Merge pull request #17 from nsheridan/vendor

update dependencies

6 files changed, 3234 insertions, 0 deletions

diff --git a/vendor/google.golang.org/grpc/transport/control.go b/vendor/google.golang.org/grpc/transport/control.go
new file mode 100644
index 0000000..7e9bdf3
--- /dev/null
+++ b/vendor/google.golang.org/grpc/transport/control.go
@@ -0,0 +1,210 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package transport
+
+import (
+	"fmt"
+	"sync"
+
+	"golang.org/x/net/http2"
+)
+
+const (
+	// The default value of flow control window size in HTTP2 spec.
+	defaultWindowSize = 65535
+	// The initial window size for flow control.
+	initialWindowSize     = defaultWindowSize      // for an RPC
+	initialConnWindowSize = defaultWindowSize * 16 // for a connection
+)
+
+// The following defines various control items which could flow through
+// the control buffer of transport. They represent different aspects of
+// control tasks, e.g., flow control, settings, streaming resetting, etc.
+type windowUpdate struct {
+	streamID  uint32
+	increment uint32
+}
+
+func (*windowUpdate) item() {}
+
+type settings struct {
+	ack bool
+	ss  []http2.Setting
+}
+
+func (*settings) item() {}
+
+type resetStream struct {
+	streamID uint32
+	code     http2.ErrCode
+}
+
+func (*resetStream) item() {}
+
+type flushIO struct {
+}
+
+func (*flushIO) item() {}
+
+type ping struct {
+	ack  bool
+	data [8]byte
+}
+
+func (*ping) item() {}
+
+// quotaPool is a pool which accumulates the quota and sends it to acquire()
+// when it is available.
+type quotaPool struct {
+	c chan int
+
+	mu    sync.Mutex
+	quota int
+}
+
+// newQuotaPool creates a quotaPool which has quota q available to consume.
+func newQuotaPool(q int) *quotaPool {
+	qb := &quotaPool{
+		c: make(chan int, 1),
+	}
+	if q > 0 {
+		qb.c <- q
+	} else {
+		qb.quota = q
+	}
+	return qb
+}
+
+// add adds n to the available quota and tries to send it on acquire.
+func (qb *quotaPool) add(n int) {
+	qb.mu.Lock()
+	defer qb.mu.Unlock()
+	qb.quota += n
+	if qb.quota <= 0 {
+		return
+	}
+	select {
+	case qb.c <- qb.quota:
+		qb.quota = 0
+	default:
+	}
+}
+
+// cancel cancels the pending quota sent on acquire, if any.
+func (qb *quotaPool) cancel() {
+	qb.mu.Lock()
+	defer qb.mu.Unlock()
+	select {
+	case n := <-qb.c:
+		qb.quota += n
+	default:
+	}
+}
+
+// reset cancels the pending quota sent on acquired, incremented by v and sends
+// it back on acquire.
+func (qb *quotaPool) reset(v int) {
+	qb.mu.Lock()
+	defer qb.mu.Unlock()
+	select {
+	case n := <-qb.c:
+		qb.quota += n
+	default:
+	}
+	qb.quota += v
+	if qb.quota <= 0 {
+		return
+	}
+	select {
+	case qb.c <- qb.quota:
+		qb.quota = 0
+	default:
+	}
+}
+
+// acquire returns the channel on which available quota amounts are sent.
+func (qb *quotaPool) acquire() <-chan int {
+	return qb.c
+}
+
+// inFlow deals with inbound flow control
+type inFlow struct {
+	// The inbound flow control limit for pending data.
+	limit uint32
+
+	mu sync.Mutex
+	// pendingData is the overall data which have been received but not been
+	// consumed by applications.
+	pendingData uint32
+	// The amount of data the application has consumed but grpc has not sent
+	// window update for them. Used to reduce window update frequency.
+	pendingUpdate uint32
+}
+
+// onData is invoked when some data frame is received. It updates pendingData.
+func (f *inFlow) onData(n uint32) error {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	f.pendingData += n
+	if f.pendingData+f.pendingUpdate > f.limit {
+		return fmt.Errorf("received %d-bytes data exceeding the limit %d bytes", f.pendingData+f.pendingUpdate, f.limit)
+	}
+	return nil
+}
+
+// onRead is invoked when the application reads the data. It returns the window size
+// to be sent to the peer.
+func (f *inFlow) onRead(n uint32) uint32 {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if f.pendingData == 0 {
+		return 0
+	}
+	f.pendingData -= n
+	f.pendingUpdate += n
+	if f.pendingUpdate >= f.limit/4 {
+		wu := f.pendingUpdate
+		f.pendingUpdate = 0
+		return wu
+	}
+	return 0
+}
+
+func (f *inFlow) resetPendingData() uint32 {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	n := f.pendingData
+	f.pendingData = 0
+	return n
+}
diff --git a/vendor/google.golang.org/grpc/transport/handler_server.go b/vendor/google.golang.org/grpc/transport/handler_server.go
new file mode 100644
index 0000000..7a4ae07
--- /dev/null
+++ b/vendor/google.golang.org/grpc/transport/handler_server.go
@@ -0,0 +1,393 @@
+/*
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+// This file is the implementation of a gRPC server using HTTP/2 which
+// uses the standard Go http2 Server implementation (via the
+// http.Handler interface), rather than speaking low-level HTTP/2
+// frames itself. It is the implementation of *grpc.Server.ServeHTTP.
+
+package transport
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+)
+
+// NewServerHandlerTransport returns a ServerTransport handling gRPC
+// from inside an http.Handler. It requires that the http Server
+// supports HTTP/2.
+func NewServerHandlerTransport(w http.ResponseWriter, r *http.Request) (ServerTransport, error) {
+	if r.ProtoMajor != 2 {
+		return nil, errors.New("gRPC requires HTTP/2")
+	}
+	if r.Method != "POST" {
+		return nil, errors.New("invalid gRPC request method")
+	}
+	if !strings.Contains(r.Header.Get("Content-Type"), "application/grpc") {
+		return nil, errors.New("invalid gRPC request content-type")
+	}
+	if _, ok := w.(http.Flusher); !ok {
+		return nil, errors.New("gRPC requires a ResponseWriter supporting http.Flusher")
+	}
+	if _, ok := w.(http.CloseNotifier); !ok {
+		return nil, errors.New("gRPC requires a ResponseWriter supporting http.CloseNotifier")
+	}
+
+	st := &serverHandlerTransport{
+		rw:       w,
+		req:      r,
+		closedCh: make(chan struct{}),
+		writes:   make(chan func()),
+	}
+
+	if v := r.Header.Get("grpc-timeout"); v != "" {
+		to, err := timeoutDecode(v)
+		if err != nil {
+			return nil, StreamErrorf(codes.Internal, "malformed time-out: %v", err)
+		}
+		st.timeoutSet = true
+		st.timeout = to
+	}
+
+	var metakv []string
+	if r.Host != "" {
+		metakv = append(metakv, ":authority", r.Host)
+	}
+	for k, vv := range r.Header {
+		k = strings.ToLower(k)
+		if isReservedHeader(k) && !isWhitelistedPseudoHeader(k){
+			continue
+		}
+		for _, v := range vv {
+			if k == "user-agent" {
+				// user-agent is special. Copying logic of http_util.go.
+				if i := strings.LastIndex(v, " "); i == -1 {
+					// There is no application user agent string being set
+					continue
+				} else {
+					v = v[:i]
+				}
+			}
+			metakv = append(metakv, k, v)
+		}
+	}
+	st.headerMD = metadata.Pairs(metakv...)
+
+	return st, nil
+}
+
+// serverHandlerTransport is an implementation of ServerTransport
+// which replies to exactly one gRPC request (exactly one HTTP request),
+// using the net/http.Handler interface. This http.Handler is guaranteed
+// at this point to be speaking over HTTP/2, so it's able to speak valid
+// gRPC.
+type serverHandlerTransport struct {
+	rw               http.ResponseWriter
+	req              *http.Request
+	timeoutSet       bool
+	timeout          time.Duration
+	didCommonHeaders bool
+
+	headerMD metadata.MD
+
+	closeOnce sync.Once
+	closedCh  chan struct{} // closed on Close
+
+	// writes is a channel of code to run serialized in the
+	// ServeHTTP (HandleStreams) goroutine. The channel is closed
+	// when WriteStatus is called.
+	writes chan func()
+}
+
+func (ht *serverHandlerTransport) Close() error {
+	ht.closeOnce.Do(ht.closeCloseChanOnce)
+	return nil
+}
+
+func (ht *serverHandlerTransport) closeCloseChanOnce() { close(ht.closedCh) }
+
+func (ht *serverHandlerTransport) RemoteAddr() net.Addr { return strAddr(ht.req.RemoteAddr) }
+
+// strAddr is a net.Addr backed by either a TCP "ip:port" string, or
+// the empty string if unknown.
+type strAddr string
+
+func (a strAddr) Network() string {
+	if a != "" {
+		// Per the documentation on net/http.Request.RemoteAddr, if this is
+		// set, it's set to the IP:port of the peer (hence, TCP):
+		// https://golang.org/pkg/net/http/#Request
+		//
+		// If we want to support Unix sockets later, we can
+		// add our own grpc-specific convention within the
+		// grpc codebase to set RemoteAddr to a different
+		// format, or probably better: we can attach it to the
+		// context and use that from serverHandlerTransport.RemoteAddr.
+		return "tcp"
+	}
+	return ""
+}
+
+func (a strAddr) String() string { return string(a) }
+
+// do runs fn in the ServeHTTP goroutine.
+func (ht *serverHandlerTransport) do(fn func()) error {
+	select {
+	case ht.writes <- fn:
+		return nil
+	case <-ht.closedCh:
+		return ErrConnClosing
+	}
+}
+
+func (ht *serverHandlerTransport) WriteStatus(s *Stream, statusCode codes.Code, statusDesc string) error {
+	err := ht.do(func() {
+		ht.writeCommonHeaders(s)
+
+		// And flush, in case no header or body has been sent yet.
+		// This forces a separation of headers and trailers if this is the
+		// first call (for example, in end2end tests's TestNoService).
+		ht.rw.(http.Flusher).Flush()
+
+		h := ht.rw.Header()
+		h.Set("Grpc-Status", fmt.Sprintf("%d", statusCode))
+		if statusDesc != "" {
+			h.Set("Grpc-Message", statusDesc)
+		}
+		if md := s.Trailer(); len(md) > 0 {
+			for k, vv := range md {
+				// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+				if isReservedHeader(k) {
+					continue
+				}
+				for _, v := range vv {
+					// http2 ResponseWriter mechanism to
+					// send undeclared Trailers after the
+					// headers have possibly been written.
+					h.Add(http2.TrailerPrefix+k, v)
+				}
+			}
+		}
+	})
+	close(ht.writes)
+	return err
+}
+
+// writeCommonHeaders sets common headers on the first write
+// call (Write, WriteHeader, or WriteStatus).
