[DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hello,

Starting a discussion for KIP-466 adding support for List Serde. PR is created 
under https://github.com/apache/kafka/pull/6592 


There are two topics I would like to discuss:
1. Since type for List serve needs to be declared before hand, I could not 
create a static method for List Serde under 
org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP: 
P.S. Static method corresponding to ListSerde under 
org.apache.kafka.common.serialization.Serdes (something like static public 
Serde> List() {...} inorg.apache.kafka.common.serialization.Serdes) 
class cannot be added because type needs to be defined beforehand. That's why 
one needs to create List Serde in the following fashion:
new Serdes.ListSerde(Serdes.String(), 
Comparator.comparing(String::length));
(can possibly be simplified by declaring import static 
org.apache.kafka.common.serialization.Serdes.ListSerde)

2. @miguno Michael G. Noll  is questioning whether I 
need to pass a comparator to ListDeserializer. This certainly is not required. 
Feel free to add your input:
https://github.com/apache/kafka/pull/6592#discussion_r281152067

Thank you!

Best,
Daniyar Yeralin

> On May 6, 2019, at 11:59 AM, Daniyar Yeralin (JIRA)  wrote:
> 
> Daniyar Yeralin created KAFKA-8326:
> --
> 
> Summary: Add List Serde
> Key: KAFKA-8326
> URL: https://issues.apache.org/jira/browse/KAFKA-8326
> Project: Kafka
>  Issue Type: Improvement
>  Components: clients, streams
>Reporter: Daniyar Yeralin
> 
> 
> I propose adding serializers and deserializers for the java.util.List class.
> 
> I have many use cases where I want to set the key of a Kafka message to be a 
> UUID. Currently, I need to turn UUIDs into strings or byte arrays and use 
> their associated Serdes, but it would be more convenient to serialize and 
> deserialize UUIDs directly.
> 
> I believe there are many use cases where one would want to have a List serde. 
> Ex. 
> [https://stackoverflow.com/questions/41427174/aggregate-java-objects-in-a-list-with-kafka-streams-dsl-windows],
>  
> [https://stackoverflow.com/questions/46365884/issue-with-arraylist-serde-in-kafka-streams-api]
> 
>  
> 
> KIP Link: 
> [https://cwiki.apache.org/confluence/display/KAFKA/KIP-466%3A+Add+support+for+List%3CT%3E+serialization+and+deserialization]
> 
> 
> 
> --
> This message was sent by Atlassian JIRA
> (v7.6.3#76005)

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi John,

I’m really sorry for the confusion. I cloned that JIRA ticket from an old one 
about introducing UUID Serde, and I guess was too hasty while editing the copy 
to notice the mistake. Just edited the ticket. Sorry for any inconvenience .

As per comparator, I agree. Let’s make user be responsible for implementing 
comparable interface. I was just thinking to make the serde a little more 
flexible (i.e. let user decide in which order records is going to be inserted 
into a change log topic).

Thank you!

Best,
Daniyar Yeralin


> On May 6, 2019, at 5:37 PM, John Roesler  wrote:
> 
> Hi Daniyar,
> 
> Thanks for the proposal!
> 
> If I understand the point about the comparator, is it just to capture the
> generic type parameter? If so, then anything that implements a known
> interface would work just as well, right? I've been considering adding
> something like the Jackson TypeReference (or similar classes in many other
> projects). Would this be a good time to do it?
> 
> Note that it's not necessary to actually require that the captured type is
> Comparable (as this proposal currently does), it's just a way to make sure
> there is some method that makes use of the generic type parameter, to force
> the compiler to capture the type.
> 
> Just to make sure I understand the motivation... You expressed a desire to
> be able to serialize UUIDs, which I didn't follow, since there is a
> built-in UUID serde: org.apache.kafka.common.serialization.Serdes#UUID, and
> also, a UUID isn't a List. Did you mean that you need to use *lists of*
> UUIDs?
> 
> Thanks,
> -John
> 
> On Mon, May 6, 2019 at 11:49 AM Development  wrote:
> 
>> Hello,
>> 
>> Starting a discussion for KIP-466 adding support for List Serde. PR is
>> created under https://github.com/apache/kafka/pull/6592 <
>> https://github.com/apache/kafka/pull/6592>
>> 
>> There are two topics I would like to discuss:
>> 1. Since type for List serve needs to be declared before hand, I could not
>> create a static method for List Serde under
>> org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP:
>> P.S. Static method corresponding to ListSerde under
>> org.apache.kafka.common.serialization.Serdes (something like static public
>> Serde> List() {...} inorg.apache.kafka.common.serialization.Serdes)
>> class cannot be added because type needs to be defined beforehand. That's
>> why one needs to create List Serde in the following fashion:
>> new Serdes.ListSerde(Serdes.String(),
>> Comparator.comparing(String::length));
>> (can possibly be simplified by declaring import static
>> org.apache.kafka.common.serialization.Serdes.ListSerde)
>> 
>> 2. @miguno Michael G. Noll <https://github.com/miguno> is questioning
>> whether I need to pass a comparator to ListDeserializer. This certainly is
>> not required. Feel free to add your input:
>> https://github.com/apache/kafka/pull/6592#discussion_r281152067
>> 
>> Thank you!
>> 
>> Best,
>> Daniyar Yeralin
>> 
>>> On May 6, 2019, at 11:59 AM, Daniyar Yeralin (JIRA) 
>> wrote:
>>> 
>>> Daniyar Yeralin created KAFKA-8326:
>>> --
>>> 
>>>Summary: Add List Serde
>>>Key: KAFKA-8326
>>>URL: https://issues.apache.org/jira/browse/KAFKA-8326
>>>Project: Kafka
>>> Issue Type: Improvement
>>> Components: clients, streams
>>>   Reporter: Daniyar Yeralin
>>> 
>>> 
>>> I propose adding serializers and deserializers for the java.util.List
>> class.
>>> 
>>> I have many use cases where I want to set the key of a Kafka message to
>> be a UUID. Currently, I need to turn UUIDs into strings or byte arrays and
>> use their associated Serdes, but it would be more convenient to serialize
>> and deserialize UUIDs directly.
>>> 
>>> I believe there are many use cases where one would want to have a List
>> serde. Ex. [
>> https://stackoverflow.com/questions/41427174/aggregate-java-objects-in-a-list-with-kafka-streams-dsl-windows],
>> [
>> https://stackoverflow.com/questions/46365884/issue-with-arraylist-serde-in-kafka-streams-api
>> ]
>>> 
>>> 
>>> 
>>> KIP Link: [
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-466%3A+Add+support+for+List%3CT%3E+serialization+and+deserialization
>> ]
>>> 
>>> 
>>> 
>>> --
>>> This message was sent by Atlassian JIRA
>>> (v7.6.3#76005)
>> 
>> 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Absolutely agree. Already pushed another commit to remove comparator argument: 
https://github.com/apache/kafka/pull/6592 
<https://github.com/apache/kafka/pull/6592>

Thank you for your input John! I really appreciate it.

What about this point I made:

1. Since type for List serde needs to be declared before hand, I could not 
create a static method for List Serde under 
org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP: 
P.S. Static method corresponding to ListSerde under 
org.apache.kafka.common.serialization.Serdes (something like static public 
Serde> List() {...} inorg.apache.kafka.common.serialization.Serdes) 
class cannot be added because type needs to be defined beforehand. That's why 
one needs to create List Serde in the following fashion:
new Serdes.ListSerde(Serdes.String(), 
Comparator.comparing(String::length));
(can possibly be simplified by declaring import static 
org.apache.kafka.common.serialization.Serdes.ListSerde)

> On May 7, 2019, at 11:50 AM, John Roesler  wrote:
> 
> Thanks for the reply Daniyar,
> 
> That makes much more sense! I thought I must be missing something, but I
> couldn't for the life of me figure it out.
> 
> What do you think about just taking an argument, instead of for a
> Comparator, for the Serde of the inner type? That way, the user can control
> how exactly the inner data gets serialized, while also bounding the generic
> parameter properly. As for the order, since the list is already in a
> specific order, which the user themselves controls, it doesn't seem
> strictly necessary to offer an option to sort the data during serialization.
> 
> Thanks,
> -John
> 
> On Mon, May 6, 2019 at 8:47 PM Development  wrote:
> 
>> Hi John,
>> 
>> I’m really sorry for the confusion. I cloned that JIRA ticket from an old
>> one about introducing UUID Serde, and I guess was too hasty while editing
>> the copy to notice the mistake. Just edited the ticket. Sorry for any
>> inconvenience .
>> 
>> As per comparator, I agree. Let’s make user be responsible for
>> implementing comparable interface. I was just thinking to make the serde a
>> little more flexible (i.e. let user decide in which order records is going
>> to be inserted into a change log topic).
>> 
>> Thank you!
>> 
>> Best,
>> Daniyar Yeralin
>> 
>> 
>>> On May 6, 2019, at 5:37 PM, John Roesler  wrote:
>>> 
>>> Hi Daniyar,
>>> 
>>> Thanks for the proposal!
>>> 
>>> If I understand the point about the comparator, is it just to capture the
>>> generic type parameter? If so, then anything that implements a known
>>> interface would work just as well, right? I've been considering adding
>>> something like the Jackson TypeReference (or similar classes in many
>> other
>>> projects). Would this be a good time to do it?
>>> 
>>> Note that it's not necessary to actually require that the captured type
>> is
>>> Comparable (as this proposal currently does), it's just a way to make
>> sure
>>> there is some method that makes use of the generic type parameter, to
>> force
>>> the compiler to capture the type.
>>> 
>>> Just to make sure I understand the motivation... You expressed a desire
>> to
>>> be able to serialize UUIDs, which I didn't follow, since there is a
>>> built-in UUID serde: org.apache.kafka.common.serialization.Serdes#UUID,
>> and
>>> also, a UUID isn't a List. Did you mean that you need to use *lists of*
>>> UUIDs?
>>> 
>>> Thanks,
>>> -John
>>> 
>>> On Mon, May 6, 2019 at 11:49 AM Development  wrote:
>>> 
>>>> Hello,
>>>> 
>>>> Starting a discussion for KIP-466 adding support for List Serde. PR is
>>>> created under https://github.com/apache/kafka/pull/6592 <
>>>> https://github.com/apache/kafka/pull/6592>
>>>> 
>>>> There are two topics I would like to discuss:
>>>> 1. Since type for List serve needs to be declared before hand, I could
>> not
>>>> create a static method for List Serde under
>>>> org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP:
>>>> P.S. Static method corresponding to ListSerde under
>>>> org.apache.kafka.common.serialization.Serdes (something like static
>> public
>>>> Serde> List() {...}
>> inorg.apache.kafka.common.serialization.Serdes)
>>>> class cannot be added because type needs to be defined beforehand.
>> That's
>>>> why one needs 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi John,

I updated JIRA and KIP.

