otlptracegrpc: error setting OTEL_EXPORTER_OTLP_ENDPOINT with a path

[godart]

Description

Setting
OTEL_EXPORTER_OTLP_ENDPOINT=https://example.com:4317/v1/traces
results in the gRPC exporter failing with
traces export: exporter export timeout: rpc error: code = Unavailable desc = connection error: desc = "transport: Error while dialing: dial tcp: lookup tcp/4317/v1/traces: unknown port"

This seems to be an error with the env variables being parsed here:

opentelemetry-go/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/envconfig.go

Line 117 in 207b0c5

cfg.Traces.Endpoint = path.Join(u.Host, u.Path)

That joining of the hostname and path into endpoint results the HTTP transport try a DNS lookup with example.com:4317/v1/traces which is not a valid hostname.

There is also a misleading example in the documentation here:
https://pkg.go.dev/go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc#WithEndpointURL

Environment

• OS: Linux
• Architecture: x64
• Go Version: 1.25.5
• opentelemetry-go version: v1.39.0

Steps To Reproduce

Set OTEL_EXPORTER_OTLP_ENDPOINT=https://example.com:4317/v1/traces
Setup code:

	res, err := resource.New(
		ctx,
		resource.WithFromEnv(), // Discover and provide attributes from OTEL_RESOURCE_ATTRIBUTES and OTEL_SERVICE_NAME environment variables.
		resource.WithTelemetrySDK(),
		resource.WithContainer(),
	)

	traceExporter, err := otlptracegrpc.New(ctx)
	if err != nil {
		return nil, fmt.Errorf("otlptracegrpc.New: %v", err)
	}
	tracerProvider := sdktrace.NewTracerProvider(
		sdktrace.WithBatcher(traceExporter),
		sdktrace.WithSampler(sdktrace.TraceIDRatioBased(1)),
		sdktrace.WithResource(res),
	)
	otel.SetTracerProvider(tracerProvider)

Then force a trace to be created and written.

Expected behavior

Not 100% what is best here. Maybe parsing the URL and rejecting it if there is a ulr.Paht present. That is because gRPC uses the path as part of the service / method discovery and binding.

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[aryan735]

I’m working on this issue. I will open PR soon.

[aryan735]

Hi,
I’ve opened a PR that addresses this issue: #7836

PR: #7836