Apache Flink：ProcessWindowFunction 实现

Question

我正在尝试使用 Scala 在我的 Apache Flink 项目中使用 ProcessWindowFunction。不幸的是，我已经无法实现一个基本的 ProcessWindowFunction，就像 Apache Flink 文档中使用的那样。

这是我的代码：

import org.apache.flink.streaming.api.scala._
import org.apache.flink.streaming.api.scala.{StreamExecutionEnvironment, _}
import org.apache.flink.streaming.api.windowing.time.Time
import org.fiware.cosmos.orion.flink.connector.{NgsiEvent, OrionSource}
import org.apache.flink.streaming.api.functions.windowing.ProcessWindowFunction
import org.apache.flink.streaming.api.windowing.windows.TimeWindow
import org.apache.flink.streaming.api.windowing.assigners.SlidingProcessingTimeWindows
import org.apache.flink.util.Collector
import scala.collection.TraversableOnce

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

 val env = StreamExecutionEnvironment.getExecutionEnvironment
 val eventStream = env.addSource(new OrionSource(9001))

 val processedDataStream = eventStream.flatMap(event => event.entities)
   .map(entity => (entity.id, entity.attrs("temperature").value.asInstanceOf[String]))
     .keyBy(_._1)
     .window(SlidingProcessingTimeWindows.of(Time.seconds(10), Time.seconds(5)))
     .process(new MyProcessWindowFunction())

 env.execute("Socket Window NgsiEvent")
 }
}


private class MyProcessWindowFunction extends ProcessWindowFunction[(String, String), String, String, TimeWindow] {

def process(key: String, context: Context, input: Iterable[(String, String)], out: Collector[String]): Unit = {
  var count: Int = 0
  for (in <- input) {
    count = count + 1
  }
  out.collect(s"Window ${context.window} count: $count")
 }
}

从 IntelliJ 我得到以下提示：

1) 这显示了新类对象的创建位置：

Type mismatch, expected: ProcessWindowFunction[(String, String), NotInferedR, String, TimeWindow], actual: MyProcessWindowFunction

2) 这直接显示在课堂上：

Class 'MyProcessWindowFunction' must either be declared abstract or implement abstract member 'process(key:KEY, context:ProcessWindowFunction.Context, iterable:Iterable<IN>, collector:Collector<OUT>):void' in 'org.apache.flink.streaming.api.functions.windowing.ProcessWindowFunction'

构建代码显示以下错误：

Error:(51, 16) type mismatch;
found   : org.apache.flink.MyProcessWindowFunction
required: 
org.apache.flink.streaming.api.scala.function.ProcessWindowFunction[(String, String),?,String,org.apache.flink.streaming.api.windowing.windows.TimeWindow]
  .process(new MyProcessWindowFunction())

感谢您的每一次帮助。

Answer 1

在与另外 2 个人一起调试了一段时间后，我们终于找到了问题所在。

在我的代码中，我使用了以下导入：

import org.apache.flink.streaming.api.functions.windowing.ProcessWindowFunction

但使用 Scala 时正确的导入似乎是：

import org.apache.flink.streaming.api.scala.function.ProcessWindowFunction

Answer 2

//package of  ProcessWindowFunction is 
import org.apache.flink.streaming.api.scala.function.ProcessWindowFunction

//The correct way to call this method
new MyProcessWindowFunction()[(String, String), String, String, TimeWindow]

//I know the official documents don't.This may be a bug