If we only want to have either keyBy or groupBy, why not keep groupBy? That would be more consistent with the batch api. On Tue, Jul 14, 2015 at 10:35 AM Stephan Ewen <se...@apache.org> wrote:
> Concerning your comments: > > 1) In the new design, there is no grouping without windowing. The > KeyedDataStream subsumes the grouping and key-ing for partitioned state. > > The keyBy() + window() makes a parallel grouped window > keyBy() alone allows access to partitioned state. > > My thought was that this is simpler, because it needs not groupBy() and > keyBy(), but one construct to handle both cases. > > 2) The discretization is a rough thought and is nothing for the short term. > It totally needs more thoughts. I put it there to have it as a sketch for > how to evolve this. > > The idea is of course to not have a single data set, but a series of > data set. In each discrete time slice, the data set can be treated like a > regular data set. > > Let's kick off a separate design for the discretization. Joins are good > to talk about (data sets can be joined with data set), and I am sure there > are more questions coming up. > > > Does that make sense? > > > > > > On Tue, Jul 14, 2015 at 10:05 AM, Gyula Fóra <gyula.f...@gmail.com> wrote: > > > I think Marton has some good points here. > > > > 1) Is KeyedDataStream a better name if this is only a renaming? > > > > 2) the discretize semantics is unclear indeed. Are we operating on a > single > > or sequence of datasets? If the latter why not call it something else > > (dstream). How are joins and other binary operators defined for different > > discretizations etc. > > On Mon, Jul 13, 2015 at 7:37 PM Márton Balassi <mbala...@apache.org> > > wrote: > > > > > Generally I agree with the new design. Two concerns: > > > > > > 1) Does KeyedDataStream replace GroupedDataStream or is it the latter a > > > special case of the former? > > > > > > The KeyedDataStream as described in the design document is a bit > unclear > > > for me. It lists the following usages: > > > a) It is the first step in building a window stream, on top of which > > the > > > grouped/windowed aggregation and reduce-style function can be applied > > > b) It allows to use the "by-key" state of functions. Here, every > record > > > has access to a state that is scoped by its key. Key-scoped state can > be > > > automatically redistributed and repartitioned. > > > > > > The code snippet describes a use case where the computation and the > > access > > > of the state is used the way currently the GroupedDataStream should > > work. I > > > suppose this is the example for case b). Would case a) also window > > elements > > > by key? If yes, then this is practically a renaming and enhancement of > > the > > > GroupedDataStream functionality with keyed state. Then the > > > StreamExecutionEnvironment.createKeyedStream(Partitioner, > > > KeySelector)construction does not make much sense as the user only > > operates > > > within the scope of the keyselector and not the partitioner anyway. > > > > > > I personally think KeyedDataStream as a name does not necessarily > suggest > > > that the records are grouped by key, it only suggests partitioning by > > key - > > > at least for me. :) > > > > > > 2) The API for discretization is not convenient IMHO > > > > > > The discretization part declares that the output of > > DataStream.discretize() > > > is a sequence of DataSets. I love this approach, but then in the code > > > snippet the return value of this function is simply a DataSet and uses > it > > > as such. The take home message of that code is the following: this is > > > actually the way you would like to program on these sequence of > DataSets, > > > most probably you would like to do the same with each of them. If that > is > > > the case we should provide a nice utility for that. I think Spark > > > Streaming's DStream.foreachRDD() is fairly useful for this purpose. > > > > > > On Mon, Jul 13, 2015 at 6:30 PM, Gyula Fóra <gyula.f...@gmail.com> > > wrote: > > > > > > > +1 > > > > On Mon, Jul 13, 2015 at 6:23 PM Stephan Ewen <se...@apache.org> > wrote: > > > > > > > > > If naming is the only concern, then we should go ahead, because we > > can > > > > > change names easily (before the release). > > > > > > > > > > In fact, I don't think it leaves a bad impression. Global windows > are > > > > > non-parallel windows. There are also parallel windows. Pick what > you > > > need > > > > > and what works. > > > > > > > > > > > > > > > On Mon, Jul 13, 2015 at 6:13 PM, Gyula Fóra <gyula.f...@gmail.com> > > > > wrote: > > > > > > > > > > > I think we agree on everything its more of a naming issue :) > > > > > > > > > > > > I thought it might be misleading that global time windows are > > > > > > "non-parallel" windows. We dont want to give a bad impression. > > (Also > > > we > > > > > > dont want them to think that every global window is parallel but > > > thats > > > > > not > > > > > > a problem here) > > > > > > > > > > > > Gyula > > > > > > On Mon, Jul 13, 2015 at 5:22 PM Stephan Ewen <se...@apache.org> > > > wrote: > > > > > > > > > > > > > Okay, what is missing about the windowing in your opinion? > > > > > > > > > > > > > > The core points of the document are: > > > > > > > > > > > > > > - The parallel windows are per group only. > > > > > > > > > > > > > > - The implementation of the parallel windows holds window > data > > in > > > > the > > > > > > > group buffers. > > > > > > > > > > > > > > - The global windows are non-parallel. May have parallel > > > > > > pre-aggregation, > > > > > > > if they are time windows. > > > > > > > > > > > > > > - Time may be operator time (timer thread), or watermark > time. > > > > > > Watermark > > > > > > > time can refer to ingress or event time. > > > > > > > > > > > > > > - Windows that do not pre-aggregate may require elements in > > > order. > > > > > Not > > > > > > > part of the first prototype. > > > > > > > > > > > > > > Do we agree on those points? > > > > > > > > > > > > > > > > > > > > > On Mon, Jul 13, 2015 at 4:50 PM, Gyula Fóra < > > gyula.f...