[mrtg] An awfully quiet list for the last 2 months ...

[Volk,Gregory B]

I have been working on modifying MRTG to send a copy of the time series data it collects to
Graphite (https://github.com/graphite-project) in addition to storing it in RRD files. I am
interested in doing this because I have a large, customized MRTG installation that collects
many metrics from many devices and it would be nice to work with that time series data via
one of the many Graphite front-ends such as Grafana (https://github.com/grafana/grafana)
without having to implement a whole new SNMP data collection system. With this in mind I
have modified mrtg 2.17.4 to use the Net::Graphite perl module
(http://search.cpan.org/~slanning/Net-Graphite-0.14/) to open a TCP socket to my Graphite
server on startup and send a copy of each collected metric and the associated timestamp to
Graphite after the calls to RRDs::update.

So far it works pretty well. The most difficult task was converting the relevant MRTG
config file directives (things like $$rcfg{'legendi'}{$router} and
$$rcfg{'legendo'}{$router}) into meaningful graphite name space values. This took some
experimentation because periods are graphite namespace delimiters, and spaces along with
other special characters are not allowed in the graphite namespace at all. In some cases I
had to go back and modify my custom MRTG cfg builder scripts and MRTG template files to not
use periods and special characters.

If anyone else is interested in trying it out you can download it from here:
http://mrtg.gvolk.com/mrtg-graphite.zip.
The zipfile contains these three files
mrtg-2.17.4-graphite    mrtg 2.17.4 with send-to-graphite modifications
mrtg-diff.txt                     diff against stock mrtg 2.17.4
README.txt                      this readme file


If you decide to try it out keep these things in mind...
-I strongly suggest using a graphite docker image unless you already have a
functioning graphite instance.
-The same can be said for Grafana - use the docker image if you are looking for a
fancier Graphite front end.
-You will need to modify line 92 of mrtg-2.17.4-graphite with your graphite server
name/ip unless you're running it on the same host as your mrtg poller.
-Ideally the graphite variable assignments in lines 90 - 101 should be cfg file
parms but so far this is just experimentation and I haven't had time to work on it
beyond the proof of concept phase.
-This only works in daemon mode so if your config files don't have RunAsDaemon:Yes in
them you're out of luck. Sorry.
-Note that line 19 of mrtg-2.17.4-graphite has DEBUG=qw(log) specified. This is
useful for troubleshooting graphite TCP socket open problems and the
MRTG-config-file-var-to-graphite-namespace conversions. This debug statement will
cause your MRTG log files to get big so I would recommend setting it to DEBUG=qw()
after things are working correctly.
-So far I have only run this on linux. I don't know if it will work on Windows or
anything else.
-You will need to install Net::Graphite from CPAN, so from your linux prompt...
perl -MCPAN -e shell
install Net::Graphite
-If the TCP socket from the MRTG server to the Graphite server goes away for some
reason (connectivity problems, graphite shutdown, etc) the MRTG daemon will die.
This is clearly a bad implementation on my part but I haven't had time to look at
it. Ideally MRTG will continue to run and update the RRD files if the Graphite
socket goes away and gracefully reconnect when the Graphite server is reachable
again.




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