Question

I read this advice from error message:

You should consider either expiring
and/or testing connection validity
before use in your application,
increasing the server configured
values for client timeouts, or using
the Connector/J connection property
‘autoReconnect=true’ to avoid this
problem.

I’m using Spring and JPA. Where should I configure Connector/J? (in persistence.xml, or in entityManagerFactory spring configuration, or in dateSource spring configuration, or somewhere else?)

Answer 1

The text describes three solutions to prevent connection aborts:

1. Configure the connection string with autoReconnect=true. This is a property of the URL connection string, which works at the driver level. You need to change the connection string in the data source configuration.

   url="jdbc:mysql://localhost:3306/confluence?autoReconnect=true"
   

2. Increase the timeout. This is normally a property of the database. You can increase this value to see if you get less connection abort.

3. Configure the connection pool to test the connection validatiy. This is done at the pool, not a the driver level. This will depend on the data source implementation that you use. But it should be configurable in the property of the data source, if you use a pooled one, e.g. c3p0.

   • Connection pooling options with JDBC: DBCP vs C3P0
   • http://snipplr.com/view/14725/c3p0-datasource-config-connectionpool/
   • http://www.mchange.com/projects/c3p0/index.html#configuring_connection_testing

Additionnal comments:

• The datasource/pool can also have a timeout, which corresponds to the time an idle connection remains in the pool. To not confused with the db timeout.
• There are several way to test the validity of a connection. One common way is to have dummy test table. The pool will issue a select on the dummy test table to see if the connection is still OK.