From a5380165935752573b9a5ccc39eef99e91ce815c Mon Sep 17 00:00:00 2001
From: Cijo Thomas <cithomas@microsoft.com>
Date: Mon, 20 Sep 2021 21:52:11 -0700
Subject: [PATCH] Disallow multiple metric streams of same name. (#2392)

---
 src/OpenTelemetry/Metrics/MeterProviderSdk.cs | 32 +++++++++++++------
 .../Metrics/MetricAPITest.cs                  | 10 +++---
 2 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/src/OpenTelemetry/Metrics/MeterProviderSdk.cs b/src/OpenTelemetry/Metrics/MeterProviderSdk.cs
index af142db482c..88957422a64 100644
--- a/src/OpenTelemetry/Metrics/MeterProviderSdk.cs
+++ b/src/OpenTelemetry/Metrics/MeterProviderSdk.cs
@@ -31,6 +31,8 @@ internal sealed class MeterProviderSdk : MeterProvider
         private readonly Metric[] metrics;
         private readonly List<object> instrumentations = new List<object>();
         private readonly object collectLock = new object();
+        private readonly object instrumentCreationLock = new object();
+        private readonly Dictionary<string, bool> metricStreamNames = new Dictionary<string, bool>(StringComparer.OrdinalIgnoreCase);
         private readonly MeterListener listener;
         private readonly MetricReader reader;
         private int metricIndex = -1;
@@ -94,16 +96,26 @@ internal MeterProviderSdk(
                 {
                     if (meterSourcesToSubscribe.ContainsKey(instrument.Meter.Name))
                     {
-                        var index = Interlocked.Increment(ref this.metricIndex);
-                        if (index >= MaxMetrics)
+                        lock (this.instrumentCreationLock)
                         {
-                            // Log that all measurements are dropped from this instrument.
-                        }
-                        else
-                        {
-                            var metric = new Metric(instrument, temporality);
-                            this.metrics[index] = metric;
-                            listener.EnableMeasurementEvents(instrument, metric);
+                            if (this.metricStreamNames.ContainsKey(instrument.Name))
+                            {
+                                // log and ignore this instrument.
+                                return;
+                            }
+
+                            var index = Interlocked.Increment(ref this.metricIndex);
+                            if (index >= MaxMetrics)
+                            {
+                                // Log that all measurements are dropped from this instrument.
+                            }
+                            else
+                            {
+                                var metric = new Metric(instrument, temporality);
+                                this.metrics[index] = metric;
+                                this.metricStreamNames.Add(instrument.Name, true);
+                                listener.EnableMeasurementEvents(instrument, metric);
+                            }
                         }
                     }
                 },
@@ -173,7 +185,7 @@ internal Batch<Metric> Collect()
                         this.metrics[i].SnapShot();
                     }
 
-                    return (target > 0) ? new Batch<Metric>(this.metrics, indexSnapShot + 1) : default;
+                    return (target > 0) ? new Batch<Metric>(this.metrics, target) : default;
                 }
                 catch (Exception)
                 {
diff --git a/test/OpenTelemetry.Tests/Metrics/MetricAPITest.cs b/test/OpenTelemetry.Tests/Metrics/MetricAPITest.cs
index e87346bc38e..668a6aa1328 100644
--- a/test/OpenTelemetry.Tests/Metrics/MetricAPITest.cs
+++ b/test/OpenTelemetry.Tests/Metrics/MetricAPITest.cs
@@ -59,7 +59,7 @@ void ProcessExport(Batch<Metric> batch)
                 PreferredAggregationTemporality = exportDelta ? AggregationTemporality.Delta : AggregationTemporality.Cumulative,
             };
 
-            var meter = new Meter("TestMeter");
+            using var meter = new Meter("TestMeter");
             var counterLong = meter.CreateCounter<long>("mycounter");
             using var meterProvider = Sdk.CreateMeterProviderBuilder()
                 .AddSource("TestMeter")
@@ -135,7 +135,7 @@ void ProcessExport(Batch<Metric> batch)
                 PreferredAggregationTemporality = exportDelta ? AggregationTemporality.Delta : AggregationTemporality.Cumulative,
             };
 
-            var meter = new Meter(meterName);
+            using var meter = new Meter(meterName);
             int i = 1;
             var counterLong = meter.CreateObservableCounter<long>(
             "observable-counter",
@@ -204,7 +204,7 @@ void ProcessExport(Batch<Metric> batch)
             {
                 PreferredAggregationTemporality = temporality,
             };
-            var meter = new Meter("TestPointCapMeter");
+            using var meter = new Meter("TestPointCapMeter");
             var counterLong = meter.CreateCounter<long>("mycounterCapTest");
             using var meterProvider = Sdk.CreateMeterProviderBuilder()
                 .AddSource("TestPointCapMeter")
@@ -256,7 +256,7 @@ void ProcessExport(Batch<Metric> batch)
                 PreferredAggregationTemporality = AggregationTemporality.Cumulative,
             };
 
-            var meter = new Meter("TestLongCounterMeter");
+            using var meter = new Meter("TestLongCounterMeter");
             var counterLong = meter.CreateCounter<long>("mycounter");
             using var meterProvider = Sdk.CreateMeterProviderBuilder()
                 .AddSource("TestLongCounterMeter")
@@ -326,7 +326,7 @@ void ProcessExport(Batch<Metric> batch)
                 PreferredAggregationTemporality = AggregationTemporality.Cumulative,
             };
 
-            var meter = new Meter("TestDoubleCounterMeter");
+            using var meter = new Meter("TestDoubleCounterMeter");
             var counterDouble = meter.CreateCounter<double>("mycounter");
             using var meterProvider = Sdk.CreateMeterProviderBuilder()
                 .AddSource("TestDoubleCounterMeter")