March 01, 2006
Session Replication supported in ObjectGrid
WebSphere XD 6.0.1 which just shipped includes a much revised and improved ObjectGrid component. We added HTTP session replication to the ObjectGrid. It should work with any servlet container and provide better qualities of service when compared with DRS.
The features over DRS would be:
- No dependancy on cells/clusters or WebSphere ND. Completely independant. You can do session replication using a set of single server WebSpheres using the ObjectGrid.
- Synchronous protocol means no data loss.
- Full distributed locking means that affinity is not required for consistency.
- WebSphere plugin is not required.
- TCP based connect models means the number of servlet containers can be large when compared with DRS.
- Works on older versions of WebSphere or even competitive servlet containers like tomcat or jetty. You add the object grid jars to your WAR, update the web.xml to add filters to your servlets and it works.
The next customer question is usually "is it faster?" and the answer is no. ObjectGrid isn't slow but DRS is very fast. DRS is a fully async protocol that can lose data when the load gets a big write spike and is VERY fast in that mode especially when running on WAS 6.0.2 or better. ObjectGrid uses a sync loss less protocol and this means it needs to wait for ACKs. ObjectGrid also implements distributed locking and this slows it down a little more. So, it's not fair to ask is it faster than DRS, it's an apple and pears answer, if you need the additional qualities of service the ObjectGrid provides then DRS simply isn't an option.
So, with the ObjectGrid handling your session replication you gain the above benefits at the expense of some speed. The XD 6.0.1 fix pack which has shipped or will be shipping in the next few days includes a performance improvement for session replication of around 4x faster. We're also continuing to tune it further to improve its performance.
March 1, 2006 | Permalink
Does this mean that we have to do our benchmarks again? ;-)
Posted by: Cameron | Mar 1, 2006 10:46:05 AM
I guess, it's an arms race :) I only wish I could benchmark against you but the lawyers won't let me so while it seems you know where you stand, I won't until A) you tell me :) or B) we bump in a competitive PoC and then I find out the hard way :(
What a world we live in...
Posted by: Billy | Mar 1, 2006 11:37:55 AM
The only time we benchmark against Websphere is in IBM's own labs, so maybe you could accidentally be there .. hehe.
Posted by: Cameron | Mar 1, 2006 12:00:40 PM
Is ObjectGrid available/downloadable separately from WebSphere XD ? I don't have access to an XD installation unfortunately...
Posted by: Alain Rogister | Mar 2, 2006 6:54:33 AM
We're putting an eval version on the web anyday now. It's timebombed to stop working after 60 minutes but you can restart it then and use it again. We just disable it after 60 minutes runtime. It's small, unzip install.
Posted by: Billy | Mar 2, 2006 7:25:26 AM