add grpc-proxy (github.com/mwitkow/grpc-proxy)

Signed-off-by: Adphi <philippe.adrien.nousse@gmail.com>

proxy/examples_test.go

@@ -0,0 +1,70 @@
+// Copyright 2017 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package proxy_test
+
+import (
+	"context"
+	"log"
+	"strings"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/status"
+
+	"go.linka.cloud/grpc-toolkit/proxy"
+)
+
+var (
+	director proxy.StreamDirector
+)
+
+func ExampleNewProxy() {
+	dst, err := grpc.Dial("example.com")
+	if err != nil {
+		log.Fatalf("dialing example.org: %v", err)
+	}
+	proxy := proxy.NewProxy(dst)
+	_ = proxy
+}
+
+func ExampleRegisterService() {
+	// A gRPC server with the proxying codec enabled.
+	server := grpc.NewServer()
+	// Register a TestService with 4 of its methods explicitly.
+	proxy.RegisterService(server, director,
+		"mwitkow.testproto.TestService",
+		"PingEmpty", "Ping", "PingError", "PingList")
+}
+
+func ExampleTransparentHandler() {
+	grpc.NewServer(
+		grpc.UnknownServiceHandler(proxy.TransparentHandler(director)))
+}
+
+// Provides a simple example of a director that shields internal services and dials a staging or production backend.
+// This is a *very naive* implementation that creates a new connection on every request. Consider using pooling.
+func ExampleStreamDirector() {
+	director = func(ctx context.Context, fullMethodName string) (context.Context, grpc.ClientConnInterface, error) {
+		// Make sure we never forward internal services.
+		if strings.HasPrefix(fullMethodName, "/com.example.internal.") {
+			return nil, nil, status.Errorf(codes.Unimplemented, "Unknown method")
+		}
+		md, ok := metadata.FromIncomingContext(ctx)
+		// Copy the inbound metadata explicitly.
+		outCtx := metadata.NewOutgoingContext(ctx, md.Copy())
+		if ok {
+			// Decide on which backend to dial
+			if val, exists := md[":authority"]; exists && val[0] == "staging.api.example.com" {
+				// Make sure we use DialContext so the dialing can be cancelled/time out together with the context.
+				conn, err := grpc.DialContext(ctx, "api-service.staging.svc.local")
+				return outCtx, conn, err
+			} else if val, exists := md[":authority"]; exists && val[0] == "api.example.com" {
+				conn, err := grpc.DialContext(ctx, "api-service.prod.svc.local")
+				return outCtx, conn, err
+			}
+		}
+		return nil, nil, status.Errorf(codes.Unimplemented, "Unknown method")
+	}
+}