junrao commented on code in PR #15889:
URL: https://github.com/apache/kafka/pull/15889#discussion_r1611984550
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clients/src/main/java/org/apache/kafka/common/metrics/stats/SampledStat.java:
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@@ -106,44 +109,51 @@ public String toString() {
public abstract double combine(List<Sample> samples, MetricConfig config,
long now);
- /* Timeout any windows that have expired in the absence of any events */
+ // purge any samples that lack observed events within the monitored window
protected void purgeObsoleteSamples(MetricConfig config, long now) {
long expireAge = config.samples() * config.timeWindowMs();
for (Sample sample : samples) {
- if (now - sample.lastWindowMs >= expireAge)
+ // samples overlapping the monitored window are kept,
+ // even if they started before it
+ if (now - sample.lastEventMs >= expireAge) {
sample.reset(now);
+ }
}
}
protected static class Sample {
public double initialValue;
public long eventCount;
- public long lastWindowMs;
+ public long startTimeMs;
+ public long lastEventMs;
public double value;
public Sample(double initialValue, long now) {
this.initialValue = initialValue;
this.eventCount = 0;
- this.lastWindowMs = now;
+ this.startTimeMs = now;
+ this.lastEventMs = now;
this.value = initialValue;
}
public void reset(long now) {
this.eventCount = 0;
- this.lastWindowMs = now;
+ this.startTimeMs = now;
+ this.lastEventMs = now;
this.value = initialValue;
}
public boolean isComplete(long timeMs, MetricConfig config) {
- return timeMs - lastWindowMs >= config.timeWindowMs() ||
eventCount >= config.eventWindow();
+ return timeMs - startTimeMs >= config.timeWindowMs() || eventCount
>= config.eventWindow();
Review Comment:
Yes, when the oldest window overlaps with the monitored window, the old
approach ignores it and the current approach keeps it. Either one could be
considered correct.
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