Split out functionality that gathers system specs
[squirrelmail.git] / plugins / filters / bulkquery / README
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2bulkquery - A program by Brent Bice - 02/2002
3
4 Bulkquery is a multi-threaded program that makes a large number of
5DNS queries as fast as possible. It's tailored for making DNS queries for
6specific IP addresses against specific DNS based RBLs.
7
8 "Why bother?"
9I've been asked this several times. While running squirrelmail on a server
10with very little bandwidth and very high latency (a dial-up account - snicker)
11I noticed that while my filters plugin was making gethostbyname() function
12calls, my dial-up line was mostly idle. This was, apparently, because all
13the DNS function calls were being made in series. Once a DNS query had been
14sent, no others were sent until a response had been received or until a
15certain timeout period had occurred. And some of the RBLs were quite a
16bit faster than the others. This seemed pretty inefficient. "Why not make
17more DNS queries while waiting for the replies," I thought.
18
19 After several attempts to make a multi-threaded program to make the queries
20using the standard DNS library calls, I realized why. The library functions
21weren't thread-safe and most of the replies would be lost. Luckily, a
22friend of a friend told me about the lwres API in Bind 9.x and told me that
23IT was definitely thread-safe and very fast.
24
25 Boy was SHE right!
26
27 So, how much faster is it? It will depend on your bandwidth and the
28latency of your connection. But for those of us trying to make do with less,
29bulkquery is a LOT faster. On a dial-up connection, I can make queries
30anywhere from 6 to 10 times faster! On my T1 at work, the queries are
31usually between 2 and 7 times faster. The bottom line of all of this is
32that even on my T1 at work, the filters plugin can query ALL of the RBLs
33for all the new email in my INBOX in less than half the time it takes using
34the PHP gethostbyname() function calls.