@Jan: The `Produced` class was introduced in 1.0 to specify key and valud Serdes (and partitioner) if data is written into a topic.
Old API:
KStream#to("topic", keySerde, valueSerde);
New API:
KStream#to("topic", Produced.with(keySerde, valueSerde));
This allows to reduce the number of overloads for `to()` (and
`through()` that follows the same pattern) -- the second parameter is
used to cover all different variations of option parameters users can
specify, while we only have 2 overload for `to()` itself.
What is still unclear to me it, what you mean by this topic prefix
thing? Either a user cares about the topic name and thus, must create
and manage it manually. Or the user does not care, and Streams create
it. How would this prefix idea fit in here?
@Guozhang:
My idea was to extend `Produced` with the hint we want to give for
creating internal topic and pass a optional `Produced` parameter. There
are multiple things we can do here:
1) stream.through(null, Produced...).groupBy().aggregate()
-> just allow for `null` topic name indicating that Streams should
create an internal topic
2) stream.through(Produced...).groupBy().aggregate()
-> add one overload taking an mandatory `Produced`
We use `Serialized` to picky back the information
3) stream.groupBy(Serialized...).aggregate()
and stream.groupByKey(Serialized...).aggregate()
-> we don't need new top level overloads
There are different trade-offs for those alternatives and maybe there
are other ways to change the API. It's just to push the discussion further.
-Matthias
On 11/12/17 1:22 PM, Jan Filipiak wrote:
> Hi Gouzhang,
>
> this felt like these questions are supposed to be answered by me.
> I do not understand the first one. I don't understand why the user
> shouldn't be able to specify a suffix for the topic name.
>
> For the third question I am not 100% familiar if the Produced class
> came to existence
> at all. I remember proposing it somewhere in our redo DSL discussion that
> I dropped out of later. Finally any call that does:
>
> 1. create the internal topic
> 2. register sink
> 3. register source
>
> will always get the work done. If we have a Produced like class. putting
> all the parameters
> in there make sense. (Partitioner, serde, PartitionHint, internal, name
> ... )
>
> Hope this helps?
>
>
> On 10.11.2017 07:54, Guozhang Wang wrote:
>> A few clarification questions on the proposal details.
>>
>> 1. API: although the repartition only happens at the final stateful
>> operations like agg / join, the repartition flag info was actually passed
>> from an earlier operator like map / groupBy. So what should be the new
>> API
>> look like? For example, if we do
>>
>> stream.groupBy().through("topic-name", Produced..).aggregate
>>
>> This would be add a bunch of APIs to GroupedKStream/KTable
>>
>> 2. Semantics: as Matthias mentioned, today any topics defined in
>> "through()" call is considered a user topic, and hence users are
>> responsible for managing them, including the topic name. For this KIP's
>> purpose, though, users would not care about the topic name. I.e. as a
>> user
>> I still want to make it be an internal topic so that I do not need to
>> worry
>> about it at all, but only specify num.partitions.
>>
>> 3. Details: in Produced we do not have specs for specifying the
>> num.partitions or should we repartition or not. So it is still not
>> clear to
>> me how we would make use of that to achieve what's in the old
>> proposal's RepartitionHint class.
>>
>>
>>
>> Guozhang
>>
>>
>> On Mon, Nov 6, 2017 at 1:21 PM, Ted Yu <yuzhih...@gmail.com> wrote:
>>
>>> bq. enlarge the score of through()
>>>
>>> I guess you meant scope.
>>>
>>> On Mon, Nov 6, 2017 at 1:15 PM, Jeyhun Karimov <je.kari...@gmail.com>
>>> wrote:
>>>
>>>> Hi,
>>>>
>>>> Sorry for the late reply. I am convinced that we should enlarge the
>>>> score
>>>> of through() (add more overloads) instead of introducing a separate set
>>> of
>>>> overloads to other methods.
>>>> I will update the KIP soon based on the discussion and inform.
>>>>
>>>>
>>>> Cheers,
>>>> Jeyhun
>>>>
>>>> On Mon, Nov 6, 2017 at 9:18 PM Jan Filipiak <jan.filip...@trivago.com>
>>>> wrote:
>>>>
>>>>> Sorry for not beeing 100% up to date.
>>>>> Back then we had the discussion that when an operation puts a >Sink<
>>>>> into the topology, a >Produced<
>>>>> parameter is added. This produced parameter could have internal or
>>>>> external. If internal I think the name would still make
>>>>> a great suffix for the topic name
>>>>>
>>>>> Is this plan still around? Otherwise having the name as suffix is
>>>>> probably always good it can help the user quicker to identify hot
>>> topics
>>>>> that need more
>>>>> partitions if he has many of these internal repartitions
>>>>>
>>>>> Best Jan
>>>>>
>>>>>
>>>>> On 06.11.2017 20:13, Matthias J. Sax wrote:
>>>>>> I absolute agree with what you say. It's not a requirement to
>>> specify a
>>>>>> topic name -- and this was the idea -- if user does specify a name,
>>> we
>>>>>> treat as is -- if users does not specify a name, Streams create an
>>>>>> internal topic.
