MySQL log error log

28.3　 Error log

MySQL Is recorded in the error log of MySQL All error messages during operation , see MySQL The error log of can help database maintainers to better troubleshoot MySQL Server failure .

28.3.1　 Open error log

Can be in my.cnf Documents or my.ini The error log function is configured in the file .

---

[mysqld]log_error = /data/mysql/log/error_log/mysql-error.log

---

among ,log_error Indicates the location of the error log file . If not for log_error assignment , be MySQL The default will be DATADIR Specified directory （MySQL Data storage directory ） Next create a host_name.err File to record MySQL Error log for .

After successful configuration , It needs to be reopened MySQL The server will take effect .

Be careful ：MySQL Does not support the MySQL The command line executes the following command to start the error log .

---

mysql> SET GLOBAL log_error = '/data/mysql/log/error_log/mysql-error.log';ERROR 1238 (HY000): Variable 'log_error' is a read only variable

---

Restart MySQL After the server , see /data/mysql/log/error_log A file in a directory .

---

[[email protected] ~]# ll /data/mysql/log/error_log/total 4-rw-r----- 1 mysql mysql 354 Jan 17 14:22 mysql-error.log

---

Results show ,data/mysql/log/error_log The directory has been successfully generated mysql-error.log file .

28.3.2　 Check the error log

MySQL The error log file of is stored on the disk of the server in the format of plain text file , You can directly view the contents of the file .

（1） towards t_goods_category Insert data into the data table , And make SQL Statement error .

---

mysql> INSERT INTO t_goods_category    -> (id, t_category)    -> VALUES    -> ('mysql', 'mysql');ERROR 1366 (HY000): Incorrect integer value: 'mysql' for column 'id' at row 1

---

（2） see MySQL Error log file .

---

cat /data/mysql/log/error_log/ mysql-error.log################ Omit n Line logs #######################2020-01-17T07:02:53.958135Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.112020-01-17T07:02:53.959012Z 0 [Note] InnoDB: Number of pools: 12020-01-17T07:02:53.960377Z 0 [Note] InnoDB: Not using CPU crc32 instructions2020-01-17T07:02:53.966535Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M2020-01-17T07:02:53.977288Z 0 [Note] InnoDB: Completed initialization of buffer pool2020-01-17T07:02:54.060328Z 0 [Note] InnoDB: Highest supported file format is Barracuda.2020-01-17T07:02:56.286598Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.2020-01-17T07:02:56.287290Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.2020-01-17T07:02:56.288285Z 0 [Note] InnoDB: Waiting for purge to start

---

28.3.3　 Delete error log

MySQL The error log of can also be deleted directly like the query log and slow query log , If you need to regenerate the log file , It's in MySQL Command line execution FLUSH LOGS command , Execute on the server command line mysqladmin flush-logs command .

（1） Delete error log .

---

rm -rf /data/mysql/log/error_log/mysql-error.log

---

see /data/mysql/log/error_log/ A file in a directory .

---

[[email protected] ~]# ll /data/mysql/log/error_log/total 0

---

Results show ,mysql-error.log The file has been deleted .

（2） Refresh log file .

---

mysql> FLUSH LOGS;         Query OK, 0 rows affected (0.01 sec)

---

Or execute the following command on the server command line to refresh the log .

---

[[email protected] ~]# mysqladmin -uroot -p flush-logsEnter password:

---

Look again /data/mysql/log/error_log/ A file in a directory .

---

[[email protected] ~]# ll /data/mysql/log/error_log/total 4-rw-r----- 1 mysql mysql 354 Jan 17 15:18 mysql-error.log

---

After refreshing the log ,MySQL The error log file will be regenerated .

28.3.4　 Close the error log

close MySQL Error log for , Only need to my.cnf Documents or my.ini In the document log_error Configuration Item Deletion , And turn it back on MySQL that will do . Readers can practice by themselves , No more details here .