Hi Ismael, Thanks for pointing us towards the direction of a DTO based approach. The AdminClient examples seem very neat and extensible in that sense. Personally, I was trying to think only along the lines of how the current Partitioner interface has been designed, i.e having all requisite parameters as separate arguments (Topic, Key, Value etc).
Regarding this question of yours: A more concrete question: did we consider having the method `partition` > take `ProduceRecord` as one of its parameters and `Cluster` as the other? No, I don't think in the discussion thread it was brought up and as I said it appears that could be due to an attempt to keep the new method's signature similar to the existing one within Partitioner. If I understood the intent of the question correctly, are you trying to hint here that `ProducerRecord` already contains all the arguments that the `partition` method accepts and also has a `headers` field within it. So, instead of adding another method for the `headers` field, why not create a new method taking ProducerRecord directly? If my understanding is correct, then it seems like a very clean way of adding support for `headers`. Anyways, the partition method within KafkaProducer already takes a ProducerRecord as an argument so that makes it easier. Keeping that in mind, should this new method's (which takes a ProducerRecord as an input) default implementation invoke the existing method ? One challenge I see there is that the existing partition method expects serialized keys and values while ProducerRecord doesn't have access to those (It directly operates on K, V). Thanks! Sagar. On Sun, Aug 27, 2023 at 8:51 AM Ismael Juma <m...@ismaeljuma.com> wrote: > A more concrete question: did we consider having the method `partition` > take `ProduceRecord` as one of its parameters and `Cluster` as the other? > > Ismael > > On Sat, Aug 26, 2023 at 12:50 PM Greg Harris <greg.har...@aiven.io.invalid > > > wrote: > > > Hey Ismael, > > > > > The mention of "runtime" is specific to Connect. When it comes to > > clients, > > one typically compiles and runs with the same version or runs with a > newer > > version than the one used for compilation. This is standard practice in > > Java and not something specific to Kafka. > > > > When I said "older runtimes" I was being lazy, and should have said > > "older versions of clients at runtime," thank you for figuring out > > what I meant. > > > > I don't know how common it is to compile a partitioner against one > > version of clients, and then distribute and run the partitioner with > > older versions of clients and expect graceful degradation of features. > > If you say that it is very uncommon and not something that we should > > optimize for, then I won't suggest otherwise. > > > > > With regards to the Admin APIs, they have been extended several times > > since introduction (naturally). One of them is: > > > > > > https://github.com/apache/kafka/commit/1d22b0d70686aef5689b775ea2ea7610a37f3e8c > > > > Thanks for the example. I also see that includes a migration from > > regular arguments to the DTO style, consistent with your > > recommendation here. > > > > I think the DTO style and the proposed additional argument style are > > both reasonable. > > > > Thanks, > > Greg > > > > On Sat, Aug 26, 2023 at 9:46 AM Ismael Juma <m...@ismaeljuma.com> wrote: > > > > > > Hi Greg, > > > > > > The mention of "runtime" is specific to Connect. When it comes to > > clients, > > > one typically compiles and runs with the same version or runs with a > > newer > > > version than the one used for compilation. This is standard practice in > > > Java and not something specific to Kafka. > > > > > > With regards to the Admin APIs, they have been extended several times > > since > > > introduction (naturally). One of them is: > > > > > > > > > https://github.com/apache/kafka/commit/1d22b0d70686aef5689b775ea2ea7610a37f3e8c > > > > > > Ismael > > > > > > On Sat, Aug 26, 2023 at 8:29 AM Greg Harris > <greg.har...@aiven.io.invalid > > > > > > wrote: > > > > > > > Hey Ismael, > > > > > > > > Thank you for clarifying where the DTO pattern is used already, I did > > > > not have the admin methods in mind. > > > > > > > > > With the DTO approach, you don't create a new DTO, you simply add a > > new > > > > overloaded constructor and accessor to the DTO. > > > > > > > > With this variant, partitioner implementations would receive a > > > > `NoSuchMethodException` when trying to access newer methods in older > > > > runtimes. Do we expect the interface implementers will maintain the > > > > try-catch to support backwards-compatibility? > > > > Fortunately here the Headers type already exists, but in the future > if > > > > a new subtype is added at the same time as the change to the DTO is > > > > made, interface implementers will need to be careful to avoid > > > > NoClassDefFoundErrors. > > > > We used this "add a new method" style extension in > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-610%3A+Error+Reporting+in+Sink+Connectors > > > > and had to be very specific in recommending how users interact with > > > > the new extension point, and there ended up being lots of sharp edges > > > > in practice. > > > > > > > > Do you have any examples of a DTO-based API that has been extended > > > > since it was initially implemented? I'm not familiar with the > > > > evolution of the Admin APIs. > > > > > > > > Thanks! > > > > Greg > > > > > > > > On Sat, Aug 26, 2023 at 6:45 AM Ismael Juma <m...