Mmuzaf commented on code in PR #3102:
URL: https://github.com/apache/cassandra/pull/3102#discussion_r1714202555
##########
src/java/org/apache/cassandra/metrics/DecayingEstimatedHistogramReservoir.java:
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@@ -371,42 +363,50 @@ private void rescaleIfNeeded(long now)
{
try
{
- rescale(now);
+ decayingBuckets = rescale(now);
Review Comment:
It seems that both `needRescale` and `rescale` should be calculated on the
same object reference. Currently it doesn't look like the same condition is
being met when the `rescale` method is run after checking `needRescale`, or am
I missing something?
The example:
```
private static final
AtomicReferenceFieldUpdater<DecayingEstimatedHistogramReservoir,
DecayingBuckets> decayingBucketsUpdater =
AtomicReferenceFieldUpdater.newUpdater(DecayingEstimatedHistogramReservoir.class,
DecayingBuckets.class, "decayingBuckets");
private void rescaleIfNeeded(long now)
{
DecayingBuckets buckets = decayingBuckets;
while (now - buckets.decayLandmark > LANDMARK_RESET_INTERVAL_IN_NS)
{
double rescaleFactor = buckets.forwardDecayWeight(now);
DecayingBuckets newBuckets = new DecayingBuckets(now);
for (int i = 0; i < buckets.buckets.length(); i++)
newBuckets.buckets.set(i, Math.round(buckets.buckets.get(i) /
rescaleFactor));
boolean success = decayingBucketsUpdater.compareAndSet(this,
buckets, newBuckets);
if (success)
return;
buckets = decayingBuckets;
}
}
```
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