Oh, that is sweet! I was totally unaware of that. Thanks Martin! -- Frank W. Zammetti Founder and Chief Software Architect Omnytex Technologies http://www.omnytex.com
On Fri, March 18, 2005 11:52 am, Martin Wegner said: > > 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] > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
