Fly-Style commented on code in PR #19646:
URL: https://github.com/apache/druid/pull/19646#discussion_r3505649635
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indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/supervisor/autoscaler/WeightedCostFunction.java:
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@@ -53,27 +53,28 @@ public class WeightedCostFunction
/**
* Minimum rate of processing for any task in records per second. This is
used
* as a placeholder if avg rate is not available to ensure that cost
computations
- * do not return infinitely large lag recovery times.
+ * do not return infinitely large lag recovery times, at the expense of
underestimating the lag cost.
*/
- static final double MIN_PROCESSING_RATE = 1_000;
+ static final double MIN_PROCESSING_RATE = 5_000;
/**
- * Target idle ratio representing the optimal operating point for the
U-shaped idle cost.
+ * Default target idle ratio representing the optimal operating point for
the U-shaped idle cost.
* At this ratio the idle cost is at its minimum; both lower (risk) and
higher (waste) are penalized.
+ * Configurable via {@link CostBasedAutoScalerConfig#getIdealIdleRatio()}.
*/
static final double IDEAL_IDLE_RATIO = 0.25;
/**
* Penalty magnitude applied when idle ratio is 0 (no safety margin).
* Controls the steepness of the U-shape on the under-provisioning side.
*/
- static final double UNDER_PROVISIONING_PENALTY = 2.0;
+ static final double UNDER_PROVISIONING_PENALTY = 1.0;
/**
* Penalty magnitude applied when idle ratio is 1 (fully wasted capacity).
* Controls the steepness of the U-shape on the over-provisioning side.
*/
- static final double OVER_PROVISIONING_PENALTY = 1.0;
+ static final double OVER_PROVISIONING_PENALTY = 2.5;
Review Comment:
I tried 2.0, but 2.5 looked better in simulation.
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