On 18 October 2011 18:45, Elias Ross <gen...@noderunner.net> wrote: > On Tue, Oct 18, 2011 at 10:13 AM, Mircea Markus <mircea.mar...@jboss.com> > wrote: > >> The way I see it a user might configure an expiry for two reasons: >> - to manage memory >> and/or >> - to control how much "staleness" the data it uses might have > > I've mostly used expiry to control data staleness. For example, I > would hold a token for security validation. It wasn't entirely > necessary to have a high degree of accuracy, maybe an order of a few > seconds. But in many cases if the expiry thread runs every minute I > suspect this would be too long. > > In my original implementation of expiration for JBoss TreeCache I used > a heap (priority queue) to order entries. This kept the implementation > very fast, at the expense of memory usage of course. > > I agree that doing removals during data access is a very bad idea. > > I would suggest having two user options: 1) Infrequent expiration > scans 2) Or, use of a priority queue and more frequent scanning.
Thanks Elias, feedback from a real use case is exactly what I was needing most. Security tokens is an interesting application; wouldn't it make sense for you to store a timestamp in your value too, and check on that as well? (in combination with automatic expiration). Your suggestions are what I would do too; not sure about the priority queue exactly, but the solution clearly is in making the eviction process more efficient - a priority queue might be a way, or anything else which might make the eviction process quicker. It seems we're discussing implementation details in the other thread "Time measurement and expiry", so I'll give more details there but one of the reasons for me to start these discussions is that if I'm allowed to make these changes, then the eviction process will be much faster as a consequence of not invoking the wall clock at every entry of the cache. How much faster, that's to be measured yet.. focusing this thread on the use cases, what sort of precision would you expect? Should we try to stay under a single second for an average heap (and how big is that?) to be considered "correct" ? _______________________________________________ infinispan-dev mailing list infinispan-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/infinispan-dev
