credentials: add RequestInfo to context passed to GetRequestMetadata

credentials/credentials.go

@@ -34,6 +34,7 @@ import (
 
 	"github.com/golang/protobuf/proto"
 	"google.golang.org/grpc/credentials/internal"
+	ginternal "google.golang.org/grpc/internal"
 )
 
 // PerRPCCredentials defines the common interface for the credentials which need to
@@ -45,7 +46,8 @@ type PerRPCCredentials interface {
 	// context. If a status code is returned, it will be used as the status
 	// for the RPC. uri is the URI of the entry point for the request.
 	// When supported by the underlying implementation, ctx can be used for
-	// timeout and cancellation.
+	// timeout and cancellation. Additionally, RequestInfo data will be
+	// available via ctx to this call.
 	// TODO(zhaoq): Define the set of the qualified keys instead of leaving
 	// it as an arbitrary string.
 	GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error)
@@ -334,3 +336,31 @@ func cloneTLSConfig(cfg *tls.Config) *tls.Config {
 
 	return cfg.Clone()
 }
+
+// RequestInfo contains request data attached to the context passed to GetRequestMetadata calls.
+//
+// This API is experimental.
+type RequestInfo struct {
+	// The method passed to Invoke or NewStream for this RPC. (For proto methods, this has the format "/some.Service/Method")
+	Method string
+}
+
+// requestInfoKey is a struct to be used as the key when attaching a RequestInfo to a context object.
+type requestInfoKey struct{}
+
+// RequestInfoFromContext extracts the RequestInfo from the context.
+//
+// This API is experimental.
+func RequestInfoFromContext(ctx context.Context) RequestInfo {
+	ri, ok := ctx.Value(requestInfoKey{}).(RequestInfo)
+	if !ok {
+		return RequestInfo{}
+	}
+	return ri
+}
+
+func init() {
+	ginternal.NewRequestInfoContext = func(ctx context.Context, ri RequestInfo) context.Context {
+		return context.WithValue(ctx, requestInfoKey{}, ri)
+	}
+}

internal/internal.go

@@ -47,6 +47,9 @@ var (
 	// call to proto.Clone(). The returned Status proto should not be mutated by
 	// the caller.
 	StatusRawProto interface{} // func (*status.Status) *spb.Status
+	// NewRequestInfoContext creates a new context based on the argument context attaching
+	// the passed in RequestInfo to the new context.
+	NewRequestInfoContext interface{} // func(context.Context, credentials.RequestInfo) context.Context
 )
 
 // HealthChecker defines the signature of the client-side LB channel health checking function.

internal/transport/http2_client.go

@@ -35,6 +35,7 @@ import (
 
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/internal"
 	"google.golang.org/grpc/internal/channelz"
 	"google.golang.org/grpc/internal/syscall"
 	"google.golang.org/grpc/keepalive"
@@ -397,11 +398,15 @@ func (t *http2Client) getPeer() *peer.Peer {
 
 func (t *http2Client) createHeaderFields(ctx context.Context, callHdr *CallHdr) ([]hpack.HeaderField, error) {
 	aud := t.createAudience(callHdr)
-	authData, err := t.getTrAuthData(ctx, aud)
+	ri := credentials.RequestInfo{
+		Method: callHdr.Method,
+	}
+	ctxWithRequestInfo := internal.NewRequestInfoContext.(func(context.Context, credentials.RequestInfo) context.Context)(ctx, ri)
+	authData, err := t.getTrAuthData(ctxWithRequestInfo, aud)
 	if err != nil {
 		return nil, err
 	}
-	callAuthData, err := t.getCallAuthData(ctx, aud, callHdr)
+	callAuthData, err := t.getCallAuthData(ctxWithRequestInfo, aud, callHdr)
 	if err != nil {
 		return nil, err
 	}

test/end2end_test.go

@@ -7484,3 +7484,30 @@ func parseCfg(s string) serviceconfig.Config {
 	}
 	return c
 }
+
+type methodTestCreds struct{}
+
+func (m methodTestCreds) GetRequestMetadata(ctx context.Context, uri ...string) (map[string]string, error) {
+	ri := credentials.RequestInfoFromContext(ctx)
+	return nil, status.Errorf(codes.Unknown, ri.Method)
+}
+
+func (m methodTestCreds) RequireTransportSecurity() bool {
+	return false
+}
+
+func (s) TestGRPCMethodAccessibleToCredsViaContextRequestInfo(t *testing.T) {
+	const wantMethod = "/grpc.testing.TestService/EmptyCall"
+	ss := &stubServer{}
+	if err := ss.Start(nil, grpc.WithPerRPCCredentials(methodTestCreds{})); err != nil {
+		t.Fatalf("Error starting endpoint server: %v", err)
+	}
+	defer ss.Stop()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+
+	if _, err := ss.client.EmptyCall(ctx, &testpb.Empty{}); status.Convert(err).Message() != wantMethod {
+		t.Fatalf("ss.client.EmptyCall(_, _) = _, %v; want _, _.Message()=%q", err, wantMethod)
+	}
+}