VTGate.Execute returns errors in RPC response

go/vt/tabletserver/gorpctabletconn/conn.go

@@ -494,4 +494,4 @@ func tabletErrorFromVitessError(ve *vterrors.VitessError) error {
 	}
 
 	return tabletconn.OperationalError(fmt.Sprintf("vttablet: %v", ve.Message))
-}
+}

go/vt/vtgate/gorpcvtgateservice/server.go

@@ -31,7 +31,12 @@ func (vtg *VTGate) Execute(ctx context.Context, query *proto.Query, reply *proto
 	defer vtg.server.HandlePanic(&err)
 	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(*rpcTimeout))
 	defer cancel()
-	return vtg.server.Execute(ctx, query, reply)
+	vtgErr := vtg.server.Execute(ctx, query, reply)
+	vtgate.AddVtGateErrorToQueryResult(vtgErr, reply)
+	if *vtgate.RPCErrorOnlyInReply {
+		return nil
+	}
+	return vtgErr
 }
 
 // ExecuteShard is the RPC version of vtgateservice.VTGateService method
@@ -39,7 +44,12 @@ func (vtg *VTGate) ExecuteShard(ctx context.Context, query *proto.QueryShard, re
 	defer vtg.server.HandlePanic(&err)
 	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(*rpcTimeout))
 	defer cancel()
-	return vtg.server.ExecuteShard(ctx, query, reply)
+	vtgErr := vtg.server.ExecuteShard(ctx, query, reply)
+	vtgate.AddVtGateErrorToQueryResult(vtgErr, reply)
+	if *vtgate.RPCErrorOnlyInReply {
+		return nil
+	}
+	return vtgErr
 }
 
 // ExecuteKeyspaceIds is the RPC version of vtgateservice.VTGateService method
@@ -47,7 +57,12 @@ func (vtg *VTGate) ExecuteKeyspaceIds(ctx context.Context, query *proto.Keyspace
 	defer vtg.server.HandlePanic(&err)
 	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(*rpcTimeout))
 	defer cancel()
-	return vtg.server.ExecuteKeyspaceIds(ctx, query, reply)
+	vtgErr := vtg.server.ExecuteKeyspaceIds(ctx, query, reply)
+	vtgate.AddVtGateErrorToQueryResult(vtgErr, reply)
+	if *vtgate.RPCErrorOnlyInReply {
+		return nil
+	}
+	return vtgErr
 }
 
 // ExecuteKeyRanges is the RPC version of vtgateservice.VTGateService method
@@ -55,7 +70,12 @@ func (vtg *VTGate) ExecuteKeyRanges(ctx context.Context, query *proto.KeyRangeQu
 	defer vtg.server.HandlePanic(&err)
 	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(*rpcTimeout))
 	defer cancel()
-	return vtg.server.ExecuteKeyRanges(ctx, query, reply)
+	vtgErr := vtg.server.ExecuteKeyRanges(ctx, query, reply)
+	vtgate.AddVtGateErrorToQueryResult(vtgErr, reply)
+	if *vtgate.RPCErrorOnlyInReply {
+		return nil
+	}
+	return vtgErr
 }
 
 // ExecuteEntityIds is the RPC version of vtgateservice.VTGateService method
@@ -63,7 +83,12 @@ func (vtg *VTGate) ExecuteEntityIds(ctx context.Context, query *proto.EntityIdsQ
 	defer vtg.server.HandlePanic(&err)
 	ctx, cancel := context.WithDeadline(ctx, time.Now().Add(*rpcTimeout))
 	defer cancel()
-	return vtg.server.ExecuteEntityIds(ctx, query, reply)
+	vtgErr := vtg.server.ExecuteEntityIds(ctx, query, reply)
+	vtgate.AddVtGateErrorToQueryResult(vtgErr, reply)
+	if *vtgate.RPCErrorOnlyInReply {
+		return nil
+	}
+	return vtgErr
 }
 
 // ExecuteBatchShard is the RPC version of vtgateservice.VTGateService method

go/vt/vtgate/proto/vtgate_proto.go

@@ -121,6 +121,7 @@ type QueryResult struct {
 	Result  *mproto.QueryResult
 	Session *Session
 	Error   string
+	Err     *mproto.RPCError
 }
 
 //go:generate bsongen -file $GOFILE -type QueryResult -o query_result_bson.go

go/vt/vtgate/vtgate.go

@@ -8,6 +8,7 @@ package vtgate
 
 import (
 	"errors"
+	"flag"
 	"fmt"
 	"math"
 	"strings"
@@ -84,6 +85,11 @@ type RegisterVTGate func(vtgateservice.VTGateService)
 // RegisterVTGates stores register funcs for VTGate server.
 var RegisterVTGates []RegisterVTGate
 
+var (
+	// RPCErrorOnlyInReply informs vtgateservice(s) about how to return errors.
+	RPCErrorOnlyInReply = flag.Bool("rpc-error-only-in-reply", false, "if true, supported RPC calls from vtgateservice(s) will only return errors as part of the RPC server response")
+)
+
 // Init initializes VTGate server.
 func Init(serv SrvTopoServer, schema *planbuilder.Schema, cell string, retryDelay time.Duration, retryCount int, connTimeoutTotal, connTimeoutPerConn, connLife time.Duration, maxInFlight int) {
 	if rpcVTGate != nil {

go/vt/vtgate/vtgate_error.go

@@ -0,0 +1,34 @@
+// Copyright 2012, Google Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package vtgate
+
+import (
+	mproto "github.com/youtube/vitess/go/mysql/proto"
+	"github.com/youtube/vitess/go/vt/vterrors"
+	"github.com/youtube/vitess/go/vt/vtgate/proto"
+)
+
+// rpcErrFromTabletError translate an error from VTGate to an *mproto.RPCError
+func rpcErrFromVtGateError(err error) *mproto.RPCError {
+	if err == nil {
+		return nil
+	}
+	// TODO(aaijazi): for now, we don't have any differentiation of VtGate errors.
+	// However, we should have them soon, so that clients don't have to parse the
+	// returned error string.
+	return &mproto.RPCError{
+		Code:    vterrors.UnknownVtgateError,
+		Message: err.Error(),
+	}
+}
+
+// AddVtGateErrorToQueryResult will mutate a QueryResult struct to fill in the Err
+// field with details from the VTGate error.
+func AddVtGateErrorToQueryResult(err error, reply *proto.QueryResult) {
+	if err == nil {
+		return
+	}
+	reply.Err = rpcErrFromVtGateError(err)
+}

go/vt/vtgate/vtgateconn/vtgateconn_test.go

@@ -43,6 +43,6 @@ func TestServerError(t *testing.T) {
 
 func TestOperationalError(t *testing.T) {
 	if OperationalError("error").Error() == "" {
-		t.Fatal("operational error is not mepty, should not return empty error")
+		t.Fatal("operational error is not empty, should not return empty error")
 	}
 }