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前言：
MySQL中有两个关于连接超时的配置项。他们之间在某些条件下会互相继承，那究竟这两个参数会在什么情况下起作用呢？
本文将会通过一些测试实例来证明总结两者的相互关系。
参数介绍：
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 alsowait_timeout.
The number of seconds the server waits for activity on a noninteractive connection before closing it. Before MySQL 5.1.41, this timeout applies only to TCP/IP connections, not to connections made through Unix socket files, named pipes, or shared memory.
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_INTERACTIVEconnect option to mysql_real_connect()). See also interactive_timeout.
CLIENT_INTERACTIVE
Permit interactive_timeout seconds (instead of wait_timeout seconds) of inactivity before closing the connection. The client's sessionwait_timeout variable is set to the value of the session interactive_timeout variable.
简单的说 interactive就是交互式的终端，例如在shell里面直接执行mysql，出现 mysql> 后就是交互式的连接。而mysql -e 'select 1' 这样的直接返回结果的方式就是非交互式的连接。
第二部分 测试
2.1 继承关系
Q：通过Socket连接 timeout会从哪个global timeout继承
A：由下例可见，通过socket登录，timeout 继承于global.interactive_timeout;
mysql> set global interactive_timeout = 11111;
Query OK, 0 rows affected (0.00 sec)
mysql> set global wait_timeout = 22222;
Query OK, 0 rows affected (0.00 sec)
mysql> show global variables like '%timeout%';
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| connect_timeout | 10 |
| delayed_insert_timeout | 300 |
| innodb_lock_wait_timeout | 50 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 11111 |
| lock_wait_timeout | 31536000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| wait_timeout | 22222 |
+----------------------------+----------+
10 rows in set (0.00 sec)
mysql -uroot -ppassword -S /usr/local/mysql3310/mysql.sock
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.5.16-log MySQL Community Server (GPL)
Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show session variables like '%timeout%';
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| connect_timeout | 10 |
| delayed_insert_timeout | 300 |
| innodb_lock_wait_timeout | 50 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 11111 |
| lock_wait_timeout | 31536000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| wait_timeout | 11111 |
+----------------------------+----------+
10 rows in set (0.00 sec)
Q：通过TCP/IP client 连接， timeout会从哪个global timeout继承
A：由下例可见，通过TCP/IP client 连接后的wait_timeout 仍然继承于 global.interactive_timeout
mysql -uroot -ppassword -h 127.0.0.1 --port 3310 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 6 Server version: 5.5.16-log MySQL Community Server (GPL) Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> show session variables like '%timeout%'; +----------------------------+----------+ | Variable_name | Value | +----------------------------+----------+ | connect_timeout | 10 | | delayed_insert_timeout | 300 | | innodb_lock_wait_timeout | 50 | | innodb_rollback_on_timeout | OFF | | interactive_timeout | 11111 | | lock_wait_timeout | 31536000 | | net_read_timeout | 30 | | net_write_timeout | 60 | | slave_net_timeout | 3600 | | wait_timeout | 11111 | +----------------------------+----------+ 10 rows in set (0.00 sec)
2.2 起效关系
Q：timeout值，对于正在运行用的语句是否起效？
A：由下例可见SQL正在执行状态的等待时间不计入timeout时间
mysql> set session wait_timeout=10; Query OK, 0 rows affected (0.00 sec) mysql> set session interactive_timeout=10; Query OK, 0 rows affected (0.00 sec) mysql> select 1,sleep(20) from dual; +---+-----------+ | 1 | sleep(20) | +---+-----------+ | 1 | 0 | +---+-----------+ 1 row in set (20.00 sec) mysql> mysql> show session variables like '%timeout%'; +----------------------------+----------+ | Variable_name | Value | +----------------------------+----------+ | connect_timeout | 10 | | delayed_insert_timeout | 300 | | innodb_lock_wait_timeout | 50 | | innodb_rollback_on_timeout | OFF | | interactive_timeout | 10 | | lock_wait_timeout | 31536000 | | net_read_timeout | 30 | | net_write_timeout | 60 | | slave_net_timeout | 3600 | | wait_timeout | 10 | +----------------------------+----------+
Q：wait_timeout 和 interacitve_timeout 如何相互作用。
A：只有session.wait_timeout 会起效
