[hotfix][Metrics] Iterate a locked table-runtime snapshot in gauges - #4326
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[hotfix][Metrics] Iterate a locked table-runtime snapshot in gauges#4326czy006 wants to merge 3 commits into
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…p gauges OptimizerGroupMetrics' five table-count gauges streamed over SchedulingPolicy's live HashMap on scrape threads without tableLock; concurrent addTable/removeTable (table onboarding, group migration) threw ConcurrentModificationException mid-scrape. getTableRuntimeMap() is @VisibleForTesting yet was the production access path. Add tableRuntimesSnapshot() (locked copy, same pattern as tableIdentifiersSnapshot) and point the gauges at it. Churn regression test: with the lock temporarily removed it fails 2 of 3 runs with CME; locked it is stable. Fix record: docs/fix-records/2026-08-16-fix-17-gauge-snapshot-cme.md
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Exercise the registered optimizer-group gauges directly and fail deterministically if they read SchedulingPolicy's live runtime map. This replaces the snapshot-only test that did not cover the production metric path.
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August 28, 2026 07:22
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Brief change log
Make optimizer-group metric gauges iterate a scheduling-policy snapshot instead of the live runtime map. The snapshot is taken under the policy lock, preventing concurrent modification failures while metrics are scraped.
How was this patch tested?
TestSchedulingPolicylocally with JDK 11 before creating this pull request.Documentation