背景介绍
在一次druid数据库连接池连接泄露的排查分析介绍了连接泄露的分析排查过程，但是对造成连接泄露的场景描述的不是太详细，下面通过代码的方式来复现连接泄露的case。
复现过程
连接泄露场景
模拟了在设置了phyTimeoutMillis参数情况下，连接泄露的场景。
连接泄露模拟代码
import com.alibaba.druid.pool.DruidConnectionHolder; import com.alibaba.druid.pool.DruidDataSource; import com.alibaba.druid.pool.DruidPooledConnection; import java.util.List; import java.util.Map; public class DruidAbandonedCase4PhyTimeout { public static void main(String[] args) throws Exception{ DruidDataSource dataSource = new DruidDataSource(); dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver"); dataSource.setUsername("root"); dataSource.setPassword("123456"); dataSource.setUrl("jdbc:mysql://127.0.0.1:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=false"); dataSource.setMinIdle(2); // 保证不会触发DestroyTask，以便手动调用shrink dataSource.setTimeBetweenEvictionRunsMillis(1 * 60 * 60 * 1000); // 物理连接超时时长(超过该阈值会close掉物理连接) dataSource.setPhyTimeoutMillis(1000); dataSource.setMinEvictableIdleTimeMillis(500); dataSource.setKeepAliveBetweenTimeMillis(501); dataSource.init(); DruidPooledConnection connection1 = dataSource.getConnection(); DruidConnectionHolder holder1 = connection1.getConnectionHolder(); System.out.println(holder1); try{ //假装该连接使用了500ms，要小于phyTimeoutMillis，以免归还连接的时候被discard了 Thread.sleep(500L); }catch (Exception e){ e.printStackTrace(); } DruidPooledConnection connection2 = dataSource.getConnection(); DruidConnectionHolder holder2 = connection2.getConnectionHolder(); System.out.println(holder2); connection2.close(); connection1.close(); System.out.println("调用shrink【之前】，连接池中连接情况,begin"); List<Map<String, Object>> conns = dataSource.getPoolingConnectionInfo(); for(Map<String,Object> conn : conns){ System.out.println(conn.get("id")); } System.out.println("调用shrink【之前】，连接池中连接情况,end"); try{ // 让连接1的物理连接时间超过phyTimeoutMillis，以观察连接1是否会被连接池释放掉 Thread.sleep(501L); }catch (Exception e){ e.printStackTrace(); } System.out.println(); System.out.println("物理连接时间,begin"); long ctm = System.currentTimeMillis(); System.out.println(holder1 + " phyConnectTimeMillis:" + (ctm - holder1.getConnectTimeMillis()) + " ,idleMillis:" + (ctm - holder1.getLastActiveTimeMillis())); System.out.println(holder2 + " phyConnectTimeMillis:" + (ctm - holder2.getConnectTimeMillis()) + " ,idleMillis:" + (ctm - holder2.getLastActiveTimeMillis())); System.out.println("物理连接时间,end"); System.out.println(); // 手动执行shrink dataSource.shrink(true); System.out.println("调用shrink【之后】，连接池中连接情况,begin"); conns = dataSource.getPoolingConnectionInfo(); for(Map<String,Object> conn : conns){ System.out.println(conn.get("id")); } System.out.println("调用shrink【之后】，连接池中连接情况,end"); System.out.println(); System.out.println(holder1 + " isClosed:" + holder1.getConnection().isClosed()); System.out.println(holder2 + " isClosed:" + holder2.getConnection().isClosed()); } }
运行以上程序，输出结果如下：
{ID:26004719, ConnectTime:"2023-10-10 12:40:04", UseCount:1, LastActiveTime:"2023-10-10 12:40:04"} {ID:31314834, ConnectTime:"2023-10-10 12:40:05", UseCount:1, LastActiveTime:"2023-10-10 12:40:05"} 调用shrink【之前】，连接池中连接情况,begin 31314834 26004719 调用shrink【之前】，连接池中连接情况,end 物理连接时间,begin {ID:26004719, ConnectTime:"2023-10-10 12:40:04", UseCount:1, LastActiveTime:"2023-10-10 12:40:05"} phyConnectTimeMillis:1011 ,idleMillis:501 {ID:31314834, ConnectTime:"2023-10-10 12:40:05", UseCount:1, LastActiveTime:"2023-10-10 12:40:05"} phyConnectTimeMillis:502 ,idleMillis:501 物理连接时间,end 调用shrink【之后】，连接池中连接情况,begin 26004719 调用shrink【之后】，连接池中连接情况,end {ID:26004719, ConnectTime:"2023-10-10 12:40:04", UseCount:1, LastActiveTime:"2023-10-10 12:40:05"} isClosed:true {ID:31314834, ConnectTime:"2023-10-10 12:40:05", UseCount:1, LastActiveTime:"2023-10-10 12:40:05"} isClosed:false
期望执行结果：
ID是26004719的连接应该从连接池中删除，ID是31314834的连接应该被连接池管理
实际执行结果：
ID是26004719的连接没有从连接池删除；ID是31314834的连接却从连接池删除了，且连接没有被关闭，即ID是31314834的连接既没有被连接池管理又没有被关闭，属于泄露的连接。
测试了druid 1.1.11，1.2.0，1.2.8 ~ 1.2.17，1.2.18~1.2.20，其中【1.1.11，1.2.0，1.2.8 ~ 1.2.17】都存在以上连接泄露的问题，1.2.18~1.2.20不存在以上连接泄露的问题了。
