Hello, You may want to take a completely different approach. 1) If your session is lightweight (no really heavy objects) you could store everything in cookies and go completely session and stateless. This would solve most of the problems. 2) If 1. isn't applicable - persist the session to a distributed db and simply save the id of the session in the db in a cookie. let the db's synchronize theirself between the data centers. Make it the db-admin's problem :-)
I would go for 1) You can save a lot of data in the cookie: userId, locale, encrypted auth data, form selections etc. You shouldn't save heavyweight data, like search result with megabytes of data in cookies, but you could save the query and simple repeat the query if the browser changed data centers. It's all cheaper as to synchronize tomcat instances across data centers. In fact all you need is to write your own session implementation and a session manager. Say 2-3 Days of work. Approx 4000 Dollar. best regards Leon On Wed, Aug 26, 2009 at 3:05 AM, Andre-John Mas<aj...@sympatico.ca> wrote: > > On 25-Aug-2009, at 20:52, Hassan Schroeder wrote: > >> On Tue, Aug 25, 2009 at 5:38 PM, Andre-John Mas<aj...@sympatico.ca> wrote: >> >>> ... The architecture would involve >>> a DNS server perodically giving out a DNS address for one DNS server and >>> then an address for the other. >> >> Huh? > > Teaches me to proof read. The DNS server gives the IP address of the load > balancer of one data center, with TTL of 30 seconds, and then hands out > the IP address of the load balancer of the other data center. I don't > have the exact details, but this is what I have been told. > > One thing that I wonder is how we can be sure that the browser tries the > data center that is has been previously been using if the address has been > purged from the local DNS cache, but the client is still meant to be in > session. Not really a Tomcat issue, though I would be curious if there are > any Tomcat related case studies in this vane. > >>> I see there is clustering available with Tomcat, but I don't see how this >>> works across data centers, if at all. >> >> You might want to research "distributed load balancing" -- it's been >> a while since I've had to deal with it, so the hardware options have >> doubtless changed. (Cisco's Remote Director was pretty much the >> only game in town at the time.) > > Thanks for the pointer, I will see what I can find. > > André-John > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
