[BEAM-8537] Provide WatermarkEstimatorProvider for different types of WatermarkEstimator

• Type: Improvement
• Status: Resolved
• Priority: P2
• Resolution: Fixed
• Fix Version/s: 2.20.0
• Component/s: sdk-py-core, sdk-py-harness
• Assignee: Boyuan Zhang
• Reporter: Boyuan Zhang
• Created: 01/Nov/19 00:26
• Updated: 03/Aug/20 16:43
• Resolved: 25/Feb/20 19:13

Description

This is a follow up for in-progress PR: https://github.com/apache/beam/pull/9794.
Current implementation in PR9794 provides a default implementation of WatermarkEstimator. For further work, we want to let WatermarkEstimator to be a pure Interface. We'll provide a WatermarkEstimatorProvider to be able to create a custom WatermarkEstimator per windowed value. It should be similar to how we track restriction for SDF:
WatermarkEstimator <---> RestrictionTracker
WatermarkEstimatorProvider <---> RestrictionTrackerProvider
WatermarkEstimatorParam <---> RestrictionDoFnParam

Issue Links

• links to: GitHub Pull Request #10375
• links to: GitHub Pull Request #10802
• links to: GitHub Pull Request #10933
• links to: GitHub Pull Request #10957