dcapwell commented on code in PR #4549:
URL: https://github.com/apache/cassandra/pull/4549#discussion_r2674061499
##########
src/java/org/apache/cassandra/service/TimeoutStrategy.java:
##########
@@ -97,7 +97,8 @@ interface LatencyModifierFactory
default LatencyModifier identity() { return (l, a) -> l; }
default LatencyModifier multiply(double constant) { return (l, a) ->
saturatedCast(l * constant); }
default LatencyModifier multiplyByAttempts(double multiply) { return
(l, a) -> saturatedCast(l * multiply * a); }
- default LatencyModifier multiplyByAttemptsExp(double base) { return
(l, a) -> saturatedCast(l * pow(base, a)); }
+ // Ensure attempts is non-negative before subtracting 1.
+ default LatencyModifier multiplyByAttemptsExp(double base) { return
(l, a) -> saturatedCast(l * pow(base, max(0, (max(a, 0) - 1)))); }
Review Comment:
this looks safe
```
$ rg '\^attempts' src
src/java/org/apache/cassandra/config/RetrySpec.java
164: return RetryStrategy.parse(spec.baseSleepTime.toMilliseconds() +
"ms * 2^attempts <= " + spec.maxSleepTime.toMilliseconds() + "ms,retries=" +
(spec.maxAttempts.value - 1), LatencySourceFactory.none());
src/java/org/apache/cassandra/service/RetryStrategy.java
72: * <li> {@code 10ms <= p95(rw)*1.8^attempts <= 100ms}
src/java/org/apache/cassandra/service/TimeoutStrategy.java
73: * <li> {@code 10ms <= p95(rw)*1.8^attempts <= 100ms}
```
The only user is repair, so not really a breaking change to paxos. If
anyone was using this in paxos v2, the only impact is that it would have the
first retry respect the min value rather than do `min * 2`, so LGTM
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