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WP Super Cache
site keeps crashing (12 posts)

  1. pluggyboy
    Member
    Posted 2 years ago #

    Hi Donncha,

    my site is a fairly heavy custom wp build, with around 50,000 articles and 20,000 + registered users. Since we installed wp super cache the site has been performing amazingly under load (better than any of the other caching plugins, tried 'em all so well done for that!).

    However... we're getting whole site crashes pretty regularly (every few hours) which are only rectifiable by renaming the wp super cache folder via ftp, and then reverting to the correct folder name when live.

    We've got the site running over 2 x quad core machines, i've increased php memory limit and defined WP_MEMORY_LIMIT.

    Site is at http://www.c21media.net, and I'm happy to pay for your consultancy services in getting this running properly asap. Please contact me dave [at] brandydigital [dot] com. thanks in advance or Skype @pluggyboy.

    http://wordpress.org/extend/plugins/wp-super-cache/

  2. Donncha O Caoimh
    Member
    Plugin Author

    Posted 2 years ago #

    You're running it on 2 machines? Do you have a shared folder for the cached folder? That might be the reason for the crashes. If you using 2 machines I'd recommend Batcache as that uses memcached to store the cached files.

  3. pluggyboy
    Member
    Posted 2 years ago #

    the site on one machine, the dbase on the other machine. we think the issue may be with APC so are turning that off on the server for the time being.

    Are there any known issues running this along side the plugin?

  4. Donncha O Caoimh
    Member
    Plugin Author

    Posted 2 years ago #

    Ah, I've had problems with APC too. Xcache works better although I think I've had problems with that too! I eventually put varnish in front of Apache to make my site even faster.

  5. pluggyboy
    Member
    Posted 2 years ago #

    will give that a go. unfortunately, it seems that APC wasn't causing the issue... any other ideas? able to take a (paid) look for me?

  6. Donncha O Caoimh
    Member
    Plugin Author

    Posted 2 years ago #

    You have 20,000 registered users. Do they have to be logged in to use the site? That nullifies most of the advantages of a full page caching plugin as each cached page will contain personal info (like the comment form) and the plugin will create legacy wp-cache files.

    You could change the expiry down to 3600 seconds, or even lower, and a scheduled timer of 3700 seconds (just a little more than the expiry in other words) as that will clear out the vast numbers of legacy cache files that will accumulate.

  7. pluggyboy
    Member
    Posted 2 years ago #

    the majority of users visit the site in non-logged in mode, so i'm not sure that this is causing the issue. looking in the cache at most times, i'm only seeing like 10 - 20 files in each cache: http://screencast.com/t/btPjjkajiS8 so i can't see that the legacy cache files would be the issue either..

    any other ideas?

  8. Donncha O Caoimh
    Member
    Plugin Author

    Posted 2 years ago #

    I'd have expected a lot more than 20 files with 20,000 registered users and that much content. Something odd is happening on your site!

  9. pluggyboy
    Member
    Posted 2 years ago #

    yes, clearly. I'm running it along with Cloudflare.com, might that be causing any issues? I'm looking at the cache stats right now, and there's nothing in the cache at all...

  10. Donncha O Caoimh
    Member
    Plugin Author

    Posted 2 years ago #

    I can't think of what might be causing this problem for you, sorry. You could try examining the cache directory next time you have to rename it - maybe there's some page cached there that shouldn't be.

  11. pluggyboy
    Member
    Posted 2 years ago #

    hey, quick update for you... I ended up turning off Cloudflare, but found that whilst the site was no longer crashing, the cache was still being completely emptied on a regular basis.

    Overnight, i've had someone go through the code and establish that it was a line of code in the buddypress core (bp-core.php line 1888) which was causing the whole cache to empty each time an article was edited / published:

    return prune_super_cache( $cache_path, true );

    commented out that line, and hey presto, i've now got 5000 pages in the cache and growing. hth in case it crops up for anyone else.

  12. Donncha O Caoimh
    Member
    Plugin Author

    Posted 2 years ago #

    Ah yes. Buddypress has code in there to clear the cache. I should add a warning about that in the readme.txt. Unfortunately nobody has fixed that in BP yet and it's been in there for several years.

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