wu-sheng commented on code in PR #10449:
URL: https://github.com/apache/skywalking/pull/10449#discussion_r1118332343
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oap-server/server-receiver-plugin/otel-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/receiver/otel/otlp/OpenTelemetryMetricRequestProcessor.java:
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@@ -161,6 +163,54 @@ private static Map<Double, Long> buildBuckets(
return result;
}
+ /**
+ * ExponentialHistogram data points are an alternate representation to the
Histogram data point in OpenTelemetry
+ * metric
format(https://opentelemetry.io/docs/reference/specification/metrics/data-model/#exponentialhistogram).
+ * It uses scale, offset and bucket index to calculate the bound. Firstly,
calculate the base using scale by
+ * formula: base = 2**(2**(-scale)). Then the upperBound of specific
bucket can be calculated by formula:
+ * base**(offset+index+1). Above calculation way is about positive
buckets. For the negative case, we just
+ * map them by their absolute value into the negative range using the same
scale as the positive range. So the
+ * upperBound should be calculated as -base**(offset+index).
+ *
+ * @param positiveOffset corresponding to positive Buckets' offset
in ExponentialHistogramDataPoint
+ * @param positiveBucketCounts corresponding to positive Buckets'
bucket_counts in ExponentialHistogramDataPoint
+ * @param negativeOffset corresponding to negative Buckets' offset
in ExponentialHistogramDataPoint
+ * @param negativeBucketCounts corresponding to negative Buckets'
bucket_counts in ExponentialHistogramDataPoint
+ * @param scale corresponding to scale in
ExponentialHistogramDataPoint
+ * @return The map is a bucket set for histogram, the key is specific
bucket's upperBound, the value is item count
+ * in this bucket lower than or equals to key(upperBound)
+ */
+ private static Map<Double, Long> buildBucketsFromExponentialHistogram(
+ int positiveOffset, final List<Long> positiveBucketCounts,
+ int negativeOffset, final List<Long> negativeBucketCounts, int scale) {
+
+ final Map<Double, Long> result = new HashMap<>();
Review Comment:
Check this
https://opentelemetry.io/docs/reference/specification/metrics/data-model/#exponentialhistogram
> The ExponentialHistogram contains a special zero_count bucket and an
optional zero_threshold field where zero_count contains the count of values
whose absolute value is less than or equal to zero_threshold. The precise value
for the zero_threshold is arbitrary and not related to the scale.
So, we can't assume the range of the threshold would not overlap with
existing buckets. We can't build more buckets from it.
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