Add Support for HttpSemanticConvention breaking changes.

src/OpenTelemetry.Api/Internal/HttpSemanticConventionHelper.cs

@@ -0,0 +1,67 @@
+// <copyright file="HttpSemanticConventionHelper.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+namespace OpenTelemetry.Internal
+{
+    using System;
+
+    /// <summary>
+    /// Helper class for Http Semantic Conventions.
+    /// </summary>
+    /// <remarks>
+    /// Due to a breaking change in the semantic convention, affected instrumentation libraries
+    /// must inspect an environment variable to determine which attributes to emit.
+    /// This is expected to be removed when the instrumentation libraries reach Stable.
+    /// <see href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md"/>.
+    /// </remarks>
+    internal static class HttpSemanticConventionHelper
+    {
+        [Flags]
+        internal enum HttpSemanticConvention
+        {
+            /// <summary>
+            /// Instructs an instrumentation library to emit the old experimental HTTP attributes.
+            /// </summary>
+            Old = 0x1,
+
+            /// <summary>
+            /// Instructs an instrumentation library to emit the new, stable Http attributes.
+            /// </summary>
+            New = 0x2,
+
+            /// <summary>
+            /// Instructs an instrumentation library to emit both the old and new attributes.
+            /// </summary>
+            Dupe = Old | New,
+        }
+
+        public static HttpSemanticConvention GetSemConvOptIn()
+        {
+            var envVarValue = Environment.GetEnvironmentVariable("OTEL_SEMCONV_STABILITY_OPT_IN");
+            return EvaluateValue(envVarValue);
+        }
+
+        internal static HttpSemanticConvention EvaluateValue(string value)
+        {
+            return value?.ToLower() switch
+            {
+                "http" => HttpSemanticConvention.New,
+                "http/dup" => HttpSemanticConvention.Dupe,
+                _ => HttpSemanticConvention.Old,
+            };
+        }
+    }
+}

src/OpenTelemetry.Instrumentation.AspNetCore/Implementation/HttpInListener.cs

@@ -62,13 +62,16 @@ internal class HttpInListener : ListenerHandler
 #endif
         private readonly PropertyFetcher<Exception> stopExceptionFetcher = new("Exception");
         private readonly AspNetCoreInstrumentationOptions options;
+        private readonly HttpSemanticConventionHelper.HttpSemanticConvention httpSemanticConvention;
 
         public HttpInListener(AspNetCoreInstrumentationOptions options)
             : base(DiagnosticSourceName)
         {
             Guard.ThrowIfNull(options);
 
             this.options = options;
+
+            this.httpSemanticConvention = HttpSemanticConventionHelper.GetSemConvOptIn();
         }
 
         public override void OnEventWritten(string name, object payload)

src/OpenTelemetry.Instrumentation.AspNetCore/OpenTelemetry.Instrumentation.AspNetCore.csproj

@@ -14,6 +14,7 @@
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Instrumentation.GrpcNetClient\GrpcTagHelper.cs" Link="Includes\GrpcTagHelper.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Instrumentation.GrpcNetClient\StatusCanonicalCode.cs" Link="Includes\StatusCanonicalCode.cs" />
     <Compile Include="$(RepoRoot)\src\OpenTelemetry.Api\Internal\Guard.cs" Link="Includes\Guard.cs" />
+    <Compile Include="$(RepoRoot)\src\OpenTelemetry.Api\Internal\HttpSemanticConventionHelper.cs" Link="Includes\HttpSemanticConventionHelper.cs" />
   </ItemGroup>
 
   <ItemGroup>

test/OpenTelemetry.Api.Tests/Internal/HttpSemanticConventionHelperTest.cs

@@ -0,0 +1,52 @@
+// <copyright file="HttpSemanticConventionHelperTest.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using Xunit;
+using static OpenTelemetry.Internal.HttpSemanticConventionHelper;
+
+namespace OpenTelemetry.Api.Tests.Internal
+{
+    public class HttpSemanticConventionHelperTest
+    {
+        [Fact]
+        public void VerifyFlags()
+        {
+            var testValue = HttpSemanticConvention.Dupe;
+            Assert.True(testValue.HasFlag(HttpSemanticConvention.Old));
+            Assert.True(testValue.HasFlag(HttpSemanticConvention.New));
+
+            testValue = HttpSemanticConvention.Old;
+            Assert.True(testValue.HasFlag(HttpSemanticConvention.Old));
+            Assert.False(testValue.HasFlag(HttpSemanticConvention.New));
+
+            testValue = HttpSemanticConvention.New;
+            Assert.False(testValue.HasFlag(HttpSemanticConvention.Old));
+            Assert.True(testValue.HasFlag(HttpSemanticConvention.New));
+        }
+
+        [Fact]
+        public void VerifyEvaluate()
+        {
+            Assert.Equal(HttpSemanticConvention.Old, EvaluateValue(null));
+            Assert.Equal(HttpSemanticConvention.Old, EvaluateValue(string.Empty));
+            Assert.Equal(HttpSemanticConvention.Old, EvaluateValue("junk"));
+            Assert.Equal(HttpSemanticConvention.Old, EvaluateValue("none"));
+            Assert.Equal(HttpSemanticConvention.New, EvaluateValue("http"));
+            Assert.Equal(HttpSemanticConvention.New, EvaluateValue("HTTP"));
+            Assert.Equal(HttpSemanticConvention.Dupe, EvaluateValue("http/dup"));
+        }
+    }
+}