I recently had to build a monitoring system including:

• Physical machine monitoring (cpu, memory, etc…)

• Virtual machines monitoring (cpu, memory, etc…)

• Ruby application servers (not only web application but also daemons which have to send counters)

I came accross collectd which is quite an awesome piece of software and configured it to dump rrds from all those data, first part done.

Now with with some rrd on disk I thought it would be a rather easy task to find an application which just draw the graph from them, looks like I was wrong… Most of the solutions I found out there want full control over the chain (they handle collection and drawing not one without the other), there is also mrtg which can with some hacking draw graph from data not network related but the graphs are just horrible and the frontend of those application takes more cpu/memory than any of the monitored application we have, really amazing if you ask me.

In the end I just came on Visage (github.com/auxesis/visage/) which is a great base, the idea is dead simple: read the rrd and send them to the client where the graph will be drawn. I really like the idea of making the browser do some of the work instead of just waiting for a picture to be generated.

I took inspiration from visage but since there was things I did not like at all with this application I finally rewrote parts of it and eventually ended with something without much common code lines so I simply changed its name.

My plans for it are really simple: being able to graph data from any rrd. Some work may be done on how data are display but I have no plan for supporting anything other than rrd and i wish to keep it as lightweight as possible.

• Sinatra : used as a backend to serve clients

• Errand (github.com/auxesis/rubyrrdtool) : read data from rrd files with a better api than the other wrappers out there

• jquery : I really love this javascript library

• flot (github.com/thenduks/flot) : draw the graph client side

  • it supports non contiguous dataset (if your set has null values in it the line will just be cut where null values are)

  • it can generates many graph format (bars, lines, points)

  • it is based on jquery and so does not rebuild all the required browser abstraction

  • use excanvas for the evil ie (I don’t care much about it but since some people are really using it… it may work or not)

The simplest way to be up and running is by using thin, you have to edit config/config.yml to point to your rrd folder

• gem install bundler thin –no-rdoc –no-ri

• gem bundle

• thin -R config.ru start -d (the -d flag is used to run in it background)

(tested only on ruby 1.9)