On my drupal 6 site, from time to time, for no obvious reason, all caches gets cleared. Native caching is enabled (normal caching mode, minimum lifetime 1 day). Cron is not setup to run automaticaly. No rules are created regarding flushing of cache. In meantime I do not do any website manipulation like editing content, editing taxonomy or installing new modules. What I can see in recent log entries is that users keep logging in and out, users make orders (ubercart 6) and several not found errors probably caused by bots.
What can trigger such automatic/unwanted cache clearing, what logs should I check or how to fix that? Thank you.

  • It's a long shot, but I did notice just the other day on a drupal 6 here that deleting a taxonomy term does a cache_clear_all() as part of its cleanup. CCK is good at flushing a lot of things, too, when fields are changed.
    – Jimajamma
    Mar 11, 2013 at 19:36
  • Hi, I do not do any changes at all on the website. In the evening I precache all pages and in the morning next day I can see that most of the page_cache entries are gone.
    – loparr
    Mar 11, 2013 at 19:45

1 Answer 1


you could place a watchdog('cache_clear_backtrace', print_r(debug_backtrace(),1); in that cache_clear_all() function to see from the log why/ where that happens.

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