MySql log monitoring: How to quickly detect and analyze MySQL errors and exceptions

With the advent of the Internet and big data era, MySQL database, as a commonly used open source database management system, is adopted by more and more companies and organizations. However, in the actual application process, various errors and exceptions may occur in the MySQL database, such as system crashes, query timeouts, deadlocks, etc. These anomalies will have a serious impact on system stability and data integrity. Therefore, quickly detecting and analyzing MySQL errors and anomalies is a very important task.

Log monitoring is one of the important functions of MySQL. By monitoring MySQL logs, MySQL errors and exceptions can be discovered and resolved in a timely manner. This article will introduce how to use MySQL's log monitoring function to quickly detect and analyze MySQL errors and exceptions.

1. MySQL log types

MySQL is divided into multiple types of logs. The following are several commonly used log types in MySQL:

1. Error log (error log): records error information generated by MySQL during operation, such as database failure to start, connection failure, etc. You can locate the problem by viewing the error log.
2. Binary log (binary log): records all MySQL data change operations, including INSERT, UPDATE, DELETE, etc., which can be used for data recovery and replication.
3. Slow query log (slow query log): records SQL statements whose MySQL execution time exceeds the specified time, which can be used to optimize query statements.
4. General query log (general query log): records all query operations of MySQL, including SELECT, SHOW, etc., and can be used for query operation auditing.
5. Relay log (relay log): used for MySQL master-slave replication, recording the process of the slave database updating the binary log of the master database to itself.

2. How to enable MySQL logs

In MySQL, the commonly used log types are error logs, binary logs and slow query logs. In order to enable these logs, you first need to modify the MySQL configuration file my.cnf (or my.ini, the specific file name may vary depending on the operating system), and add the following configuration items in the file:

1. Enable Error log:

[mysqld]
log-error=/var/log/mysql/error.log #Error log saving path

2. Enable binary log ：

[mysqld]
log-bin=/var/log/mysql/mysql-bin.log # Save path of binary log

3. Enable slow query Log:

[mysqld]
slow_query_log=ON # Enable slow query log
slow_query_log_file=/var/log/mysql/slow.log #Save path of slow query log
long_query_time=2 # Only queries that take more than 2 seconds will be recorded

After modifying the configuration file, you need to restart the MySQL service to make the modification effective:

$ sudo systemctl restart mysqld

3. How to read MySQL logs

1. Reading error logs

Reading error logs can be achieved directly by viewing the contents of the log file . For example, if the error log is saved in /var/log/mysql/error.log, you can use the cat command to view the contents of the log file:

$ sudo cat /var/log/mysql/error.log

2. Reading the binary log

Reading the binary log can be achieved using the MySQL command line tool mysqlbinlog. For example, if the binary log is saved in /var/log/mysql/mysql-bin.log, you can use the following command to view the contents of the log file:

$ mysqlbinlog /var/log/mysql/mysql- bin.log

3. Reading of slow query log

Reading of slow query log can be realized directly by viewing the content in the log file. For example, if the slow query log is saved in /var/log/mysql/slow.log, you can use the cat command to view the contents of the log file:

$ sudo cat /var/log/mysql/slow. log

4. How to monitor MySQL logs

In order to facilitate monitoring of MySQL logs, you can use some open source tools, such as pt-query-digest and mysqlbinlog. These tools can analyze and collect statistics on MySQL logs, helping us discover and solve MySQL errors and exceptions in a timely manner.

1. pt-query-digest

pt-query-digest is an open source MySQL query analysis tool that can analyze and collect statistics on MySQL's slow query logs. Use pt-query-digest to easily find inefficient query statements and optimize them.

An example of using pt-query-digest is as follows:

$ pt-query-digest /var/log/mysql/slow.log > /tmp/slow_query_report.txt

This command will analyze the /var/log/mysql/slow.log log file and output the analysis results to the /tmp/slow_query_report.txt file.

2. mysqlbinlog

mysqlbinlog is an open source MySQL binary log analysis tool that can analyze and process MySQL binary logs. Use mysqlbinlog to easily view data change operations, and perform data recovery and replication.

The example of using mysqlbinlog is as follows:

$ mysqlbinlog /var/log/mysql/mysql-bin.log > /tmp/binlog_report.sql

This command will Analyze the /var/log/mysql/mysql-bin.log log file and output the analysis results to the /tmp/binlog_report.sql file.

5. Summary

MySQL's log monitoring function is an important tool to ensure the normal operation of MySQL and ensure data security. By enabling MySQL logs and using open source tools for analysis and statistics, MySQL errors and exceptions can be quickly detected and analyzed, and maintenance and optimization can be carried out in a timely manner.

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