+func (ht *serverHandlerTransport) writeCommonHeaders(s *Stream) {
+	if ht.didCommonHeaders {
+		return
+	}
+	ht.didCommonHeaders = true
+
+	h := ht.rw.Header()
+	h["Date"] = nil // suppress Date to make tests happy; TODO: restore
+	h.Set("Content-Type", "application/grpc")
+
+	// Predeclare trailers we'll set later in WriteStatus (after the body).
+	// This is a SHOULD in the HTTP RFC, and the way you add (known)
+	// Trailers per the net/http.ResponseWriter contract.
+	// See https://golang.org/pkg/net/http/#ResponseWriter
+	// and https://golang.org/pkg/net/http/#example_ResponseWriter_trailers
+	h.Add("Trailer", "Grpc-Status")
+	h.Add("Trailer", "Grpc-Message")
+
+	if s.sendCompress != "" {
+		h.Set("Grpc-Encoding", s.sendCompress)
+	}
+}
+
+func (ht *serverHandlerTransport) Write(s *Stream, data []byte, opts *Options) error {
+	return ht.do(func() {
+		ht.writeCommonHeaders(s)
+		ht.rw.Write(data)
+		if !opts.Delay {
+			ht.rw.(http.Flusher).Flush()
+		}
+	})
+}
+
+func (ht *serverHandlerTransport) WriteHeader(s *Stream, md metadata.MD) error {
+	return ht.do(func() {
+		ht.writeCommonHeaders(s)
+		h := ht.rw.Header()
+		for k, vv := range md {
+			// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+			if isReservedHeader(k) {
+				continue
+			}
+			for _, v := range vv {
+				h.Add(k, v)
+			}
+		}
+		ht.rw.WriteHeader(200)
+		ht.rw.(http.Flusher).Flush()
+	})
+}
+
+func (ht *serverHandlerTransport) HandleStreams(startStream func(*Stream)) {
+	// With this transport type there will be exactly 1 stream: this HTTP request.
+
+	var ctx context.Context
+	var cancel context.CancelFunc
+	if ht.timeoutSet {
+		ctx, cancel = context.WithTimeout(context.Background(), ht.timeout)
+	} else {
+		ctx, cancel = context.WithCancel(context.Background())
+	}
+
+	// requestOver is closed when either the request's context is done
+	// or the status has been written via WriteStatus.
+	requestOver := make(chan struct{})
+
+	// clientGone receives a single value if peer is gone, either
+	// because the underlying connection is dead or because the
+	// peer sends an http2 RST_STREAM.
+	clientGone := ht.rw.(http.CloseNotifier).CloseNotify()
+	go func() {
+		select {
+		case <-requestOver:
+			return
+		case <-ht.closedCh:
+		case <-clientGone:
+		}
+		cancel()
+	}()
+
+	req := ht.req
+
+	s := &Stream{
+		id:            0,            // irrelevant
+		windowHandler: func(int) {}, // nothing
+		cancel:        cancel,
+		buf:           newRecvBuffer(),
+		st:            ht,
+		method:        req.URL.Path,
+		recvCompress:  req.Header.Get("grpc-encoding"),
+	}
+	pr := &peer.Peer{
+		Addr: ht.RemoteAddr(),
+	}
+	if req.TLS != nil {
+		pr.AuthInfo = credentials.TLSInfo{*req.TLS}
+	}
+	ctx = metadata.NewContext(ctx, ht.headerMD)
+	ctx = peer.NewContext(ctx, pr)
+	s.ctx = newContextWithStream(ctx, s)
+	s.dec = &recvBufferReader{ctx: s.ctx, recv: s.buf}
+
+	// readerDone is closed when the Body.Read-ing goroutine exits.
+	readerDone := make(chan struct{})
+	go func() {
+		defer close(readerDone)
+
+		// TODO: minimize garbage, optimize recvBuffer code/ownership
+		const readSize = 8196
+		for buf := make([]byte, readSize); ; {
+			n, err := req.Body.Read(buf)
+			if n > 0 {
+				s.buf.put(&recvMsg{data: buf[:n:n]})
+				buf = buf[n:]
+			}
+			if err != nil {
+				s.buf.put(&recvMsg{err: mapRecvMsgError(err)})
+				return
+			}
+			if len(buf) == 0 {
+				buf = make([]byte, readSize)
+			}
+		}
+	}()
+
+	// startStream is provided by the *grpc.Server's serveStreams.
+	// It starts a goroutine serving s and exits immediately.
+	// The goroutine that is started is the one that then calls
+	// into ht, calling WriteHeader, Write, WriteStatus, Close, etc.
+	startStream(s)
+
+	ht.runStream()
+	close(requestOver)
+
+	// Wait for reading goroutine to finish.
+	req.Body.Close()
+	<-readerDone
+}
+
+func (ht *serverHandlerTransport) runStream() {
+	for {
+		select {
+		case fn, ok := <-ht.writes:
+			if !ok {
+				return
+			}
+			fn()
+		case <-ht.closedCh:
+			return
+		}
+	}
+}
+
+// mapRecvMsgError returns the non-nil err into the appropriate
+// error value as expected by callers of *grpc.parser.recvMsg.
+// In particular, in can only be:
+//   * io.EOF
+//   * io.ErrUnexpectedEOF
+//   * of type transport.ConnectionError
+//   * of type transport.StreamError
+func mapRecvMsgError(err error) error {
+	if err == io.EOF || err == io.ErrUnexpectedEOF {
+		return err
+	}
+	if se, ok := err.(http2.StreamError); ok {
+		if code, ok := http2ErrConvTab[se.Code]; ok {
+			return StreamError{
+				Code: code,
+				Desc: se.Error(),
+			}
+		}
+	}
+	return ConnectionError{Desc: err.Error()}
+}
diff --git a/vendor/google.golang.org/grpc/transport/http2_client.go b/vendor/google.golang.org/grpc/transport/http2_client.go
new file mode 100644
index 0000000..e624f8d
--- /dev/null
+++ b/vendor/google.golang.org/grpc/transport/http2_client.go
@@ -0,0 +1,953 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package transport
+
+import (
+	"bytes"
+	"io"
+	"math"
+	"net"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+)
+
+// http2Client implements the ClientTransport interface with HTTP2.
+type http2Client struct {
+	target    string // server name/addr
+	userAgent string
+	conn      net.Conn             // underlying communication channel
+	authInfo  credentials.AuthInfo // auth info about the connection
+	nextID    uint32               // the next stream ID to be used
+
+	// writableChan synchronizes write access to the transport.
+	// A writer acquires the write lock by sending a value on writableChan
+	// and releases it by receiving from writableChan.
+	writableChan chan int
+	// shutdownChan is closed when Close is called.
+	// Blocking operations should select on shutdownChan to avoid
+	// blocking forever after Close.
+	// TODO(zhaoq): Maybe have a channel context?
+	shutdownChan chan struct{}
+	// errorChan is closed to notify the I/O error to the caller.
+	errorChan chan struct{}
+
+	framer *framer
+	hBuf   *bytes.Buffer  // the buffer for HPACK encoding
+	hEnc   *hpack.Encoder // HPACK encoder
+
+	// controlBuf delivers all the control related tasks (e.g., window
+	// updates, reset streams, and various settings) to the controller.
+	controlBuf *recvBuffer
+	fc         *inFlow
+	// sendQuotaPool provides flow control to outbound message.
+	sendQuotaPool *quotaPool
+	// streamsQuota limits the max number of concurrent streams.
+	streamsQuota *quotaPool
+
+	// The scheme used: https if TLS is on, http otherwise.
+	scheme string
+
+	authCreds []credentials.Credentials
+
+	mu            sync.Mutex     // guard the following variables
+	state         transportState // the state of underlying connection
+	activeStreams map[uint32]*Stream
+	// The max number of concurrent streams
+	maxStreams int
+	// the per-stream outbound flow control window size set by the peer.
+	streamSendQuota uint32
+}
+
+// newHTTP2Client constructs a connected ClientTransport to addr based on HTTP2
+// and starts to receive messages on it. Non-nil error returns if construction
+// fails.
+func newHTTP2Client(addr string, opts *ConnectOptions) (_ ClientTransport, err error) {
+	if opts.Dialer == nil {
+		// Set the default Dialer.
+		opts.Dialer = func(addr string, timeout time.Duration) (net.Conn, error) {
+			return net.DialTimeout("tcp", addr, timeout)
+		}
+	}
+	scheme := "http"
+	startT := time.Now()
+	timeout := opts.Timeout
+	conn, connErr := opts.Dialer(addr, timeout)
+	if connErr != nil {
+		return nil, ConnectionErrorf("transport: %v", connErr)
+	}
+	var authInfo credentials.AuthInfo
+	for _, c := range opts.AuthOptions {
+		if ccreds, ok := c.(credentials.TransportAuthenticator); ok {
+			scheme = "https"
+			// TODO(zhaoq): Now the first TransportAuthenticator is used if there are
+			// multiple ones provided. Revisit this if it is not appropriate. Probably
+			// place the ClientTransport construction into a separate function to make
+			// things clear.
+			if timeout > 0 {
+				timeout -= time.Since(startT)
+			}
+			conn, authInfo, connErr = ccreds.ClientHandshake(addr, conn, timeout)
+			break
+		}
+	}
+	if connErr != nil {
+		return nil, ConnectionErrorf("transport: %v", connErr)
+	}
+	defer func() {
+		if err != nil {
+			conn.Close()
+		}
+	}()
+	ua := primaryUA
+	if opts.UserAgent != "" {
+		ua = opts.UserAgent + " " + ua
+	}
+	var buf bytes.Buffer
+	t := &http2Client{
+		target:    addr,
+		userAgent: ua,
+		conn:      conn,
+		authInfo:  authInfo,
+		// The client initiated stream id is odd starting from 1.
+		nextID:          1,
+		writableChan:    make(chan int, 1),
+		shutdownChan:    make(chan struct{}),
+		errorChan:       make(chan struct{}),
+		framer:          newFramer(conn),
+		hBuf:            &buf,
+		hEnc:            hpack.NewEncoder(&buf),
+		controlBuf:      newRecvBuffer(),
+		fc:              &inFlow{limit: initialConnWindowSize},
+		sendQuotaPool:   newQuotaPool(defaultWindowSize),
+		scheme:          scheme,
+		state:           reachable,
+		activeStreams:   make(map[uint32]*Stream),
+		authCreds:       opts.AuthOptions,
+		maxStreams:      math.MaxInt32,
+		streamSendQuota: defaultWindowSize,
+	}
+	// Start the reader goroutine for incoming message. Each transport has
+	// a dedicated goroutine which reads HTTP2 frame from network. Then it
+	// dispatches the frame to the corresponding stream entity.
+	go t.reader()
+	// Send connection preface to server.
+	n, err := t.conn.Write(clientPreface)
+	if err != nil {
+		t.Close()
+		return nil, ConnectionErrorf("transport: %v", err)
+	}
+	if n != len(clientPreface) {
+		t.Close()
+		return nil, ConnectionErrorf("transport: preface mismatch, wrote %d bytes; want %d", n, len(clientPreface))
+	}
+	if initialWindowSize != defaultWindowSize {
+		err = t.framer.writeSettings(true, http2.Setting{http2.SettingInitialWindowSize, uint32(initialWindowSize)})
+	} else {
+		err = t.framer.writeSettings(true)
+	}
+	if err != nil {
+		t.Close()
+		return nil, ConnectionErrorf("transport: %v", err)
+	}
+	// Adjust the connection flow control window if needed.
