关于数据库连接池C3P0的警告问题

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关于数据库连接池C3P0的警告问题20

系统在启动的时候c3p0报警告信息“A C3P0Registry mbean is already registered. This probably means that an application using c3p0 was undeployed, but not all PooledDataSources were closed prior to undeployment. This may lead to resource leaks over time. Please take care to close all PooledDataSources.”
请问这是什么问题？
运行境是多个系统访问共同的数据库，每个系统里有自己的连接池c3p0，c3p0的一些参数都是默认参数。其中一个系统重启的时候报以上警告信息。

问题补充：

gdfloyd 写道

翻译下，不准确不要怪：
c3p0的托管bean已经注册了，意味着应用程序当反部署（取消部署？）的时候，并非所有数据源都在取消部署时关闭。时间一长，这会导致资源泄漏。请注意关闭所有连接池~~~~~

用spring管理的话，服务器关闭会自动释放db连接
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
</bean>

连接池是spring来管理的，不过忘记加destroy-method="close"，但是tomcat在关闭的时候数据库中检测到链接已经断开。

问题补充：警告原因已找到。当一个tomcat下启动两个或两个以上使用了C3P0的系统时，就会出现以上警告信息。
有源代码可以看出问题（attemptManageC3P0Registry方法），也就是c3p0的托管bean已经注册l，再次注册的时候就会警告。

/*
 * Distributed as part of c3p0 v.0.9.1.2
 *
 * Copyright (C) 2005 Machinery For Change, Inc.
 *
 * Author: Steve Waldman <swaldman@mchange.com>
 *
 * This library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2.1, as 
 * published by the Free Software Foundation.
 *
 * This software 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this software; see the file LICENSE.  If not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307, USA.
 */


package com.mchange.v2.c3p0.management;

import java.lang.management.*;
import javax.management.*;
import com.mchange.v2.log.*;
import com.mchange.v2.c3p0.*;

public class ActiveManagementCoordinator implements ManagementCoordinator
{
    private final static String C3P0_REGISTRY_NAME = "com.mchange.v2.c3p0:type=C3P0Registry";
    
    //MT: thread-safe
    final static MLogger logger = MLog.getLogger( ActiveManagementCoordinator.class );

    MBeanServer mbs;

    public ActiveManagementCoordinator() throws Exception
    {
        this.mbs = ManagementFactory.getPlatformMBeanServer();
    }

    public void attemptManageC3P0Registry() 
    {
        try
        {
            ObjectName name = new ObjectName(C3P0_REGISTRY_NAME );
            C3P0RegistryManager mbean = new C3P0RegistryManager();

            if (mbs.isRegistered(name)) 
            {
                if (logger.isLoggable(MLevel.WARNING))
                {
                    logger.warning("A C3P0Registry mbean is already registered. " +
                                    "This probably means that an application using c3p0 was undeployed, " +
                                    "but not all PooledDataSources were closed prior to undeployment. " +
                                    "This may lead to resource leaks over time. Please take care to close " +
                                    "all PooledDataSources.");  
                }
                mbs.unregisterMBean(name);
            }
            mbs.registerMBean(mbean, name);
        }
        catch (Exception e)
        { 
            if ( logger.isLoggable( MLevel.WARNING ) )
                logger.log( MLevel.WARNING, 
                        "Failed to set up C3P0RegistryManager mBean. " +
                        "[c3p0 will still function normally, but management via JMX may not be possible.]", 
                        e);
        }
    }

    public void attemptUnmanageC3P0Registry() 
    {
        try
        {
            ObjectName name = new ObjectName(C3P0_REGISTRY_NAME );
            if (mbs.isRegistered(name))
            {
                mbs.unregisterMBean(name);
                if (logger.isLoggable(MLevel.FINER))
                    logger.log(MLevel.FINER, "C3P0Registry mbean unregistered.");
            }
            else if (logger.isLoggable(MLevel.FINE))
                logger.fine("The C3P0Registry mbean was not found in the registry, so could not be unregistered.");   
        }
        catch (Exception e)
        {
            if ( logger.isLoggable( MLevel.WARNING ) )
                logger.log( MLevel.WARNING, 
                        "An Exception occurred while trying to unregister the C3P0RegistryManager mBean." +
                        e);
        }
    }
    
    public void attemptManagePooledDataSource(PooledDataSource pds) 
    {
        String name = getPdsObjectNameStr( pds );
        try
        {
            //PooledDataSourceManager mbean = new PooledDataSourceManager( pds );
            //mbs.registerMBean(mbean, ObjectName.getInstance(name));
            //if (logger.isLoggable(MLevel.FINER))
            //    logger.log(MLevel.FINER, "MBean: " + name + " registered.");

