[Dnsmasq-discuss] Add address file option

[Don Muller]

> -----Original Message-----
> From: dnsmasq-discuss-bounces at lists.thekelleys.org.uk [mailto:dnsmasq-
> discuss-bounces at lists.thekelleys.org.uk] On Behalf Of Jan 'RedBully'
> Seiffert
> Sent: Friday, March 05, 2010 12:16 PM
> To: dnsmasq-discuss at lists.thekelleys.org.uk
> Subject: Re: [Dnsmasq-discuss] Add address file option
> 
> Simon Kelley schrieb:
> [snip]
> >> I'd be rather more inclined to extend the DBus interface, which
> allows
> >>> dynamic setting of servers (but not source ports)
> >>>
> >>> I'm still bewildered why people are so allergic to restarting
> dnsmasq:
> >>> it takes almost no time, doesn't disrupt existing connections and
> the
> >>> only state lost is the cache, which is quickly and transparently
> >>> replaced.
> >>>
> > Can anybody answer this?
> >
> 
> I think its:
> Even if it's fast, it's not fast enough.
> If a query comes in exactly during this blib, it will fail and you have
> to deal
> with users which are not that firm with computers going "the internet
> is down".
> It's even enough that some other service may barf a little bit louder
> because
> one name query failed (dumb example: your mail server wants to resolve
> in that
> very moment, couldn't and now rejects the mail).
> And there is always the risk the new dnsmasq will not come up, because
> you made
> a silly typo in the config, or something like that. Depending on how
> fast you
> can rectify the situation, now you have a real window where you are
> without name
> resolution.

I agree. Many organizations, if they follow any kind of change or problem
management, will not allow a restart of DNS without the proper 'paperwork'
and they will probably never allow a restart during busy times. However a
refresh (or reload) is a different matter. That would probably be allowed
since it is a function of an already running task.

> If one can avoid that, he will avoid that.
> 
> To really make the "restart will be fine"-option workable, dnsmasq
> needs some
> kind of "continuous service"-feature. Which means: Implement a special
> take-over
> restart.
> The old dnsmasq gets signaled by a socket somewhere in /var/run that a
> new
> instance is starting, it will finish it's in flight actions, but not
> start new
> actions and than pass "important" fd's over the socket to the new
> dnsmasq
> instance when it signals "all systems go". This way no packet is lost
> and
> service is not disrupted by a restart.
> (And this doesn't work if the admin changes something on listen-
> address,
> interface, except-interface, bind-interfaces...)
> 
> And that is overkill for dnsmasq, you do something like that if you do
> not want
> to drop VoIP-calls or something like that, so back to the "avoid
> restart" scheme...

I think this is over kill.


> 
> > Cheers,
> >
> > Simon.
> >
> 
> Greetings
> 	Jan
> 
> --
> Networking? That is for fishermen.
> 
> _______________________________________________
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss