improve error messages

exporter/otelcollector/otelcollector.go

@@ -61,13 +61,13 @@ func httpExporterWithOptions(ctx context.Context, cfg config.OTLPExporter,
 	tOpts = append(tOpts, otlptracehttp.WithEndpoint(endpoint))
 	exporter, err := otlptracehttp.New(ctx, tOpts...)
 	if err != nil {
-		return nil, errors.New("cannot create http trace exporter")
+		return nil, errors.New("cannot create http trace exporter:" + err.Error())
 	}
 
 	mOpts = append(mOpts, otlpmetrichttp.WithEndpoint(endpoint))
 	metricExporter, err := otlpmetrichttp.New(ctx, mOpts...)
 	if err != nil {
-		return nil, errors.New("cannot create http metric exporter")
+		return nil, errors.New("cannot create http metric exporter:" + err.Error())
 	}
 
 	return &OtelCollector{

state/state.go

@@ -131,14 +131,23 @@ func (s *OTELState) Tracer() trace.Tracer {
 
 // Meter returns a meter to create metric instruments.
 func (s *OTELState) Meter() metric.Meter {
+	if s == nil {
+		return nil
+	}
 	return s.meter
 }
 
 func (s *OTELState) MeterProvider() metric.MeterProvider {
+	if s == nil {
+		return nil
+	}
 	return s.meterProvider
 }
 
 func (s *OTELState) TracerProvider() trace.TracerProvider {
+	if s == nil {
+		return nil
+	}
 	return s.tracerProvider
 }
 
@@ -153,6 +162,9 @@ func (s *OTELState) Propagator() propagation.TextMapPropagator {
 // Shutdown performs the clean shutdown to be able to
 // flush pending traces and / or metrics.
 func (s *OTELState) Shutdown(ctx context.Context) {
+	if s == nil {
+		return
+	}
 	if s.sdkTracerProvider != nil {
 		s.sdkTracerProvider.Shutdown(ctx)
 	}