And one more comment about the type safety: 7. I'm in favor of the approach of enforcing type safety at compile time, since with Scala's strong typing system I think it makes more sense to get rid of config-based serde specifications that can cause runtime error in the Scala wrapper.
Guozhang On Mon, Mar 19, 2018 at 10:28 AM, Guozhang Wang <wangg...@gmail.com> wrote: > Hello Debasish, > > Thanks for the KIP. Here are some comments: > > 1. About the naming: I'd also vote for option 2 and enforce users to > rename when import since this scenario seems rare to me. > > 2. About the dependency: since this KIP can only be merged as early as > 1.2, it means that for users who wants to use this artifact, say for > version 1.2, she would need to bring in "kafka-streams" version 1.2. In > addition, if we change the Java API in the future versions we'd also need > to update the Scala wrapper at the same version as well, so in other words > "kafka-streams-scala" version X have to be with "kafka-streams" version X > anyways. So I'd suggest we remove the version number in "kafka-streams-scala > only depends on the Scala standard library and Kafka Streams" as it may > be confusing to readers. > > 3. For the KIP discussion, it need be based on the proposed state of this > project in AK. More specifically, for the groupId in maven / gradle, it > need to be "org.apache.kafka"; for the version, it need to be Kafka release > versions, e.g. 1.2.0. > > 4. In "New or Changed Public Interfaces" section, it does not mention the > serde classes like "DefaultSerdes", but I think they should also be > considered public APIs as users would most likely import these in her > implementation. > > 5. Could you also list the changes you'd propose to made to build.gradle > in kafka for adding this artifact? More details will help readers to better > understand your proposal. > > 6. I think it'd will be good to have a WordCount example code as part of > this KIP, to illustrate how to code in this Scala wrapper, e.g. in > o.a.k.scala.examples. But for this class we probably do not need to have a > separate artifact for it as we did in kafka-streams-examples. > > > Guozhang > > > On Mon, Mar 19, 2018 at 9:16 AM, Ted Yu <yuzhih...@gmail.com> wrote: > >> I agree with Sean on name unification. >> >> +1 to option 2. >> >> On Mon, Mar 19, 2018 at 7:23 AM, Sean Glover <sean.glo...@lightbend.com> >> wrote: >> >> > Type names: I vote for option 2. The user must explicitly add a >> dependency >> > to this library and the wrapper types are in a different package. It >> seems >> > reasonable to expect them to do an import rename if there's a need to >> drop >> > down to the Java API. >> > >> > Test Utils: The test utils in kafka-streams-scala are nice and lean, but >> > I'm not sure if it provides much more value than other options that >> exist >> > in the community. There's an embedded Kafka/ZK project implementation >> for >> > ScalaTest that's popular and active: manub/scalatest-embedded-kakfa. >> It >> > implies you must also use ScalaTest, which I acknowledge isn't >> everyone's >> > first choice for Scala test framework, but it probably is one of, if not >> > the most, popular library. It includes a DSL for Kafka Streams too. If >> > this KIP is accepted then perhaps a PR to that project could be made to >> > support the new wrapper implementations. >> > >> > https://github.com/manub/scalatest-embedded-kafka# >> > scalatest-embedded-kafka-streams >> > >> > Sean >> > >> > On Sun, Mar 18, 2018 at 4:05 AM, Debasish Ghosh < >> > debasish.gh...