Wrapper to allow runit to send signals to the unicorn master even when its PID changes

unicorn_wrapper.sh

#!/bin/sh
set -e

APP=$1
APP_PATH="/srv/${APP}/current"
RAILS_ENV=$2
UNICORN_CONFIG="/etc/unicorn/${APP}.rb"

UNICORN_PID_FILE="/tmp/unicorn.${APP}.pid"

cd $APP_PATH

# start Unicorn in the background:
bundle exec unicorn -E $RAILS_ENV -c $UNICORN_CONFIG -D

# forward signals received in this wrapper to the Unicorn process:
for sig in HUP USR1 USR2 QUIT TERM QUIT
do
  trap 'kill -'$sig' $(cat $UNICORN_PID_FILE)' $sig
done

# loop forever while Unicorn has its pid file
while test -e $UNICORN_PID_FILE || test -e $UNICORN_PID_FILE.oldbin
do
   sleep 1
done