mysql运维之服务器日志
mysql运维之服务器日志。（east_sun参考文档）
目录
- mysql运维之服务器日志east_sun参考文档
- 目录
- 日志分类概要
- 1 服务器日志之服务器错误日志error_log
- 2 服务器日志之慢查询日志log_slow
- 2 服务器日志之慢查询日志log_slow
- 3 服务器日志通用查询日志general_log
日志分类概要：
MySQL日志类型分为1.服务器日志（server_log）和2.事务日志（transaction_log）。其中在实际运维中，经常使用的服器日志有：服务器错误日志，慢查询日志和综合查询日志。事务日志经常使用的是：存储引擎事务日志，二进制日志。
1.1 服务器日志之服务器错误日志(error_log)
服务器错误日志主要记录MySQL运行过程中的Error、Warning、Note等信息，系统出错或者某条记录出问题可以查看Error日志。
mysql> SHOW GLOBAL VARIABLES LIKE 'log_error' ;＃＃此句SQL出了服务器错误日志的具体位置：
+---------------+----------------------------------------+
| Variable_name | Value |
+---------------+----------------------------------------+
| log_error | /usr/local/mysql/data/mysqld.local.err |
+---------------+----------------------------------------+然后进入log_error文件less读内容，可以看到Error、Warning、Note等信息，需要强调一点， log_error里面不斗全是错误信息，同时用户使用记录实例启动中重要信息和配置参数log_error文档信息。 当DBA遇到无法启动mysql时候，需要第一时间想到查看log_error。
1.2 服务器日志之慢查询日志（log_slow）：
服务器日志分类下日志的慢日志查询主要用途是用来记录在MySQL中响应时间超过阀值的语句，具体指运行时间超过long_query_time设置值，默认值为10秒,同时可以这个参数是精确到微秒（microseconds）。MySQL官方文档中(https://dev.mysql.com/doc/refman/5.7/en/slow-query-log.html)， 慢查询日志解释主要如下：
The slow query log consists of SQL statements that took more than long_query_time seconds to execute and required at least min_examined_row_limit rows to be examined. The minimum and default values of long_query_time are 0 and 10, respectively. The value can be specified to a resolution of microseconds. For logging to a file, times are written including the microseconds part. For logging to tables, only integer times are written; the microseconds part is ignored.
下面记录下自己常用的慢查询日志操作：
mysql> SHOW GLOBAL VARIABLES LIKE '%slow%'; ##查看slow_log相关日志
+---------------------------+--------------------------------------------------------+
| Variable_name | Value |
+---------------------------+--------------------------------------------------------+
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| slow_launch_time | 2 |
| slow_query_log | OFF |
| slow_query_log_file | /usr/local/mysql/data/louhaomiaodeMacBook-Pro-slow.log |
+---------------------------+--------------------------------------------------------+
5 rows in set (0.00 sec)
mysql> SET GLOBAL slow_query_log = 1 ; ##开启错误日志查询功能（默认一般关闭）
Query OK, 0 rows affected (0.02 sec)
mysql> SHOW GLOBAL VARIABLES LIKE '%slow%'; ##查看slow_log相关日志
+---------------------------+--------------------------------------------------------+
| Variable_name | Value |
+---------------------------+--------------------------------------------------------+
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | /usr/local/mysql/data/louhaomiaodeMacBook-Pro-slow.log |
+---------------------------+--------------------------------------------------------+
5 rows in set (0.01 sec)
mysql> SHOW GLOBAL VARIABLES LIKE'%long%'; ##默认为十秒
+----------------------------------------------------------+-----------+
| Variable_name | Value |
+----------------------------------------------------------+-----------+
| long_query_time | 10.000000 |
| performance_schema_events_stages_history_long_size | 1000 |
| performance_schema_events_statements_history_long_size | 1000 |
| performance_schema_events_transactions_history_long_size | 1000 |
| performance_schema_events_waits_history_long_size | 1000 |
+----------------------------------------------------------+-----------+
5 rows in set (0.00 sec)
mysql> SET GLOBAL long_query_time = 5 ;##一般线上业务设为五秒。
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW GLOBAL VARIABLES LIKE'%long%';
+----------------------------------------------------------+----------+
| Variable_name | Value |
+----------------------------------------------------------+----------+
| long_query_time | 5.000000 |
| performance_schema_events_stages_history_long_size | 1000 |
| performance_schema_events_statements_history_long_size | 1000 |
| performance_schema_events_transactions_history_long_size | 1000 |
| performance_schema_events_waits_history_long_size | 1000 |
+----------------------------------------------------------+----------+
5 rows in set (0.01 sec)
1.2 服务器日志之慢查询日志（log_slow）：
服务器日志分类下日志的慢日志查询主要用途是用来记录在MySQL中响应时间超过阀值的语句，具体指运行时间超过long_query_time设置值，默认值为10秒,同时可以这个参数是精确到微秒（microseconds）。MySQL官方文档中(https://dev.mysql.com/doc/refman/5.7/en/slow-query-log.html)， 慢查询日志解释主要如下：
The slow query log consists of SQL statements that took more than long_query_time seconds to execute and required at least min_examined_row_limit rows to be examined. The minimum and default values of long_query_time are 0 and 10, respectively. The value can be specified to a resolution of microseconds. For logging to a file, times are written including the microseconds part. For logging to tables, only integer times are written; the microseconds part is ignored.