@lightbend.com> wrote: >> > >> > > > >> > > > > Should this be 1.2 (maybe it's even better to not put any >> version at >> > > > all) >> > > >> > > >> > > Actually wanted to emphasize that the support is from 1.0.0 onwards .. >> > > Should we make that explicit ? Like .. >> > > >> > > kafka-streams-scala only depends on the Scala standard library and >> Kafka >> > > > Streams 1.0.0+. >> > > >> > > >> > > In 1.1 release, we add a new module `kafka-streams-test-utils` to >> > simplify >> > > > testing for Kafka Streams applications. Are those test utils >> suitable >> > for >> > > > Scala users or should we add Scala wrappers for those, too? >> > > >> > > >> > > I will check up and let you know .. >> > > >> > > Also I am not clear about the decision on renaming of Scala >> abstractions. >> > > Can we have a consensus on this ? Here's the summary .. >> > > >> > > *Option 1:* Keep names separate (KStream for Java class, KStreamS for >> > > Scala). No renaming of imports required. >> > > *Option 2:* Unify names (KStream for Java and Scala class names). No >> > > conflict since they will reside in different packages. But if we need >> to >> > > use both abstractions, renaming of imports are required. But again, >> this >> > > may not be a too frequent use case. >> > > >> > > Suggestions ? >> > > >> > > regards. >> > > >> > > On Sat, Mar 17, 2018 at 3:07 AM, Matthias J. Sax < >> matth...@confluent.io> >> > > wrote: >> > > >> > > > Thanks a lot for the KIP! Two questions: >> > > > >> > > > 1) the KIP states: >> > > > >> > > > > kafka-streams-scala only depends on the Scala standard library and >> > > Kafka >> > > > Streams 1.0.0. >> > > > >> > > > Should this be 1.2 (maybe it's even better to not put any version >> at >> > > all) >> > > > >> > > > >> > > > 2) In 1.1 release, we add a new module `kafka-streams-test-utils` to >> > > > simplify testing for Kafka Streams applications. Are those test >> utils >> > > > suitable for Scala users or should we add Scala wrappers for those, >> > too? >> > > > >> > > > >> > > > -Matthias >> > > > >> > > > >> > > > On 3/16/18 11:10 AM, Ted Yu wrote: >> > > > > Import renames seem to be fine. >> > > > > >> > > > > The class names with trailing 'S' look clean. >> > > > > >> > > > > Cheers >> > > > > >> > > > > On Fri, Mar 16, 2018 at 11:04 AM, Ismael Juma <ism...@juma.me.uk> >> > > wrote: >> > > > > >> > > > >> If this is rare (as it sounds), relying on import renames seems >> fine >> > > to >> > > > me. >> > > > >> Let's see what others think. >> > > > >> >> > > > >> Ismael >> > > > >> >> > > > >> On Fri, Mar 16, 2018 at 10:51 AM, Debasish Ghosh < >> > > > >> debasish.gh...@lightbend.com> wrote: >> > > > >> >> > > > >>> I am not sure if this is practical or not. But theoretically a >> user >> > > may >> > > > >>> want to extract the unsafe Java abstraction from the Scala ones >> and >> > > use >> > > > >>> Java APIs on them .. e.g. >> > > > >>> >> > > > >>> val userClicksStream: KStreamS[String, Long] = >> > > > >>> builder.stream(userClicksTopic) // Scala abstraction >> > > > >>> >> > > > >>> val jStream: KStream[String, Long] = userClicksStream.inner // >> > > > publishes >> > > > >>> the underlying Java abstraction >> > > > >>> >> > > > >>> //.. work with Java, may be pass to some function written in >> Java >> > > > >>> >> > > > >>> I do realize this is somewhat of a convoluted use case and may >> not >> > be >> > > > >>> practically useful .. >> > > > >>> >> > > > >>> Otherwise we can very well work on the suggested approach of >> > unifying >> > > > the >> > > > >>> names .. >> > > > >>> >> > > > >>> regards. >> > > > >>> >> > > > >>> >> > > > >>> >> > > > >>> On Fri, Mar 16, 2018 at 10:28 PM, Ismael Juma < >> ism...@juma.me.uk> >> > > > wrote: >> > > > >>> >> > > > >>>> What does "mixed mode application" mean? What are the cases >> where >> > a >> > > > >> user >> > > > >>>> would want to use both APIs? I think that would help understand >> > the >> > > > >>>> reasoning. >> > > > >>>> >> > > > >>>> Thanks, >> > > > >>>> Ismael >> > > > >>>> >> > > > >>>> On Fri, Mar 16, 2018 at 8:48 AM, Debasish Ghosh < >> > > > >>>> debasish.gh...