SlidingWindowMap

SlidingWindowMap.scala

class SlidingWindowMap(keys: Set[String], maxCount: Int, periodMs: Int) {

  val times = new collection.mutable.HashMap[String, Vector[Long]]() with collection.mutable.SynchronizedMap[String, Vector[Long]]
  times ++= keys.map(k => (k, Vector[Long]()))

  def nextKey: Option[String] = {
    val now = System.currentTimeMillis
    times.synchronized {
      val trimmedTimes = times.toStream map { case (k, usage) =>
        val trimmedUsage = usage dropWhile (_ < now - periodMs)
        times(k) = trimmedUsage
        (k, trimmedUsage)
      }

      trimmedTimes find (_._2.length < maxCount) map (_._1)
    }
  }

  def addUsage(key: String) {
    times(key) = times.getOrElse(key, Vector[Long]()) :+ System.currentTimeMillis
  }

}