Here is how to capture both Gate states: open and closed without using GoF State Pattern. It looks like a thread, but it doesn't block any most of the time. Most of the previously hardcoded things are actor parameters now.

WrASSE_3_GateActor.scala

package wrasse3

import scala.actors.Actor._
import System.{currentTimeMillis => now}
import actors.{Actor, TIMEOUT}

class GateActor[R](sendRequest: => R,
                   errorResponse: R,
                   maxErrors: Int,
                   closePeriod: Int) extends Actor {

  def info(m: String) = println(this + " " + m)

  def stop() = try { exit() } catch { case _ => () }

  def act = loop{

    info("entering open state")
    var errors = 0

    loopWhile(errors < maxErrors) {
      react{
        case _ => {
          val r = sendRequest
          if (r == errorResponse) errors += 1 else errors = 0
          reply(r)
        }
      }
    } andThen {

      info("entering closed state")
      val end = now + closePeriod

      loopWhile(now < end) {
        reactWithin(end - now) {
          case TIMEOUT => ()
          case _ => {
            info("gate is currently closed");
            reply(errorResponse)
          }
        }
      }

    }
  }

}

Obsolete now. The current version is at http://github.com/przemek-pokrywka/wrasse3/blob/master/src/main/scala/wrasse3/GateActor.scala