[Dnsmasq-discuss] Add address file option
Jan 'RedBully' Seiffert
redbully at cc.hs-owl.de
Fri Mar 5 17:16:15 GMT 2010
Simon Kelley schrieb:
>> 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
> 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
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
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...
Networking? That is for fishermen.
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