+	if delta := uint32(initialConnWindowSize - defaultWindowSize); delta > 0 {
+		if err := t.framer.writeWindowUpdate(true, 0, delta); err != nil {
+			t.Close()
+			return nil, ConnectionErrorf("transport: %v", err)
+		}
+	}
+	go t.controller()
+	t.writableChan <- 0
+	return t, nil
+}
+
+func (t *http2Client) newStream(ctx context.Context, callHdr *CallHdr) *Stream {
+	// TODO(zhaoq): Handle uint32 overflow of Stream.id.
+	s := &Stream{
+		id:            t.nextID,
+		method:        callHdr.Method,
+		sendCompress:  callHdr.SendCompress,
+		buf:           newRecvBuffer(),
+		fc:            &inFlow{limit: initialWindowSize},
+		sendQuotaPool: newQuotaPool(int(t.streamSendQuota)),
+		headerChan:    make(chan struct{}),
+	}
+	t.nextID += 2
+	s.windowHandler = func(n int) {
+		t.updateWindow(s, uint32(n))
+	}
+	// Make a stream be able to cancel the pending operations by itself.
+	s.ctx, s.cancel = context.WithCancel(ctx)
+	s.dec = &recvBufferReader{
+		ctx:  s.ctx,
+		recv: s.buf,
+	}
+	return s
+}
+
+// NewStream creates a stream and register it into the transport as "active"
+// streams.
+func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (_ *Stream, err error) {
+	// Record the timeout value on the context.
+	var timeout time.Duration
+	if dl, ok := ctx.Deadline(); ok {
+		timeout = dl.Sub(time.Now())
+	}
+	select {
+	case <-ctx.Done():
+		return nil, ContextErr(ctx.Err())
+	default:
+	}
+	pr := &peer.Peer{
+		Addr: t.conn.RemoteAddr(),
+	}
+	// Attach Auth info if there is any.
+	if t.authInfo != nil {
+		pr.AuthInfo = t.authInfo
+	}
+	ctx = peer.NewContext(ctx, pr)
+	authData := make(map[string]string)
+	for _, c := range t.authCreds {
+		// Construct URI required to get auth request metadata.
+		var port string
+		if pos := strings.LastIndex(t.target, ":"); pos != -1 {
+			// Omit port if it is the default one.
+			if t.target[pos+1:] != "443" {
+				port = ":" + t.target[pos+1:]
+			}
+		}
+		pos := strings.LastIndex(callHdr.Method, "/")
+		if pos == -1 {
+			return nil, StreamErrorf(codes.InvalidArgument, "transport: malformed method name: %q", callHdr.Method)
+		}
+		audience := "https://" + callHdr.Host + port + callHdr.Method[:pos]
+		data, err := c.GetRequestMetadata(ctx, audience)
+		if err != nil {
+			return nil, StreamErrorf(codes.InvalidArgument, "transport: %v", err)
+		}
+		for k, v := range data {
+			authData[k] = v
+		}
+	}
+	t.mu.Lock()
+	if t.activeStreams == nil {
+		t.mu.Unlock()
+		return nil, ErrConnClosing
+	}
+	if t.state != reachable {
+		t.mu.Unlock()
+		return nil, ErrConnClosing
+	}
+	checkStreamsQuota := t.streamsQuota != nil
+	t.mu.Unlock()
+	if checkStreamsQuota {
+		sq, err := wait(ctx, t.shutdownChan, t.streamsQuota.acquire())
+		if err != nil {
+			return nil, err
+		}
+		// Returns the quota balance back.
+		if sq > 1 {
+			t.streamsQuota.add(sq - 1)
+		}
+	}
+	if _, err := wait(ctx, t.shutdownChan, t.writableChan); err != nil {
+		// Return the quota back now because there is no stream returned to the caller.
+		if _, ok := err.(StreamError); ok && checkStreamsQuota {
+			t.streamsQuota.add(1)
+		}
+		return nil, err
+	}
+	t.mu.Lock()
+	if t.state != reachable {
+		t.mu.Unlock()
+		return nil, ErrConnClosing
+	}
+	s := t.newStream(ctx, callHdr)
+	t.activeStreams[s.id] = s
+
+	// This stream is not counted when applySetings(...) initialize t.streamsQuota.
+	// Reset t.streamsQuota to the right value.
+	var reset bool
+	if !checkStreamsQuota && t.streamsQuota != nil {
+		reset = true
+	}
+	t.mu.Unlock()
+	if reset {
+		t.streamsQuota.reset(-1)
+	}
+
+	// HPACK encodes various headers. Note that once WriteField(...) is
+	// called, the corresponding headers/continuation frame has to be sent
+	// because hpack.Encoder is stateful.
+	t.hBuf.Reset()
+	t.hEnc.WriteField(hpack.HeaderField{Name: ":method", Value: "POST"})
+	t.hEnc.WriteField(hpack.HeaderField{Name: ":scheme", Value: t.scheme})
+	t.hEnc.WriteField(hpack.HeaderField{Name: ":path", Value: callHdr.Method})
+	t.hEnc.WriteField(hpack.HeaderField{Name: ":authority", Value: callHdr.Host})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "user-agent", Value: t.userAgent})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "te", Value: "trailers"})
+
+	if callHdr.SendCompress != "" {
+		t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-encoding", Value: callHdr.SendCompress})
+	}
+	if timeout > 0 {
+		t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-timeout", Value: timeoutEncode(timeout)})
+	}
+	for k, v := range authData {
+		// Capital header names are illegal in HTTP/2.
+		k = strings.ToLower(k)
+		t.hEnc.WriteField(hpack.HeaderField{Name: k, Value: v})
+	}
+	var (
+		hasMD      bool
+		endHeaders bool
+	)
+	if md, ok := metadata.FromContext(ctx); ok {
+		hasMD = true
+		for k, v := range md {
+			// HTTP doesn't allow you to set pseudoheaders after non pseudoheaders were set.
+			if isReservedHeader(k) {
+				continue
+			}
+			for _, entry := range v {
+				t.hEnc.WriteField(hpack.HeaderField{Name: k, Value: entry})
+			}
+		}
+	}
+	first := true
+	// Sends the headers in a single batch even when they span multiple frames.
+	for !endHeaders {
+		size := t.hBuf.Len()
+		if size > http2MaxFrameLen {
+			size = http2MaxFrameLen
+		} else {
+			endHeaders = true
+		}
+		var flush bool
+		if endHeaders && (hasMD || callHdr.Flush) {
+			flush = true
+		}
+		if first {
+			// Sends a HeadersFrame to server to start a new stream.
+			p := http2.HeadersFrameParam{
+				StreamID:      s.id,
+				BlockFragment: t.hBuf.Next(size),
+				EndStream:     false,
+				EndHeaders:    endHeaders,
+			}
+			// Do a force flush for the buffered frames iff it is the last headers frame
+			// and there is header metadata to be sent. Otherwise, there is flushing until
+			// the corresponding data frame is written.
+			err = t.framer.writeHeaders(flush, p)
+			first = false
+		} else {
+			// Sends Continuation frames for the leftover headers.
+			err = t.framer.writeContinuation(flush, s.id, endHeaders, t.hBuf.Next(size))
+		}
+		if err != nil {
+			t.notifyError(err)
+			return nil, ConnectionErrorf("transport: %v", err)
+		}
+	}
+	t.writableChan <- 0
+	return s, nil
+}
+
+// CloseStream clears the footprint of a stream when the stream is not needed any more.
+// This must not be executed in reader's goroutine.
+func (t *http2Client) CloseStream(s *Stream, err error) {
+	var updateStreams bool
+	t.mu.Lock()
+	if t.activeStreams == nil {
+		t.mu.Unlock()
+		return
+	}
+	if t.streamsQuota != nil {
+		updateStreams = true
+	}
+	if t.state == draining && len(t.activeStreams) == 1 {
+		// The transport is draining and s is the last live stream on t.
+		t.mu.Unlock()
+		t.Close()
+		return
+	}
+	delete(t.activeStreams, s.id)
+	t.mu.Unlock()
+	if updateStreams {
+		t.streamsQuota.add(1)
+	}
+	// In case stream sending and receiving are invoked in separate
+	// goroutines (e.g., bi-directional streaming), the caller needs
+	// to call cancel on the stream to interrupt the blocking on
+	// other goroutines.
+	s.cancel()
+	s.mu.Lock()
+	if q := s.fc.resetPendingData(); q > 0 {
+		if n := t.fc.onRead(q); n > 0 {
+			t.controlBuf.put(&windowUpdate{0, n})
+		}
+	}
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return
+	}
+	if !s.headerDone {
+		close(s.headerChan)
+		s.headerDone = true
+	}
+	s.state = streamDone
+	s.mu.Unlock()
+	if _, ok := err.(StreamError); ok {
+		t.controlBuf.put(&resetStream{s.id, http2.ErrCodeCancel})
+	}
+}
+
+// Close kicks off the shutdown process of the transport. This should be called
+// only once on a transport. Once it is called, the transport should not be
+// accessed any more.
+func (t *http2Client) Close() (err error) {
+	t.mu.Lock()
+	if t.state == reachable {
+		close(t.errorChan)
+	}
+	if t.state == closing {
+		t.mu.Unlock()
+		return
+	}
+	t.state = closing
+	t.mu.Unlock()
+	close(t.shutdownChan)
+	err = t.conn.Close()
+	t.mu.Lock()
+	streams := t.activeStreams
+	t.activeStreams = nil
+	t.mu.Unlock()
+	// Notify all active streams.
+	for _, s := range streams {
+		s.mu.Lock()
+		if !s.headerDone {
+			close(s.headerChan)
+			s.headerDone = true
+		}
+		s.mu.Unlock()
+		s.write(recvMsg{err: ErrConnClosing})
+	}
+	return
+}
+
+func (t *http2Client) GracefulClose() error {
+	t.mu.Lock()
+	if t.state == closing {
+		t.mu.Unlock()
+		return nil
+	}
+	if t.state == draining {
+		t.mu.Unlock()
+		return nil
+	}
+	t.state = draining
+	active := len(t.activeStreams)
+	t.mu.Unlock()
+	if active == 0 {
+		return t.Close()
+	}
+	return nil
+}
+
+// Write formats the data into HTTP2 data frame(s) and sends it out. The caller
+// should proceed only if Write returns nil.
+// TODO(zhaoq): opts.Delay is ignored in this implementation. Support it later
+// if it improves the performance.
+func (t *http2Client) Write(s *Stream, data []byte, opts *Options) error {
+	r := bytes.NewBuffer(data)
+	for {
+		var p []byte
+		if r.Len() > 0 {
+			size := http2MaxFrameLen
+			s.sendQuotaPool.add(0)
+			// Wait until the stream has some quota to send the data.
+			sq, err := wait(s.ctx, t.shutdownChan, s.sendQuotaPool.acquire())
+			if err != nil {
+				return err
+			}
+			t.sendQuotaPool.add(0)
+			// Wait until the transport has some quota to send the data.
