It seems actually to be an issue rather than a feature (I can't think of a use case where this behavior would be useful); I have created a few test cases (similar to the one you have provided in the other thread) that further analyze your discovery but they don't add much to what you found (apart from confirming the risk of getting stale data). However, when we start design/implement a refactoring of this part of the system, I would suggest that we also consider how to deal with similar scenarios in a clustered deployment (in fact many of the production deployment are based on clusters); the simplest use case could be: in a cluster, we have two OFBiz instances connected to the same database; in one instance the list is cached, in the other instance one of the generic values (that are part of the selection) is updated. A distributed cache system may help here.
Jacopo On Apr 21, 2013, at 10:54 AM, Adrian Crum <adrian.c...@sandglass-software.com> wrote: > Last week I discovered a flaw in the EntityListCache implementation: > http://mail-archives.apache.org/mod_mbox/incubator-ofbiz-dev/201304.mbox/%3c516ac7b4.2020...@sandglass-software.com%3E > > To summarize: Entity conditions that are cached become stale when any member > of the cached list is changed - making the cache contents invalid. In > addition, GenericValues in the cached list are mutable - which is > inconsistent with the primary key cache, where GenericValues from the cache > are immutable. > > I would like to fix this, but I think we should discuss it first. > > One change would be to make the list member GenericValues immutable. This > will make the GenericValues retrieved from the entity list cache consistent > with the GenericValues retrieved from the primary key cache, but it won't > prevent an invalid cache (because the list member GenericValue can be cloned > and modified). Also, this change will likely break a lot of code, because it > is common to retrieve a list of GenericValues from the cache and then make > changes to the list members. We could create a "transitional" GenericValue > that would warn developers when they modify a cached list member, and then > switch to an immutable GenericValue some time in the future. > > To fix the stale cache problem, the cache instance can be made a GenericValue > listener in all of its list members - so any time a list member is modified > the cache will be cleared. This will keep the cache valid, but there might be > a performance hit. I'm open to other solutions to this problem. > > Any thoughts? > > -Adrian > >
