Hi all, Regarding the placement, you might as well move the constants to `org.apache.kafka.clients.CommonClientConfigs`, so that the constants and the configs and the code are in the same module.
Regarding the constructor... What Matthias said is correct: The serde, serializer, and deserializer all need to have zero-arg constructors so they can be instantiated reflectively by Kafka. However, the factory method you proposed "New method public static <T> Serde<List<T>> ListSerde()" is not a constructor, and is not required. It would be used purely from the Java interface, but has the drawbacks I listed above. This method, not the constructor, is what I proposed to remove from the KIP. Thanks, -John On Mon, Jul 15, 2019 at 10:15 AM Development <d...@yeralin.net> wrote: > One problem though. > > Since WindowedSerde (Windowed(De)Serializer) are so similar, I’m trying to > mimic the implementation of my ListSerde accordingly. > > I created couple constants under StreamsConfig: > > > > And trying to do similar construct: > > final String propertyName = isKey ? > StreamsConfig.DEFAULT_LIST_KEY_SERDE_INNER_CLASS : > StreamsConfig.DEFAULT_LIST_VALUE_SERDE_INNER_CLASS; > > But then found out that *StreamsConfig is not accessible* from > *org.apache.kafka.common.serialization* package while window serde > (de)serializers are located under *org.apache.kafka.streams.kstream* > package. > > What should I do? Should I move my classes under > *org.apache.kafka.streams.kstream > *package instead? > > On Jul 15, 2019, at 10:45 AM, Development <d...@yeralin.net> wrote: > > Hi Matthias, > > Thank you for your input. > > I updated the KIP, made it a little more readable. > > I think the configuration parameters strategy is finalized then. > > Do you have any other questions/concerns regarding this KIP? > > Meanwhile I’ll start doing appropriate code changes, and commit them under > my PR. > > Best, > Daniyar Yeralin > > On Jul 11, 2019, at 2:44 PM, Matthias J. Sax <matth...@confluent.io> > wrote: > > Daniyar, > > thanks for the update to the KIP. It's in really good shape and well > written. > > About the default constructor question: > > All Serdes/Serializer/Deserializer classes need a default constructor to > create them easily via reflections when specifies in a config. I > understand that it is not super user friendly, but all existing code > works this way. Hence, it seems best to stick with the established pattern. > > We have a similar issue with `TimeWindowedSerde` and > `SessionWindowedSerde`, and I just recently did a PR to improve user > experience that address the exact issue John raised. (cf > https://github.com/apache/kafka/pull/7067) > > Note, that if a user would instantiate the Serde manually, the user > would also need to call `configure()` to setup the inner serdes. Kafka > Streams would not setup those automatically and one might most likely > end-up with an NPE. > > > Coming back the KIP, and the parameter names. `WindowedSerdes` are > similar to `ListSerde` as they wrap another Serde. For `WindowedSerdes`, > we use the following parameter names: > > - default.windowed.key.serde.inner > - default.windowed.value.serde.inner > > > It might be good to align the naming pattern. I would also suggest to > use `type` instead of `impl`? > > > default.key.list.serde.impl -> default.list.key.serde.type > default.value.list.serde.impl -> default.list.value.serde.type > default.key.list.serde.element -> default.list.key.serde.inner > default.value.list.serde.element -> default.list.value.serde.inner > > > > -Matthias > > > On 7/10/19 8:52 AM, Development wrote: > > Hi John, > > Yes, I do agree. That totally makes sense. The only thing is that it goes > against what Matthias suggested earlier: > "I think that ... `ListSerde` should have an default constructor and it > should be possible to pass in the `Class listClass` information via a > configuration. Otherwise, KafkaStreams cannot use it as default serde.” > > What do you think about that? I hope I’m not confusing anything. > > Best, > Daniyar Yeralin > > On Jul 9, 2019, at 5:56 PM, John Roesler <j...