Re: Database sessions garbage collection issue

By default there is 1% chance for gc to be called by PHP.
If you want to test if gc() is fired, increase session.gc_probability close to divisor:
http://www.php.net/manual/en/session.configuration.php#ini.session.gc-probability
Then watch SQL log for that query.

Anyway, expires should be current timestamp + Session.timeout config
I know, PHP and sessions - nothing but sorcery :D

On Wednesday, August 1, 2012 9:12:13 AM UTC+2, Crazy wrote:

I'm having some issues with my sessions.

It's probably configuration somewhere, but don't know what to change/where to look.

I'm using database sessions for my cake application, these sessions are not getting cleaned up.

The app in question I have the issue on is an old one written on 1.3.10 running with php version 5.3.5. The garbage collection function in the 2.x branch is the same so don't think the framework version will matter.

I've tracked down the issue to the function __gc located in the CakeSession class and that function is registered there in the php session_set_save_handler function, this is the function in question:

  /**   * Helper function called on gc for database sessions.   *   * @param integer $expires Timestamp (defaults to current time)   * @return boolean Success   * @access private   */  function __gc($expires = null) {      $model =& ClassRegistry::getObject('Session');        if (!$expires) {          $expires = time();      }                $return = $model->deleteAll(array($model->alias . ".expires <" => $expires), false, false);      return $return;  }  

Now, the comments say that $expires is a timestamp, but this isn't correct according to the php docs:

  gc($lifetime)  The garbage collector callback is invoked internally by PHP periodically in order to purge old session data. The frequency is controlled by session.gc_probability and session.gc_divisor. The value of lifetime which is passed to this callback can be set in session.gc_maxlifetime. Return value should be TRUE for success, FALSE for failure.  

The value for $lifeime, so gc_maxlifetime in php.ini is the following:

  ; After this number of seconds, stored data will be seen as 'garbage' and  ; cleaned up by the garbage collection process.  session.gc_maxlifetime = 3600  

So this results in a query that never deletes anything:

  delete from cake_sessions where expires < 3600;  

Could someone clarify what I'm doing wrong or if this is an issue in cake itself?

I've posted this on ask.cakephp.org as well, when I find the answer I'll make sure to update both locations.

http://ask.cakephp.org/questions/view/database_sessions_garbage_collection_issue 

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