I didn’t know about the process, and created PR before I knew about KIPs :) 

As per static declaration, I don’t think Java allows that:


Best,
Daniyar Yeralin

> On May 7, 2019, at 2:22 PM, John Roesler  wrote:
> 
> Thanks for that update. Do you mind making changes primarily on the
> KIP document ? 
> (https://cwiki.apache.org/confluence/display/KAFKA/KIP-466%3A+Add+support+for+List%3CT%3E+serialization+and+deserialization)
> 
> This is the design document that we have to agree on and vote for, the
> PR comes later. It can be nice to have an implementation to look at,
> but the KIP is the main artifact for this discussion.
> 
> With this in mind, it will help get more reviewers to look at it if
> you can tidy up the KIP document so that it stands on its own. People
> shouldn't have to look at any other document to understand the
> motivation of the proposal, and they shouldn't have to look at a PR to
> see what the public API will look like. If it helps, you can take a
> look at some other recent KIPs.
> 
> Given that the list serde needs an inner serde, I agree you can't have
> a zero-argument static factory method for it, but it seems you could
> still have a static method:
> `public static Serde> List(Serde innerSerde)`.
> 
> Thoughts?
> 
> On Tue, May 7, 2019 at 12:18 PM Development  wrote:
>> 
>> Absolutely agree. Already pushed another commit to remove comparator 
>> argument: https://github.com/apache/kafka/pull/6592 
>> <https://github.com/apache/kafka/pull/6592>
>> 
>> Thank you for your input John! I really appreciate it.
>> 
>> What about this point I made:
>> 
>> 1. Since type for List serde needs to be declared before hand, I could not 
>> create a static method for List Serde under 
>> org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP:
>> P.S. Static method corresponding to ListSerde under 
>> org.apache.kafka.common.serialization.Serdes (something like static public 
>> Serde> List() {...} inorg.apache.kafka.common.serialization.Serdes) 
>> class cannot be added because type needs to be defined beforehand. That's 
>> why one needs to create List Serde in the following fashion:
>> new Serdes.ListSerde(Serdes.String(), 
>> Comparator.comparing(String::length));
>> (can possibly be simplified by declaring import static 
>> org.apache.kafka.common.serialization.Serdes.ListSerde)
>> 
>>> On May 7, 2019, at 11:50 AM, John Roesler  wrote:
>>> 
>>> Thanks for the reply Daniyar,
>>> 
>>> That makes much more sense! I thought I must be missing something, but I
>>> couldn't for the life of me figure it out.
>>> 
>>> What do you think about just taking an argument, instead of for a
>>> Comparator, for the Serde of the inner type? That way, the user can control
>>> how exactly the inner data gets serialized, while also bounding the generic
>>> parameter properly. As for the order, since the list is already in a
>>> specific order, which the user themselves controls, it doesn't seem
>>> strictly necessary to offer an option to sort the data during serialization.
>>> 
>>> Thanks,
>>> -John
>>> 
>>> On Mon, May 6, 2019 at 8:47 PM Development  wrote:
>>> 
>>>> Hi John,
>>>> 
>>>> I’m really sorry for the confusion. I cloned that JIRA ticket from an old
>>>> one about introducing UUID Serde, and I guess was too hasty while editing
>>>> the copy to notice the mistake. Just edited the ticket. Sorry for any
>>>> inconvenience .
>>>> 
>>>> As per comparator, I agree. Let’s make user be responsible for
>>>> implementing comparable interface. I was just thinking to make the serde a
>>>> little more flexible (i.e. let user decide in which order records is going
>>>> to be inserted into a change log topic).
>>>> 
>>>> Thank you!
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>>> 
>>>> 
>>>>> On May 6, 2019, at 5:37 PM, John Roesler  wrote:
>>>>> 
>>>>> Hi Daniyar,
>>>>> 
>>>>> Thanks for the proposal!
>>>>> 
>>>>> If I understand the point about the comparator, is it just to capture the
>>>>> generic type parameter? If so, then anything that implements a known
>>>>> interface would work just as well, right? I've been considering adding
>>>>> something like the Jackson TypeReference (or 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey,

That worked! I certainly lack Java generics knowledge. Thanks for the snippet. 
I’ll update KIP again.

Best,
Daniyar Yeralin

> On May 8, 2019, at 1:39 PM, Chris Egerton  wrote:
> 
> Hi Daniyar,
> 
> I think you may want to tweak your syntax a little:
> 
> public static  Serde> List(Serde innerSerde) {
>   return new ListSerde(innerSerde);
> }
> 
> Does that work?
> 
> Cheers,
> 
> Chris
> 
> On Wed, May 8, 2019 at 10:29 AM Development  <mailto:d...@yeralin.net>> wrote:
> Hi John,
> 
> I updated JIRA and KIP.
> 
> I didn’t know about the process, and created PR before I knew about KIPs :) 
> 
> As per static declaration, I don’t think Java allows that:
> 
> 
> Best,
> Daniyar Yeralin
> 
>> On May 7, 2019, at 2:22 PM, John Roesler > <mailto:j...@confluent.io>> wrote:
>> 
>> Thanks for that update. Do you mind making changes primarily on the
>> KIP document ? 
>> (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>)
>> 
>> This is the design document that we have to agree on and vote for, the
>> PR comes later. It can be nice to have an implementation to look at,
>> but the KIP is the main artifact for this discussion.
>> 
>> With this in mind, it will help get more reviewers to look at it if
>> you can tidy up the KIP document so that it stands on its own. People
>> shouldn't have to look at any other document to understand the
>> motivation of the proposal, and they shouldn't have to look at a PR to
>> see what the public API will look like. If it helps, you can take a
>> look at some other recent KIPs.
>> 
>> Given that the list serde needs an inner serde, I agree you can't have
>> a zero-argument static factory method for it, but it seems you could
>> still have a static method:
>> `public static Serde> List(Serde innerSerde)`.
>> 
>> Thoughts?
>> 
>> On Tue, May 7, 2019 at 12:18 PM Development > <mailto:d...@yeralin.net>> wrote:
>>> 
>>> Absolutely agree. Already pushed another commit to remove comparator 
>>> argument: https://github.com/apache/kafka/pull/6592 
>>> <https://github.com/apache/kafka/pull/6592> 
>>> <https://github.com/apache/kafka/pull/6592 
>>> <https://github.com/apache/kafka/pull/6592>>
>>> 
>>> Thank you for your input John! I really appreciate it.
>>> 
>>> What about this point I made:
>>> 
>>> 1. Since type for List serde needs to be declared before hand, I could not 
>>> create a static method for List Serde under 
>>> org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP:
>>> P.S. Static method corresponding to ListSerde under 
>>> org.apache.kafka.common.serialization.Serdes (something like static public 
>>> Serde> List() {...} inorg.apache.kafka.common.serialization.Serdes) 
>>> class cannot be added because type needs to be defined beforehand. That's 
>>> why one needs to create List Serde in the following fashion:
>>> new Serdes.ListSerde(Serdes.String(), 
>>> Comparator.comparing(String::length));
>>> (can possibly be simplified by declaring import static 
>>> org.apache.kafka.common.serialization.Serdes.ListSerde)
>>> 
>>>> On May 7, 2019, at 11:50 AM, John Roesler >>> <mailto:j...@confluent.io>> wrote:
>>>> 
>>>> Thanks for the reply Daniyar,
>>>> 
>>>> That makes much more sense! I thought I must be missing something, but I
>>>> couldn't for the life of me figure it out.
>>>> 
>>>> What do you think about just taking an argument, instead of for a
>>>> Comparator, for the Serde of the inner type? That way, the user can control
>>>> how exactly the inner data gets serialized, while also bounding the generic
>>>> parameter properly. As for the order, since the list is already in a
>>>> specific order, which the user themselves controls, it doesn't seem
>>>> strictly necessary to offer an option to sort the data during 
>>>> serialization.
>>>> 
>>>> Thanks,
>>>> -John
>>>> 
>>>> On Mon, May 6, 2019 at 8:47 PM Development >>> <mailto:d...@yeralin.net>> wrote:
>>>> 
>>>>> Hi John,
>>>>> 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey,

I don’t see any replies. Seems like this proposal can be finalized and called 
for a vote?

Also I’ve been thinking. Do we need more serdes for other Collections? Like 
queue or set for example

Best,
Daniyar Yeralin

> On May 8, 2019, at 2:28 PM, John Roesler  wrote:
> 
> Hi Daniyar,
> 
> No worries about the procedural stuff. Prior experience with KIPs is
> not required :)
> 
> I was just trying to help you propose this stuff in a way that the
> others will find easy to review.
> 
> Thanks for updating the KIP. Thanks to the others for helping out with
> the syntax.
> 
> Given these updates, I'm curious if anyone else has feedback about
> this proposal. Personally, I think it sounds fine!
> 
> -John
> 
> On Wed, May 8, 2019 at 1:01 PM Development  wrote:
>> 
>> Hey,
>> 
>> That worked! I certainly lack Java generics knowledge. Thanks for the 
>> snippet. I’ll update KIP again.
>> 
>> Best,
>> Daniyar Yeralin
>> 
>>> On May 8, 2019, at 1:39 PM, Chris Egerton  wrote:
>>> 
>>> Hi Daniyar,
>>> 
>>> I think you may want to tweak your syntax a little:
>>> 
>>> public static  Serde> List(Serde innerSerde) {
>>>  return new ListSerde(innerSerde);
>>> }
>>> 
>>> Does that work?
>>> 
>>> Cheers,
>>> 
>>> Chris
>>> 
>>> On Wed, May 8, 2019 at 10:29 AM Development >> <mailto:d...@yeralin.net>> wrote:
>>> Hi John,
>>> 
>>> I updated JIRA and KIP.
>>> 
>>> I didn’t know about the process, and created PR before I knew about KIPs :)
>>> 
>>> As per static declaration, I don’t think Java allows that:
>>> 
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>>> On May 7, 2019, at 2:22 PM, John Roesler >>> <mailto:j...@confluent.io>> wrote:
>>>> 
>>>> Thanks for that update. Do you mind making changes primarily on the
>>>> KIP document ? 
>>>> (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>)
>>>> 
>>>> This is the design document that we have to agree on and vote for, the
>>>> PR comes later. It can be nice to have an implementation to look at,
>>>> but the KIP is the main artifact for this discussion.
>>>> 
>>>> With this in mind, it will help get more reviewers to look at it if
>>>> you can tidy up the KIP document so that it stands on its own. People
>>>> shouldn't have to look at any other document to understand the
>>>> motivation of the proposal, and they shouldn't have to look at a PR to
>>>> see what the public API will look like. If it helps, you can take a
>>>> look at some other recent KIPs.
>>>> 
>>>> Given that the list serde needs an inner serde, I agree you can't have
>>>> a zero-argument static factory method for it, but it seems you could
>>>> still have a static method:
>>>> `public static Serde> List(Serde innerSerde)`.
>>>> 
>>>> Thoughts?
>>>> 
>>>> On Tue, May 7, 2019 at 12:18 PM Development >>> <mailto:d...@yeralin.net>> wrote:
>>>>> 
>>>>> Absolutely agree. Already pushed another commit to remove comparator 
>>>>> argument: https://github.com/apache/kafka/pull/6592 
>>>>> <https://github.com/apache/kafka/pull/6592> 
>>>>> <https://github.com/apache/kafka/pull/6592 
>>>>> <https://github.com/apache/kafka/pull/6592>>
>>>>> 
>>>>> Thank you for your input John! I really appreciate it.
>>>>> 
>>>>> What about this point I made:
>>>>> 
>>>>> 1. Since type for List serde needs to be declared before hand, I could 
>>>>> not create a static method for List Serde under 
>>>>> org.apache.kafka.common.serialization.Serdes. I addressed it in the KIP:
>>>>> P.S. Static method corresponding to ListSerde under 
>>>>> org.apache.kafka.common.serialization.Serdes (something like static 
>>>>> public Serde> List() {...} 
>>>>> inorg.apache.kafka.common.serialization.Serdes) class cannot be added 
>>>>> because type needs to be defined 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey Sophie,

Thank you for your input. I think I’d rather finish this KIP as is, and then 
open a new one for the Collections (if everyone agrees). I don’t want to extend 
the current KIP-466, since most of the work is already done for it.

Meanwhile, I’ll start adding some test cases for this new list serde since this 
discussion seems to be approaching its logical end.

Best,
Daniyar Yeralin

> On May 9, 2019, at 1:35 PM, Sophie Blee-Goldman  wrote:
> 
> Good point about serdes for other Collections. On the one hand I'd guess
> that non-List Collections are probably relatively rare in practice (if
> anyone disagrees please correct me!) but on the other hand, a) even if just
> a small number of people benefit I think it's worth the extra effort and b)
> if we do end up needing/wanting them in the future it would save us a KIP
> to just add them now. Personally I feel it would make sense to expand the
> scope of this KIP a bit to include all Collections as a logical unit, but
> the ROI could be low..
> 
> (I know of at least one instance in the unit tests where a Set serde could
> be useful, and there may be more)
> 
> On Thu, May 9, 2019 at 7:27 AM Development  wrote:
> 
>> Hey,
>> 
>> I don’t see any replies. Seems like this proposal can be finalized and
>> called for a vote?
>> 
>> Also I’ve been thinking. Do we need more serdes for other Collections?
>> Like queue or set for example
>> 
>> Best,
>> Daniyar Yeralin
>> 
>>> On May 8, 2019, at 2:28 PM, John Roesler  wrote:
>>> 
>>> Hi Daniyar,
>>> 
>>> No worries about the procedural stuff. Prior experience with KIPs is
>>> not required :)
>>> 
>>> I was just trying to help you propose this stuff in a way that the
>>> others will find easy to review.
>>> 
>>> Thanks for updating the KIP. Thanks to the others for helping out with
>>> the syntax.
>>> 
>>> Given these updates, I'm curious if anyone else has feedback about
>>> this proposal. Personally, I think it sounds fine!
>>> 
>>> -John
>>> 
>>> On Wed, May 8, 2019 at 1:01 PM Development  wrote:
>>>> 
>>>> Hey,
>>>> 
>>>> That worked! I certainly lack Java generics knowledge. Thanks for the
>> snippet. I’ll update KIP again.
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>>> 
>>>>> On May 8, 2019, at 1:39 PM, Chris Egerton  wrote:
>>>>> 
>>>>> Hi Daniyar,
>>>>> 
>>>>> I think you may want to tweak your syntax a little:
>>>>> 
>>>>> public static  Serde> List(Serde innerSerde) {
>>>>> return new ListSerde(innerSerde);
>>>>> }
>>>>> 
>>>>> Does that work?
>>>>> 
>>>>> Cheers,
>>>>> 
>>>>> Chris
>>>>> 
>>>>> On Wed, May 8, 2019 at 10:29 AM Development > d...@yeralin.net>> wrote:
>>>>> Hi John,
>>>>> 
>>>>> I updated JIRA and KIP.
>>>>> 
>>>>> I didn’t know about the process, and created PR before I knew about
>> KIPs :)
>>>>> 
>>>>> As per static declaration, I don’t think Java allows that:
>>>>> 
>>>>> 
>>>>> Best,
>>>>> Daniyar Yeralin
>>>>> 
>>>>>> On May 7, 2019, at 2:22 PM, John Roesler > j...@confluent.io>> wrote:
>>>>>> 
>>>>>> Thanks for that update. Do you mind making changes primarily on the
>>>>>> KIP document ? (
>> 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
>>> )
>>>>>> 
>>>>>> This is the design document that we have to agree on and vote for, the
>>>>>> PR comes later. It can be nice to have an implementation to look at,
>>>>>> but the KIP is the main artifact for this discussion.
>>>>>> 
>>>>>> With this in mind, it will help get more reviewers to look at it if
>>>>>> you can tidy up the KIP document so that it stands on its own. People
>>>>>> shouldn't have to look at any other document to understand the
>>>>>> motivation of the proposal, and they shouldn't have to 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi,

I was trying to add some test cases for the list serde, and it led me to this 
class `org.apache.kafka.common.serialization.SerializationTest`. I saw that it 
relies on method `org.apache.kafka.common.serialization.serdeFrom(Class 
type)`

Now, I’m not sure how to adapt List serde for this method, since it will be 
a “nested class”. What is the best approach in this case? 

I remember that in Jackson for example, one uses a TypeFactory, and constructs 
“collectionType” of two classes. For example, 
`constructCollectionType(List.class, String.class).getClass()`. I don’t think 
it applies here.

Any ideas?

Best,
Daniyar Yeralin

> On May 9, 2019, at 2:10 PM, Development  wrote:
> 
> Hey Sophie,
> 
> Thank you for your input. I think I’d rather finish this KIP as is, and then 
> open a new one for the Collections (if everyone agrees). I don’t want to 
> extend the current KIP-466, since most of the work is already done for it.
> 
> Meanwhile, I’ll start adding some test cases for this new list serde since 
> this discussion seems to be approaching its logical end.
> 
> Best,
> Daniyar Yeralin
> 
>> On May 9, 2019, at 1:35 PM, Sophie Blee-Goldman  wrote:
>> 
>> Good point about serdes for other Collections. On the one hand I'd guess
>> that non-List Collections are probably relatively rare in practice (if
>> anyone disagrees please correct me!) but on the other hand, a) even if just
>> a small number of people benefit I think it's worth the extra effort and b)
>> if we do end up needing/wanting them in the future it would save us a KIP
>> to just add them now. Personally I feel it would make sense to expand the
>> scope of this KIP a bit to include all Collections as a logical unit, but
>> the ROI could be low..
>> 
>> (I know of at least one instance in the unit tests where a Set serde could
>> be useful, and there may be more)
>> 
>> On Thu, May 9, 2019 at 7:27 AM Development  wrote:
>> 
>>> Hey,
>>> 
>>> I don’t see any replies. Seems like this proposal can be finalized and
>>> called for a vote?
>>> 
>>> Also I’ve been thinking. Do we need more serdes for other Collections?
>>> Like queue or set for example
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>>> On May 8, 2019, at 2:28 PM, John Roesler  wrote:
>>>> 
>>>> Hi Daniyar,
>>>> 
>>>> No worries about the procedural stuff. Prior experience with KIPs is
>>>> not required :)
>>>> 
>>>> I was just trying to help you propose this stuff in a way that the
>>>> others will find easy to review.
>>>> 
>>>> Thanks for updating the KIP. Thanks to the others for helping out with
>>>> the syntax.
>>>> 
>>>> Given these updates, I'm curious if anyone else has feedback about
>>>> this proposal. Personally, I think it sounds fine!
>>>> 
>>>> -John
>>>> 
>>>> On Wed, May 8, 2019 at 1:01 PM Development  wrote:
>>>>> 
>>>>> Hey,
>>>>> 
>>>>> That worked! I certainly lack Java generics knowledge. Thanks for the
>>> snippet. I’ll update KIP again.
>>>>> 
>>>>> Best,
>>>>> Daniyar Yeralin
>>>>> 
>>>>>> On May 8, 2019, at 1:39 PM, Chris Egerton  wrote:
>>>>>> 
>>>>>> Hi Daniyar,
>>>>>> 
>>>>>> I think you may want to tweak your syntax a little:
>>>>>> 
>>>>>> public static  Serde> List(Serde innerSerde) {
>>>>>> return new ListSerde(innerSerde);
>>>>>> }
>>>>>> 
>>>>>> Does that work?
>>>>>> 
>>>>>> Cheers,
>>>>>> 
>>>>>> Chris
>>>>>> 
>>>>>> On Wed, May 8, 2019 at 10:29 AM Development >> d...@yeralin.net>> wrote:
>>>>>> Hi John,
>>>>>> 
>>>>>> I updated JIRA and KIP.
>>>>>> 
>>>>>> I didn’t know about the process, and created PR before I knew about
>>> KIPs :)
>>>>>> 
>>>>>> As per static declaration, I don’t think Java allows that:
>>>>>> 
>>>>>> 
>>>>>> Best,
>>>>>> Daniyar Yeralin
>>>>>> 
>>>>>>> On May 7, 2019, at 2:22 PM, John Roesler >> j...@confluent.io>> wrote:
>>>>>>> 
>>

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey,

I think it the proposal is finalized, no one raised any concerns. Shall we call 
it for a [VOTE]?

