confused by flush_page_cache_test_object_cache_disabled function

To clear a page's cache the flush_page_cache.module attempts to force cache_get() to always return NULL. The assumption and common practice is when cache_get() returns NULL the caller function/module will re-generate and re-cache the data. This module is not actually clearing cached page data but forcing all the cached data on a page to be re-built.

Since Drupal's database cache mechanism can be replaced with memcache or APC, the flush_page_cache_test_object_cache_disabled() function is testing that cache_get() is actual being disabled (returning NULL) as intended.

During the development of the module iamEAP and myself struggled with getting this code to work properly, which is why I added this function to insure that the module is continually confirming that it is working as expected.

I will test it tomorrow. BTW, are you using the most recent version of the memcache module?

So I was able to test flushing the page for memache 6.x-1.9 and 6.x-1.10 and it works without any problem or error message. I definitely need to the know what version you are running.

Are you using both database and memcache for caching or just memcache?

Could you please post your memcache config information?

I wasn't aware of the stampede protection in memcache. It is something I will probably implement on my site in the next few weeks. My guess is the cached data is not being replaced when cache_set() is being called.

Originally, I wanted to avoid telling people to hack their 'memcache.inc' file but I think if you put the below snippet in the beginning of cache_get() in 'memcache.inc', the page's cache will be be completely flushed.

function cache_get($cid, $table = 'cache') {
  // Handle flush page cache requests.
  if (function_exists('flush_page_cache_requested') && flush_page_cache_requested()) {
    cache_clear_all($cid, $table);
    return FALSE;
  }

  ...
}

This hack might be the best way to insure that the page's cache is cleared for any custom 'cache_inc' file provided by a contrib module. Can please test this solution out on your site?

Thanks

So I updated the module and post a new 6.x-1.beta2 release which uses this solution/hack since it insures that this module will always work as expected.

My assumption is that anyone using a contrib cache module will have a reasonable enough level of PHP skill to implement the code.

So, I updated/hacked my memcache.inc on a production site and the below cache_clear_all($cid, $table) call broke my site, basically cached data was being deleted but not regenerated. I am using multiple bins on remote server which might be part of the problem.

function cache_get($cid, $table = 'cache') {
  // Handle flush page cache requests.
  if (function_exists('flush_page_cache_requested') && flush_page_cache_requested()) {
    cache_clear_all($cid, $table);
    return FALSE;
  }

  ...
}

For now, I am going to recommend you use the same code without clear_cache_all().

function cache_get($cid, $table = 'cache') {
  // Handle flush page cache requests.
  if (function_exists('flush_page_cache_requested') && flush_page_cache_requested()) {
    cache_clear_all($cid, $table);
    return FALSE;
  }

  ...
}