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XF 1.4 Users getting logged out after moving sessions to Memcached

Discussion in 'Troubleshooting and Problems' started by DeltaHF, Mar 31, 2015.

  1. DeltaHF

    DeltaHF Well-Known Member

    I recently started using Memcached to store user sessions, and some Firefox and Android users are now reporting being logged out of their accounts intermittently and prematurely. I did some testing and was able to replicate the issue a few times with Firefox 36.0.4 on OS X. I have no idea how this could be browser related, but Chrome and many of my other users are not experiencing problems.

    Here's my caching configuration in config.php:
    // Cache
    $config['cache']['enabled'] = true;
    $config['cache']['frontend'] = 'Core';
    $config['cache']['frontendOptions']['cache_id_prefix'] = 'gtpxf_';
    $config['cache']['cacheSessions'] = true;
    $config['cache']['backend'] = 'memcached';
    $config['cache']['backendOptions'] = array(
        'compression' => false,
        'servers' => array(
                // your memcached server IP /address
                'host' => 'localhost',
                // memcached port
                'port' => 11211,
    Here's my memcached stats...as you can see, there's plenty of memory available:
    Screen Shot 2015-03-30 at 10.07.42 PM.png

    I have also attached my phpinfo page below.

    One question/point of note...in my config.php, the backend is defined as 'memcached'. I've seen many others here use 'Libmemcached' instead. I don't really understand Libmemcached enough to know why it would be used there, but I believe it is installed with @eva2000's Centminmod (which I've used to set up the server). While troubleshooting, I switched config.php to use 'Libmemcached', but it broke the forums and filled the error logs with the following:

    ErrorException: Memcached::get(): could not read long value, too big - library/Zend/Cache/Backend/Libmemcached.php:166
    I'm not sure what to do next.

    Attached Files:

  2. Mike

    Mike XenForo Developer Staff Member

    The change is entirely server side, so browsers won't be involved.

    I do note that you only have 16MB allocated, so if a large number of sessions come in (such as from a bot), that could push other stuff out and that would cause the issue. You likely want to increase your allocation.

    Alternatively, users can choose to stay logged in and that will effectively prevent the issue.
  3. DeltaHF

    DeltaHF Well-Known Member

    I suspected memory might be an issue, but I immediately viewed the stats after I had personally experienced the problem, and consumption was well below 60% as displayed in the screenshot. I commented the 'cacheSessions' line in config.php last night, and the complaining users reported the problem was gone.

    No memcached sessions for me, I suppose. :(
  4. MattW

    MattW Well-Known Member

    What version of Memcache are you using, and what options do you have set for the daemon?

    In the frontend options, you can set a litetime. Set this to zero, and the session cache will not be cleared out prematurely.

    $config['cache'] = array(
    'enabled'                      => true,
    'cacheSessions'                => true,
    'frontend'                     => 'Core',
    'frontendOptions'              => array(
    'caching'                  => true,
    'cache_id_prefix'          => 'mws_',
    'automatic_serialization'  => true,
    'lifetime'                 => 0),
    'backend'                      => 'Memcached',
    'backendOptions'               => array(
    'servers'                  => array(
    'host'             => 'localhost',
    'port'             => 11211,
    'weight'           => 1
  5. DeltaHF

    DeltaHF Well-Known Member

    Thanks, MattW. I'm going to try the 'lifetime' setting - any drawbacks to setting that to zero? I presume older entries are cleared by memcached as memory is needed?

    Heres' the memcached version info and settings:

    Screen Shot 2015-04-05 at 5.05.01 PM.png

    From /etc/init.d/memcached:
    # chkconfig: - 80 12
    # description:  The memcached daemon is a network memory cache service.
    # processname: memcached
    OPTIONS='-o slab_reassign,slab_automove'
    if [ -f /proc/user_beancounters ]; then
  6. The Forum Heroes

    The Forum Heroes Well-Known Member

    try changing the host from localhost to
  7. DeltaHF

    DeltaHF Well-Known Member

    Interesting. Could you expand on your reasoning behind that and why it would make a difference?
  8. The Forum Heroes

    The Forum Heroes Well-Known Member

    Just have had it happen with customers before. Same with MySQL kicking back invalid user/pass and changing to have fixed both... Just one of life's mysteries i guess :D
    DeltaHF likes this.
  9. Jeremy P

    Jeremy P Well-Known Member

    With MySQL, using localhost will connect via a socket, while will connect using TCP/IP. Sockets must be setup properly to work, and when they aren't then using localhost won't work.

    This may apply to memcached too, but I'm not sure.
    DeltaHF likes this.
  10. DeltaHF

    DeltaHF Well-Known Member

    Hmmm, good to know; thanks, guys. I will make the change in my tests and report back.

    @eva2000 This is a Centminmod box; is there any reason sockets might be unreliable?
  11. MattW

    MattW Well-Known Member

    If you are set up using Centminmod, it doesn't use the socket, it's TCP based.

    /usr/local/bin/memcached -d -m 64 -l -p 11211 -c 1024 -t 4 -n 72 -f 1.25 -u nobody -o slab_reassign slab_automove
    eva2000 likes this.

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