some minor fixes

grpclb/grpclb.go

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2014, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -37,12 +37,12 @@
 package grpclb
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials"
 	lbpb "google.golang.org/grpc/grpclb/grpc_lb_v1"
 	"google.golang.org/grpc/grpclog"
 	"google.golang.org/grpc/naming"
@@ -172,7 +172,70 @@ func (b *balancer) processServerList(l *lbpb.ServerList) {
 	return
 }
 
-func (b *balancer) init(target string, creds credentials.TransportCredentials) error {
+func (b *balancer) callRemoteBalancer(lbc lbpb.LoadBalancerClient) (retry bool) {
+	b.mu.Lock()
+	if b.done {
+		b.mu.Unlock()
+		return
+	}
+	b.mu.Unlock()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	stream, err := lbc.BalanceLoad(ctx, grpc.FailFast(false))
+	if err != nil {
+		grpclog.Printf("Failed to perform RPC to the remote balancer %v", err)
+		return
+	}
+	initReq := &lbpb.LoadBalanceRequest{
+		LoadBalanceRequestType: &lbpb.LoadBalanceRequest_InitialRequest{
+			InitialRequest: new(lbpb.InitialLoadBalanceRequest),
+		},
+	}
+	if err := stream.Send(initReq); err != nil {
+		// TODO: backoff on retry?
+		return true
+	}
+	reply, err := stream.Recv()
+	if err != nil {
+		// TODO: backoff on retry?
+		return true
+	}
+	initResp := reply.GetInitialResponse()
+	if initResp == nil {
+		grpclog.Println("Failed to receive the initial response from the remote balancer.")
+		return
+	}
+	// TODO: Support delegation.
+	if initResp.LoadBalancerDelegate != "" {
+		// delegation
+		grpclog.Println("TODO: Delegation is not supported yet.")
+		return
+	}
+	// Retrieve the server list.
+	for {
+		reply, err := stream.Recv()
+		if err != nil {
+			break
+		}
+		if serverList := reply.GetServerList(); serverList != nil {
+			b.processServerList(serverList)
+		}
+	}
+	return true
+}
+
+func (b *balancer) Start(target string, config grpc.BalancerConfig) error {
+	// TODO: Fall back to the basic direct connection if there is no name resolver.
+	if b.r == nil {
+		return errors.New("there is no name resolver installed")
+	}
+	b.mu.Lock()
+	if b.done {
+		b.mu.Unlock()
+		return grpc.ErrClientConnClosing
+	}
+	b.addrCh = make(chan []grpc.Address)
+	b.mu.Unlock()
 	w, err := b.r.Resolve(target)
 	if err != nil {
 		return err
@@ -205,6 +268,7 @@ func (b *balancer) init(target string, creds credentials.TransportCredentials) e
 			//
 			// TODO: override the server name in creds using Metadata in addr.
 			var err error
+			creds := config.DialCreds
 			if creds == nil {
 				cc, err = grpc.Dial(rb.addr.Addr, grpc.WithBlock(), grpc.WithInsecure())
 			} else {
@@ -217,56 +281,9 @@ func (b *balancer) init(target string, creds credentials.TransportCredentials) e
 			lbc := lbpb.NewLoadBalancerClient(cc)
 			go func() {
 				for {
-					b.mu.Lock()
+					if retry := b.callRemoteBalancer(lbc); !retry {
-					if b.done {
-						b.mu.Unlock()
 						return
 					}
-					b.mu.Unlock()
-					ctx, cancel := context.WithCancel(context.Background())
-					defer cancel()
-					stream, err := lbc.BalanceLoad(ctx, grpc.FailFast(false))
-					if err != nil {
-						grpclog.Printf("Failed to perform RPC to the remote balancer %v", err)
-						return
-					}
-					initReq := &lbpb.LoadBalanceRequest{
-						LoadBalanceRequestType: &lbpb.LoadBalanceRequest_InitialRequest{
-							InitialRequest: new(lbpb.InitialLoadBalanceRequest),
-						},
-					}
-					if err := stream.Send(initReq); err != nil {
-						cancel()
-						// TODO: backoff on retry?
-						continue
-					}
-					reply, err := stream.Recv()
-					if err != nil {
-						cancel()
-						// TODO: backoff on retry?
-						continue
-					}
-					initResp := reply.GetInitialResponse()
-					if initResp == nil {
-						grpclog.Println("Failed to receive the initial response from the remote balancer.")
-						return
-					}
-					// TODO: Support delegation.
-					if initResp.LoadBalancerDelegate != "" {
-						// delegation
-						grpclog.Println("TODO: Delegation is not supported yet.")
-						return
-					}
-					// Retrieve the server list.
-					for {
-						reply, err := stream.Recv()
-						if err != nil {
-							break
-						}
-						if serverList := reply.GetServerList(); serverList != nil {
-							b.processServerList(serverList)
-						}
-					}
 				}
 			}()
 		}
@@ -274,20 +291,6 @@ func (b *balancer) init(target string, creds credentials.TransportCredentials) e
 	return nil
 }
 
-func (b *balancer) Start(target string, config grpc.BalancerConfig) error {
-	b.mu.Lock()
-	if b.done {
-		b.mu.Unlock()
-		return grpc.ErrClientConnClosing
-	}
-	b.addrCh = make(chan []grpc.Address)
-	b.mu.Unlock()
-	if err := b.init(target, config.DialCreds); err != nil {
-		return err
-	}
-	return nil
-}
-
 func (b *balancer) down(addr grpc.Address, err error) {
 	b.mu.Lock()
 	defer b.mu.Unlock()