Best,
Daniyar Yeralin

> On May 10, 2019, at 10:17 AM, John Roesler  wrote:
> 
> Good observation, Daniyar.
> 
> Maybe we should just not implement support for serdeFrom.
> 
> We can always add it later, but I think you're right, we need some
> kind of more sophisticated support, or at least a second argument for
> the inner class.
> 
> For now, it seems like most use cases would be satisfied without
> serdeFrom(...List...)
> 
> -John
> 
> On Fri, May 10, 2019 at 8:57 AM Development  wrote:
>> 
>> Hi,
>> 
>> I was trying to add some test cases for the list serde, and it led me to 
>> this class `org.apache.kafka.common.serialization.SerializationTest`. I saw 
>> that it relies on method 
>> `org.apache.kafka.common.serialization.serdeFrom(Class type)`
>> 
>> Now, I’m not sure how to adapt List serde for this method, since it will 
>> be a “nested class”. What is the best approach in this case?
>> 
>> I remember that in Jackson for example, one uses a TypeFactory, and 
>> constructs “collectionType” of two classes. For example, 
>> `constructCollectionType(List.class, String.class).getClass()`. I don’t 
>> think it applies here.
>> 
>> Any ideas?
>> 
>> Best,
>> Daniyar Yeralin
>> 
>>> On May 9, 2019, at 2:10 PM, Development  wrote:
>>> 
>>> Hey Sophie,
>>> 
>>> Thank you for your input. I think I’d rather finish this KIP as is, and 
>>> then open a new one for the Collections (if everyone agrees). I don’t want 
>>> to extend the current KIP-466, since most of the work is already done for 
>>> it.
>>> 
>>> Meanwhile, I’ll start adding some test cases for this new list serde since 
>>> this discussion seems to be approaching its logical end.
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>>> On May 9, 2019, at 1:35 PM, Sophie Blee-Goldman  
>>>> wrote:
>>>> 
>>>> Good point about serdes for other Collections. On the one hand I'd guess
>>>> that non-List Collections are probably relatively rare in practice (if
>>>> anyone disagrees please correct me!) but on the other hand, a) even if just
>>>> a small number of people benefit I think it's worth the extra effort and b)
>>>> if we do end up needing/wanting them in the future it would save us a KIP
>>>> to just add them now. Personally I feel it would make sense to expand the
>>>> scope of this KIP a bit to include all Collections as a logical unit, but
>>>> the ROI could be low..
>>>> 
>>>> (I know of at least one instance in the unit tests where a Set serde could
>>>> be useful, and there may be more)
>>>> 
>>>> On Thu, May 9, 2019 at 7:27 AM Development  wrote:
>>>> 
>>>>> Hey,
>>>>> 
>>>>> I don’t see any replies. Seems like this proposal can be finalized and
>>>>> called for a vote?
>>>>> 
>>>>> Also I’ve been thinking. Do we need more serdes for other Collections?
>>>>> Like queue or set for example
>>>>> 
>>>>> Best,
>>>>> Daniyar Yeralin
>>>>> 
>>>>>> On May 8, 2019, at 2:28 PM, John Roesler  wrote:
>>>>>> 
>>>>>> Hi Daniyar,
>>>>>> 
>>>>>> No worries about the procedural stuff. Prior experience with KIPs is
>>>>>> not required :)
>>>>>> 
>>>>>> I was just trying to help you propose this stuff in a way that the
>>>>>> others will find easy to review.
>>>>>> 
>>>>>> Thanks for updating the KIP. Thanks to the others for helping out with
>>>>>> the syntax.
>>>>>> 
>>>>>> Given these updates, I'm curious if anyone else has feedback about
>>>>>> this proposal. Personally, I think it sounds fine!
>>>>>> 
>>>>>> -John
>>>>>> 
>>>>>> On Wed, May 8, 2019 at 1:01 PM Development  wrote:
>>>>>>> 
>>>>>>> Hey,
>>>>>>> 
>>>>>>> That worked! I certainly lack Java generics knowledge. Thanks for the
>>>>> snippet. I’ll update KIP again.
>>>>>>> 
>>>>>>> Best,
>>>>>>> Daniyar Yeralin
>>&

[VOTE] KIP-466: Add support for List serialization and deserialization

[Development]

Hello,

I want to start a vote for KIP-466 

 "Add support for List serialization and deserialization”.
The implementation can be found as a PR 
. 
In order to utilize list serde, a user needs to create it in the following 
nested fashion: Serdes.ListSerde(Serdes.someSerde());
Because of this difference, it also requires separate test cases.

Thank you all for your input and support.

Best,
Daniyar Yeralin

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey,

- did we consider to make the return type (ie, ArrayList, vs
LinkesList) configurable or encode it the serialized bytes?

Not sure about this one. Could you elaborate?

- atm the size of each element is encoded individually; did we consider
an optimization for fixed size elements (like Long) to avoid this overhead?

I cannot think of any clean way to do so. How would you see it?

Btw I resolved all your comments under PR

Best,
Daniyar Yeralin

> On May 24, 2019, at 12:01 AM, Matthias J. Sax  wrote:
> 
> Thanks for the KIP. I also had a look into the PR and have two follow up
> question:
> 
> 
> - did we consider to make the return type (ie, ArrayList, vs
> LinkesList) configurable or encode it the serialized bytes?
> 
> - atm the size of each element is encoded individually; did we consider
> an optimization for fixed size elements (like Long) to avoid this overhead?
> 
> 
> 
> -Matthias
> 
> On 5/15/19 6:05 PM, John Roesler wrote:
>> Sounds good!
>> 
>> On Tue, May 14, 2019 at 9:21 AM Development  wrote:
>>> 
>>> Hey,
>>> 
>>> I think it the proposal is finalized, no one raised any concerns. Shall we 
>>> call it for a [VOTE]?
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>>> On May 10, 2019, at 10:17 AM, John Roesler  wrote:
>>>> 
>>>> Good observation, Daniyar.
>>>> 
>>>> Maybe we should just not implement support for serdeFrom.
>>>> 
>>>> We can always add it later, but I think you're right, we need some
>>>> kind of more sophisticated support, or at least a second argument for
>>>> the inner class.
>>>> 
>>>> For now, it seems like most use cases would be satisfied without
>>>> serdeFrom(...List...)
>>>> 
>>>> -John
>>>> 
>>>> On Fri, May 10, 2019 at 8:57 AM Development  wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> I was trying to add some test cases for the list serde, and it led me to 
>>>>> this class `org.apache.kafka.common.serialization.SerializationTest`. I 
>>>>> saw that it relies on method 
>>>>> `org.apache.kafka.common.serialization.serdeFrom(Class type)`
>>>>> 
>>>>> Now, I’m not sure how to adapt List serde for this method, since it 
>>>>> will be a “nested class”. What is the best approach in this case?
>>>>> 
>>>>> I remember that in Jackson for example, one uses a TypeFactory, and 
>>>>> constructs “collectionType” of two classes. For example, 
>>>>> `constructCollectionType(List.class, String.class).getClass()`. I don’t 
>>>>> think it applies here.
>>>>> 
>>>>> Any ideas?
>>>>> 
>>>>> Best,
>>>>> Daniyar Yeralin
>>>>> 
>>>>>> On May 9, 2019, at 2:10 PM, Development  wrote:
>>>>>> 
>>>>>> Hey Sophie,
>>>>>> 
>>>>>> Thank you for your input. I think I’d rather finish this KIP as is, and 
>>>>>> then open a new one for the Collections (if everyone agrees). I don’t 
>>>>>> want to extend the current KIP-466, since most of the work is already 
>>>>>> done for it.
>>>>>> 
>>>>>> Meanwhile, I’ll start adding some test cases for this new list serde 
>>>>>> since this discussion seems to be approaching its logical end.
>>>>>> 
>>>>>> Best,
>>>>>> Daniyar Yeralin
>>>>>> 
>>>>>>> On May 9, 2019, at 1:35 PM, Sophie Blee-Goldman  
>>>>>>> wrote:
>>>>>>> 
>>>>>>> Good point about serdes for other Collections. On the one hand I'd guess
>>>>>>> that non-List Collections are probably relatively rare in practice (if
>>>>>>> anyone disagrees please correct me!) but on the other hand, a) even if 
>>>>>>> just
>>>>>>> a small number of people benefit I think it's worth the extra effort 
>>>>>>> and b)
>>>>>>> if we do end up needing/wanting them in the future it would save us a 
>>>>>>> KIP
>>>>>>> to just add them now. Personally I feel it would make sense to expand 
>>>>>>> the
>>>>>>> scope of this KIP a bit to include all Collections as a logical unit, 
>>>>>>>

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Bump

> On May 24, 2019, at 2:09 PM, Development  wrote:
> 
> Hey,
> 
> - did we consider to make the return type (ie, ArrayList, vs
> LinkesList) configurable or encode it the serialized bytes?
> 
> Not sure about this one. Could you elaborate?
> 
> - atm the size of each element is encoded individually; did we consider
> an optimization for fixed size elements (like Long) to avoid this overhead?
> 
> I cannot think of any clean way to do so. How would you see it?
> 
> Btw I resolved all your comments under PR
> 
> Best,
> Daniyar Yeralin
> 
>> On May 24, 2019, at 12:01 AM, Matthias J. Sax  wrote:
>> 
>> Thanks for the KIP. I also had a look into the PR and have two follow up
>> question:
>> 
>> 
>> - did we consider to make the return type (ie, ArrayList, vs
>> LinkesList) configurable or encode it the serialized bytes?
>> 
>> - atm the size of each element is encoded individually; did we consider
>> an optimization for fixed size elements (like Long) to avoid this overhead?
>> 
>> 
>> 
>> -Matthias
>> 
>> On 5/15/19 6:05 PM, John Roesler wrote:
>>> Sounds good!
>>> 
>>> On Tue, May 14, 2019 at 9:21 AM Development  wrote:
>>>> 
>>>> Hey,
>>>> 
>>>> I think it the proposal is finalized, no one raised any concerns. Shall we 
>>>> call it for a [VOTE]?
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>>> 
>>>>> On May 10, 2019, at 10:17 AM, John Roesler  wrote:
>>>>> 
>>>>> Good observation, Daniyar.
>>>>> 
>>>>> Maybe we should just not implement support for serdeFrom.
>>>>> 
>>>>> We can always add it later, but I think you're right, we need some
>>>>> kind of more sophisticated support, or at least a second argument for
>>>>> the inner class.
>>>>> 
>>>>> For now, it seems like most use cases would be satisfied without
>>>>> serdeFrom(...List...)
>>>>> 
>>>>> -John
>>>>> 
>>>>> On Fri, May 10, 2019 at 8:57 AM Development  wrote:
>>>>>> 
>>>>>> Hi,
>>>>>> 
>>>>>> I was trying to add some test cases for the list serde, and it led me to 
>>>>>> this class `org.apache.kafka.common.serialization.SerializationTest`. I 
>>>>>> saw that it relies on method 
>>>>>> `org.apache.kafka.common.serialization.serdeFrom(Class type)`
>>>>>> 
>>>>>> Now, I’m not sure how to adapt List serde for this method, since it 
>>>>>> will be a “nested class”. What is the best approach in this case?
>>>>>> 
>>>>>> I remember that in Jackson for example, one uses a TypeFactory, and 
>>>>>> constructs “collectionType” of two classes. For example, 
>>>>>> `constructCollectionType(List.class, String.class).getClass()`. I don’t 
>>>>>> think it applies here.
>>>>>> 
>>>>>> Any ideas?
>>>>>> 
>>>>>> Best,
>>>>>> Daniyar Yeralin
>>>>>> 
>>>>>>> On May 9, 2019, at 2:10 PM, Development  wrote:
>>>>>>> 
>>>>>>> Hey Sophie,
>>>>>>> 
>>>>>>> Thank you for your input. I think I’d rather finish this KIP as is, and 
>>>>>>> then open a new one for the Collections (if everyone agrees). I don’t 
>>>>>>> want to extend the current KIP-466, since most of the work is already 
>>>>>>> done for it.
>>>>>>> 
>>>>>>> Meanwhile, I’ll start adding some test cases for this new list serde 
>>>>>>> since this discussion seems to be approaching its logical end.
>>>>>>> 
>>>>>>> Best,
>>>>>>> Daniyar Yeralin
>>>>>>> 
>>>>>>>> On May 9, 2019, at 1:35 PM, Sophie Blee-Goldman  
>>>>>>>> wrote:
>>>>>>>> 
>>>>>>>> Good point about serdes for other Collections. On the one hand I'd 
>>>>>>>> guess
>>>>>>>> that non-List Collections are probably relatively rare in practice (if
>>>>>>>> anyone disagrees please correct me!) but on the other hand, a) even if 
>>>>>>>> just
>

[VOTE] KIP-466: Add support for List serialization and deserialization

[Development]

Hello,

I want to start a vote for KIP-466 
>
 "Add support for List serialization and deserialization”.
The implementation can be found as a PR 
>. 

Thank you all for your input and support.

Best,
Daniyar Yeralin

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi Matthias,

Indeed, you are right. I missed your email, I had a problem with my mail 
server, so I guess I didn’t receive it.

1) Here is what I came up with
In my ListSerializer.java I have the following:
try (final DataOutputStream out = new DataOutputStream(baos)) {
// I’m encoding the class name at the top of the byte array
out.writeUTF(data.getClass().getCanonicalName());
out.writeInt(size);
for (T entry : data) {
final byte[] bytes = serializer.serialize(topic, entry);
out.writeInt(bytes.length);
out.write(bytes);
}
return baos.toByteArray();
}
Then in ListDeserializer.java:
try (final DataInputStream dis = new DataInputStream(new 
ByteArrayInputStream(data))) {
final String listClassName = dis.readUTF();
final int size = dis.readInt();
List deserializedList = getListInstance(listClassName, size);
for (int i = 0; i < size; i++) {
byte[] payload = new byte[dis.readInt()];
dis.read(payload);
deserializedList.add(deserializer.deserialize(topic, payload));
}
return deserializedList;
}
private List getListInstance(String listClassName, int listSize) {
try {
Class listClass = Class.forName(listClassName);
Constructor listConstructor = listClass.getConstructor(Integer.TYPE);
return (List) listConstructor.newInstance(listSize);
} catch (Exception e) {
throw new RuntimeException("Could not construct a list instance of \"" 
+ listClassName + "\"", e);
}
}
It works just fine, except for one edge case. If you try to pass 
Arrays.asList(...) to the (de)serializer which is ArrayList instance, it will 
throw: java.lang.ClassNotFoundException: java.util.Arrays.ArrayList
Because it is expecting java.util.ArrayList.
The problem is described here: 
https://stackoverflow.com/questions/28851652/java-lang-classcastexception-java-util-arraysarraylist-cannot-be-cast-to-java
Arrays.asList() produces an instance of a List implementation 
(java.util.Arrays$ArrayList) that is not java.util.ArrayList

What do you think of this? Based on your experience, what is the best approach 
in this case? Maybe we modify a String? Is there any other cases where similar 
problem happens?

Still working on (2)

Thank you Matthias!

Best,
Daniyar Yeralin

> On Jun 11, 2019, at 6:05 PM, Matthias J. Sax  wrote:
> 
> Seems you missed my reply from 31/6. C&P below:
> 
>> (1) The current PR suggests to always instantiate an `ArrayList` --
>> however, if a user wants to use any other list implementation, they have
>> no way to specify this. It might be good to either allow users to
>> specify the list-type on the deserializer, or encode the list type
>> directly in the bytes, and hence, whatever type the serialized list was,
>> the same type will be used on deserialization (might only work for Java
>> build-it list types).
>> 
>> Personally, I thinks its better/more flexible to specify the list-type
>> on the deserializer, as it also allows to plug-in any custom list types.
>> 
>> This could of course be opt-in and for the case users don't care, we
>> just default to `ArrayList`.
>> 
>> 
>> (2) For Java built-in types, we could check the type via `instanceof` --
>> if the type is unknown, we fall back to per-element length encoding. As
>> an alternative, we could also add a constructor taking an `enum` with
>> two values `fixed-size` and `variable-size`, or a config instead of a
>> constructor element.
>> 
>> 
>> Just bounding off ideas -- maybe there are good reasons (too
>> complicated?) to not support either of them.
>> 
> 
> 
> -Matthias
> 
> On 6/10/19 8:44 AM, Development wrote:
>> Bump
>> 
>>> On May 24, 2019, at 2:09 PM, Development  wrote:
>>> 
>>> Hey,
>>> 
>>> - did we consider to make the return type (ie, ArrayList, vs
>>> LinkesList) configurable or encode it the serialized bytes?
>>> 
>>> Not sure about this one. Could you elaborate?
>>> 
>>> - atm the size of each element is encoded individually; did we consider
>>> an optimization for fixed size elements (like Long) to avoid this overhead?
>>> 
>>> I cannot think of any clean way to do so. How would you see it?
>>> 
>>> Btw I resolved all your comments under PR
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>>> On May 24, 2019, at 12:01 AM, Matthias J. Sax  
>>>> wrote:
>>>> 
>>>> Thanks for the KIP. I also had a look into the PR and have two follow up
>>>> question:
>>>> 
>>>> 
>>>> - did we consider to make the return type (ie, ArrayList, vs
>>>>

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hmm the formatting got removed unfortunately. I’m sorry, it got harder to read 
my email.

> On Jun 12, 2019, at 10:27 AM, Development  wrote:
> 
> Hi Matthias,
> 
> Indeed, you are right. I missed your email, I had a problem with my mail 
> server, so I guess I didn’t receive it.
> 
> 1) Here is what I came up with
> In my ListSerializer.java I have the following:
> try (final DataOutputStream out = new DataOutputStream(baos)) {
>// I’m encoding the class name at the top of the byte array
>out.writeUTF(data.getClass().getCanonicalName());
>out.writeInt(size);
>for (T entry : data) {
>final byte[] bytes = serializer.serialize(topic, entry);
>out.writeInt(bytes.length);
>out.write(bytes);
>}
>return baos.toByteArray();
> }
> Then in ListDeserializer.java:
> try (final DataInputStream dis = new DataInputStream(new 
> ByteArrayInputStream(data))) {
>final String listClassName = dis.readUTF();
>final int size = dis.readInt();
>List deserializedList = getListInstance(listClassName, size);
>for (int i = 0; i < size; i++) {
>byte[] payload = new byte[dis.readInt()];
>dis.read(payload);
>deserializedList.add(deserializer.deserialize(topic, payload));
>}
>return deserializedList;
> }
> private List getListInstance(String listClassName, int listSize) {
>try {
>Class listClass = Class.forName(listClassName);
>Constructor listConstructor = 
> listClass.getConstructor(Integer.TYPE);
>return (List) listConstructor.newInstance(listSize);
>} catch (Exception e) {
>throw new RuntimeException("Could not construct a list instance of \"" 
> + listClassName + "\"", e);
>}
> }
> It works just fine, except for one edge case. If you try to pass 
> Arrays.asList(...) to the (de)serializer which is ArrayList instance, it will 
> throw: java.lang.ClassNotFoundException: java.util.Arrays.ArrayList
> Because it is expecting java.util.ArrayList.
> The problem is described here: 
> https://stackoverflow.com/questions/28851652/java-lang-classcastexception-java-util-arraysarraylist-cannot-be-cast-to-java
> Arrays.asList() produces an instance of a List implementation 
> (java.util.Arrays$ArrayList) that is not java.util.ArrayList
> 
> What do you think of this? Based on your experience, what is the best 
> approach in this case? Maybe we modify a String? Is there any other cases 
> where similar problem happens?
> 
> Still working on (2)
> 
> Thank you Matthias!
> 
> Best,
> Daniyar Yeralin
> 
>> On Jun 11, 2019, at 6:05 PM, Matthias J. Sax  wrote:
>> 
>> Seems you missed my reply from 31/6. C&P below:
>> 
>>> (1) The current PR suggests to always instantiate an `ArrayList` --
>>> however, if a user wants to use any other list implementation, they have
>>> no way to specify this. It might be good to either allow users to
>>> specify the list-type on the deserializer, or encode the list type
>>> directly in the bytes, and hence, whatever type the serialized list was,
>>> the same type will be used on deserialization (might only work for Java
>>> build-it list types).
>>> 
>>> Personally, I thinks its better/more flexible to specify the list-type
>>> on the deserializer, as it also allows to plug-in any custom list types.
>>> 
>>> This could of course be opt-in and for the case users don't care, we
>>> just default to `ArrayList`.
>>> 
>>> 
>>> (2) For Java built-in types, we could check the type via `instanceof` --
>>> if the type is unknown, we fall back to per-element length encoding. As
>>> an alternative, we could also add a constructor taking an `enum` with
>>> two values `fixed-size` and `variable-size`, or a config instead of a
>>> constructor element.
>>> 
>>> 
>>> Just bounding off ideas -- maybe there are good reasons (too
>>> complicated?) to not support either of them.
>>> 
>> 
>> 
>> -Matthias
>> 
>> On 6/10/19 8:44 AM, Development wrote:
>>> Bump
>>> 
>>>> On May 24, 2019, at 2:09 PM, Development  wrote:
>>>> 
>>>> Hey,
>>>> 
>>>> - did we consider to make the return type (ie, ArrayList, vs
>>>> LinkesList) configurable or encode it the serialized bytes?
>>>> 
>>>> Not sure about this one. Could you elaborate?
>>>> 
>>>> - atm the size of each element is encoded individually; did we consider
>>>> an optimization for fixed size elemen

Posted a new article about Kafka Streams

[Development]

Hello Kafka Dev community,

I wrote an article on implementing a custom transformer using Processor API for 
Kafka Streams!
https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregation-f6a4a6c376be
 

Feel free to leave a feedback and/or corrections if I wrote something silly :)

Thank you!

Best,
Daniyar Yeralin

Re: Posted a new article about Kafka Streams

[Development]

Bad link:
https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregator-6cb23d00eaa7

> On Jun 14, 2019, at 11:07 AM, Development  wrote:
> 
> Hello Kafka Dev community,
> 
> I wrote an article on implementing a custom transformer using Processor API 
> for Kafka Streams!
> https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregation-f6a4a6c376be
>  
> <https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregation-f6a4a6c376be>
> Feel free to leave a feedback and/or corrections if I wrote something silly :)
> 
> Thank you!
> 
> Best,
> Daniyar Yeralin

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

bump

Re: Posted a new article about Kafka Streams

[Development]

Hey Paul,

Thank you so much for your input! :)
Just updated my article about the iterator closing.

Thank you!

Best,
Daniyar Yeralin

> On Jun 16, 2019, at 4:11 PM, Paul Whalen  wrote:
> 
> I've only skimmed it so far, but great job!  The community is in serious
> need of more examples of the Processor API, there really isn't that much
> out there.
> 
> One thing I did notice: the iterator you get from kvStore.all() ought to be
> closed to release resources when you're done with it.  This matters when
> the underlying store is RocksDB, which as I understand it, allocates
> additional memory off heap to iterate.  I see this bug everywhere, after
> writing it many times myself over the course of many months :). it's too
> bad the API can't be more clear, but I guess there's not a ton you can do
> in Java.  People think about this kind of thing for DB calls, but when
> you're using something that's basically a HashMap you really don't think of
> it at all.
> 
> Side plug for KIP-401 since you're using the Processor API, it would be
> interesting to hear on that discussion thread if you find it useful (
> https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=97553756).
> It seems like there's soft interest, but maybe not yet enough to push it
> over the finish line.
> 
> Again, great job!
> 
> Paul
> 
> On Fri, Jun 14, 2019 at 10:33 AM Development  wrote:
> 
>> Bad link:
>> 
>> https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregator-6cb23d00eaa7
>> 
>>> On Jun 14, 2019, at 11:07 AM, Development  wrote:
>>> 
>>> Hello Kafka Dev community,
>>> 
>>> I wrote an article on implementing a custom transformer using Processor
>> API for Kafka Streams!
>>> 
>> https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregation-f6a4a6c376be
>> <
>> https://medium.com/@daniyaryeralin/utilizing-kafka-streams-processor-api-and-implementing-custom-aggregation-f6a4a6c376be
>>> 
>>> Feel free to leave a feedback and/or corrections if I wrote something
>> silly :)
>>> 
>>> Thank you!
>>> 
>>> Best,
>>> Daniyar Yeralin
>> 
>> 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

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  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
> interesting.
> 
> Thanks,
> -John
> 
> On Mon, Jun 17, 2019 at 12:38 PM Development  wrote:
>> 
>> bump

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

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>
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  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  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
>> interesting.
>> 
>> Thanks,
>> -John
>> 
>> On Mon, Jun 17, 2019 at 12:38 PM Development  wrote:
>>> 
>>> bump
> 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

I made and pushed necessary commits, so we could review the final version under 
PR 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  wrote:
> 
> Hey Daniyar,
> 
> Looks good to me! Thanks for considering it.
> 
> Thanks,
> -John
> 
> On Fri, Jun 21, 2019 at 9:04 AM Development  <mailto: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 > <mailto: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? The serde could
>>> only be used to produce a LinkedList, thus, we'd still need an
>>> inner serde, like you have in the KIP (Serde innerSerde).
>>> 
>>> Something more like Serde> = 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 >> <mailto:d...@yeralin.net>
>>> <mailto:d...@yeralin.net <mailto: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>
>>>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 >>> <mailto:d...@yeralin.net>
>>>><mailto:d...@yeralin.net <mailto:d...@yeralin.net>>> wrote:
>>>> 
>>>>Hi John,
>>>> 
>>>>Thank you for your input! Yes, my idea looks a little bit over
>>&g

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

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:+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  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 >> <mailto: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
>>>> 
>>>> 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 >>>> <mailto: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 >>>> <mailto:d...@yeralin.net> <mailto: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 >>>>> <mailto:matth...@confluent.io> <mailto:matth...@confluent.io>> wrote:
>>>>>> 
>>>>>

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

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  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  Serde> 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  <mailto: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  > <mailto: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  > <mailto: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  > <mailto: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 primiti

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

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  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  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  Serde> 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 >> <mailto: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 
>

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

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  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  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  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  Serde> 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 s

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi John,

I knew I was missing something. Yes, that makes sense now, I removed all 
`listSerde()` methods, and left empty constructors instead.

As per `CommonClientConfigs` I looked at the class, it doesn’t have any 
properties related to serdes, and that bothers me a little.

All properties like `default.key.serde` `default.windowed.key.serde.*` are 
located in StreamsConfig. I don’t want to create a confusion.
What also doesn’t make sense to me is that `WindowedSerdes` and its 
(de)serializers are not located in org.apache.kafka.common.serialization. I 
guess it kind of makes sense since windowed serdes are only available for kafka 
streams, not vice versa. 

If everyone is okay to put list properties in `CommonClientConfigs` class, I’ll 
go ahead and do that then.

Thank you for your input!

Best,
Daniyar Yeralin

> On Jul 15, 2019, at 11:45 AM, John Roesler  wrote:
> 
> 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  Serde> 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  <mailto: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 > <mailto: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 >> <mailto: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 
>>> <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 `

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi,

Pushed new changes under my PR: https://github.com/apache/kafka/pull/6592 
<https://github.com/apache/kafka/pull/6592>

Feel free to put any comments in there.

Best,
Daniyar Yeralin

> On Jul 15, 2019, at 1:06 PM, Development  wrote:
> 
> Hi John,
> 
> I knew I was missing something. Yes, that makes sense now, I removed all 
> `listSerde()` methods, and left empty constructors instead.
> 
> As per `CommonClientConfigs` I looked at the class, it doesn’t have any 
> properties related to serdes, and that bothers me a little.
> 
> All properties like `default.key.serde` `default.windowed.key.serde.*` are 
> located in StreamsConfig. I don’t want to create a confusion.
> What also doesn’t make sense to me is that `WindowedSerdes` and its 
> (de)serializers are not located in org.apache.kafka.common.serialization. I 
> guess it kind of makes sense since windowed serdes are only available for 
> kafka streams, not vice versa. 
> 
> If everyone is okay to put list properties in `CommonClientConfigs` class, 
> I’ll go ahead and do that then.
> 
> Thank you for your input!
> 
> Best,
> Daniyar Yeralin
> 
>> On Jul 15, 2019, at 11:45 AM, John Roesler  wrote:
>> 
>> 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  Serde> 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 > <mailto: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 >> <mailto: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 >>> <mailto: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 
>>>> <https://github.com/apache/kafka/pull/7067>)
>>>> 
>>>> Note, that if a user would insta

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi,

Yes, totally forgot about the statement. KIP-466 is updated.

Thank you so much John Roesler, Matthias J. Sax, Sophie Blee-Goldman for your 
valuable input!

I hope I did not cause too much trouble :)

I’ll start the vote now.

Best,
Daniyar Yeralin

> On Jul 16, 2019, at 3:17 PM, John Roesler  wrote:
> 
> Hi Daniyar,
> 
> Thanks for that update. I took a look, and I think this is in good shape.
> 
> One note, the statement "New method public static  Serde>
> ListSerde() in org.apache.kafka.common.serialization.Serdes class
> (infers list implementation and inner serde from config file)" is
> still present in the KIP, although I do it is was removed from the PR.
> 
> Once you remove that statement from the KIP, then I think this KIP is
> ready to go up for a vote! Then, we can really review the PR in
> earnest and get this thing merged.
> 
> Thanks,
> -john
> 
> On Tue, Jul 16, 2019 at 2:05 PM Development  wrote:
>> 
>> Hi,
>> 
>> Pushed new changes under my PR: https://github.com/apache/kafka/pull/6592 
>> <https://github.com/apache/kafka/pull/6592>
>> 
>> Feel free to put any comments in there.
>> 
>> Best,
>> Daniyar Yeralin
>> 
>>> On Jul 15, 2019, at 1:06 PM, Development  wrote:
>>> 
>>> Hi John,
>>> 
>>> I knew I was missing something. Yes, that makes sense now, I removed all 
>>> `listSerde()` methods, and left empty constructors instead.
>>> 
>>> As per `CommonClientConfigs` I looked at the class, it doesn’t have any 
>>> properties related to serdes, and that bothers me a little.
>>> 
>>> All properties like `default.key.serde` `default.windowed.key.serde.*` are 
>>> located in StreamsConfig. I don’t want to create a confusion.
>>> What also doesn’t make sense to me is that `WindowedSerdes` and its 
>>> (de)serializers are not located in org.apache.kafka.common.serialization. I 
>>> guess it kind of makes sense since windowed serdes are only available for 
>>> kafka streams, not vice versa.
>>> 
>>> If everyone is okay to put list properties in `CommonClientConfigs` class, 
>>> I’ll go ahead and do that then.
>>> 
>>> Thank you for your input!
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>>> On Jul 15, 2019, at 11:45 AM, John Roesler  wrote:
>>>> 
>>>> 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  Serde> 
>>>> 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 >>> <mailto: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 >>>> <mailto:d...@yeralin.net>> wrote:
>>>>> 
>>>>> Hi Matthias,
>>>>> 
>>>>> Thank y

[VOTE] KIP-466: Add support for List serialization and deserialization

[Development]

Hi,

I’d like to start a vote thread for KIP-466.

This addition will introduce new serde type ListSerde.

More info at: 
https://cwiki.apache.org/confluence/display/KAFKA/KIP-466%3A+Add+support+for+List%3CT%3E+serialization+and+deserialization
 

Best,
Daniyar Yeralin

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hi Matthias,

I agree, ConsumerConfig did not seem like a right place for these 
configurations.
I’ll put them in ProducerConfig, ConsumerConfig, and StreamsConfig.

However, I have a question. What should I do in "configure(Map 
configs, boolean isKey)” methods? Which configurations should I try to locate? 
I was comparing my (de)serializer implementations with 
SessionWindows(De)serializer classes, and they use StreamsConfig class to get  
either StreamsConfig.DEFAULT_WINDOWED_KEY_SERDE_INNER_CLASS : 
StreamsConfig.DEFAULT_WINDOWED_VALUE_SERDE_INNER_CLASS

In my case, as I mentioned earlier, StreamsConfig class is not accessible from 
org.apache.kafka.common.serialization package. So, I can’t utilize it. Any 
suggestions here?

Best,
Daniyar Yeralin


> On Jul 18, 2019, at 8:46 PM, Matthias J. Sax  wrote:
> 
> Thanks!
> 
> One minor question about the configs. The KIP adds three classes, a
> Serializer, a Deserializer, and a Serde.
> 
> Hence, would it make sense to add the corresponding configs to
> `ConsumerConfig`, `ProducerConfig`, and `StreamsConfig` using slightly
> different names each time?
> 
> 
> Somethin like this:
> 
> ProducerConfig:
> 
> list.key/value.serializer.type
> list.key/value.serializer.inner
> 
> ConsumerConfig:
> 
> list.key/value.deserializer.type
> list.key/value.deserializer.inner
> 
> StreamsConfig:
> 
> default.list.key/value.serde.type
> default.list.key/value.serde.inner
> 
> 
> Adding `d.l.k/v.serde.t/i` to `CommonClientConfigs does not sound right
> to me. Also note, that it seems better to avoid the `default.` prefix
> for consumers and producers because there is only one Serializer or
> Deserializer anyway. Only for Streams, there are multiple and
> StreamsConfig specifies the default one of an operator does not
> overwrite it.
> 
> Thoughts?
> 
> 
> Also, the KIP should explicitly mention to what classed certain configs
> are added. Atm, the KIP only list parameter names, but does not state
> where those are added.
> 
> 
> -Matthias
> 
> 
> 
> 
> 
> On 7/16/19 1:11 PM, Development wrote:
>> Hi,
>> 
>> Yes, totally forgot about the statement. KIP-466 is updated.
>> 
>> Thank you so much John Roesler, Matthias J. Sax, Sophie Blee-Goldman for 
>> your valuable input!
>> 
>> I hope I did not cause too much trouble :)
>> 
>> I’ll start the vote now.
>> 
>> Best,
>> Daniyar Yeralin
>> 
>>> On Jul 16, 2019, at 3:17 PM, John Roesler  wrote:
>>> 
>>> Hi Daniyar,
>>> 
>>> Thanks for that update. I took a look, and I think this is in good shape.
>>> 
>>> One note, the statement "New method public static  Serde>
>>> ListSerde() in org.apache.kafka.common.serialization.Serdes class
>>> (infers list implementation and inner serde from config file)" is
>>> still present in the KIP, although I do it is was removed from the PR.
>>> 
>>> Once you remove that statement from the KIP, then I think this KIP is
>>> ready to go up for a vote! Then, we can really review the PR in
>>> earnest and get this thing merged.
>>> 
>>> Thanks,
>>> -john
>>> 
>>> On Tue, Jul 16, 2019 at 2:05 PM Development  wrote:
>>>> 
>>>> Hi,
>>>> 
>>>> Pushed new changes under my PR: https://github.com/apache/kafka/pull/6592 
>>>> <https://github.com/apache/kafka/pull/6592>
>>>> 
>>>> Feel free to put any comments in there.
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>>> 
>>>>> On Jul 15, 2019, at 1:06 PM, Development  wrote:
>>>>> 
>>>>> Hi John,
>>>>> 
>>>>> I knew I was missing something. Yes, that makes sense now, I removed all 
>>>>> `listSerde()` methods, and left empty constructors instead.
>>>>> 
>>>>> As per `CommonClientConfigs` I looked at the class, it doesn’t have any 
>>>>> properties related to serdes, and that bothers me a little.
>>>>> 
>>>>> All properties like `default.key.serde` `default.windowed.key.serde.*` 
>>>>> are located in StreamsConfig. I don’t want to create a confusion.
>>>>> What also doesn’t make sense to me is that `WindowedSerdes` and its 
>>>>> (de)serializers are not located in org.apache.kafka.common.serialization. 
>>>>> I guess it kind of makes sense since windowed serdes are only available 
>>>>> for kafka streams, not vice versa.
>>>>> 
>>>>> If everyone is

