I want to fix this so that the package at least works in 5.0.
Clickthrough is designed to be mounted multiple times (or just once of course), under various nodes where you'd like to survey the traffic. The package is keeping a single cache for all its instances and there is a sweeper proc scheduled at package initialization time. This is set to run at regular intervals and is responsible for updating the database when the cache has reached a certain number of clicks. Now, the problem is that we have _package instance_ parameters that control the interval at which to sweep, and the number of clicks at which to dump to the database, when it ought to be a package level parameter. Also, there are calls to "apm_package_id_from_key clickthrough" which will probably fail if there are more than one instance of Clickthrough mounted in the sitemap.
My suggestion is that - for now - I either hard code the values (interval 300, click_count 100, say) or I move the package instance params (CacheSweeperInterval and MaxNumberOfCachedClicks) to acs-kernel. Hmm, since Clickthrough is not a core package, it might be a bad idea to put the params in acs-kernel ...
What do others think about that?
(Sooner or later, we _really_ need to have package parameters in addition to package instance parameters.)