Hi Simon
Some answers inline sorry for the netiquette

Sent from my iPhone

> On 24 Nov 2017, at 17:56, Simon Kelley <si...@thekelleys.org.uk> wrote:
> 
> A couple of possible problems with this are as follows.
> 
> 1) It may not be possible to determine that the upstream server is not
> answering in a tinely manner. "Connection refused replies work, but
> don't arrive in many otherwise reasonable network config, and without
> those, you're relying on timeouts.
I think it is ok to fallback on timeouts and consider connection refused or 
NXDOMAIN as the primary time of failure. 
> 
> 2) Once you've determined that the upstream server is not answering,
> there's no guarantee that the record you need will be in the cache, even
> with a stale TTL. Cache entries can easily be evicted even before the
> end of the TTL by newer entries, as the system uses LRU cache
> replacment. I get the feeling that you want some guarantees, and this
> doesn't give that, just a lower probability of failure.
> 
You probably mean that cache eviction happens even if a query is not made and 
is probably made on a timer basis. If so, such a behavior for sure would 
require to handle cache eviction differently and probably at query time or at a 
max ttl value, 86400 for example.

> Cheers,
> 
> Simon.
> 
> 
>> On 23/11/17 14:02, Akram Ben Aissi wrote:
>> Hi all,
>> 
>> I would be interrested by the following feature:
>> 
>> In case we have a dns forward for a given domain and upstream dns server
>> is not available for this domain (connection refused on UDP port 53) , I
>> want TTL to be ignored (or countdown restarts to old TTL value or
>> to *min-cache-ttl*)   and still have the old record to be returned.
>> 
>> 
>> I am interrested in this feature to be used by our OpenShift
>> infrastructure in which we use dnsmasq to forward queries to our
>> internal skydns.
>> 
>> In case of skydns not being available, for example, in case of a major
>> crash, we still want dnsmasq to return old values, until skydns is back
>> again.
>> 
>> 
>> Any thhougths ?
>> 
>> Akram
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> _______________________________________________
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>> 
> 
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