Some time ago, Peter Boros at Percona wrote this post: Rotating MySQL slow logs safely. It contains good info, such as that one should use the rename method for rotation (rather than copytruncate), and then connect to mysqld and issue a FLUSH LOGS (rather than send a SIGHUP signal).

So far so good. What I do not agree with is the additional construct to prevent slow queries from being written during log rotation. The author’s rationale is that if too many items get written while the rotation is in process, this can block threads. I understand this, but let’s review what actually happens.

Indeed, if one were to do lots of writes to the slow query log in a short space of time, a write could block while waiting.

Is the risk of this occurring greater during a logrotate operation? I doubt it. A FLUSH LOGS has to …

Did your logging stop working after you set up logrotate? Then this post might be for you.

Archive your log files!

Some time ago, Peter Boros wrote about Rotating MySQL Slow Logs safely, explaining the steps of a “best practice” log rotate/archive. This post will add more info about the topic.

When running logrotate for MySQL (after proper setting the /etc/logrotate.d/mysql conf file) from anacron, there’s a situation that you might potentially face if the user and password used to execute the “flush logs” command is stored in, for example, /root/.my.cnf file.

The situation:

You might find out that you have a new MySQL log file ready to receive data, but nothing is being written to it.

Why did this happen?

The logrotate script is executed, but the postrotate …

This blog post is part two of two. Like part one, published Wednesday, this is a cross-post from Groupon’s engineering blog. Thanks again to Kyle Oppenheim at Groupon. And one more reminder that I’ll be at the Percona Live MySQL Conference and Expo next week in Santa Clara, California so look for me there. You can checkout the sessions I’ll be leading here.

In my last post, I described a solution for keeping the caches of a MySQL standby server hot using MySQL slow logs with …