"RapidMiner Server complains that a database connection was closed. How can I re-establish it"
JBoss pools SQL connections. When connections are closed for various reasons (errors, timeouts, network problems), it does not realize that this has happens and returns closed connections the next time they are required.
Force JBoss to check whether the connection is still live before returning them from the pool. If not, it will re-establish the connection. To achieve this, insert the following into the standalone.xml configuration file (found under standalone/configuration):
<check-valid-connection-sql> sql code</check-valid-connection-sql>
after the XML element
For sql code, insert arbitrary (fast) SQL code like
or (for Microsoft SQL Server)
SELECT 1 FROM sysobjects
Note that this may very slightly influence performance. You may also want to try setting