Comment 11 for bug 1883659

I think this is caused by usage of obsolete code which was used in keystonemiddleware long time ago - before oslo.cache support was added to keystonemiddleware as new library (in past time :)).

Services which are using keystonemiddleware should use memcache_use_advanced_pool = True (oslo.cache memcached_pool implementation) instead of obsolete code.

Or better said option memcache_use_advanced_pool should be removed and keystonemiddleware should use oslo.cache implementation by default.

Oslo.cache introducing and adding to requirements in :
 https://review.opendev.org/c/openstack/keystonemiddleware/+/268664
 https://review.opendev.org/c/openstack/keystonemiddleware/+/527466/