Database Reference
In-Depth Information
Window operators
As Spark Streaming operates on time-ordered batched streams of data, it introduces a new
concept, which is that of
windowing
. A
window
function computes a transformation
over a sliding window applied to the stream.
A window is defined by the length of the window and the sliding interval. For example,
with a 10-second window and a 5-second sliding interval, we will compute results every 5
seconds, based on the latest 10 seconds of data in the DStream. For example, we might
wish to calculate the top websites by page view numbers over the last 10 seconds and re-
compute this metric every 5 seconds using a sliding window.
The following figure illustrates a windowed DStream:
A windowed DStream
