In Aljoscha's approach, we would need a special mutable stream. We could do it like this:
DataStream source = ... FeedbackPoint pt = source.createFeedbackPoint(); DataStream mapper = pt .map(noOpMapper) DataStream feedback = mapper.filter(...) pt .addFeedbacl(feedback) It is basically like the current approach, with different names. I actually like the current approach, because it is explicit where streams could be altered in hind-sight (after their definition). On Tue, Jul 7, 2015 at 4:20 PM, Gyula Fóra <gyula.f...@gmail.com> wrote: > @Aljoscha: > Yes, thats basically my point as well. This is what happens now too but we > give this mutable datastream a special name : IterativeDataStream > > This can be handled in very different ways through the api, the goal would > be to make something easy to use. I am fine with what we have now because I > know how it works but it might confuse people to call it iterate. > > Aljoscha Krettek <aljos...@apache.org> ezt írta (időpont: 2015. júl. 7., > K, > 16:18): > > > I think it could work if we allowed a DataStream to be unioned after > > creation. For example: > > > > DataStream source = .. > > DataStream mapper = source.map(noOpMapper) > > DataStream feedback = mapper.filter(...) > > source.union(feedback) > > > > This would basically mean that a DataStream is mutable and can be > extended > > after creation with more streams. > > > > On Tue, 7 Jul 2015 at 16:12 Aljoscha Krettek <aljos...@apache.org> > wrote: > > > > > I think this would be good yes. I was just about to open an Issue for > > > changing the Streaming Iteration API. :D > > > > > > Then we should also make the implementation very straightforward and > > > simple, right now, the implementation of the iterations is all over the > > > place. > > > > > > On Tue, 7 Jul 2015 at 15:57 Gyula Fóra <gyf...@apache.org> wrote: > > > > > >> Hey, > > >> > > >> Along with the suggested changes to the streaming API structure I > think > > we > > >> should also rework the "iteration" api. Currently the iteration api > > tries > > >> to mimic the syntax of the batch API while the runtime behaviour is > > quite > > >> different. > > >> > > >> What we create instead of iterations is really just cyclic streams > > (loops > > >> in the streaming job), so the API should somehow be intuitive about > this > > >> behaviour. > > >> > > >> I suggest to remove the explicit iterate call and instead add a method > > to > > >> the StreamOperators that allows to connect feedback inputs (create > > loops). > > >> It would look like this: > > >> > > >> A mapper that does nothing but iterates over some filtered input: > > >> > > >> *Current API :* > > >> DataStream source = .. > > >> IterativeDataStream it = source.iterate() > > >> DataStream mapper = it.map(noOpMapper) > > >> DataStream feedback = mapper.filter(...) > > >> it.closeWith(feedback) > > >> > > >> *Suggested API :* > > >> DataStream source = .. > > >> DataStream mapper = source.map(noOpMapper) > > >> DataStream feedback = mapper.filter(...) > > >> mapper.addInput(feedback) > > >> > > >> The suggested approach would let us define inputs to operators after > > they > > >> are created and implicitly union them with the normal input. This is I > > >> think a much clearer approach than what we have now. > > >> > > >> What do you think? > > >> > > >> Gyula > > >> > > > > > >
