FrankChen021 commented on code in PR #19655:
URL: https://github.com/apache/druid/pull/19655#discussion_r3570770878
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indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/supervisor/autoscaler/CostBasedAutoScaler.java:
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@@ -207,6 +207,25 @@ public CostBasedAutoScalerConfig getConfig()
return config;
}
+ private boolean isCriticalLag(CostMetrics metrics)
+ {
+ final Long criticalLagThreshold = config.getCriticalLagThreshold();
+ return metrics != null && criticalLagThreshold != null
+ && metrics.getAggregateLag() >= criticalLagThreshold *
WeightedCostFunction.CRITICAL_LAG_TIER1_FRACTION;
Review Comment:
[P2] Use exact total lag for tier checks
`collectMetrics()` supplies only `lagStats.getAvgLag()`, while
`CostMetrics#getAggregateLag()` reconstructs the total as `avgLag *
partitionCount`. `DefaultLagAggregator` computes that average using integer
division, so the reconstructed value can undercount by up to `partitionCount -
1`; for example, total lag 999 across 1000 partitions becomes aggregate lag 0.
A valid `criticalLagThreshold` may therefore be crossed without engaging tier 1
or tier 2. With the updated normal multiplier set to 0, a missed tier also
leaves lag unamplified and scale-up boundaries enabled. Carry
`lagStats.getTotalLag()` into `CostMetrics` and use the exact total for these
comparisons.
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