本篇文章為大家展示了MySQL中怎么設(shè)置查詢超時(shí)，內(nèi)容簡(jiǎn)明扼要并且容易理解，絕對(duì)能使你眼前一亮，通過這篇文章的詳細(xì)介紹希望你能有所收獲。

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為了優(yōu)化OceanBase的query timeout設(shè)置方式，特調(diào)研MySQL關(guān)于timeout的處理，記錄如下。
[plain]
mysql> show variables like '%time%';
+----------------------------+-------------------+
| Variable_name              | Value             |
+----------------------------+-------------------+
| connect_timeout            | 10                |
| datetime_format            | %Y-%m-%d %H:%i:%s |
| delayed_insert_timeout     | 300               |
| flush_time                 | 1800              |
| innodb_lock_wait_timeout   | 50                |
| innodb_old_blocks_time     | 0                 |
| innodb_rollback_on_timeout | OFF               |
| interactive_timeout        | 28800             |
| lc_time_names              | en_US             |
| lock_wait_timeout          | 31536000          |
| long_query_time            | 10.000000         |
| net_read_timeout           | 30                |
| net_write_timeout          | 60                |
| slave_net_timeout          | 3600              |
| slow_launch_time           | 2                 |
| system_time_zone           |                   |
| time_format                | %H:%i:%s          |
| time_zone                  | SYSTEM            |
| timed_mutexes              | OFF               |
| timestamp                  | 1366027807        |
| wait_timeout               | 28800             |
+----------------------------+-------------------+
21 rows in set, 1 warning (0.00 sec)
重點(diǎn)解釋其中幾個(gè)參數(shù)：
connect_timeout:
The number of seconds that the mysqld server waits for a connect packet before respondingwith Bad handshake. The default value is 10 seconds as of MySQL 5.1.23 and 5 seconds before that.  Increasing the connect_timeout value might help if clients frequently encounter errors of the form Lost connection to MySQL server at ‘XXX’, system error: errno.
解釋：在獲取鏈接時(shí)，等待握手的超時(shí)時(shí)間，只在登錄時(shí)有效，登錄成功這個(gè)參數(shù)就不管事了。主要是為了防止網(wǎng)絡(luò)不佳時(shí)應(yīng)用重連導(dǎo)致連接數(shù)漲太快，一般默認(rèn)即可。
interactive_timeout:
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.
解釋：一個(gè)持續(xù)SLEEP狀態(tài)的線程多久被關(guān)閉。線程每次被使用都會(huì)被喚醒為acrivity狀態(tài)，執(zhí)行完Query后成為interactive狀態(tài)，重新開始計(jì)時(shí)。wait_timeout不同在于只作用于TCP/IP和Socket鏈接的線程，意義是一樣的。
MySQL可以配置連接的超時(shí)時(shí)間，這個(gè)時(shí)間如果做得太長(zhǎng)，甚至到了10min，那么很可能發(fā)生這種情況，3000個(gè)鏈接都被占滿而且sleep在哪，新鏈接進(jìn)不來，導(dǎo)致無(wú)法正常服務(wù)。因此這個(gè)配置盡量配置一個(gè)符合邏輯的值，60s或者120s等等。
說人話：
命令行下面敲一個(gè)命令后，直至下一個(gè)命令到來之前的時(shí)間間隔為interactive_time，如果這個(gè)時(shí)間間隔超過了 interactive_timeout，則連接會(huì)被自動(dòng)斷開，下一個(gè)命令失敗。不過一般的mysql客戶端都有自動(dòng)重連機(jī)制，下一個(gè)命令會(huì)在重連后執(zhí) 行。
[sql]
mysql> set interactive_timeout = 1;
Query OK, 0 rows affected (0.00 sec)
mysql> show session variables like '%timeout%';
+----------------------------+----------+
| Variable_name              | Value    |
+----------------------------+----------+
| connect_timeout            | 10       |
| interactive_timeout        | 1        |
| wait_timeout               | 28800    |
+----------------------------+----------+
10 rows in set (0.00 sec)
=====
[sql]
mysql> set wait_timeout = 1;
Query OK, 0 rows affected (0.00 sec)
【去泡杯茶，等會(huì)兒】
mysql> show session variables like '%timeout%';
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    7
Current database: *** NONE ***
+----------------------------+----------+
| Variable_name              | Value    |
+----------------------------+----------+
| connect_timeout            | 10       |
| interactive_timeout        | 28800    |
| wait_timeout               | 28800    |
+----------------------------+----------+
10 rows in set (0.01 sec)
wait_timeout:
The number of seconds the server waits for activity on a noninteractive connection (連接上沒有活動(dòng)命令，可能是客戶端喝咖啡去了。)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

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