dns.resolve only tries the first nameserver in /etc/resolv.conf??

[Yun Feng Ma]

Hi everyone!

The dns.resolve tries to send request to only the first nameserver in /etc/resolv.conf, and if the first nameserver fails to resolve the name, dns.resolve just returns and doesn't try to send request to the second nameserver.  Is this work-as-design?

Here is an example: the  /etc/resolv.conf is like below in Linux:

75.2.4.5

75.4.7.6

Run below codes:

dns.resolve('demo1.sample.com','A',function(err, addresses) {
        console.log(err);
        console.log(addresses);
});

The 'demo1.sample.com' is defined in the second nameserver (75.4.7.6), so the above codes always failed, because the dns.resolve doesn't try to call the second nameserver.

I found nodejs has flag to control this: https://github.com/nodejs/node/blob/master/deps/cares/src/ares_init.c#L255  seems like the default behaviour is only call the first nameserver, is there any way to make dns.resolve to call all nameservers in /etc/resolv.conf until succeed? 

Thanks a lot.

[Ben Noordhuis]

The second nameserver is only tried when the first one times out or
returns a malformed reply. If the first server replies with NXDOMAIN
(domain not found), the second one isn't contacted; that shouldn't be
necessary because DNS is a global registry after all.

[Yun Feng Ma]

在此输入代码...

在 2016年5月6日星期五 UTC+8上午9:43:50，Ben Noordhuis写道：

Thanks, Ben, for the reply.

In our environment, the first nameserver is our internal DNS server, which is used to resolve some internal domain names; the second nameserver is the public nameserver (like google DNS server 8.8.8.8), so this code  dns.resolve('www.google.com','A',function(err, addresses) { }) will get failed, because the first nameserver returns NXDOMAIN for "www.google.com". Do you have any solution for this?

Thanks.

[Matt]

Yes, make your internal nameserver also be recursive/caching and remove the second line. How you do that depends on what software you're using for DNS.

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[Alain Mouette]

What you are trying to do is against the rules. It will not work with any standard implementation!

Read more about DNS

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Alain Mouette

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[Denard Springle]

Set the internal DNS to proxy to an external DNS - such that when a DNS record is requested that the internal DNS does not have, it fetches it from an external name server (and caches it for future use). 

-- Denny

[Ben Noordhuis]

Not a node.js-based solution but is there a reason you can't configure
your internal nameserver to forward requests for names it doesn't know
about to an upstream server?

If that isn't a option, you could try installing dnsmasq locally and
see if you can make it do what you want.