[otlp] Remove Grpc.Core support for .NET Framework and .NET Standard 2.0 in OTLP exporter

Directory.Packages.props

@@ -62,10 +62,6 @@
         We use conservative versions of these packages where an upgrade might
         introduce breaking changes.
     -->
-    <PackageVersion Include="Google.Protobuf" Version="[3.22.5,4.0)" />
-    <PackageVersion Include="Grpc" Version="[2.44.0,3.0)" />
-    <PackageVersion Include="Grpc.Core" Version="[2.44.0,3.0)" />
-    <PackageVersion Include="Grpc.Net.Client" Version="[2.52.0,3.0)" />
   </ItemGroup>
 
   <ItemGroup>
@@ -97,6 +93,9 @@
     <PackageVersion Include="Grpc.AspNetCore" Version="[2.59.0,3.0)" />
     <PackageVersion Include="Grpc.AspNetCore.Server" Version="[2.59.0, 3.0)" />
     <PackageVersion Include="Grpc.Tools" Version="[2.59.0,3.0)" />
+    <PackageVersion Include="Google.Protobuf" Version="[3.22.5,4.0)" />
+    <PackageVersion Include="Grpc" Version="[2.44.0,3.0)" />
+    <PackageVersion Include="Grpc.Net.Client" Version="[2.52.0,3.0)" />
     <PackageVersion Include="Microsoft.CSharp" Version="[4.7.0]" />
     <PackageVersion Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" Version="[3.11.0-beta1.23525.2]" />
     <PackageVersion Include="Microsoft.Coyote" Version="1.7.11" />

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -7,6 +7,24 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+* **Breaking Change (Behavioral)**: Removed the deprecated `Grpc.Core` transport
+  support for `.NET Framework (net462)` and `.NET Standard 2.0` in the OTLP
+  exporter. `OtlpExportProtocol.Grpc` is no longer supported when using the
+  default HTTP client factory on these platforms. Attempting to use this
+  combination will now result in a `NotSupportedException`.
+  ([#](https://github.com/open-telemetry/opentelemetry-dotnet/pull/))
+
+* Changed default export protocol for `.NET Framework` and `.NET Standard 2.0`
+  to `OtlpExportProtocol.HttpProtobuf`. This aligns with supported and actively
+  maintained transport mechanisms.For `.NET Framework` or `.NET Standard 2.0`
+  users previously relying on `OtlpExportProtocol.Grpc`, update your
+  configuration:
+  ([#](https://github.com/open-telemetry/opentelemetry-dotnet/pull/))
+
+  ```csharp
+  options.Protocol = OtlpExportProtocol.HttpProtobuf;
+  ```
+
 ## 1.11.2
 
 Released 2025-Mar-04

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OpenTelemetry.Exporter.OpenTelemetryProtocol.csproj

@@ -23,10 +23,6 @@
     <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry\OpenTelemetry.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Grpc.Core" Condition="'$(TargetFramework)' == 'netstandard2.0' OR '$(TargetFramework)' == '$(NetFrameworkMinimumSupportedVersion)'" />
-  </ItemGroup>
-
   <ItemGroup>
     <Reference Include="System.Net.Http" Condition="'$(TargetFramework)' == '$(NetFrameworkMinimumSupportedVersion)'" />
   </ItemGroup>

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs

@@ -26,7 +26,11 @@ public class OtlpExporterOptions : IOtlpExporterOptions
 {
     internal const string DefaultGrpcEndpoint = "http://localhost:4317";
     internal const string DefaultHttpEndpoint = "http://localhost:4318";
+#if NET462_OR_GREATER || NETSTANDARD2_0
+    internal const OtlpExportProtocol DefaultOtlpExportProtocol = OtlpExportProtocol.HttpProtobuf;
+#else
     internal const OtlpExportProtocol DefaultOtlpExportProtocol = OtlpExportProtocol.Grpc;
+#endif
 
     internal static readonly KeyValuePair<string, string>[] StandardHeaders = new KeyValuePair<string, string>[]
     {

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptionsExtensions.cs

@@ -9,9 +9,6 @@
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation.ExportClient;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation.Transmission;
-#if NET462_OR_GREATER || NETSTANDARD2_0
-using Grpc.Core;
-#endif
 
 namespace OpenTelemetry.Exporter;
 
@@ -25,30 +22,6 @@ internal static class OtlpExporterOptionsExtensions
     private const string MetricsHttpServicePath = "v1/metrics";
     private const string LogsHttpServicePath = "v1/logs";
 
