On Jul 27, 2011, at 6:49 PM, Dzmitry Kazimirchyk (JIRA) wrote: > > There may be some difficulties with this because EHCache unlike OSCache > doesn't have support for cache groups which Cayenne actively uses. As I've > searched this is a major problem for all users migrating from OSCache to > EHCache and EHCache even has Jira for it: > https://jira.terracotta.org/jira/browse/EHC-240 .
Oops. Now I am starting to remember why we picked OSCache against EHCache for Cayenne in the first place... Yeah, seems like OSCache is unique in respect to "cache groups" feature. After a quick repeat look at EhCache after many years, it is definitely pretty advanced (I am surprised it doesn't support groups considering everything else it supports) and I see a bunch of things that I like. E.g. multiple caches per CacheManager allows to split cache into regions which seems suitable to serve for unified cache approach between object and query caches (something that's been on the list for some time). And IIRC this is how Hibernate does it. Besides with some tweaking it allows to emulate a few OSCache behaviors I am used to. E.g. cluster cache replication is done by copy by default, but it can be configured to be done via a much lighter invalidation mechanism (trading consistency for performance - something I am willing to do in the apps I am mostly dealing with). > The question is should we wait for EHCache to implement cache groups or write > our custom solution for this? (or maybe something else) Good question... From the Jira history, this issue has been shifted around for 2 years by Terracotta, so it is hard to tell when it becomes standard. I suspect a custom implementation will be either complex, requiring a rewrite of big parts of EhCache, or inefficient (such as our own MapQueryCache that scans the entire cache to remove all items belonging to a group. I guess we can inspect the user patches and make a decision on that. I think we can start with an implementation that quietly ignores groups and uses a single cache (and hence a single expiration policy) for all query entries. It is rather crippled, as it would preclude targeted invalidation, but it will be a start. And then who knows, maybe EHC-240 is committed. Andrus P.S. Also after joining Terracotta, EhCache became sneaky spyware: http://adammonsen.com/post/512 Big surprise :-/
