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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<code class="hljs less"><span class="hljs-attribute">DEBUG: (BaseJdbcLogger.<span class="hljs-attribute">java:<span class="hljs-number">132)    ooo Using Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl<span class="hljs-variable">@4d4e22e1] [<span class="hljs-number">2014-<span class="hljs-number">07-<span class="hljs-number">17 <span class="hljs-number">15:<span class="hljs-number">19:<span class="hljs-number">35]<span class="hljs-number">5363945354 [Druid-ConnectionPool-Destory-<span class="hljs-number">1422598563] com.alibaba.druid.pool.<span class="hljs-attribute">DruidDataSource:<span class="hljs-number">1132  <span class="hljs-attribute">WARN : (DruidDataSource.<span class="hljs-attribute">java:<span class="hljs-number">1132)   get/close not same thread   <span class="hljs-attribute">ERROR: (DruidDataSource.<span class="hljs-attribute">java:<span class="hljs-number">1815)   abandon connection, open stackTrace         at java.lang.Thread.getStackTrace(Thread.<span class="hljs-attribute">java:<span class="hljs-number">1588)     at com.alibaba.druid.pool.DruidDataSource.getConnectionDirect(DruidDataSource.<span class="hljs-attribute">java:<span class="hljs-number">942)     at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.<span class="hljs-attribute">java:<span class="hljs-number">4534)     at com.alibaba.druid.filter.stat.StatFilter.dataSource_getConnection(StatFilter.<span class="hljs-attribute">java:<span class="hljs-number">661)     at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.<span class="hljs-attribute">java:<span class="hljs-number">4530)     at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.<span class="hljs-attribute">java:<span class="hljs-number">880)     at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.<span class="hljs-attribute">java:<span class="hljs-number">872)     at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.<span class="hljs-attribute">java:<span class="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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<code class="hljs css"><span class="hljs-selector-tag">Caused <span class="hljs-selector-tag">by: <span class="hljs-selector-tag">java<span class="hljs-selector-class">.sql<span class="hljs-selector-class">.SQLException: <span class="hljs-selector-tag">connection <span class="hljs-selector-tag">holder <span class="hljs-selector-tag">is <span class="hljs-selector-tag">null     <span class="hljs-selector-tag">at <span class="hljs-selector-tag">com<span class="hljs-selector-class">.alibaba<span class="hljs-selector-class">.druid<span class="hljs-selector-class">.pool<span class="hljs-selector-class">.DruidPooledConnection<span class="hljs-selector-class">.checkState(<span class="hljs-selector-tag">DruidPooledConnection<span class="hljs-selector-class">.java<span class="hljs-selector-pseudo">:1085)     <span class="hljs-selector-tag">at <span class="hljs-selector-tag">com<span class="hljs-selector-class">.alibaba<span class="hljs-selector-class">.druid<span class="hljs-selector-class">.pool<span class="hljs-selector-class">.DruidPooledConnection<span class="hljs-selector-class">.getMetaData(<span class="hljs-selector-tag">DruidPooledConnection<span class="hljs-selector-class">.java<span class="hljs-selector-pseudo">:825)     <span class="hljs-selector-tag">at <span class="hljs-selector-tag">org<span class="hljs-selector-class">.springframework<span class="hljs-selector-class">.jdbc<span class="hljs-selector-class">.support<span class="hljs-selector-class">.JdbcUtils<span class="hljs-selector-class">.extractDatabaseMetaData(<span class="hljs-selector-tag">JdbcUtils<span class="hljs-selector-class">.java<span class="hljs-selector-pseudo">:285)     ... 70 <span class="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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<code class="hljs java"><span class="hljs-number">941         <span class="hljs-keyword">if (isRemoveAbandoned()) { <span class="hljs-number">942                StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace(); <span class="hljs-number">943                poolalbeConnection.setConnectStackTrace(stackTrace);                 poolalbeConnection.setConnectedTimeNano();                 poolalbeConnection.setTraceEnable(<span class="hljs-keyword">true);                   <span class="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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<code class="hljs lua">                    <span class="hljs-keyword">if (isRemoveAbandoned()) {                         removeAbandoned();                     }</span></code>

 

    继续

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<code class="hljs java">    <span class="hljs-function"><span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">public<span class="hljs-function"> <span class="hljs-keyword"><span class="hljs-function"><span class="hljs-keyword">int<span class="hljs-function"> <span class="hljs-title"><span class="hljs-function"><span class="hljs-title">removeAbandoned<span class="hljs-params"><span class="hljs-function"><span class="hljs-params">()<span class="hljs-function"> {         <span class="hljs-keyword">int removeCount = <span class="hljs-number">0;           <span class="hljs-keyword">long currrentNanos = System.nanoTime();           List<DruidPooledConnection> abandonedList = <span class="hljs-keyword">new ArrayList<DruidPooledConnection>();           <span class="hljs-keyword">synchronized (activeConnections) {             Iterator<DruidPooledConnection> iter = activeConnections.keySet().iterator();               <span class="hljs-keyword">for (; iter.hasNext();) {                 DruidPooledConnection pooledConnection = iter.next();                   <span class="hljs-keyword">if (pooledConnection.isRunning()) {                     <span class="hljs-keyword">continue;                 }                   <span class="hljs-keyword">long timeMillis = (currrentNanos - pooledConnection.getConnectedTimeNano()) / (<span class="hljs-number">1000 * <span class="hljs-number">1000);                   <span class="hljs-keyword">if (timeMillis >= removeAbandonedTimeoutMillis) {                     iter.remove();                     pooledConnection.setTraceEnable(<span class="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.