Mike Matrigali wrote: > Note that the problem we are trying to solve is multiple derby > instances from 2 classloaders accessing the same database at the > same time. We are unlikely to ever allow this - as correct > direct access to the database requires sharing a lot of information > (page cache, lock tables, ...). > > I am not happy with the system property approach - but best I could > come up with so far, and the thread describes the problems with current > lock files. > > I don't know much about what is and is not available from different > classloaders. I think all that is needed is some way to generate a > unique key which can be used to identify what jvm instance I am in. The > pid > of the jvm would work, but I don't think it is available from java. > Then each classloader in the jvm could use some sort of file lock to > tell if another classloader in the same jvm existed.
I guess I'm not seeing the jump from unique jvm id to use of a file lock. If a file lock doesn't prevent multiple threads within a JVM from modifying a file, how does the unique jvm id help? Dan.