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey Matthias,

It looks a little confusing, but I don’t have enough expertise to judge on the 
configuration placement.

If you think, it is fine I’ll go ahead with this approach.

Best,
Daniyar Yeralin

> On Jul 19, 2019, at 5:49 PM, Matthias J. Sax  wrote:
> 
> Good point.
> 
> I guess the simplest solution is, to actually add
> 
>>> default.list.key/value.serde.type
>>> default.list.key/value.serde.inner
> 
> to both `CommonClientConfigs` and `StreamsConfig`.
> 
> It's not super clean, but I think it's the best we can do. Thoughts?
> 
> 
> -Matthias
> 
> On 7/19/19 1:23 PM, Development wrote:
>> Hi Matthias,
>> 
>> I agree, ConsumerConfig did not seem like a right place for these 
>> configurations.
>> I’ll put them in ProducerConfig, ConsumerConfig, and StreamsConfig.
>> 
>> However, I have a question. What should I do in "configure(Map 
>> configs, boolean isKey)” methods? Which configurations should I try to 
>> locate? I was comparing my (de)serializer implementations with 
>> SessionWindows(De)serializer classes, and they use StreamsConfig class to 
>> get  either StreamsConfig.DEFAULT_WINDOWED_KEY_SERDE_INNER_CLASS : 
>> StreamsConfig.DEFAULT_WINDOWED_VALUE_SERDE_INNER_CLASS
>> 
>> In my case, as I mentioned earlier, StreamsConfig class is not accessible 
>> from org.apache.kafka.common.serialization package. So, I can’t utilize it. 
>> Any suggestions here?
>> 
>> Best,
>> Daniyar Yeralin
>> 
>> 
>>> On Jul 18, 2019, at 8:46 PM, Matthias J. Sax  wrote:
>>> 
>>> Thanks!
>>> 
>>> One minor question about the configs. The KIP adds three classes, a
>>> Serializer, a Deserializer, and a Serde.
>>> 
>>> Hence, would it make sense to add the corresponding configs to
>>> `ConsumerConfig`, `ProducerConfig`, and `StreamsConfig` using slightly
>>> different names each time?
>>> 
>>> 
>>> Somethin like this:
>>> 
>>> ProducerConfig:
>>> 
>>> list.key/value.serializer.type
>>> list.key/value.serializer.inner
>>> 
>>> ConsumerConfig:
>>> 
>>> list.key/value.deserializer.type
>>> list.key/value.deserializer.inner
>>> 
>>> StreamsConfig:
>>> 
>>> default.list.key/value.serde.type
>>> default.list.key/value.serde.inner
>>> 
>>> 
>>> Adding `d.l.k/v.serde.t/i` to `CommonClientConfigs does not sound right
>>> to me. Also note, that it seems better to avoid the `default.` prefix
>>> for consumers and producers because there is only one Serializer or
>>> Deserializer anyway. Only for Streams, there are multiple and
>>> StreamsConfig specifies the default one of an operator does not
>>> overwrite it.
>>> 
>>> Thoughts?
>>> 
>>> 
>>> Also, the KIP should explicitly mention to what classed certain configs
>>> are added. Atm, the KIP only list parameter names, but does not state
>>> where those are added.
>>> 
>>> 
>>> -Matthias
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On 7/16/19 1:11 PM, Development wrote:
>>>> Hi,
>>>> 
>>>> Yes, totally forgot about the statement. KIP-466 is updated.
>>>> 
>>>> Thank you so much John Roesler, Matthias J. Sax, Sophie Blee-Goldman for 
>>>> your valuable input!
>>>> 
>>>> I hope I did not cause too much trouble :)
>>>> 
>>>> I’ll start the vote now.
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>>> 
>>>>> On Jul 16, 2019, at 3:17 PM, John Roesler  wrote:
>>>>> 
>>>>> Hi Daniyar,
>>>>> 
>>>>> Thanks for that update. I took a look, and I think this is in good shape.
>>>>> 
>>>>> One note, the statement "New method public static  Serde>
>>>>> ListSerde() in org.apache.kafka.common.serialization.Serdes class
>>>>> (infers list implementation and inner serde from config file)" is
>>>>> still present in the KIP, although I do it is was removed from the PR.
>>>>> 
>>>>> Once you remove that statement from the KIP, then I think this KIP is
>>>>> ready to go up for a vote! Then, we can really review the PR in
>>>>> earnest and get this thing merged.
>>>>> 
>>>>> Thanks,
>>>>> -john
>>>>> 
>>>>> 

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Bump

> On Jul 22, 2019, at 11:26 AM, Development  wrote:
> 
> Hey Matthias,
> 
> It looks a little confusing, but I don’t have enough expertise to judge on 
> the configuration placement.
> 
> If you think, it is fine I’ll go ahead with this approach.
> 
> Best,
> Daniyar Yeralin
> 
>> On Jul 19, 2019, at 5:49 PM, Matthias J. Sax  wrote:
>> 
>> Good point.
>> 
>> I guess the simplest solution is, to actually add
>> 
>>>> default.list.key/value.serde.type
>>>> default.list.key/value.serde.inner
>> 
>> to both `CommonClientConfigs` and `StreamsConfig`.
>> 
>> It's not super clean, but I think it's the best we can do. Thoughts?
>> 
>> 
>> -Matthias
>> 
>> On 7/19/19 1:23 PM, Development wrote:
>>> Hi Matthias,
>>> 
>>> I agree, ConsumerConfig did not seem like a right place for these 
>>> configurations.
>>> I’ll put them in ProducerConfig, ConsumerConfig, and StreamsConfig.
>>> 
>>> However, I have a question. What should I do in "configure(Map 
>>> configs, boolean isKey)” methods? Which configurations should I try to 
>>> locate? I was comparing my (de)serializer implementations with 
>>> SessionWindows(De)serializer classes, and they use StreamsConfig class to 
>>> get  either StreamsConfig.DEFAULT_WINDOWED_KEY_SERDE_INNER_CLASS : 
>>> StreamsConfig.DEFAULT_WINDOWED_VALUE_SERDE_INNER_CLASS
>>> 
>>> In my case, as I mentioned earlier, StreamsConfig class is not accessible 
>>> from org.apache.kafka.common.serialization package. So, I can’t utilize it. 
>>> Any suggestions here?
>>> 
>>> Best,
>>> Daniyar Yeralin
>>> 
>>> 
>>>> On Jul 18, 2019, at 8:46 PM, Matthias J. Sax  wrote:
>>>> 
>>>> Thanks!
>>>> 
>>>> One minor question about the configs. The KIP adds three classes, a
>>>> Serializer, a Deserializer, and a Serde.
>>>> 
>>>> Hence, would it make sense to add the corresponding configs to
>>>> `ConsumerConfig`, `ProducerConfig`, and `StreamsConfig` using slightly
>>>> different names each time?
>>>> 
>>>> 
>>>> Somethin like this:
>>>> 
>>>> ProducerConfig:
>>>> 
>>>> list.key/value.serializer.type
>>>> list.key/value.serializer.inner
>>>> 
>>>> ConsumerConfig:
>>>> 
>>>> list.key/value.deserializer.type
>>>> list.key/value.deserializer.inner
>>>> 
>>>> StreamsConfig:
>>>> 
>>>> default.list.key/value.serde.type
>>>> default.list.key/value.serde.inner
>>>> 
>>>> 
>>>> Adding `d.l.k/v.serde.t/i` to `CommonClientConfigs does not sound right
>>>> to me. Also note, that it seems better to avoid the `default.` prefix
>>>> for consumers and producers because there is only one Serializer or
>>>> Deserializer anyway. Only for Streams, there are multiple and
>>>> StreamsConfig specifies the default one of an operator does not
>>>> overwrite it.
>>>> 
>>>> Thoughts?
>>>> 
>>>> 
>>>> Also, the KIP should explicitly mention to what classed certain configs
>>>> are added. Atm, the KIP only list parameter names, but does not state
>>>> where those are added.
>>>> 
>>>> 
>>>> -Matthias
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On 7/16/19 1:11 PM, Development wrote:
>>>>> Hi,
>>>>> 
>>>>> Yes, totally forgot about the statement. KIP-466 is updated.
>>>>> 
>>>>> Thank you so much John Roesler, Matthias J. Sax, Sophie Blee-Goldman for 
>>>>> your valuable input!
>>>>> 
>>>>> I hope I did not cause too much trouble :)
>>>>> 
>>>>> I’ll start the vote now.
>>>>> 
>>>>> Best,
>>>>> Daniyar Yeralin
>>>>> 
>>>>>> On Jul 16, 2019, at 3:17 PM, John Roesler  wrote:
>>>>>> 
>>>>>> Hi Daniyar,
>>>>>> 
>>>>>> Thanks for that update. I took a look, and I think this is in good shape.
>>>>>> 
>>>>>> One note, the statement "New method public static  Serde>
>>>>>> ListSerde() in org.apache.kafka.common.serialization.Serde

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

Hey Matthias,

Yes, you are totally right, “list.key/value.serializer.type" in 
ProducerConfigs. Removed!

And yes, now StreamsConfig just points to configs stored in CommonClientsConfig.

I’ll update the KIP.

I think we can continue with voting now.

