摘要: Druid连接池一个设置引发的血案 -- 链接池出现问题

原文来自：http://www.cnblogs.com/water-1/p/6843960.html

摘要: Druid连接池一个设置引发的血案

    今天在一台配置很低的机器上运行批量更新的程序~~~

    大概跑了三十分钟~~~这配置~~~这程序~~~

    然后华丽丽的报异常了~~~

    具体异常是这样的,

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<codeclass="hljs less"><spanclass="hljs-attribute">DEBUG: (BaseJdbcLogger.<spanclass="hljs-attribute">java:<spanclass="hljs-number">132)    ooo Using Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl<spanclass="hljs-variable">@4d4e22e1]

[<spanclass="hljs-number">2014-<spanclass="hljs-number">07-<spanclass="hljs-number">17 <spanclass="hljs-number">15:<spanclass="hljs-number">19:<spanclass="hljs-number">35]<spanclass="hljs-number">5363945354 [Druid-ConnectionPool-Destory-<spanclass="hljs-number">1422598563] com.alibaba.druid.pool.<spanclass="hljs-attribute">DruidDataSource:<spanclass="hljs-number">1132 

<spanclass="hljs-attribute">WARN : (DruidDataSource.<spanclass="hljs-attribute">java:<spanclass="hljs-number">1132)   get/close not same thread

 

<spanclass="hljs-attribute">ERROR: (DruidDataSource.<spanclass="hljs-attribute">java:<spanclass="hljs-number">1815)   abandon connection, open stackTrace

        at java.lang.Thread.getStackTrace(Thread.<spanclass="hljs-attribute">java:<spanclass="hljs-number">1588)

    at com.alibaba.druid.pool.DruidDataSource.getConnectionDirect(DruidDataSource.<spanclass="hljs-attribute">java:<spanclass="hljs-number">942)

    at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.<spanclass="hljs-attribute">java:<spanclass="hljs-number">4534)

    at com.alibaba.druid.filter.stat.StatFilter.dataSource_getConnection(StatFilter.<spanclass="hljs-attribute">java:<spanclass="hljs-number">661)

    at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.<spanclass="hljs-attribute">java:<spanclass="hljs-number">4530)

    at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.<spanclass="hljs-attribute">java:<spanclass="hljs-number">880)

    at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.<spanclass="hljs-attribute">java:<spanclass="hljs-number">872)

    at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.<spanclass="hljs-attribute">java:<spanclass="hljs-number">97)</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></code>

 

    这个是最初的异常, 后面还有一大批异常,

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<codeclass="hljs css"><spanclass="hljs-selector-tag">Caused <spanclass="hljs-selector-tag">by: <spanclass="hljs-selector-tag">java<spanclass="hljs-selector-class">.sql<spanclass="hljs-selector-class">.SQLException: <spanclass="hljs-selector-tag">connection <spanclass="hljs-selector-tag">holder <spanclass="hljs-selector-tag">is <spanclass="hljs-selector-tag">null

    <spanclass="hljs-selector-tag">at <spanclass="hljs-selector-tag">com<spanclass="hljs-selector-class">.alibaba<spanclass="hljs-selector-class">.druid<spanclass="hljs-selector-class">.pool<spanclass="hljs-selector-class">.DruidPooledConnection<spanclass="hljs-selector-class">.checkState(<spanclass="hljs-selector-tag">DruidPooledConnection<spanclass="hljs-selector-class">.java<spanclass="hljs-selector-pseudo">:1085)

    <spanclass="hljs-selector-tag">at <spanclass="hljs-selector-tag">com<spanclass="hljs-selector-class">.alibaba<spanclass="hljs-selector-class">.druid<spanclass="hljs-selector-class">.pool<spanclass="hljs-selector-class">.DruidPooledConnection<spanclass="hljs-selector-class">.getMetaData(<spanclass="hljs-selector-tag">DruidPooledConnection<spanclass="hljs-selector-class">.java<spanclass="hljs-selector-pseudo">:825)

    <spanclass="hljs-selector-tag">at <spanclass="hljs-selector-tag">org<spanclass="hljs-selector-class">.springframework<spanclass="hljs-selector-class">.jdbc<spanclass="hljs-selector-class">.support<spanclass="hljs-selector-class">.JdbcUtils<spanclass="hljs-selector-class">.extractDatabaseMetaData(<spanclass="hljs-selector-tag">JdbcUtils<spanclass="hljs-selector-class">.java<spanclass="hljs-selector-pseudo">:285)

    ... 70 <spanclass="hljs-selector-tag">more</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></code>

 

    说什么holder为空

    第一眼看到holder就像到Spring的源码, 里面到处是holder(笑)

    但是这里的holder不是Spirng里面的,是Druid的

    这个holder大概是用来hou住连接池里面的连接的.

