C3PO connection pool goes stale/ not getting called?

JoeCritter · **Posted:** Sun Mar 27, 2005 1:00 pm

The FAQ for use with mySQL says to use C3P0 to avoid having Hibernate become unable to connect to the database after >hand waving< a while of inactivity. I do this.

This does the job nicely on my Windows dev box.

It however doesn't work so great when I deploy. The first query I try gives me an exception if nothing has happened for too long.

Using Hibernate 3.0 RC1 and C3P0 with MySQL 4.1.

hibernate.cfg.xml snippet:

Code:

        <property name="show_sql">true</property>
        <property name="dialect">org.hibernate.dialect.MySQLInnoDBDialect</property>
        <property name="connection.username">xxxxx</property>
        <property name="connection.password">xxxxx</property>
       <property name="connection.driver_class">org.gjt.mm.mysql.Driver</property>
       <property name="connection.url">jdbc:mysql://localhost:3306/xx</property>
       <property name="c3p0.minPoolSize">5</property>
       <property name="c3p0.maxPoolSize">20</property>
       <property name="c3p0.timeout">1800</property>
       <property name="c3p0.max_statement">50</property>
       <property name="hibernate.transaction.factory_class">
         org.hibernate.transaction.JDBCTransactionFactory
       </property>

Exception snippet follows. I find it curious no C3P0 code seems to get called. I assume this must mean I have a misconfiguration above.

Code:

java.io.EOFException
        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1394)
        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:1538)
        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:1929)
        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1167)
        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1278)
        at com.mysql.jdbc.Connection.execSQL(Connection.java:2247)
        at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1586)
        at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:107)
        at org.hibernate.loader.Loader.getResultSet(Loader.java:1183)
        at org.hibernate.loader.Loader.doQuery(Loader.java:363)
        at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:203)
        at org.hibernate.loader.Loader.doList(Loader.java:1499)
        at org.hibernate.loader.Loader.list(Loader.java:1482)
        at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:111)
        at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1246)
        at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:299)

swaldman · **Joined:** Tue Jan 06, 2004 8:58 pm **Posts:** 145

Hi,

Your hibernate config should have

<property name="c3p0.min_size">5</property>
<property name="c3p0.max_size">20</property>

instead of...

<property name="c3p0.minPoolSize">5</property> 
<property name="c3p0.maxPoolSize">20</property> 

Please see http://www.mchange.com/projects/c3p0/in ... appendix_d for more info.

I gather from a comment on hibernate's wiki ( http://www.hibernate.org/214.html ) that hibernate looks for the presence of hibernate.c3p0.max_size in deciding whether to use c3p0, so this probably explains why hibernate didn't try to use c3p0 in your app. [Thx markmansour!]

smiles,
Steve

JoeCritter · **Posted:** Wed Mar 30, 2005 1:56 am

Thank you. That fixed it.

I had cut and pasted that snippet from The Hibernate 2.1 manual some time back. I would not have had the C3P0 native property name otherwise...