文章转自：http://my.oschina.net/haogrgr/blog/224010 非常感谢原作者，思路非常清晰
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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DEBUG: (BaseJdbcLogger.java:
132 ) ooo Using Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl @4d4e22e1 ]
[
2014 – 07 – 17 15 : 19 : 35 ] 5363945354 [Druid-ConnectionPool-Destory- 1422598563 ] com.alibaba.druid.pool.DruidDataSource: 1132
WARN : (DruidDataSource.java:
1132 ) get/close not same thread
ERROR: (DruidDataSource.java:
1815 ) abandon connection, open stackTrace at java.lang.Thread.getStackTrace(Thread.java: 1588 ) at com.alibaba.druid.pool.DruidDataSource.getConnectionDirect(DruidDataSource.java: 942 ) at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java: 4534 ) at com.alibaba.druid.filter.stat.StatFilter.dataSource_getConnection(StatFilter.java: 661 ) at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java: 4530 ) at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java: 880 ) at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java: 872 ) at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java: 97 ) |
这个是最初的异常, 后面还有一大批异常,
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Caused by: java.sql.SQLException: connection holder is
null at com.alibaba.druid.pool.DruidPooledConnection.checkState(DruidPooledConnection.java: 1085 ) at com.alibaba.druid.pool.DruidPooledConnection.getMetaData(DruidPooledConnection.java: 825 ) at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java: 285 ) … 70 more |
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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941
if (isRemoveAbandoned()) {
942
StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
943
poolalbeConnection.setConnectStackTrace(stackTrace); poolalbeConnection.setConnectedTimeNano(); poolalbeConnection.setTraceEnable( true ); synchronized (activeConnections) { activeConnections.put(poolalbeConnection, PRESENT); } } |
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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if (isRemoveAbandoned()) { removeAbandoned(); } |
继续
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public int removeAbandoned() { int removeCount = 0 ; long currrentNanos = System.nanoTime(); List<DruidPooledConnection> abandonedList = new ArrayList<DruidPooledConnection>(); synchronized (activeConnections) { Iterator<DruidPooledConnection> iter = activeConnections.keySet().iterator(); for (; iter.hasNext();) { DruidPooledConnection pooledConnection = iter.next(); if (pooledConnection.isRunning()) { continue ; } long timeMillis = (currrentNanos – pooledConnection.getConnectedTimeNano()) / ( 1000 * 1000 ); if (timeMillis >= removeAbandonedTimeoutMillis) { iter.remove(); pooledConnection.setTraceEnable( false ); abandonedList.add(pooledConnection); } } } ….略 } |
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.
原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/13730.html