>(round robin or randomly selected)
ASSP is smarter - it knows how fast the DNS-servers are answering and uses
the fastest first. If a name server can't be reached - it is removed from
the querylist for some time.
As long as the nameserver order is not changed, it tries to use permanent
sockets. Because DNS-queries are also done by many other Perl modules
(Mail::SPF for example), it redirects there calls to its own DNS-engine
instead using the default Perl DNS implementation.
>would be a more standard implementation of DNS queries
What a standard - what RFC? Not the OS, the applications makes the rules.
Each app may handle DNS queries different. By the way, the Net::DNS module
in Perl works the same way.
ASSP V2 is designed to be as fast as possible - it has not the time to
wait for slow DNS-servers.
As an ASSP admin you have to know, that assp will produce up to 100 DNS
queries for a single mail (depends on the enabled features and there
configuration).
So if your assp handles 100.000 mails a day, the used DNS-Servers must be
able to answer 10.000.000 queries a day (but at least 1.000.000 !)
An day has 86400 seconds and the default DNS-Timeout is two seconds - I
think the numbers are selfexplaining.
Thomas
Von: K Post <nntp.p...@gmail.com>
An: ASSP development mailing list <assp-test@lists.sourceforge.net>
Datum: 21.05.2015 06:05
Betreff: Re: [Assp-test] More MX and A record lookup issues
I ask if it's normal because I don't (or didn't know). It's illogical to
me that it does, so I find the question perfectly reasonable.
I assumed that we'd want ASSP to try one of the DNS servers at a time,
especially if we're using internal DNS servers. If for some reason that
selected DNS server (round robin or randomly selected) times out, remove
it
from the rotation for a while so it's not a source of constant delay, and
try the next dns server. ASSP shouldn't be using internal dns servers
that
aren't reliable. I specify multiple just so that a single point of
failure
doesn't bring down ASSP.
Querying one at a time would allow multiple DNS servers listed for backup
purposes only without increasing the DNS query load unnecessarily* I
would think that would be a more standard implementation of DNS queries in
general. Isn't that the way Windows and Linux workstations and servers
operate normally? If you've got 3 dns servers in windows and do a dns
lookup, it asks one server (as far as I understand it). If that times
out,
it moves on to the next. I can't say that I've ever seen (or noticed) a
server querying every DNS server it is assigned to use with the same query
every time.
*I say "unecessarily" becuase >>I<< don't think it's necessary, but if
I'm off base on this concept I'd love to understand why.
Anyway, I'm glad that my incessant questions keep finding these minor yet
potentially impactful bugs that your continually able to diagnose and fix
-
and quickly. Thanks so much for that.
On Wed, May 20, 2015 at 10:34 AM, Thomas Eckardt
<thomas.ecka...@thockar.com
> wrote:
> >is it normal for each query
> to ask each server??
>
> You should be able to answer this question yourself!!!
>
> Yes - what else makes sense?
>
> The logic is: query all-> wait - use the first result - repeat all if
> failed. - max time = DNSTimeout * DNSretry
>
> Otherwise it would be: query the first NS -> wait for result (NO-result)
> -> query next NS -> wait .... Next....Next ... LAST -> repeat all if
> failed - max time = DNSTimeout * Nameserver * DNSretry
>
> But I found a BUG in assp. Because DNS uses UDP the order of the answers
> of a DNS server must not be the same like the order of the queries, if
> multiple queries are done using the same socket.
> This is currently not expected by assp - it ignores the DNS header-ID,
if
> the DNS sockets are reused. The next build will fix this.
>
> Thomas
>
>
>
> Von: K Post <nntp.p...@gmail.com>
> An: ASSP development mailing list <assp-test@lists.sourceforge.net>
> Datum: 19.05.2015 23:19
> Betreff: Re: [Assp-test] More MX and A record lookup issues
>
>
>
> Thomas, I'll disable the reuse socket option. is it normal for each
query
> to ask each server??
>
> The self loader was removed a long time ago.
>
> On Tue, May 19, 2015 at 5:16 PM, K Post <nntp.p...@gmail.com> wrote:
>
> > Thanks for the question Bob, but nope, they're straight WIndows 2012
R2
> > DNS servers. no dnsmasq.
> >
> > On Tue, May 19, 2015 at 1:08 PM, Robert K Coffman Jr. -Info From Data
> > Corp. <bcoff...@infofromdata.com> wrote:
> >
> >>
> >> > May-19-15 11:41:26 Info: sent DNS query for '_dmarc.my.orbitz.com'
> type
> >> > 'TXT' to nameserver 172.23.0.52
> >> > May-19-15 11:41:26 Info: reuse DNS socket for 172.23.0.53
> >>
> >> By any chance, are you running DNSMASQ on your DNS servers?
> >>
> >> - Bob
> >>
> >>
> >>
> >>
>
>
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