"reasonable" bulk resolver behavior
barmar at alum.mit.edu
Thu Jan 13 02:30:56 UTC 2005
In article <cs4f7l$1844$1 at sf1.isc.org>,
Steve Friedl <steve at unixwiz.net> wrote:
> Hello all,
> I've written a bulk IP rDNS resolver program that runs through Apache
> logs and populates a DB file with IP->name lookups that are later used
> by webalizer for webserver logfile analysis. It uses the ADNS library to
> make async calls (in a single thread) to burn through reverse lookups as
> fast as the network can take it: there could be 200 outstanding queries
> at a time, for instance.
> It strikes me that maxing out the nameserver is not terribly polite
> behavior, so there is a throttle mechanism: limit to <N> outstanding
> queries at a time, and pause a bit when we reach that number.
> How does one select a proper throttle point for a nameserver? I have
> no idea when the query rate becomes "rude": can anybody offer some
> suggestions for what to look for when picking this number?
It depends on how powerful and busy the nameserver you're querying is.
If you're running your own nameserver and it doesn't have lots of other
clients, you may be able to go full out; if you're querying your ISP's
nameserver, you'll probably have to throttle down quite a bit.
Barry Margolin, barmar at alum.mit.edu
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