About the windowOperator and Watermark

[曲洋]

Hi Experts,

Given that a window in the stream is configured with short window size like timeWinodw(3s)，
and I gotta utilize Event time and Periodic Watermark.
The stream input is [watermark(7) | 6, 5, 3, 4, 1, 2],
and then two windows are created (3,1,2) (6,5,4) before watermark(7) arriving.
But in this situation when the current watermark is received,
which window or how many windows will be be triggered to fire and emit?
My question is what will the windowOperater do when it comes to two parellel windows edge end timestamps both smaller than cerrent watermark timestamps?

[dwysakowicz]

Hi,

When a Watermark arrives the window operator will emit all windows that
are considered finished at the time of the Watermark. In your example
(assuming both windows are finished) they will both be emitted.

Best,

Dawid

On 08/05/2021 08:03, 曲洋 wrote:
> Hi Experts,
>
> Given that a window in the stream is configured with short window size like timeWinodw(3s)，
> and I gotta utilize Event time and Periodic Watermark.
> The stream input is [watermark(7) | 6, 5, 3, 4, 1, 2],
> and then two windows are created (3,1,2) (6,5,4) before watermark(7) arriving.
> But in this situation when the current watermark is received,
> which window or how many windows will be be triggered to fire and emit?
> My question is what will the windowOperater do when it comes to two parellel windows edge end timestamps both smaller than cerrent watermark timestamps?