    然后为什么为空了呢? 目测是哪个链接坏了, 或者被意外的关闭了...

    根据异常调源码  at com.alibaba.druid.pool.DruidDataSource.getConnectionDirect(DruidDataSource.java:942)

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<codeclass="hljs java"><spanclass="hljs-number">941         <spanclass="hljs-keyword">if (isRemoveAbandoned()) {

<spanclass="hljs-number">942                StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();

<spanclass="hljs-number">943                poolalbeConnection.setConnectStackTrace(stackTrace);

                poolalbeConnection.setConnectedTimeNano();

                poolalbeConnection.setTraceEnable(<spanclass="hljs-keyword">true);

 

                <spanclass="hljs-keyword">synchronized (activeConnections) {

                    activeConnections.put(poolalbeConnection, PRESENT);

                }

            }</span></span></span></span></span></span></code>

 

    看不出啥来. 只能将日志继续看看, 还是看不出啥来

    然后看了上面代码几遍后, 老觉得 isRemoveAbandoned() 这个方法有鬼.

    查看调用处,:

    恩, 这个DestroyConnectionThread非常可疑, 跳

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<codeclass="hljs lua">                    <spanclass="hljs-keyword">if (isRemoveAbandoned()) {

                        removeAbandoned();

                    }</span></code>

 

    继续

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<codeclass="hljs java">    <spanclass="hljs-function"><spanclass="hljs-keyword"><spanclass="hljs-function"><spanclass="hljs-keyword">public<spanclass="hljs-function"> <spanclass="hljs-keyword"><spanclass="hljs-function"><spanclass="hljs-keyword">int<spanclass="hljs-function"> <spanclass="hljs-title"><spanclass="hljs-function"><spanclass="hljs-title">removeAbandoned<spanclass="hljs-params"><spanclass="hljs-function"><spanclass="hljs-params">()<spanclass="hljs-function"> {

        <spanclass="hljs-keyword">int removeCount = <spanclass="hljs-number">0;

 

        <spanclass="hljs-keyword">long currrentNanos = System.nanoTime();

 

        List<DruidPooledConnection> abandonedList = <spanclass="hljs-keyword">new ArrayList<DruidPooledConnection>();

 

        <spanclass="hljs-keyword">synchronized (activeConnections) {

            Iterator<DruidPooledConnection> iter = activeConnections.keySet().iterator();

 

            <spanclass="hljs-keyword">for (; iter.hasNext();) {

                DruidPooledConnection pooledConnection = iter.next();

 

                <spanclass="hljs-keyword">if (pooledConnection.isRunning()) {

                    <spanclass="hljs-keyword">continue;

                }

 

                <spanclass="hljs-keyword">long timeMillis = (currrentNanos - pooledConnection.getConnectedTimeNano()) / (<spanclass="hljs-number">1000 * <spanclass="hljs-number">1000);

 

                <spanclass="hljs-keyword">if (timeMillis >= removeAbandonedTimeoutMillis) {

                    iter.remove();

                    pooledConnection.setTraceEnable(<spanclass="hljs-keyword">false);

                    abandonedList.add(pooledConnection);

                }

            }

        } ....略

    }</span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span></code>

 

    擦, 这里不对头,   timeMillis >= removeAbandonedTimeoutMillis  timeMillis 这个是getConnection()被调用时的时间

    意思就是一个连接被get后, 超过了 removeAbandonedTimeoutMillis这么久我就弄死你.

    然后继续找removeAbandonedTimeoutMillis 这玩意在哪里设置的   ,最后发现是在

 

<property name="removeAbandoned" value="true" />

<property name="removeAbandonedTimeout" value="1800" />

    初始化配置的这里设置的,  这两个参数的大概意思就是, 

    通过datasource.getConnontion() 取得的连接必须在removeAbandonedTimeout这么多秒内调用close(),要不我就弄死你.(就是conn不能超过指定的租期)

    然后调成2个小时~~~

    然后程序成功跑完~~~华丽丽的等了50分钟

    总结:

    连接池为了防止程序从池里取得连接后忘记归还的情况, 而提供了一些参数来设置一个租期, 使用这个可以在一定程度上防止连接泄漏

    但是如果你的业务真要跑这么久~~~~那还是注意下这个设置.