Using the APC PHP cache/accelerator (need help confirming error)

[stevec]

Hi,

After upgrading to 5.1.0c and installing the APC cache, we've had odd date-format errors. I was wondering if anyone who uses the APC cache could confirm or reject what we've found?

It appears that with APC installed and enabled with the recommended settings, date formats in listviews and calendar persist when a user's date format is changed. But to a degree where dates on the same page can differ in format (!?!). This also leads to calls and meetings dissapearing from calendar views.

To replicate:

1. make sure you have the 'my meetings' dashlet set on your home page.
2. Go to the calendar and bring up a view that displays a meeting.
3. Go to 'my account' and change the date format to something unusal - say 2006-12-23
4. Go back to the same calendar view and add another meeting so it should appear near to the other meeting(s)

At this point - the other meetings might be missing - and if you go back to the homepage, the new meeting will be in the 'my meetings' dashlet in the new date-format, but the previous meetings are still in the original format (23/12/2006 in my case).

5. Now, return to 'my accounts' and set the date format back to the original value (23/12/2006)
6. Go back to the chosen calendar view - the old meetings are back. the new meeting might be missing. However, if it is there, opening it up into it's detail view, it will have the dates in the wrong format 2006-12-23
7. go to homepage - the items in the meetings dashlet are showing different date formats - whichever they were saved under.


Now, restarting APC - or using the apc.php web-interface to dynamically clear the 'user cache' will fix the inconsistencies.


Does this happen for others - or is it specific to our setup?

[eggsurplus]

I believe we have the user cache turned off because of this.

[stevec]

Ah,

I couldn't see an individual config to turn that part of the application off - could you let me know what I need to change?

Thanks

[eggsurplus]

I'm sorry, absolutely forgetting what and why we did what we did. We went into config.php and added this entry:

$sugar_config['external_cache_disabled'] = true;

and it seemed to solve the problem.

[stevec]

Hi,

But wouldn't that turn the whole of APC off - not just the user cache? It'd be nice to keep some part of APC running as when it does, sugar runs more that 50% faster.

[eggsurplus]

No, it just turns off Sugar's ability to cache. Your webserver will still use APC to cache Sugar. I'm sure you know this already but make sure to allocate enough memory so that it doesn't fragment. A 256mb seems to be the right mark for us before it starts to fragment which ends up being used up almost 25%. If you haven't already, I highly recommend putting up the apc.php page up on your server but lock it down to be accessible by your network only. The stats are invaluable to help tune it and then to monitor later. I had to restart apache for a different reason a day ago and we already have 12271909 cache hits with 975 misses. We're getting about 96 cache requests a second.

[roblaus]

Can't confirm this behaviour. I have two machines with apc up and on both the date formats behave as they should (dd.mm.yyyy). But we use litespeed and the macines are virtualized with openvz. Maybe this makes a difference.

[stevec]

Thanks, I've configured sugar to not use the cache - but let apache use it for php caching.

Currently running with the sugr recommended 64MB. I'll keep a look out for fragmentation - I assume this is where segments > 1?

I've created a case with sugar about this - I expect it might be something to do with the other speed ups we've implemented in apache.

Cheers,
Steve

[eggsurplus]

No problem. I should have posted this link originally. Helped us a ton: http://docs.moodle.org/en/Installing_APC_in_Windows

[RichW]

Seeing the same issue using memcached as our user/object cache

Does anyone know if Sugar 5.5 has addressed this problem with cached date formats? I'd hate to lose performance due to this issue.

Thanks,
Rich