-#if NET462_OR_GREATER || NETSTANDARD2_0
-    public static Channel CreateChannel(this OtlpExporterOptions options)
-    {
-        if (options.Endpoint.Scheme != Uri.UriSchemeHttp && options.Endpoint.Scheme != Uri.UriSchemeHttps)
-        {
-            throw new NotSupportedException($"Endpoint URI scheme ({options.Endpoint.Scheme}) is not supported. Currently only \"http\" and \"https\" are supported.");
-        }
-
-        ChannelCredentials channelCredentials;
-        if (options.Endpoint.Scheme == Uri.UriSchemeHttps)
-        {
-            channelCredentials = new SslCredentials();
-        }
-        else
-        {
-            channelCredentials = ChannelCredentials.Insecure;
-        }
-
-        return new Channel(options.Endpoint.Authority, channelCredentials);
-    }
-
-    public static Metadata GetMetadataFromHeaders(this OtlpExporterOptions options) => options.GetHeaders<Metadata>((m, k, v) => m.Add(k, v));
-#endif
-
     public static THeaders GetHeaders<THeaders>(this OtlpExporterOptions options, Action<THeaders, string, string> addHeader)
         where THeaders : new()
     {
@@ -134,20 +107,6 @@ public static IExportClient GetExportClient(this OtlpExporterOptions options, Ot
             throw new NotSupportedException($"Protocol {options.Protocol} is not supported.");
         }
 
-#if NET462_OR_GREATER || NETSTANDARD2_0
-        if (options.Protocol == OtlpExportProtocol.Grpc)
-        {
-            var servicePath = otlpSignalType switch
-            {
-                OtlpSignalType.Traces => TraceGrpcServicePath,
-                OtlpSignalType.Metrics => MetricsGrpcServicePath,
-                OtlpSignalType.Logs => LogsGrpcServicePath,
-                _ => throw new NotSupportedException($"OtlpSignalType {otlpSignalType} is not supported."),
-            };
-            return new GrpcExportClient(options, servicePath);
-        }
-#endif
-
         return otlpSignalType switch
         {
             OtlpSignalType.Traces => options.Protocol == OtlpExportProtocol.Grpc

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpLogExporterHelperExtensions.cs

@@ -284,6 +284,15 @@ internal static BaseProcessor<LogRecord> BuildOtlpLogExporter(
         Debug.Assert(sdkLimitOptions != null, "sdkLimitOptions was null");
         Debug.Assert(experimentalOptions != null, "experimentalOptions was null");
 
+#if NET462_OR_GREATER || NETSTANDARD2_0
+        if (exporterOptions!.Protocol == OtlpExportProtocol.Grpc &&
+            ReferenceEquals(exporterOptions.HttpClientFactory, exporterOptions.DefaultHttpClientFactory))
+        {
+            throw new NotSupportedException("OtlpExportProtocol.Grpc with the default HTTP client factory is not supported on .NET Framework or .NET Standard 2.0." +
+                "Please switch to OtlpExportProtocol.HttpProtobuf or provide a custom HttpClientFactory.");
+        }
+#endif
+
         if (!skipUseOtlpExporterRegistrationCheck)
         {
             serviceProvider!.EnsureNoUseOtlpExporterRegistrations();

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpMetricExporterExtensions.cs

@@ -168,6 +168,15 @@ internal static MetricReader BuildOtlpExporterMetricReader(
         Debug.Assert(metricReaderOptions != null, "metricReaderOptions was null");
         Debug.Assert(experimentalOptions != null, "experimentalOptions was null");
 
+#if NET462_OR_GREATER || NETSTANDARD2_0
+        if (exporterOptions!.Protocol == OtlpExportProtocol.Grpc &&
+            ReferenceEquals(exporterOptions.HttpClientFactory, exporterOptions.DefaultHttpClientFactory))
+        {
+            throw new NotSupportedException("OtlpExportProtocol.Grpc with the default HTTP client factory is not supported on .NET Framework or .NET Standard 2.0." +
+                "Please switch to OtlpExportProtocol.HttpProtobuf or provide a custom HttpClientFactory.");
+        }
+#endif
+
         if (!skipUseOtlpExporterRegistrationCheck)
         {
             serviceProvider!.EnsureNoUseOtlpExporterRegistrations();

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpTraceExporterHelperExtensions.cs

@@ -129,6 +129,15 @@ internal static BaseProcessor<Activity> BuildOtlpExporterProcessor(
         Debug.Assert(experimentalOptions != null, "experimentalOptions was null");
         Debug.Assert(batchExportProcessorOptions != null, "batchExportProcessorOptions was null");
 
+#if NET462_OR_GREATER || NETSTANDARD2_0
+        if (exporterOptions!.Protocol == OtlpExportProtocol.Grpc &&
+            ReferenceEquals(exporterOptions.HttpClientFactory, exporterOptions.DefaultHttpClientFactory))
+        {
+            throw new NotSupportedException("OtlpExportProtocol.Grpc with the default HTTP client factory is not supported on .NET Framework or .NET Standard 2.0." +
+                "Please switch to OtlpExportProtocol.HttpProtobuf or provide a custom HttpClientFactory.");
+        }
+#endif
+
         if (!skipUseOtlpExporterRegistrationCheck)
         {
             serviceProvider!.EnsureNoUseOtlpExporterRegistrations();