Major Description
In Kafka-streams 3.4.0 :
According to the javadoc of the Joinwindow:
There are three different window configuration supported:
- before = after = time-difference
- before = 0 and after = time-difference
- before = time-difference and after = 0
However if I use a joinWindow with before = time-difference and after = 0
on a kstream-kstream-leftjoin the after=0 part does not seem to work.
When using stream1.leftjoin(stream2, joinWindow) with joinWindow.after=0 and joinWindow.before=30s, any new message on stream 1 that can not be joined with any messages on stream2 should be joined with a null-record after the joinWindow.after has ended and a new message has arrived on stream1.
It does not.
Only if the new message arrives after the value of joinWindow.before the previous message will be joined with a null-record.
Attached you can find two files with a TopologyTestDriver Unit test to reproduce.
topology: stream1.leftjoin( stream2, joiner, joinwindow)
joinWindow has before=5000ms and after=0
message1(key1) -> stream1
after 4000ms message2(key2) -> stream1 -> NO null-record join was made, but the after period was expired.
after 4900ms message2(key2) -> stream1 -> NO null-record join was made, but the after period was expired.
after 5000ms message2(key2) -> stream1 -> A null-record join was made, before period was expired.
after 6000ms message2(key2) -> stream1 -> A null-record join was made, before period was expired.