@ismaeljuma.com> > wrote: > > > > > > > > > > Hi Greg, > > > > > > > > > > The point is that the approach proposed here introduces complexity > > > > forever. > > > > > Each new user of this interface that needs access to the parameters > > not > > > > > exposed originally needs to implement the abstract method with an > > empty > > > > > implementation and it needs to override whichever additional > default > > they > > > > > care about (this KIP introduces a second method, but future KIPs > > would > > > > > introduce additional methods for new parameters). One would never > > design > > > > > the interface like this from the start. > > > > > > > > > > With the DTO approach, you don't create a new DTO, you simply add a > > new > > > > > overloaded constructor and accessor to the DTO. The implementers of > > the > > > > > interface still have a single method (two here since we made a > > mistake > > > > > originally) and they can decide which of the values from the DTO > they > > > > would > > > > > like to access. This approach has been the recommended approach for > > years > > > > > and it's how the Admin apis work (they're the most recent client). > An > > > > > example: > > > > > > > > > > createTopics(Collection<NewTopic> newTopics, CreateTopicsOptions > > > > options); > > > > > > > > > > This makes it easy to add new fields to `NewTopic` or > > > > `CreateTopicsOptions`. > > > > > > > > > > Ismael > > > > > > > > > > On Wed, Aug 23, 2023 at 11:48 AM Greg Harris > > > > <greg.har...@aiven.io.invalid> > > > > > wrote: > > > > > > > > > > > Hey Jack, > > > > > > > > > > > > The design of this KIP is also consistent with the way header > > support > > > > > > was added to Connect: > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-440%3A+Extend+Connect+Converter+to+support+headers > > > > > > I think making argument for precedent here is reasonable. > > > > > > > > > > > > Hi Ismael, > > > > > > > > > > > > Can you expand what you mean by "without breaking > compatibility"? I > > > > > > think the approach proposed here (a default method) would be > > backwards > > > > > > compatible. If an implementation wishes to make use of the new > > > > > > signature, they can override the new method and the version of > > Kafka > > > > > > will determine which implementation is used without instance > > checking, > > > > > > reflection, or exceptions. > > > > > > > > > > > > I believe that when you pass a DTO, that some sort of instance > > > > > > checking, reflection, or exceptions would be required for the > > > > > > Partitioner to determine whether additional information is > present. > > > > > > For example, if we wished to add some information X to the > > partitioner > > > > > > in the future, the caller could pass either a `PartitionInfo` or > > > > > > `PartitionInfoWithX` DTO instance, and the callee could use an > > > > > > `instanceof` check and a cast before accessing the X information. > > That > > > > > > seems to be more machinery for the Partitioner implementation to > > > > > > manage as compared to maintaining multiple methods, which may > just > > be > > > > > > one-line calls to other methods. > > > > > > > > > > > > Please let me know if I've misunderstood your DTO design. > > > > > > > > > > > > Thanks! > > > > > > Greg > > > > > > > > > > > > On Tue, Aug 22, 2023 at 9:33 PM Jack Tomy <jacktomy...@gmail.com > > > > > > wrote: > > > > > > > > > > > > > > Hi Ismael, > > > > > > > > > > > > > > That would be totally different from the pattern currently > being > > > > followed > > > > > > > in all the interfaces, for example serializer. > > > > > > > I personally don't favour that either. Let's see if the > community > > > > has any > > > > > > > opinions on the same. > > > > > > > > > > > > > > Hey everyone, please share your thoughts on using a DTO instead > > of > > > > > > separate > > > > > > > params for the interface. > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > On Mon, Aug 21, 2023 at 8:06 PM Ismael Juma <m...@ismaeljuma.com > > > > > > wrote: > > > > > > > > > > > > > > > Hi Jack, > > > > > > > > > > > > > > > > I mean a DTO. That means you can add additional parameters > > later > > > > > > without > > > > > > > > breaking compatibility. The current proposal would result in > > yet > > > > > > another > > > > > > > > method each time we need to add parameters. > > > > > > > > > > > > > > > > Ismael > > > > > > > > > > > > > > > > On Sun, Aug 20, 2023 at 4:53 AM Jack Tomy < > > jacktomy...@gmail.com> > > > > > > wrote: > > > > > > > > > > > > > > > > > Hey Ismael, > > > > > > > > > > > > > > > > > > Are you suggesting to pass a param like a DTO or you are > > > > suggesting > > > > > > to > > > > > > > > pass > > > > > > > > > the record object? > > > > > > > > > > > > > > > > > > I would also like to hear other devs' opinions on this as I > > > > > > personally > > > > > > > > > favour what is done currently. > > > > > > > > > > > > > > > > > > On Thu, Aug 17, 2023 at 9:34 AM Ismael Juma < > > m...@ismaeljuma.com> > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > > > > > > > Thanks for the KIP. The problem outlined here is a great > > > > example > > > > > > why we > > > > > > > > > > should be using a record-like structure to pass the > > parameters > > > > to a > > > > > > > > > method > > > > > > > > > > like this. Then we can add more parameters without having > > to > > > > > > introduce > > > > > > > > > new > > > > > > > > > > methods. Have we considered this option? > > > > > > > > > > > > > > > > > > > > Ismael > > > > > > > > > > > > > > > > > > > > On Mon, Aug 7, 2023 at 5:26 AM Jack Tomy < > > > > jacktomy...@gmail.com> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > Hey everyone. > > > > > > > > > > > > > > > > > > > > > > I would like to call for a vote on KIP-953: partition > > method > > > > to > > > > > > be > > > > > > > > > > > overloaded to accept headers as well. > > > > > > > > > > > > > > > > > > > > > > KIP : > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=263424937 > > > > > > > > > > > Discussion thread : > > > > > > > > > > > > > > > https://lists.apache.org/thread/0f20kvfqkmhdqrwcb8vqgqn80szcrcdd > > > > > > > > > > > > > > > > > > > > > > Thanks > > > > > > > > > > > -- > > > > > > > > > > > Best Regards > > > > > > > > > > > *Jack* > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > Best Regards > > > > > > > > > *Jack* > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > Best Regards > > > > > > > *Jack* > > > > > > > > > > > > >
