Flink之Watermarks

1、代码案例

package window

import com.yangwj.api.SensorReading
import org.apache.flink.streaming.api.TimeCharacteristic
import org.apache.flink.streaming.api.functions.source.SourceFunction
import org.apache.flink.streaming.api.functions.timestamps.BoundedOutOfOrdernessTimestampExtractor
import org.apache.flink.streaming.api.scala.{DataStream, StreamExecutionEnvironment, _}
import org.apache.flink.streaming.api.windowing.time.Time

import scala.util.Random

/**
 * @author yangwj
 * @date 2021/1/7 21:45
 * @version 1.0
 */
object WaterMarksTime {
  /**
   * 窗口：分为时间窗口和计数窗口
   * @param args
   */
  def main(args: Array[String]): Unit = {
    val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment
    env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)

    val dataStream: DataStream[SensorReading] = env.addSource(new MySensorSource)
//      .assignAscendingTimestamps(_.timestamp)  //assignAscendingTimestamps 升序数据提取时间
      //assignTimestampsAndWatermarks(毫秒)将大部分数据都放入bucket中，得到近似正确数据
      .assignTimestampsAndWatermarks(new BoundedOutOfOrdernessTimestampExtractor[SensorReading](Time.seconds(3)) {
        override def extractTimestamp(t: SensorReading): Long = {
          t.timestamp
        }
      })
    //每15秒统计一次温度最小值
    val laterTag = new OutputTag[(String, Double, Long)]("later")
    val value: DataStream[(String, Double, Long)] = dataStream
      .map(data => (data.id, data.temperature, data.timestamp))
      .keyBy(_._1) //按照二元组的第一个元素分组
      // .window(TumblingEventTimeWindows.of(Time.seconds(15))) //定义滚动时间窗口
      //      .window(SlidingEventTimeWindows.of(Time.minutes(5),Time.seconds(5)))//滑动窗口
      //      .window(EventTimeSessionWindows.withGap(Time.seconds(5)))// 会话窗口
      .timeWindow(Time.seconds(15)) //定义滚动时间窗口
      //      .timeWindow(Time.minutes(5),Time.seconds(5))//滑动窗口
      //.countWindow(5)//计数窗口
      //      .minBy(1)
      .allowedLateness(Time.minutes(1)) // 这个设定将watermark漏网之鱼进行补抓
      .sideOutputLateData(laterTag)
      .reduce((curs, newd) => (curs._1, curs._2.min(newd._2), newd._3))

    value.print("windows")

    value.getSideOutput(laterTag).print("outSide Stream")
    env.execute("reduce test")

  }
}
//自定义数据源
class MySensorSource extends SourceFunction[SensorReading]{

  //定义一个标识位，用来表示数据源是否正常运行发出数据
  var running :Boolean = true
  //sourceContext 发送数据
  override def run(sourceContext: SourceFunction.SourceContext[SensorReading]): Unit = {
    //定义无线循环，不断产生数据，除非被cancel
    val rand = new Random()
    var curTemp= 1.to(4).map(i => ("sensor" + i, rand.nextDouble() * 100))

    while (running){
      curTemp = curTemp.map(data =>(data._1,data._2+rand.nextGaussian()))

      val curTime = System.currentTimeMillis()
      println("输入值:"+curTemp+",时间为:"+curTime)
      curTemp.foreach(data => sourceContext.collect(SensorReading(data._1,curTime,data._2)))
      Thread.sleep(3000)
    }
  }

  override def cancel(): Unit = false
}