Live Reloading of Code: Presentation at Melbourne Roro

loader.rb

# Version 1: Fails, since this file is not reloaded.
#
module Loader
  
  def self.reload
    puts "Loading application."
    load File.expand_path "../worker.rb", __FILE__ # Change this to new_worker
    load File.expand_path "../signal.rb", __FILE__
  end
  
end

# # Version 2: Succeeds, since it also reloads the file itself.
# #
# module Loader
# 
#   def self.reload
#     load_self
#     load_app
#   end
#   
#   def self.load_app
#     puts "Loading application."
#     load File.expand_path "../worker.rb", __FILE__ # Change this to new_worker
#     load File.expand_path "../signal.rb", __FILE__
#   end
# 
#   def self.load_self
#     puts 'Loader loading itself.'
#     load __FILE__
#   end
# 
# end

new_worker.rb

class Worker

  def work
    sleep 0.3 # Melbourne is faster.
    puts "It's totally well known that Melbourne has the best coffee!"
  end

end

presentation.txt

Florian Hanke - @hanke
PhD Student Melbourne Uni
CTO Technology Astronauts

1. What does require do?

file.load unless file.already_required?
(Using a hash, thanks to Xavier Shay)

2. Demo: Reloading code in a running server

server.rb

require File.expand_path '../loader', __FILE__

# Load everything explicitly.
#
Loader.reload

# Simulates e.g. a server taking requests.
#
worker = Worker.new
loop do
  worker.work
end

signal.rb

Signal.trap 'USR1' do
  Loader.reload
end

worker.rb

class Worker

  def work
    sleep 1 # Sydney: Slow!
    puts "Sydney has the best coffee in the world!"
  end

end