improve OTLP/gRPC connection errors (#1737)

* improve OTLP/gRPC connection errors

* Update CHANGELOG.md

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -24,6 +24,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
   The existing `ParentSpanID` and `HasRemoteParent` fields are removed in favor of this. (#1748)
 - The `ParentContext` field of the `"go.opentelemetry.io/otel/sdk/trace".SamplingParameters` is updated to hold a `context.Context` containing the parent span.
   This changes it to make `SamplingParameters` conform with the OpenTelemetry specification. (#1749)
+- Improve OTLP/gRPC exporter connection errors. (#1737)
 
 ### Removed
 

exporters/otlp/otlpgrpc/driver.go

@@ -41,8 +41,7 @@ type driver struct {
 }
 
 var (
-	errNoClient     = errors.New("no client")
-	errDisconnected = errors.New("exporter disconnected")
+	errNoClient = errors.New("no client")
 )
 
 // NewDriver creates a new gRPC protocol driver.
@@ -88,7 +87,7 @@ func (d *driver) Stop(ctx context.Context) error {
 // to protobuf binary format and sends the result to the collector.
 func (d *driver) ExportMetrics(ctx context.Context, cps metricsdk.CheckpointSet, selector metricsdk.ExportKindSelector) error {
 	if !d.connection.connected() {
-		return errDisconnected
+		return fmt.Errorf("exporter disconnected: %w", d.connection.lastConnectError())
 	}
 	ctx, cancel := d.connection.contextWithStop(ctx)
 	defer cancel()
@@ -127,7 +126,7 @@ func (d *driver) uploadMetrics(ctx context.Context, protoMetrics []*metricpb.Res
 // protobuf binary format and sends the result to the collector.
 func (d *driver) ExportTraces(ctx context.Context, ss []*tracesdk.SpanSnapshot) error {
 	if !d.connection.connected() {
-		return errDisconnected
+		return fmt.Errorf("exporter disconnected: %w", d.connection.lastConnectError())
 	}
 	ctx, cancel := d.connection.contextWithStop(ctx)
 	defer cancel()

exporters/otlp/otlpgrpc/otlp_integration_test.go

@@ -316,6 +316,27 @@ func TestNewExporter_withHeaders(t *testing.T) {
 	assert.Equal(t, "value1", headers.Get("header1")[0])
 }
 
+func TestNewExporter_withInvalidSecurityConfiguration(t *testing.T) {
+	mc := runMockCollector(t)
+	defer func() {
+		_ = mc.stop()
+	}()
+
+	ctx := context.Background()
+	driver := otlpgrpc.NewDriver(otlpgrpc.WithEndpoint(mc.endpoint))
+	exp, err := otlp.NewExporter(ctx, driver)
+	if err != nil {
+		t.Fatalf("failed to create a new collector exporter: %v", err)
+	}
+
+	err = exp.ExportSpans(ctx, []*exporttrace.SpanSnapshot{{Name: "misconfiguration"}})
+	require.Equal(t, err.Error(), "exporter disconnected: grpc: no transport security set (use grpc.WithInsecure() explicitly or set credentials)")
+
+	defer func() {
+		_ = exp.Shutdown(ctx)
+	}()
+}
+
 func TestNewExporter_withMultipleAttributeTypes(t *testing.T) {
 	mc := runMockCollector(t)