Hi

I am pretty much stuck with this problem, I am using hibernate with tomcat and c3p0 with mysql. After a while tomcat crashes with too many open files in the system. It happens too frequently, here are some details .. I didnt find anything helpful searching in forums, so i assume i am doing something wrong somewhere, any help will be appreciated.

Hibernate version:
hibernate3,
Configuration :
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>

<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>

<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

<!-- Echo all executed SQL to stdout -->
<property name="show_sql">false</property>

<property name="c3p0.acquire_increment">1</property>
<property name="c3p0.acquireRetryDelay">1000</property>
<property name="c3p0.acquireRetryAttempts">60</property>
<property name="c3p0.idle_test_period">100</property> <!-- seconds -->

<property name="c3p0.minPoolSize">3</property>
<property name="c3p0.maxPoolSize">20</property>
<property name="c3p0.max_size">100</property>
<property name="c3p0.max_statements">200</property>
<property name="c3p0.min_size">10</property>
<property name="c3p0.timeout">100</property> <!-- seconds -->


Usage pattern :
org.hibernate.Session session = HibernateUtil.getSessionFactory().openSession();
Transaction txn = session.beginTransaction();

Query quert = session.createQuery( ");
query.list();
txn.commit();
session.close() ;

Full stack trace of any exception that occurs:
INFO | jvm 1 | 2007/01/03 17:49:50 | Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2" java.lang.NoClassDefFoundError: com/mysql/jdbc/Messages
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.CommunicationsException.<init>(CommunicationsException.java:174)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:569)INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:971)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.Connection.createNewIO(Connection.java:2644)INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.Connection.<init>(Connection.java:1531)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.Connection.<init>(Connection.java:1531)INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:135)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:978)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1774)
INFO | jvm 1 | 2007/01/03 17:49:50 | at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
INFO | jvm 1 | 2007/01/03 17:52:20 | Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1" java.lang.NoClassDefFoundError: com/mysql/jdbc/Messages
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mysql.jdbc.CommunicationsException.<init>(CommunicationsException.java:174)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:569)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:971)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mysql.jdbc.Connection.createNewIO(Connection.java:2644)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mysql.jdbc.Connection.<init>(Connection.java:1531)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:135)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:978)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1774)
INFO | jvm 1 | 2007/01/03 17:52:20 | at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
INFO | jvm 1 | 2007/01/03 19:57:20 | Exception in thread "com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0" java.lang.NoClassDefFoundError: com/mysql/jdbc/SQLError
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2834)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1573)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1665)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.Connection.execSQL(Connection.java:3118)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.Connection.execSQL(Connection.java:3047)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.Statement.executeQuery(Statement.java:1166)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.DatabaseMetaData$9.forEach(DatabaseMetaData.java:4355)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.DatabaseMetaData$IterateBlock.doForAll(DatabaseMetaData.java:76)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mysql.jdbc.DatabaseMetaData.getTables(DatabaseMetaData.java:4342)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnectionNoQuery(DefaultConnectionTester.java:185)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.DefaultConnectionTester.activeCheckConnection(DefaultConnectionTester.java:62)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.AbstractConnectionTester.activeCheckConnection(AbstractConnectionTester.java:67)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:329)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.finerLoggingTestPooledConnection(C3P0PooledConnectionPool.java:279)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.testPooledConnection(C3P0PooledConnectionPool.java:329)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.finerLoggingTestPooledConnection(C3P0PooledConnectionPool.java:279)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.refurbishIdleResource(C3P0PooledConnectionPool.java:269)INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask.run(BasicResourcePool.java:1962)
INFO | jvm 1 | 2007/01/03 19:57:20 | at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
INFO | jvm 1 | 2007/01/03 19:57:32 | Exception in thread "Timer-2" java.lang.NoClassDefFoundError: com/mchange/v2/io/IndentedWriter
INFO | jvm 1 | 2007/01/03 19:57:32 | at com.mchange.v2.async.ThreadPoolAsynchronousRunner.getMultiLineStatusString(ThreadPoolAsynchronousRunner.java:281)
INFO | jvm 1 | 2007/01/03 19:57:32 | at com.mchange.v2.async.ThreadPoolAsynchronousRunner.access$100(ThreadPoolAsynchronousRunner.java:36)
INFO | jvm 1 | 2007/01/03 19:57:32 | at com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector.run(ThreadPoolAsynchronousRunner.java:616)INFO | jvm 1 | 2007/01/03 19:57:32 | at java.util.TimerThread.mainLoop(Timer.java:512)
INFO | jvm 1 | 2007/01/03 19:57:32 | at java.util.TimerThread.run(Timer.java:462)
STATUS | wrapper | 2007/01/03 22:37:42 | TERM trapped. Shutting down.

Also c3p0 version is - c3p0-0.9.1-pre11.jar, I had same problem with an earlier version.

sanjay,

well, this is a weird one, but it's clear what's going on. c3p0 is trying, but failing, to acquire Connections from mysql. The failure is what's unusual: the class com.mysql.jdbc.Messages can't be loaded, while other mysql driver classes seem to be loadable just file.

Here's the URL of a similar issue, but unfortunately no solution is posted:

http://mail-archives.apache.org/mod_mbox/tomcat-users/200603.mbox/%3C44071456.6030403@ste-energy.com%3E

You eventually run out of file descriptors because the driver has already opened a socket, but the thrown NoClassDefFoundError skips and internal cleanup and prevents a Connection from being returned, so no one can ever call close() on it.

I'm not sure what to tell you with this.

Here's are some suggestions: make sure there aren't somehow two incompatible versions of mysql's jdbc driver somehow visible to your application or tomcat. maybe download a fresh copy of the driver and tomcat, and try running your application from there, without any external CLASSPATH set (and ensuring that there is only a single copy of the jdbc driver jar files in your tomcat installation).

Do verify that mysql is installed and waiting for Conections. Prior to the NoClassDefFoundError, a CommunicationsException occurs -- maybe if you could prevent that from happening, the inability to load the Messages class wouldn't bite (though it's still bad -- and weird -- if unresolved). Try checking whether your app can connect to the database without connection pooling turned on.

Good luck!