HazelCast --> what is hazel cast?

Today I looked at HazelCast and wrote some code using the library. I found this library to be extremely useful and simple. Some of the advantages found in hazelcast are,

1. It can be used as a No-SQL data store - http://www.hazelcast.org/use-cases/in-memory-nosql/
2. Useful for messaging (pub/sub, topics etc...) - http://www.hazelcast.org/use-cases/messaging/
3. Can be used as a data-grid - http://www.hazelcast.org/use-cases/data-grid/
4. Can be used for caching - http://www.hazelcast.org/use-cases/caching/
5. For application scaling - http://www.hazelcast.org/use-cases/application-scaling/
6. For clustering sessions in java web apps - http://www.hazelcast.org/use-cases/clustering/

clustering

clustering an application enables apps to scale out and cater a large audience. most renowned servers supports this feature. when one node goes down other nodes are present to cater the user requests. but what happens to the session of the server which went down? well the session replication across the cluster becomes very important in this case. if you take jboss, it replicates using messages. tomcat also supports it when it is clustered and uses a communication framework called Tribes to achieve it.

A simple how to cluster and do session replication with jboss can be found in the following article.

https://docs.jboss.org/author/display/AS71/AS7+Cluster+Howto?_sscc=t