Add a ServeHTTP method to *grpc.Server

This adds new http.Handler-based ServerTransport in the process,
reusing the HTTP/2 server code in x/net/http2 or Go 1.6+.

All end2end tests pass with this new ServerTransport.

Fixes grpc#75

Also:
Updates grpc#495 (lets user fix it with middleware in front)
Updates grpc#468 (x/net/http2 validates)
Updates grpc#147 (possible with x/net/http2)
Updates grpc#104 (x/net/http2 does this)

rpc_util.go

@@ -273,7 +273,7 @@ func checkRecvPayload(pf payloadFormat, recvCompress string, dc Decompressor) er
 	case compressionNone:
 	case compressionMade:
 		if recvCompress == "" {
-			return transport.StreamErrorf(codes.InvalidArgument, "grpc: received unexpected payload format %d", pf)
+			return transport.StreamErrorf(codes.InvalidArgument, "grpc: invalid grpc-encoding %q with compression enabled", recvCompress)
 		}
 		if dc == nil || recvCompress != dc.Type() {
 			return transport.StreamErrorf(codes.InvalidArgument, "grpc: Decompressor is not installed for grpc-encoding %q", recvCompress)

server.go

@@ -39,13 +39,15 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/http"
 	"reflect"
 	"runtime"
 	"strings"
 	"sync"
 	"time"
 
 	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
 	"golang.org/x/net/trace"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
@@ -82,10 +84,11 @@ type service struct {
 
 // Server is a gRPC server to serve RPC requests.
 type Server struct {
-	opts   options
-	mu     sync.Mutex
+	opts options
+
+	mu     sync.Mutex // guards following
 	lis    map[net.Listener]bool
-	conns  map[transport.ServerTransport]bool
+	conns  map[io.Closer]bool
 	m      map[string]*service // service name -> service info
 	events trace.EventLog
 }
@@ -96,6 +99,7 @@ type options struct {
 	cp                   Compressor
 	dc                   Decompressor
 	maxConcurrentStreams uint32
+	useHandlerImpl       bool // use http.Handler-based server
 }
 
 // A ServerOption sets options.
@@ -149,7 +153,7 @@ func NewServer(opt ...ServerOption) *Server {
 	s := &Server{
 		lis:   make(map[net.Listener]bool),
 		opts:  opts,
-		conns: make(map[transport.ServerTransport]bool),
+		conns: make(map[io.Closer]bool),
 		m:     make(map[string]*service),
 	}
 	if EnableTracing {
@@ -216,9 +220,17 @@ var (
 	ErrServerStopped = errors.New("grpc: the server has been stopped")
 )
 
+func (s *Server) useTransportAuthenticator(rawConn net.Conn) (net.Conn, credentials.AuthInfo, error) {
+	creds, ok := s.opts.creds.(credentials.TransportAuthenticator)
+	if !ok {
+		return rawConn, nil, nil
+	}
+	return creds.ServerHandshake(rawConn)
+}
+
 // Serve accepts incoming connections on the listener lis, creating a new
 // ServerTransport and service goroutine for each. The service goroutines
-// read gRPC request and then call the registered handlers to reply to them.
+// read gRPC requests and then call the registered handlers to reply to them.
 // Service returns when lis.Accept fails.
 func (s *Server) Serve(lis net.Listener) error {
 	s.mu.Lock()
@@ -235,39 +247,54 @@ func (s *Server) Serve(lis net.Listener) error {
 		delete(s.lis, lis)
 		s.mu.Unlock()
 	}()
+	listenerAddr := lis.Addr()
 	for {
-		c, err := lis.Accept()
+		rawConn, err := lis.Accept()
 		if err != nil {
 			s.mu.Lock()
 			s.printf("done serving; Accept = %v", err)
 			s.mu.Unlock()
 			return err
 		}
-		var authInfo credentials.AuthInfo
-		if creds, ok := s.opts.creds.(credentials.TransportAuthenticator); ok {
-			var conn net.Conn
-			conn, authInfo, err = creds.ServerHandshake(c)
-			if err != nil {
-				s.mu.Lock()
-				s.errorf("ServerHandshake(%q) failed: %v", c.RemoteAddr(), err)
-				s.mu.Unlock()
-				grpclog.Println("grpc: Server.Serve failed to complete security handshake.")
-				continue
-			}
-			c = conn
-		}
+		// Start a new goroutine to deal with rawConn
+		// so we don't stall this Accept loop goroutine.
+		go s.handleRawConn(listenerAddr, rawConn)
+	}
+}
+
+// handleRawConn is run in its own goroutine and handles a just-accepted
+// connection that has not had any I/O performed on it yet.
+func (s *Server) handleRawConn(listenerAddr net.Addr, rawConn net.Conn) {
+	conn, authInfo, err := s.useTransportAuthenticator(rawConn)
+	if err != nil {
 		s.mu.Lock()
-		if s.conns == nil {
-			s.mu.Unlock()
-			c.Close()
-			return nil
-		}
+		s.errorf("ServerHandshake(%q) failed: %v", rawConn.RemoteAddr(), err)
 		s.mu.Unlock()
+		grpclog.Println("grpc: Server.Serve failed to complete security handshake.")
+		rawConn.Close()
+		return
+	}
 
