: {}'.format(e))
               max_retries = 3
               retries = 0
               success = False
               while retries < max_retries and not success:
                   try:
                       with transaction.atomic():
                           request.session.save()
                       success = True
                   except UpdateError:
                       print('试图获得锁时发现死锁;尝试重新启动事务!')
                       retries += 1
                       time.sleep(1)
   
               if not success:
                   # 处理超过最大重试次数的情况
                   if request.method == "POST":
                       print(request.body, '================>')
                   else:
                       print(request.GET, '================>')
                   print('OperationalError 异常已经重试最大次数')
           return response
   
   

3. 在Django的配置文件（settings.py）中将默认的SessionMiddleware替换为自定义的中间件。

   MIDDLEWARE = [
       # 'django.contrib.sessions.middleware.SessionMiddleware',
       # 重写SessionMiddleware
       'middleware.session.CustomSessionMiddleware',
   ]