[collectd] Plugins for postfix, amavisd-new and powerdns

Luke Heberling collectd at c-ware.com
Tue Feb 19 20:11:36 CET 2008

Sebastian Harl wrote:
> Replying to your original post to this list, Alexander Wirt pointed you
> at amavisd-nanny, amavisd's bdb stats databases and some snmp agent (see
> <20071120090914.GC29338 at ned.snow-crash.org>). Did you have a look at
> that? Any well-defined interface is preferred to parsing logs. Sorry for
> the inconvenience.

Did you read my response at the time? I looked at the bdb database at 
least twice, once before I discovered collectd and was doing this with 
perl scripts updating rrd files on a cron job.  I wouldn't describe it 
as a well-defined interface.  In fact, if I wrote a plugin using the bdb 
on my version of amavis (debian stable: 2.4.2) then it would be broken 
with the newest release of amavis, which changed the bdb format 
incompatibly in april of last year (version 2.5.0 - see 
http://www.ijs.si/software/amavisd/release-notes.txt).  This apparently 
wasn't much of a problem however because as noted in the release notes, 
they just changed the nanny and agent to work with the new format.  The 
role of the bdb appears to be an internal implementation detail which 
can be changed to add features, counters and the like, or any other 
reason. Listed as "related software" on the project's home page 
(http://www.ijs.si/software/amavisd/#contrib) amongst nearly a dozen log 
parsers are exactly zero programs which use the bdb.

Bolstering my opinion that the amavis distribution endorses log parsing 
it the ease with which it can be done.  Take a look at the length of the 
amavis plugin and you'll see how really simple it is to parse their 
logs.  Even if they change the log format, unless they take a huge step 
backwards in structured format it will be very easy to follow suit.  I 
don't think that the same can be said of the bdb.

The snmp agent is slightly more appealing, but amavisd-agent is just a 
proof of concept that "displays snmp-like counters".  It doesn't listen 
to or answer queries from other programs.  Perhaps there are third party 
programs that do that which may work fine with the existing snmp 
collectd plugin, but they too would be burdened by keeping up with the 
bdb format.

In short, I find the bdb format to be at least as volatile as the log 
format, and I'd rather be in the same boat as a dozen other tools if the 
log format changes than on my own using the bdb stats.  But I have that 
regardless of whether you find a use for my plugin.  No reason to speak 
of inconvenience, my plugins have improved in quality thanks to your 
input and I will benefit from that as I continue to use them.

The powerdns plugin might still be of use to you.  It talks to powerdns 
over a socket, but the format of the question/answer could change 
incompatibly in a future version.


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