[KAFKA-14864] Memory leak in KStreamWindowAggregate with ON_WINDOW_CLOSE emit strategy

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0, 3.3.2
• Fix Version/s: 3.5.0, 3.4.1, 3.3.3
• Component/s: streams
• Assignee: Victoria Xia
• Reporter: Victoria Xia
• Created: 28/Mar/23 23:16
• Updated: 04/Apr/23 05:09
• Resolved: 04/Apr/23 05:09

Description

The Streams DSL processor implementation for the ON_WINDOW_CLOSE emit strategy during KStream windowed aggregations opens a key-value iterator but does not call `close()` on it (link), despite the Javadocs for the iterator making clear that users must do so in order to release resources (link).  

I discovered this bug while running load testing benchmarks and noticed that some runs were sporadically hitting OOMs, so it is definitely possible to hit this in practice.

Issue Links

• links to: GitHub Pull Request #13470