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:
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ERROR 2013 (HY000): Lost connection to MySQL server during query
ERROR 2006 (HY000): MySQL server has gone away
No connection . Trying to reconnect...
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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
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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.
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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
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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
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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
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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)
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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
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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)
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开启另外一个mysql客户端,查看会话变量的值
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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)
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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
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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));
}
}
}
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结果输出如下:
INTERACTIVE_TIMEOUT: 10
WAIT_TIMEOUT: 28800
只修改全局变量wait_timeout的值
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mysql> select variable_name,variable_value from information_schema.global_variables where variable_name in ( 'interactive_timeout' , 'wa
it_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' , 'wa
it_timeout' );+ ---------------------+----------------+
| variable_name | variable_value |
+ ---------------------+----------------+
| INTERACTIVE_TIMEOUT | 28800 |
| WAIT_TIMEOUT | 20 |
+ ---------------------+----------------+
2 rows in set (0.00 sec)
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开启另外一个mysql客户端,查看会话变量的值
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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)
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WAIT_TIMEOUT的值依旧是28800.
查看jdbc的结果
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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));
}
}
}
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查看jdbc的结果
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INTERACTIVE_TIMEOUT: 28800
WAIT_TIMEOUT: 20
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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 failure
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Last 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
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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
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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)
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以上所述是小编给大家介绍的MySQL中interactive_timeout和wait_timeout的区别,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持!
原文链接:http://www.cnblogs.com/ivictor/archive/2016/10/20/5979731.html