standardize error class and add span error tags

go/otgrpc/client.go

@@ -72,8 +72,8 @@ func OpenTracingClientInterceptor(tracer opentracing.Tracer, optFuncs ...Option)
 				clientSpan.LogFields(log.Object("gRPC response", resp))
 			}
 		} else {
+			SetSpanTags(clientSpan, err, true)
 			clientSpan.LogFields(log.String("event", "gRPC error"), log.Error(err))
-			ext.Error.Set(clientSpan, true)
 		}
 		if otgrpcOpts.decorator != nil {
 			otgrpcOpts.decorator(clientSpan, method, req, resp, err)

go/otgrpc/errors.go

@@ -0,0 +1,66 @@
+package otgrpc
+
+import (
+	"github.com/opentracing/opentracing-go"
+	"github.com/opentracing/opentracing-go/ext"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// A Class is a set of types of outcomes (including errors) that will often
+// be handled in the same way.
+type Class string
+
+const (
+	Unknown Class = "0xx"
+	// Success represents outcomes that achieved the desired results.
+	Success Class = "2xx"
+	// ClientError represents errors that were the client's fault.
+	ClientError Class = "4xx"
+	// ServerError represents errors that were the server's fault.
+	ServerError Class = "5xx"
+)
+
+// ErrorClass returns the class of the given error
+func ErrorClass(err error) Class {
+	if s, ok := status.FromError(err); ok {
+		switch s.Code() {
+		// Success or "success"
+		case codes.OK, codes.Canceled:
+			return Success
+
+		// Client errors
+		case codes.InvalidArgument, codes.NotFound, codes.AlreadyExists,
+			codes.PermissionDenied, codes.Unauthenticated, codes.FailedPrecondition,
+			codes.OutOfRange:
+			return ClientError
+
+		// Server errors
+		case codes.DeadlineExceeded, codes.ResourceExhausted, codes.Aborted,
+			codes.Unimplemented, codes.Internal, codes.Unavailable, codes.DataLoss:
+			return ServerError
+
+		// Not sure
+		case codes.Unknown:
+			fallthrough
+		default:
+			return Unknown
+		}
+	}
+	return Unknown
+}
+
+// SetSpanTags sets one or more tags on the given span according to the
+// error.
+func SetSpanTags(span opentracing.Span, err error, client bool) {
+	c := ErrorClass(err)
+	code := codes.Unknown
+	if s, ok := status.FromError(err); ok {
+		code = s.Code()
+	}
+	span.SetTag("response_code", code)
+	span.SetTag("response_class", c)
+	if client || c == ServerError {
+		ext.Error.Set(span, true)
+	}
+}

go/otgrpc/server.go

@@ -64,7 +64,7 @@ func OpenTracingServerInterceptor(tracer opentracing.Tracer, optFuncs ...Option)
 				serverSpan.LogFields(log.Object("gRPC response", resp))
 			}
 		} else {
-			ext.Error.Set(serverSpan, true)
+			SetSpanTags(serverSpan, err, false)
 			serverSpan.LogFields(log.String("event", "gRPC error"), log.Error(err))
 		}
 		if otgrpcOpts.decorator != nil {