我尝试在flink中实现窗口触发器，如果平均值高于阈值，它将触发。
流式数据将学生的姓名和标记用分隔符隔开 , . 如果学生的平均分数超过 90 不考虑尝试次数。
示例数据：

Fred,88
Fred,91
Wilma,93
.
.

当前flink代码：

import org.apache.flink.streaming.api.scala._
import org.apache.flink.streaming.api.windowing.assigners.GlobalWindows
import org.apache.flink.streaming.api.windowing.time.Time
import org.apache.flink.streaming.api.windowing.triggers.Trigger.TriggerContext
import org.apache.flink.streaming.api.windowing.triggers.{CountTrigger, PurgingTrigger, Trigger, TriggerResult}
import org.apache.flink.streaming.api.windowing.windows.{GlobalWindow, Window}

case class Marks(name : String, mark : Double, count : Int)

class MarksTrigger[W <: Window] extends Trigger[Marks,W] {

  override def onElement(element: Marks, timestamp: Long, window: W, ctx: TriggerContext): TriggerResult = {
    if(element.mark > 90) TriggerResult.FIRE  // fire if avg mark is > 90
    else TriggerResult.CONTINUE
  }

  override def onProcessingTime(time: Long, window: W, ctx: TriggerContext): TriggerResult = {
    TriggerResult.CONTINUE
  }
  override def onEventTime(time: Long, window: W, ctx: TriggerContext): TriggerResult = {
    TriggerResult.CONTINUE
  }

  override def clear(window: W, ctx: TriggerContext) = ???
}

object Main {
  def main(args: Array[String]) {

    val env = StreamExecutionEnvironment.getExecutionEnvironment
    val data = env.socketTextStream("localhost", 9999)

    val fdata = data.map { values =>
      val columns = values.split(",")
      Marks(columns(0), columns(1).toDouble, 1)
    }

    val keyed = fdata.keyBy(_.name).
      window(GlobalWindows.create()).
      trigger(new MarksTrigger[GlobalWindow]()). // TODO

    keyed.print()
    env.execute()
  }
}

正在计算平均值：在批处理模式下尝试了以下操作

case class Marks(name : String, mark : Double, count : Int)

val data = benv.fromElements(("Fred", 88.0), ("Fred", 95.0), ("Fred", 91.0), ("Wilma", 93.0), ("Wilma", 95.0), ("Wilma", 98.0))

data.map(x => (x._1, x._2, 1)).groupBy(0).reduce { (x, y) => 
    (x._1, x._2 + y._2, x._3 + y._3) 
}.map(x => Marks(x._1, x._2/x._3, x._3)).collect

我怎么把这些绑在一起？应该 .window() 以及 .trigger() 在计算平均数之前被调用或者平均数计算应该在里面做 onElement() ?