@confluent.io> wrote: > > Ah, my apologies, I must have just overlooked it. Thanks for the update, > too. > > Just one more super-small question, do we need this variant: > > New method public static <T> Serde<List<T>> ListSerde() in > org.apache.kafka.common.serialization.Serdes class (infers list > implementation and inner serde from config file) > > > It seems like this situation implies my config file is already set up for > the list serde, so passing this serde (e.g., in Produced) would have the > same effect as not specifying it. > > I guess that it could be the case that you have the > `default.key/value.serde` set to something else, like StringSerde, but you > still have the `default.key/value.list.serde.impl/element` set. This seems > like it would result in more confusion than convenience, so my gut instinct > is maybe we shouldn't introduce the `ListSerde()` variant until people > actually request it later on. > > Thus, we'd just stick with fully config-driven or fully > source-code-driven, not half/half. > > What do you think? > > Thanks, > -John > > > On Tue, Jul 9, 2019 at 9:58 AM Development <d...@yeralin.net < > mailto:d...@yeralin.net <d...@yeralin.net>>> wrote: > > > Hi John, > > I hope everyone had a great long weekend. > > Regarding Java interfaces, I may not understand you correctly, but I think > I already listed them: > > So for Produced, you would use it in the following fashion, for example: > Produced.keySerde(Serdes.ListSerde(ArrayList.class, Serdes.Integer())) > > I also updated the KIP, and added a section “Serialization Strategy” where > I describe our logic of conditional serialization based on the type of an > inner serde. > > Thank you! > > Best, > Daniyar Yeralin > > On Jun 26, 2019, at 11:44 AM, John Roesler <j...@confluent.io < > mailto:j...@confluent.io <j...@confluent.io>>> wrote: > > Thanks for the update, Daniyar! > > In addition to specifying the config interface, can you also specify > the Java interface? Namely, if I need to pass an instance of this > serde in to the DSL directly, as in Produced, Materialized, etc., what > constructor(s) would I have available? Likewise with the Serializer > and Deserailizer. I don't think you need to specify the implementation > logic, since we've already discussed it here. > > If you also want to specify the serialized format of the data records > in the KIP, it could be useful documentation, as well as letting us > verify the schema for forward/backward compatibility concerns, etc. > > Thanks, > John > > On Wed, Jun 26, 2019 at 10:33 AM Development <d...@yeralin.net < > mailto:d...@yeralin.net <d...@yeralin.net>>> wrote: > > > Hey, > > Finally made updates to the KIP: > https://cwiki.apache.org/confluence/display/KAFKA/KIP-466%3A+Add+support+for+List%3CT%3E+serialization+and+deserialization > < > https://cwiki.apache.org/confluence/display/KAFKA/KIP-466%3A+Add+support+for+List%3CT%3E+serialization+and+deserialization> > < > https://cwiki.apache.org/confluence/display/KAFKA/KIP-466:+Add+support+for+List%3CT%3E+serialization+and+deserialization > < > https://cwiki.apache.org/confluence/display/KAFKA/KIP-466:+Add+support+for+List%3CT%3E+serialization+and+deserialization > >> > Sorry for the delay :) > > Thank You! > > Best, > Daniyar Yeralin > > On Jun 22, 2019, at 12:49 AM, Matthias J. Sax <matth...@confluent.io < > mailto:matth...@confluent.io <matth...@confluent.io>>> wrote: > > Yes, something like this. I did not think about good configuration > parameter names yet. I am also not sure if I understand all proposed > configs atm. But all configs should be listed and explained in the KIP > anyway, and we can discuss further after you have updated the KIP (I can > ask more detailed question if I have any). > > > -Matthias > > On 6/21/19 2:05 PM, Development wrote: > > Yes, you are right. ByteSerializer is not what I need to have in a list > of primitives. > > As for the default constructor and configurability, just want to make > sure. Is this what you have on your mind? > > Best, > Daniyar Yeralin > > > > On Jun 21, 2019, at 2:51 PM, Matthias J. Sax <matth...@confluent.io < > mailto:matth...@confluent.io <matth...@confluent.io>> > <mailto:matth...@confluent.io <matth...@confluent.io> < > mailto:matth...@confluent.io <matth...