At the current moment, I think John's plan is better than the original plan
described in the KIP. I think we should create a new `Serdes` in another
package. The old one will be deprecated.
- Yuriy
On Fri, May 29, 2020 at 8:58 AM John Roesler <vvcep...@apache.org> wrote:
> Thanks, Matthias,
>
> If we go with the approach Yuriy and I agreed on, to deprecate and replace
> the whole class and not just a few of the methods, then the timeline is
> less of a concern. Under that plan, Yuriy can just write the new class
> exactly the way he wants and people can cleanly swap over to the new
> pattern when they are ready.
>
> The timeline was more significant if we were just going to deprecate some
> methods and add new methods to the existing class. That plan requires two
> implementation phases, where we first deprecate the existing methods and
> later swap the implicits at the same time we remove the deprecated members.
> Aside from the complexity of that approach, it’s not a breakage free path,
> as some users would be forced to continue using the deprecated members
> until a future release drops them, breaking their source code, and only
> then can they update their code.
>
> That wouldn’t be the end of the world, and we’ve had to do the same thing
> in the past with the implicit conversations, but this is a much wider
> scope, since it’s all the serdes. I’m happy with the new plan, since it’s
> not only one step, but also it provides everyone a breakage-free path.
>
> We can still consider dropping the deprecated class in 3.0; I just wanted
> to clarify how the timeline issue has changed.
>
> Thanks,
> John
>
> On Thu, May 28, 2020, at 20:34, Matthias J. Sax wrote:
> > I am not a Scale person, so I cannot really contribute much. However for
> > the deprecation period, if we get the change into 2.7, it might be ok to
> > remove the deprecated classed in 3.0.
> >
> > It would only be one minor release in between what is a little bit short
> > (we usually prefer at least two minor released, better three), but if we
> > have a good reason for it, it might be ok.
> >
> > If we cannot remove it in 3.0, it seems there would be a 4.0 in about a
> > year(?) when ZK removal is finished and we can remove the deprecated
> > code than.
> >
> >
> > -Matthias
> >
> > On 5/28/20 7:39 AM, John Roesler wrote:
> > > Hi Yuriy,
> > >
> > > Sounds good to me! I had a feeling we were bringing different context
> > > to the discussion; thanks for sticking with the conversation until we
> got
> > > it hashed out.
> > >
> > > I'm glad you prefer Serde*s*, since having multiple different classes
> with
> > > the same name leads to all kinds of trouble. "Serdes" seems relatively
> > > safe because people in the Scala lib won't be using the Java Serdes
> class,
> > > and they won't be using the deprecated and non-deprecated one at the
> > > same time.
> > >
> > > Thank again,
> > > -John
> > >
> > > On Thu, May 28, 2020, at 02:21, Yuriy Badalyantc wrote:
> > >> Ok, I understood you, John. I wasn't sure about kafka deprecation
> policy
> > >> and thought that the full cycle could be done with 2.7 version.
> Waiting for
> > >> 3.0 is too much, I agree with it.
> > >>
> > >> So, I think creating one more `Serdes` in another package is our way.
> I
> > >> suggest one of the following:
> > >> 1. `org.apache.kafka.streams.scala.serde.Serdes`
> > >> 2. `org.apache.kafka.streams.scala.serialization.Serdes`
> > >>
> > >> About `Serde` vs `Serdes`. I'm strongly against `Serde` because it
> would
> > >> lead to a new name clash with the
> > >> `org.apache.kafka.common.serialization.Serde`.
> > >>
> > >> - Yuriy
> > >>
> > >> On Thu, May 28, 2020 at 11:12 AM John Roesler <vvcep...@apache.org>
> wrote:
> > >>
> > >>> Hi Yuriy,
> > >>>
> > >>> Thanks for the clarification.
> > >>>
> > >>> I guess my concern is twofold:
> > >>> 1. We typically leave deprecated methods in place for at least a
> major
> > >>> release cycle before removing them, so it would seem abrupt to have a
> > >>> deprecation period of only one minor release. If we follow the same
> pattern
> > >>> here, it would take over a year to finish this KIP.
> > >>> 2. It doesn’t seem like there is a nonbreaking deprecation path at
> all if
> > >>> people enumerate their imports (if they don’t use a wildcard). In
> that
> > >>> case, they would have no path to implicitly use the newly named
> serdes, and
> > >>> therefore they would have no way to avoid continuing to use the
> deprecated
> > >>> ones.
> > >>>
> > >>> Since you mentioned that your reason is mainly the preference for
> the name
> > >>> “Serde” or “Serdes”, can we explore just using one of those? Would
> it cause
> > >>> some kind of conflict to use org.apache.kafka.streams.scala.Serde or
> to use
> > >>> Serdes in a different package, like
> > >>> org.apache.kafka.streams.scala.implicit.Serdes?
> > >>>
> > >>> I empathize with this desire. I faced the same dilemma when I wanted
> to
> > >>> replace Processor but keep the class name in KIP-478. I wound up
> creating a
> > >>> new package for the new Processor.
