transport: Pass Header metadata to tap handle. (#6652)

Author: pstibrany

Diff for: internal/transport/http2_server.go

@@ -566,7 +566,7 @@ func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(
 	}
 	if t.inTapHandle != nil {
 		var err error
-		if s.ctx, err = t.inTapHandle(s.ctx, &tap.Info{FullMethodName: s.method}); err != nil {
+		if s.ctx, err = t.inTapHandle(s.ctx, &tap.Info{FullMethodName: s.method, Header: mdata}); err != nil {
 			t.mu.Unlock()
 			if t.logger.V(logLevel) {
 				t.logger.Infof("Aborting the stream early due to InTapHandle failure: %v", err)

Diff for: tap/tap.go

@@ -27,13 +27,19 @@ package tap
 
 import (
 	"context"
+
+	"google.golang.org/grpc/metadata"
 )
 
 // Info defines the relevant information needed by the handles.
 type Info struct {
 	// FullMethodName is the string of grpc method (in the format of
 	// /package.service/method).
 	FullMethodName string
+
+	// Header contains the header metadata received.
+	Header metadata.MD
+
 	// TODO: More to be added.
 }
 

Diff for: test/end2end_test.go

@@ -2099,6 +2099,10 @@ func (t *myTap) handle(ctx context.Context, info *tap.Info) (context.Context, er
 		switch info.FullMethodName {
 		case "/grpc.testing.TestService/EmptyCall":
 			t.cnt++
+
+			if vals := info.Header.Get("return-error"); len(vals) > 0 && vals[0] == "true" {
+				return nil, status.Errorf(codes.Unknown, "tap error")
+			}
 		case "/grpc.testing.TestService/UnaryCall":
 			return nil, fmt.Errorf("tap error")
 		case "/grpc.testing.TestService/FullDuplexCall":
@@ -2120,13 +2124,28 @@ func testTap(t *testing.T, e env) {
 	tc := testgrpc.NewTestServiceClient(cc)
 	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
 	defer cancel()
+
 	if _, err := tc.EmptyCall(ctx, &testpb.Empty{}); err != nil {
 		t.Fatalf("TestService/EmptyCall(_, _) = _, %v, want _, <nil>", err)
 	}
 	if ttap.cnt != 1 {
 		t.Fatalf("Get the count in ttap %d, want 1", ttap.cnt)
 	}
 
+	if _, err := tc.EmptyCall(metadata.AppendToOutgoingContext(ctx, "return-error", "false"), &testpb.Empty{}); err != nil {
+		t.Fatalf("TestService/EmptyCall(_, _) = _, %v, want _, <nil>", err)
+	}
+	if ttap.cnt != 2 {
+		t.Fatalf("Get the count in ttap %d, want 2", ttap.cnt)
+	}
+
+	if _, err := tc.EmptyCall(metadata.AppendToOutgoingContext(ctx, "return-error", "true"), &testpb.Empty{}); status.Code(err) != codes.Unknown {
+		t.Fatalf("TestService/EmptyCall(_, _) = _, %v, want _, %s", err, codes.Unknown)
+	}
+	if ttap.cnt != 3 {
+		t.Fatalf("Get the count in ttap %d, want 3", ttap.cnt)
+	}
+
 	payload, err := newPayload(testpb.PayloadType_COMPRESSABLE, 31)
 	if err != nil {
 		t.Fatal(err)