protoc-gen-go-http generates HTTP-wrappers for gRPC servers generated by protoc-gen-go. It is implemented as a protoc plugin.
A typical use case is when you started using gRPC but there is legacy services that still use HTTP/1.1. protoc-gen-go-http generates fast wrappers that can be used as handler functions.
Suppose you have a simple service:
syntax = "proto3";
service Example {
// Simple request/response.
rpc GetPerson(Query) returns (Person) {}
// Server streaming (ignored).
rpc ListPeople(Query) returns (stream Person) {}
}
protoc-gen-go will generate the following interface:
type ExampleServer interface {
// Simple request/response.
GetPerson(context.Context, *Query) (*Person, error)
// Server streaming (ignored).
ListPeople(*Query, Example_ListPeopleServer) error
}Then with protoc-gen-go-http you can get your HTTP handler functions:
type HTTPExampleServer struct {
srv ExampleServer
cdc codec.Codec
}
func NewHTTPExampleServer(srv ExampleServer, cdc codec.Codec) *HTTPExampleServer {
return &HTTPExampleServer{
srv: srv,
cdc: cdc,
}
}
func (wpr *HTTPExampleServer) GetPerson(w http.ResponseWriter, r *http.Request) {
defer r.Body.Close()
arg := Query{}
err := wpr.cdc.ReadRequest(r.Body, &arg)
if err != nil {
wpr.cdc.WriteError(w, err)
return
}
grpcResp, err := wpr.srv.GetPerson(r.Context(), &arg)
if err != nil {
wpr.cdc.WriteError(w, err)
return
}
wpr.cdc.WriteResponse(w, grpcResp)
}A codec.Codec is used to read requests and write responses/errors. You can use the codec.DefaultCodec or implement a custom one.
protoc-gen-go-http relies heavily on grpc-gateway code, but it's faster because less time is spent on marshalling/unmarshalling. grpc-gateway first unmarshals POST body, then marshals it into a protobuf blob, then unmarshals a protobuf response, etc. protoc-gen-go-http just unmarshals POST body into a "native" gRPC struct, gets response struct and marshals it.
All stream-based gRPC methods are ignored.
go get -u github.com/lazada/protoc-gen-go-http
Add --go-http_out=. as a parameter to protoc, for example:
protoc --go_out=plugins=grpc:. --go-http_out=. example.proto