[Dnsmasq-discuss] Any plans on adding ability to store cachetodisk?

[Timothy Madden]

Nicholas Weaver wrote:

>>> gypsy wrote:
>>>
>>>> If Simon is offended, then so be it, but I mean no offense. I just fail
>>>> to see how a save to/restore from disk could bloat the code;
>>>> save/restore IS a basic feature. TTL will expire out any crap
>>>> naturally.
>>>> --
>>>> gypsy
> 
> Speaking as just a general DNS guy (I'm not a DNSMasq developer):  Saving
> cache state is stupid.
> 
> TTL dictates a MAXIMUM that data can remain in the cache, but doesn't
> dictate a minimum, as any "minimum" could be enforced on the authority
> side by simply ensuring that the answer is consistent.
> 
> The savings is also trivial:  It only saves one RTT to the recursive
> resolver per lookup, since the recursive resolver should still have the
> item in its cache.  And this should be a short RTT: if your ISP doesn't
> have the recursive resolver within 30-40ms of your system, its either a
> high latency link overall (in which case amdahl's law ensures that the RTT
> for DNS lookups are still going to be irrelevant).

Exactly why should the recursive resolver have the site in its cache for the 
entire TTL of the site name ?

And if it happens not to have it, a new lookup costs about 2 seconds in my 
case.

Timothy Madden