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Session Replication

 
Thomas Becker
Greenhorn
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Hi Cliff,

What do you think about Session Replication? Is it the pure headache as I know it or is it worth to put tons of work to get Session Replication to work as it should.

I worked as a Applications Operations Specialist for big webapplications. They were supposed to replicate their sessions to avoid any outage for the customers during restarts/outages/so on. It sometimes worked and usually put other unwanted side-effects to the portal.

I'm interested in your opinion.

Cheers,
Thomas
[ January 17, 2006: Message edited by: Ilja Preuss ]
 
Stan James
(instanceof Sidekick)
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We use WebSphere session persistence to UDB. Is that the kind of thing you mean? We had a rough start because our vendor framework put some VERY large objects on the session. Since we got rid of those it works fine. We can stop and restart one sick node in the cluster with almost zero user impact.
 
Cliff Berg
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Hi Thomas,

One has to consider the risks and benefits. If a session is persistent, then it is possible to retain the session if a failover occurs. It is also possible for the user to rejoin their session if their app server fails and they failover to another server. These are valuable benefits. But a persistent session is inevitably more resource-intensive. I have seen it work well - even with a home-grown approach. On the other hand, since node failure is rare, it might be more cost-effective to simply restart the session. This would especially be true if the end user is not human (machine-to-machine) or if session content is minimal. If the session persistence mechanism is problem-ridden, it is almost certainly not worth it. I see no inherent reason why it should be problem-ridden though.

- Cliff
 
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