mysql异常占用资源排查

通过执行日志与连接信息排查

查看是否开启日志记录

sql 复制代码

mysql> show global variables like '%general%';
+------------------+---------------+
| Variable_name    | Value         |
+------------------+---------------+
| general_log      | OFF           |
| general_log_file | localhost.log |
+------------------+---------------+
2 rows in set (0.03 sec)

开启sql记录

sql 复制代码

mysql> set global general_log=on;
Query OK, 0 rows affected (0.00 sec)

查看日志位置观察异常sql

sql 复制代码

mysql> show global variables like '%general%';
+------------------+---------------+
| Variable_name    | Value         |
+------------------+---------------+
| general_log      | ON            |
| general_log_file | localhost.log |
+------------------+---------------+

查看当前连接数

sql 复制代码

mysql> SHOW STATUS LIKE 'Threads_connected';
+-------------------+-------+
| Variable_name     | Value |
+-------------------+-------+
| Threads_connected | 2     |
+-------------------+-------+
1 row in set (0.04 sec)

查看哪些客户端连接到了mysql

sql 复制代码

mysql> SHOW PROCESSLIST;
+-------+-------------+----------------------+------------------+---------+------+--------------------------+------------------+----------+
| Id    | User        | Host                 | db               | Command | Time | State                    | Info             | Progress |
+-------+-------------+----------------------+------------------+---------+------+--------------------------+------------------+----------+
|     1 | system user |                      | NULL             | Daemon  | NULL | InnoDB purge worker      | NULL             |    0.000 |
|     2 | system user |                      | NULL             | Daemon  | NULL | InnoDB purge coordinator | NULL             |    0.000 |
|     3 | system user |                      | NULL             | Daemon  | NULL | InnoDB purge worker      | NULL             |    0.000 |
|     4 | system user |                      | NULL             | Daemon  | NULL | InnoDB purge worker      | NULL             |    0.000 |
|     5 | system user |                      | NULL             | Daemon  | NULL | InnoDB shutdown handler  | NULL             |    0.000 |
| 98821 | root        | 192.168.2.42:53790   | test_cloud       | Sleep   |    2 |                          | NULL             |    0.000 |
| 98824 | root        | 192.168.2.14:64112   | NULL             | Query   |    0 | Init                     | SHOW PROCESSLIST |    0.000 |
+-------+-------------+----------------------+------------------+---------+------+--------------------------+------------------+----------+
7 rows in set (0.05 sec)

通过慢sql信息排查

查看是否开启慢sql记录

sql 复制代码

mysql> show global variables like '%slow_query_log%';
+---------------------+--------------------+
| Variable_name       | Value              |
+---------------------+--------------------+
| slow_query_log      | OFF                |
| slow_query_log_file | localhost-slow.log |
+---------------------+--------------------+
2 rows in set (0.05 sec)

开启慢sql记录

sql 复制代码

mysql> set global slow_query_log=1;
Query OK, 0 rows affected (0.00 sec)

mysql> show global variables like '%slow_query_log%';
+---------------------+--------------------+
| Variable_name       | Value              |
+---------------------+--------------------+
| slow_query_log      | ON                 |
| slow_query_log_file | localhost-slow.log |
+---------------------+--------------------+
2 rows in set (0.05 sec)

关闭慢sql记录

sql 复制代码

mysql> set global slow_query_log=0;
Query OK, 0 rows affected (0.00 sec)

mysql> show global variables like '%slow_query_log%';
+---------------------+--------------------+
| Variable_name       | Value              |
+---------------------+--------------------+
| slow_query_log      | OFF                 |
| slow_query_log_file | localhost-slow.log |
+---------------------+--------------------+
2 rows in set (0.05 sec)

修改slow_launch_time与 long_query_time

slow_launch_time：定义一个客户端连接启动所花费的时间阈值。如果一个客户端连接的启动时间超过了这个阈值，MySQL 将认为这是一个慢连接启动，并将其记录到慢查询日志中。
long_query_time：定义一个 SQL 查询执行所花费的时间阈值。如果一个 SQL 查询的执行时间超过了这个阈值，MySQL 将认为这是一个慢查询，并将其记录到慢查询日志中。

这两个参数都可以在 MySQL 的配置文件中进行设置，通常在 my.cnf 或 my.ini 文件中定义。例如：

bash 复制代码

slow_launch_time = 2
long_query_time = 1

也可以通过sql进行查看和修改：

查看慢连接判定时间：

sql 复制代码

mysql> show variables like 'slow_launch_time%';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| slow_launch_time | 2     |
+------------------+-------+
1 row in set (0.04 sec)

修改慢连接判定时间：

sql 复制代码

mysql> set global slow_launch_time=3;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'slow_launch_time%';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| slow_launch_time | 3     |
+------------------+-------+
1 row in set (0.04 sec)

查看慢sql判定时间

sql 复制代码

mysql> show variables like 'long_query_time%';
+-----------------+-----------+
| Variable_name   | Value     |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+
1 row in set (0.05 sec)

修改慢sql判定时间

sql 复制代码

mysql> set long_query_time=3;
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like 'long_query_time%';
+-----------------+----------+
| Variable_name   | Value    |
+-----------------+----------+
| long_query_time | 3.000000 |
+-----------------+----------+
1 row in set (0.04 sec)