What does "deleted from unreachable cache" mean?

Cathy Almond cathya at isc.org
Fri Aug 3 08:13:50 UTC 2012

On 02/08/12 19:00, Michael Hoskins (michoski) wrote:
> -----Original Message-----
> From: Peter Olsson <pol at leissner.se>
> Date: Thursday, August 2, 2012 10:25 AM
> To: Cathy Almond <cathya at isc.org>
> Cc: "bind-users at lists.isc.org" <bind-users at lists.isc.org>
> Subject: Re: What does "deleted from unreachable cache" mean?
>> Excellent information, thanks!
> Agreed.  I really appreciate the effort ISC has put into the KB.
>> However, it is worrying that the master sometimes is unreachable.
>> Is there some way I can make the slave server log, with timestamp,
>> what zone it was trying to refresh when it failed?
> Not sure if you've already tried, but do you have xfer logging enabled?
> logging {
> <snip>
> 	channel audit_log {
> 		file "/var/named/bind/named.log";
> 		severity debug;
> 		print-time yes;
> 	};
> <snip>
> 	category xfer-in { audit_log; };
> 	category xfer-out { audit_log; };
> 	category notify { audit_log; };
> 	category network { audit_log; };
> 	category update { audit_log; };
> 	// might want this to debug...
> 	//category queries { audit_log; };
> };

The point at which the 'unreachable' entry is cached, is logged under
category 'xfer-in' - although it doesn't actually tell you that it's
caching it.  Look for messages containing text "failed to connect" or
"could not refresh".

Once the master is already in the unreachable cache, if the refresh code
checks and finds it there, then there are several messages (different
circumstances) that explain why a transfer isn't going to happen right
then - and these ones all incorporate the text "unreachable (cached)".

But yesterday, I dug further into the code that's reporting "deleted
from unreachable cache" and I'm sorry that I have to report that there
is a bug there - the code is matching the source of the notify
correctly, but may also mistakenly include and report on older cache
entries that are already "deleted".

We'll fix this.  It's being tracked as bug ticket #30501.

But if you have no evidence of ongoing problems (looking at what's
logged in category xfer-in - per my suggestions above) then you can
safely ignore these messages. There will have been an issue at some
point in the past, but which is now cleared.


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