thanos-io/thanos · error

otlp: invalid client type. Only 'http' and 'grpc' are…

Error message

otlp: invalid client type. Only 'http' and 'grpc' are accepted. 

What it means

In pkg/tracing/otlp NewTracerProvider, the switch over the configured OTLP client type only handles 'http' and 'grpc'; any other value reaches the default branch and returns this sentinel error. OTLP exporter construction never happens, so no spans can be exported.

Solutions

1. Set the OTLP client type to exactly 'http' or 'grpc' (lowercase, no slashes)
2. Use 'grpc' for port 4317 and 'http' for port 4318 to match your collector
3. Fix typos and avoid casing variants
4. Consult the wrapped error/logs to confirm which value was parsed

Example fix

// before
config:
  client_type: HTTP/protobuf
  endpoint: otel:4318
// after
config:
  client_type: http
  endpoint: otel:4318

// Before invoking the OTLP tracing path
if ct, ok := cfg["client_type"]; !ok {
    return fmt.Errorf("otlp config missing client_type")
} else if ct != "http" && ct != "grpc" {
    return fmt.Errorf("otlp client_type %q invalid: only 'http' and 'grpc' accepted", ct)
}

func validOTLPClientType(v interface{}) bool {
    s, ok := v.(string)
    return ok && (s == "http" || s == "grpc")
}

tracer, closer, err := tracing.NewTracer(ctx, logger, reg, cfgYaml)
if err != nil && strings.Contains(err.Error(), "invalid client type") {
    logger.Error(err, "set otlp client_type to 'http' or 'grpc'")
    return err
}

When it happens

Trigger: OTLP tracing config with client_type set to something other than 'http' or 'grpc' (e.g. 'http/protobuf', 'HTTP', 'grcp', or empty).

Common situations: Copying OpenTelemetry SDK config conventions (http/protobuf) into Thanos config, casing mistakes, or typos like 'grcp'.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• tracing failed
• error getting tenant from HTTP
• internal server error
• Error decoding remote write request
• error converting OTLP metrics to Prometheus format

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/05c91972e8910ba4. Report an issue: GitHub.

Appendix: source

Thrown at pkg/tracing/otlp/otlp.go:65

	case TracingClientHTTP:
		options := traceHTTPOptions(config)

		client := otlptracehttp.NewClient(options...)
		exporter, err = otlptrace.New(ctx, client)
		if err != nil {
			return nil, err
		}

	case TracingClientGRPC:
		options := traceGRPCOptions(config)
		client := otlptracegrpc.NewClient(options...)
		exporter, err = otlptrace.New(ctx, client)
		if err != nil {
			return nil, err
		}

	default:
		return nil, errors.New("otlp: invalid client type. Only 'http' and 'grpc' are accepted. ")
	}

	processor := tracesdk.NewBatchSpanProcessor(exporter)
	sampler, err := getSampler(config)
	if err != nil {
		logger.Log(err)
	}
	tp := newTraceProvider(ctx, processor, logger, config.ServiceName, config.ResourceAttributes, sampler)

	return tp, nil
}

func newTraceProvider(
	ctx context.Context,
	processor tracesdk.SpanProcessor,
	logger log.Logger,
	serviceName string,
	attrs map[string]string,

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