低版本Druid连接池+MySQL驱动8.0导致线程阻塞、性能受限


Posted in MySQL onJuly 01, 2021

现象

应用升级MySQL驱动8.0后,在并发量较高时,查看监控打点,Druid连接池拿到连接并执行SQL的时间大部分都超过200ms

对系统进行压测,发现出现大量线程阻塞的情况,线程dump信息如下:

"http-nio-5366-exec-48" #210 daemon prio=5 os_prio=0 tid=0x00000000023d0800 nid=0x3be9 waiting for monitor entry [0x00007fa4c1400000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.loadClass(TomcatEmbeddedWebappClassLoader.java:66)
        - waiting to lock <0x0000000775af0960> (a java.lang.Object)
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1186)
        at com.alibaba.druid.util.Utils.loadClass(Utils.java:220)
        at com.alibaba.druid.util.MySqlUtils.getLastPacketReceivedTimeMs(MySqlUtils.java:372)

根因分析

public class MySqlUtils {

    public static long getLastPacketReceivedTimeMs(Connection conn) throws SQLException {
        if (class_connectionImpl == null && !class_connectionImpl_Error) {
            try {
                class_connectionImpl = Utils.loadClass("com.mysql.jdbc.MySQLConnection");
            } catch (Throwable error){
                class_connectionImpl_Error = true;
            }
        }

        if (class_connectionImpl == null) {
            return -1;
        }

        if (method_getIO == null && !method_getIO_error) {
            try {
                method_getIO = class_connectionImpl.getMethod("getIO");
            } catch (Throwable error){
                method_getIO_error = true;
            }
        }

        if (method_getIO == null) {
            return -1;
        }

        if (class_MysqlIO == null && !class_MysqlIO_Error) {
            try {
                class_MysqlIO = Utils.loadClass("com.mysql.jdbc.MysqlIO");
            } catch (Throwable error){
                class_MysqlIO_Error = true;
            }
        }

        if (class_MysqlIO == null) {
            return -1;
        }

        if (method_getLastPacketReceivedTimeMs == null && !method_getLastPacketReceivedTimeMs_error) {
            try {
                Method method = class_MysqlIO.getDeclaredMethod("getLastPacketReceivedTimeMs");
                method.setAccessible(true);
                method_getLastPacketReceivedTimeMs = method;
            } catch (Throwable error){
                method_getLastPacketReceivedTimeMs_error = true;
            }
        }

        if (method_getLastPacketReceivedTimeMs == null) {
            return -1;
        }

        try {
            Object connImpl = conn.unwrap(class_connectionImpl);
            if (connImpl == null) {
                return -1;
            }

            Object mysqlio = method_getIO.invoke(connImpl);
            Long ms = (Long) method_getLastPacketReceivedTimeMs.invoke(mysqlio);
            return ms.longValue();
        } catch (IllegalArgumentException e) {
            throw new SQLException("getLastPacketReceivedTimeMs error", e);
        } catch (IllegalAccessException e) {
            throw new SQLException("getLastPacketReceivedTimeMs error", e);
        } catch (InvocationTargetException e) {
            throw new SQLException("getLastPacketReceivedTimeMs error", e);
        }
    }

MySqlUtils中的getLastPacketReceivedTimeMs()方法会加载com.mysql.jdbc.MySQLConnection这个类,但在MySQL驱动8.0中类名改为com.mysql.cj.jdbc.ConnectionImpl,所以MySQL驱动8.0中加载不到com.mysql.jdbc.MySQLConnection

getLastPacketReceivedTimeMs()方法实现中,如果Utils.loadClass("com.mysql.jdbc.MySQLConnection")加载不到类并抛出异常,会修改变量class_connectionImpl_Error,下次调用不会再进行加载

public class Utils {

    public static Class<?> loadClass(String className) {
        Class<?> clazz = null;

        if (className == null) {
            return null;
        }

        try {
            return Class.forName(className);
        } catch (ClassNotFoundException e) {
            // skip
        }

        ClassLoader ctxClassLoader = Thread.currentThread().getContextClassLoader();
        if (ctxClassLoader != null) {
            try {
                clazz = ctxClassLoader.loadClass(className);
            } catch (ClassNotFoundException e) {
                // skip
            }
        }

        return clazz;
    }

但是,在Utils的loadClass()方法中同样catch了ClassNotFoundException,这就导致loadClass()在加载不到类的时候,并不会抛出异常,从而会导致每调用一次getLastPacketReceivedTimeMs()方法,就会加载一次MySQLConnection这个类

