MySQL中interactive_timeout和wait_timeout的区别（https://www.cnblogs.com/ivictor/p/5979731.html）

在用mysql客户端对数据库进行操作时，打开终端窗口，如果一段时间没有操作，再次操作时，常常会报如下错误：

ERROR 2013 (HY000): Lost connection to MySQL server during query

ERROR 2006 (HY000): MySQL server has gone awayNo connection. Trying to reconnect...

 

这个报错信息就意味着当前的连接已经断开，需要重新建立连接。

 

那么，连接的时长是如何确认的？

其实，这个与interactive_timeout和wait_timeout的设置有关。

 

首先，看看官方文档对于这两个参数的定义

interactive_timeout

默认是28800，单位秒，即8个小时

The number of seconds the server waits for activity on an interactive connection before closing it. An interactive client is defined as a client that uses the CLIENT_INTERACTIVE option to mysql_real_connect(). See also wait_timeout.

 

wait_timeout

默认同样是28800s

The number of seconds the server waits for activity on a noninteractive connection before closing it.On thread startup, the session wait_timeout value is initialized from the global wait_timeout value or from the global interactive_timeout value, depending on the type of client (as defined by the CLIENT_INTERACTIVE connect option to mysql_real_connect()). See also interactive_timeout.

 

根据上述定义，两者的区别显而易见

1> interactive_timeout针对交互式连接，wait_timeout针对非交互式连接。所谓的交互式连接，即在mysql_real_connect()函数中使用了CLIENT_INTERACTIVE选项。

     说得直白一点，通过mysql客户端连接数据库是交互式连接，通过jdbc连接数据库是非交互式连接。 

2> 在连接启动的时候，根据连接的类型，来确认会话变量wait_timeout的值是继承于全局变量wait_timeout，还是interactive_timeout。

 

下面来测试一下，确认如下问题

1. 控制连接最大空闲时长的是哪个参数。

2. 会话变量wait_timeout的继承问题

 

Q1：控制连接最大空闲时长的是哪个参数

A1：wait_timeout

验证

只修改wait_timeout参数

mysql> select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout');+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 28800          || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.03 sec)mysql> set session WAIT_TIMEOUT=10;Query OK, 0 rows affected (0.00 sec)-------等待10s后再执行mysql> select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout');ERROR 2013 (HY000): Lost connection to MySQL server during query

可以看到，等待10s后再执行操作，连接已经断开。

 

只修改interactive_timeout参数

mysql> select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout');+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 28800          || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.06 sec)mysql> set session INTERACTIVE_TIMEOUT=10;Query OK, 0 rows affected (0.00 sec)
----------等待10s后执行mysql> select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout');+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 10             || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.06 sec)

 

Q2：会话变量wait_timeout的继承问题

A2：如果是交互式连接，则继承全局变量interactive_timeout的值，如果是非交互式连接，则继承全局变量wait_timeout的值。

验证：

只修改全局变量interactive_timeout的值

mysql> select variable_name,variable_value from information_schema.global_variables where variable_name in ('interactive_timeout','wait_timeout'); 
+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 28800          || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.13 sec)mysql> set global INTERACTIVE_TIMEOUT=10;Query OK, 0 rows affected (0.00 sec)mysql> select variable_name,variable_value from information_schema.global_variables where variable_name in ('interactive_timeout','wait_timeout');
+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 10             || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.00 sec)

 

开启另外一个mysql客户端，查看会话变量的值

mysql> select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout');
+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 10             || WAIT_TIMEOUT        | 10             |+---------------------+----------------+2 rows in set (0.00 sec)

发现，WAIT_TIMEOUT的值已经变为10了。

 

但通过jdbc测试，wait_timeout的值依旧是28800

public class Jdbc_test {    @SuppressWarnings("static-access")    public static void main(String[] args) throws Exception {         Connection conn = null;         Statement stmt = null;         ResultSet rs = null;         String url = "jdbc:mysql://192.168.244.10:3306/test";         String user = "root";         String password = "123456";         Class.forName("com.mysql.jdbc.Driver");         conn = DriverManager.getConnection(url, user, password);         stmt = conn.createStatement();         String sql = "select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout')";         rs = stmt.executeQuery(sql);         while (rs.next()) {             System.out                     .println(rs.getString(1)+":  "+rs.getString(2));         }    }}

