I'm new to golang and wanted to experiment with grpc code to get a better understanding of it. In order to do so I followed the example shown here:
https://devicharan.wordpress.com/
The source code is here: https://github.com/devicharan/basicwebapp
Unfortunately, when I run this code and do a go build I get an error message with the following:
# basicwebapp/proto
proto/CatalogService.pb.go:126: cannot use _CatalogService_GetProductCatalog_Handler (type func(interface {}, context.Context, []byte) (proto.Message, error)) as type grpc.methodHandler in field value
proto/RecommendationService.pb.go:99: cannot use _RecommendationService_GetRecommendations_Handler (type func(interface {}, context.Context, []byte) (proto.Message, error)) as type grpc.methodHandler in field value
I don't know what this means or what I need to change in order to begin finding a fix. Is it a problem with the code itself or with my Go configuration? Also, is there a good debugger for Go that someone can recommend?
Here is the code for CatalogService.pb.go:
// Code generated by protoc-gen-go.
// source: CatalogService.proto
// DO NOT EDIT!
/*
Package protos is a generated protocol buffer package.
It is generated from these files:
CatalogService.proto
Product.proto
RecommendationService.proto
It has these top-level messages:
Category
CatalogResponse
CatalogRequest
*/
package protos
import proto "github.com/golang/protobuf/proto"
import (
context "golang.org/x/net/context"
grpc "google.golang.org/grpc"
)
// Reference imports to suppress errors if they are not otherwise used.
var _ context.Context
var _ grpc.ClientConn
// Reference imports to suppress errors if they are not otherwise used.
var _ = proto.Marshal
type Category struct {
CategoryName string `protobuf:"bytes,1,opt,name=categoryName" json:"categoryName,omitempty"`
}
func (m *Category) Reset() { *m = Category{} }
func (m *Category) String() string { return proto.CompactTextString(m) }
func (*Category) ProtoMessage() {}
type CatalogResponse struct {
Products []*Product `protobuf:"bytes,1,rep,name=products" json:"products,omitempty"`
}
func (m *CatalogResponse) Reset() { *m = CatalogResponse{} }
func (m *CatalogResponse) String() string { return proto.CompactTextString(m) }
func (*CatalogResponse) ProtoMessage() {}
func (m *CatalogResponse) GetProducts() []*Product {
if m != nil {
return m.Products
}
return nil
}
type CatalogRequest struct {
Category *Category `protobuf:"bytes,1,opt,name=category" json:"category,omitempty"`
}
func (m *CatalogRequest) Reset() { *m = CatalogRequest{} }
func (m *CatalogRequest) String() string { return proto.CompactTextString(m) }
func (*CatalogRequest) ProtoMessage() {}
func (m *CatalogRequest) GetCategory() *Category {
if m != nil {
return m.Category
}
return nil
}
func init() {
}
// Client API for CatalogService service
type CatalogServiceClient interface {
GetProductCatalog(ctx context.Context, in *CatalogRequest, opts ...grpc.CallOption) (*CatalogResponse, error)
}
type catalogServiceClient struct {
cc *grpc.ClientConn
}
func NewCatalogServiceClient(cc *grpc.ClientConn) CatalogServiceClient {
return &catalogServiceClient{cc}
}
func (c *catalogServiceClient) GetProductCatalog(ctx context.Context, in *CatalogRequest, opts ...grpc.CallOption) (*CatalogResponse, error) {
out := new(CatalogResponse)
err := grpc.Invoke(ctx, "/protos.CatalogService/GetProductCatalog", in, out, c.cc, opts...)
if err != nil {
return nil, err
}
return out, nil
}
// Server API for CatalogService service
type CatalogServiceServer interface {
GetProductCatalog(context.Context, *CatalogRequest) (*CatalogResponse, error)
}
func RegisterCatalogServiceServer(s *grpc.Server, srv CatalogServiceServer) {
s.RegisterService(&_CatalogService_serviceDesc, srv)
}
func _CatalogService_GetProductCatalog_Handler(srv interface{}, ctx context.Context, buf []byte) (proto.Message, error) {
in := new(CatalogRequest)
if err := proto.Unmarshal(buf, in); err != nil {
return nil, err
}
out, err := srv.(CatalogServiceServer).GetProductCatalog(ctx, in)
if err != nil {
return nil, err
}
return out, nil
}
var _CatalogService_serviceDesc = grpc.ServiceDesc{
ServiceName: "protos.CatalogService",
HandlerType: (*CatalogServiceServer)(nil),
Methods: []grpc.MethodDesc{
{
MethodName: "GetProductCatalog",
Handler: _CatalogService_GetProductCatalog_Handler,
},
},
Streams: []grpc.StreamDesc{},
}
And this is RecommendationService.pg.go
// Code generated by protoc-gen-go.
