gistfile1.scala

  /* interleave slots so that slots of different nodes are given priority during assignment of topology as opposed to slots of the same node */
  private def interleaveSlotsByNode(slots: Set[WorkerSlot]): List[WorkerSlot] = {
    val groupedSeq = slots.groupBy(_.getNodeId).toSeq
    val slotsByNode = mutable.Map[String, Set[WorkerSlot]](groupedSeq: _*)
    val nodes = slotsByNode.keys.toList.sorted
    val results = mutable.ListBuffer[WorkerSlot]()
    while (!slotsByNode.isEmpty) {
      for (node <- nodes) {
        slotsByNode.get(node) match {
          case Some(slots) => {
            val firstSlot = slots.head
            results += firstSlot
            val remaining = slots - firstSlot
            if (remaining.isEmpty)
              slotsByNode.remove(node)
            else
              slotsByNode.put(node, remaining)
          }
          case None => {}
        }
      }
    }
    results.toList
  }