[CentOS] tinydns/djbdns opinion poll

[Bill Campbell]

On Thu, Feb 12, 2009, Ian Forde wrote:
>On Thu, 2009-02-12 at 11:08 -0600, Les Mikesell wrote:
>> That sounds like the kiss of death for any critical service.  Can't it 
>> figure out ahead of time that this is going to happen and let the 
>> service keep running unchanged with a warning message about needing the 
>> update instead?
>
>You're missing the point.  If the service is already running, the
>changes won't take effect until you restart the service with the new
>binaries. And the whole patching exercise is what maintenance windows
>are for, anyway.  Note that it's critical SERVICE, not critical SERVER.
>The former is more important than the latter, so ideally you should be
>able to take down the latter in order to upgrade one implementation of
>the former.

I understand the distinction very well.  In the time we have been using
this method, we have never taken down a service for any significant period
of time (the services are restarted on installation by the RPM SPEC files'
%pre, %post processing).

Of course we don't do things that are likely to take a critical service
down without proper prior planning (often found out the hard way on our own
systems :-).  If an update is likely to have an impact on operations, it is
scheduled during a maintenance window.

The services that are most frequently updated are clamav, spamassassin, and
amavisd-new, and we have often done this on heavily loaded MX servers
(millions of e-mails a day) without having a service down for more than a
minute or two while dealing with configuration file changes.

Bill
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