Hi Chris, Thanks for bringing up these concerns.
I did a more detailed analysis of our application. Though it keeps 5GB of session data in RAM which are actually disk backed, the active session data will only account for a maximum of 200MB per second. So I am only required to persist this much data in DB every second. Going with the in-memory session replication will require 10GB of RAM on both the tomcat instances. When the session data gets replicated to another node, it gets written on disk of the other node too. Its a Wicket application, and I can't just get away with replicating the disk based session data :-( If I go with persisting sessions in DB, my RAM requirement drops to only 5GB on the cost of more network traffic and 200MB of DB writes per second. We plan to use an NDB cluster for that. But only issue is that Tomcat doesn't persist sessions to DB synchronously as is the case with in-memory replication where session data is first replicated and then the request gets served. So if master fails, and the session data has not been persisted, subsequent requests going to the other tomcat node will see old session data from DB, and might frustrate the *user*. I would like to know how synchronous persistance of session data with Tomcat is done in practice. Thanks, Amit On Mon, Mar 2, 2009 at 12:23 PM, Christopher Schultz <ch...@christopherschultz.net> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Amit, > > On 2/28/2009 9:02 PM, Amit Chandel wrote: >> I am trying to deploy a tomcat cluster. I was able to set up a test >> tomcat cluster using in-memory replication with version 6.0.10, but my >> session data is too much (almost 5 GB per tomcat instance, and using 2 >> nodes in cluster both instances will require 10GB of RAM to hold >> session data). > > Wow, does this thing scale? 5 GB of session data is a /lot/. Have you > considered using either db-backed sessions (that is, writing everything > to the database instead of keeping it in memory) or having your > application itself store things in the db instead of the session? > > - -chris > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (MingW32) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org > > iEYEARECAAYFAkmsFhYACgkQ9CaO5/Lv0PCK3wCdFKK3UW36VBjJuO/TgjmIQWoT > YusAoJ1WNgnn7nnAul84qJ8E7MHHPlJB > =G8Kk > -----END PGP SIGNATURE----- > > --------------------------------------------------------------------- > 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
