首页 > 代码库 > 【转】Druid连接池一个设置引发的血案
【转】Druid连接池一个设置引发的血案
https://my.oschina.net/haogrgr/blog/224010
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,
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 threadERROR: (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,
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)
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
if (isRemoveAbandoned()) { removeAbandoned(); }
继续
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="http://www.mamicode.com/true" />
<property name="removeAbandonedTimeout" value="http://www.mamicode.com/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.
【转】Druid连接池一个设置引发的血案