id summary reporter owner description type status component version severity resolution keywords cc stage has_patch needs_docs needs_tests needs_better_patch easy ui_ux 33092 Add note regarding thread-safety when using PyMemcacheCache. Martijn van der Blom nobody "For thread-safety when using `pymemcache` the option `'use_pooling': True` can be passed via `OPTIONS` which will make `pymemcache.HashClient` use `pymemcache.PooledClient` instead of `pymemcache.Client` internally. Some documentation should be added or improved. ---- In our application we were using the MemcachedCache backend to connect to a memcached server. Since this backend will be removed in Django 4.1 we thought we'd migrate to the alternative PyMemcacheCache backend as suggested in the Django documentation at: https://docs.djangoproject.com/en/3.2/topics/cache/ After upgrading we encountered several errors when running the application in gunicorn with the gevent worker class. Summary of errors: - gevent._socketcommon.cancel_wait_ex: [Errno 9] File descriptor was closed in another greenlet - gevent.exceptions.ConcurrentObjectUseError: This socket is already used by another greenlet: > - OSError: [Errno 9] Bad file descriptor These errors seem to be related to either the Django backend implementation or Pymemcache not handling multi-threading/thread-safety properly. There is a related bug for the Pymemcache library where a member of that team states that is up the application using Pymemcache to handle thread-safety (https://github.com/pinterest/pymemcache/issues/195#issuecomment-452523524). In this case the Django framework. This comment in Django's BaseMemcachedCache implementation indicates that that was the original intent: https://github.com/django/django/blob/main/django/core/cache/backends/memcached.py#L38 so i think PyMemcacheCache should handle this. Example project that reproduces the error: https://github.com/mvanderblom/django-memcached-bugreport For us, this error prevents us from using the PyMemcacheCache backend and thus from upgrading to Django 4.1 when it gets released." Cleanup/optimization new Core (Cache system) 3.2 Normal Andrew Godwin Nick Pope Accepted 0 0 0 0 0 0