            // DynamicPooledDataSourceManagerMBean registers itself on construction (and logs its own registration)
            DynamicPooledDataSourceManagerMBean mbean = new DynamicPooledDataSourceManagerMBean( pds, name, mbs );
        }
        catch (Exception e)
        { 
            if ( logger.isLoggable( MLevel.WARNING ) )
                logger.log( MLevel.WARNING, 
                        "Failed to set up a PooledDataSourceManager mBean. [" + name + "] " +
                        "[c3p0 will still functioning normally, but management via JMX may not be possible.]", 
                        e);
        }
    }
   
    
    public void attemptUnmanagePooledDataSource(PooledDataSource pds) 
    {
        String nameStr = getPdsObjectNameStr( pds );
        try
        {
            ObjectName name = new ObjectName( nameStr );
            if (mbs.isRegistered(name))
            {
                mbs.unregisterMBean(name);
                if (logger.isLoggable(MLevel.FINER))
                    logger.log(MLevel.FINER, "MBean: " + nameStr + " unregistered.");
            }
            else 
                if (logger.isLoggable(MLevel.FINE))
                    logger.fine("The mbean " + nameStr + " was not found in the registry, so could not be unregistered.");   
        }
        catch (Exception e)
        { 
            if ( logger.isLoggable( MLevel.WARNING ) )
                logger.log( MLevel.WARNING, 
                        "An Exception occurred while unregistering mBean. [" + nameStr + "] " +
                        e);
        }
    }
    
    private String getPdsObjectNameStr(PooledDataSource pds)
    { return "com.mchange.v2.c3p0:type=PooledDataSource[" + pds.getIdentityToken() + "]"; }
}

DAO

2010年3月11日 13:01

springoflove
11
0 0 1

4个答案按时间排序按投票排序

0 0

好像是参数问题，看看下面的配置能解决不

<bean id="dataSource"
		class="com.mchange.v2.c3p0.ComboPooledDataSource"
		destroy-method="close">
		<property name="driverClass"
			value="${dataSource.driverClassName}" />
		<property name="jdbcUrl" value="${dataSource.url}" />
		<property name="user" value="${dataSource.username}" />
		<property name="password" value="${dataSource.password}" />

		<!--连接池中保留的最小连接数。-->
		<property name="minPoolSize" value="1" />
		<!--连接池中保留的最大连接数。Default: 15 -->
		<property name="maxPoolSize" value="30" />
		<!--初始化时获取的连接数，取值应在minPoolSize与maxPoolSize之间。Default: 3 -->
		<property name="initialPoolSize" value="2" />
		<!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。Default: 3 -->
		<property name="acquireIncrement" value="2" />
		<!--最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->
		<property name="maxIdleTime" value="1800" />
		<!--JDBC的标准参数，用以控制数据源内加载的PreparedStatements数量。但由于预缓存的statements
			属于单个connection而不是整个连接池。所以设置这个参数需要考虑到多方面的因素。
			如果maxStatements与maxStatementsPerConnection均为0，则缓存被关闭。Default: 0-->
		<property name="maxStatements" value="0" />
		<!--每1800秒检查所有连接池中的空闲连接。Default: 0 -->
		<property name="idleConnectionTestPeriod" value="1800" />
		<!--定义在从数据库获取新连接失败后重复尝试的次数。Default: 30 -->
		<property name="acquireRetryAttempts" value="30" />
		<!--获取连接失败将会引起所有等待连接池来获取连接的线程抛出异常。但是数据源仍有效
			保留，并在下次调用getConnection()的时候继续尝试获取连接。如果设为true，那么在尝试
			获取连接失败后该数据源将申明已断开并永久关闭。Default: false-->
		<property name="breakAfterAcquireFailure" value="true" />
		<!--因性能消耗大请只在需要的时候使用它。如果设为true那么在每个connection提交的
			时候都将校验其有效性。建议使用idleConnectionTestPeriod或automaticTestTable
			等方法来提升连接测试的性能。Default: false -->
		<property name="testConnectionOnCheckout" value="false " />
		<!--连接关闭时默认将所有未提交的操作回滚。Default: false -->
		<property name="autoCommitOnClose" value="true"></property>
	</bean>

2010年3月12日 13:46