development server Puma + Listen + FSEvent (macOS) : Fix running too many fsevent_watch processes

00_README.md

https://gist.github.com/steakknife/b318a570803b08c1548c7f51c18c0753

License

Dual-licensed: MIT or DWFTYL

Problem (on macOS only)

• Listen fires up a fsevent_watch for every directory watched
• Puma is a threaded server, restarting it doesn't restart the Ruby process
• The development server + spring uses Listen to hot-reload code (models, views, controllers, etc.)
• Restarting the server doesn't call #stop on the Listen instances
• Tons and tons of fsevent_watch appear until fork() fails

Solution

• Call #stop on all Listen instances (including yours), to kill off unneeded fsevent_watch

Installation

1. Add all the other files included in this gist as per their names
2. Add this to your config/puma.rb

# config/puma.rb

#...

# FSEvent cleanup -- begin
# let puma find custom, project-included puma plugins
lib = File.expand_path('lib')
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include(lib)

# kill off fsevent_watch in development
plugin :fsevent_cleanup
# FSEvent cleanup -- end

Notes

1. Works with MRI
2. Won't work with JRuby unless ObjectSpace is enabled
3. Might not work on Rubinius
4. Don't use bin/rails s use bin/bundle exec puma because Rails + Puma + rails c is broken (both try to write tmp/pids/server.pid, rails doesn't like threaded servers restarting themselves)

add_plugin_restart_hook.rb

# lib/puma/plugin/add_plugin_restart_hook.rb
require 'puma/plugin'

Puma::Plugin.create do
  def config(dsl)
    Puma::Launcher.class_eval do
      def fire_plugins_restart
        @config.plugins.fire_restarts self
      end
    end

    Puma::PluginLoader.class_eval do
      def fire_restarts(launcher)
        @instances.each do |i|          
          i.restart(launcher) if i.respond_to? :restart
        end
      end
    end

    dsl.on_restart do |launcher|
      launcher.fire_plugins_restart
    end
  end
end

fsevent_cleanup.rb

# lib/puma/plugin/listen_cleanup.rb
require 'puma/plugin'

Puma::Plugin.create do
  def config(dsl)
    dsl.plugin :add_plugin_restart_hook
  end

  # call #stop on all FSEvent instances
  # this should close pipes and make fsevent_watch'es die
  def restart(_launcher)
    return unless defined? FSEvent
    ObjectSpace.each_object(FSEvent) { |x| x.stop }
  end
end