如何在Google Dataflow中创建个性化WindowFn [英] How to create a personalised WindowFn in google dataflow

问题描述

我想以不同的方式创建一个不同的WindowFn，以便根据另一个字段而不是根据输入条目的时间戳将Windows分配给我的任何输入元素.我知道Google DataFlow SDK中的预定义WindowFn使用时间戳作为分配窗口的条件.

I'd like to create a different WindowFn in a such way to assign Windows to any of my input elements based on another field instead of based on my input entry's timestamp. I know the pre-defined WindowFn's from Google DataFlow SDK use the timestamp as a criteria to assign window.

更具体地说，我想创建一种SlidingWindows，但与其考虑将时间戳作为窗口分配标准，不如将其他字段视为该条件.

More specifically I'd like to create a kind of SlidingWindows but instead of considering timestamp as the Window assignment criteria I'd like to consider another field as that criteria.

如何创建自定义的WindowFn?创建自己的WindowFn时应考虑哪些要点?

How could I create my customised WindowFn? What are the points that I should consider when creating my own WindowFn?

谢谢.

推荐答案

要创建新的WindowFn，您只需从

To create a new WindowFn, you just need to inherit from WindowFn or a subclass and override the various abstract methods.

在您的情况下，您不需要窗口合并，因此您可以从NonMergingWindowFn继承，并且您的代码可能类似于

In your case, you don't need window merging, so you can inherit from NonMergingWindowFn, and your code could look something like

public class MyWindowFn extends NonMergingWindowFn<ElementT, IntervalWindow> {
  public Collection<W> assignWindows(AssignContext c) {
    return setOfWindowsElementShouldBeIn(c.element());
  }

  public boolean isCompatible(WindowFn other) {
    return other instanceof MyWindowFn;
  }

  public Coder<IntervalWindow> windowCoder() {
    return IntervalWindow.getCoder();
  }

  public W getSideInputWindow(final BoundedWindow window) {
    // You may not need this if you won't ever be using PCollections windowed 
    // with this as side inputs.  If that's the case, just throw.
    // Otherwise you'll need to figure out how to map the main input windows
    // into the windows generated by this WindowFn.
  }
}

这篇关于如何在Google Dataflow中创建个性化WindowFn的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！