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]