+			tq, err := wait(s.ctx, t.shutdownChan, t.sendQuotaPool.acquire())
+			if err != nil {
+				if _, ok := err.(StreamError); ok {
+					t.sendQuotaPool.cancel()
+				}
+				return err
+			}
+			if sq < size {
+				size = sq
+			}
+			if tq < size {
+				size = tq
+			}
+			p = r.Next(size)
+			ps := len(p)
+			if ps < sq {
+				// Overbooked stream quota. Return it back.
+				s.sendQuotaPool.add(sq - ps)
+			}
+			if ps < tq {
+				// Overbooked transport quota. Return it back.
+				t.sendQuotaPool.add(tq - ps)
+			}
+		}
+		var (
+			endStream  bool
+			forceFlush bool
+		)
+		if opts.Last && r.Len() == 0 {
+			endStream = true
+		}
+		// Indicate there is a writer who is about to write a data frame.
+		t.framer.adjustNumWriters(1)
+		// Got some quota. Try to acquire writing privilege on the transport.
+		if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+			if _, ok := err.(StreamError); ok {
+				// Return the connection quota back.
+				t.sendQuotaPool.add(len(p))
+			}
+			if t.framer.adjustNumWriters(-1) == 0 {
+				// This writer is the last one in this batch and has the
+				// responsibility to flush the buffered frames. It queues
+				// a flush request to controlBuf instead of flushing directly
+				// in order to avoid the race with other writing or flushing.
+				t.controlBuf.put(&flushIO{})
+			}
+			return err
+		}
+		select {
+		case <-s.ctx.Done():
+			t.sendQuotaPool.add(len(p))
+			if t.framer.adjustNumWriters(-1) == 0 {
+				t.controlBuf.put(&flushIO{})
+			}
+			t.writableChan <- 0
+			return ContextErr(s.ctx.Err())
+		default:
+		}
+		if r.Len() == 0 && t.framer.adjustNumWriters(0) == 1 {
+			// Do a force flush iff this is last frame for the entire gRPC message
+			// and the caller is the only writer at this moment.
+			forceFlush = true
+		}
+		// If WriteData fails, all the pending streams will be handled
+		// by http2Client.Close(). No explicit CloseStream() needs to be
+		// invoked.
+		if err := t.framer.writeData(forceFlush, s.id, endStream, p); err != nil {
+			t.notifyError(err)
+			return ConnectionErrorf("transport: %v", err)
+		}
+		if t.framer.adjustNumWriters(-1) == 0 {
+			t.framer.flushWrite()
+		}
+		t.writableChan <- 0
+		if r.Len() == 0 {
+			break
+		}
+	}
+	if !opts.Last {
+		return nil
+	}
+	s.mu.Lock()
+	if s.state != streamDone {
+		if s.state == streamReadDone {
+			s.state = streamDone
+		} else {
+			s.state = streamWriteDone
+		}
+	}
+	s.mu.Unlock()
+	return nil
+}
+
+func (t *http2Client) getStream(f http2.Frame) (*Stream, bool) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	s, ok := t.activeStreams[f.Header().StreamID]
+	return s, ok
+}
+
+// updateWindow adjusts the inbound quota for the stream and the transport.
+// Window updates will deliver to the controller for sending when
+// the cumulative quota exceeds the corresponding threshold.
+func (t *http2Client) updateWindow(s *Stream, n uint32) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.state == streamDone {
+		return
+	}
+	if w := t.fc.onRead(n); w > 0 {
+		t.controlBuf.put(&windowUpdate{0, w})
+	}
+	if w := s.fc.onRead(n); w > 0 {
+		t.controlBuf.put(&windowUpdate{s.id, w})
+	}
+}
+
+func (t *http2Client) handleData(f *http2.DataFrame) {
+	size := len(f.Data())
+	if err := t.fc.onData(uint32(size)); err != nil {
+		t.notifyError(ConnectionErrorf("%v", err))
+		return
+	}
+	// Select the right stream to dispatch.
+	s, ok := t.getStream(f)
+	if !ok {
+		if w := t.fc.onRead(uint32(size)); w > 0 {
+			t.controlBuf.put(&windowUpdate{0, w})
+		}
+		return
+	}
+	if size > 0 {
+		s.mu.Lock()
+		if s.state == streamDone {
+			s.mu.Unlock()
+			// The stream has been closed. Release the corresponding quota.
+			if w := t.fc.onRead(uint32(size)); w > 0 {
+				t.controlBuf.put(&windowUpdate{0, w})
+			}
+			return
+		}
+		if err := s.fc.onData(uint32(size)); err != nil {
+			s.state = streamDone
+			s.statusCode = codes.Internal
+			s.statusDesc = err.Error()
+			s.mu.Unlock()
+			s.write(recvMsg{err: io.EOF})
+			t.controlBuf.put(&resetStream{s.id, http2.ErrCodeFlowControl})
+			return
+		}
+		s.mu.Unlock()
+		// TODO(bradfitz, zhaoq): A copy is required here because there is no
+		// guarantee f.Data() is consumed before the arrival of next frame.
+		// Can this copy be eliminated?
+		data := make([]byte, size)
+		copy(data, f.Data())
+		s.write(recvMsg{data: data})
+	}
+	// The server has closed the stream without sending trailers.  Record that
+	// the read direction is closed, and set the status appropriately.
+	if f.FrameHeader.Flags.Has(http2.FlagDataEndStream) {
+		s.mu.Lock()
+		if s.state == streamWriteDone {
+			s.state = streamDone
+		} else {
+			s.state = streamReadDone
+		}
+		s.statusCode = codes.Internal
+		s.statusDesc = "server closed the stream without sending trailers"
+		s.mu.Unlock()
+		s.write(recvMsg{err: io.EOF})
+	}
+}
+
+func (t *http2Client) handleRSTStream(f *http2.RSTStreamFrame) {
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	s.mu.Lock()
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return
+	}
+	s.state = streamDone
+	if !s.headerDone {
+		close(s.headerChan)
+		s.headerDone = true
+	}
+	s.statusCode, ok = http2ErrConvTab[http2.ErrCode(f.ErrCode)]
+	if !ok {
+		grpclog.Println("transport: http2Client.handleRSTStream found no mapped gRPC status for the received http2 error ", f.ErrCode)
+		s.statusCode = codes.Unknown
+	}
+	s.mu.Unlock()
+	s.write(recvMsg{err: io.EOF})
+}
+
+func (t *http2Client) handleSettings(f *http2.SettingsFrame) {
+	if f.IsAck() {
+		return
+	}
+	var ss []http2.Setting
+	f.ForeachSetting(func(s http2.Setting) error {
+		ss = append(ss, s)
+		return nil
+	})
+	// The settings will be applied once the ack is sent.
+	t.controlBuf.put(&settings{ack: true, ss: ss})
+}
+
+func (t *http2Client) handlePing(f *http2.PingFrame) {
+	pingAck := &ping{ack: true}
+	copy(pingAck.data[:], f.Data[:])
+	t.controlBuf.put(pingAck)
+}
+
+func (t *http2Client) handleGoAway(f *http2.GoAwayFrame) {
+	// TODO(zhaoq): GoAwayFrame handler to be implemented
+}
+
+func (t *http2Client) handleWindowUpdate(f *http2.WindowUpdateFrame) {
+	id := f.Header().StreamID
+	incr := f.Increment
+	if id == 0 {
+		t.sendQuotaPool.add(int(incr))
+		return
+	}
+	if s, ok := t.getStream(f); ok {
+		s.sendQuotaPool.add(int(incr))
+	}
+}
+
+// operateHeaders takes action on the decoded headers.
+func (t *http2Client) operateHeaders(frame *http2.MetaHeadersFrame) {
+	s, ok := t.getStream(frame)
+	if !ok {
+		return
+	}
+	var state decodeState
+	for _, hf := range frame.Fields {
+		state.processHeaderField(hf)
+	}
+	if state.err != nil {
+		s.write(recvMsg{err: state.err})
+		// Something wrong. Stops reading even when there is remaining.
+		return
+	}
+
+	endStream := frame.StreamEnded()
+
+	s.mu.Lock()
+	if !endStream {
+		s.recvCompress = state.encoding
+	}
+	if !s.headerDone {
+		if !endStream && len(state.mdata) > 0 {
+			s.header = state.mdata
+		}
+		close(s.headerChan)
+		s.headerDone = true
+	}
+	if !endStream || s.state == streamDone {
+		s.mu.Unlock()
+		return
+	}
+
+	if len(state.mdata) > 0 {
+		s.trailer = state.mdata
+	}
+	s.state = streamDone
+	s.statusCode = state.statusCode
+	s.statusDesc = state.statusDesc
+	s.mu.Unlock()
+
+	s.write(recvMsg{err: io.EOF})
+}
+
+func handleMalformedHTTP2(s *Stream, err error) {
+	s.mu.Lock()
+	if !s.headerDone {
+		close(s.headerChan)
+		s.headerDone = true
+	}
+	s.mu.Unlock()
+	s.write(recvMsg{err: err})
+}
+
+// reader runs as a separate goroutine in charge of reading data from network
+// connection.
+//
+// TODO(zhaoq): currently one reader per transport. Investigate whether this is
+// optimal.
+// TODO(zhaoq): Check the validity of the incoming frame sequence.
+func (t *http2Client) reader() {
+	// Check the validity of server preface.
+	frame, err := t.framer.readFrame()
+	if err != nil {
+		t.notifyError(err)
+		return
+	}
+	sf, ok := frame.(*http2.SettingsFrame)
+	if !ok {
+		t.notifyError(err)
+		return
+	}
+	t.handleSettings(sf)
+
+	// loop to keep reading incoming messages on this transport.
+	for {
+		frame, err := t.framer.readFrame()
+		if err != nil {
+			// Abort an active stream if the http2.Framer returns a
+			// http2.StreamError. This can happen only if the server's response
+			// is malformed http2.
+			if se, ok := err.(http2.StreamError); ok {
+				t.mu.Lock()
+				s := t.activeStreams[se.StreamID]
+				t.mu.Unlock()
+				if s != nil {
+					// use error detail to provide better err message
+					handleMalformedHTTP2(s, StreamErrorf(http2ErrConvTab[se.Code], "%v", t.framer.errorDetail()))
+				}
+				continue
+			} else {
+				// Transport error.
+				t.notifyError(err)
+				return
+			}
+		}
+		switch frame := frame.(type) {
+		case *http2.MetaHeadersFrame:
+			t.operateHeaders(frame)
+		case *http2.DataFrame:
+			t.handleData(frame)
+		case *http2.RSTStreamFrame:
+			t.handleRSTStream(frame)
+		case *http2.SettingsFrame:
+			t.handleSettings(frame)
+		case *http2.PingFrame:
+			t.handlePing(frame)
+		case *http2.GoAwayFrame:
+			t.handleGoAway(frame)
+		case *http2.WindowUpdateFrame:
+			t.handleWindowUpdate(frame)
+		default:
+			grpclog.Printf("transport: http2Client.reader got unhandled frame type %v.", frame)
+		}
+	}
+}
+
+func (t *http2Client) applySettings(ss []http2.Setting) {
+	for _, s := range ss {
+		switch s.ID {
+		case http2.SettingMaxConcurrentStreams:
+			// TODO(zhaoq): This is a hack to avoid significant refactoring of the
+			// code to deal with the unrealistic int32 overflow. Probably will try
+			// to find a better way to handle this later.
