Hi John,
Thanks for your reply. I am not sure if this behavior I've observed is
a bug or not, as I've not been resetting my application properly. On
the other hand if the subtractor or adder in the reduce operation are
never supposed to be called with null aggregator value, perhaps it
would make s
Hi Rajini,
Thanks for generating the RC. It seems like the kafka-streams-scala 2.12
artifact is missing from the Maven repository:
https://repository.apache.org/content/groups/staging/org/apache/kafka/
Since this is the first time we are publishing this artifact, it is
possible that this never w
Hi again Vasily,
Ok, it looks to me like this behavior is the result of the un-clean
topology change.
Just in case you're interested, here's what I think happened.
1. Your reduce node in subtopology1 (KSTREAM-REDUCE-02 / "table" )
internally emits pairs of "oldValue"/"newValue" . (side-n
Hi John,
Thanks for your explanation.
I have an answer to the practical question, i.e. a null aggregator
value should be interpreted as a fatal application error.
On the other hand, looking at the app topology, I see that a message
from KSTREAM-REDUCE-02 / "table" goes goes to
KTABLE-SEL
Hi Vasily,
I'm glad you're making me look at this; it's good homework for me!
This is very non-obvious, but here's what happens:
KStreamsReduce is a Processor of (K, V) => (K, Change) . I.e., it emits
new/old Change pairs as the value.
Next is the Select (aka GroupBy). In the DSL code, this is
