You can also use the Jakarta Commons ID packageto generate a GUID which is guaranteed to be unique in the universe. You could then convert the GUID to your seed.
--- Kris Schneider <[EMAIL PROTECTED]> wrote: > Will InetAddress.getLocalHost() work for you? > NetworkInterface.getNetworkInterfaces() might also be of interest. Or, > you > might want to create yourself an instance of java.rmi.dgc.VMID... > > Quoting "Frank W. Zammetti" <[EMAIL PROTECTED]>: > > > Oh boy, I got a good one! It's only related to Struts in that the > > application in question is Struts-based, so I hope no one minds a > semi-OT > > question... > > > > Here's the situation... An app I wrote has a daemon thread that is > spawned > > at startup (from a Struts plugin) that does periodic background > processing > > tasks. This works great, never had a bit of trouble. > > > > Now though, the app is moving from a single server to a clusted > environment. > > > > So, what's going to happen is that each server in the cluster will > have > > its own instance of the thread running on it. Not a huge problem > except > > that I have to be sure only one instance of the thread (i.e., one > server > > in the cluster) is executing concurrently. > > > > The easy solution is just a database table that is checked when the > thread > > wakes up. If there is no entry in it, then there is no other instance > > running, so it can write an entry to the table and go off and do its > > thing. > > > > I want to be extremely certain that no issues arise in terms of one > > instance of the thread reading from the database while another > instance is > > writing, etc. So, aside from transactional database calls and > row-level > > locking, I want to do one more thing: I want the thread to sleep a > random > > number of seconds (1-300) at startup. This will ensure that, all the > > database locking and such aside, the threads should all be offset from > one > > another in terms of when they run. > > > > So, I need a random number generated when the thread starts up. As we > all > > know though, random number generation on most computers that don't > have > > something like a Brownian motion sensor attached stuck in a cup of > boiling > > coffee can't generate truly random numbers. So, in theory, what could > > happen is that if all the servers in the cluster come up at the same > time, > > the threads could wind up running at the same time regardless of the > > random sleep at the start! It might never happen in reality, small > > fluctuations would probably offset them anyway, but I want to be more > > certain than that. > > > > So now we're at the crux of the problem... > > > > I can't just seed the random number generator with the current time > > because it concievably might not be random enough. So, I thought I > could > > just tally up the octets of the server's IP address and add that to > the > > current time. Then the seed on each server should be different > enough. > > > > But, there doesn't appear to be any way to get the server IP address > > independant of a request, so I can't get at it in my plugin. Anyone > know > > differently? > > > > Assuming that is the case, can anyone think of any other way to seed > the > > generator that would ensure a different value on different machines in > the > > cluster? There are some options like encoding the individual server > names > > in my app's config file with a different seed value for each, but that > > makes maintenance a pain if a new server is added or one removed or > > addresses simply changed. > > > > Any ideas? Thanks! > > > > -- > > Frank W. Zammetti > > Founder and Chief Software Architect > > Omnytex Technologies > > http://www.omnytex.com > > -- > Kris Schneider <mailto:[EMAIL PROTECTED]> > D.O.Tech <http://www.dotech.com/> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
