gRPC gateway init (#7019)

* WIP: grpc server setup

* add register grpc routes

* updated go mod

* updated grpc for all modules

* added pb file for grpc gateway

* udpated gw file

* added a test for grpc route

* fixed conflicts

* added grpc server

* grpc tests added

* cleanup

* Fix gateway forward issue

* Add godoc

* updated tests

* fix lint

* fix tests

* fix tests

* fix tests

* fixed test

* Add grpc headers

* Fix error handling

* Fix tests - hacky

* Fix lint

* remove debug logs

* Fix review comments

* move grpc tests into a separate file

* Fix protobuf version

* Update x/capability/module.go

* Fix godoc

* Fix review suggestions

* Fix codec

* Add query params test for gateway request

* Fix gofmt

Co-authored-by: anilCSE <anil@vitwit.com>
Co-authored-by: Federico Kunze <31522760+fedekunze@users.noreply.github.com>

server/api/server.go

@@ -7,8 +7,10 @@ import (
 	"strings"
 	"time"
 
+	"github.com/gogo/gateway"
 	"github.com/gorilla/handlers"
 	"github.com/gorilla/mux"
+	"github.com/grpc-ecosystem/grpc-gateway/runtime"
 	"github.com/rakyll/statik/fs"
 	"github.com/tendermint/tendermint/libs/log"
 	tmrpcserver "github.com/tendermint/tendermint/rpc/jsonrpc/server"
@@ -16,6 +18,7 @@ import (
 	"github.com/cosmos/cosmos-sdk/client"
 	"github.com/cosmos/cosmos-sdk/server/config"
 	"github.com/cosmos/cosmos-sdk/telemetry"
+	grpctypes "github.com/cosmos/cosmos-sdk/types/grpc"
 	"github.com/cosmos/cosmos-sdk/types/rest"
 
 	// unnamed import of statik for swagger UI support
@@ -24,19 +27,54 @@ import (
 
 // Server defines the server's API interface.
 type Server struct {
-	Router    *mux.Router
-	ClientCtx client.Context
+	Router     *mux.Router
+	GRPCRouter *runtime.ServeMux
+	ClientCtx  client.Context
 
 	logger   log.Logger
 	metrics  *telemetry.Metrics
 	listener net.Listener
 }
 
+// CustomGRPCHeaderMatcher for mapping request headers to
+// GRPC metadata.
+// HTTP headers that start with 'Grpc-Metadata-' are automatically mapped to
+// gRPC metadata after removing prefix 'Grpc-Metadata-'. We can use this
+// CustomGRPCHeaderMatcher if headers don't start with `Grpc-Metadata-`
+func CustomGRPCHeaderMatcher(key string) (string, bool) {
+	switch strings.ToLower(key) {
+	case grpctypes.GRPCBlockHeightHeader:
+		return grpctypes.GRPCBlockHeightHeader, true
+	default:
+		return runtime.DefaultHeaderMatcher(key)
+	}
+}
+
 func New(clientCtx client.Context, logger log.Logger) *Server {
+	// The default JSON marshaller used by the gRPC-Gateway is unable to marshal non-nullable non-scalar fields.
+	// Using the gogo/gateway package with the gRPC-Gateway WithMarshaler option fixes the scalar field marshalling issue.
+	marshalerOption := &gateway.JSONPb{
+		EmitDefaults: true,
+		Indent:       "  ",
+		OrigName:     true,
+	}
+
 	return &Server{
 		Router:    mux.NewRouter(),
 		ClientCtx: clientCtx,
 		logger:    logger,
+		GRPCRouter: runtime.NewServeMux(
+			// Custom marshaler option is required for gogo proto
+			runtime.WithMarshalerOption(runtime.MIMEWildcard, marshalerOption),
+
+			// This is necessary to get error details properly
+			// marshalled in unary requests.
+			runtime.WithProtoErrorHandler(runtime.DefaultHTTPProtoErrorHandler),
+
+			// Custom header matcher for mapping request headers to
+			// GRPC metadata
+			runtime.WithIncomingHeaderMatcher(CustomGRPCHeaderMatcher),
+		),
 	}
 }
 
@@ -70,6 +108,7 @@ func (s *Server) Start(cfg config.Config) error {
 		return err
 	}
 
+	s.registerGRPCRoutes()
 	s.listener = listener
 	var h http.Handler = s.Router
 
@@ -93,7 +132,11 @@ func (s *Server) registerSwaggerUI() {
 	}
 
 	staticServer := http.FileServer(statikFS)
-	s.Router.PathPrefix("/").Handler(staticServer)
+	s.Router.PathPrefix("/legacy").Handler(staticServer)
+}
+
+func (s *Server) registerGRPCRoutes() {
+	s.Router.PathPrefix("/").Handler(s.GRPCRouter)
 }
 
 func (s *Server) registerMetrics() {