broadcast_trigger.rb

module Zookeeper
  class BroadcastTrigger
    def initialize(zk, path)
      @zk   = zk
      @path = path
    end

    def trigger
      @zk.set(@path, "#{$$}")
    rescue ZK::Exceptions::NoNode
      @zk.mkdir_p(@path, :data => "#{$$}")
    end

    def watch(&block)
      @callback = block
      configure_watches
      self
    end

    def stop
      if @register
        @register.unregister
      end

      if @on_connected
        @on_connected.unregister
      end
    end

    def configure_watches
      @register ||= @zk.register(@path) do
        if stat = @zk.stat(@path, :watch => true)
          update_version(stat.version)
        end
      end

      @on_connected ||= @zk.on_connected do
        if stat = @zk.stat(@path, :watch => true)
          update_version(stat.version)
        end
      end

      if stat = @zk.stat(@path, :watch => true)
        @version = stat.version
      end
    end

    def update_version(new_version)
      old_version, @version = @version, new_version

      if old_version != new_version
        @callback.call
      end
    end
  end
end