@gmail.com> > > > > > > wrote: > > > > > > > > > > > > > > > In general I like it, although the main difference between > the > > > > > current > > > > > > > and > > > > > > > > the new one is the windowing and that is still not very > clear. > > > > > > > > > > > > > > > > Where do we have the full stream time windows for > > instance?(which > > > > is > > > > > > > > parallel but not keyed) > > > > > > > > On Mon, Jul 13, 2015 at 4:28 PM Aljoscha Krettek < > > > > > aljos...@apache.org> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > +1 I like it as well. > > > > > > > > > > > > > > > > > > On Mon, 13 Jul 2015 at 16:17 Kostas Tzoumas < > > > ktzou...@apache.org > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > +1 from my side > > > > > > > > > > > > > > > > > > > > On Mon, Jul 13, 2015 at 4:15 PM, Stephan Ewen < > > > > se...@apache.org> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > Do we have consensus on these designs? > > > > > > > > > > > > > > > > > > > > > > If we have, we should get to implementing this soon, > > > because > > > > > > > > basically > > > > > > > > > > all > > > > > > > > > > > streaming patches will have to be revisited in light of > > > > this... > > > > > > > > > > > > > > > > > > > > > > On Tue, Jul 7, 2015 at 3:41 PM, Gyula Fóra < > > > > > gyula.f...@gmail.com > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > You are right thats an important issue. > > > > > > > > > > > > > > > > > > > > > > > > And I think we should also do some renaming with the > > > > > > "iterations" > > > > > > > > > > because > > > > > > > > > > > > they are not really iterations like in the batch case > > and > > > > it > > > > > > > might > > > > > > > > > > > confuse > > > > > > > > > > > > some users. > > > > > > > > > > > > Maybe we can call them loops or cycles and rename the > > api > > > > > calls > > > > > > > to > > > > > > > > > make > > > > > > > > > > > it > > > > > > > > > > > > more intuitive what happens. It is really just a > cyclic > > > > > > dataflow. > > > > > > > > > > > > > > > > > > > > > > > > Aljoscha Krettek <aljos...@apache.org> ezt írta > > > (időpont: > > > > > > 2015. > > > > > > > > júl. > > > > > > > > > > 7., > > > > > > > > > > > > K, > > > > > > > > > > > > 15:35): > > > > > > > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > I just noticed that we don't have anything about > how > > > > > > iterations > > > > > > > > and > > > > > > > > > > > > > timestamps/watermarks should interact. > > > > > > > > > > > > > > > > > > > > > > > > > > Cheers, > > > > > > > > > > > > > Aljoscha > > > > > > > > > > > > > > > > > > > > > > > > > > On Mon, 6 Jul 2015 at 23:56 Stephan Ewen < > > > > se...@apache.org > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi all! > > > > > > > > > > > > > > > > > > > > > > > > > > > > As many of you know, there are a ongoing efforts > to > > > > > > > consolidate > > > > > > > > > the > > > > > > > > > > > > > > streaming API for the next release, and then > > graduate > > > > it > > > > > > > (from > > > > > > > > > beta > > > > > > > > > > > > > > status). > > > > > > > > > > > > > > > > > > > > > > > > > > > > In the process of this consolidation, we want to > > > > achieve > > > > > > the > > > > > > > > > > > following > > > > > > > > > > > > > > goals. > > > > > > > > > > > > > > > > > > > > > > > > > > > > - Make the code more robust and simplify it in > > parts > > > > > > > > > > > > > > > > > > > > > > > > > > > > - Clearly define the semantics of the > constructs. > > > > > > > > > > > > > > > > > > > > > > > > > > > > - Prepare it for support of more advanced > > concepts, > > > > like > > > > > > > > > > > partitionable > > > > > > > > > > > > > > state, and event time. > > > > > > > > > > > > > > > > > > > > > > > > > > > > - Cut support for certain corner cases that were > > > > > > prototyped, > > > > > > > > but > > > > > > > > > > > > turned > > > > > > > > > > > > > > out to be not efficiently doable > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Based on prior discussions on the mailing list, > > > > Aljoscha > > > > > > and > > > > > > > me > > > > > > > > > > > drafted > > > > > > > > > > > > > the > > > > > > > > > > > > > > design documents below, which outline how the > > > > > consolidated > > > > > > > API > > > > > > > > > > would > > > > > > > > > > > > > like. > > > > > > > > > > > > > > We focused in constructs, time, and window > > semantics. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Design document on how to restructure the > Streaming > > > > API: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/Streams+and+Operations+on+Streams > > > > > > > > > > > > > > > > > > > > > > > > > > > > Design document on definitions of time, order, > and > > > the > > > > > > > > resulting > > > > > > > > > > > > > semantics: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/Time+and+Order+in+Streams > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Note: The design of the interfaces and concepts > for > > > > > > advanced > > > > > > > > > state > > > > > > > > > > in > > > > > > > > > > > > > > functions is not in here. That is part of a > > separate > > > > > design > > > > > > > > > > > discussion > > > > > > > > > > > > > and > > > > > > > > > > > > > > orthogonal to the designs drafted here. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Please have a look and voice questions and > > concerns. > > > > > Since > > > > > > we > > > > > > > > > > should > > > > > > > > > > > > not > > > > > > > > > > > > > > break the streaming API more than once, we should > > > make > > > > > sure > > > > > > > > this > > > > > > > > > > > > > > consolidation brings it into the shape we want it > > to > > > be > > > > > in. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Greetings, > > > > > > > > > > > > > > Stephan > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
