node_watcher.rb

module Papertrail
  module Zookeeper
    class NodeWatcher
      include Watchable

      attr_reader :name

      def initialize(zk, name, options = {})
        @zk   = zk
        @name = name

        @mutex = Mutex.new

        register
      end

      def register
        @zk.register(@name) do |event|
          @mutex.synchronize do
            Rails.logger.info "node_watcher: event received: #{event.inspect}"
            if event.node_created?
              handle_data(:created)
            elsif event.node_changed?
              handle_data(:changed)
            elsif event.node_deleted?
              handle_deleted
            else
              Rails.logger.info "node_watcher: Unknown event: #{event.inspect}"
            end
          end
        end

        @zk.on_connected do
          @zk.stat(@name, :watch => true)
        end

        @zk.stat(@name, :watch => true)
      end
    
      def handle_deleted
        # Re-register events
        @zk.stat(@name, :watch => true)
        fire(:deleted)
      end
    
      def handle_data(action)
        # Re-register events
        value, _ = @zk.get(@name, :watch => true)
        fire(action, value)
      rescue ZK::Exceptions::NoNode
        handle_deleted
      end
    end
  end
end