@confluent.io>>>> wrote: > > Thanks for the update! > > I think that `ListDeserializer`, `ListSerializer`, and `ListSerde` > should have an default constructor and it should be possible to pass in > the `Class listClass` information via a configuration. Otherwise, > KafkaStreams cannot use it as default serde. > > > For the primitive serializers: `BytesSerializer` is not primitive IMHO, > as is it for `byte[]` with variable length -- it's for arrays, not for > single `byte` (note, that `Bytes` is a Kafka class wrapping `byte[]`). > > > For tests, we can comment on the PR. No need to do this in the KIP > discussion. > > > Can you also update the KIP? > > > > -Matthias > > > > > > On 6/21/19 11:29 AM, Development wrote: > > I made and pushed necessary commits, so we could review the final > version under PR https://github.com/apache/kafka/pull/6592 < > https://github.com/apache/kafka/pull/6592> > > I also need some advice on writing tests for this new serde. So far I > only have two test cases (roundtrip and empty payload), I’m not sure > if it is enough. > > Thank y’all for your help in this KIP :) > > Best, > Daniyar Yeralin > > > On Jun 21, 2019, at 1:44 PM, John Roesler <j...@confluent.io < > mailto:j...@confluent.io <j...@confluent.io>> > <mailto:j...@confluent.io <j...@confluent.io> <mailto:j...@confluent.io > <j...@confluent.io>>>> wrote: > > Hey Daniyar, > > Looks good to me! Thanks for considering it. > > Thanks, > -John > > On Fri, Jun 21, 2019 at 9:04 AM Development <d...@yeralin.net < > mailto:d...@yeralin.net <d...@yeralin.net>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>>> wrote: > Hey John and Matthias, > > Yes, now I see it all. I’m storing lots of redundant information. > Here is my final idea. Yes, now a user should pass a list type. I > realized that’s the type is not really needed in ListSerializer, but > only in ListDeserializer: > > > In ListSerializer we will start storing sizes only if serializer is > not a primitive serializer: > > > Then, in deserializer, we persist passed list type, so that during > deserialization we could create an instance of it with predefined > listSize for better performance. > We also try to locate a primitiveSize based on passed deserializer. > If it is not there, then primitiveSize will be null. Which means > that each entry’s size was encoded individually. > > > This looks much cleaner and more concise. > > What do you think? > > Best, > Daniyar Yeralin > > On Jun 20, 2019, at 5:45 PM, Matthias J. Sax <matth...@confluent.io < > mailto:matth...@confluent.io <matth...@confluent.io>> > <mailto:matth...@confluent.io <matth...@confluent.io> < > mailto:matth...@confluent.io <matth...@confluent.io>>> < > mailto:matth...@confluent.io <matth...@confluent.io> < > mailto:matth...@confluent.io <matth...@confluent.io>>>> wrote: > > For encoding the list-type: I see John's point about re-encoding the > list-type redundantly. However, I also don't like the idea that the > Deserializer returns a fixed type... > > Maybe it's best allow users to specify the target list type on > deserialization via config? > > Similar for the primitive types: I don't think we need to encode the > type size, but users could specify the type on the deserializer (via a > config again)? > > > About generics: nesting could be arbitrarily deep. Hence, I doubt > we can > support this and a cast will be necessary at some point in the user > code. > > > > -Matthias > > > > On 6/20/19 1:21 PM, John Roesler wrote: > > Hey Daniyar, > > Thanks for looking at it! > > Something like your screenshot is more along the lines of what I was > thinking. Sorry, but I didn't follow what you mean, how would that not > be "vanilla java"? > > Unfortunately the deserializer needs more information, though. For > example, what if the inner type is a Map<String,String>? The serde > could > only be used to produce a LinkedList<Map>, thus, we'd still need an > inner serde, like you have in the KIP (Serde<T> innerSerde). > > Something more like Serde<LinkedList<MyRecord>> = Serdes.listSerde( > /**list type**/ LinkedList.class, > /**inner serde**/ new MyRecordSerde() > ) > > And in configuration, it's something like: > default.key.serde: org...ListSerde > default.key.list.serde.type: java.util.LinkedList > default.key.list.serde.inner: com.mycompany.MyRecordSerde > > > What do you think? > Thanks, > -John > > On Thu, Jun 20, 2019 at 2:46 PM Development <d...@yeralin.net < > mailto:d...@yeralin.net <d...