SERVFAIL debugging

[JINMEI Tatuya / 神明達哉]

At Wed, 24 Jun 2009 10:13:51 +0400,
Dmitry Rybin <kirgudu at corbina.net> wrote:

> >>>>> new experimental feature just for that purpose:
> >>>> Is this feature going to be back ported to 9.4 and 9.5 releases as well?
> >>> For 9.5, yes.  For 9.4, not according to the current plan.
> >> named[87071]: 22-Jun-2009 13:18:23.256 query-errors: debug 2: fetch 
> >> completed at resolver.c:6569 for static.cache.l.google.com/A in 
> >> 0.041364: SERVFAIL/success 
> >> [domain:com,referral:1,restart:0,qrysent:0,timeout:0,lame:0,neterr:0,badresp:0,adberr:0,findfail:0,valfail:0]
> > 
> > Which version of BIND9 is this?  To match the line number we need the
> > exact version number.

> FreeBSD 7.2-STABLE, bind from ports bind96-9.6.1

Okay, then the above log strongly suggests that the cache is full in
some unusual way and even recently fetched RR (which is in this case
NS for google.com) has been purged before it's actually used.

There have been bugs that could cause this symptom, but all known
problems should have been solved in 9.6.1.  So, I have no specific
idea about how exactly that happened.

Can you provide the following information?
- your complete named.conf
- if you enable statistics-channel, its output when you see this
  trouble
- the result of rndc dump when you see this trouble (note: rndc dump
  purges stale cache entries as a side effect and may hide the cause.
  It will still help investigate the problem)

If you think it's sensitive please contact me offlist.

Thanks,

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.