Memory leak with c3p0 using ConnectionProperties

Hi,

I think I found a memory leak in mysql-connector-3.1.11.

Perhaps the cause for the memory leak is in c3p0, but since the memory 
leak goes away when the JDBC url is changed I first post the problem here.

A class to reproduce the problem is attached.
I am using mysql-connector-3.1.11 and c3p0 version 0.9.0 with JDK 1.5.0.

c3p0 has the possibility to expire idling connections. The test case 
sets an expire time of 1 second.
The log shows that c3p0 really expires the connections and creates new 
connections.

When the JDBC url is
"jdbc:mysql://localhost/test?profileSQL=true"
the memory leak occurs, when it is
"jdbc:mysql://localhost/test"
it occurs not.

The memory leak can be observed by starting the class and then doing a
# jmap -histo <processid> |grep "com.mysql.jdbc.Connection"

On my linux workstation it produces something like this:

Attaching to process ID 14539, please wait...
Debugger attached successfully.
Client compiler detected.
JVM version is 1.5.0-b64
Iterating over heap. This may take a while...
1180872 16401 
com.mysql.jdbc.ConnectionProperties$BooleanConnectionProperty
277200  3465 
com.mysql.jdbc.ConnectionProperties$IntegerConnectionProperty
182952  2541    com.mysql.jdbc.ConnectionProperties$StringConnectionProperty
168168  231     com.mysql.jdbc.Connection
36960   462 
com.mysql.jdbc.ConnectionProperties$MemorySizeConnectionProperty
Heap traversal took 9.15 seconds.

The second number in each line is the object count. And it is increasing.

Greetings
Achim


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package de.freenet.xselling.db;

import java.util.Properties;

import java.sql.Connection;
import java.sql.Statement;

import javax.sql.DataSource;

import com.mchange.v2.c3p0.DataSources;
import com.mchange.v2.c3p0.PoolConfig;

public class C3P0MemoryLeakTest
{

	/**
	 * @param args
	 */
	public static void main(String[] args)
		throws Exception
	{

		PoolConfig pcfg = new PoolConfig();
		pcfg.setInitialPoolSize(10);
		pcfg.setMinPoolSize(10);
		pcfg.setMaxPoolSize(30);
		pcfg.setAcquireIncrement(1);
		/* idle connections expire after 1 second */
		pcfg.setMaxIdleTime(1);
		pcfg.setMaxStatements(0);
		pcfg.setIdleConnectionTestPeriod(30);

		Class.forName("com.mysql.jdbc.Driver");
		
		/**
		 * This URL produces a memory leak
		 */
		String jdbcUrl = "jdbc:mysql://localhost/test?profileSQL=true";
		/**
		 * This one not.
		 */
//		String jdbcUrl = "jdbc:mysql://localhost/test";
		Properties connectionProps = new Properties();
		connectionProps.put("user","root");
		DataSource unpooled = DataSources.unpooledDataSource(
				jdbcUrl, connectionProps);
		DataSource ds = DataSources.pooledDataSource(unpooled, pcfg);
		
		while (true) {
			Thread.sleep(5000);
			System.out.println(System.currentTimeMillis()+": doing testquery");
			Connection conn = ds.getConnection();
			Statement stmt = conn.createStatement();
			stmt.executeQuery("select * from c3p0_testtable");
			conn.close();
			System.gc();
		}
	}

}