#!/usr/bin/env ruby
# Runs ApacheBench a preset number of times and outputs the mean request time as CSV
#
# Bryant Casteel
# http://bethings.postplatinum.com/tag/ab-time-chart/
# 2010-12-05

# configuration

MIN_CONNECTIONS = 1
MAX_CONNECTIONS = 1000
TARGET_SAMPLES = 100

# output the column headings
print '""'
$*.each do |url|
  print ",\"#{url}\""
end
puts

# output row of zeroes for origin
print '0'
$*.length.times do
  print ',0'
end
puts

# for increasing number of concurrent connections
interval = 1
connections = MIN_CONNECTIONS
while connections <= MAX_CONNECTIONS do
  # output the row heading
  print connections

  # test each URL
  $*.each do |url|
    mean_time = nil
    samples = TARGET_SAMPLES
    # keep trying in the event of a failure
    while mean_time.nil? and (samples > 0)
      hits = connections * samples
      if /Time per request.*?([\d\.]+).*(mean)/ =~ `ab -n #{hits} -c #{connections} "#{url}"`
        # store just the mean request time upon success
        mean_time = $1
      else
        # try fewer samples upon failure
        samples = (samples * 0.5).to_i
      end
    end
    if mean_time.nil?
      # fill in missing data in chart
      mean_time = '=NA()'
    end
    print ",#{mean_time}"
  end

  # end the row
  puts

  # calculate next increment
  if (connections / (interval * 10)) >= 1
    # increment the connections by increasing powers of 10
    interval = interval * 10
  end
  connections = connections + interval
end