Represent SDM Counters as Gauges In Prometheus Exposition Format (#4101)

Co-authored-by: kkeirstead <[email protected]>
dotnet · Mar 30, 2023 · a681b6c · a681b6c
1 parent 5a997db
commit a681b6c
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/src/Microsoft.Diagnostics.Monitoring.WebApi/Metrics/MetricsStore.cs b/src/Microsoft.Diagnostics.Monitoring.WebApi/Metrics/MetricsStore.cs
@@ -200,8 +200,8 @@ private static string GetMetricType(EventType eventType)
         {
             switch (eventType)
             {
+                // In Prometheus, rates are treated as gauges due to their non-monotonic nature
                 case EventType.Rate:
-                    return "counter";
                 case EventType.Gauge:
                     return "gauge";
                 case EventType.Histogram:

diff --git a/src/Tests/Microsoft.Diagnostics.Monitoring.Tool.UnitTests/MetricsFormattingTests.cs b/src/Tests/Microsoft.Diagnostics.Monitoring.Tool.UnitTests/MetricsFormattingTests.cs
@@ -99,7 +99,7 @@ public async Task CounterFormat_Test()
 
             Assert.Equal(3, lines.Count);
             Assert.Equal($"# HELP {metricName}{payload.Unit} {payload.DisplayName}", lines[0]);
-            Assert.Equal($"# TYPE {metricName} counter", lines[1]);
+            Assert.Equal($"# TYPE {metricName} gauge", lines[1]);
             Assert.Equal($"{metricName} {payload.Value} {new DateTimeOffset(payload.Timestamp).ToUnixTimeMilliseconds()}", lines[2]);
         }