线程dump信息中可以看到是在调用TomcatEmbeddedWebappClassLoader的loadClass()方法时,导致线程阻塞的

public class TomcatEmbeddedWebappClassLoader extends ParallelWebappClassLoader {

public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
  synchronized (JreCompat.isGraalAvailable() ? this : getClassLoadingLock(name)) {
   Class<?> result = findExistingLoadedClass(name);
   result = (result != null) ? result : doLoadClass(name);
   if (result == null) {
    throw new ClassNotFoundException(name);
   }
   return resolveIfNecessary(result, resolve);
  }
 }

这是因为TomcatEmbeddedWebappClassLoader在加载类的时候,会加synchronized锁,这就导致每调用一次getLastPacketReceivedTimeMs()方法,就会加载一次com.mysql.jdbc.MySQLConnection,而又始终加载不到,在加载类的时候会加synchronized锁,所以会出现线程阻塞,性能下降的现象

getLastPacketReceivedTimeMs()方法调用时机

public abstract class DruidAbstractDataSource extends WrapperAdapter implements DruidAbstractDataSourceMBean, DataSource, DataSourceProxy, Serializable {

    protected boolean testConnectionInternal(DruidConnectionHolder holder, Connection conn) {
        String sqlFile = JdbcSqlStat.getContextSqlFile();
        String sqlName = JdbcSqlStat.getContextSqlName();

        if (sqlFile != null) {
            JdbcSqlStat.setContextSqlFile(null);
        }
        if (sqlName != null) {
            JdbcSqlStat.setContextSqlName(null);
        }
        try {
            if (validConnectionChecker != null) {
                boolean valid = validConnectionChecker.isValidConnection(conn, validationQuery, validationQueryTimeout);
                long currentTimeMillis = System.currentTimeMillis();
                if (holder != null) {
                    holder.lastValidTimeMillis = currentTimeMillis;
                    holder.lastExecTimeMillis = currentTimeMillis;
                }

                if (valid && isMySql) { // unexcepted branch
                    long lastPacketReceivedTimeMs = MySqlUtils.getLastPacketReceivedTimeMs(conn);
                    if (lastPacketReceivedTimeMs > 0) {
                        long mysqlIdleMillis = currentTimeMillis - lastPacketReceivedTimeMs;
                        if (lastPacketReceivedTimeMs > 0 //
                                && mysqlIdleMillis >= timeBetweenEvictionRunsMillis) {
                            discardConnection(holder);
                            String errorMsg = "discard long time none received connection. "
                                    + ", jdbcUrl : " + jdbcUrl
                                    + ", jdbcUrl : " + jdbcUrl
                                    + ", lastPacketReceivedIdleMillis : " + mysqlIdleMillis;
                            LOG.error(errorMsg);
                            return false;
                        }
                    }
                }

                if (valid && onFatalError) {
                    lock.lock();
                    try {
                        if (onFatalError) {
                            onFatalError = false;
                        }
                    } finally {
                        lock.unlock();
                    }
                }

                return valid;
            }

            if (conn.isClosed()) {
                return false;
            }

            if (null == validationQuery) {
                return true;
            }

            Statement stmt = null;
            ResultSet rset = null;
            try {
                stmt = conn.createStatement();
                if (getValidationQueryTimeout() > 0) {
                    stmt.setQueryTimeout(validationQueryTimeout);
                }
                rset = stmt.executeQuery(validationQuery);
                if (!rset.next()) {
                    return false;
                }
            } finally {
                JdbcUtils.close(rset);
                JdbcUtils.close(stmt);
            }

            if (onFatalError) {
                lock.lock();
                try {
                    if (onFatalError) {
                        onFatalError = false;
                    }
                } finally {
                    lock.unlock();
                }
            }

            return true;
        } catch (Throwable ex) {
            // skip
            return false;
        } finally {
            if (sqlFile != null) {
                JdbcSqlStat.setContextSqlFile(sqlFile);
            }
            if (sqlName != null) {
                JdbcSqlStat.setContextSqlName(sqlName);
            }
        }
    }

只有DruidAbstractDataSource的testConnectionInternal()方法中会调用getLastPacketReceivedTimeMs()方法

testConnectionInternal()是用来检测连接是否有效的,在获取连接和归还连接时都有可能会调用该方法,这取决于Druid检测连接是否有效的参数

Druid检测连接是否有效的参数:

  • testOnBorrow:每次获取连接时执行validationQuery检测连接是否有效(会影响性能)
  • testOnReturn:每次归还连接时执行validationQuery检测连接是否有效(会影响性能)
  • testWhileIdle:申请连接的时候检测,如果空闲时间大于timeBetweenEvictionRunsMillis,执行validationQuery检测连接是否有效
  • 应用中设置了testOnBorrow=true,每次获取连接时,都会去抢占synchronized锁,所以性能下降的很明显

解决方案

经验证,使用Druid 1.x版本<=1.1.22会出现该bug,解决方案就是升级至Druid 1.x版本>=1.1.23或者Druid 1.2.x版本

GitHub issue:https://github.com/alibaba/druid/issues/3808

到此这篇关于低版本Druid连接池+MySQL驱动8.0导致线程阻塞、性能受限的文章就介绍到这了,更多相关MySQL驱动8.0低版本Druid连接池内容请搜索三水点靠木以前的文章或继续浏览下面的相关文章希望大家以后多多支持三水点靠木!