+			if s.Val > math.MaxInt32 {
+				s.Val = math.MaxInt32
+			}
+			t.mu.Lock()
+			reset := t.streamsQuota != nil
+			if !reset {
+				t.streamsQuota = newQuotaPool(int(s.Val) - len(t.activeStreams))
+			}
+			ms := t.maxStreams
+			t.maxStreams = int(s.Val)
+			t.mu.Unlock()
+			if reset {
+				t.streamsQuota.reset(int(s.Val) - ms)
+			}
+		case http2.SettingInitialWindowSize:
+			t.mu.Lock()
+			for _, stream := range t.activeStreams {
+				// Adjust the sending quota for each stream.
+				stream.sendQuotaPool.reset(int(s.Val - t.streamSendQuota))
+			}
+			t.streamSendQuota = s.Val
+			t.mu.Unlock()
+		}
+	}
+}
+
+// controller running in a separate goroutine takes charge of sending control
+// frames (e.g., window update, reset stream, setting, etc.) to the server.
+func (t *http2Client) controller() {
+	for {
+		select {
+		case i := <-t.controlBuf.get():
+			t.controlBuf.load()
+			select {
+			case <-t.writableChan:
+				switch i := i.(type) {
+				case *windowUpdate:
+					t.framer.writeWindowUpdate(true, i.streamID, i.increment)
+				case *settings:
+					if i.ack {
+						t.framer.writeSettingsAck(true)
+						t.applySettings(i.ss)
+					} else {
+						t.framer.writeSettings(true, i.ss...)
+					}
+				case *resetStream:
+					t.framer.writeRSTStream(true, i.streamID, i.code)
+				case *flushIO:
+					t.framer.flushWrite()
+				case *ping:
+					t.framer.writePing(true, i.ack, i.data)
+				default:
+					grpclog.Printf("transport: http2Client.controller got unexpected item type %v\n", i)
+				}
+				t.writableChan <- 0
+				continue
+			case <-t.shutdownChan:
+				return
+			}
+		case <-t.shutdownChan:
+			return
+		}
+	}
+}
+
+func (t *http2Client) Error() <-chan struct{} {
+	return t.errorChan
+}
+
+func (t *http2Client) notifyError(err error) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	// make sure t.errorChan is closed only once.
+	if t.state == reachable {
+		t.state = unreachable
+		close(t.errorChan)
+		grpclog.Printf("transport: http2Client.notifyError got notified that the client transport was broken %v.", err)
+	}
+}
diff --git a/vendor/google.golang.org/grpc/transport/http2_server.go b/vendor/google.golang.org/grpc/transport/http2_server.go
new file mode 100644
index 0000000..1c4d585
--- /dev/null
+++ b/vendor/google.golang.org/grpc/transport/http2_server.go
@@ -0,0 +1,743 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package transport
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"math"
+	"net"
+	"strconv"
+	"sync"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/metadata"
+	"google.golang.org/grpc/peer"
+)
+
+// ErrIllegalHeaderWrite indicates that setting header is illegal because of
+// the stream's state.
+var ErrIllegalHeaderWrite = errors.New("transport: the stream is done or WriteHeader was already called")
+
+// http2Server implements the ServerTransport interface with HTTP2.
+type http2Server struct {
+	conn        net.Conn
+	maxStreamID uint32               // max stream ID ever seen
+	authInfo    credentials.AuthInfo // auth info about the connection
+	// writableChan synchronizes write access to the transport.
+	// A writer acquires the write lock by receiving a value on writableChan
+	// and releases it by sending on writableChan.
+	writableChan chan int
+	// shutdownChan is closed when Close is called.
+	// Blocking operations should select on shutdownChan to avoid
+	// blocking forever after Close.
+	shutdownChan chan struct{}
+	framer       *framer
+	hBuf         *bytes.Buffer  // the buffer for HPACK encoding
+	hEnc         *hpack.Encoder // HPACK encoder
+
+	// The max number of concurrent streams.
+	maxStreams uint32
+	// controlBuf delivers all the control related tasks (e.g., window
+	// updates, reset streams, and various settings) to the controller.
+	controlBuf *recvBuffer
+	fc         *inFlow
+	// sendQuotaPool provides flow control to outbound message.
+	sendQuotaPool *quotaPool
+
+	mu            sync.Mutex // guard the following
+	state         transportState
+	activeStreams map[uint32]*Stream
+	// the per-stream outbound flow control window size set by the peer.
+	streamSendQuota uint32
+}
+
+// newHTTP2Server constructs a ServerTransport based on HTTP2. ConnectionError is
+// returned if something goes wrong.
+func newHTTP2Server(conn net.Conn, maxStreams uint32, authInfo credentials.AuthInfo) (_ ServerTransport, err error) {
+	framer := newFramer(conn)
+	// Send initial settings as connection preface to client.
+	var settings []http2.Setting
+	// TODO(zhaoq): Have a better way to signal "no limit" because 0 is
+	// permitted in the HTTP2 spec.
+	if maxStreams == 0 {
+		maxStreams = math.MaxUint32
+	} else {
+		settings = append(settings, http2.Setting{http2.SettingMaxConcurrentStreams, maxStreams})
+	}
+	if initialWindowSize != defaultWindowSize {
+		settings = append(settings, http2.Setting{http2.SettingInitialWindowSize, uint32(initialWindowSize)})
+	}
+	if err := framer.writeSettings(true, settings...); err != nil {
+		return nil, ConnectionErrorf("transport: %v", err)
+	}
+	// Adjust the connection flow control window if needed.
+	if delta := uint32(initialConnWindowSize - defaultWindowSize); delta > 0 {
+		if err := framer.writeWindowUpdate(true, 0, delta); err != nil {
+			return nil, ConnectionErrorf("transport: %v", err)
+		}
+	}
+	var buf bytes.Buffer
+	t := &http2Server{
+		conn:            conn,
+		authInfo:        authInfo,
+		framer:          framer,
+		hBuf:            &buf,
+		hEnc:            hpack.NewEncoder(&buf),
+		maxStreams:      maxStreams,
+		controlBuf:      newRecvBuffer(),
+		fc:              &inFlow{limit: initialConnWindowSize},
+		sendQuotaPool:   newQuotaPool(defaultWindowSize),
+		state:           reachable,
+		writableChan:    make(chan int, 1),
+		shutdownChan:    make(chan struct{}),
+		activeStreams:   make(map[uint32]*Stream),
+		streamSendQuota: defaultWindowSize,
+	}
+	go t.controller()
+	t.writableChan <- 0
+	return t, nil
+}
+
+// operateHeader takes action on the decoded headers.
+func (t *http2Server) operateHeaders(frame *http2.MetaHeadersFrame, handle func(*Stream)) {
+	buf := newRecvBuffer()
+	s := &Stream{
+		id:  frame.Header().StreamID,
+		st:  t,
+		buf: buf,
+		fc:  &inFlow{limit: initialWindowSize},
+	}
+
+	var state decodeState
+	for _, hf := range frame.Fields {
+		state.processHeaderField(hf)
+	}
+	if err := state.err; err != nil {
+		if se, ok := err.(StreamError); ok {
+			t.controlBuf.put(&resetStream{s.id, statusCodeConvTab[se.Code]})
+		}
+		return
+	}
+
+	if frame.StreamEnded() {
+		// s is just created by the caller. No lock needed.
+		s.state = streamReadDone
+	}
+	s.recvCompress = state.encoding
+	if state.timeoutSet {
+		s.ctx, s.cancel = context.WithTimeout(context.TODO(), state.timeout)
+	} else {
+		s.ctx, s.cancel = context.WithCancel(context.TODO())
+	}
+	pr := &peer.Peer{
+		Addr: t.conn.RemoteAddr(),
+	}
+	// Attach Auth info if there is any.
+	if t.authInfo != nil {
+		pr.AuthInfo = t.authInfo
+	}
+	s.ctx = peer.NewContext(s.ctx, pr)
+	// Cache the current stream to the context so that the server application
+	// can find out. Required when the server wants to send some metadata
+	// back to the client (unary call only).
+	s.ctx = newContextWithStream(s.ctx, s)
+	// Attach the received metadata to the context.
+	if len(state.mdata) > 0 {
+		s.ctx = metadata.NewContext(s.ctx, state.mdata)
+	}
+
+	s.dec = &recvBufferReader{
+		ctx:  s.ctx,
+		recv: s.buf,
+	}
+	s.recvCompress = state.encoding
+	s.method = state.method
+	t.mu.Lock()
+	if t.state != reachable {
+		t.mu.Unlock()
+		return
+	}
+	if uint32(len(t.activeStreams)) >= t.maxStreams {
+		t.mu.Unlock()
+		t.controlBuf.put(&resetStream{s.id, http2.ErrCodeRefusedStream})
+		return
+	}
+	s.sendQuotaPool = newQuotaPool(int(t.streamSendQuota))
+	t.activeStreams[s.id] = s
+	t.mu.Unlock()
+	s.windowHandler = func(n int) {
+		t.updateWindow(s, uint32(n))
+	}
+	handle(s)
+}
+
+// HandleStreams receives incoming streams using the given handler. This is
+// typically run in a separate goroutine.
+func (t *http2Server) HandleStreams(handle func(*Stream)) {
+	// Check the validity of client preface.
+	preface := make([]byte, len(clientPreface))
+	if _, err := io.ReadFull(t.conn, preface); err != nil {
+		grpclog.Printf("transport: http2Server.HandleStreams failed to receive the preface from client: %v", err)
+		t.Close()
+		return
+	}
+	if !bytes.Equal(preface, clientPreface) {
+		grpclog.Printf("transport: http2Server.HandleStreams received bogus greeting from client: %q", preface)
+		t.Close()
+		return
+	}
+
+	frame, err := t.framer.readFrame()
+	if err != nil {
+		grpclog.Printf("transport: http2Server.HandleStreams failed to read frame: %v", err)
+		t.Close()
+		return
+	}
+	sf, ok := frame.(*http2.SettingsFrame)
+	if !ok {
+		grpclog.Printf("transport: http2Server.HandleStreams saw invalid preface type %T from client", frame)
+		t.Close()
+		return
+	}
+	t.handleSettings(sf)
+
+	for {
+		frame, err := t.framer.readFrame()
+		if err != nil {
+			if se, ok := err.(http2.StreamError); ok {
+				t.mu.Lock()
+				s := t.activeStreams[se.StreamID]
+				t.mu.Unlock()
+				if s != nil {
+					t.closeStream(s)
+				}
+				t.controlBuf.put(&resetStream{se.StreamID, se.Code})
+				continue
+			}
+			t.Close()
+			return
+		}
+		switch frame := frame.(type) {
+		case *http2.MetaHeadersFrame:
+			id := frame.Header().StreamID
+			if id%2 != 1 || id <= t.maxStreamID {
+				// illegal gRPC stream id.
