ARROW-17553: [Go] Enable flight.Server to register additional grpc se…

…rvices (apache#13995)

This PR exposes `grpc.ServiceRegistrar` and `reflection.ServiceInfoProvider` in `grpc.Server`. They are needed to register additional gRPC services such as health check and reflection.

Authored-by: Jie Zhang <[email protected]>
Signed-off-by: Matt Topol <[email protected]>

go/arrow/flight/flight_test.go

@@ -31,6 +31,9 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials/insecure"
+	"google.golang.org/grpc/health"
+	"google.golang.org/grpc/health/grpc_health_v1"
+	"google.golang.org/grpc/reflection"
 	"google.golang.org/grpc/status"
 )
 
@@ -308,6 +311,44 @@ func TestServer(t *testing.T) {
 	}
 }
 
+func TestServerWithAdditionalServices(t *testing.T) {
+	f := &flightServer{}
+	f.SetAuthHandler(&servAuth{})
+
+	s := flight.NewFlightServer()
+	s.Init("localhost:0")
+	s.RegisterFlightService(f)
+
+	// Enable health check.
+	grpc_health_v1.RegisterHealthServer(s, health.NewServer())
+
+	// Enable reflection for grpcurl.
+	reflection.Register(s)
+
+	go s.Serve()
+	defer s.Shutdown()
+
+	// Flight client should not be affected by the additional services.
+	flightClient, err := flight.NewFlightClient(s.Addr().String(), &clientAuth{}, grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		t.Error(err)
+	}
+	defer flightClient.Close()
+
+	// Make sure health check is working.
+	conn, err := grpc.Dial(s.Addr().String(), grpc.WithTransportCredentials(insecure.NewCredentials()))
+	if err != nil {
+		t.Error(err)
+	}
+	defer conn.Close()
+
+	healthClient := grpc_health_v1.NewHealthClient(conn)
+	_, err = healthClient.Check(context.Background(), &grpc_health_v1.HealthCheckRequest{})
+	if err != nil {
+		t.Error(err)
+	}
+}
+
 type flightMetadataWriterServer struct {
 	flight.BaseFlightServer
 }

go/arrow/flight/server.go

@@ -17,13 +17,14 @@
 package flight
 
 import (
-	context "context"
+	"context"
 	"net"
 	"os"
 	"os/signal"
 
 	"github.com/apache/arrow/go/v10/arrow/flight/internal/flight"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/reflection"
 )
 
 type (
@@ -79,6 +80,12 @@ type Server interface {
 	// RegisterFlightService sets up the handler for the Flight Endpoints as per
 	// normal Grpc setups
 	RegisterFlightService(FlightServer)
+	// ServiceRegistrar wraps a single method that supports service registration.
+	// For example, it may be used to register health check provided by grpc-go.
+	grpc.ServiceRegistrar
+	// ServiceInfoProvider is an interface used to retrieve metadata about the services to expose.
+	// If reflection is enabled on the server, all the endpoints can be invoked using grpcurl.
+	reflection.ServiceInfoProvider
 }
 
 // BaseFlightServer is the base flight server implementation and must be
@@ -250,3 +257,11 @@ func (s *server) RegisterFlightService(svc FlightServer) {
 func (s *server) Shutdown() {
 	s.server.GracefulStop()
 }
+
+func (s *server) RegisterService(sd *grpc.ServiceDesc, ss interface{}) {
+	s.server.RegisterService(sd, ss)
+}
+
+func (s *server) GetServiceInfo() map[string]grpc.ServiceInfo {
+	return s.server.GetServiceInfo()
+}