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For fun I decided to chart various statistics from my mail server’s logs. I ended up with these charts using John Barnette’s GChart, some regular expressions, and cron.

The details of parsing out the data from the log files and setting up a crontab is boring, so I’ll spare you the details of that.

Using GChart is really cool and easy. Here’s what I used to generate the Amavis Statistics chart, the others are all nearly the same, just different labels and titles.

def graph_amavis(data)
  # These are the labels and colors I'm using 
  labels = %w[Banned Spam   Spammy Bad\ Header Clean]
  colors = %w[000000 ff0000 ff7f00 ffff00      00ff00]

  max = data.map { |vals| vals.max }.max

  # Since axis labels aren't yet supported by the API in 0.2.0, I use :extras
  extras = { 'chxt' => 'r', 'chxl' => "0:|#{axis_labels max}" }

  chart = GChart.line :title => 'Amavis Statistics', :data => data,
                      :labels => labels, :colors => colors, :extras => extras

  chart_path = File.join File.dirname(@file), 'amavis_statistics.png'

  chart.size = '750x400'# can't be > 300,000 pixels
  chart.write chart_path
end

That’s it! One minor gotcha I had was that I needed to transpose the data set after reading it in because it wasn’t in the right order for GChart to consume it, but with Array#transpose, it’s just an extra method call before graphing.

Also, I wrote this simple utility function to calculate some good-enough axis labels:

def axis_labels(max)
  axis_labels = []
  0.upto 10 do |i| axis_labels << (max * 0.1 * i).to_i end
  axis_labels.join '|'
end

The values aren’t prettily chosen, but they work well enough.