The only hook I see for specifying a TimestampExtractor is in the Properties that you pass when creating a KafkaStreams instance. Is it possible to modify the timestamp while processing a stream, or does the timestamp need to be extracted immediately upon entry into the topology?
I have a case where I'm creating a KStream from a topic with mostly JSON-formatted messages. I need to deserialize as byte array, filter out non-JSON messages, call .map on the stream to deserialize those objects into desired POJOs, and only then reach into the objects to extract the desired timestamp. Workarounds I've imagined are either to define a TimestampExtractor that attempts to do some partial deserialization of the payload to get at the timestamp field; or, to create two separate topologies, with the second one reading a topic that's already filtered.
