Count sliding window does not work as expected

[Soheil Pourbafrani <so...@gmail.com>]

Hi,

I need some sliding windowing strategy that fills the window with the count
of 400 and for every 100 incoming data, process the last 400 data. For
example, suppose we have a data stream of count 160000. For count window of
400 and sliding of 100, I expect it output 1597 stream:

160000 - 400 = 159600    // the first output
159600 / 100 = 1596        //  sliding every 100 input data
 overall output = 1596 + 1 = 1597

But calling the Flink built-in count window, count (400, 100), on the keyed
stream, resulted in some strange behavior! Actually, my process is to merge
windowed streams. I expected every output to have 400 merged streams in it,
but in the Flink output, it contains 100 to 1000 merged streams!

Can someone elaborate on how Sliding count window works in Flink?