+				grpclog.Println("transport: http2Server.HandleStreams received an illegal stream id: ", id)
+				t.Close()
+				break
+			}
+			t.maxStreamID = id
+			t.operateHeaders(frame, handle)
+		case *http2.DataFrame:
+			t.handleData(frame)
+		case *http2.RSTStreamFrame:
+			t.handleRSTStream(frame)
+		case *http2.SettingsFrame:
+			t.handleSettings(frame)
+		case *http2.PingFrame:
+			t.handlePing(frame)
+		case *http2.WindowUpdateFrame:
+			t.handleWindowUpdate(frame)
+		case *http2.GoAwayFrame:
+			break
+		default:
+			grpclog.Printf("transport: http2Server.HandleStreams found unhandled frame type %v.", frame)
+		}
+	}
+}
+
+func (t *http2Server) getStream(f http2.Frame) (*Stream, bool) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.activeStreams == nil {
+		// The transport is closing.
+		return nil, false
+	}
+	s, ok := t.activeStreams[f.Header().StreamID]
+	if !ok {
+		// The stream is already done.
+		return nil, false
+	}
+	return s, true
+}
+
+// updateWindow adjusts the inbound quota for the stream and the transport.
+// Window updates will deliver to the controller for sending when
+// the cumulative quota exceeds the corresponding threshold.
+func (t *http2Server) updateWindow(s *Stream, n uint32) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.state == streamDone {
+		return
+	}
+	if w := t.fc.onRead(n); w > 0 {
+		t.controlBuf.put(&windowUpdate{0, w})
+	}
+	if w := s.fc.onRead(n); w > 0 {
+		t.controlBuf.put(&windowUpdate{s.id, w})
+	}
+}
+
+func (t *http2Server) handleData(f *http2.DataFrame) {
+	size := len(f.Data())
+	if err := t.fc.onData(uint32(size)); err != nil {
+		grpclog.Printf("transport: http2Server %v", err)
+		t.Close()
+		return
+	}
+	// Select the right stream to dispatch.
+	s, ok := t.getStream(f)
+	if !ok {
+		if w := t.fc.onRead(uint32(size)); w > 0 {
+			t.controlBuf.put(&windowUpdate{0, w})
+		}
+		return
+	}
+	if size > 0 {
+		s.mu.Lock()
+		if s.state == streamDone {
+			s.mu.Unlock()
+			// The stream has been closed. Release the corresponding quota.
+			if w := t.fc.onRead(uint32(size)); w > 0 {
+				t.controlBuf.put(&windowUpdate{0, w})
+			}
+			return
+		}
+		if err := s.fc.onData(uint32(size)); err != nil {
+			s.mu.Unlock()
+			t.closeStream(s)
+			t.controlBuf.put(&resetStream{s.id, http2.ErrCodeFlowControl})
+			return
+		}
+		s.mu.Unlock()
+		// TODO(bradfitz, zhaoq): A copy is required here because there is no
+		// guarantee f.Data() is consumed before the arrival of next frame.
+		// Can this copy be eliminated?
+		data := make([]byte, size)
+		copy(data, f.Data())
+		s.write(recvMsg{data: data})
+	}
+	if f.Header().Flags.Has(http2.FlagDataEndStream) {
+		// Received the end of stream from the client.
+		s.mu.Lock()
+		if s.state != streamDone {
+			if s.state == streamWriteDone {
+				s.state = streamDone
+			} else {
+				s.state = streamReadDone
+			}
+		}
+		s.mu.Unlock()
+		s.write(recvMsg{err: io.EOF})
+	}
+}
+
+func (t *http2Server) handleRSTStream(f *http2.RSTStreamFrame) {
+	s, ok := t.getStream(f)
+	if !ok {
+		return
+	}
+	t.closeStream(s)
+}
+
+func (t *http2Server) handleSettings(f *http2.SettingsFrame) {
+	if f.IsAck() {
+		return
+	}
+	var ss []http2.Setting
+	f.ForeachSetting(func(s http2.Setting) error {
+		ss = append(ss, s)
+		return nil
+	})
+	// The settings will be applied once the ack is sent.
+	t.controlBuf.put(&settings{ack: true, ss: ss})
+}
+
+func (t *http2Server) handlePing(f *http2.PingFrame) {
+	pingAck := &ping{ack: true}
+	copy(pingAck.data[:], f.Data[:])
+	t.controlBuf.put(pingAck)
+}
+
+func (t *http2Server) handleWindowUpdate(f *http2.WindowUpdateFrame) {
+	id := f.Header().StreamID
+	incr := f.Increment
+	if id == 0 {
+		t.sendQuotaPool.add(int(incr))
+		return
+	}
+	if s, ok := t.getStream(f); ok {
+		s.sendQuotaPool.add(int(incr))
+	}
+}
+
+func (t *http2Server) writeHeaders(s *Stream, b *bytes.Buffer, endStream bool) error {
+	first := true
+	endHeaders := false
+	var err error
+	// Sends the headers in a single batch.
+	for !endHeaders {
+		size := t.hBuf.Len()
+		if size > http2MaxFrameLen {
+			size = http2MaxFrameLen
+		} else {
+			endHeaders = true
+		}
+		if first {
+			p := http2.HeadersFrameParam{
+				StreamID:      s.id,
+				BlockFragment: b.Next(size),
+				EndStream:     endStream,
+				EndHeaders:    endHeaders,
+			}
+			err = t.framer.writeHeaders(endHeaders, p)
+			first = false
+		} else {
+			err = t.framer.writeContinuation(endHeaders, s.id, endHeaders, b.Next(size))
+		}
+		if err != nil {
+			t.Close()
+			return ConnectionErrorf("transport: %v", err)
+		}
+	}
+	return nil
+}
+
+// WriteHeader sends the header metedata md back to the client.
+func (t *http2Server) WriteHeader(s *Stream, md metadata.MD) error {
+	s.mu.Lock()
+	if s.headerOk || s.state == streamDone {
+		s.mu.Unlock()
+		return ErrIllegalHeaderWrite
+	}
+	s.headerOk = true
+	s.mu.Unlock()
+	if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+		return err
+	}
+	t.hBuf.Reset()
+	t.hEnc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+	if s.sendCompress != "" {
+		t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-encoding", Value: s.sendCompress})
+	}
+	for k, v := range md {
+		if isReservedHeader(k) {
+			// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+			continue
+		}
+		for _, entry := range v {
+			t.hEnc.WriteField(hpack.HeaderField{Name: k, Value: entry})
+		}
+	}
+	if err := t.writeHeaders(s, t.hBuf, false); err != nil {
+		return err
+	}
+	t.writableChan <- 0
+	return nil
+}
+
+// WriteStatus sends stream status to the client and terminates the stream.
+// There is no further I/O operations being able to perform on this stream.
+// TODO(zhaoq): Now it indicates the end of entire stream. Revisit if early
+// OK is adopted.
+func (t *http2Server) WriteStatus(s *Stream, statusCode codes.Code, statusDesc string) error {
+	var headersSent bool
+	s.mu.Lock()
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return nil
+	}
+	if s.headerOk {
+		headersSent = true
+	}
+	s.mu.Unlock()
+	if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+		return err
+	}
+	t.hBuf.Reset()
+	if !headersSent {
+		t.hEnc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
+		t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+	}
+	t.hEnc.WriteField(
+		hpack.HeaderField{
+			Name:  "grpc-status",
+			Value: strconv.Itoa(int(statusCode)),
+		})
+	t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-message", Value: statusDesc})
+	// Attach the trailer metadata.
+	for k, v := range s.trailer {
+		// Clients don't tolerate reading restricted headers after some non restricted ones were sent.
+		if isReservedHeader(k) {
+			continue
+		}
+		for _, entry := range v {
+			t.hEnc.WriteField(hpack.HeaderField{Name: k, Value: entry})
+		}
+	}
+	if err := t.writeHeaders(s, t.hBuf, true); err != nil {
+		t.Close()
+		return err
+	}
+	t.closeStream(s)
+	t.writableChan <- 0
+	return nil
+}
+
+// Write converts the data into HTTP2 data frame and sends it out. Non-nil error
+// is returns if it fails (e.g., framing error, transport error).
+func (t *http2Server) Write(s *Stream, data []byte, opts *Options) error {
+	// TODO(zhaoq): Support multi-writers for a single stream.
+	var writeHeaderFrame bool
+	s.mu.Lock()
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return StreamErrorf(codes.Unknown, "the stream has been done")
+	}
+	if !s.headerOk {
+		writeHeaderFrame = true
+		s.headerOk = true
+	}
+	s.mu.Unlock()
+	if writeHeaderFrame {
+		if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+			return err
+		}
+		t.hBuf.Reset()
+		t.hEnc.WriteField(hpack.HeaderField{Name: ":status", Value: "200"})
+		t.hEnc.WriteField(hpack.HeaderField{Name: "content-type", Value: "application/grpc"})
+		if s.sendCompress != "" {
+			t.hEnc.WriteField(hpack.HeaderField{Name: "grpc-encoding", Value: s.sendCompress})
+		}
+		p := http2.HeadersFrameParam{
+			StreamID:      s.id,
+			BlockFragment: t.hBuf.Bytes(),
+			EndHeaders:    true,
+		}
+		if err := t.framer.writeHeaders(false, p); err != nil {
+			t.Close()
+			return ConnectionErrorf("transport: %v", err)
+		}
+		t.writableChan <- 0
+	}
+	r := bytes.NewBuffer(data)
+	for {
+		if r.Len() == 0 {
+			return nil
+		}
+		size := http2MaxFrameLen
+		s.sendQuotaPool.add(0)
+		// Wait until the stream has some quota to send the data.
+		sq, err := wait(s.ctx, t.shutdownChan, s.sendQuotaPool.acquire())
+		if err != nil {
+			return err
+		}
+		t.sendQuotaPool.add(0)
+		// Wait until the transport has some quota to send the data.
+		tq, err := wait(s.ctx, t.shutdownChan, t.sendQuotaPool.acquire())
+		if err != nil {
+			if _, ok := err.(StreamError); ok {
+				t.sendQuotaPool.cancel()
+			}
+			return err
+		}
+		if sq < size {
+			size = sq
+		}
+		if tq < size {
+			size = tq
+		}
+		p := r.Next(size)
+		ps := len(p)
+		if ps < sq {
+			// Overbooked stream quota. Return it back.
+			s.sendQuotaPool.add(sq - ps)
+		}
+		if ps < tq {
+			// Overbooked transport quota. Return it back.
+			t.sendQuotaPool.add(tq - ps)
+		}
+		t.framer.adjustNumWriters(1)
+		// Got some quota. Try to acquire writing privilege on the
+		// transport.
+		if _, err := wait(s.ctx, t.shutdownChan, t.writableChan); err != nil {
+			if _, ok := err.(StreamError); ok {
+				// Return the connection quota back.
+				t.sendQuotaPool.add(ps)
+			}
+			if t.framer.adjustNumWriters(-1) == 0 {
+				// This writer is the last one in this batch and has the
+				// responsibility to flush the buffered frames. It queues
+				// a flush request to controlBuf instead of flushing directly
+				// in order to avoid the race with other writing or flushing.
