【转】druid 版本bug导致discard connection问题记录

1.项目中遇到的bug，记录一下，以下是转载https://blog.csdn.net/mj158518/article/details/53091064

1. 背景

之前处理了一个mybatis的bug（详见之前的文章），在给系统升级mybatis的时候，想顺便把所有系统的druid也升级了，从版本（0.2.18~1.0.18不等）升级到统一的最新版本（1.0.26）。

但是在beta测试期间，遇到如下异常：

ERROR com.alibaba.druid.pool.DruidDataSource:1243 discard connection
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 1,463,838 milliseconds ago. The last packet sent successfully to the server was 1,463,839 mill
iseconds ago. is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configure
d values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.7.0_45]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.7.0_45]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.7.0_45]
at java.lang.reflect.Constructor.newInstance(Constructor.java:526) ~[na:1.7.0_45]
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) ~[mysql-connector-java-5.1.32.jar:na]
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1137) ~[mysql-connector-java-5.1.32.jar:na]
复现的方法是程序启动后，访问一些需要查库的功能，然后闲置直至超过mysql配置的wait_timeout时间（默认8小时，可以改小，如3分钟，方便复现），再访问需要查库的资源，就出现这个问题了。

2.相关配置

代码封装了一个工厂，对druid进行了统一的配置。

其中和连接相关的配置只有：

url中的autoReconnect=true（但这个看网上说在mysql 5.x以上不管用了，没有具体考证，不敢乱说）

testWhileIdle=true这两条。

3. 代码分析

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查询时会获取连接（DruidDataSource.getConnectionDirect），在内部会检测连接的状态（DruidDataSource.testConnectionInternal）,检测时使用validConnectionChecker.isValidConnection。
下面比较不存在这个问题的1.0.18版本和存在问题的1.0.26版本，通过跟踪代码的执行，发现两个版本在该部分使用的判断逻辑不同，如下：

3.1 1.0.18版本

/*
* Copyright 1999-2101 Alibaba Group Holding Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.alibaba.druid.pool.vendor;

import com.alibaba.druid.pool.DruidPooledConnection;
import com.alibaba.druid.pool.ValidConnectionChecker;
import com.alibaba.druid.pool.ValidConnectionCheckerAdapter;
import com.alibaba.druid.proxy.jdbc.ConnectionProxy;
import com.alibaba.druid.support.logging.Log;
import com.alibaba.druid.support.logging.LogFactory;
import com.alibaba.druid.util.JdbcUtils;
import com.alibaba.druid.util.Utils;

import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class MySqlValidConnectionChecker extends ValidConnectionCheckerAdapter implements ValidConnectionChecker, Serializable {

public static final int DEFAULT_VALIDATION_QUERY_TIMEOUT = 1000;

private static final long serialVersionUID = 1L;
private static final Log LOG = LogFactory.getLog(MySqlValidConnectionChecker.class);

private Class<?> clazz;
private Method ping;
private boolean usePingMethod = false;

public MySqlValidConnectionChecker(){
try {
clazz = Utils.loadClass("com.mysql.jdbc.MySQLConnection");
ping = clazz.getMethod("pingInternal", boolean.class, int.class);
if (ping != null) {
usePingMethod = true;
}
} catch (Exception e) {
LOG.warn("Cannot resolve com.mysq.jdbc.Connection.ping method. Will use 'SELECT 1' instead.", e);
}

configFromProperties(System.getProperties());
}

@Override
public void configFromProperties(Properties properties) {
String property = properties.getProperty("druid.mysql.usePingMethod");
if ("true".equals(property)) {
setUsePingMethod(true);
} else if ("false".equals(property)) {
setUsePingMethod(false);
}
}

public boolean isUsePingMethod() {
return usePingMethod;
}

public void setUsePingMethod(boolean usePingMethod) {
this.usePingMethod = usePingMethod;
}

public boolean isValidConnection(Connection conn, String validateQuery, int validationQueryTimeout) {
try {
if (conn.isClosed()) {
return false;
}
} catch (SQLException ex) {
// skip
return false;
}

if (usePingMethod) {
if (conn instanceof DruidPooledConnection) {
conn = ((DruidPooledConnection) conn).getConnection();
}

if (conn instanceof ConnectionProxy) {
conn = ((ConnectionProxy) conn).getRawObject();
}

if (clazz.isAssignableFrom(conn.getClass())) {
if (validationQueryTimeout < 0) {
validationQueryTimeout = DEFAULT_VALIDATION_QUERY_TIMEOUT;
}

try {
ping.invoke(conn, true, validationQueryTimeout);
return true;
} catch (InvocationTargetException e) {
Throwable cause = e.getCause();
if (cause instanceof SQLException) {
return false;
}

