MySQL 需要很长时间(数小时)来确定丢失的连接

Question

我们有一项服务可以在同一个单独的服务器上访问几个数据库。服务宕机了，但是 mysql 并没有中止所有的连接，而是让一个连接打开了很长时间。下面是一个mysql日志。我们可以根据连接 ID 看到，最后一行报告的连接应该在 00:01 与其他连接一起中止，但它停留了 2 个多小时。

110216  0:00:01 [Warning] Aborted connection 11864307 to db: 'foodb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865442 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864559 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11863856 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865445 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864581 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865447 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864566 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865451 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865446 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865444 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864565 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865490 to db: 'foodb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864251 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864299 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864303 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865486 to db: 'foodb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864304 to db: 'foodb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864560 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11864268 to db: 'foodb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865055 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865443 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:01 [Warning] Aborted connection 11865450 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:02 [Warning] Aborted connection 11865448 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  0:00:02 [Warning] Aborted connection 11865485 to db: 'foodb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)
110216  2:11:17 [Warning] Aborted connection 11865449 to db: 'bardb' user: 'db_user' host: '10.234.1.15' (Got an error reading communication packets)

现在，假设这是 mysql 的问题，给定以下超时设置，是否有任何可能导致此问题的原因？

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                 | 0                 |
| innodb_lock_wait_timeout   | 600               |
| innodb_rollback_on_timeout | OFF               |
| interactive_timeout        | 28800             |
| lc_time_names              | en_US             |
| long_query_time            | 5                 |
| net_read_timeout           | 30                |
| net_write_timeout          | 60                |
| slave_net_timeout          | 3600              |
| slow_launch_time           | 2                 |
| system_time_zone           | GMT               |
| table_lock_wait_timeout    | 50                |
| time_format                | %H:%i:%s          |
| time_zone                  | SYSTEM            |
| timed_mutexes              | OFF               |
| wait_timeout               | 28800             |
+----------------------------+-------------------+

mysql> show variables like '%packet%';
+--------------------+----------+
| Variable_name      | Value    |
+--------------------+----------+
| max_allowed_packet | 16777216 |
+--------------------+----------+

Answer 1

您的 max_allowed_size 必须默认为 1M，并且您是否使用大量数据、blob 或其他内容进行了一些查询。将该值增加到 8M(1GB 是最大限制)。

将 wait_timeout 减少到 50 左右。

wait_timeout 是 “服务器在关闭非交互式连接之前等待事件的秒数。此超时仅适用于 TCP/IP 和 Unix 套接字文件连接，不适用于使用命名管道建立的连接，或共享内存。” Details