Flink ProcessFunction API自定义事件处理

作用：可以访问时间戳、watermark 以及注册定时事件。还可以输出特定的一些事件，例如超时事件等。Process Function 用来构建事件驱动的应用以及实现自定义的业务逻辑(使用之前的window 函数和转换算子无法实现)。例如，Flink SQL 就是使用 Process Function 实现的。

完整代码：

object WindowTest {

  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    env.setParallelism(1)
    env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime)

    val socketStream = env.socketTextStream("hadoop102", 7777)

    val dataStream: DataStream[SensorReading] = socketStream.map(d => {
      val arr = d.split(",")
      SensorReading(arr(0).trim, arr(1).trim.toLong, arr(2).toDouble)
    })
      .assignTimestampsAndWatermarks(new BoundedOutOfOrdernessTimestampExtractor[SensorReading](Time.seconds(1)) {
        override def extractTimestamp(t: SensorReading): Long = t.timestamp * 1000
      })

    //自定义温度报警处理
    val processStream = dataStream.keyBy(_.id).process(new TempIncreAlert)

    //输出自定义业务逻辑
    processStream.print("process stream")

    //打印原始的dataStream
    dataStream.print("data stream")


    env.execute("window test")
  }

}

case class SensorReading(id: String, timestamp: Long, temperature: Double)

//温度报警处理类
class TempIncreAlert extends KeyedProcessFunction[String, SensorReading, String] {

  //定义一个状态，保存上一条数据的温度
  lazy val savedTemper: ValueState[Double] = getRuntimeContext.getState(new ValueStateDescriptor[Double]("lastTemp", classOf[Double]))

  //定义一个状态，保存定时器的时间戳
  lazy val savedTimer: ValueState[Long] = getRuntimeContext.getState(new ValueStateDescriptor[Long]("currentTimer", classOf[Long]))


  override def processElement(i: SensorReading, context: KeyedProcessFunction[String, SensorReading, String]#Context, collector: Collector[String]): Unit = {

    //取出上一个温度值
    val preTemp = savedTemper.value()

    //更新温度值
    savedTemper.update(i.temperature)

    //取出上一个定时器的时间戳
    val preTimerTs = savedTimer.value()

    //如果温度在30度以上上升，则注册定时器
    if (i.temperature > preTemp && preTemp > 30 && preTimerTs == 0) {
      //注册3秒后触发的定时器
      val ts = context.timerService().currentProcessingTime()
      context.timerService().registerProcessingTimeTimer(ts + 3000)

      //保存刚注册的定时器时间戳
      savedTimer.update(ts)
    } else if (i.temperature < preTemp || preTemp == 0) {
      //删除定时器
      context.timerService().deleteProcessingTimeTimer(preTimerTs)
      //清空状态
      savedTimer.clear()
    }

  }

  //定时器回调函数
  override def onTimer(timestamp: Long,
                       ctx: KeyedProcessFunction[String, SensorReading, String]#OnTimerContext,
                       out: Collector[String]): Unit = {
    //输出报警信息
    out.collect(ctx.getCurrentKey + "温度超过30度且连续上升！")
  }
}

端口输入数据

[atguigu@hadoop102 ~]$ nc -lk 7777
sensor_1, 1547718200, 30
sensor_1, 1547718200, 29    
sensor_1, 1547718200, 31
sensor_1, 1547718200, 33

控制台打印

data stream> SensorReading(sensor_1,1547718200,30.0)
data stream> SensorReading(sensor_1,1547718200,29.0)
data stream> SensorReading(sensor_1,1547718200,31.0)
data stream> SensorReading(sensor_1,1547718200,33.0)
process stream> sensor_1温度超过30度且连续上升！