LOG.warn("Unexpected error in ping", e);
return false;
} catch (Exception e) {
LOG.warn("Unexpected error in ping", e);
return false;
}
}
}

Statement stmt = null;
ResultSet rs = null;
try {
stmt = conn.createStatement();
if (validationQueryTimeout > 0) {
stmt.setQueryTimeout(validationQueryTimeout);
}
rs = stmt.executeQuery(validateQuery);
return true;
} catch (SQLException e) {
return false;
} catch (Exception e) {
LOG.warn("Unexpected error in ping", e);
return false;
} finally {
JdbcUtils.close(rs);
JdbcUtils.close(stmt);
}

}

}

3.2 1.0.26版本

再翻看代码，发现1.0.26版本中也是有MySqlValidConnectionChecker啊，为什么没用上呢？原来是方法名改了，没重载上=。=

/*
* Copyright 1999-2101 Alibaba Group Holding Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.alibaba.druid.pool.vendor;

import java.io.Serializable;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;

import com.alibaba.druid.pool.DruidPooledConnection;
import com.alibaba.druid.pool.ValidConnectionChecker;
import com.alibaba.druid.pool.ValidConnectionCheckerAdapter;
import com.alibaba.druid.proxy.jdbc.ConnectionProxy;
import com.alibaba.druid.support.logging.Log;
import com.alibaba.druid.support.logging.LogFactory;
import com.alibaba.druid.util.JdbcUtils;
import com.alibaba.druid.util.Utils;

public class MySqlValidConnectionChecker extends ValidConnectionCheckerAdapter implements ValidConnectionChecker, Serializable {

public static final int DEFAULT_VALIDATION_QUERY_TIMEOUT = 1000;

private static final long serialVersionUID = 1L;
private static final Log LOG = LogFactory.getLog(MySqlValidConnectionChecker.class);

private Class<?> clazz;
private Method ping;
private boolean usePingMethod = false;

public MySqlValidConnectionChecker(){
try {
clazz = Utils.loadClass("com.mysql.jdbc.MySQLConnection");
if (clazz == null) {
clazz = Utils.loadClass("com.mysql.cj.jdbc.ConnectionImpl");
}

if (clazz != null) {
ping = clazz.getMethod("pingInternal", boolean.class, int.class);
}

if (ping != null) {
usePingMethod = true;
}
} catch (Exception e) {
LOG.warn("Cannot resolve com.mysql.jdbc.Connection.ping method. Will use 'SELECT 1' instead.", e);
}

configFromProperties(System.getProperties());
}

@Override
public void configFromProperties(Properties properties) {
String property = properties.getProperty("druid.mysql.usePingMethod");
if ("true".equals(property)) {
setUsePingMethod(true);
} else if ("false".equals(property)) {
setUsePingMethod(false);
}
}

public boolean isUsePingMethod() {
return usePingMethod;
}

public void setUsePingMethod(boolean usePingMethod) {
this.usePingMethod = usePingMethod;
}

public boolean validConnection(Connection conn, String validateQuery, int validationQueryTimeout) throws Exception {
if (conn.isClosed()) {
return false;
}

if (usePingMethod) {
if (conn instanceof DruidPooledConnection) {
conn = ((DruidPooledConnection) conn).getConnection();
}

if (conn instanceof ConnectionProxy) {
conn = ((ConnectionProxy) conn).getRawObject();
}

if (clazz.isAssignableFrom(conn.getClass())) {
if (validationQueryTimeout < 0) {
validationQueryTimeout = DEFAULT_VALIDATION_QUERY_TIMEOUT;
}

ping.invoke(conn, true, validationQueryTimeout * 1000);
return true;
}
}

Statement stmt = null;
ResultSet rs = null;
try {
stmt = conn.createStatement();
if (validationQueryTimeout > 0) {
stmt.setQueryTimeout(validationQueryTimeout);
}
rs = stmt.executeQuery(validateQuery);
return true;
} finally {
JdbcUtils.close(rs);
JdbcUtils.close(stmt);
}

}

}
往前看了几个版本，发现从1.0.21版本就是这样了。

目前还没有理解这么做的原因是什么，是因为mysql版本太多，这个功能不通用？还是当时开发的时候名字改错了？

提了个issue，等大大们回复了。

————————————————————————————————————————————

最新进展：大大们已经修复了，更新到1.0.27版本即可。
---------------------
作者：_tsubasa_
来源：CSDN
原文：https://blog.csdn.net/mj158518/article/details/53091064
版权声明：本文为博主原创文章，转载请附上博文链接！

【转】druid 版本bug导致discard connection问题记录

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