add server reflection (flyteorg#34)

The same as flyteorg/datacatalog#19

With [server reflection](https://github.com/grpc/grpc-go/blob/master/Documentation/server-reflection-tutorial.md), it would be easier to interact with GRPC service using e.g. `grpcurl`.

flyteadmin does come with HTTP endpoint as well, but interacting with GRPC directly makes it more handy.

cmd/entrypoints/serve.go

@@ -33,6 +33,7 @@ import (
 	"github.com/lyft/flytestdlib/contextutils"
 	"github.com/lyft/flytestdlib/promutils/labeled"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/reflection"
 )
 
 // serveCmd represents the serve command
@@ -84,6 +85,9 @@ func newGRPCServer(ctx context.Context, cfg *config.ServerConfig, authContext in
 	grpcServer := grpc.NewServer(serverOpts...)
 	grpc_prometheus.Register(grpcServer)
 	flyteService.RegisterAdminServiceServer(grpcServer, adminservice.NewAdminServer(cfg.KubeConfig, cfg.Master))
+	if cfg.GrpcServerReflection {
+		reflection.Register(grpcServer)
+	}
 	return grpcServer, nil
 }
 

flyteadmin_config.yaml

@@ -5,6 +5,7 @@
 server:
   httpPort: 8088
   grpcPort: 8089
+  grpcServerReflection: true
   security:
     secure: false
     ssl:

pkg/config/config.go

@@ -12,11 +12,12 @@ const SectionKey = "server"
 //go:generate pflags ServerConfig --default-var=defaultServerConfig
 
 type ServerConfig struct {
-	HTTPPort   int                   `json:"httpPort" pflag:",On which http port to serve admin"`
-	GrpcPort   int                   `json:"grpcPort" pflag:",On which grpc port to serve admin"`
-	KubeConfig string                `json:"kube-config" pflag:",Path to kubernetes client config file."`
-	Master     string                `json:"master" pflag:",The address of the Kubernetes API server."`
-	Security   ServerSecurityOptions `json:"security"`
+	HTTPPort             int                   `json:"httpPort" pflag:",On which http port to serve admin"`
+	GrpcPort             int                   `json:"grpcPort" pflag:",On which grpc port to serve admin"`
+	GrpcServerReflection bool                  `json:"grpcServerReflection" pflag:",Enable GRPC Server Reflection"`
+	KubeConfig           string                `json:"kube-config" pflag:",Path to kubernetes client config file."`
+	Master               string                `json:"master" pflag:",The address of the Kubernetes API server."`
+	Security             ServerSecurityOptions `json:"security"`
 }
 
 type ServerSecurityOptions struct {