Background

Graphit is a tool that reads time-based numeric data over a network socket and plots it in near real-time.

Here's a screenshot:

http://github.com/marktriggs/Graphit/blob/master/screenshot.png

I'm in the unfortunate position of being a systems administrator by day, and that means keeping an eye on lots of different things--load averages, number of Apache processes, number of threads for certain applications, things like that. Tools like RRDTool do a great job of gathering and plotting data, but they're not really designed for real-time visualisation. I wanted something I could stare at in the quieter moments.

Graphit uses the wonderful JFreeChart (http://www.jfree.org/jfreechart/) to do its plotting. The other bits (the easy bits) are Clojure code to handle reading data from a socket, tracking multiple graphs, and that sort of thing.

Building it

Thanks to the wonders Of Leiningen and Clojars this should be easy to build. The steps:

1. Get Leiningen from http://github.com/technomancy/leiningen and put the 'lein' script somewhere in your $PATH.

2. From graphit's root directory, run lein uberjar'. Lein will grab all required dependencies and produce agraphit.jar'.

   Note: Thanks to Java's AWT madness you seem to need your DISPLAY environment variable set to even compile the thing.

3. Run the jar with, for example:

   java -jar graphit.jar --redraw 2000 --port 6666

   This will redraw all graphs once every two seconds, and will listen on port 666 for data.

Trying it out

Once Graphit is running, you can plot some random lines just by using bash and netcat:

!/bin/bash

while [ 1 ]; do for i in 1 2 3; do for j in 1 2 3; do echo -e "graph$i $j $RANDOM" done done sleep 1 done | nc localhost 6666

And that's about all there is to know: you connect to Graphit on its port, send it one-reading per line in either this format:

name of graph[tab]name of line[tab]y value

or this one:

name of graph[tab]x value[tab]name of line[tab]y value

or if you want to do times:

name of graph[tab]time string[tab]name of line[tab]y value[tab]SimpleDateFormat string

JFreeChart gives some niceties for free: you can drag a rectangle to zoom in, hold down control and click+drag to pan around, right click to get a context menu. All sorts of wonderful things.

The end. Thanks for reading.