[rbldnsd] question of efficiency

[Michael Tokarev]

Jeff Chan wrote:
> On Sunday, January 23, 2005, 7:34:58 PM, Robin Frank wrote:
> 
>>Has anyone ever tested the relative efficiency of and rbldnsd zone of
>>say 100,000 entries versus a postfix access map in a mysqld databse?
> 
>>If not, can anyone hazard a guess?
> 
> IIRC rbldnsd is based on a much leaner database than mysql, so
> it ought to be faster.  The queries are extremely straightforward
> too so should be trivial to optimize in ways a more general
> database can't.

Well, that's (good) theory.  In practice, there are many other
levels involved - you also forget about caching resolver sitting
in between rbldnsd and clients, latency and whatnot.  The answer
is - it really depends.

I implemented rbldnsd mostly to work in real dnsbl environment,
when I saw problems popular dnsbls where having some years ago,
especially constant instabilities happening at osirusoft.com.
For this sort of environment, rbldnsd just isn't comparable to
any other solution.  But, for client-side "caching" of a dnsbl,
other solutions works too.  For example, one of DSBL.org
nameservers currently processes 4K requests per second, peaking
at 6K.  I'm sure this machine (it's 600MHz celeron) can do more.
But for typical (and I really mean typical - there are other
cases exists too) mailserver, there will be less queries than
that.  I think any postfix-useable map can be used here just
fine (well.. maybe except of regex/pcre and cidr -- both aren't
optimized for large number of entries and are searched
sequentially).

Usage of rbldnsd in "client environment" is mostly about convenience
than anything else, IMHO (you just grab the data in ready to use
format and be done with it), and maybe scalability -- (re)loading
external, constantly changing data to eg mysql may be a real problem,
but that's convenience again.  If you use your own {block}list,
using mysql may be more suitable because of easier maintenance.

YMMV ofcourse.  The main point here is not about efficiency IMHO,
but about easy/simplicity of use.

/mjt