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During the MySQL Troubleshooting webinar series, I covered many monitoring and logging tools such as:

• General, slow, audit, binary, error log files
• Performance Schema
• Information Schema
• System …

This blog post will discuss how to use the MySQL super_read_only system variable.

It is well known that replica servers in a master/slave configuration, to avoid breaking replication due to duplicate keys, missing rows or other similar issues, should not receive write queries. It’s a good practice to set

read_only=1

 on slave servers to prevent any (accidental) writes. Servers acting as replicas will NOT be in read-only mode automatically by default.

Sadly, 

read_only

 has an historical issue: users with the SUPER privilege can override the setting and could still run DML queries. Since Percona Server 5.6.21 and MySQL 5.7.8, however, you can use the

super_read_only

 feature to extend the

read_only