2019独角兽企业重金招聘Python工程师标准>>> 
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 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,
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 abandonedList = new ArrayList();
synchronized (activeConnections) {
Iterator 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
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.