Chef + runit + Unicorn + rbenv

sv-unicorn-run.erb

#!/bin/bash -e

export RBENV_ROOT=/usr/local/rbenv
export PATH=/usr/local/rbenv/shims:/usr/local/rbenv/bin:/usr/local/bin:"$PATH"

APP="<%= @options[:app].application.name %>"
APP_PATH="<%= @options[:app].path %>"
RAILS_ENV="<%= @options[:rails_env] %>"
UNICORN_CONFIG="/etc/unicorn/${APP}.rb"
CUR_PID_FILE="${APP_PATH}/shared/pids/unicorn.pid"
OLD_PID_FILE="${PID_FILE}.oldbin"

function is_unicorn_alive {
  set +e
  if [ -n $1 ] && kill -0 $1 >/dev/null 2>&1; then
    echo "yes"
  fi
  set -e
}

if [ -e $OLD_PID_FILE ]; then
  OLD_PID=$(cat $OLD_PID_FILE)
  echo "Waiting for existing master to exit. PID: ($OLD_PID)."
  while [ -n "$(is_unicorn_alive $OLD_PID)" ]; do
    /bin/echo -n '.'
    sleep 2
  done
fi

if [ -e $CUR_PID_FILE ]; then
  CUR_PID=$(cat $CUR_PID_FILE)
  if [ -n "$(is_unicorn_alive $CUR_PID)" ]; then
    echo "Unicorn master already running. PID: ($CUR_PID)."
    RUNNING=true
  fi
fi

if [ ! $RUNNING ]; then
  echo "Starting unicorn."
    $APP_PATH/current/bin/unicorn -E $RAILS_ENV -c $UNICORN_CONFIG -D
  sleep 3
  CUR_PID=$(cat $CUR_PID_FILE)
fi

function restart {
  echo "Initialize new master with USR2."
  kill -USR2 $CUR_PID
  # Make runit restart to pick up new unicorn pid
  sleep 2
  echo "Restarting service to capture new pid."
  exit
}

function graceful_shutdown {
  echo "Initializing graceful shutdown."
  kill -QUIT $CUR_PID
}

trap restart HUP QUIT
trap graceful_shutdown INT TERM

for sig in USR1 USR2
do
  trap 'kill -'$sig' $(cat $CUR_PID_FILE)' $sig
done

echo "Waiting for current master to die. PID: ($CUR_PID)"
while [ -n "$(is_unicorn_alive $CUR_PID)" ]; do
  /bin/echo -n '.'
  sleep 2
done

echo "Unicorn process ($CUR_PID) has quit."

This is a runit run template file to manage Unicorn within a Chef environment. It assumes:

• rbenv is installed globally to manage rubies (setting environment variables required for successful operation)
• --binstubs are generated for an application on deployment (so we can call the unicorn binstub directly to start Unicorn)

Calling a binstub directly guarantees that rbenv will execute the correct Ruby version (assuming a per-application version is specified within a .ruby-version file within the application repository), and that the correct Gems will be loaded. (Note: it is no longer necessary to cd into the application directory or modify Ruby shebangs to use ruby-local-exec, as rbenv has rolled the functionality into the ruby shim)

Can I ask how sig is set on line 62? Is it set somewhere external to this script?

@MarkBennett I think that's if it receives a USR1/2 signal.