apache/beam

Improve UnboundedSourceShard structure

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#18,122 opened on Jun 3, 2022

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Description

Use the 'OneOf' of "Active Reader" and "Optional<Checkpoint>", to make it obvious how to obtain and use a reader.

Maintain an ordered list of checkpoints that have not been finalized for a shard. Checkpoints that can be resumed from can also be finalized, but otherwise the two are unrelated. This also improves ease of never multi-finalizing a checkpoint. This gets more complicated with retries, but must be considered with the associated work required to make UnboundedReadEvaluatorFactory handle retries properly.

Imported from Jira BEAM-1659. Original Jira may contain additional context. Reported by: tgroh.

Contributor guide

Research direction
Study the current UnboundedSourceShard implementation, understand the OneOf pattern used for active reader and checkpoint, and design a structure to maintain an ordered list of non finalized checkpoints while ensuring no multi finalization. Consider retry handling in UnboundedReadEvaluatorFactory.
Tech stack
java
Domain
backend
Issue type
Refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Needs investigation
Prerequisites
JavaApache Beam source concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35