mysql异常占用资源排查
作者：L-960
本文详细介绍了通过MySQL的全局变量检查日志状态,监控连接数及启用和调整慢查询记录,以帮助排查数据库性能问题,感兴趣的可以了解一下
通过执行日志与连接信息排查
查看是否开启日志记录
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
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
mysql> show global variables like '%general%'; +------------------+---------------+ | Variable_name | Value | +------------------+---------------+ | general_log | ON | | general_log_file | localhost.log | +------------------+---------------+
查看当前连接数
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
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
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
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
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：
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：
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：
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
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
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)
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