Just some notes on the KIP doc itself: * It'd be useful to clarify at what point the plain consumer + custom code + producer breaks down. I think trivial filtering and aggregation on a single stream usually work fine with this model. Anything where you need more complex joins, windowing, etc. are where it breaks down. I think most interesting applications require that functionality, but it's helpful to make this really clear in the motivation -- right now, Kafka only provides the lowest level plumbing for stream processing applications, so most interesting apps require very heavyweight frameworks. * I think the feature comparison of plain producer/consumer, stream processing frameworks, and this new library is a good start, but we might want something more thorough and structured, like a feature matrix. Right now it's hard to figure out exactly how they relate to each other. * I'd personally push the library vs. framework story very strongly -- the total buy-in and weak integration story of stream processing frameworks is a big downside and makes a library a really compelling (and currently unavailable, as far as I am aware) alternative. * Comment about in-memory storage of other frameworks is interesting -- it is specific to the framework, but is supposed to also give performance benefits. The high-level functional processing interface would allow for combining multiple operations when there's no shuffle, but when there is a shuffle, we'll always be writing to Kafka, right? Spark (and presumably spark streaming) is supposed to get a big win by handling shuffles such that the data just stays in cache and never actually hits disk, or at least hits disk in the background. Will we take a hit because we always write to Kafka? * I really struggled with the structure of the KIP template with Copycat because the flow doesn't work well for proposals like this. They aren't as concrete changes as the KIP template was designed for. I'd completely ignore that template in favor of optimizing for clarity if I were you.
-Ewen On Thu, Jul 23, 2015 at 5:59 PM, Guozhang Wang <wangg...@gmail.com> wrote: > Hi all, > > I just posted KIP-28: Add a transform client for data processing > < > https://cwiki.apache.org/confluence/display/KAFKA/KIP-28+-+Add+a+transform+client+for+data+processing > > > . > > The wiki page does not yet have the full design / implementation details, > and this email is to kick-off the conversation on whether we should add > this new client with the described motivations, and if yes what features / > functionalities should be included. > > Looking forward to your feedback! > > -- Guozhang > -- Thanks, Ewen
