Adds a core.internal_cache_read_only config variable to Kohana's internals.
Kohana's internal_cache for find_file wasn't working in Gallery because the cache would be emptied on each request after reading it from disk and before most lookups would run.
1. Bootstrap sets initial core.modules (= include path): forge, kohana23_compat, gallery.
2. Kohana::setup() loads find_file cache from disk.
3. Gallery loads list of active modules and themes, and updates the core.modules value (=include path), which forces the internal find_file cache to be empties (which makes sense).
4. Request processing starts, and thus 80% of all Kohana::find_file() triggered is_file() invocations start off with an empty find_file cache.
In the case of my small Gallery installation, we're talking about 3100 is_file() invocations per request with or without internal_cache enabled. With this fix, this number is down to 800 invocations.
The basic idea is that we treat the cache as read only and don't write any (possibly dirty) values to it in memory until we're sure that the include path won't change later on in the request processing. Once we know the list of active modules and themes, we can update core.modules and finally flip the read-only state of the cache and start writing to it.
Kohana makes this type of transition fairly straightforward in that
all controllers/helpers/etc are still located in the cascading
filesystem without any extra effort, except that I've temporarily
added a hack to force modules/gallery into the module path.
Rename what's left of "core" to be "application" so that it conforms
more closely to the Kohana standard (basically, just
application/config/config.php which is the minimal thing that you need
in the application directory)
There's still considerable work left to be done here.
