From: Dan Nelson
Date: May 19 2011 2:27pm
Subject: Re: Interesting bug/oversight
List-Archive: http://lists.mysql.com/mysql/225043
Message-Id: <20110519142703.GE34082@dan.emsphone.com>
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In the last episode (May 19), Johan De Meersman said:
> I use DNS names instead of IPs in mysql grants. Yes, I'm aware of the
> performance impact, that's not an issue.
> 
> I just found out through failing logins that a server was still connecting
> to an old DNS server, and properly updated the resolv.conf.  Commandline
> host lookups then returned correct results.
> 
> However, even after repeated flush hosts commands, the MySQL kept
> returning wrong results.  Only after a full restart did it pick itself up
> and start doing proper lookups.  I strongly suspect that this is due to it
> internally caching the nameserver, too, and not refreshing that along with
> the host cache on a flush hosts command.
> 
> Can anyone confirm this is the case, and wether or not a bug has been
> logged about it?  I can't seem to find one.

I doubt that mysql calls anything other than gethostbyname() or
getaddrinfo(), so your behaviour is probably dependant on whatever OS you
are running and how often its local resolver re-checks resolv.conf.  Usually
that's only once when a program starts.  If you're running bind, nscd, or
some other intermediate DNS client on your machine, bouncing that should
work.  If not, you'll need to bounce mysql.

-- 
	Dan Nelson
	dnelson@stripped