Add support for monotonic sums, add more tests

open-telemetry · Oct 29, 2024 · b412857 · b412857
1 parent 218c71a
commit b412857
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Showing 2 changed files with 323 additions and 46 deletions.
diff --git a/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs b/src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusSerializerExt.cs
@@ -1,6 +1,7 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+using System.Diagnostics;
 using OpenTelemetry.Metrics;
 
 namespace OpenTelemetry.Exporter.Prometheus;
@@ -28,8 +29,11 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
         cursor = WriteUnitMetadata(buffer, cursor, prometheusMetric, openMetricsRequested);
         cursor = WriteHelpMetadata(buffer, cursor, prometheusMetric, metric.Description, openMetricsRequested);
 
+        var isLong = metric.MetricType.IsLong();
         if (!metric.MetricType.IsHistogram())
         {
+            var isSum = metric.MetricType.IsSum();
+
             foreach (ref readonly var metricPoint in metric.GetMetricPoints())
             {
                 var timestamp = metricPoint.EndTime.ToUnixTimeMilliseconds();
@@ -40,12 +44,9 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
 
                 buffer[cursor++] = unchecked((byte)' ');
 
-                // TODO: MetricType is same for all MetricPoints
-                // within a given Metric, so this check can avoided
-                // for each MetricPoint
-                if (((int)metric.MetricType & 0b_0000_1111) == 0x0a /* I8 */)
+                if (isLong)
                 {
-                    if (metric.MetricType.IsSum())
+                    if (isSum)
                     {
                         cursor = WriteLong(buffer, cursor, metricPoint.GetSumLong());
                     }
@@ -56,7 +57,7 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                 }
                 else
                 {
-                    if (metric.MetricType.IsSum())
+                    if (isSum)
                     {
                         cursor = WriteDouble(buffer, cursor, metricPoint.GetSumDouble());
                     }
@@ -70,11 +71,18 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
 
                 cursor = WriteTimestamp(buffer, cursor, timestamp, openMetricsRequested);
 
+                if (isSum && metricPoint.TryGetExemplars(out var exemplarCollection))
+                {
+                    cursor = WriteSumExemplar(buffer, cursor, metric, openMetricsRequested, exemplarCollection);
+                }
+
                 buffer[cursor++] = ASCII_LINEFEED;
             }
         }
         else
         {
+            Debug.Assert(!isLong, "Expected histogram metric to be of type `double`");
+
             foreach (ref readonly var metricPoint in metric.GetMetricPoints())
             {
                 var tags = metricPoint.Tags;
@@ -115,7 +123,7 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
                     {
                         if (exemplars.Current.DoubleValue <= histogramMeasurement.ExplicitBound)
                         {
-                            cursor = WriteExemplar(buffer, cursor, exemplars.Current, openMetricsRequested, metric.Name);
+                            cursor = WriteExemplar(buffer, cursor, exemplars.Current, openMetricsRequested, metric.Name, isLong: false);
                         }
 
                         while (hasExemplar && exemplars.Current.DoubleValue <= histogramMeasurement.ExplicitBound)
@@ -160,7 +168,44 @@ public static int WriteMetric(byte[] buffer, int cursor, Metric metric, Promethe
         return cursor;
     }
 
-    private static int WriteExemplar(byte[] buffer, int cursor, in Exemplar exemplar, bool openMetricsRequested, string metricName)
+    private static int WriteSumExemplar(
+        byte[] buffer,
+        int cursor,
+        in Metric metric,
+        bool openMetricsRequested,
+        in ReadOnlyExemplarCollection exemplarCollection)
+    {
+        var exemplars = exemplarCollection.GetEnumerator();
+        if (!exemplars.MoveNext())
+        {
+            return cursor;
+        }
+
+        ref readonly Exemplar maxExemplar = ref exemplars.Current;
+        var isLong = metric.MetricType.IsLong();
+
+        while (exemplars.MoveNext())
+        {
+            if (isLong)
+            {
+                if (exemplars.Current.LongValue >= maxExemplar.LongValue)
+                {
+                    maxExemplar = ref exemplars.Current;
+                }
+            }
+            else
+            {
+                if (exemplars.Current.DoubleValue >= maxExemplar.DoubleValue)
+                {
+                    maxExemplar = ref exemplars.Current;
+                }
+            }
+        }
+
+        return WriteExemplar(buffer, cursor, maxExemplar, openMetricsRequested, metric.Name, isLong);
+    }
+
+    private static int WriteExemplar(byte[] buffer, int cursor, in Exemplar exemplar, bool openMetricsRequested, string metricName, bool isLong)
     {
         buffer[cursor++] = unchecked((byte)' ');
         buffer[cursor++] = unchecked((byte)'#');
@@ -204,7 +249,15 @@ private static int WriteExemplar(byte[] buffer, int cursor, in Exemplar exemplar
         buffer[cursor - 1] = unchecked((byte)'}'); // Note: We write the '}' over the last written comma, which is extra.
         buffer[cursor++] = unchecked((byte)' ');
 
-        cursor = WriteDouble(buffer, cursor, exemplar.DoubleValue);
+        if (isLong)
+        {
+            cursor = WriteLong(buffer, cursor, exemplar.LongValue);
+        }
+        else
+        {
+            cursor = WriteDouble(buffer, cursor, exemplar.DoubleValue);
+        }
+
         buffer[cursor++] = unchecked((byte)' ');
         cursor = WriteTimestamp(buffer, cursor, exemplar.Timestamp.ToUnixTimeMilliseconds(), openMetricsRequested);