问题描述
我目前正在研究在MysqL数据库之间切换以检查某些更改的内容。但是,当使用下面的switchSource
方法切换数据库和主机时,将导致切换成功,但是连接保持打开状态,似乎没有关闭或遵循setMaxIdleTime
设置。
所以发生的事情是,每次它连接到数据库主机和数据库时,它都会创建更多的连接,每次重新连接时都会不断累积,直到数据库主机停止接受连接并返回“太多连接”错误为止。
我想知道如何最好地关闭这些连接。
运行查询时,它们处于try catch(例如try (Connection conn = DataSource.getInstance().getConnection())
)中,并且在catch之前也关闭了语句。加上setMaxIdleTime
,我不确定为什么没有关闭连接。
如果有人能对此有所了解,我将非常感激。感谢您的阅读。
package com.example.database;
import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.sqlException;
import java.util.Properties;
import com.example.base.ShardNode;
import com.example.manage.ShardManager;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import static com.example.manage.ShardManager.shardNodeList;
// see https://www.javatips.net/blog/c3p0-connection-pooling-example
public class DataSource {
private static DataSource datasource;
private ComboPooledDataSource cpds;
private static int currentShardId = -1;
private static ShardNode currentShardNode;
private static boolean dbIsNotSpecified;
private static boolean clearConnections = false;
private static String GetDatabaseUrlAndDB(ShardNode selectedShard) {
System.out.println(selectedShard.getFullUrl() + ShardManager.getDatabaseName(currentShardId));
if (dbIsNotSpecified) {
return selectedShard.getFullUrl();
}
return selectedShard.getFullUrl() + ShardManager.getDatabaseName(currentShardId);
}
private DataSource() throws PropertyVetoException {
this.cpds = new ComboPooledDataSource();
this.cpds.setDriverClass("com.MysqL.cj.jdbc.Driver");
this.cpds.setJdbcUrl(GetDatabaseUrlAndDB(currentShardNode));
this.cpds.setUser(currentShardNode.getUsername());
this.cpds.setPassword(currentShardNode.getpassword());
// the settings below are optional -- c3p0 can work with defaults
// cpds.setinitialPoolSize(5);
// cpds.setMinPoolSize(5);
// cpds.setAcquireIncrement(5);
// cpds.setMaxPoolSize(100);
// cpds.setMaxStatements(100);
/*
* Set this low to prevent connections from hanging around after the worker has left
* Otherwise it results in too many connections being made on a single node and the server
* starts rejecting new connections.
*/
// cpds.setMaxIdleTime(1);
}
/* Refreshes the datasource to use a new id */
public static void switchSource(int shardId,boolean dbnotSpecified) throws PropertyVetoException {
// Todo continue work here. Pass id to data source and pull through credentials
currentShardId = shardId;
dbIsNotSpecified = dbnotSpecified;
for(ShardNode CurrentShard: shardNodeList) {
if ((shardId >= CurrentShard.getStartingShard())
&& (shardId <= CurrentShard.getEndingShard())) {
currentShardNode = CurrentShard;
datasource = new DataSource();
break;
}
}
if (datasource == null) {
// Handle empty datasources
}
}
public static DataSource getInstance() throws PropertyVetoException {
/*
* If the datasource is null the runner is likely to have
* just been started so use the first shardNode in the list
*/
if (datasource == null) {
currentShardNode = shardNodeList.get(0);
datasource = new DataSource();
}
return datasource;
}
public Connection getConnection() throws sqlException {
return this.cpds.getConnection();
}
}
解决方法
在像您这样的长期存在的程序中,使用完.close()
后,必须Connection
从.getConnection()
获得的任何.getConnection()
对象。如果不这样做,则会出现问题中描述的连接泄漏。
您的DataSource似乎支持池化连接。如此一来,.close()
/ ~/code/
的重复周期就不会对性能造成影响。