[KAFKA-10298] Replace Windows with a proper interface

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: streams
• Assignee: John Roesler
• Reporter: John Roesler
• Created: 21/Jul/20 19:37
• Updated: 17/Aug/20 15:17

Description

See POC: https://github.com/apache/kafka/pull/9031

 

Presently, windowed aggregations in KafkaStreams fall into two categories:

• Windows
  • TimeWindows
  • UnlimitedWindows
  • JoinWindows
• SessionWindows

Unfortunately, Windows is an abstract class instead of an interface, and it forces some fields onto its implementations. This has led to a number of problems over the years, but so far we have been able to live with them.

However, as we consider adding new implementations to this side of the hierarchy, the damage will spread. See KIP-450, for example.

We should take the opportunity now to correct the issue by introducing an interface and deprecating Windows itself. Then, we can implement new features cleanly and maybe remove Windows in the 3.0 release.

Issue Links

• blocks: KAFKA-10408 Calendar based windows
• links to: GitHub Pull Request #9031
• links to: https://github.com/apache/kafka/pull/9031
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