FrankChen021 commented on code in PR #20291:
URL: https://github.com/apache/druid/pull/20291#discussion_r4034902768
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server/src/main/java/org/apache/druid/segment/metadata/AbstractSegmentMetadataCache.java:
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@@ -615,6 +616,9 @@ public void removeSegment(final DataSegment segment)
}
}
);
+ if (remainingSegments == null) {
+ dataSourcesNeedingRebuild.remove(segment.getDataSource());
Review Comment:
Addressed in 64694425a9. Rather than coordinating with the in-flight
refresh, the metric emission is now idempotent: both `removeSegment` and the
null-signature branch of `refresh` emit `dataSource/removed` only when their
own `tables.remove(dataSource)` returned a non-null value. Since `tables` is a
`ConcurrentHashMap`, exactly one of the two paths wins the remove and emits;
the other sees `null` and stays silent, in either interleaving. The callback
still never touches the refresh thread's local `dataSourcesToRebuild` set, and
no lock is held across metadata queries.
Test coverage: `testLastSegmentRemovalClearsRebuildState` now also runs a
refresh that is handed the datasource explicitly after the last segment is gone
(simulating a refresh that captured it before the removal) and asserts the
metric count stays at 1. A new
`testRefreshOfUnknownDatasourceDoesNotEmitRemovalMetric` covers a datasource
that never had a table. Both fail on the previous revision (`expected: <1> but
was: <2>` / `expected: <0> but was: <1>`) and pass now.
The separate table-resurrection race (refresh re-inserting a table after the
last segment was removed) is pre-existing on master and not addressed here; I
will file it as a follow-up.
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