That’s convenient, at least for the incremental ML where feedback streams are the norm. In this case we don’t force the user to create wrappers and we also know what comes from where.
I went through the PR and it looks that doesn’t break anything so you have my +1. Paris > On 26 Jun 2015, at 13:35, Gyula Fóra <gyf...@apache.org> wrote: > > Hey! > > Now that we are implementing more and more applications for streaming that > use iterations we realized a huge shortcoming of the current iteration api. > Currently it only allows to feedback data of the same type to the iteration > head. > > This makes sense because the operators are typed but makes it awkward if we > indeed want to use a different feedback (such as a model syncing for > machine learning applications). To do this developers need to use wrapper > types and flags to distinguish the inputs. > > I propose to add the possibility to tread the original input of the > iteration head operator and the feedback stream as a ConnectedDataStream so > we can apply operators such as CoMap, CoFlatMap etc. This helps > distinguishing the inputs and also allows different feedback types to be > used. I believe this change is inevitable if we want to write elegant > applications without unnecessary wrapper types. > > I made a PR <https://github.com/apache/flink/pull/870> already that > introduces this functionality (it is a very small change in fact). > > Cheers, > Gyula