+				t.controlBuf.put(&flushIO{})
+			}
+			return err
+		}
+		select {
+		case <-s.ctx.Done():
+			t.sendQuotaPool.add(ps)
+			if t.framer.adjustNumWriters(-1) == 0 {
+				t.controlBuf.put(&flushIO{})
+			}
+			t.writableChan <- 0
+			return ContextErr(s.ctx.Err())
+		default:
+		}
+		var forceFlush bool
+		if r.Len() == 0 && t.framer.adjustNumWriters(0) == 1 && !opts.Last {
+			forceFlush = true
+		}
+		if err := t.framer.writeData(forceFlush, s.id, false, p); err != nil {
+			t.Close()
+			return ConnectionErrorf("transport: %v", err)
+		}
+		if t.framer.adjustNumWriters(-1) == 0 {
+			t.framer.flushWrite()
+		}
+		t.writableChan <- 0
+	}
+
+}
+
+func (t *http2Server) applySettings(ss []http2.Setting) {
+	for _, s := range ss {
+		if s.ID == http2.SettingInitialWindowSize {
+			t.mu.Lock()
+			defer t.mu.Unlock()
+			for _, stream := range t.activeStreams {
+				stream.sendQuotaPool.reset(int(s.Val - t.streamSendQuota))
+			}
+			t.streamSendQuota = s.Val
+		}
+
+	}
+}
+
+// controller running in a separate goroutine takes charge of sending control
+// frames (e.g., window update, reset stream, setting, etc.) to the server.
+func (t *http2Server) controller() {
+	for {
+		select {
+		case i := <-t.controlBuf.get():
+			t.controlBuf.load()
+			select {
+			case <-t.writableChan:
+				switch i := i.(type) {
+				case *windowUpdate:
+					t.framer.writeWindowUpdate(true, i.streamID, i.increment)
+				case *settings:
+					if i.ack {
+						t.framer.writeSettingsAck(true)
+						t.applySettings(i.ss)
+					} else {
+						t.framer.writeSettings(true, i.ss...)
+					}
+				case *resetStream:
+					t.framer.writeRSTStream(true, i.streamID, i.code)
+				case *flushIO:
+					t.framer.flushWrite()
+				case *ping:
+					t.framer.writePing(true, i.ack, i.data)
+				default:
+					grpclog.Printf("transport: http2Server.controller got unexpected item type %v\n", i)
+				}
+				t.writableChan <- 0
+				continue
+			case <-t.shutdownChan:
+				return
+			}
+		case <-t.shutdownChan:
+			return
+		}
+	}
+}
+
+// Close starts shutting down the http2Server transport.
+// TODO(zhaoq): Now the destruction is not blocked on any pending streams. This
+// could cause some resource issue. Revisit this later.
+func (t *http2Server) Close() (err error) {
+	t.mu.Lock()
+	if t.state == closing {
+		t.mu.Unlock()
+		return errors.New("transport: Close() was already called")
+	}
+	t.state = closing
+	streams := t.activeStreams
+	t.activeStreams = nil
+	t.mu.Unlock()
+	close(t.shutdownChan)
+	err = t.conn.Close()
+	// Cancel all active streams.
+	for _, s := range streams {
+		s.cancel()
+	}
+	return
+}
+
+// closeStream clears the footprint of a stream when the stream is not needed
+// any more.
+func (t *http2Server) closeStream(s *Stream) {
+	t.mu.Lock()
+	delete(t.activeStreams, s.id)
+	t.mu.Unlock()
+	// In case stream sending and receiving are invoked in separate
+	// goroutines (e.g., bi-directional streaming), cancel needs to be
+	// called to interrupt the potential blocking on other goroutines.
+	s.cancel()
+	s.mu.Lock()
+	if q := s.fc.resetPendingData(); q > 0 {
+		if w := t.fc.onRead(q); w > 0 {
+			t.controlBuf.put(&windowUpdate{0, w})
+		}
+	}
+	if s.state == streamDone {
+		s.mu.Unlock()
+		return
+	}
+	s.state = streamDone
+	s.mu.Unlock()
+}
+
+func (t *http2Server) RemoteAddr() net.Addr {
+	return t.conn.RemoteAddr()
+}
diff --git a/vendor/google.golang.org/grpc/transport/http_util.go b/vendor/google.golang.org/grpc/transport/http_util.go
new file mode 100644
index 0000000..a4b1b07
--- /dev/null
+++ b/vendor/google.golang.org/grpc/transport/http_util.go
@@ -0,0 +1,422 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+package transport
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+	"strings"
+	"sync/atomic"
+	"time"
+
+	"golang.org/x/net/http2"
+	"golang.org/x/net/http2/hpack"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/grpclog"
+	"google.golang.org/grpc/metadata"
+)
+
+const (
+	// The primary user agent
+	primaryUA = "grpc-go/0.11"
+	// http2MaxFrameLen specifies the max length of a HTTP2 frame.
+	http2MaxFrameLen = 16384 // 16KB frame
+	// http://http2.github.io/http2-spec/#SettingValues
+	http2InitHeaderTableSize = 4096
+	// http2IOBufSize specifies the buffer size for sending frames.
+	http2IOBufSize = 32 * 1024
+)
+
+var (
+	clientPreface   = []byte(http2.ClientPreface)
+	http2ErrConvTab = map[http2.ErrCode]codes.Code{
+		http2.ErrCodeNo:                 codes.Internal,
+		http2.ErrCodeProtocol:           codes.Internal,
+		http2.ErrCodeInternal:           codes.Internal,
+		http2.ErrCodeFlowControl:        codes.ResourceExhausted,
+		http2.ErrCodeSettingsTimeout:    codes.Internal,
+		http2.ErrCodeStreamClosed:       codes.Internal,
+		http2.ErrCodeFrameSize:          codes.Internal,
+		http2.ErrCodeRefusedStream:      codes.Unavailable,
+		http2.ErrCodeCancel:             codes.Canceled,
+		http2.ErrCodeCompression:        codes.Internal,
+		http2.ErrCodeConnect:            codes.Internal,
+		http2.ErrCodeEnhanceYourCalm:    codes.ResourceExhausted,
+		http2.ErrCodeInadequateSecurity: codes.PermissionDenied,
+		http2.ErrCodeHTTP11Required:     codes.FailedPrecondition,
+	}
+	statusCodeConvTab = map[codes.Code]http2.ErrCode{
+		codes.Internal:          http2.ErrCodeInternal,
+		codes.Canceled:          http2.ErrCodeCancel,
+		codes.Unavailable:       http2.ErrCodeRefusedStream,
+		codes.ResourceExhausted: http2.ErrCodeEnhanceYourCalm,
+		codes.PermissionDenied:  http2.ErrCodeInadequateSecurity,
+	}
+)
+
+// Records the states during HPACK decoding. Must be reset once the
+// decoding of the entire headers are finished.
+type decodeState struct {
+	err error // first error encountered decoding
+
+	encoding string
+	// statusCode caches the stream status received from the trailer
+	// the server sent. Client side only.
+	statusCode codes.Code
+	statusDesc string
+	// Server side only fields.
+	timeoutSet bool
+	timeout    time.Duration
+	method     string
+	// key-value metadata map from the peer.
+	mdata map[string][]string
+}
+
+// isReservedHeader checks whether hdr belongs to HTTP2 headers
+// reserved by gRPC protocol. Any other headers are classified as the
+// user-specified metadata.
+func isReservedHeader(hdr string) bool {
+	if hdr != "" && hdr[0] == ':' {
+		return true
+	}
+	switch hdr {
+	case "content-type",
+		"grpc-message-type",
+		"grpc-encoding",
+		"grpc-message",
+		"grpc-status",
+		"grpc-timeout",
+		"te":
+		return true
+	default:
+		return false
+	}
+}
+
+// isWhitelistedPseudoHeader checks whether hdr belongs to HTTP2 pseudoheaders
+// that should be propagated into metadata visible to users.
+func isWhitelistedPseudoHeader(hdr string) bool {
+	switch hdr {
+	case ":authority":
+		return true
+	default:
+		return false
+	}
+}
+
+func (d *decodeState) setErr(err error) {
+	if d.err == nil {
+		d.err = err
+	}
+}
+
+func (d *decodeState) processHeaderField(f hpack.HeaderField) {
+	switch f.Name {
+	case "content-type":
+		if !strings.Contains(f.Value, "application/grpc") {
+			d.setErr(StreamErrorf(codes.FailedPrecondition, "transport: received the unexpected content-type %q", f.Value))
+			return
+		}
+	case "grpc-encoding":
+		d.encoding = f.Value
+	case "grpc-status":
+		code, err := strconv.Atoi(f.Value)
+		if err != nil {
+			d.setErr(StreamErrorf(codes.Internal, "transport: malformed grpc-status: %v", err))
+			return
+		}
+		d.statusCode = codes.Code(code)
+	case "grpc-message":
+		d.statusDesc = f.Value
+	case "grpc-timeout":
+		d.timeoutSet = true
+		var err error
+		d.timeout, err = timeoutDecode(f.Value)
+		if err != nil {
+			d.setErr(StreamErrorf(codes.Internal, "transport: malformed time-out: %v", err))
+			return
+		}
+	case ":path":
+		d.method = f.Value
+	default:
+		if !isReservedHeader(f.Name) || isWhitelistedPseudoHeader(f.Name) {
+			if f.Name == "user-agent" {
+				i := strings.LastIndex(f.Value, " ")
+				if i == -1 {
+					// There is no application user agent string being set.
+					return
+				}
+				// Extract the application user agent string.
+				f.Value = f.Value[:i]
+			}
+			if d.mdata == nil {
+				d.mdata = make(map[string][]string)
+			}
+			k, v, err := metadata.DecodeKeyValue(f.Name, f.Value)
+			if err != nil {
+				grpclog.Printf("Failed to decode (%q, %q): %v", f.Name, f.Value, err)
+				return
+			}
+			d.mdata[k] = append(d.mdata[k], v)
+		}
+	}
+}
+
+type timeoutUnit uint8
+
+const (
+	hour        timeoutUnit = 'H'
+	minute      timeoutUnit = 'M'
+	second      timeoutUnit = 'S'
+	millisecond timeoutUnit = 'm'
+	microsecond timeoutUnit = 'u'
+	nanosecond  timeoutUnit = 'n'
+)
+
+func timeoutUnitToDuration(u timeoutUnit) (d time.Duration, ok bool) {
+	switch u {
+	case hour:
+		return time.Hour, true
+	case minute:
+		return time.Minute, true
+	case second:
+		return time.Second, true
+	case millisecond:
+		return time.Millisecond, true
+	case microsecond:
+		return time.Microsecond, true
+	case nanosecond:
+		return time.Nanosecond, true
+	default:
+	}
+	return
+}
+
+const maxTimeoutValue int64 = 100000000 - 1
+
+// div does integer division and round-up the result. Note that this is
+// equivalent to (d+r-1)/r but has less chance to overflow.
