MySQL: Weird log message in the slow queries log

Question

I found in the slow queries log there are a bunch of these logs, what exactly does it mean? It looks like mysql is keep restarting itself? I'm using mysql 5.0.77. Any idea what might be causing this? Thanks!

/usr/libexec/mysqld, Version: 5.0.77-log (Source distribution). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
/usr/libexec/mysqld, Version: 5.0.77-log (Source distribution). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument
/usr/libexec/mysqld, Version: 5.0.77-log (Source distribution). started with:
Tcp port: 3306  Unix socket: /var/lib/mysql/mysql.sock
Time                 Id Command    Argument

Answer 1

This happens in two situations. Something executed a FLUSH LOGS statement which causes mysqld to close and reopen all logs, including the slow log.

Alternatively, something sent a SIGHUP signal to mysqld. This too causes mysqld to close and reopen logs. A SIGHUP is commonly sent by logrotate when it performs log rotation.

Answer 2

Most likely what is happening is that your log rotation process is asking mysql to start new logs, but it isn't actually rotating the slow query log to a new file. This could be because it is set to a minimum log size or just doesn't know about the file. The MySQL docs have some information about log rotation, but most distributions use a systemwide tool to handle all the rotation for all the different servers and logs at once. For instance, Debian uses logrotate which is configured with the list of mysql log files in /etc/logrotate.d/mysql-server