Current state: Discarded
Discussion thread: here
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Update: This KIP was discarded in favor of moving the code from the
core) module to other modules. Once that effort is completed,
core) will be empty and a separate KIP will propose its removal (along with proposed alternatives).
Since Scala 2 is not binary compatible across minor versions, a separate
core ) artifact is published for each supported Scala version (as is typical for Scala projects). More concretely, we currently publish kafka_2.12 and kafka_2.13 for Scala 2.12 and 2.13 respectively. This requires building the project and running all the tests once for each supported Scala version. In addition, it's not uncommon for contributors to have to fix pull requests so that they work on both Scala versions.
Projects written in Java can use any of the two jars (i.e. there is no benefit in having both artifacts), but projects written in Scala should use the jar with the matching Scala version. It is worth noting that the
kafka jar does not expose any public API, so we are doing extra work to support Scala users who access internal APIs. That said, it's not uncommon for users and other projects to depend on internal broker classes to start an embedded kafka cluster for testing purposes (we should have a public API for testing, but that's a subject for another KIP).
As part of KIP-751, we deprecated support for Scala 2.12 with the goal to remove it in Apache 4.0 – that is, a single Scala version would be supported at that point. I propose we take the chance to formalize that only a single Scala version will be supported by the
core ) module from Apache Kafka 4.0 and the artifact name should be changed to be simply
kafka (i.e. the Scala version suffix will be removed).
Rename Maven artifact
kafka in Apache Kafka 4.0.
Update the build to achieve what's been mentioned in the
Public Interfaces section.
Compatibility, Deprecation, and Migration Plan
Users and projects that depend on
kafka_2.13 would have to change their build to refer to
Projects written in Scala that are using a different version than the one
kafka supports would have to either use a separate classloader, shading or running kafka in a separate process via testcontainers (or similar).
Verify that the published artifact has the updated name.
Maintain the status quo.