Is there any way to have the JBoss connection pool reconnect to Oracle when connections go bad?

Question

We have our JBoss and Oracle on separate servers. The connections seem to be dropped and is causing issues with JBoss. How can I have the JBoss reconnect to Oracle if the connection is bad while we figure out why the connections are being dropped in the first place?

Answer 1

Whilst you can use the old "select 1 from dual" trick, the downside with this is that it issues an extra query each and every time you borrow a connection from the pool. For high volumes, this is wasteful.

JBoss provides a special connection validator which should be used for Oracle:

<valid-connection-checker-class-name>     org.jboss.resource.adapter.jdbc.vendor.OracleValidConnectionChecker </valid-connection-checker-class-name> 

This makes use of the proprietary ping() method on the Oracle JDBC Connection class, and uses the driver's underlying networking code to determine if the connection is still alive.

However, it's still wasteful to run this each and every time a connection is borrowed, so you may want to use the facility where a background thread checks the connections in the pool, and silently discards the dead ones. This is much more efficient, but means that if the connections do go dead, any attempt to use them before the background thread runs its check will fail.

See the wiki docs for how to configure the background checking (look for background-validation-millis).

Answer 2

There is usually a configuration option on the pool to enable a validation query to be executed on borrow. If the validation query executes successfully, the pool will return that connection. If the query does not execute successfully, the pool will create a new connection.

The JBoss Wiki documents the various attributes of the pool.

<check-valid-connection-sql>select 1 from dual</check-valid-connection-sql> 

Seems like it should do the trick.