Hi Christophe, if you don't have a way to recompute the key from the aggregation result, then you have to write an aggregation function which explicitly keeps it (e.g. a tuple value where the first entry is the key and the second the aggregate value).
Cheers, Till On Fri, Jan 5, 2018 at 5:51 PM, Christophe Jolif <cjo...@gmail.com> wrote: > Hi all, > > I'm sourcing from a Kafka topic, using the key of the Kafka message to key > the stream, then doing some aggregation on the keyed stream. > > Now I want to sink back to a different Kafka topic but re-using the same > key. The thing is that my aggregation "lost" the key. Obviously I can make > sure my aggregation function keeps the key, but I find that a bit strange > as it does not relate to aggregation. > > Is there a best practice in that domain? How should the key be carried > when moving from a kafka source to sink but doing some aggregation along > the way? > > Thanks, > -- > Christophe >
