FrankChen021 commented on code in PR #19655:
URL: https://github.com/apache/druid/pull/19655#discussion_r3520911069
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indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/supervisor/autoscaler/CostBasedAutoScaler.java:
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@@ -284,6 +321,12 @@ int computeOptimalTaskCount(CostMetrics metrics)
: startIndex;
}
+ // Emergency (tier 2) lag skips the argmin search entirely: evaluate only
the maximum valid task count.
+ if (emergencyLag) {
+ startIndex = validTaskCounts.length - 1;
Review Comment:
[P1] Make emergency lag choose the max unconditionally
The emergency path narrows the loop to only the maximum valid task count,
but `optimalTaskCount` and `optimalCost` are still initialized from the current
task count before this block. If the configured weights make the current-count
cost lower than the max-count cost, for example `lagWeight=0` and
`idleWeight=1`, the loop evaluates the max candidate but never updates
`optimalTaskCount`, so tier-2 emergency lag returns the current count instead
of jumping to the max. Set the emergency result to the max candidate
unconditionally, or initialize the optimal candidate from `startIndex` after
the emergency bounds are applied.
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