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MySQL之wait_timeout和interactive_timeout参数

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文章目录
  1. 引言
  2. 相关参数
  3. 控制连接最大空闲时长的参数及验证
  4. 会话变量wait_timeout的继承问题
  5. 总结
  6. 参考
  7. 更多内容请关注公众号

引言

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 away
No 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,连接的时长是多长?如何确认和配置?

相关参数

引言中连接时长和参数interactive_timeout和wait_timeout的设置有关。

1. interactive_timeout参数定义

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.

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。

默认值:28800,单位秒,即8个小时

2. wait_timeout参数定义

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.

服务器关闭非交互连接之前等待活动的秒数。在线程启动时,根据全局wait_timeout值或全局interactive_timeout值初始化会话wait_timeout值,取决于客户端类型(由mysql_real_connect()的连接选项CLIENT_INTERACTIVE定义)。

默认值:28800,单位秒,即8个小时

控制连接最大空闲时长的参数及验证

控制连接最大空闲时长的参数是: wait_timeout

验证: 1. 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          |
+---------------------+----------------+
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。

验证: 2. 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          |
+---------------------+----------------+
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          |
+---------------------+----------------+
rows in set (0.06 sec)

可以看到,等待10s后再执行操作,连接没有断开。

会话变量wait_timeout的继承问题

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1: 只修改全局变量interactive_timeout的值

1. 交互式连接修改INTERACTIVE_TIMEOUT值
* 打开一个Mysql客户端修改INTERACTIVE_TIMEOUT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          |
+---------------------+----------------+
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          |
+---------------------+----------------+
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             |
+---------------------+----------------+
rows in set (0.00 sec)

WAIT_TIMEOUT的值已经变为10,继承INTERACTIVE_TIMEOUT的值。

2. 非交互式连接修改INTERACTIVE_TIMEOUT值

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));
}
}
}

输出结果

INTERACTIVE_TIMEOUT:  10
WAIT_TIMEOUT:  28800

wait_timeout的值依旧是28800,没有继承INTERACTIVE_TIMEOUT的值

验证2: 只修改全局变量wait_timeout的值

1. 交互式连接修改wait_timeout值
* 打开一个Mysql客户端修改wait_timeout值

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          |
+---------------------+----------------+
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             |
+---------------------+----------------+
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          |
+---------------------+----------------+
rows in set (0.03 sec)

wait_timeout的值依旧是28800,没有继承刚才设置的WAIT_TIMEOUT值

2. 非交互式连接修改wait_timeout值

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));
}
}
}

输出结果

INTERACTIVE_TIMEOUT:  28800
WAIT_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 failure
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

wait_timeout的变为20,继承刚才设置的WAIT_TIMEOUT值

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             |
+----+------+----------------------+------+---------+------+-------+------------------+
rows in set (0.03 sec)

参考

  • https://www.cnblogs.com/ivictor/p/5979731.html
  • http://www.cnblogs.com/Alight/p/4118515.html
  • http://www.cnblogs.com/jiunadianshi/articles/2475475.html

更多内容请关注公众号


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