separate reflection descriptor from established conn

core/grpcox.go

@@ -7,12 +7,9 @@ import (
 	"time"
 
 	"github.com/fullstorydev/grpcurl"
-	"github.com/jhump/protoreflect/grpcreflect"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/keepalive"
-	"google.golang.org/grpc/metadata"
-	reflectpb "google.golang.org/grpc/reflection/grpc_reflection_v1alpha"
 )
 
 // GrpCox - main object
@@ -71,15 +68,12 @@ func (g *GrpCox) GetResource(ctx context.Context, target string, plainText, isRe
 	var err error
 	r := new(Resource)
 	h := append(g.headers, g.reflectHeaders...)
-	md := grpcurl.MetadataFromHeaders(h)
+	r.md = grpcurl.MetadataFromHeaders(h)
-	refCtx := metadata.NewOutgoingContext(ctx, md)
 	r.clientConn, err = g.dial(ctx, target, plainText)
 	if err != nil {
 		return nil, err
 	}
 
-	r.refClient = grpcreflect.NewClient(refCtx, reflectpb.NewServerReflectionClient(r.clientConn))
-	r.descSource = grpcurl.DescriptorSourceFromServer(ctx, r.refClient)
 	r.headers = h
 
 	g.activeConn.addConnection(target, r, g.maxLifeConn)

core/resource.go

@@ -14,6 +14,8 @@ import (
 	"github.com/jhump/protoreflect/grpcreflect"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	reflectpb "google.golang.org/grpc/reflection/grpc_reflection_v1alpha"
 )
 
 // Resource - hold 3 main function (List, Describe, and Invoke)
@@ -23,12 +25,42 @@ type Resource struct {
 	refClient  *grpcreflect.Client
 
 	headers []string
+	md      metadata.MD
+}
+
+//openDescriptor - use it to reflect server descriptor
+func (r *Resource) openDescriptor() {
+	ctx := context.Background()
+	refCtx := metadata.NewOutgoingContext(ctx, r.md)
+	r.refClient = grpcreflect.NewClient(refCtx, reflectpb.NewServerReflectionClient(r.clientConn))
+	r.descSource = grpcurl.DescriptorSourceFromServer(ctx, r.refClient)
+}
+
+//closeDescriptor - please ensure to always close after open in the same flow
+func (r *Resource) closeDescriptor() {
+	done := make(chan int)
+	go func() {
+		if r.refClient != nil {
+			r.refClient.Reset()
+		}
+		done <- 1
+	}()
+
+	select {
+	case <-done:
+		return
+	case <-time.After(3 * time.Second):
+		log.Printf("Reflection %s falied to close\n", r.clientConn.Target())
+		return
+	}
 }
 
 // List - To list all services exposed by a server
 // symbol can be "" to list all available services
 // symbol also can be service name to list all available method
 func (r *Resource) List(symbol string) ([]string, error) {
+	r.openDescriptor()
+	defer r.closeDescriptor()
 
 	var result []string
 	if symbol == "" {
@@ -65,6 +97,8 @@ func (r *Resource) List(symbol string) ([]string, error) {
 // It also prints a description of that symbol, in the form of snippets of proto source.
 // It won't necessarily be the original source that defined the element, but it will be equivalent.
 func (r *Resource) Describe(symbol string) (string, string, error) {
+	r.openDescriptor()
+	defer r.closeDescriptor()
 
 	var result, template string
 
@@ -119,6 +153,9 @@ func (r *Resource) Describe(symbol string) (string, string, error) {
 
 // Invoke - invoking gRPC function
 func (r *Resource) Invoke(ctx context.Context, symbol string, in io.Reader) (string, time.Duration, error) {
+	r.openDescriptor()
+	defer r.closeDescriptor()
+
 	// because of grpcurl directly fmt.Printf on their invoke function
 	// so we stub the Stdout using os.Pipe
 	backUpStdout := os.Stdout
@@ -167,10 +204,6 @@ func (r *Resource) Invoke(ctx context.Context, symbol string, in io.Reader) (str
 func (r *Resource) Close() {
 	done := make(chan int)
 	go func() {
-		if r.refClient != nil {
-			r.refClient.Reset()
-			r.refClient = nil
-		}
 		if r.clientConn != nil {
 			r.clientConn.Close()
 			r.clientConn = nil