[FLINK-20845] Drop support for Scala 2.11

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.15.0
• Component/s: API / Scala
• Labels: auto-unassigned pull-request-available

Release Note

Support for Scala 2.11 has been removed. All Flink dependencies that (transitively) depend on Scala are suffixed with the Scala version that they are built for, for example flink-streaming-scala_2.12. Users should update all Flink dependecies, changing "2.11" to "2.12". For example, "flink-streaming-java_2.11" needs to be changed to "flink-streaming-java_2.12".

Scala versions (2.11, 2.12, etc.) are not binary compatible with one another. That also means that there's no guarantee that you can restore from a savepoint, made with a Flink Scala 2.11 application, if you're upgrading to a Flink Scala 2.12 application. This depends on the data types that you have been using in your application.

• Assignee: Nick Burkard
• Reporter: Nick Burkard
• Created: 04/Jan/21 14:10
• Updated: 26/Apr/22 09:40
• Resolved: 30/Sep/21 10:22

Description

The first step to adding support for Scala 2.13 is to drop Scala 2.11. Community discussion can be found here.

• Scala 2.11 was released in November 2017 and is quite old now. Most open-source libraries no longer build for it.
• Upgrading libraries to support 2.13 will be much easier without 2.11. Many do not support 2.11, 2.12 and 2.13 at the same time, so this is basically required to get 2.13 support.

Considerations:

• The Flink Scala Shell submodule still does not support Scala 2.12. It isn't a strict dependency for dropping Scala 2.11, but would be nice to have before making the cut.
• Stateful functions previously needed Scala 2.11, but it looks like it now supports 2.12.

Issue Links

• blocks: FLINK-21214 FlinkKafkaProducerITCase.testScaleDownBeforeFirstCheckpoint Failed
• blocks: FLINK-19168 Upgrade Kafka client version beyond 2.5.0
• is blocked by: FLINK-24360 Drop Scala Shell
• is related to: FLINK-23996 Make Scala 2.12 default build target
• relates to: FLINK-22441 In Flink v1.11.3 contains netty(version:3.10.6) netty(version:4.1.60) . There are many vulnerabilities, like CVE-2021-21409 etc. please confirm these version and fix. thx
• relates to: FLINK-27413 Drop scala 2.11 support from the flink-docker
• links to: GitHub Pull Request #14544