mysql> set session interactive_timeout=10; Query OK, 0 rows affected (0.00 sec) mysql> set session wait_timeout=20; Query OK, 0 rows affected (0.00 sec) ---------------------another connection------------------------- mysql> show full processlist; +----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read | +----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | 1 | system user | | NULL | Connect | 103749 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL | 0 | 0 | 1 | | 2 | system user | | NULL | Connect | 103750 | Connecting to master | NULL | 0 | 0 | 1 | | 3 | root | localhost | NULL | Query | 0 | NULL | show full processlist | 0 | 0 | 11 | | 10 | root | localhost:58946 | NULL | Sleep | 20 | | NULL | 0 | 0 | 11 | +----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ 4 rows in set (0.00 sec) mysql> show full processlist; +----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read | +----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | 1 | system user | | NULL | Connect | 103749 | Slave has read all relay log; waiting for the slave I/O thread to update it | NULL | 0 | 0 | 1 | | 2 | system user | | NULL | Connect | 103750 | Connecting to master | NULL | 0 | 0 | 1 | | 3 | root | localhost | NULL | Query | 0 | NULL | show full processlist | 0 | 0 | 11 | +----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ 3 rows in set (0.00 sec)
Q：global timeout和session timeout哪个起作用。
A：只有session timeout 会起作用。
测试1：
mysql> set session interactive_timeout = 10;
Query OK, 0 rows affected (0.00 sec)
mysql> set session wait_timeout = 10;
Query OK, 0 rows affected (0.00 sec)
mysql> show session variables like '%timeout%';
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| interactive_timeout | 10 |
| wait_timeout | 10 |
+----------------------------+----------+
10 rows in set (0.00 sec)
mysql> show global variables like '%timeout%';
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| interactive_timeout | 20 |
| wait_timeout | 20 |
+----------------------------+----------+
10 rows in set (0.00 sec)
mysql> show full processlist;
+----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+
| 3 | root | localhost | NULL | Query | 0 | NULL | show full processlist | 0 | 0 | 11 |
| 17 | root | localhost:60585 | NULL | Sleep | 10 | | NULL | 10 | 10 | 11 |
+----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+
2 rows in set (0.00 sec)
mysql> show full processlist;
+----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+
| Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read |
+----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+
| 3 | root | localhost | NULL | Query | 0 | NULL | show full processlist | 0 | 0 | 11 |
+----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+
1 rows in set (0.00 sec)
测试2：
mysql> show session variables like '%timeout%'; +----------------------------+----------+ | Variable_name | Value | +----------------------------+----------+ | interactive_timeout | 20 | | wait_timeout | 20 | +----------------------------+----------+ 10 rows in set (0.00 sec) mysql> show global variables like '%timeout%'; +----------------------------+----------+ | Variable_name | Value | +----------------------------+----------+ | interactive_timeout | 10 |
| wait_timeout | 10 | +----------------------------+----------+ 10 rows in set (0.00 sec) mysql> show full processlist; +----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read | +----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | 3 | root | localhost | NULL | Query | 0 | NULL | show full processlist | 0 | 0 | 11 | | 19 | root | localhost:50276 | NULL | Sleep | 19 | | NULL | 10 | 10 | 11 | +----+-------------+-----------------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ 2 rows in set (0.00 sec) mysql> show full processlist; +----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | Rows_read | +----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ | 3 | root | localhost | NULL | Query | 0 | NULL | show full processlist | 0 | 0 | 11 | +----+-------------+-----------+------+---------+--------+-----------------------------------------------------------------------------+-----------------------+-----------+---------------+-----------+ 1 rows in set (0.00 sec)
第三部分 总结
由以上的阶段测试可以获得以下结论。
1. 超时时间只对非活动状态的connection进行计算。
2. 超时时间指通过 session wait_timeout 起效。
3. 交互式连接的wait_timeout 继承于 global.interactive_timeout
非交互式连接的wait_timeout 继承于 global.wait_timeout
4. 继承关系和超时对 TCP/IP 和 Socket 连接均有效果