fastzolver is a very fast Asynchronous DNS resolver for Webalizer.
The Webalizer is a web logfile analysis program written by Bradley Barrett, and it's widely used to produce statistics about website traffic. It is highly customizable and very fast.
It includes facilities for reporting IP-to-name DNS translations, but it's a terribly slow and inefficient process. Even the inclusion of webazolver, a preprocessor which does nothing but populate a name cache via multiple child processes, is impacted badly in the face of an unreachable nameserver. These are very common.
Our own website sees relatively little traffic, but log processing still took much too long, and it was clear that DNS inverse lookups were the hangup. So we studied how The Webalizer used the cache and wrote our own program using asynchronous DNS. It's dramatically faster and more efficient.
On a dual-processor 500MHz Linux machine, fastzolver was able to achieve more than 100 resolution per second when run in unlimited queries mode (though this ought not be typical, as it's very hard on a nameserver). This runs in a single thread.
Most DNS lookups are synchronous, which means that the requesting process blocks until a response is received or a timeout occurs. These timeouts are typically fairly long - 30 seconds or one minute - and absolutely nothing is done by the requesting process during this time.
When inverse DNS servers respond immediately, a series of lookups can proceed rapidly, but it doesn't take many unreachable servers before runtime shoots up dramatically. This can be ameliorated somewhat with multiple child processes, but this requires a lot of coordination but still suffers from the waiting-for-reply hangs.
Requirements:
· a C++ compiler
· GNU make
· the ADNS library
· the Berkeley DB library
· ZLIB(optional)
Product's homepage
Requirements:
· a C compiler
· GNU make
· the ADNS library
· the Berkeley DB library
· ZLIB(optional)
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