Clustering and Failover
Novell Cool Solutions: Question & Answer
Q:
VS wrote: Questions from a newbie in iChain field. How can iChain can be configured in a clustered environment? Is a load balancer required to balance the load between two iChain servers? What changes are required in standard iChain installation and configuration to accommodate the failover?
A:
iChain can be clustered by configuring the authentication session broker between the iChain servers participating in the cluster. The session broker allows iChain sessions to be shared between multiple iChain servers and thus allows for failover. For example, when an iChain server fails, and the load balancer forwards the HTTP traffic to an iChain server that is up, that iChain server through the session broker will get the user's authentication context so that the user need not log in again.
The only functionality provided by the session broker is the sharing of iChain authentication sessions. iChain servers in a cluster will not communicate with each other to check each other's availability. For distributing traffic within a cluster for load balancing and failover you will have to use a load balancer.
However there is a caveat here. If you are planning to use more than one back-end Web server and if these back-end Web servers cannot share their session and if you plan to load balance through iChain using the "load-balance-at-session-level-only" switch, then users would lose their back-end sessions when the iChain failover happens because the new iChain server would select one of the back-end servers in random.
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