Flink侧输出流（Side Output）

需求：如果温度值小于32F，就将报警信息输出到侧输出流中

package com.run.wc

import org.apache.flink.streaming.api.scala.{OutputTag, StreamExecutionEnvironment}
import org.apache.flink.api.scala._
import org.apache.flink.streaming.api.functions.ProcessFunction
import org.apache.flink.streaming.api.functions.timestamps.BoundedOutOfOrdernessTimestampExtractor
import org.apache.flink.streaming.api.windowing.time.Time
import org.apache.flink.util.Collector

/**
 * @author 霄嵩
 */
/**
 * SideOutput侧输出流
 * 需求：如果温度值小于32F，就将报警信息输出到侧输出流中
 */
object SideOutputTest {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    env.setParallelism(1)

    val dataStream = env.socketTextStream("master", 9999)
    val mapStream = dataStream.map(x => {
      val line = x.split(",")
      Sensor(line(0).trim.toString, line(1).trim.toLong, line(2).trim.toDouble)
    })
    val stream = mapStream.assignTimestampsAndWatermarks(new BoundedOutOfOrdernessTimestampExtractor[Sensor](Time.seconds(1)) {
      override def extractTimestamp(element: Sensor): Long = {
        element.timestamp * 1000
      }
    })
    val processStream = stream.process(new SideOutputAlert())

    mapStream.print("map data")
    processStream.print("process data")
    //通过getSideOutput获取侧输出流，并打印输出
    processStream.getSideOutput(new OutputTag[String]("freezingAlert")).print("side output data")

    env.execute("side output test")
  }
}

//温度值小于32F，就将报警信息输出到侧输出流中
class SideOutputAlert() extends ProcessFunction[Sensor, Sensor] {
  //定义一个侧输出流标签
  lazy val freezingAlert: OutputTag[String] = new OutputTag[String]("freezingAlert")

  override def processElement(value: Sensor,
                              ctx: ProcessFunction[Sensor, Sensor]#Context,
                              out: Collector[Sensor]): Unit = {
    if (value.temperature < 32) {
      ctx.output(freezingAlert, s"${value.id}的温度值小于32F")
    } else {
      out.collect(value)
    }
  }
}

Result:
process data> Sensor(sensor_1,1547718207,37.0)
map data> Sensor(sensor_1,1547718207,37.0)
process data> Sensor(sensor_1,1547718207,36.0)
map data> Sensor(sensor_1,1547718207,36.0)
side output data> sensor_1的温度值小于32F
map data> Sensor(sensor_1,1547718207,31.0)
process data> Sensor(sensor_1,1547718207,36.0)
map data> Sensor(sensor_1,1547718207,36.0)
side output data> sensor_1的温度值小于32F
map data> Sensor(sensor_1,1547718207,20.0)