@yeralin.net>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>>>> wrote: > > Hey John, > > I gave read about TypeReference. It could work for the list serde. > However, it is not directly > supported: > https://github.com/FasterXML/jackson-databind/issues/1490 < > https://github.com/FasterXML/jackson-databind/issues/1490> > <https://github.com/FasterXML/jackson-databind/issues/1490 < > https://github.com/FasterXML/jackson-databind/issues/1490>> > The only way is to pass an actual class object into the constructor, > something like: > > It could be an option, but not a pretty one. What do you think of my > approach to use vanilla java and canonical class name? (As described > previously) > > Best, > Daniyar Yeralin > > On Jun 20, 2019, at 2:45 PM, Development <d...@yeralin.net < > mailto:d...@yeralin.net <d...@yeralin.net>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>>>> wrote: > > Hi John, > > Thank you for your input! Yes, my idea looks a little bit over > engineered :) > > I also wanted to see a feedback from Mathias as well since he gave > me an idea about storing fixed/variable size entries. > > Best, > Daniyar Yeralin > > On Jun 18, 2019, at 6:06 PM, John Roesler <j...@confluent.io < > mailto:j...@confluent.io <j...@confluent.io>> > <mailto:j...@confluent.io <j...@confluent.io> <mailto:j...@confluent.io > <j...@confluent.io>>> <mailto:j...@confluent.io <j...@confluent.io> < > mailto:j...@confluent.io <j...@confluent.io>>> > <mailto:j...@confluent.io <j...@confluent.io> <mailto:j...@confluent.io > <j...@confluent.io>> <mailto:j...@confluent.io <j...@confluent.io> < > mailto:j...@confluent.io <j...@confluent.io>>>>> wrote: > > Hi Daniyar, > > That's a very clever solution! > > One observation is that, now, this is what we might call a > polymorphic > serde. That is, you're detecting the actual concrete type and then > promising to produce the exact same concrete type on read. > There are > some inherent problems with this approach, which in general > require > some kind of schema registry (not necessarily Schema > Registry, just > any registry for schemas) to solve. > > Notice that every serialized record has quite a bit of duplicated > information: the concrete type as well as a byte to indicate > whether > the value type is a fixed size, and, if so, an integer to > indicate the > actual size. These constitute a schema, of sorts, because they > tell us > later how exactly to deserialize the data. Unfortunately, this > information is completely redundant. In all likelihood, the > information will be exactly the same for every record in the > topic. > This problem is essentially the core motivation for serializations > like Avro: to move the schema outside of the serialization > itself, so > that the records won't contain so much redundant information. > > In this light, I'm wondering if it makes sense to go back to > something > like what you had earlier in which you don't support perfectly > preserving the concrete type for _this_ serde, but instead just > support deserializing to _some_ List. Then, you could defer full, > perfect, type preservation to serdes that have an external > system in > which to register their type information. > > There does exist an alternative, if we really do want to > preserve the > concrete type (which does seem kind of nice). You can add a > configuration option specifically for the serde to configure > what the > list type will be, and maybe what the element type is, as well. > > As far as "related work" goes, you might be interested to take > a look > at how Jackson can be configured to deserialize into a specific, > arbitrarily nested, generically parameterized class structure. > Specifically, you might find > > https://fasterxml.github.io/jackson-core/javadoc/2.0.0/com/fasterxml/jackson/core/type/TypeReference.html > < > https://fasterxml.github.io/jackson-core/javadoc/2.0.0/com/fasterxml/jackson/core/type/TypeReference.html > > > < > https://fasterxml.github.io/jackson-core/javadoc/2.0.0/com/fasterxml/jackson/core/type/TypeReference.html > < > https://fasterxml.github.io/jackson-core/javadoc/2.0.0/com/fasterxml/jackson/core/type/TypeReference.html > >> > interesting. > > Thanks, > -John > > On Mon, Jun 17, 2019 at 12:38 PM Development <d...@yeralin.net < > mailto:d...@yeralin.net <d...@yeralin.net>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>> > <mailto:d...@yeralin.net <d...@yeralin.net> <mailto:d...@yeralin.net > <d...@yeralin.net>> <mailto:d...@yeralin.net <d...@yeralin.net> < > mailto:d...@yeralin.net <d...@yeralin.net>>>>> wrote: > > > bump > > > > > > > > > > > > > >
