Hi,

we are currently drafting/implementing some clustering mechanisms for
Apache OpenMeetings.

I have seen OpenJPA supports the MySQL Replication feature:
http://people.apache.org/~mikedd/nightly.builds/apache-openjpa-2.3.0-SNAPSHOT/docs/docbook/manual/ref_guide_dbsetup_dbsupport.html#ref_guide_dbsetup_dbsupport_mysql
which is great!

However it solves only one side of the cluster: Having the database
clustered.

What happens if you want to cluster OpenJPA itself on multiple nodes? Each
OpenJPA instance would have its own data-cache, how can you make sure those
caches are synchronized across all nodes in your cluster?
And how would you solve the primary key/sequencer issue? When multiple
instances write to the same database they could potentially try to create a
record with the same primary key.

Thanks!
Sebastian

-- 
Sebastian Wagner
https://twitter.com/#!/dead_lock
http://www.webbase-design.de
http://www.wagner-sebastian.com
seba.wagner@gmail.com