A primitive way to ensure that your Passenger processes don't eat up your machine completely. It will kill any Rack app process that starts to eat more than 300MB RAM. I used this to find a leak in a Sinatra application.

gistfile1

#!/bin/bash

while :; do
  stats=$(passenger-memory-stats | grep Rack)
  if [ "$stats" != "" ]; then
    echo $stats
    echo $stats | egrep --color=always 'MB ([12][0-9]|[3-9])..\.. MB'
    pid=$(echo $stats | egrep 'MB ([12][0-9]|[3-9])..\.. MB' | awk '{ print $1 }')
    if [ "$pid" != "" ]; then
      ps aux | grep $pid
      kill $pid && echo "$pid killed."
    fi
    echo "---"
  fi
  sleep 0.5
done