Hi, there,
Because your clients lock up on particular IP
address, there is no other way, than to make that
address available "no matter what".
Two obvious choices are (a) local cache-only DNS
on 127.0.0.1 and (b) redundant DNS, HA style.
You can also try (if your applications will honor
/etc/nsswitch.conf) an /etc/hosts file with a list
of your remote hosts, if it is a limited list.
/etc/hosts size does not really matters anymore,
as it will be cached by nscd. I have seen 3000+
entries /etc/hosts running without problem.
On Mon, 9 Jun 2003, Dave Belfer-Shevett wrote:
>
> Hi all - good question for BBLISA folks.
>
> We have a large cluster of machiens that have 3 DNS servers available to
> them. (sdm[123]). We run applications on the cluster that are 'startup &
> run' type of services.
>
> The problem is that these applications seem to start, check
> /etc/resolv.conf, pick a nameserver, and stick to it. If the nameserver
> it attaches to (the first one on the list probably) goes down (either
> named dying or the machine rebooting), all the applications wedge with
> failed lookups.
>
> We need a stronger failover mechanism for these clusters - how do folks
> handle this sort of situation?
>
> One thing that has been proposed is using a localized 'caching only' named
> configuration on each of the servers, with a list of 'upstream' servers
> (sdm[123]) to consult if the cache doesn't have the answer.
>
> I've thought about round-robin DNS for the nameservers - but does
> libresolv actually handle that appropriately? Eg, if I call libresolv to
> do a nametoaddress lookup, and we say 'use sdm for resolution', will it
> keep poking whatever IP 'sdm' is for the answer?
>
> How do folks handle fault-tolerant nameservice inside high availability
> clusters?
>
> (btw - these are all Sun machines, running Solaris 7 or higher)
>
> --
> ------------------.--------.
> Dave Belfer-Shevett\ KB1FWR \
> www.homeport.org >--------`------------------------------------
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