Druid连接池 报错：abandon connection原因分析

问题现象：

使用Druid的数据库连接池，在进行一个查询SQL的时候，抛出了异常：

[2017-10-20 01:40:59.269 ERROR com.alibaba.druid.pool.DruidDataSource:2189] abandon connection, owner thread: schedulerDuty_Worker-2, connected at : 1508434843057, open stackTrace        at java.lang.Thread.getStackTrace(Thread.java:1552)        at com.alibaba.druid.pool.DruidDataSource.getConnectionDirect(DruidDataSource.java:1068)        at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java:4544)        at com.alibaba.druid.filter.stat.StatFilter.dataSource_getConnection(StatFilter.java:662)        at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java:4540)        at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:992)        at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:984)        at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:103)        at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)        at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)        at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:84)        at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:70)        at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:336)        at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:84)        at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)        at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)        at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)        at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)        at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)        at sun.reflect.GeneratedMethodAccessor696.invoke(Unknown Source)        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)        at java.lang.reflect.Method.invoke(Method.java:498)        at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:434)        at com.sun.proxy.$Proxy61.selectOne(Unknown Source)        at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:167)        at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:82)        at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)        at com.sun.proxy.$Proxy83.isStatisticExist(Unknown Source)        at org.quartz.core.JobRunShell.run(JobRunShell.java:202)        at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:573)ownerThread current state is RUNNABLE, current stackTrace        at java.net.SocketInputStream.socketRead0(Native Method)        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)        at java.net.SocketInputStream.read(SocketInputStream.java:170)        at java.net.SocketInputStream.read(SocketInputStream.java:141)        at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:145)          at org.postgresql.core.VisibleBufferedInputStream.readMore(VisibleBufferedInputStream.java:145)        at org.postgresql.core.VisibleBufferedInputStream.ensureBytes(VisibleBufferedInputStream.java:114)        at org.postgresql.core.VisibleBufferedInputStream.read(VisibleBufferedInputStream.java:73)        at org.postgresql.core.PGStream.ReceiveChar(PGStream.java:274)        at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1661)        at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)        at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:512)        at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:374)        at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:366)        at com.alibaba.druid.filter.FilterChainImpl.statement_execute(FilterChainImpl.java:2489)        at com.alibaba.druid.filter.FilterAdapter.statement_execute(FilterAdapter.java:2451)        at com.alibaba.druid.filter.FilterEventAdapter.statement_execute(FilterEventAdapter.java:188)        at com.alibaba.druid.filter.FilterChainImpl.statement_execute(FilterChainImpl.java:2487)        at com.alibaba.druid.proxy.jdbc.StatementProxyImpl.execute(StatementProxyImpl.java:137)        at com.alibaba.druid.pool.DruidPooledStatement.execute(DruidPooledStatement.java:416)        at org.apache.ibatis.executor.statement.SimpleStatementHandler.query(SimpleStatementHandler.java:73)        at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)        at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)        at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)        at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)        at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)        at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)        at org.apache.ibatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:77)        at sun.reflect.GeneratedMethodAccessor696.invoke(Unknown Source)        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)        at java.lang.reflect.Method.invoke(Method.java:498)        at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:434)        at com.sun.proxy.$Proxy61.selectOne(Unknown Source)        at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:167)        at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:82)        at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)        at com.sun.proxy.$Proxy83.isExist(Unknown Source)

从报错信息中可以提取到，是Druid连接池执行SQL，获取Statement失败，导致的问题

问题分析：

根据异常的第一行，可以得知报错来自于DruidDataSource这个类，根据报错的信息，可以看出是因为执行SQL时获取不到Connection连接，然后去看一下Druid的配置中，有三个配置可以关注一下：

配置 默认值 说明 removeAbandoned false 是否强制关闭连接时长大于removeAbandonedTimeoutMillis的连接 removeAbandonedTimeoutMillis 300 * 1000 一个连接从被连接到被关闭之间的最大生命周期 logAbandoned false 强制关闭连接时是否记录日志

再去查看我们的配置，removeAbandoned是true，代表的意思是 是否关闭连接时长大于一定时长的连接，问题可能是出在这里，去看源代码：

public class DestroyTask implements Runnable {        public DestroyTask() {        }        public void run() {            DruidDataSource.this.shrink(true);            if(DruidDataSource.this.isRemoveAbandoned()) {                DruidDataSource.this.removeAbandoned();            }        }}

发现调用removeAbandoned的位置在这里，这里是一个线程，在连接池初始化的时候会启动一个调度，在定时的时间频度去执行，可以看出这里的判断条件是如果开启了配置，就去执行removeAbandoned()这个方法，来看一下这个方法里面有什么：

public int removeAbandoned() {    int removeCount = 0;    long currrentNanos = System.nanoTime();    ArrayList abandonedList = new ArrayList();    Map var5 = this.activeConnections;    synchronized(this.activeConnections) {        Iterator pooledConnection = this.activeConnections.keySet().iterator();        while(pooledConnection.hasNext()) {             DruidPooledConnection buf = (DruidPooledConnection)pooledConnection.next();             if(!buf.isRunning()) {                long trace = (currrentNanos - buf.getConnectedTimeNano()) / 1000000L;                  if(trace >= this.removeAbandonedTimeoutMillis) {                      pooledConnection.remove();                      buf.setTraceEnable(false);                      abandonedList.add(buf);                  }             }        }    }.................}

这里给出了一部分的代码实现，可以看到问题的原因可能就是出现在这里了，这里进行了一个判断，循环遍历连接池中的连接，如果存活，就判断是否超过了配置的removeAbandonedTimeoutMillis（单位是毫秒，配置里面需要配置秒，有转换），如果超过了时间，我就干死你！

解决方案

问题原因已经找到，那么解决的办法就是将removeAbandoned这个配置设置为false或者不设置（默认就是false），或者将removeAbandonedTimeoutMillis这个时间配置调大：

<!--配置成三十分钟--><property name="removeAbandonedTimeout" value="1800" />

再观察，就不会出现报错的情况了，问题解决~

官方说明：

https://github.com/alibaba/druid/wiki/%E8%BF%9E%E6%8E%A5%E6%B3%84%E6%BC%8F%E7%9B%91%E6%B5%8B