Zookeeper leader election using Ruby

election_candidate.rb

# http://zookeeper.apache.org/doc/r3.3.4/recipes.html#sc_leaderElection
require 'rubygems'
require 'bundler/setup'
require 'zookeeper'
require 'hashie'

class ElectionCandidate
  ROOT_PATH = "/election"
  NODE_PATH = "candidate_"

  attr_reader :zookeeper, :children, :node_path

  def initialize
    @zookeeper = Zookeeper.new("localhost:2181")
    root_path_create! unless root_path_exists?
    register!
  end

  def root_path_create!
    @zookeeper.create(path:ROOT_PATH, data:ROOT_PATH)
  end

  def root_path_exists?
    Hashie::Mash.new(@zookeeper.get(path:ROOT_PATH)).stat.exists?
  end

  def register!
    path = "#{ROOT_PATH}/#{NODE_PATH}"
    result = Hashie::Mash.new(@zookeeper.create(path:path, data:path, ephemeral:true, sequence:true))
    if result.rc == 0
      @node_path = result.path
    end
  end

  def registered?
    !self.node_path.nil?
  end

  def leader?
    result = Hashie::Mash.new(@zookeeper.get_children(path:ROOT_PATH))
    @children = result.children
    puts "ERROR: #{result}" if result.rc != 0

    leader = result.children.select{|c| c[/#{NODE_PATH}/] }.sort.first
    leader_path = "#{ROOT_PATH}/#{leader}"
    result.rc == 0 && result.children && self.node_path == leader_path 
  end
end

candidate = ElectionCandidate.new

loop do
  system "clear"
  puts "candidate '#{candidate.node_path}'"  
  if candidate.leader?
    puts "I am the leader!"
  else
    puts "candidates: #{candidate.children}"
  end
  sleep 5
end