c3p0 connection management problems

Question

Hi,

I'm using Spring 3.0.2, Hibernate 3.5.0 and c3p0 0.9.1.2 and I'm having a ton of errors when it comes down to retrieving connections and commiting transactions. Here's my configuration of c3p0:

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
    <property name="driverClass" value="${jdbc.driverClassName}"/>
    <property name="jdbcUrl" value="${jdbc.url}"/>
    <property name="properties">
        <props>
            <prop key="c3p0.acquireIncrement">5</prop>
            <prop key="c3p0.maxIdleTime">30</prop>
            <prop key="c3p0.idleConnectionTestPeriod">20</prop>
            <prop key="c3p0.maxPoolSize">100</prop>
            <prop key="c3p0.maxStatements">0</prop>
            <prop key="c3p0.minPoolSize">1</prop>
            <prop key="user">${jdbc.username}</prop>
            <prop key="password">${jdbc.password}</prop>
        </props>
    </property>
</bean>

Up until recently I got this error pretty often:

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
Last packet sent to the server was 0 ms ago.

Recently I also get these:

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Connection.close() has already been called. Invalid operation in this state.
java.sql.SQLException: Connections could not be acquired from the underlying database!

Any suggestions?

Answer 1

That's probably because connections are being timed out. Checkout idle_test_period setting or use bonecp (http://jolbox.com) which has sensible defaults instead.