So this has been discussed a bit in a couple of threads; and I wanted to bring it all together.
Firstly, we already cache, in an adhoc manner, in model objects. (Case in point: shipit has code to clear(erroneously as it happens) a cache in Person. Secondly, we don't have any cache invalidation patterns at the moment, other than some adhoc and all-slightly-different ones (some things use storm hooks, others explicit methods...). So, lp:~lifeless/launchpad/cachedproperty is a branch which cleans this up : it provides an API for working in more detail with cached properties; it makes SQLBase automatically invalidate cachedproperty caches, and it provides a way for things that know a cache needs to be updated, or removed, to do so across the system. This branch is in ec2 land mode at the moment. I will update the storm notes on the wiki, but here is key message: In SQLBase classes, do not write __storm_invalidation__ hooks anymore: just use cachedproperty, and its all taken care of for you. If you *do* write a hook, be sure to upcall, or else cachedproperty caches won't be cleared. If you are writing pure storm without SQLBase, either don't use cachedproperty at all, or call clear_cachedproperties(self) in a storm invalidation hook. Thirdly, I have a branch which adds moderately extensive caching to Person, with an optional helper to get all the members of a team with all their caches preloaded, this makes /participation on a team take 11 DB queries (and 4 of those are OAuth). I think its a reasonable approach to the short term challenge of getting a bunch of related data for a page or API, and I'm interested in how easy folk find it to read or reuse. There is more we can do to make the idiom work well and be reusable, but I think its pretty good for a early step. (Its very similar to the sorts of methods Danilo talked about, but nicer to use as a consumer, I think). This branch is also reviewed and should be in ec2 land anytime now. It also adds some polish to the cachedproperty helper functions, because until you use something in anger its hard to be sure its complete (it wasn't). When caching, please do so with some thought to likely actions that will need to clear the cache or otherwise modify it. Cheers, Rob _______________________________________________ Mailing list: https://launchpad.net/~launchpad-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~launchpad-dev More help : https://help.launchpad.net/ListHelp