Best,
Daniyar Yeralin

> On Jul 23, 2019, at 9:08 PM, Matthias J. Sax  wrote:
> 
>>> Just to make sure I understand the problem you're highlighting:
>>> I guess the difference is that the serializer and deserializer that are
>>> nested inside the serde also need to be configured? So, by default I'd have
>>> to specify all six configs when I'm using Streams?
> 
> That is not the problem. And you actually describe the solution for it
> yourself:
> 
>>> I guess in the Serde, it could make use of a package-protected constructor
>>> for the serializer and deserializer that fixes the list type and inner type
>>> to the serde-configured ones. Then, when you're configuring Streams, you
>>> only need to specify the StreamsConfigs.
> 
> 
> 
> 
> The problem is, that `ListSerde` is in package `clients` and thus
> `ListSerde` cannot access `StreamsConfig`, and hence cannot use
> `StreamsConfig#DEFAULT_LIST_KEY_SERDE_TYPE` (and others). Therefore, we
> either need to hard-code strings literal for the config names (what does
> not sound right) or add `CommonClientConfig#DEFAULT_LIST_KEY_SERDE_TYPE`
> (and others).
> 
> In StreamsConfig we would just redefine them for convenience:
> 
>> public static final String DEFAULT_LIST_KEY_SERDE_TYPE = 
>> CommonClientConfig#DEFAULT_LIST_KEY_SERDE_TYPE;
> 
> 
> Note that `TimeWindowSerde` is contained in `streams` package and thus
> it can access `StreamsConfig` and
> `StreamsConfig#DEFAULT_WINDOWED_KEY_SERDE_INNER_CLASS`.
> 
> 
> 
> 
> Btw: I just realized that we actually don't need `ProducerConfig`
> 
>> list.key/value.serializer.type
> 
> because the list-type is irrelevant on write. We only need `inner` config.
> 
> 
> 
> -Matthias
> 
> 
> On 7/23/19 1:30 PM, John Roesler wrote:
>> Hmm, that's a tricky situation.
>> 
>> I think Daniyar was on the right track... Producer only cares about
>> serializer configs, and Consumer only cares about deserializer configs.
>> 
>> I didn't see the problem with your proposal:
>> 
>> ProducerConfig:
>>> list.key/value.serializer.type
>>> list.key/value.serializer.inner
>>> ConsumerConfig:
>>> list.key/value.deserializer.type
>>> list.key/value.deserializer.inner
>>> StreamsConfig:
>>> default.list.key/value.serde.type
>>> default.list.key/value.serde.inner
>> 
>> 
>> It seems like the key/value serde configs are a better analogy than the
>> windowed serde.
>> ProducerConfig: key.serializer
>> ConsumerConfig: key.deserializer
>> StreamsConfig: default.key.serde
>> 
>> Just to make sure I understand the problem you're highlighting:
>> I guess the difference is that the serializer and deserializer that are
>> nested inside the serde also need to be configured? So, by default I'd have
>> to specify all six configs when I'm using Streams?
>> 
>> I guess in the Serde, it could make use of a package-protected constructor
>> for the serializer and deserializer that fixes the list type and inner type
>> to the serde-configured ones. Then, when you're configuring Streams, you
>> only need to specify the StreamsConfigs.
>> 
>> Does that work?
>> -John
>> 
>> 
>> On Tue, Jul 23, 2019 at 11:39 AM Development  wrote:
>> 
>>> Bump
>>> 
>>>> On Jul 22, 2019, at 11:26 AM, Development  wrote:
>>>> 
>>>> Hey Matthias,
>>>> 
>>>> It looks a little confusing, but I don’t have enough expertise to judge
>>> on the configuration placement.
>>>> 
>>>> If you think, it is fine I’ll go ahead with this approach.
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>>> 
>>>>> On Jul 19, 2019, at 5:49 PM, Matthias J. Sax 
>>> wrote:
>>>>> 
>>>>> Good point.
>>>>> 
>>>>> I guess the simplest solution is, to actually add
>>>>> 
>>>>>>> default.list.key/value.serde.type
>>>>>>> default.list.key/value.serde.inner
>>>>> 
>>>>> to both `CommonClientConfigs` and `StreamsConfig`.
>>>>> 
>>>>> It's not super clean, but I think it's the best we can do. Thoughts?

Re: [DISCUSS] KIP-466: Add support for List serialization and deserialization

[Development]

KIP-466 is updated and new commit is pushed.

Thank you guys!

> On Jul 24, 2019, at 10:53 AM, John Roesler  wrote:
> 
> Ah, thanks for setting me straight, Matthias.
> 
> Given the choice between defining the Serde in the streams module (hence it
> would not be in the Serdes "menu" class) or defining the configuration
> property in CommonClientConfig, I think I'm leaning toward the latter.
> 
> Really good catch on the ProducerConfig; otherwise, I think we should go
> ahead and add the serializer/deserializer configs as discussed to
> ProducerConfig and ConsumerConfig. It's just cleaner and more uniform that
> way.
> 
> Thanks again,
> -John
> 
> On Tue, Jul 23, 2019 at 8:08 PM Matthias J. Sax 
> wrote:
> 
>>>> Just to make sure I understand the problem you're highlighting:
>>>> I guess the difference is that the serializer and deserializer that are
>>>> nested inside the serde also need to be configured? So, by default I'd
>> have
>>>> to specify all six configs when I'm using Streams?
>> 
>> That is not the problem. And you actually describe the solution for it
>> yourself:
>> 
>>>> I guess in the Serde, it could make use of a package-protected
>> constructor
>>>> for the serializer and deserializer that fixes the list type and inner
>> type
>>>> to the serde-configured ones. Then, when you're configuring Streams, you
>>>> only need to specify the StreamsConfigs.
>> 
>> 
>> 
>> 
>> The problem is, that `ListSerde` is in package `clients` and thus
>> `ListSerde` cannot access `StreamsConfig`, and hence cannot use
>> `StreamsConfig#DEFAULT_LIST_KEY_SERDE_TYPE` (and others). Therefore, we
>> either need to hard-code strings literal for the config names (what does
>> not sound right) or add `CommonClientConfig#DEFAULT_LIST_KEY_SERDE_TYPE`
>> (and others).
>> 
>> In StreamsConfig we would just redefine them for convenience:
>> 
>>> public static final String DEFAULT_LIST_KEY_SERDE_TYPE =
>> CommonClientConfig#DEFAULT_LIST_KEY_SERDE_TYPE;
>> 
>> 
>> Note that `TimeWindowSerde` is contained in `streams` package and thus
>> it can access `StreamsConfig` and
>> `StreamsConfig#DEFAULT_WINDOWED_KEY_SERDE_INNER_CLASS`.
>> 
>> 
>> 
>> 
>> Btw: I just realized that we actually don't need `ProducerConfig`
>> 
>>> list.key/value.serializer.type
>> 
>> because the list-type is irrelevant on write. We only need `inner` config.
>> 
>> 
>> 
>> -Matthias
>> 
>> 
>> On 7/23/19 1:30 PM, John Roesler wrote:
>>> Hmm, that's a tricky situation.
>>> 
>>> I think Daniyar was on the right track... Producer only cares about
>>> serializer configs, and Consumer only cares about deserializer configs.
>>> 
>>> I didn't see the problem with your proposal:
>>> 
>>> ProducerConfig:
>>>> list.key/value.serializer.type
>>>> list.key/value.serializer.inner
>>>> ConsumerConfig:
>>>> list.key/value.deserializer.type
>>>> list.key/value.deserializer.inner
>>>> StreamsConfig:
>>>> default.list.key/value.serde.type
>>>> default.list.key/value.serde.inner
>>> 
>>> 
>>> It seems like the key/value serde configs are a better analogy than the
>>> windowed serde.
>>> ProducerConfig: key.serializer
>>> ConsumerConfig: key.deserializer
>>> StreamsConfig: default.key.serde
>>> 
>>> Just to make sure I understand the problem you're highlighting:
>>> I guess the difference is that the serializer and deserializer that are
>>> nested inside the serde also need to be configured? So, by default I'd
>> have
>>> to specify all six configs when I'm using Streams?
>>> 
>>> I guess in the Serde, it could make use of a package-protected
>> constructor
>>> for the serializer and deserializer that fixes the list type and inner
>> type
>>> to the serde-configured ones. Then, when you're configuring Streams, you
>>> only need to specify the StreamsConfigs.
>>> 
>>> Does that work?
>>> -John
>>> 
>>> 
>>> On Tue, Jul 23, 2019 at 11:39 AM Development  wrote:
>>> 
>>>> Bump
>>>> 
>>>>> On Jul 22, 2019, at 11:26 AM, Development  wrote:
>>>>> 
>>>>> Hey Matthias,
>>>>> 
>>>>> It looks a little conf

Re: [VOTE] KIP-466: Add support for List serialization and deserialization

[Development]

Hi,

Thank you everyone! 

KIP-466 Add support for List serialization and deserialization will be 
marked as accepted with 3 binding votes:
Bill Bejeck, Guozhang Wang, and Matthias J. Sax.

Best,
Daniyar Yeralin

> On Jul 24, 2019, at 5:12 PM, Bill Bejeck  wrote:
> 
> Thanks for the KIP looks to be very helpful.
> 
> +1(binding)
> 
> -Bill
> 
> On Wed, Jul 24, 2019 at 5:01 PM Guozhang Wang  wrote:
> 
>> +1 (binding).
>> 
>> Thanks Daniyar!
>> 
>> On Wed, Jul 24, 2019 at 12:04 PM John Roesler  wrote:
>> 
>>> Thanks, Daniyar,
>>> 
>>> I'm +1 (nonbinding)
>>> 
>>> -John
>>> 
>>> On Tue, Jun 11, 2019 at 1:45 PM Development  wrote:
>>> 
>>>> Hello,
>>>> 
>>>> I want to start a vote for KIP-466 <
>>>> 
>>> 
>> 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
>>>>> 
>>>> "Add support for List serialization and deserialization”.
>>>> The implementation can be found as a PR <
>>>> https://github.com/apache/kafka/pull/6592 <
>>>> https://github.com/apache/kafka/pull/6592>>.
>>>> 
>>>> Thank you all for your input and support.
>>>> 
>>>> Best,
>>>> Daniyar Yeralin
>>> 
>> 
>> 
>> --
>> -- Guozhang
>> 

Help needed with PR #6592

[Development]

Hi,

I’ve been maintaining this PR "KAFKA-8326: Introduce List Serde" 
https://github.com/apache/kafka/pull/6592 
 My linters keep failing during the 
building, complaining about: "Disallowed import - 
org.apache.kafka.clients.CommonClientConfigs.” in my list (de)serializer 
classes. However, it was decided that those import must be there during KIP 
discussions.

Thank you!

Best,
Daniyar Yeralin

PR Broken builds

[Development]

Hi,

I’ve been working on KAFKA-8326 PR (https://github.com/apache/kafka/pull/6592 
), but I can never pass the checks. 
The build keeps failing with unrelated errors from SpotBugs. Seems like other 
people’s PRs are also affected. What’s the current process on merging PRs in 
such a case? 

Thank you!

Best,
Daniyar Yeralin