Some settings such as ulimit -n (open-files-limit) cannot be done from inside 
the daemon.

Most other daemons fork themselves so the same mechanism for restarting is 
built in anyway. 

A signal 11 is always a bug, not normal or acceptable. So I trust you reported 
the backtraces from the errorlog?

Regards,
Arjen. 




-------- Original message --------
From: Russell Coker <[email protected]> 
Date: 08/11/2013  17:07  (GMT+10:00) 
To: [email protected] 
Subject: mysqld_safe seems unsafe 
 
It's always a sign of low code quality when a daemon has a wrapper script to 
restart it when it crashes.  Squid used to have such a script but for many 
years has been considered to be reliable enough not to need it.

MySQL seems to be the only commonly used daemon with such a script.  I had 
been wondering if the script was even needed, I would have hoped that mysqld 
was reliable many years ago.  But I checked the logs of a RHEL4 system I run 
and found 19 log messages about mysqld getting signal 11 since 2006 of which 
the last one was 4 days ago.

One problem with such scripts seems to be the issue of reliably shutting down 
the server.  I have a ZFS system that doesn't always mount the filesystems on 
boot so I use /etc/rc.local to restart mysqld.  That usually works apart from 
the time when I ended up with two copies of mysqld running at once.  However 
mysqld uses file locking and it seems that you don't get data loss when you 
have two copies of it running at the same time (try not to test this theory on 
production networks).

While it was handy that mysqld was restarted 19 times, it wasn't good that I 
was unaware of the problems.

Is that script being used in the MySQL successors such as Drizzle?

-- 
My Main Blog         http://etbe.coker.com.au/
My Documents Blog    http://doc.coker.com.au/
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