Hi,
I am in the process of migrating a project from Nifi 1.26 to Nifi 2.0, and I am running into problems around the PublishKafka processor.
Since the processor has seen a major redesign, I've had to reconfigure a couple of things. I was mostly successful, but I noticed my outgoing Kafka messages are missing their key, which used to be set from a flowfile attribute ("kafka.key") in 1.26.
It took me a while to find out how to configure the "Kafka Key" property of the processor in 2.0, but even after doing so, the key continues to be null for all my Kafka messages. According to the documentation, "kafka.key" should be the default attribute to derive the message key from, but neither setting it explicitly, nor leaving "Kafka Key" empty, nor any other configuration so far led to anything other than null as the key of my outgoing Kafka messages.
I had a quick look into the source code to understand what the processor actually does, and I came to the conclusion that setting the message key based on a flowfile attribute requires an impossible to fulfill set of conditions, more specifically the Publish Strategy being set to "Use Wrapper" and NOT being set to "Use Wrapper".
This conclusion might be wrong, since I am not at all familiar with the Nifi source code. I hope this information still helps diagnosing the problem, in case it is actually in the source code.
If the problem is in fact me, mis-configuring the processor, any advice on how to achieve what 1.26 used to do here is appreciated.
Best regards
Jonas Allmann
