Fly-Style commented on code in PR #19562:
URL: https://github.com/apache/druid/pull/19562#discussion_r3467865157
##########
indexing-service/src/main/java/org/apache/druid/indexing/seekablestream/supervisor/autoscaler/WeightedCostFunction.java:
##########
@@ -42,6 +42,12 @@ public class WeightedCostFunction
*/
static final double LAG_AMPLIFICATION_MULTIPLIER = 0.4;
+ /**
+ * Exponent (< 1) for sublinear busy redistribution in the idle
projection: busy grows as
+ * {@code (currentTaskCount / proposedTaskCount)^EXPONENT}, not linearly.
Calibrated as log2(1.25) ~= 0.32.
+ */
+ static final double IDLE_SUBLINEARITY_EXPONENT = 0.32;
Review Comment:
> Why this specific value?
This is already explained in PR description: we want to redistribute
projected busyness in a sub-linear way, basically making it U-shaped (instead
of V-shaped, like it was previously). It is also proved by theoretical math
behind it (see plots).
Regarding an alternative -- I'd encourage you to elaborate more, please.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
