As Gwen said, my initial thought is that message transformations that are "more than trivial" should rather be done by Kafka Streams, rather than by Kafka Connect (for the reasons that Gwen mentioned).
Transforming one message at a time would be a good fit for Kafka Connect. An important use case is to remove sensitive data (such as PII) from an incoming data stream before it hits Kafka's persistent storage -- this use case can't be implemented well with Kafka Streams because, by design, Kafka Streams is meant to read its input data from Kafka (i.e. at the point when Kafka Streams could be used to removed sensitive data fields the data is already stored persistently in Kafka, and this might be a no-go depending on the use case). I'm of course interested to hear what other people think. On Tue, Jul 12, 2016 at 6:06 AM, Gwen Shapira <g...@confluent.io> wrote: > I think we need to restrict the functionality to one-message-at-a-time. > > Basically, connect gives very little guarantees about the size of the set > of the composition (you may get same messages over and over, mix of old and > new, etc) > > In order to do useful things over a collection, you need better defined > semantics of what's included. Kafka Streams is putting tons of effort into > having good windowing semantics, and I think apps that require modification > of collections are a better fit there. > > I'm willing to change my mind though (have been known to happen) - what are > the comments about usage that point toward the collections approach? > > Gwen > > On Mon, Jul 11, 2016 at 3:32 PM, Nisarg Shah <snis...@gmail.com> wrote: > > > Thanks Jay, added that to the KIP. > > > > Besides reviewing the KIP as a whole, I wanted to know about what > everyone > > thinks about what data should be dealt at the Transformer level. > Transform > > the whole Collection of Records (giving the flexibility of modifying > > messages across the set) OR > > Transform messages one at a time, iteratively. This will restrict > > modifications across messages. > > > > I’ll get a working sample ready soon, to have a look. There were some > > comments about Transformer usage that pointed to the first approach, > which > > I prefer too given the flexibility. > > > > > On Jul 11, 2016, at 2:49 PM, Jay Kreps <j...@confluent.io> wrote: > > > > > > One minor thing, the Transformer interface probably needs a close() > > method > > > (i.e. the opposite of initialize). This would be used for any > transformer > > > that uses a resource like a file/socket/db connection/etc that needs to > > be > > > closed. You usually don't need this but when you do need it you really > > need > > > it. > > > > > > -Jay > > > > > > On Mon, Jul 11, 2016 at 1:47 PM, Nisarg Shah <snis...@gmail.com> > wrote: > > > > > >> Hello, > > >> > > >> This KIP < > > >> > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-66:+Add+Kafka+Connect+Transformers+to+allow+transformations+to+messages > > > > > >> is for KAFKA-3209 <https://issues.apache.org/jira/browse/KAFKA-3209>. > > >> It’s about capabilities to transform messages in Kafka Connect. > > >> > > >> Some design decisions need to be taken, so please advise me on the > same. > > >> Feel free to express any thoughts or concerns as well. > > >> > > >> Many many thanks to Ewen Cheslack-Postava. > > >> > > >> -Nisarg > > > > > -- Best regards, Michael Noll *Michael G. Noll | Product Manager | Confluent | +1 650.453.5860Download Apache Kafka and Confluent Platform: www.confluent.io/download <http://www.confluent.io/download>*
