Re: Memory leak with c3p0 using ConnectionProperties

Achim Abeling <[email protected]> Fri, 02 Jun 2006 11:38:05 +0200

Newsgroups	gmane.comp.db.mysql.java
Message-ID	<[email protected]>

Another solution could be to use weak references as in the attached patch.

Greetings
Achim

Achim Abeling wrote:
> Hi Mark,
> 
> I think the problem is in com.mysql.jdbc.profiler.ProfileEventSink where 
> the map CONNECTIONS_TO_SINKS is filled but elements are never removed.
> 
> How about this patch with which the Connections are garbage collected in 
> my test case:
> 
> 1. add
> public static synchronized void removeInstance(Connection conn)
> {
>     CONNECTIONS_TO_SINKS.remove(conn);
> }
> to ProfileEventSink
> 
> 2. add
> ProfileEventSink.removeInstance(this);
> to the finally block in Connection.realClose
> 
> Best regards
> Achim
> 
> 
> Achim Abeling wrote:
>> Hi Mark,
>>
>> Mark Matthews wrote:
>>
>>>
>>> Achim,
>>>
>>> Adding "profileSQL=true" to your URL causes the driver to log _every_
>>> query to System.err, or another defined logger, so depending on how your
>>> logging is setup, that could be filling a lot of memory due to how your
>>> logging system buffers things.
>>
>> I am using log4j and the MySQL driver seems to log automatically to 
>> the log4j logger "MySQL" in this case.
>> The problem occurs even if I set the loglevel for this logger to 
>> ERROR, so nothing is logged.
>>
>> But the fact remains that the number of com.mysql.jdbc.Connection 
>> objects in the heap is increasing.
>> It is not the logging system that takes the memory.
>>
>> BTW: I thought the problem would occur with any property setting in 
>> the JDBC url but it seems to arise only with "profileSQL".
>>
>>>
>>> "profileSQL" is not designed to be used in a production setting, is
>>> there a reason you're running it in this manner?
>>>
>>
>> No. I will remove it.
>>
> 
>


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ProfileEventSink.java (text/plain, 2.5 KB)

/*
 Copyright (C) 2002-2004 MySQL AB

 This program is free software; you can redistribute it and/or modify
 it under the terms of version 2 of the GNU General Public License as 
 published by the Free Software Foundation.

 There are special exceptions to the terms and conditions of the GPL 
 as it is applied to this software. View the full text of the 
 exception in file EXCEPTIONS-CONNECTOR-J in the directory of this 
 software distribution.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



 */
package com.mysql.jdbc.profiler;

import java.util.Map;
import java.util.WeakHashMap;

import java.lang.ref.WeakReference;

import java.sql.SQLException;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.log.Log;

/**
 * @author mmatthew
 */
public class ProfileEventSink {

	private static final Map CONNECTIONS_TO_SINKS = new WeakHashMap();

	private Connection ownerConnection = null;

	private Log log = null;

	/**
	 * Returns the ProfileEventSink that handles profiler events for the given
	 * connection.
	 * 
	 * @param conn
	 *            the connection to handle events for
	 * @return the ProfileEventSink that handles profiler events
	 */
	public static synchronized ProfileEventSink getInstance(Connection conn) {
		WeakReference ref =
			(WeakReference) CONNECTIONS_TO_SINKS.get(conn);
		
		ProfileEventSink sink = null;
		if (ref!=null) {
			sink = (ProfileEventSink) ref.get();
		}

		if (sink == null) {
			sink = new ProfileEventSink(conn);
			CONNECTIONS_TO_SINKS.put(conn, new WeakReference(sink));
			System.out.println("CONNECTIONS_TO_SINKS.size: "
					+CONNECTIONS_TO_SINKS.size());
		}

		return sink;
	}

	/**
	 * Process a profiler event
	 * 
	 * @param evt
	 *            the event to process
	 */
	public void consumeEvent(ProfilerEvent evt) {
		if (evt.eventType == ProfilerEvent.TYPE_WARN) {
			this.log.logWarn(evt);
		} else {
			this.log.logInfo(evt);
		}
	}

	private ProfileEventSink(Connection conn) {
		this.ownerConnection = conn;

		try {
			this.log = this.ownerConnection.getLog();
		} catch (SQLException sqlEx) {
			throw new RuntimeException("Unable to get logger from connection");
		}
	}

}