@lightbend.com> wrote: >> > > > >>>> >> > > > >>>>> Hi Damian - >> > > > >>>>> >> > > > >>>>> We could. But in case the user wants to use both Scala and >> Java >> > > APIs >> > > > >>> (may >> > > > >>>>> be for some mixed mode application), won't that be confusing ? >> > She >> > > > >> will >> > > > >>>>> have to do something like .. >> > > > >>>>> >> > > > >>>>> import o.a.k.s.scala.{KStream => KStreamS} >> > > > >>>>> >> > > > >>>>> to rename Scala imports or the other way round for imported >> Java >> > > > >>> classes. >> > > > >>>>> >> > > > >>>>> regards. >> > > > >>>>> >> > > > >>>>> >> > > > >>>>> >> > > > >>>>> On Fri, Mar 16, 2018 at 9:07 PM, Damian Guy < >> > damian....@gmail.com> >> > > > >>>> wrote: >> > > > >>>>> >> > > > >>>>>> Hi Debasish, >> > > > >>>>>> >> > > > >>>>>> Thanks for the KIP - will be a great addition to streams. >> I've >> > > only >> > > > >>>> had a >> > > > >>>>>> quick scan, but seeing as the Scala classes are going to be >> in >> > > > >> their >> > > > >>>> own >> > > > >>>>>> package could we drop the S at the end of the class names? >> > > > >>>>>> >> > > > >>>>>> Thanks, >> > > > >>>>>> Damian >> > > > >>>>>> >> > > > >>>>>> >> > > > >>>>>> On Fri, 16 Mar 2018 at 15:25 Debasish Ghosh < >> > > > >>>>> debasish.gh...@lightbend.com> >> > > > >>>>>> wrote: >> > > > >>>>>> >> > > > >>>>>>> Hi - >> > > > >>>>>>> >> > > > >>>>>>> A new KIP, KIP-270 is up for discussion: >> > > > >>>>>>> >> > > > >>>>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP- >> > > > >>>>>> 270+-+A+Scala+Wrapper+Library+for+Kafka+Streams >> > > > >>>>>>> >> > > > >>>>>>> The relevant JIRA issue: https://issues.apache.org/ >> > > > >>>>>> jira/browse/KAFKA-6670 >> > > > >>>>>>> >> > > > >>>>>>> The library as proposed in the KIP has been implemented at >> > > > >>>>>>> https://github.com/lightbend/kafka-streams-scala and the >> > current >> > > > >>>>> release >> > > > >>>>>>> is >> > > > >>>>>>> 0.2.0 ( >> > > > >>>>>>> https://github.com/lightbend/kafka-streams-scala/releases/ >> > > > >>> tag/v0.2.0 >> > > > >>>> ). >> > > > >>>>>>> We at Lightbend has been using it since quite some time now. >> > > > >>>>>>> >> > > > >>>>>>> regards. >> > > > >>>>>>> >> > > > >>>>>>> -- >> > > > >>>>>>> Debasish Ghosh >> > > > >>>>>>> Principal Engineer >> > > > >>>>>>> >> > > > >>>>>>> Twitter: @debasishg >> > > > >>>>>>> Blog: http://debasishg.blogspot.com >> > > > >>>>>>> Code: https://github.com/debasishg >> > > > >>>>>>> >> > > > >>>>>> >> > > > >>>>> >> > > > >>>>> >> > > > >>>>> >> > > > >>>>> -- >> > > > >>>>> Debasish Ghosh >> > > > >>>>> Principal Engineer >> > > > >>>>> >> > > > >>>>> Twitter: @debasishg >> > > > >>>>> Blog: http://debasishg.blogspot.com >> > > > >>>>> Code: https://github.com/debasishg >> > > > >>>>> >> > > > >>>> >> > > > >>> >> > > > >>> >> > > > >>> >> > > > >>> -- >> > > > >>> Debasish Ghosh >> > > > >>> Principal Engineer >> > > > >>> >> > > > >>> Twitter: @debasishg >> > > > >>> Blog: http://debasishg.blogspot.com >> > > > >>> Code: https://github.com/debasishg >> > > > >>> >> > > > >> >> > > > > >> > > > >> > > > >> > > >> > > >> > > -- >> > > Debasish Ghosh >> > > Principal Engineer >> > > >> > > Twitter: @debasishg >> > > Blog: http://debasishg.blogspot.com >> > > Code: https://github.com/debasishg >> > > >> > >> > >> > >> > -- >> > Senior Software Engineer, Lightbend, Inc. >> > >> > <http://lightbend.com> >> > >> > @seg1o <https://twitter.com/seg1o>, in/seanaglover >> > <https://www.linkedin.com/in/seanaglover/> >> > >> > > > > -- > -- Guozhang > -- -- Guozhang
