I have a bunch of sites built off the same profile, and recently noticed the pages aren't being cached. I spent some time doing the usual: looking for
drupal_set_message calls, disabling all the modules that might disable page cache, as defined here. I've also dug into
drupal_page_get_cache. This lead me to the database, where it turns out the
cache_page table is empty.
This is clearly the source of the issue, I'm just not sure how/what is preventing the page cache. What I'd like to do is to figure out where page cache is writing to the database, and do a debug_backtrace, or just
dpm from that point backward.
A) Is there a point in drupal core where cache_page is written to? B) Any other ideas for debuggings this? (please don't say disable all modules, then re-enable, we have upwards of 200 modules in place with a dozen custom module with interdependencies)
After posting this I opened my IDE and realized I had found the
DrupalDatabaseCache->set method, and that the
$cid is never called into that function.