balancer: remove Header from PickOptions; it is also available through context (#2674)

balancer/balancer.go

@@ -171,9 +171,6 @@ type PickOptions struct {
 	// FullMethodName is the method name that NewClientStream() is called
 	// with. The canonical format is /service/Method.
 	FullMethodName string
-	// Header contains the metadata from the RPC's client header.  The metadata
-	// should not be modified; make a copy first if needed.
-	Header metadata.MD
 }
 
 // DoneInfo contains additional information for done.

clientconn.go

@@ -42,7 +42,6 @@ import (
 	"google.golang.org/grpc/internal/grpcsync"
 	"google.golang.org/grpc/internal/transport"
 	"google.golang.org/grpc/keepalive"
-	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/resolver"
 	_ "google.golang.org/grpc/resolver/dns"         // To register dns resolver.
 	_ "google.golang.org/grpc/resolver/passthrough" // To register passthrough resolver.
@@ -747,10 +746,8 @@ func (cc *ClientConn) healthCheckConfig() *healthCheckConfig {
 }
 
 func (cc *ClientConn) getTransport(ctx context.Context, failfast bool, method string) (transport.ClientTransport, func(balancer.DoneInfo), error) {
-	hdr, _ := metadata.FromOutgoingContext(ctx)
 	t, done, err := cc.blockingpicker.pick(ctx, failfast, balancer.PickOptions{
 		FullMethodName: method,
-		Header:         hdr,
 	})
 	if err != nil {
 		return nil, nil, toRPCErr(err)

test/balancer_test.go

@@ -29,7 +29,6 @@ import (
 	"google.golang.org/grpc/connectivity"
 	"google.golang.org/grpc/credentials"
 	"google.golang.org/grpc/grpclog"
-	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/resolver"
 	testpb "google.golang.org/grpc/test/grpc_testing"
 	"google.golang.org/grpc/testdata"
@@ -46,7 +45,6 @@ type testBalancer struct {
 	sc balancer.SubConn
 
 	newSubConnOptions balancer.NewSubConnOptions
-	pickOptions       []balancer.PickOptions
 	doneInfo          []balancer.DoneInfo
 }
 
@@ -103,7 +101,6 @@ type picker struct {
 }
 
 func (p *picker) Pick(ctx context.Context, opts balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
-	p.bal.pickOptions = append(p.bal.pickOptions, opts)
 	if p.err != nil {
 		return nil, nil, p.err
 	}
@@ -138,13 +135,13 @@ func (s) TestCredsBundleFromBalancer(t *testing.T) {
 	}
 }
 
-func (s) TestPickAndDone(t *testing.T) {
+func (s) TestDoneInfo(t *testing.T) {
 	for _, e := range listTestEnv() {
-		testPickAndDone(t, e)
+		testDoneInfo(t, e)
 	}
 }
 
-func testPickAndDone(t *testing.T, e env) {
+func testDoneInfo(t *testing.T, e env) {
 	te := newTest(t, e)
 	b := &testBalancer{}
 	balancer.Register(b)
@@ -164,20 +161,10 @@ func testPickAndDone(t *testing.T, e env) {
 	if _, err := tc.EmptyCall(ctx, &testpb.Empty{}); !reflect.DeepEqual(err, wantErr) {
 		t.Fatalf("TestService/EmptyCall(_, _) = _, %v, want _, %v", err, wantErr)
 	}
-	md := metadata.Pairs("testMDKey", "testMDVal")
-	ctx = metadata.NewOutgoingContext(ctx, md)
 	if _, err := tc.UnaryCall(ctx, &testpb.SimpleRequest{}); err != nil {
 		t.Fatalf("TestService.UnaryCall(%v, _, _, _) = _, %v; want _, <nil>", ctx, err)
 	}
 
-	poWant := []balancer.PickOptions{
-		{FullMethodName: "/grpc.testing.TestService/EmptyCall"},
-		{FullMethodName: "/grpc.testing.TestService/UnaryCall", Header: md},
-	}
-	if !reflect.DeepEqual(b.pickOptions, poWant) {
-		t.Fatalf("b.pickOptions = %v; want %v", b.pickOptions, poWant)
-	}
-
 	if len(b.doneInfo) < 1 || !reflect.DeepEqual(b.doneInfo[0].Err, wantErr) {
 		t.Fatalf("b.doneInfo = %v; want b.doneInfo[0].Err = %v", b.doneInfo, wantErr)
 	}