InetAddress might not get the answer for you, Frank. I don't know what your setup is, but you can go to any ip address service outside your system and get a unique return address for your machines with a mini-browser.
Jack On Fri, 18 Mar 2005 11:36:10 -0500 (EST), Frank W. Zammetti <[EMAIL PROTECTED]> wrote: > Yes, I think InetAddress just might do the trick. Thank you Kris! > > -- > Frank W. Zammetti > Founder and Chief Software Architect > Omnytex Technologies > http://www.omnytex.com > > On Fri, March 18, 2005 11:24 am, Kris Schneider said: > > 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] > > -- "You can lead a horse to water but you cannot make it float on its back." ~Dakota Jack~ --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