结果输出如下：

INTERACTIVE_TIMEOUT:  10WAIT_TIMEOUT:  28800

 

 只修改全局变量wait_timeout的值

mysql> select variable_name,variable_value from information_schema.global_variables where variable_name in ('interactive_timeout','wait_timeout');+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 28800          || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.17 sec)mysql> set global WAIT_TIMEOUT=20;Query OK, 0 rows affected (0.07 sec)mysql> select variable_name,variable_value from information_schema.global_variables where variable_name in ('interactive_timeout','wait_timeout');+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 28800          || WAIT_TIMEOUT        | 20             |+---------------------+----------------+2 rows in set (0.00 sec)

 

开启另外一个mysql客户端，查看会话变量的值

mysql> select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout');+---------------------+----------------+| variable_name       | variable_value |+---------------------+----------------+| INTERACTIVE_TIMEOUT | 28800          || WAIT_TIMEOUT        | 28800          |+---------------------+----------------+2 rows in set (0.03 sec)

WAIT_TIMEOUT的值依旧是28800.

 

查看jdbc的结果

public class Jdbc_test {    @SuppressWarnings("static-access")    public static void main(String[] args) throws Exception {         Connection conn = null;         Statement stmt = null;         ResultSet rs = null;         String url = "jdbc:mysql://192.168.244.10:3306/test";         String user = "root";         String password = "123456";         Class.forName("com.mysql.jdbc.Driver");         conn = DriverManager.getConnection(url, user, password);         stmt = conn.createStatement();         String sql = "select variable_name,variable_value from information_schema.session_variables where variable_name in ('interactive_timeout','wait_timeout')";         rs = stmt.executeQuery(sql);         while (rs.next()) {             System.out                     .println(rs.getString(1)+":  "+rs.getString(2));         }         Thread.currentThread().sleep(21000);         sql = "select 1 from dual";         rs = stmt.executeQuery(sql);         while (rs.next()) {             System.out                     .println(rs.getInt(1));         }    }}

查看jdbc的结果

INTERACTIVE_TIMEOUT:  28800WAIT_TIMEOUT:  20

同时，新增了一段程序，等待20s后，再次执行查询，报如下错误：

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureLast packet sent to the server was 12 ms ago.    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)    at java.lang.reflect.Constructor.newInstance(Unknown Source)    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3009)    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2895)    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3438)    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1951)    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2101)    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2548)    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2477)    at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1422)    at com.victor_01.Jdbc_test.main(Jdbc_test.java:29)Caused by: java.net.SocketException: Software caused connection abort: recv failed    at java.net.SocketInputStream.socketRead0(Native Method)    at java.net.SocketInputStream.socketRead(Unknown Source)    at java.net.SocketInputStream.read(Unknown Source)    at java.net.SocketInputStream.read(Unknown Source)    at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)    at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)    at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)    at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2452)    at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2906)    ... 8 more

 

总结

1. 控制连接最大空闲时长的wait_timeout参数。

2. 对于非交互式连接，类似于jdbc连接，wait_timeout的值继承自服务器端全局变量wait_timeout。

    对于交互式连接，类似于mysql客户单连接，wait_timeout的值继承自服务器端全局变量interactive_timeout。

3. 判断一个连接的空闲时间，可通过show processlist输出中Sleep状态的时间

mysql> show processlist;+----+------+----------------------+------+---------+------+-------+------------------+| Id | User | Host                 | db   | Command | Time | State | Info             |+----+------+----------------------+------+---------+------+-------+------------------+|  2 | root | localhost            | NULL | Query   |    0 | init  | show processlist ||  6 | repl | 192.168.244.20:44641 | NULL | Sleep   | 1154 |       | NULL             |+----+------+----------------------+------+---------+------+-------+------------------+2 rows in set (0.03 sec)

 

参考

1. http://www.cnblogs.com/cenalulu/archive/2012/06/20/2554863.html

2. http://www.cnblogs.com/Alight/p/4118515.html

3. http://ronaldbradford.com/blog/sqlstatehy000-general-error-2006-mysql-server-has-gone-away-2013-01-02/