[ Celluloid / DCell / Ruby ]: Run a distributed set of cells.

README.md

Running a distributed actor web in Ruby using Celluloid and DCells

Requirements

• DCell version 1.16.0
• ZeroMQ version 3.2.5
• A Redis instance accessible by URI

Why?

The docs on the formal wiki seem a little vague on versioning and dependencies, and doesn't neatly indicate a teardown sequence for the actors it demonstrates. This updated example has all of that.

itchy.rb

require 'dcell'

url = ENV['REDIS_URI']

DCell.start(
  id: "itchy",
  addr: "tcp://127.0.0.1:9001",
  registry: { adapter: 'redis', url: url }
)

class Itchy
  include Celluloid

  def initialize
    puts "Ready for mayhem!"
    @n = 0
  end

  def fight
    @n = (@n % 6) + 1
    if @n <= 3
      puts "Bite!"
    else
      puts "Fight!"
    end
  end

  def end_the_show
    puts "The itchy and scratchy show!"
    terminate
  end
end

class ItchyGroup < Celluloid::SupervisionGroup
  supervise Itchy, as: :itchy
end

supervisor = ItchyGroup.run!

while supervisor.actors.any?
  sleep(rand)
end

scratchy.rb

require 'dcell'
url = ENV['REDIS_URI']

DCell.start(
  id: "scratchy",
  addr: "tcp://127.0.0.1:9002",
  registry: { adapter: 'redis', url: url }
)

class Scratchy
  include Celluloid

  attr_reader :itchy, :service

  def initialize
    @service = DCell::Node[:itchy]
    @itchy   = service[:itchy]
    link service
    puts "Fighting itchy! (check itchy's output)"
  end

  def the_show
    6.times { itchy.fight; sleep(rand) }
    sleep(rand)
    itchy.end_the_show
  end
end

Scratchy.new.the_show

Some quirks I noticed: If you don't explicitly state the ZMQ address, then the registry will clobber itself and hang. So in terms of service discovery, this doesn't really provide a great example for anything which isn't hard coded.