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 PyMemcacheCache backend fails when running as a wsgi application with gevent worker class 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." Bug closed Core (Cache system) 3.2 Normal worksforme Andrew Godwin Nick Pope Accepted 0 0 0 0 0 0