opentelemetrytracer: Add User-Agent header to OTLP trace exporters

changelogs/current.yaml

@@ -255,6 +255,9 @@ new_features:
 - area: tracing
   change: |
     Added support to configure a Dynatrace sampler for the OpenTelemetry tracer.
+- area: tracing
+  change: |
+    Added User-Agent header to OTLP trace exporters according to the OpenTelemetry specification.
 
 deprecated:
 - area: listener

source/extensions/tracers/opentelemetry/BUILD

@@ -59,10 +59,12 @@ envoy_cc_library(
     srcs = [
         "grpc_trace_exporter.cc",
         "http_trace_exporter.cc",
+        "otlp_utils.cc",
     ],
     hdrs = [
         "grpc_trace_exporter.h",
         "http_trace_exporter.h",
+        "otlp_utils.h",
         "trace_exporter.h",
     ],
     deps = [
@@ -75,6 +77,7 @@ envoy_cc_library(
         "//source/common/http:utility_lib",
         "//source/common/protobuf",
         "//source/common/tracing:trace_context_lib",
+        "//source/common/version:version_lib",
         "@envoy_api//envoy/config/core/v3:pkg_cc_proto",
         "@opentelemetry_proto//:trace_cc_proto",
     ],

source/extensions/tracers/opentelemetry/grpc_trace_exporter.h

@@ -4,6 +4,7 @@
 
 #include "source/common/common/logger.h"
 #include "source/common/grpc/typed_async_client.h"
+#include "source/extensions/tracers/opentelemetry/otlp_utils.h"
 #include "source/extensions/tracers/opentelemetry/trace_exporter.h"
 
 #include "opentelemetry/proto/collector/trace/v1/trace_service.pb.h"
@@ -30,7 +31,9 @@ class OpenTelemetryGrpcTraceExporterClient : Logger::Loggable<Logger::Id::tracin
     LocalStream(OpenTelemetryGrpcTraceExporterClient& parent) : parent_(parent) {}
 
     // Grpc::AsyncStreamCallbacks
-    void onCreateInitialMetadata(Http::RequestHeaderMap&) override {}
+    void onCreateInitialMetadata(Http::RequestHeaderMap& metadata) override {
+      metadata.setReferenceUserAgent(OtlpUtils::getOtlpUserAgentHeader());
+    }
     void onReceiveInitialMetadata(Http::ResponseHeaderMapPtr&&) override {}
     void onReceiveMessage(
         std::unique_ptr<opentelemetry::proto::collector::trace::v1::ExportTraceServiceResponse>&&)

source/extensions/tracers/opentelemetry/http_trace_exporter.cc

@@ -8,6 +8,7 @@
 #include "source/common/common/enum_to_int.h"
 #include "source/common/common/logger.h"
 #include "source/common/protobuf/protobuf.h"
+#include "source/extensions/tracers/opentelemetry/otlp_utils.h"
 
 namespace Envoy {
 namespace Extensions {
@@ -50,6 +51,10 @@ bool OpenTelemetryHttpTraceExporter::log(const ExportTraceServiceRequest& reques
   message->headers().setReferenceMethod(Http::Headers::get().MethodValues.Post);
   message->headers().setReferenceContentType(Http::Headers::get().ContentTypeValues.Protobuf);
 
+  // User-Agent header follows the OTLP specification:
+  // https://github.com/open-telemetry/opentelemetry-specification/blob/v1.30.0/specification/protocol/exporter.md#user-agent
+  message->headers().setReferenceUserAgent(OtlpUtils::getOtlpUserAgentHeader());
+
   // Add all custom headers to the request.
   for (const auto& header_pair : parsed_headers_to_add_) {
     message->headers().setReference(header_pair.first, header_pair.second);

source/extensions/tracers/opentelemetry/otlp_utils.cc

@@ -0,0 +1,22 @@
+#include "source/extensions/tracers/opentelemetry/otlp_utils.h"
+
+#include <string>
+
+#include "source/common/common/fmt.h"
+#include "source/common/common/macros.h"
+#include "source/common/version/version.h"
+
+namespace Envoy {
+namespace Extensions {
+namespace Tracers {
+namespace OpenTelemetry {
+
+const std::string& OtlpUtils::getOtlpUserAgentHeader() {
+  CONSTRUCT_ON_FIRST_USE(std::string,
+                         fmt::format("OTel-OTLP-Exporter-Envoy/{}", Envoy::VersionInfo::version()));
+}
+
+} // namespace OpenTelemetry
+} // namespace Tracers
+} // namespace Extensions
+} // namespace Envoy

source/extensions/tracers/opentelemetry/otlp_utils.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <string>
+
+namespace Envoy {
+namespace Extensions {
+namespace Tracers {
+namespace OpenTelemetry {
+
+/**
+ * Contains utility functions  for Otel
+ */
+class OtlpUtils {
+
+public:
+  /**
+   * @brief Get the User-Agent header value to be used on the OTLP exporter request.
+   *
+   * The header value is compliant with the OpenTelemetry specification. See:
+   * https://github.com/open-telemetry/opentelemetry-specification/blob/v1.30.0/specification/protocol/exporter.md#user-agent
+   * @return std::string The User-Agent for the OTLP exporters in Envoy.
+   */
+  static const std::string& getOtlpUserAgentHeader();
+};
+
+} // namespace OpenTelemetry
+} // namespace Tracers
+} // namespace Extensions
+} // namespace Envoy

test/extensions/tracers/opentelemetry/grpc_trace_exporter_test.cc

@@ -1,6 +1,7 @@
 #include <sys/types.h>
 
 #include "source/common/buffer/zero_copy_input_stream_impl.h"
+#include "source/common/version/version.h"
 #include "source/extensions/tracers/opentelemetry/grpc_trace_exporter.h"
 
 #include "test/mocks/common.h"
@@ -70,6 +71,11 @@ TEST_F(OpenTelemetryGrpcTraceExporterTest, CreateExporterAndExportSpan) {
   span.set_name("test");
   *request.add_resource_spans()->add_scope_spans()->add_spans() = span;
   EXPECT_TRUE(exporter.log(request));
+
+  Http::TestRequestHeaderMapImpl metadata;
+  callbacks_->onCreateInitialMetadata(metadata);
+  EXPECT_EQ(metadata.getUserAgentValue(),
+            "OTel-OTLP-Exporter-Envoy/" + Envoy::VersionInfo::version());
 }
 
 TEST_F(OpenTelemetryGrpcTraceExporterTest, NoExportWithHighWatermark) {

test/extensions/tracers/opentelemetry/http_trace_exporter_test.cc

@@ -1,6 +1,7 @@
 #include <sys/types.h>
 
 #include "source/common/buffer/zero_copy_input_stream_impl.h"
+#include "source/common/version/version.h"
 #include "source/extensions/tracers/opentelemetry/http_trace_exporter.h"
 
 #include "test/mocks/common.h"
@@ -78,6 +79,8 @@ TEST_F(OpenTelemetryHttpTraceExporterTest, CreateExporterAndExportSpan) {
             callback = &callbacks;
 
             EXPECT_EQ(Http::Headers::get().MethodValues.Post, message->headers().getMethodValue());
+            EXPECT_EQ(message->headers().getUserAgentValue(),
+                      "OTel-OTLP-Exporter-Envoy/" + Envoy::VersionInfo::version());
             EXPECT_EQ(Http::Headers::get().ContentTypeValues.Protobuf,
                       message->headers().getContentTypeValue());