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From Liam Clarke <liam.cla...@adscale.co.nz>
Subject Session Window emitting null values when converted to stream?
Date Mon, 03 Dec 2018 00:59:34 GMT
Hi all,

Using

I am using a session window of 1 minute to detect and prevent duplicated
events within the window using reduce() to preserve the first seen value
and accumulate how often duplicates were seen, I'm then converting the
windowed KTable into a stream to continue processing events.

However, later in the stream, I've been hitting NPEs because after the
window expiry, the stream is emitting a previously seen key with a null
value when I'd assumed any values in the stream would be non-null. Is this
an idiom expressing that the window for that key has expired and as such
needs to be explicitly handled?

I'm worried that my filtering those values from the ongoing stream is
hiding a problem further upstream, but if it's working as designed, then
sweet as.

Kind regards,

Liam Clarke

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