Basic puma configuration because the example in the puma repo is shit.

puma.conf

# /etc/init/puma.conf - Puma config

# This example config should work with Ubuntu 12+.  It
# allows you to manage Puma instances with
# Upstart, Ubuntu's native service management tool.
#
# Save this config as /etc/init/puma.conf then mange puma with:
#   sudo start puma app=/path/to/application
#   sudo stop puma app=/path/to/application
#   sudo status puma app=/path/to/application
#
# or use the service command:
#   sudo service puma {start,stop,restart,status} app=/path/to/application
#

description "Puma Background Worker"

# no "start on", we don't want to automatically start
stop on (runlevel [06])

# change deploy to match your deployment user if you want to use this as a less privileged user (recommended!)
setuid deploy
setgid deploy

respawn
respawn limit 3 30

instance ${app}

script
    chdir ${app}

    logger -t puma "Starting server: $app"
    rvm_env=`cat .ruby-version`@`cat .ruby-gemset`
    export RUBYOPT=-Ku
    exec /usr/local/rvm/bin/rvm-shell $rvm_env -c 'bundle exec puma -C config/puma.rb'
end script