vendor updates

vendor/google.golang.org/grpc/metadata/metadata.go

@@ -17,7 +17,8 @@
  */
 
 // Package metadata define the structure of the metadata supported by gRPC library.
-// Please refer to https://grpc.io/docs/guides/wire.html for more information about custom-metadata.
+// Please refer to https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
+// for more information about custom-metadata.
 package metadata // import "google.golang.org/grpc/metadata"
 
 import (
@@ -115,9 +116,22 @@ func NewIncomingContext(ctx context.Context, md MD) context.Context {
 	return context.WithValue(ctx, mdIncomingKey{}, md)
 }
 
-// NewOutgoingContext creates a new context with outgoing md attached.
+// NewOutgoingContext creates a new context with outgoing md attached. If used
+// in conjunction with AppendToOutgoingContext, NewOutgoingContext will
+// overwrite any previously-appended metadata.
 func NewOutgoingContext(ctx context.Context, md MD) context.Context {
-	return context.WithValue(ctx, mdOutgoingKey{}, md)
+	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md})
+}
+
+// AppendToOutgoingContext returns a new context with the provided kv merged
+// with any existing metadata in the context. Please refer to the
+// documentation of Pairs for a description of kv.
+func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context {
+	if len(kv)%2 == 1 {
+		panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
+	}
+	md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)
+	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md, added: append(md.added, kv)})
 }
 
 // FromIncomingContext returns the incoming metadata in ctx if it exists.  The
@@ -128,10 +142,39 @@ func FromIncomingContext(ctx context.Context) (md MD, ok bool) {
 	return
 }
 
+// FromOutgoingContextRaw returns the un-merged, intermediary contents
+// of rawMD. Remember to perform strings.ToLower on the keys. The returned
+// MD should not be modified. Writing to it may cause races. Modification
+// should be made to copies of the returned MD.
+//
+// This is intended for gRPC-internal use ONLY.
+func FromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
+	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
+	if !ok {
+		return nil, nil, false
+	}
+
+	return raw.md, raw.added, true
+}
+
 // FromOutgoingContext returns the outgoing metadata in ctx if it exists.  The
 // returned MD should not be modified. Writing to it may cause races.
 // Modification should be made to the copies of the returned MD.
-func FromOutgoingContext(ctx context.Context) (md MD, ok bool) {
-	md, ok = ctx.Value(mdOutgoingKey{}).(MD)
-	return
+func FromOutgoingContext(ctx context.Context) (MD, bool) {
+	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
+	if !ok {
+		return nil, false
+	}
+
+	mds := make([]MD, 0, len(raw.added)+1)
+	mds = append(mds, raw.md)
+	for _, vv := range raw.added {
+		mds = append(mds, Pairs(vv...))
+	}
+	return Join(mds...), ok
+}
+
+type rawMD struct {
+	md    MD
+	added [][]string
 }

vendor/google.golang.org/grpc/metadata/metadata_test.go

@@ -21,6 +21,8 @@ package metadata
 import (
 	"reflect"
 	"testing"
+
+	"golang.org/x/net/context"
 )
 
 func TestPairsMD(t *testing.T) {
@@ -69,3 +71,55 @@ func TestJoin(t *testing.T) {
 		}
 	}
 }
+
+func TestAppendToOutgoingContext(t *testing.T) {
+	// Pre-existing metadata
+	ctx := NewOutgoingContext(context.Background(), Pairs("k1", "v1", "k2", "v2"))
+	ctx = AppendToOutgoingContext(ctx, "k1", "v3")
+	ctx = AppendToOutgoingContext(ctx, "k1", "v4")
+	md, ok := FromOutgoingContext(ctx)
+	if !ok {
+		t.Errorf("Expected MD to exist in ctx, but got none")
+	}
+	want := Pairs("k1", "v1", "k1", "v3", "k1", "v4", "k2", "v2")
+	if !reflect.DeepEqual(md, want) {
+		t.Errorf("context's metadata is %v, want %v", md, want)
+	}
+
+	// No existing metadata
+	ctx = AppendToOutgoingContext(context.Background(), "k1", "v1")
+	md, ok = FromOutgoingContext(ctx)
+	if !ok {
+		t.Errorf("Expected MD to exist in ctx, but got none")
+	}
+	want = Pairs("k1", "v1")
+	if !reflect.DeepEqual(md, want) {
+		t.Errorf("context's metadata is %v, want %v", md, want)
+	}
+}
+
+// Old/slow approach to adding metadata to context
+func Benchmark_AddingMetadata_ContextManipulationApproach(b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		ctx := context.Background()
+		md, _ := FromOutgoingContext(ctx)
+		NewOutgoingContext(ctx, Join(Pairs("k1", "v1", "k2", "v2"), md))
+	}
+}
+
+// Newer/faster approach to adding metadata to context
+func BenchmarkAppendToOutgoingContext(b *testing.B) {
+	for n := 0; n < b.N; n++ {
+		AppendToOutgoingContext(context.Background(), "k1", "v1", "k2", "v2")
+	}
+}
+
+func BenchmarkFromOutgoingContext(b *testing.B) {
+	ctx := context.Background()
+	ctx = NewOutgoingContext(ctx, MD{"k3": {"v3", "v4"}})
+	ctx = AppendToOutgoingContext(ctx, "k1", "v1", "k2", "v2")
+
+	for n := 0; n < b.N; n++ {
+		FromOutgoingContext(ctx)
+	}
+}