// source: RecommendationService.proto
// DO NOT EDIT!
package protos
import proto "github.com/golang/protobuf/proto"
import (
context "golang.org/x/net/context"
grpc "google.golang.org/grpc"
)
// Reference imports to suppress errors if they are not otherwise used.
var _ context.Context
var _ grpc.ClientConn
// Reference imports to suppress errors if they are not otherwise used.
var _ = proto.Marshal
type RecommendationResponse struct {
Result []*RecommendationResponse_Recommendation `protobuf:"bytes,1,rep,name=result" json:"result,omitempty"`
}
func (m *RecommendationResponse) Reset() { *m = RecommendationResponse{} }
func (m *RecommendationResponse) String() string { return proto.CompactTextString(m) }
func (*RecommendationResponse) ProtoMessage() {}
func (m *RecommendationResponse) GetResult() []*RecommendationResponse_Recommendation {
if m != nil {
return m.Result
}
return nil
}
type RecommendationResponse_Recommendation struct {
Rating int32 `protobuf:"varint,1,opt,name=rating" json:"rating,omitempty"`
Productid int32 `protobuf:"varint,2,opt,name=productid" json:"productid,omitempty"`
}
func (m *RecommendationResponse_Recommendation) Reset() { *m = RecommendationResponse_Recommendation{} }
func (m *RecommendationResponse_Recommendation) String() string { return proto.CompactTextString(m) }
func (*RecommendationResponse_Recommendation) ProtoMessage() {}
func init() {
}
// Client API for RecommendationService service
type RecommendationServiceClient interface {
GetRecommendations(ctx context.Context, in *Product, opts ...grpc.CallOption) (*RecommendationResponse, error)
}
type recommendationServiceClient struct {
cc *grpc.ClientConn
}
func NewRecommendationServiceClient(cc *grpc.ClientConn) RecommendationServiceClient {
return &recommendationServiceClient{cc}
}
func (c *recommendationServiceClient) GetRecommendations(ctx context.Context, in *Product, opts ...grpc.CallOption) (*RecommendationResponse, error) {
out := new(RecommendationResponse)
err := grpc.Invoke(ctx, "/protos.RecommendationService/GetRecommendations", in, out, c.cc, opts...)
if err != nil {
return nil, err
}
return out, nil
}
// Server API for RecommendationService service
type RecommendationServiceServer interface {
GetRecommendations(context.Context, *Product) (*RecommendationResponse, error)
}
func RegisterRecommendationServiceServer(s *grpc.Server, srv RecommendationServiceServer) {
s.RegisterService(&_RecommendationService_serviceDesc, srv)
}
func _RecommendationService_GetRecommendations_Handler(srv interface{}, ctx context.Context, buf []byte) (proto.Message, error) {
in := new(Product)
if err := proto.Unmarshal(buf, in); err != nil {
return nil, err
}
out, err := srv.(RecommendationServiceServer).GetRecommendations(ctx, in)
if err != nil {
return nil, err
}
return out, nil
}
var _RecommendationService_serviceDesc = grpc.ServiceDesc{
ServiceName: "protos.RecommendationService",
HandlerType: (*RecommendationServiceServer)(nil),
Methods: []grpc.MethodDesc{
{
MethodName: "GetRecommendations",
Handler: _RecommendationService_GetRecommendations_Handler,
},
},
Streams: []grpc.StreamDesc{},
}
For anyone running into the same problem, what I did was simply change how I built the proto files. There is a comment on the blog page that highlights some missing steps, I followed it and did the following protoc command to generate code from the proto files:
protoc --go_out=plugins=grpc:. *.proto
I ran this command in the directory with my proto files and then did a go build on my main.go file, now everything is working fine.
Basically your protoc-gen-go doesn't match the version of grpc. So sync them both to the latest version and reinstall protoc-gen-go will resolve the issue:
go get -u github.com/golang/protobuf/
cd github.com/golang/protobuf/
make
go get -u github.com/grpc/grpc-go
I am having the same issue and reinstalling or the new command doesn't seem to work.
However: If you change
codec grpc.Codec, buf []byte
in the Handler Definition into:
dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor
and
codec.Unmarshal(buf, in)
into
dec(in)
(All in the Handler Definition in your .pb.go file)
it seems to work.
Changing this file is of course not optimal and every time you recompile it will override your changes, but at least there is a workaround until I figure out what I messed up.