[FLINK-4134] EventTimeSessionWindows trigger for empty windows when dropping late events

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.3
• Fix Version/s: 1.1.0
• Component/s: API / DataStream
• Assignee: Stefan Richter
• Reporter: Stefan Richter
• Created: 30/Jun/16 12:47
• Updated: 04/Jul/16 15:26
• Resolved: 04/Jul/16 15:25

Description

It seems like EventTimeSessionWindows sometimes trigger for empty windows. The behavior is observed in connection with dropping late events:

stream
 .keyBy("sessionKey")
 .window(EventTimeSessionWindows.withGap(Time.milliseconds(100)))
 .allowedLateness(Time.milliseconds(0))
 .apply(new ValidatingWindowFunction())
 .print();

I wrote a generator that generates events for several parallel sessions and that allows to reproduce the error. For now, I can share this generator privately for debugging purposes, but my plan is to use the generator as basis for an integration test.

Issue Links

• links to: GitHub Pull Request #2196