otlptracehttp: Add WithHTTPClient option (#6751)

Follows #6688

Towards (for OTLP trace exporter):
- #4536
- #5129
- #2632

Author: pellared

CHANGELOG.md

@@ -15,8 +15,9 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   The package contains semantic conventions from the `v1.31.0` version of the OpenTelemetry Semantic Conventions.
   See the [migration documentation](./semconv/v1.31.0/MIGRATION.md) for information on how to upgrade from `go.opentelemetry.io/otel/semconv/v1.30.0`(#6479)
 - Add `Recording`, `Scope`, and `Record` types in `go.opentelemetry.io/otel/log/logtest`. (#6507)
-- Add `WithHTTPClient` option to configure the `http.Client` used by `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#6688)
+- Add `WithHTTPClient` option to configure the `http.Client` used by `go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`. (#6751)
 - Add `WithHTTPClient` option to configure the `http.Client` used by `go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`. (#6752)
+- Add `WithHTTPClient` option to configure the `http.Client` used by `go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#6688)
 
 ### Removed
 

exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options.go

@@ -71,20 +71,24 @@ var _ otlptrace.Client = (*client)(nil)
 func NewClient(opts ...Option) otlptrace.Client {
 	cfg := otlpconfig.NewHTTPConfig(asHTTPOptions(opts)...)
 
-	httpClient := &http.Client{
-		Transport: ourTransport,
-		Timeout:   cfg.Traces.Timeout,
-	}
-
-	if cfg.Traces.TLSCfg != nil || cfg.Traces.Proxy != nil {
-		clonedTransport := ourTransport.Clone()
-		httpClient.Transport = clonedTransport
+	httpClient := cfg.Traces.HTTPClient
 
-		if cfg.Traces.TLSCfg != nil {
-			clonedTransport.TLSClientConfig = cfg.Traces.TLSCfg
+	if httpClient == nil {
+		httpClient = &http.Client{
+			Transport: ourTransport,
+			Timeout:   cfg.Traces.Timeout,
 		}
-		if cfg.Traces.Proxy != nil {
-			clonedTransport.Proxy = cfg.Traces.Proxy
+
+		if cfg.Traces.TLSCfg != nil || cfg.Traces.Proxy != nil {
+			clonedTransport := ourTransport.Clone()
+			httpClient.Transport = clonedTransport
+
+			if cfg.Traces.TLSCfg != nil {
+				clonedTransport.TLSClientConfig = cfg.Traces.TLSCfg
+			}
+			if cfg.Traces.Proxy != nil {
+				clonedTransport.Proxy = cfg.Traces.Proxy
+			}
 		}
 	}
 

exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options_test.go

@@ -153,3 +153,19 @@ func WithRetry(rc RetryConfig) Option {
 func WithProxy(pf HTTPTransportProxyFunc) Option {
 	return wrappedOption{otlpconfig.WithProxy(otlpconfig.HTTPTransportProxyFunc(pf))}
 }
+
+// WithHTTPClient sets the HTTP client to used by the exporter.
+//
+// This option will take precedence over [WithProxy], [WithTimeout],
+// [WithTLSClientConfig] options as well as OTEL_EXPORTER_OTLP_CERTIFICATE,
+// OTEL_EXPORTER_OTLP_TRACES_CERTIFICATE, OTEL_EXPORTER_OTLP_TIMEOUT,
+// OTEL_EXPORTER_OTLP_TRACES_TIMEOUT environment variables.
+//
+// Timeout and all other fields of the passed [http.Client] are left intact.
+//
+// Be aware that passing an HTTP client with transport like
+// [go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp.NewTransport] can
+// cause the client to be instrumented twice and cause infinite recursion.
+func WithHTTPClient(c *http.Client) Option {
+	return wrappedOption{otlpconfig.WithHTTPClient(c)}
+}

exporters/otlp/otlptrace/otlptracehttp/client.go

@@ -53,7 +53,9 @@ type (
 		// gRPC configurations
 		GRPCCredentials credentials.TransportCredentials
 
-		Proxy HTTPTransportProxyFunc
+		// HTTP configurations
+		Proxy      HTTPTransportProxyFunc
+		HTTPClient *http.Client
 	}
 
 	Config struct {
@@ -350,3 +352,10 @@ func WithProxy(pf HTTPTransportProxyFunc) GenericOption {
 		return cfg
 	})
 }
+
+func WithHTTPClient(c *http.Client) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Traces.HTTPClient = c
+		return cfg
+	})
+}

exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go

@@ -483,6 +483,24 @@ func TestConfigs(t *testing.T) {
 				assert.Nil(t, c.Traces.Proxy)
 			},
 		},
+
+		// HTTP Client Tests
+		{
+			name: "Test With HTTP Client",
+			opts: []GenericOption{
+				WithHTTPClient(http.DefaultClient),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, http.DefaultClient, c.Traces.HTTPClient)
+			},
+		},
+		{
+			name: "Test Without HTTP Client",
+			opts: []GenericOption{},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Nil(t, c.Traces.HTTPClient)
+			},
+		},
 	}
 
 	for _, tt := range tests {