dosubot[bot] commented on issue #2627:
URL:
https://github.com/apache/incubator-hugegraph/issues/2627#issuecomment-2274816214
<!-- Answer -->
To resolve the issue of histogram metrics values for JRaft returning NaN in
the HStore backend of the Master (Apache Release Version) of your server, you
should ensure that the `HistogramWrapper` class is correctly updating its
snapshot. The current implementation updates the snapshot every 30 seconds,
which might be causing the NaN values if the histogram is not being updated
frequently enough.
Here is the relevant code snippet that shows how the `HistogramWrapper`
class is implemented:
```java
private static class HistogramWrapper {
private final com.codahale.metrics.Histogram histogram;
private Snapshot snapshot;
private long ts = System.currentTimeMillis();
HistogramWrapper(com.codahale.metrics.Histogram histogram) {
this.histogram = histogram;
this.snapshot = this.histogram.getSnapshot();
}
Snapshot getSnapshot() {
if (System.currentTimeMillis() - this.ts > 30_000) {
this.snapshot = this.histogram.getSnapshot();
this.ts = System.currentTimeMillis();
}
return this.snapshot;
}
}
```
To ensure that the histogram metrics are updated correctly, you might want
to reduce the interval for updating the snapshot or ensure that the histogram
is being updated frequently enough. You can adjust the interval by modifying
the condition in the `getSnapshot` method:
```java
Snapshot getSnapshot() {
if (System.currentTimeMillis() - this.ts > 10_000) { // Update every 10
seconds
this.snapshot = this.histogram.getSnapshot();
this.ts = System.currentTimeMillis();
}
return this.snapshot;
}
```
Additionally, ensure that the histogram is being updated with new data
points frequently enough to avoid NaN values. If the histogram is not receiving
new data points, it might result in NaN values when the snapshot is taken
<sup>[[1]](https://github.com/apache/incubator-hugegraph/blob/master/hugegraph-store/hg-store-node/src/main/java/org/apache/hugegraph/store/node/metrics/JRaftMetrics.java)</sup>.
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