[dns-operations] More Aggressive prefetch for popular names
phoffman at proper.com
Mon Apr 15 21:37:04 UTC 2019
On 15 Apr 2019, at 14:15, Peter van Dijk wrote:
> Hello Paul,
> On 11 Apr 2019, at 15:54, Paul Hoffman wrote:
>>> "only increasing the authoritative load in the less common cases."
>>> That's where it can get tricky. In theory, yes, but in practice it's
>>> hard to estimate the aggregate effects from such policy -- it may as
>>> well lead to some unintended collateral damage -- and IMO we need
>>> studies on this.
>> Fully agree. This could even be aided by some resolver developers
>> adding a debug feature.
> What would that debugging feature look like?
As a first guess:
In a cache dump or other way of getting resolver stats, you could report
the ratio of names that had a prefetch that have that data hit in the
cache before the TTL expires (0% bad, 100% best). For software that lets
the operator tune the prefetch, this ratio could help in the tuning. For
software that uses off/on setting, if that ratio is less than 50%, the
operator might consider turning off prefetching.
Actual operators of customer-facing resolvers (that's not me!) might
suggest here other debugging that might aid them in deciding how to tune
or turn off/on.
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