From 8500472c41622ec6aa3415d8e5ff892c9c9d023e Mon Sep 17 00:00:00 2001
From: kkeirstead <85592574+kkeirstead@users.noreply.github.com>
Date: Thu, 30 Mar 2023 09:17:50 -0700
Subject: [PATCH] Represent SDM Counters as Gauges In Prometheus Exposition
 Format (#4098)

---
 .../Metrics/MetricsStore.cs                                     | 2 +-
 .../MetricsFormattingTests.cs                                   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Microsoft.Diagnostics.Monitoring.WebApi/Metrics/MetricsStore.cs b/src/Microsoft.Diagnostics.Monitoring.WebApi/Metrics/MetricsStore.cs
index 1ebfdbef892..5d3b01425cd 100644
--- 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
index 22fa08055e2..ae4712896c1 100644
--- 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]);
         }