>>>>>>
>>>>>> The goal of the Jira is to allow a simplified way to control
>>>>>> repartitioning (atm, user needs to manually create a topic and use
>>> via
>>>>>> through()).
>>>>>>
>>>>>> Thus, the idea is to make the topic name parameter of through
>>> optional.
>>>>>> It's of course just an idea. Happy do have a other API design. The
>>> goal
>>>>>> was, to avoid to many new overloads.
>>>>>>
>>>>>>>> Could you clarify exactly what you mean by keeping the current
>>>>> distinction?
>>>>>> Current distinction is: user topics are created manually and user
>>>>>> specifies the name -- internal topics are created by Kafka Streams
>>> and
>>>>>> an name is generated automatically.
>>>>>>
>>>>>> -> through("user-topic")
>>>>>> -> through(TopicConfig.withNumberOfPartitions(5)) // Streams creates
>>>> an
>>>>>> internal topic
>>>>>>
>>>>>>
>>>>>> -Matthias
>>>>>>
>>>>>>
>>>>>> On 11/6/17 6:56 PM, Thomas Becker wrote:
>>>>>>> Could you clarify exactly what you mean by keeping the current
>>>>> distinction?
>>>>>>> Actually, re-reading the KIP and JIRA, it's not clear that being
>>> able
>>>>> to specify a custom name is actually a requirement. If the goal is to
>>>>> control repartitioning and tune parallelism, maybe we can just
>>>>> sidestep
>>>>> this issue altogether by removing the ability to set a different name.
>>>>>>> On Mon, 2017-11-06 at 16:51 +0100, Matthias J. Sax wrote:
>>>>>>>
>>>>>>> That's a good point. In current design, we strictly distinguish
>>> both.
>>>>>>> For example, the reset tools deletes internal topics (starting with
>>>>>>> prefix `<application.id>-` and ending with either `-repartition` or
>>>>>>> `-changelog`.
>>>>>>>
>>>>>>> Thus, from my point of view, it would make sense to keep the current
>>>>>>> distinction.
>>>>>>>
>>>>>>> -Matthias
>>>>>>>
>>>>>>> On 11/6/17 4:45 PM, Thomas Becker wrote:
>>>>>>>
>>>>>>>
>>>>>>> I think this sounds good as well. It's worth clarifying whether
>>> topics
>>>>> that are named by the user but created by streams are considered
>>>> "internal"
>>>>> topics also.
>>>>>>> On Sun, 2017-11-05 at 23:02 +0100, Matthias J. Sax wrote:
>>>>>>>
>>>>>>> My idea was, to relax the requirement for through() that a topic
>>> must
>>>> be
>>>>>>> created manually before startup.
>>>>>>>
>>>>>>> Thus, if no through() call is made, a (internal) topic is created
>>> the
>>>>>>> same way we do it currently.
>>>>>>>
>>>>>>> If one uses `through(String topicName)` we keep the current behavior
>>>> and
>>>>>>> require users to create the topic manually.
>>>>>>>
>>>>>>> The reasoning is as follows: if a user creates a topic manually, a
>>>> user
>>>>>>> can just use it for repartitioning. As the topic is already there,
>>>> there
>>>>>>> is no need to specify any topic configs.
>>>>>>>
>>>>>>> We add a new `through()` overload (details TBD) that allows to
>>> specify
>>>>>>> topic configs and Streams create the topic with those configs.
>>>>>>>
>>>>>>> Reasoning: user don't want to manage topic manually, thus, it's
>>> still
>>>> an
>>>>>>> internal topic and Streams create the topic name automatically as
>>> for
>>>>>>> all other internal topics. However, users gets some more control
>>> about
>>>>>>> topic parameters like number of partitions (we should discuss what
>>>> other
>>>>>>> configs would be useful).
>>>>>>>
>>>>>>>
>>>>>>> Does this make sense?
>>>>>>>
>>>>>>>
>>>>>>> -Matthias
>>>>>>>
>>>>>>>
>>>>>>> On 11/5/17 1:21 AM, Jan Filipiak wrote:
>>>>>>>
>>>>>>>
>>>>>>> Hi.
>>>>>>>
>>>>>>>
>>>>>>> Im not 100 % up to date what version 1.0 DSL looks like ATM.
>>>>>>> I just would argue that repartitioning should be an own API call
>>> like
>>>>>>> through or something.
>>>>>>> One can use through or to already to get this. I would argue one
>>>> should
>>>>>>> look there instead of overloads
>>>>>>>
>>>>>>> Best Jan
>>>>>>>
>>>>>>> On 04.11.2017 16:01, Jeyhun Karimov wrote:
>>>>>>>
>>>>>>>
>>>>>>> Dear community,
>>>>>>>
>>>>>>> I would like to initiate discussion on KIP-221 [1] based on issue
>>> [2].
>>>>>>> Please feel free to comment.
>>>>>>>
>>>>>>> [1]
>>>>>>>
>>>>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
>>>> 221%3A+Repartition+Topic+Hints+in+Streams
>>>>>>> [2] https://issues.apache.org/jira/browse/KAFKA-6037
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Cheers,
>>>>>>> Jeyhun
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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