Options object cache can become out of sync with the database.

[markjaquith]

I have a client with a high volume site (both in terms of view and in terms of entries posted that has been having problems with future-published entries sometimes not publishing at their correct times. I've been monitoring things, and it seems that when problems occur, the object cache has become out of sync with the database. We're using the APC backend in this case, though I don't think that's the cause of the issues.

Specifically, sometimes the database "cron" entry will have cron items that aren't found when you get_option('cron');

There may be a race condition with concurrent updates.

We can likely improve this in the option API, but we might not be able to eliminate it entirely. It may be prudent to revisit our method of storing cron entries, as an option is not a good place to store a frequently-updated serialized array.

The idea of a multi-use "meta" table has been floated, and this might be another good use of that, as cron entries could have their own meta type.

[markjaquith]

Caught it with two conflicting values (note the different publishing times). The one in the DB was right, but not the one in the cache.

_get_cron_array() :

Array
(
   [1192545034] => Array
       (
           [publish_future_post] => Array
               (
                   [c718cfbf7e9d1a40c454cc48cebbe5a7] => Array
                       (
                           [schedule] =>
                           [args] => Array
                               (
                                   [0] => 11915
                               )

                       )

               )

       )

)




DB:

Array
(
   [1192543234] => Array
       (
           [publish_future_post] => Array
               (
                   [c718cfbf7e9d1a40c454cc48cebbe5a7] => Array
                       (
                           [schedule] =>
                           [args] => Array
                               (
                                   [0] => 11915
                               )

                       )

               )

       )

)

[hakre]

I guess this is APC related. Please disable APC and try to reproduce.

[Denis-de-Bernardy]

is this still current in trunk (transcients, new cron procedure...)?

[DD32]

is this still current in trunk (transcients, new cron procedure...)?

Yes.

They mearly use the Object Cache/Database, However, Transient use does mean the database should hopefully not get the data in the first place..

To me, This sounds like the APC cache is not updating itself for some reason.. I somewhat doubt its a WP issue.. but it might depend on the object cache file in use.

[solarissmoke]

This ticket was raised back when there was persistent caching in core. Is it still relevant now?

[nacin]

Going to close this. Our various changes with regards to cron locking has very likely made this much better.