-		go s.serveNewHTTP2Transport(c, authInfo)
+	s.mu.Lock()
+	if s.conns == nil {
+		s.mu.Unlock()
+		conn.Close()
+		return
+	}
+	s.mu.Unlock()
+
+	if s.opts.useHandlerImpl {
+		s.serveUsingHandler(listenerAddr, conn)
+	} else {
+		s.serveNewHTTP2Transport(conn, authInfo)
 	}
 }
 
+// serveNewHTTP2Transport sets up a new http/2 transport (using the
+// gRPC http2 server transport in transport/http2_server.go) and
+// serves streams on it.
+// This is run in its own goroutine (it does network I/O in
+// transport.NewServerTransport).
 func (s *Server) serveNewHTTP2Transport(c net.Conn, authInfo credentials.AuthInfo) {
 	st, err := transport.NewServerTransport("http2", c, s.opts.maxConcurrentStreams, authInfo)
 	if err != nil {
@@ -299,6 +326,52 @@ func (s *Server) serveStreams(st transport.ServerTransport) {
 	wg.Wait()
 }
 
+var _ http.Handler = (*Server)(nil)
+
+// serveUsingHandler is the implementation of Serve(net.Listener) when
+// TestingUseHandlerImpl has been configured. This lets the end2end
+// tests exercise the ServeHTTP method as one of the environment types.
+//
+// conn is the *tls.Conn that's already been authenticated.
+func (s *Server) serveUsingHandler(listenerAddr net.Addr, conn net.Conn) {
+	if !s.addConn(conn) {
+		conn.Close()
+		return
+	}
+	defer s.removeConn(conn)
+	connDone := make(chan struct{})
+	hs := &http.Server{
+		Handler: s,
+		ConnState: func(c net.Conn, cs http.ConnState) {
+			if cs == http.StateClosed {
+				close(connDone)
+			}
+		},
+	}
+	if err := http2.ConfigureServer(hs, &http2.Server{
+		MaxConcurrentStreams: s.opts.maxConcurrentStreams,
+	}); err != nil {
+		grpclog.Fatalf("grpc: http2.ConfigureServer: %v", err)
+		return
+	}
+	hs.Serve(&singleConnListener{addr: listenerAddr, conn: conn})
+	<-connDone
+}
+
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	st, err := transport.NewServerHandlerTransport(w, r)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	if !s.addConn(st) {
+		st.Close()
+		return
+	}
+	defer s.removeConn(st)
+	s.serveStreams(st)
+}
+
 // traceInfo returns a traceInfo and associates it with stream, if tracing is enabled.
 // If tracing is not enabled, it returns nil.
 func (s *Server) traceInfo(st transport.ServerTransport, stream *transport.Stream) (trInfo *traceInfo) {
@@ -317,21 +390,21 @@ func (s *Server) traceInfo(st transport.ServerTransport, stream *transport.Strea
 	return trInfo
 }
 
-func (s *Server) addConn(st transport.ServerTransport) bool {
+func (s *Server) addConn(c io.Closer) bool {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	if s.conns == nil {
 		return false
 	}
-	s.conns[st] = true
+	s.conns[c] = true
 	return true
 }
 
-func (s *Server) removeConn(st transport.ServerTransport) {
+func (s *Server) removeConn(c io.Closer) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	if s.conns != nil {
-		delete(s.conns, st)
+		delete(s.conns, c)
 	}
 }
 
@@ -603,12 +676,14 @@ func (s *Server) Stop() {
 	cs := s.conns
 	s.conns = nil
 	s.mu.Unlock()
+
 	for lis := range listeners {
 		lis.Close()
 	}
 	for c := range cs {
 		c.Close()
 	}
+
 	s.mu.Lock()
 	if s.events != nil {
 		s.events.Finish()
@@ -618,16 +693,24 @@ func (s *Server) Stop() {
 }
 
 // TestingCloseConns closes all exiting transports but keeps s.lis accepting new
-// connections. This is for test only now.
+// connections.
+// This is only for tests and is subject to removal.
 func (s *Server) TestingCloseConns() {
 	s.mu.Lock()
 	for c := range s.conns {
 		c.Close()
+		delete(s.conns, c)
 	}
-	s.conns = make(map[transport.ServerTransport]bool)
 	s.mu.Unlock()
 }
 
+// TestingUseHandlerImpl enables the http.Handler-based server implementation.
+// It must be called before Serve and requires TLS credentials.
+// This is only for tests and is subject to removal.
+func (s *Server) TestingUseHandlerImpl() {
+	s.opts.useHandlerImpl = true
+}
+
 // SendHeader sends header metadata. It may be called at most once from a unary
 // RPC handler. The ctx is the RPC handler's Context or one derived from it.
 func SendHeader(ctx context.Context, md metadata.MD) error {
@@ -658,3 +741,30 @@ func SetTrailer(ctx context.Context, md metadata.MD) error {
 	}
 	return stream.SetTrailer(md)
 }
+
+// singleConnListener is a net.Listener that yields a single conn.
+type singleConnListener struct {
+	mu   sync.Mutex
+	addr net.Addr
+	conn net.Conn // nil if done
+}
+
+func (ln *singleConnListener) Addr() net.Addr { return ln.addr }
+
+func (ln *singleConnListener) Close() error {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+	ln.conn = nil
+	return nil
+}
+
+func (ln *singleConnListener) Accept() (net.Conn, error) {
+	ln.mu.Lock()
+	defer ln.mu.Unlock()
+	c := ln.conn
+	if c == nil {
+		return nil, io.EOF
+	}
+	ln.conn = nil
+	return c, nil
+}