> > >>>
> > >>> Thanks,
> > >>> John
> > >>>
> > >>> On Wed, May 27, 2020, at 22:20, Yuriy Badalyantc wrote:
> > >>>> Hi John,
> > >>>>
> > >>>> I'm stick with the `org.apache.kafka.streams.scala.Serdes` because
> it's
> > >>>> sort of conventional in the scala community. If you have a typeclass
> > >>> `Foo`,
> > >>>> you probably will search `Foo` related stuff in the `Foo` or maybe
> `Foos`
> > >>>> (plural). All other places are far less discoverable for the
> developers.
> > >>>>
> > >>>> I agree that the migration path is a bit complex for such change.
> But I
> > >>>> think it's more important to provide good developer experience than
> to
> > >>>> simplify migration. Also, I think it's debatable which migration
> path is
> > >>>> better for library users. If we would create, for example,
> `Serdes2`,
> > >>>> library users will have to modify their code if they used any part
> of the
> > >>>> old `Serde`. With my approach, most of the old code will still work
> > >>> without
> > >>>> changes. Only explicit usage of implicits will need to be fixed
> (because
> > >>>> names will be changed, and old names will be deprecated). Wildcard
> > >>> imports
> > >>>> will work without changes and will not lead to a name clash.
> Moreover,
> > >>> many
> > >>>> users may not notice name clash problems. And with my migration
> path,
> > >>> they
> > >>>> will not notice any changes at all.
> > >>>>
> > >>>> - Yuriy
> > >>>>
> > >>>> On Thu, May 28, 2020 at 7:48 AM John Roesler <vvcep...@apache.org>
> > >>> wrote:
> > >>>>
> > >>>>> Hi Yuriy,
> > >>>>>
> > >>>>> Thanks for the reply. I guess I've been out of the Scala game for a
> > >>>>> while; all this summoner business is totally new to me.
> > >>>>>
> > >>>>> I think I followed the rationale you provided, but I still don't
> see
> > >>>>> why you can't implement your whole plan in a new class. What
> > >>>>> is special about the existing Serdes class?
> > >>>>>
> > >>>>> Thanks,
> > >>>>> -John
> > >>>>>
> > >>>>> On Tue, May 19, 2020, at 01:18, Yuriy Badalyantc wrote:
> > >>>>>> Hi John,
> > >>>>>>
> > >>>>>> Your suggestion looks interesting. I think it's technically
> doable.
> > >>> But
> > >>>>> I'm
> > >>>>>> not sure that this is the better solution. I will try to explain.
> > >>> From
> > >>>>> the
> > >>>>>> scala developers' perspective, `Serde` looks really like a
> typeclass.
> > >>>>>> Typical typeclass in pure scala will look like this:
> > >>>>>>
> > >>>>>> ```
> > >>>>>> trait Serde[A] {
> > >>>>>> def serialize(data: A): Array[Byte]
> > >>>>>> def deserialize(data: Array[Byte]): A
> > >>>>>> }
> > >>>>>> object Serde extends DefaultSerdes {
> > >>>>>> // "summoner" function. With this I can write `Serde[A]` and
> this
> > >>> serde
> > >>>>>> will be implicitly summonned.
> > >>>>>> def apply[A](implicit ev: Serde[A]): Serde[A] = ev
> > >>>>>> }
> > >>>>>>
> > >>>>>> trait DefaultSerdes {
> > >>>>>> // default instances here
> > >>>>>> }
> > >>>>>> ```
> > >>>>>>
> > >>>>>> Usage example (note, that there are no wildcards imports here):
> > >>>>>> ```
> > >>>>>> object Main extends App {
> > >>>>>> import Serde // not wildcard import
> > >>>>>>
> > >>>>>> // explicit summonning:
> > >>>>>> val stringSerde = Serde[String] // using summoner
> > >>>>>> stringSerde.serialize(???)
> > >>>>>>
> > >>>>>> // implicit summonning
> > >>>>>> def serialize[A: Serde](a: A) = {
> > >>>>>> Serde[A].serialize(a) // summoner again
> > >>>>>> }
> > >>>>>> serialize("foo")
> > >>>>>> }
> > >>>>>> ```
> > >>>>>>
> > >>>>>> Examples are pretty silly, but I just want to show common
> patterns of
> > >>>>>> working with typeclasses in scala. All default instances in the
> usage
> > >>>>>> examples are found using implicits searching mechanism. Scala
> > >>> compiler
> > >>>>>> searches implicits in a lot of places. Including companion
> objects.
> > >>> In my
> > >>>>>> examples compiler will found `Serde[String]` instance in the
> > >>> companion
> > >>>>>> object of `Serde` typeclass.
> > >>>>>>
> > >>>>>> Also, I want to pay attention to the summoner function. It makes
> > >>> usage of
> > >>>>>> typeclasses very neat and clear.
