Question

My app got the error:

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after connection closed.
        at sun.reflect.GeneratedConstructorAccessor281.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
        at com.mysql.jdbc.Util.getInstance(Util.java:381)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)

When my app sees that error it automatically retry the operation. But when I did a tcpdump and I don’t see any new tcp connection is created at that time. It looks like the same tcp connection is used. So why I get the exception? My app uses c3p0 connection pool and I set c3p0 to test connection before check in. Is there any settings to mysql driver or c3p0 to get around this problem?

Answer 1

testConnectionOnCheckin alone is insufficient to ensure that Connections don’t time out in the pool. if the pool is not very busy, Connections may remained checked-in and idle indefinitely. testConnectionOnCheckin should be combined with idleConnectionTestPeriod, so that idle Connections are periodically verified as well.

see http://www.mchange.com/projects/c3p0/#configuring_connection_testing

good luck!