Hi all, The Kafka build currently includes support for Scala 2.9, which means that it cannot take advantage of features introduced in Scala 2.10 or depend on libraries that require it.
This restricts the solutions available while trying to solve existing issues. I was browsing JIRA looking for areas to contribute and I quickly ran into two issues where this is the case: * KAFKA-1351: "String.format is very expensive in Scala" could be solved nicely by using the String interpolation feature introduced in Scala 2.10. * KAFKA-1595: "Remove deprecated and slower scala JSON parser from kafka.consumer.TopicCount" could be solved by using an existing JSON library, but both jackson-scala and play-json require 2.10 (argonaut supports Scala 2.9, but it brings other dependencies like scalaz). We can workaround this by writing our own code instead of using libraries, of course, but it's not ideal. Other features like Scala Futures and value classes would also be useful in some situations, I would think (for a more extensive list of new features, see http://scala-language.1934581.n4.nabble.com/Scala-2-10-0-now-available-td4634126.html ). Another pain point of supporting 2.9.x is that it doubles the number of build and test configurations required from 2 to 4 (because the 2.9.x series was not necessarily binary compatible). A strong argument for maintaining support for 2.9.x was the client library, but that has been rewritten in Java. It's also worth mentioning that Scala 2.9.1 was released in August 2011 (more than 3.5 years ago) and the 2.9.x series hasn't received updates of any sort since early 2013. Scala 2.10.0, in turn, was released in January 2013 (over 2 years ago) and 2.10.5, the last planned release in the 2.10.x series, has been recently released (so even 2.10.x won't be receiving updates any longer). All in all, I think it would not be unreasonable to drop support for Scala 2.9.x in a future release, but I may be missing something. What do others think? Ismael
