resolv.conf question

[Jim Reid]

>>>>> "Ralf" == Ralf Hildebrandt <Ralf.Hildebrandt at innominate.de> writes:

    Ralf> I know that the servers given in /etc/resolv.conf are
    Ralf> queried in the order they're listed there. If the first
    Ralf> server fails, we get a timeout and the second server is
    Ralf> tried and so on.

    Ralf> My question: Is there any way to automatically reorder the
    Ralf> server in such a way, that query time is optimal?

No. And even if there were, few applications would be able to exploit
it. Most applications make 1 DNS request - maybe repeated to 2 or 3
name servers - and then don't do another DNS lookup after they've got
the answer. So keeping track of the round trip times would be
pointless for most things that use the DNS. The rotate option in the
BIND8 resolver might help a little, but only for the handful of
applications which make lots of DNS lookups. And even then this only
round-robins queries between the three nameserver directives, so the
bad name server(s) still get queried.

    Ralf> Reason: We had several customers complaining about bad
    Ralf> performance, and one of the main resons was that the
    Ralf> nameservers in their /etc/resolv.conf's were not answering
    Ralf> their machine's queries.

Why not get those customers to set up their resolvers to point at
reliable name servers? That would be the simplest and most obvious
solution. It seems a bit silly to fire DNS lookups at name servers
that don't respond.