loadbalancer-experimental: Narrow ewma config params from long to int #2994
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Motivation: We currently allow configuring a long for the parameter values that affect the RequestTracker ewma, specifically the cancel, error, and concurrent request penalties. There are no realistic scenarios where a long is necessary vs an int. Modifications: Change the configuration parameters to an int.
...adbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultRequestTracker.java
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...adbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultRequestTracker.java
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...adbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/DefaultRequestTracker.java
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| // Add penalty for concurrent requests to account for "unaccounted" load. | ||
| // Penalty is the observed latency if known, else an arbitrarily high value which makes entities for which | ||
| // no latency data has yet been received (eg: request sent but not received), un-selectable. | ||
| final int concurrentPenalty = (int) min(MAX_VALUE, | ||
| (long) concurrentCount * concurrentRequestPenalty * currentEWMA); | ||
| int concurrentPenalty = safeMultiply(concurrentCount, safeMultiply(currentEWMA, concurrentRequestPenalty)); |
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Side note: when I was looking at how EWMA is calculated in updateEWMA, it feels like if we move this part into a separate static method, it will get a higher chance for inlining:
final double tmp = (currentTimeNanos - lastTimeNanos) * invTau;
final double w = exp(-tmp);
nextEWMA = (int) ceil(currentEWMA * w + currentLatency * (1d - w));WDYT?
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I'm not strongly opinionated one way or the other, so I included it in the latest commit.
idelpivnitskiy
approved these changes
Jul 3, 2024
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Motivation:
We currently allow configuring a long for the parameter values that affect the RequestTracker ewma, specifically the cancel, error, and concurrent request penalties. There are no realistic scenarios where a long is necessary vs an int.
Modifications:
Change the configuration parameters to an int.