下面记录下自己常用的慢查询日志操作：
mysql> SHOW GLOBAL VARIABLES LIKE '%slow%'; ##查看slow_log相关日志
+---------------------------+--------------------------------------------------------+
| Variable_name | Value |
+---------------------------+--------------------------------------------------------+
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| slow_launch_time | 2 |
| slow_query_log | OFF |
| slow_query_log_file | /usr/local/mysql/data/louhaomiaodeMacBook-Pro-slow.log |
+---------------------------+--------------------------------------------------------+
5 rows in set (0.00 sec)
mysql> SET GLOBAL slow_query_log = 1 ; ##开启错误日志查询功能（默认一般关闭）
Query OK, 0 rows affected (0.02 sec)
mysql> SHOW GLOBAL VARIABLES LIKE '%slow%'; ##查看slow_log相关日志
+---------------------------+--------------------------------------------------------+
| Variable_name | Value |
+---------------------------+--------------------------------------------------------+
| log_slow_admin_statements | OFF |
| log_slow_slave_statements | OFF |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | /usr/local/mysql/data/louhaomiaodeMacBook-Pro-slow.log |
+---------------------------+--------------------------------------------------------+
5 rows in set (0.01 sec)
mysql> SHOW GLOBAL VARIABLES LIKE'%long%'; ##默认为十秒
+----------------------------------------------------------+-----------+
| Variable_name | Value |
+----------------------------------------------------------+-----------+
| long_query_time | 10.000000 |
| performance_schema_events_stages_history_long_size | 1000 |
| performance_schema_events_statements_history_long_size | 1000 |
| performance_schema_events_transactions_history_long_size | 1000 |
| performance_schema_events_waits_history_long_size | 1000 |
+----------------------------------------------------------+-----------+
5 rows in set (0.00 sec)
mysql> SET GLOBAL long_query_time = 5 ;##一般线上业务设为五秒。
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW GLOBAL VARIABLES LIKE'%long%';
+----------------------------------------------------------+----------+
| Variable_name | Value |
+----------------------------------------------------------+----------+
| long_query_time | 5.000000 |
| performance_schema_events_stages_history_long_size | 1000 |
| performance_schema_events_statements_history_long_size | 1000 |
| performance_schema_events_transactions_history_long_size | 1000 |
| performance_schema_events_waits_history_long_size | 1000 |
+----------------------------------------------------------+----------+
5 rows in set (0.01 sec)
1.3 服务器日志通用查询日志（general_log）：
简单的说，通用查询日志就是纪录一切，英文慢日志解释如下：
The general query log is a general record of what mysqld is doing. The server writes information to this log when clients connect or disconnect, and it logs each SQL statement received from clients. The general query log can be very useful when you suspect an error in a client and want to know exactly what the client sent to mysqld.
所以根据解释：我们可以猜测到，通用查询是非常占用系统资源的一个日志，所以一般建议关闭。
通过SQL语句SHOW GLOBAL VARIABLES LIKE'%general%';
找到general_log。如果SET GLOBAL general_log = 'ON';然后MySQL就会记录一切客户的查询和写入的记录。