stats brainteaser

[Hauke Lampe]

Todd wrote:

> Yesterday I needed to flush the cache on a number of my servers, and I
> saw a big spike in queries recorded by the server in the "success"
> category. The spike was about 40% more than the usual traffic.

After a cache flush, the server has to re-fetch glue and nameserver
records from the root up to the target names. This can cause a
noticeable spike on a busy resolver. The statistics count these
"internal" queries, too.

> So, my mental exercise is this ... does BIND not record a cache hit as
> a success?

It does, AFAIK. If it was a success and not a cached negative response
or other.

> Assuming my clients are doing say, 1000queries/second, and all 1000
> are cache hits, do they show up as a success?

They do, but so do successfully resolved cache misses.

The number of cache hits is approximately
("responses sent") - ("queries caused recursion")

Approximately, because the value includes answers from local
authoritative zones, FORMERRs and other responses that did not come from
the cache.



Hauke.


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