> > >>>>>>
> > >>>>>> The example above was the example of the perfect solution for the
> > >>> scala
> > >>>>>> developers. But this solution requires to create separate `Serde`
> > >>>>>> typeclass, to make all this implicit searching stuff works. I
> don't
> > >>> think
> > >>>>>> that it worth it, because a lot of code should be reimplemented
> using
> > >>>>> this
> > >>>>>> new typeclass. But the main point of my example is to show the
> > >>> perfect
> > >>>>>> solution. And I think we should strive to provide developer
> > >>> experience
> > >>>>>> close to this.
> > >>>>>>
> > >>>>>> It's a bit out of the scope of my KIP, but I have a plan to make
> > >>>>>> `org.apache.kafka.streams.scala.Serdes` more closer to the
> solution
> > >>>>> above.
> > >>>>>> It could be done in 2 steps:
> > >>>>>> 1. Fix implicit names.
> > >>>>>> 2. Add summoner function.
> > >>>>>>
> > >>>>>> And with this scala developers will be able to write almost the
> same
> > >>> code
> > >>>>>> as in the example above:
> > >>>>>> ```
> > >>>>>> object Main extends App {
> > >>>>>> import org.apache.kafka.streams.scala.Serdes // not wildcard
> import
> > >>>>>>
> > >>>>>> val stringSerde = Serdes[String]
> > >>>>>> stringSerde.serialize(???)
> > >>>>>>
> > >>>>>> def serialize[A: Serde](a: A) = {
> > >>>>>> Serdes[A].serialize(a)
> > >>>>>> }
> > >>>>>> serialize("foo")
> > >>>>>> }
> > >>>>>> ```
> > >>>>>> Of course, wildcard import will still work.
> > >>>>>>
> > >>>>>> Other names will make this new entity (containing default
> implicits)
> > >>> less
> > >>>>>> discoverable. And summoner usage, in this case, will look weird:
> > >>>>>> ```
> > >>>>>> object Main extends App {
> > >>>>>> import org.apache.kafka.streams.scala.DefaultSerdes // not
> wildcard
> > >>>>> import
> > >>>>>>
> > >>>>>> val stringSerde = DefaultSerdes[String]
> > >>>>>> stringSerde.serialize(???)
> > >>>>>>
> > >>>>>> def serialize[A: Serde](a: A) = {
> > >>>>>> DefaultSerdes[A].serialize(a)
> > >>>>>> }
> > >>>>>> serialize("foo")
> > >>>>>> }
> > >>>>>> ```
> > >>>>>>
> > >>>>>> So, I think it's more important to provide a solid and familiar
> > >>> developer
> > >>>>>> experience for the scala developer. And renaming (or creating a
> new
> > >>>>>> version) of `Serdes` will not help here.
> > >>>>>>
> > >>>>>> -Yuriy
> > >>>>>>
> > >>>>>> On Tue, May 19, 2020 at 11:56 AM John Roesler <
> vvcep...@apache.org>
> > >>>>> wrote:
> > >>>>>>
> > >>>>>>> Hi Yuriy,
> > >>>>>>>
> > >>>>>>> Thanks so much for the KIP! I didn’t anticipate the problem you
> > >>> laid
> > >>>>> out
> > >>>>>>> in the KIP, but I find it very plausible.
> > >>>>>>>
> > >>>>>>> Thanks for pushing back on the “convention” and raising the
> issue,
> > >>> and
> > >>>>>>> also volunteering a solution!
> > >>>>>>>
> > >>>>>>> I’m wondering if we can “fix” it in one shot by just deprecating
> > >>> the
> > >>>>> whole
> > >>>>>>> Serdes class and replacing it with a new one containing the defs
> > >>> you
> > >>>>>>> proposed. Then, people could just switch their import to the new
> > >>> one.
> > >>>>>>>
> > >>>>>>> Of course the new class needs to have a different name, which is
> > >>>>> always a
> > >>>>>>> challenge in situations like this, so I might just throw out
> > >>>>> ImplicitSerdes
> > >>>>>>> as an option.
> > >>>>>>>
> > >>>>>>> Do you think this would work?
> > >>>>>>>
> > >>>>>>> Thanks again,
> > >>>>>>> John
> > >>>>>>>
> > >>>>>>> On Mon, May 18, 2020, at 23:35, Yuriy Badalyantc wrote:
> > >>>>>>>> Hi,
> > >>>>>>>>
> > >>>>>>>> I would like to propose KIP-616 to fix naming clash in the kafka
> > >>>>>>>> streams scala API:
> > >>>>>>>>
> > >>>>>>>
> > >>>>>
> > >>>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-616%3A+Rename+implicit+Serdes+instances+in+kafka-streams-scala
> > >>>>>>>>
> > >>>>>>>> Looking forward to your feedback.
> > >>>>>>>>
> > >>>>>>>> -Yuriy
> > >>>>>>>>
> > >>>>>>>
> > >>>>>>
> > >>>>>
> > >>>>
> > >>>
> > >>
> >
> >
> > Attachments:
> > * signature.asc
>
