[Iceberg CDC] Add watch for snapshots source#38834
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Summary of ChangesHello, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request implements a snapshot-watching mechanism for Iceberg CDC in Apache Beam. By periodically polling for new snapshots and tracking them using monotonic sequence numbers, the system can effectively stream changes from an Iceberg table. It includes robust handling for watermark advancement during idle periods and provides comprehensive unit testing for the new SDF logic. Highlights
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Code Review
This pull request introduces WatchForSnapshotsSdf, a SplittableDoFn that monitors Iceberg tables for new snapshots, alongside necessary visibility and configuration updates in IcebergScanConfig, ReadUtils, and TableCache. The review feedback identifies several critical issues: a potential NullPointerException in ReadUtils when resolving expired snapshots, stale metadata returns in TableCache due to asynchronous cache refreshing, incorrect range estimation and stale cache usage in WatchForSnapshotsSdf, and a missing validation check to enforce Iceberg table format version 2 or higher for CDC scans.
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## master #38834 +/- ##
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Coverage 57.73% 57.73%
- Complexity 13049 13052 +3
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Files 2513 2513
Lines 261615 261618 +3
Branches 10745 10746 +1
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+ Hits 151035 151048 +13
+ Misses 104846 104837 -9
+ Partials 5734 5733 -1
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Reminder, please take a look at this pr: @chamikaramj |
| if (fromSnapshot != null) { | ||
| fromSnapshot = table.snapshot(fromSnapshot).parentId(); | ||
| Snapshot snapshot = table.snapshot(fromSnapshot); | ||
| fromSnapshot = snapshot != null ? snapshot.parentId() : null; |
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What happen if A user's from_snapshot is expired by table maintenance before a pipeline restart IncrementalScanSource ? I believe the existing WatchForSnapshots silently reprocess the entire table history, it will emit mass duplicates with no warning.
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This PR's watch transform keeps track of the snapshot sequence number (stateful), so on restart it should skip everything up to the last processed snapshot
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Will merge when tests go green |
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IcebergIO Unit Test failures are irrelevant (see #39266) |
2 participants
Adds a source that periodically polls for snapshots and outputs the snapshot ID. Tracks progress based on snapshot sequence number, which is monotonically increasing unlike the ID.
Part of #38831
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