Too many open files when using Memcached for sessions

Ok, I've found the solution thanks to this:

http://php.net/manual/en/memcached.construct.php (see @Tobias comment)

and this https://gist.github.com/K-Phoen/4327229 (see @cmenning comment)

I was using Memcached with a sessions.yml as follows:

session.memcached:    class: Memcached    arguments:       persistent_id: %session_memcached_prefix%    calls:        - [ addServer, [ %session_memcached_host%, %session_memcached_port% ]]session.handler.memcached:    class:     Symfony\Component\HttpFoundation\Session\Storage\Handler\MemcachedSessionHandler    arguments: [@session.memcached, { prefix: %session_memcached_prefix%, expiretime: %session_memcached_expire% }]

It turns out that if you provide a persistent_id argument for Memcached it would persist the connection between requests. From php.net:

persistent_id

By default the Memcached instances are destroyed at the end of the request. To create an instance that persists between requests, use persistent_id to specify a unique ID for the instance. All instances created with the same persistent_id will share the same connection.

The problem is that if you use a persistent_id (Which is better for performance), you have to check if there are already servers added before calling addServer, otherwise it would add a new server & create a new connection, even though it's the same server (it doesn't check for dupes. Something like this:

        $instance = new Memcached($persistent_id);        // Add server if no connections listed.         if (!count($instance->getServerList())) {            $instance->addServers($server);        }

But for that you'd need to create a wrapper class of Memcached. The easy fix is just to comment out this lines, and avoid using persistent connections for the moment:

    #arguments:    #  persistent_id: %session_memcached_prefix%

This solves the issue, even though it's not ideal.I hope it helps you to save some time and avoid a headache!Thanks everyone for your help.

We had this problem which we fixed by caching metadata in memcache in your config.yml

 orm:    default_entity_manager:   default    entity_managers:      default:         metadata_cache_driver:             type: memcache             host: localhost             port: 11211             instance_class: Memcache         query_cache_driver:             type: memcache             host: localhost             port: 11211             instance_class: Memcache

Otherwise if you prefere to cache via apc it also fixes it, i tried both :

 metadata_cache_driver: apc query_cache_driver: apc

Hope this helped, for more informations about this issue : https://github.com/FriendsOfSymfony/FOSUserBundle/issues/1062#issuecomment-29473883