[BEAM-1589] Add OnWindowExpiration method to Stateful DoFn

• Type: New Feature
• Status: Triage Needed
• Priority: P2
• Resolution: Fixed
• Fix Version/s: Missing
• Component/s: runner-core, sdk-java-core
• Labels: Clarified Done stale-P2 stale-assigned
• Assignee: Reuven Lax
• Reporter: Jingsong Lee
• Created: 02/Mar/17 03:38
• Updated: 13/Apr/23 11:01
• Resolved: 15/May/21 17:59

Description

See BEAM-1517
This allows the user to do some work before the state's garbage collection.
It seems kind of annoying, but on the other hand forgetting to set a final timer to flush state is probably data loss most of the time.
FlinkRunner does this work very simply, but other runners, such as DirectRunner, need to traverse all the states to do this, and maybe it's a little hard.

Issue Links

• Blocked: BEAM-2535 Allow explicit output time independent of firing specification for all timers
• is duplicated by: BEAM-5307 Allow injection of state in DoFn.FinishBundle
• links to: GitHub Pull Request #4482
• links to: GitHub Pull Request #11350
• links to: GitHub Pull Request #11773
• links to: GitHub Pull Request #11774