MySQL 相关文章推荐
Mysql 性能监控及调优
Apr 06 MySQL
安装配置mysql及Navicat prenium的详细流程
Jun 10 MySQL
MySQL系列之二 多实例配置
Jul 02 MySQL
MySQL系列之十二 备份与恢复
Jul 02 MySQL
MySQL中的隐藏列的具体查看
Sep 04 MySQL
MySQL基础快速入门知识总结(附思维导图)
Sep 25 MySQL
MySQL面试题讲解之如何设置Hash索引
Nov 01 MySQL
面试中老生常谈的MySQL问答集锦夯实基础
Mar 13 MySQL
MySQL中一条update语句是如何执行的
Mar 16 MySQL
MySQL日期时间函数知识汇总
Mar 17 MySQL
讲解MySQL增删改操作
May 06 MySQL
MySQL数据库如何查看表占用空间大小
Jun 10 MySQL
MySQL 8.0 驱动与阿里druid版本兼容问题解决
MySQL query_cache_type 参数与使用详解
Jul 01 #MySQL
mysql 数据插入优化方法之concurrent_insert
Jul 01 #MySQL
MySQL的Query Cache图文详解
MySQL高速缓存启动方法及参数详解(query_cache_size)
Jul 01 #MySQL
mysql优化之query_cache_limit参数说明
Jul 01 #MySQL
MySQL中存储时间的最佳实践指南
Jul 01 #MySQL
You might like
后宫无数却洁身自好的男主,唐三只爱小舞
2020/03/02 国漫
收音机怀古---春雷3P7图片欣赏
2021/03/02 无线电
几个学习PHP的网址
2006/11/25 PHP
探讨PHP使用eAccelerator的API开发详解
2013/06/09 PHP
destoon后台网站设置变成空白的解决方法
2014/06/21 PHP
php转换颜色为其反色的方法
2015/04/27 PHP
使用PHP如何实现高效安全的ftp服务器(二)
2015/12/30 PHP
非常有用的9个PHP代码片段
2016/04/06 PHP
php微信开发之谷歌测距
2018/06/14 PHP
jquery 实现二级/三级/多级联动菜单的思路及代码
2013/04/08 Javascript
JavaScript使表单中的内容显示在屏幕上的方法
2015/06/29 Javascript
JavaScript如何自定义trim方法
2015/07/28 Javascript
JavaScript基础——使用Canvas绘图
2016/11/02 Javascript
JavaScript中使用webuploader实现上传视频功能(demo)
2017/04/10 Javascript
关于jquery中attr()和prop()方法的区别
2018/05/28 jQuery
记一次vue-webpack项目优化实践详解
2019/02/17 Javascript
微信小程序如何实现全局重新加载
2019/06/05 Javascript
基于Node的Axure文件在线预览的实现代码
2019/08/28 Javascript
Vue+Node实现的商城用户管理功能示例
2019/12/23 Javascript
Vue实现多页签组件
2021/01/14 Vue.js
Linux下python3.6.1环境配置教程
2018/09/26 Python
pyqt5 禁止窗口最大化和禁止窗口拉伸的方法
2019/06/18 Python
浅谈Python小波分析库Pywavelets的一点使用心得
2019/07/09 Python
Python单链表原理与实现方法详解
2020/02/22 Python
使用python的turtle函数绘制一个滑稽表情
2020/02/28 Python
基于django 的orm中非主键自增的实现方式
2020/05/18 Python
Python 操作SQLite数据库的示例
2020/10/16 Python
Windows环境下Python3.6.8 importError: DLLload failed:找不到指定的模块
2020/11/01 Python
若通过ObjectOutputStream向一个文件中多次以追加方式写入object,为什么用ObjectInputStream读取这些object时会产生StreamCorruptedException?
2016/10/17 面试题
学生干部的自我评价分享
2014/01/18 职场文书
广告创意求职信
2014/03/17 职场文书
《月亮湾》教学反思
2014/04/14 职场文书
小学一年级学生评语
2014/04/22 职场文书
解除施工合同协议书
2014/10/17 职场文书
整改落实情况汇报材料
2014/10/29 职场文书
Python如何识别银行卡卡号?
2021/06/10 Python