Well, one client complain because the server start going to be verry slow. After a short look, I see that where over 20k ESTABLISHED connection from php-fpm to memcached server.
The main problem was that the server didn’t verify if have a connection active and every time was adding a new one.
After a short search we nottice that we have the stable version of memcached ( php module ) , and the new one have something like isPristine function, you won’t find anything on official documentation on pecl site.
So, the fix was to upgrade to memcached-2.0.0b2 .
How to upgrade memcached:
pecl uninstall memcached
pecl install memcached-2.0.0b2
After this you may use into php code  isPristine
