OTLP exporter add User-Agent header

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* Include User-Agent header
+  [per the specification](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#user-agent).
+  ([#4120](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4120))
+
 ## 1.4.0-rc.2
 
 Released 2023-Jan-09

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptions.cs

@@ -39,11 +39,19 @@ public class OtlpExporterOptions
         internal const string TimeoutEnvVarName = "OTEL_EXPORTER_OTLP_TIMEOUT";
         internal const string ProtocolEnvVarName = "OTEL_EXPORTER_OTLP_PROTOCOL";
 
+        internal static readonly KeyValuePair<string, string>[] StandardHeaders = new KeyValuePair<string, string>[]
+        {
+            new KeyValuePair<string, string>("User-Agent", UserAgentProductVersion != null ? $"{UserAgentProduct}/{UserAgentProductVersion}" : UserAgentProduct),
+        };
+
         internal readonly Func<HttpClient> DefaultHttpClientFactory;
 
         private const string DefaultGrpcEndpoint = "http://localhost:4317";
         private const string DefaultHttpEndpoint = "http://localhost:4318";
         private const OtlpExportProtocol DefaultOtlpExportProtocol = OtlpExportProtocol.Grpc;
+        private const string UserAgentProduct = "OTel-OTLP-Exporter-Dotnet";
+
+        private static readonly Version UserAgentProductVersion = GetAssemblyVersion();
 
         private Uri endpoint;
 
@@ -195,5 +203,18 @@ internal static void RegisterOtlpExporterOptionsFactory(IServiceCollection servi
                     configuration,
                     sp.GetRequiredService<IOptionsMonitor<BatchExportActivityProcessorOptions>>().Get(name)));
         }
+
+        private static Version GetAssemblyVersion()
+        {
+            try
+            {
+                var assemblyName = typeof(OtlpExporterOptions).Assembly.GetName();
+                return assemblyName.Version;
+            }
+            catch (Exception)
+            {
+                return null;
+            }
+        }
     }
 }

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpExporterOptionsExtensions.cs

@@ -89,6 +89,11 @@ public static THeaders GetHeaders<THeaders>(this OtlpExporterOptions options, Ac
                     });
             }
 
+            foreach (var header in OtlpExporterOptions.StandardHeaders)
+            {
+                addHeader(headers, header.Key, header.Value);
+            }
+
             return headers;
         }
 

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/Implementation/ExportClient/OtlpHttpTraceExportClientTests.cs

@@ -63,9 +63,14 @@ public void NewOtlpHttpTraceExportClient_OtlpExporterOptions_ExporterHasCorrectP
 
             Assert.NotNull(client.HttpClient);
 
-            Assert.Equal(2, client.Headers.Count);
+            Assert.Equal(2 + OtlpExporterOptions.StandardHeaders.Length, client.Headers.Count);
             Assert.Contains(client.Headers, kvp => kvp.Key == header1.Name && kvp.Value == header1.Value);
             Assert.Contains(client.Headers, kvp => kvp.Key == header2.Name && kvp.Value == header2.Value);
+
+            for (int i = 0; i < OtlpExporterOptions.StandardHeaders.Length; i++)
+            {
+                Assert.Contains(client.Headers, entry => entry.Key == OtlpExporterOptions.StandardHeaders[i].Key && entry.Value == OtlpExporterOptions.StandardHeaders[i].Value);
+            }
         }
 
         [Theory]
@@ -179,10 +184,15 @@ void RunTest(Batch<Activity> batch)
                 Assert.NotNull(httpRequest);
                 Assert.Equal(HttpMethod.Post, httpRequest.Method);
                 Assert.Equal("http://localhost:4317/", httpRequest.RequestUri.AbsoluteUri);
-                Assert.Equal(2, httpRequest.Headers.Count());
+                Assert.Equal(OtlpExporterOptions.StandardHeaders.Length + 2, httpRequest.Headers.Count());
                 Assert.Contains(httpRequest.Headers, h => h.Key == header1.Name && h.Value.First() == header1.Value);
                 Assert.Contains(httpRequest.Headers, h => h.Key == header2.Name && h.Value.First() == header2.Value);
 
+                for (int i = 0; i < OtlpExporterOptions.StandardHeaders.Length; i++)
+                {
+                    Assert.Contains(httpRequest.Headers, entry => entry.Key == OtlpExporterOptions.StandardHeaders[i].Key && entry.Value.First() == OtlpExporterOptions.StandardHeaders[i].Value);
+                }
+
                 Assert.NotNull(httpRequest.Content);
                 Assert.IsType<OtlpHttpTraceExportClient.ExportRequestContent>(httpRequest.Content);
                 Assert.Contains(httpRequest.Content.Headers, h => h.Key == "Content-Type" && h.Value.First() == OtlpHttpTraceExportClient.MediaContentType);

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsExtensionsTests.cs

@@ -14,6 +14,7 @@
 // limitations under the License.
 // </copyright>
 
+using Grpc.Core;
 using OpenTelemetry.Exporter.OpenTelemetryProtocol.Implementation.ExportClient;
 using Xunit;
 using Xunit.Sdk;
@@ -37,12 +38,19 @@ public void GetMetadataFromHeadersWorksCorrectFormat(string headers, string[] ke
             };
             var metadata = options.GetMetadataFromHeaders();
 
-            Assert.Equal(keys.Length, metadata.Count);
+            Assert.Equal(OtlpExporterOptions.StandardHeaders.Length + keys.Length, metadata.Count);
 
             for (int i = 0; i < keys.Length; i++)
             {
                 Assert.Contains(metadata, entry => entry.Key == keys[i] && entry.Value == values[i]);
             }
+
+            for (int i = 0; i < OtlpExporterOptions.StandardHeaders.Length; i++)
+            {
+                // Metadata key is always converted to lowercase.
+                // See: https://cloud.google.com/dotnet/docs/reference/Grpc.Core/latest/Grpc.Core.Metadata.Entry#Grpc_Core_Metadata_Entry__ctor_System_String_System_String_
+                Assert.Contains(metadata, entry => entry.Key == OtlpExporterOptions.StandardHeaders[i].Key.ToLower() && entry.Value == OtlpExporterOptions.StandardHeaders[i].Value);
+            }
         }
 
         [Theory]
@@ -71,7 +79,7 @@ public void GetMetadataFromHeadersThrowsExceptionOnInvalidFormat(string headers)
         [Theory]
         [InlineData("")]
         [InlineData(null)]
-        public void GetHeaders_NoOptionHeaders_ReturnsEmptyHeaders(string optionHeaders)
+        public void GetHeaders_NoOptionHeaders_ReturnsStandardHeaders(string optionHeaders)
         {
             var options = new OtlpExporterOptions
             {
@@ -80,7 +88,12 @@ public void GetHeaders_NoOptionHeaders_ReturnsEmptyHeaders(string optionHeaders)
 
             var headers = options.GetHeaders<Dictionary<string, string>>((d, k, v) => d.Add(k, v));
 
-            Assert.Empty(headers);
+            Assert.Equal(OtlpExporterOptions.StandardHeaders.Length, headers.Count);
+
+            for (int i = 0; i < OtlpExporterOptions.StandardHeaders.Length; i++)
+            {
+                Assert.Contains(headers, entry => entry.Key == OtlpExporterOptions.StandardHeaders[i].Key && entry.Value == OtlpExporterOptions.StandardHeaders[i].Value);
+            }
         }
 
         [Theory]