Apache Flink：如何应用多个计数窗口函数？

Question

我有一个数据流是键控的，需要计算不同时间段（1分钟，5分钟，1天，1周）的翻滚计数。

有可能在一个应用程序中计算所有四个窗口计数吗？

Answer 1

是的，那是可能的。

如果您使用的是事件时间，您可以简单地将窗口级联，增加时间间隔。所以你是这样做的：

DataStream<String> data = ...
// append a Long 1 to each record to count it.
DataStream<Tuple2<String, Long>> withOnes = data.map(new AppendOne); 

DataStream<Tuple2<String, Long>> 1minCnts = withOnes
  // key by String field
  .keyBy(0) 
  // define time window
  .timeWindow(Time.of(1, MINUTES))
  // sum ones of the Long field
  // in practice you want to use an incrementally aggregating ReduceFunction and 
  // a WindowFunction to extract the start/end timestamp of the window
  .sum(1);

// emit 1-min counts to wherever you need it
1minCnts.addSink(new YourSink());

// compute 5-min counts based on 1-min counts
DataStream<Tuple2<String, Long>> 5minCnts = 1minCnts
  // key by String field
  .keyBy(0)
  // define time window of 5 minutes
  .timeWindow(Time.of(5, MINUTES))
  // sum the 1-minute counts in the Long field
  .sum(1);

// emit 5-min counts to wherever you need it
5minCnts.addSink(new YourSink());

// continue with 1 day window and 1 week window

请注意，这是可能的，因为：

null

如果要使用处理时间来计算这个值，则不能将窗口级联，而必须将输入数据流扇出到四个窗口函数。