chore: give hint of configuration on otel invalid utf8 errors

router-tests/telemetry/attribute_processor_test.go

@@ -1,15 +1,19 @@
 package telemetry
 
 import (
+	"context"
+	"fmt"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 	"github.com/wundergraph/cosmo/router-tests/testenv"
 	"github.com/wundergraph/cosmo/router/core"
 	"github.com/wundergraph/cosmo/router/pkg/config"
 	"github.com/wundergraph/cosmo/router/pkg/trace/tracetest"
 	"go.opentelemetry.io/otel/attribute"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
 	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
 	"go.uber.org/zap/zapcore"
 )
@@ -184,6 +188,32 @@ func TestAttributeProcessorIntegration(t *testing.T) {
 		})
 	})
 
+	t.Run("invalid UTF-8 export error logs config hint", func(t *testing.T) {
+		t.Parallel()
+
+		testenv.Run(t, &testenv.Config{
+			TraceExporter: &invalidUTF8Exporter{},
+			LogObservation: testenv.LogObservationConfig{
+				Enabled:  true,
+				LogLevel: zapcore.ErrorLevel,
+			},
+		}, func(t *testing.T, xEnv *testenv.Environment) {
+			res := xEnv.MakeGraphQLRequestOK(testenv.GraphQLRequest{
+				Query: `query { employees { id } }`,
+			})
+			require.Equal(t, 200, res.Response.StatusCode)
+
+			require.Eventually(t, func() bool {
+				logs := xEnv.Observer().FilterMessageSnippet("sanitize_utf8").All()
+				return len(logs) > 0
+			}, 5*time.Second, 100*time.Millisecond)
+
+			logs := xEnv.Observer().FilterMessageSnippet("sanitize_utf8").All()
+			require.NotEmpty(t, logs)
+			require.Equal(t, logs[0].Message, "otel error: traces export: string field contains invalid UTF-8: Enable 'telemetry.tracing.sanitize_utf8.enabled' in your config to sanitize invalid UTF-8 attributes.")
+		})
+	})
+
 	t.Run("IPAnonymization hashes IP attributes", func(t *testing.T) {
 		t.Parallel()
 
@@ -220,3 +250,20 @@ func TestAttributeProcessorIntegration(t *testing.T) {
 		})
 	})
 }
+
+// errInvalidUTF8 mimics google.golang.org/protobuf/internal/impl.errInvalidUTF8
+// so that errors.As can match it via the invalidUTF8Error interface used in the router.
+type errInvalidUTF8 struct{}
+
+func (errInvalidUTF8) Error() string     { return "string field contains invalid UTF-8" }
+func (errInvalidUTF8) InvalidUTF8() bool { return true }
+
+type invalidUTF8Exporter struct{}
+
+func (e *invalidUTF8Exporter) ExportSpans(_ context.Context, _ []sdktrace.ReadOnlySpan) error {
+	return fmt.Errorf("traces export: %w", errInvalidUTF8{})
+}
+
+func (e *invalidUTF8Exporter) Shutdown(_ context.Context) error {
+	return nil
+}

router/pkg/trace/errors.go

@@ -0,0 +1,34 @@
+package trace
+
+import (
+	"errors"
+	"go.uber.org/zap"
+)
+
+// invalidUTF8Error matches the InvalidUTF8() method exposed by
+// google.golang.org/protobuf/internal/impl.errInvalidUTF8.
+type invalidUTF8Error interface {
+	InvalidUTF8() bool
+}
+
+// hasInvalidUTF8Error walks the error chain looking for an error
+// that implements the invalidUTF8Error interface.
+func hasInvalidUTF8Error(err error) bool {
+	var target invalidUTF8Error
+	if errors.As(err, &target) {
+		return target.InvalidUTF8()
+	}
+	return false
+}
+
+func errHandler(config *ProviderConfig) func(err error) {
+	return func(err error) {
+		if hasInvalidUTF8Error(err) {
+			config.Logger.Error(
+				"otel error: traces export: string field contains invalid UTF-8: Enable 'telemetry.tracing.sanitize_utf8.enabled' in your config to sanitize invalid UTF-8 attributes.",
+				zap.Error(err))
+			return
+		}
+		config.Logger.Error("otel error", zap.Error(err))
+	}
+}

router/pkg/trace/meter.go

@@ -219,9 +219,7 @@ func NewTracerProvider(ctx context.Context, config *ProviderConfig) (*sdktrace.T
 		otel.SetTracerProvider(tp)
 	}
 
-	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) {
-		config.Logger.Error("otel error", zap.Error(err))
-	}))
+	otel.SetErrorHandler(otel.ErrorHandlerFunc(errHandler(config)))
 
 	return tp, nil
 }