unicorn_reloader

#!/usr/bin/env ruby
#
# unicorn_reloader
#
# spawns a unicorn to serve a rack app in the given directory.  Watches
# the app files for changes, restarting the unicorn worker when they're
# detected.
#
# Tony Strauss <tony at animoto.com>
# Forked in order to:
# * Have bring down Unicorn as part of its exit sequence
# * Eliminate the need to rely on unicorn's pid file
# * Rename (unicorn_reloader)
#
# This script relies on:
# directory_watcher
# rev
#
# This script also echoes the unicorn output to stdout
#
# This originally was based on Jonathan Stott's watcher.rb (Unicorn Sparkles):
# Jonathan D. Stott <jonathan.stott@gmail.com>
# http://namelessjon.posterous.com/magical-reloading-sparkles
#
# Copyright (c) 2010 Jonathan Stott.
# Copyright (c) 2011 Animoto Productions (http://www.animoto.com)
# Released under the terms of the MIT License

require 'directory_watcher'

def usage
  puts "The unicorn_reloader launches unicorn and monitors source files for"
  puts "changes.  When it detects a change, it restarts the Unicorn workers,"
  puts "reloading the web application.  This allows you to"
  puts "immediately see the results of your changes without any"
  puts "manual intervention.  While doing so, it also tails the specified"
  puts "log files."
  puts ""
  puts "unicorn_reloader unicorn_config_file rackup_file log_file1 log_file2 ..."
end

if ARGV.empty?
  usage
  exit
elsif ARGV.length < 2
  $stderr.print "Error: invalid arguments!\n\n"
  usage
  exit false
end

log_files = []

unicorn_config_file = ARGV[0]
rackup_file = ARGV[1]

if ARGV.length > 2
  log_files = ARGV[2..ARGV.length]
end

# The application files that will be watched in order to trigger reloads.
GLOB = ['**/*.rb'] # glob of the application's files

# remove the old logs
log_files.each do |log_file|
  begin
    File.delete log_file
  rescue Errno::ENOENT
  end
end

# start unicorn via fork/exec
unicorn_pid = Process.fork do
  Process.exec "unicorn --config-file #{unicorn_config_file} #{rackup_file}"
end

logs = []

#
# Wait for unicorn to start and create any
# specified log files.
#
log_files.each do |log_file|
  begin
    logs << File.open(log_file)
  rescue Errno::ENOENT
    retry
  end
end

# watch our app for changes
dw = DirectoryWatcher.new '.',
  :glob => GLOB,
  :interval => 2,
  :scanner => :rev,
  :pre_load => true

# SIGHUP makes unicorn respawn workers
dw.add_observer do |*args|
  puts "Detected source code change.  Restarting Unicorn workers!"
  Process.kill :HUP, unicorn_pid
end

trap "INT" do |sig|
  # Kill unicorn, which will trigger the unicorn_relaoder to exit below
  Process.kill :QUIT, unicorn_pid
end

dw.start

#
# Wait for any one of:
# * Unicorn to exit (caught by waitpid2)
# * unicorn_reloader to be interrupted (resulting in our SIGINT handler being run, which will kill unicorn)
#
unicorn_exit_status = nil
while unicorn_exit_status == nil do
  logs.each do |log|
    print log.read
  end

  #
  # The sleep is hacky; this could be improved by using the self-pipe trick
  #
  sleep 0.1

  # Non-blocking waitpid
  unused, unicorn_exit_status = Process.waitpid2 unicorn_pid, Process::WNOHANG
end

dw.stop

if not unicorn_exit_status.exited? or not unicorn_exit_status.success?
  $stderr.puts "\nERROR: Unicorn exited with bad status: #{unicorn_exit_status}"
  exit false
else
  exit
end