Output cache not deleting expired caches

The behavior is supposed to be that cache files are deleted when a requested page has a cache that has expired. Understand that the deletion mechanism only applies to the specific page request. The deletion process doesn't walk through all the cache files and delete all the expired ones.

Do you use the following?

PHP Code:

$config['cache_query_string'] = TRUE; 


If you do, then any variation in the query string will result in another cache file for that exact combo of URL+ query parameters. If that exact combo of URL+ query parameters is never requested again the cache file will never be deleted.

The config options that will affect cache behavior are

PHP Code:

$config['cache_path']
$config['cache_query_string']
$config['base_url']
$config['index_page'] 


Basically, all of the above affect the name of the cache file. Change any of them and existing cache files are instant orphans.