Parses a Heroku log (defaults to /var/log/heroku, but you can pass it a log file as the first argument to the script), then prints out the dyno, the error code, the count, and the percentage of the total.

requests-by-dyno

#!/bin/bash

# ---------------
# Example output:
# ---------------
#       Dyno      Count  % of Total
# app[web.1]        103      14.33%
# app[web.2]        140      19.47%
# app[web.3]        111      15.44%
# app[web.4]        111      15.44%
# app[web.5]        123      17.11%
# app[web.6]        131      18.22%

LOG=${1:-/var/log/heroku}
grep 'app\[web.' $LOG | grep 'Started' | awk 'BEGIN{printf "%10s %10s %11s\n", "Dyno", "Count", "% of Total"}{a[$5]++;total++}END{for(i in a){printf "%10s %10s %10.2f%%\n",i, a[i], a[i]/total*100;}}'