how to get backtraces of running ruby rack process passenger

all_backtraces_passenger.sh

#at least on ubuntu + apache + passenger:
# send SIGQUIT to all processes: (ref: https://groups.google.com/forum/#!msg/phusion-passenger/B8SNMH2ootY/oJRvlw19DgAJ)
sudo /home/rdp/installs/ree-187/bin/passenger-memory-stats | grep RubyApp | cut -d " " -f 1 | xargs -n1 kill -3
sleep 3
sudo tail -n 1000 /var/log/apache2/error.log