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eZSessionGarbageCollector run by PHP during user http request

eZSessionGarbageCollector run by PHP during user http request

Monday 17 May 2010 2:57:45 pm - 1 reply

Hello there,

The method eZSessionGarbageCollector() is set by eZ as a PHP handler for cleaning sessions (session_set_save_handler php function) in eZ 4.0.

While investigating performance issues on our Intranet production clustered RHEL servers, it appears that an important amount of slow queries (from 3 to 6 seconds) are generated by the "DELETE * FROM ezsession... " which is launched by eZSessionGarbageCollector().

With these execution time, having the session garbage collection run during users http request is a nonsense...

Is this setting a recent addition to eZ Publish ?

Do you know of performance "best practices" about eZ Publish which would advise to deactivate session garbage collection in php.ini or a configuration item in eZ Publish which would have the same effect ?

My own analyse would be to set in php.ini the item session.gc_probability to 0 and run ez's cleanup.php as a daily cronjob script, as it was advised for Debian setups.

Any experience on this subject is welcome,

Thanks !

Kevin

Monday 17 May 2010 6:08:01 pm

- that query was altered in 4.2 so that it would not slow down db too much. Now it deletes 100 (or 50?) rows at a time. It's your best bet to fix the problem

- doing it randomly on a statistical basis is the way of php (not just the way of ez)

- you can increase in php.ini gc_probability and lower gc_divisor to have gc happen more frequently. That should make the queries faster if you have a site with lots of traffic (more frequency = fewer rows to delete)

- also diminishing session timeout (3 days by default!) can have a positive impact, as there will be fewer sessions in the db at any given time

- you can set in php.ini gc_probability = 0 and run the query via cronjob, so at least slow queries are not hitting live pages (see the cronjob session_gc.php, added in 4.1)

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