FrankChen021 commented on code in PR #20267:
URL: https://github.com/apache/druid/pull/20267#discussion_r3940653841
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server/src/main/java/org/apache/druid/server/coordinator/loading/StrategicSegmentAssigner.java:
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@@ -516,25 +520,68 @@ private int loadPartialReplicas(
return 0;
}
- // The classifier's list is already the complete candidate set when
nothing was canceled.
+ // The classifier's lists are already the complete candidate sets when
nothing was canceled.
+ final List<ServerHolder> inPlaceDestinations;
final List<ServerHolder> freshCandidates;
if (canceledStaleServers.isEmpty()) {
+ inPlaceDestinations = status.getEligibleForInPlaceReload();
freshCandidates = status.getEligibleForFreshLoad();
} else {
+ inPlaceDestinations = new
ArrayList<>(status.getEligibleForInPlaceReload());
freshCandidates = new ArrayList<>(status.getEligibleForFreshLoad());
- freshCandidates.addAll(canceledStaleServers);
+ for (ServerHolder server : canceledStaleServers) {
+ if (server.isServingSegment(segment) &&
PartialSegmentStatusInTier.canReloadInPlace(server)) {
+ inPlaceDestinations.add(server);
+ } else {
+ freshCandidates.add(server);
+ }
+ }
}
- final Iterator<ServerHolder> destinations = Iterators.concat(
- serversToLoadSegment(segment, tier, freshCandidates),
- status.getEligibleForAdditiveReload().iterator()
+ int numLoadsQueued = queuePartialLoads(
Review Comment:
[P1] Preserve the serving replica when an in-place reload fails
This now queues an in-place reload before trying any empty server, but a
failed `loadPartial` is handled by `SegmentLoadDropHandler.addSegment` as a
failed segment load: it unannounces and drops the existing segment. Failures
are possible here (for example, the old cache entry is held or the new partial
bundles cannot be reserved), and `canReloadInPlace` intentionally does not
check disk capacity. With one stale replica and a viable empty server, this can
remove the only serving copy even though the previous fresh-first path would
have kept it serving while the replacement loaded. Preserve or roll back the
old replica, or fall back to a fresh destination when the in-place load cannot
proceed, and add a failure-with-fresh-candidate test.
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