In this release of session replication, Tomcat performs an all-to-all
replication of session state.
This is an algorithm that is only efficient when the clusters are
small. For large clusters, the next
release will support a primary-secondary session replication where
the session will only be stored at one
or maybe two backup servers.
Currently you can use the domain worker attribute (mod_jk > 1.2.8)
to build cluster partitions
with the potential of very scaleable cluster solution.
In order to keep the network traffic down in an all-to-all
environment, you can split your cluster
into smaller groups. This can be easily achieved by using different
multicast addresses for the different groups.
A very simple setup would look like this:
What is important to mention here, is that session replication is
only the beginning of clustering.
Another popular concept used to implement clusters is farming, ie,
you deploy your apps only to one
server, and the cluster will distribute the deployments across the
entire cluster.
This is all capabilities that can go into with the FarmWarDeployer
(s. cluster example at server.xml
)