+func div(d, r time.Duration) int64 {
+	if m := d % r; m > 0 {
+		return int64(d/r + 1)
+	}
+	return int64(d / r)
+}
+
+// TODO(zhaoq): It is the simplistic and not bandwidth efficient. Improve it.
+func timeoutEncode(t time.Duration) string {
+	if d := div(t, time.Nanosecond); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "n"
+	}
+	if d := div(t, time.Microsecond); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "u"
+	}
+	if d := div(t, time.Millisecond); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "m"
+	}
+	if d := div(t, time.Second); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "S"
+	}
+	if d := div(t, time.Minute); d <= maxTimeoutValue {
+		return strconv.FormatInt(d, 10) + "M"
+	}
+	// Note that maxTimeoutValue * time.Hour > MaxInt64.
+	return strconv.FormatInt(div(t, time.Hour), 10) + "H"
+}
+
+func timeoutDecode(s string) (time.Duration, error) {
+	size := len(s)
+	if size < 2 {
+		return 0, fmt.Errorf("transport: timeout string is too short: %q", s)
+	}
+	unit := timeoutUnit(s[size-1])
+	d, ok := timeoutUnitToDuration(unit)
+	if !ok {
+		return 0, fmt.Errorf("transport: timeout unit is not recognized: %q", s)
+	}
+	t, err := strconv.ParseInt(s[:size-1], 10, 64)
+	if err != nil {
+		return 0, err
+	}
+	return d * time.Duration(t), nil
+}
+
+type framer struct {
+	numWriters int32
+	reader     io.Reader
+	writer     *bufio.Writer
+	fr         *http2.Framer
+}
+
+func newFramer(conn net.Conn) *framer {
+	f := &framer{
+		reader: bufio.NewReaderSize(conn, http2IOBufSize),
+		writer: bufio.NewWriterSize(conn, http2IOBufSize),
+	}
+	f.fr = http2.NewFramer(f.writer, f.reader)
+	f.fr.ReadMetaHeaders = hpack.NewDecoder(http2InitHeaderTableSize, nil)
+	return f
+}
+
+func (f *framer) adjustNumWriters(i int32) int32 {
+	return atomic.AddInt32(&f.numWriters, i)
+}
+
+// The following writeXXX functions can only be called when the caller gets
+// unblocked from writableChan channel (i.e., owns the privilege to write).
+
+func (f *framer) writeContinuation(forceFlush bool, streamID uint32, endHeaders bool, headerBlockFragment []byte) error {
+	if err := f.fr.WriteContinuation(streamID, endHeaders, headerBlockFragment); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeData(forceFlush bool, streamID uint32, endStream bool, data []byte) error {
+	if err := f.fr.WriteData(streamID, endStream, data); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeGoAway(forceFlush bool, maxStreamID uint32, code http2.ErrCode, debugData []byte) error {
+	if err := f.fr.WriteGoAway(maxStreamID, code, debugData); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeHeaders(forceFlush bool, p http2.HeadersFrameParam) error {
+	if err := f.fr.WriteHeaders(p); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writePing(forceFlush, ack bool, data [8]byte) error {
+	if err := f.fr.WritePing(ack, data); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writePriority(forceFlush bool, streamID uint32, p http2.PriorityParam) error {
+	if err := f.fr.WritePriority(streamID, p); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writePushPromise(forceFlush bool, p http2.PushPromiseParam) error {
+	if err := f.fr.WritePushPromise(p); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeRSTStream(forceFlush bool, streamID uint32, code http2.ErrCode) error {
+	if err := f.fr.WriteRSTStream(streamID, code); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeSettings(forceFlush bool, settings ...http2.Setting) error {
+	if err := f.fr.WriteSettings(settings...); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeSettingsAck(forceFlush bool) error {
+	if err := f.fr.WriteSettingsAck(); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) writeWindowUpdate(forceFlush bool, streamID, incr uint32) error {
+	if err := f.fr.WriteWindowUpdate(streamID, incr); err != nil {
+		return err
+	}
+	if forceFlush {
+		return f.writer.Flush()
+	}
+	return nil
+}
+
+func (f *framer) flushWrite() error {
+	return f.writer.Flush()
+}
+
+func (f *framer) readFrame() (http2.Frame, error) {
+	return f.fr.ReadFrame()
+}
+
+func (f *framer) errorDetail() error {
+	return f.fr.ErrorDetail()
+}
diff --git a/vendor/google.golang.org/grpc/transport/transport.go b/vendor/google.golang.org/grpc/transport/transport.go
new file mode 100644
index 0000000..1c9af54
--- /dev/null
+++ b/vendor/google.golang.org/grpc/transport/transport.go
@@ -0,0 +1,513 @@
+/*
+ *
+ * Copyright 2014, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+/*
+Package transport defines and implements message oriented communication channel
+to complete various transactions (e.g., an RPC).
+*/
+package transport // import "google.golang.org/grpc/transport"
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"sync"
+	"time"
+
+	"golang.org/x/net/context"
+	"golang.org/x/net/trace"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/metadata"
+)
+
+// recvMsg represents the received msg from the transport. All transport
+// protocol specific info has been removed.
+type recvMsg struct {
+	data []byte
+	// nil: received some data
+	// io.EOF: stream is completed. data is nil.
+	// other non-nil error: transport failure. data is nil.
+	err error
+}
+
+func (*recvMsg) item() {}
+
+// All items in an out of a recvBuffer should be the same type.
+type item interface {
+	item()
+}
+
+// recvBuffer is an unbounded channel of item.
+type recvBuffer struct {
+	c       chan item
+	mu      sync.Mutex
+	backlog []item
+}
+
+func newRecvBuffer() *recvBuffer {
+	b := &recvBuffer{
+		c: make(chan item, 1),
+	}
+	return b
+}
+
+func (b *recvBuffer) put(r item) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if len(b.backlog) == 0 {
+		select {
+		case b.c <- r:
+			return
+		default:
+		}
+	}
+	b.backlog = append(b.backlog, r)
+}
+
+func (b *recvBuffer) load() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if len(b.backlog) > 0 {
+		select {
+		case b.c <- b.backlog[0]:
+			b.backlog = b.backlog[1:]
+		default:
+		}
+	}
+}
+
+// get returns the channel that receives an item in the buffer.
+//
+// Upon receipt of an item, the caller should call load to send another
+// item onto the channel if there is any.
+func (b *recvBuffer) get() <-chan item {
+	return b.c
+}
+
+// recvBufferReader implements io.Reader interface to read the data from
+// recvBuffer.
+type recvBufferReader struct {
+	ctx  context.Context
+	recv *recvBuffer
+	last *bytes.Reader // Stores the remaining data in the previous calls.
+	err  error
+}
+
+// Read reads the next len(p) bytes from last. If last is drained, it tries to
+// read additional data from recv. It blocks if there no additional data available
+// in recv. If Read returns any non-nil error, it will continue to return that error.
+func (r *recvBufferReader) Read(p []byte) (n int, err error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+	defer func() { r.err = err }()
+	if r.last != nil && r.last.Len() > 0 {
+		// Read remaining data left in last call.
+		return r.last.Read(p)
+	}
+	select {
+	case <-r.ctx.Done():
+		return 0, ContextErr(r.ctx.Err())
+	case i := <-r.recv.get():
+		r.recv.load()
+		m := i.(*recvMsg)
+		if m.err != nil {
+			return 0, m.err
+		}
+		r.last = bytes.NewReader(m.data)
+		return r.last.Read(p)
+	}
+}
+
+type streamState uint8
+
+const (
+	streamActive    streamState = iota
+	streamWriteDone             // EndStream sent
+	streamReadDone              // EndStream received
+	streamDone                  // sendDone and recvDone or RSTStreamFrame is sent or received.
+)
+
+// Stream represents an RPC in the transport layer.
+type Stream struct {
+	id uint32
+	// nil for client side Stream.
+	st ServerTransport
+	// ctx is the associated context of the stream.
+	ctx    context.Context
+	cancel context.CancelFunc
+	// method records the associated RPC method of the stream.
+	method       string
+	recvCompress string
+	sendCompress string
+	buf          *recvBuffer
+	dec          io.Reader
+	fc           *inFlow
+	recvQuota    uint32
+	// The accumulated inbound quota pending for window update.
+	updateQuota uint32
+	// The handler to control the window update procedure for both this
+	// particular stream and the associated transport.
+	windowHandler func(int)
+
+	sendQuotaPool *quotaPool
+	// Close headerChan to indicate the end of reception of header metadata.
+	headerChan chan struct{}
+	// header caches the received header metadata.
+	header metadata.MD
+	// The key-value map of trailer metadata.
+	trailer metadata.MD
+
+	mu sync.RWMutex // guard the following
+	// headerOK becomes true from the first header is about to send.
+	headerOk bool
+	state    streamState
+	// true iff headerChan is closed. Used to avoid closing headerChan
+	// multiple times.
+	headerDone bool
+	// the status received from the server.
+	statusCode codes.Code
+	statusDesc string
+}
+
+// RecvCompress returns the compression algorithm applied to the inbound
+// message. It is empty string if there is no compression applied.
+func (s *Stream) RecvCompress() string {
+	return s.recvCompress
+}
+
+// SetSendCompress sets the compression algorithm to the stream.
+func (s *Stream) SetSendCompress(str string) {
+	s.sendCompress = str
+}
+
+// Header acquires the key-value pairs of header metadata once it
+// is available. It blocks until i) the metadata is ready or ii) there is no
+// header metadata or iii) the stream is cancelled/expired.
+func (s *Stream) Header() (metadata.MD, error) {
+	select {
+	case <-s.ctx.Done():
+		return nil, ContextErr(s.ctx.Err())
+	case <-s.headerChan:
+		return s.header.Copy(), nil
+	}
+}
+
+// Trailer returns the cached trailer metedata. Note that if it is not called
+// after the entire stream is done, it could return an empty MD. Client
+// side only.
+func (s *Stream) Trailer() metadata.MD {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+	return s.trailer.Copy()
+}
+
+// ServerTransport returns the underlying ServerTransport for the stream.
+// The client side stream always returns nil.
+func (s *Stream) ServerTransport() ServerTransport {
+	return s.st
+}
+
+// Context returns the context of the stream.
+func (s *Stream) Context() context.Context {
+	return s.ctx
+}
+
+// TraceContext recreates the context of s with a trace.Trace.
+func (s *Stream) TraceContext(tr trace.Trace) {
+	s.ctx = trace.NewContext(s.ctx, tr)
+}
+
+// Method returns the method for the stream.
+func (s *Stream) Method() string {
+	return s.method
+}
+
+// StatusCode returns statusCode received from the server.
+func (s *Stream) StatusCode() codes.Code {
+	return s.statusCode
+}
+
+// StatusDesc returns statusDesc received from the server.
+func (s *Stream) StatusDesc() string {
+	return s.statusDesc
+}
+
+// ErrIllegalTrailerSet indicates that the trailer has already been set or it
+// is too late to do so.
+var ErrIllegalTrailerSet = errors.New("transport: trailer has been set")
+
+// SetTrailer sets the trailer metadata which will be sent with the RPC status
+// by the server. This can only be called at most once. Server side only.
+func (s *Stream) SetTrailer(md metadata.MD) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.trailer != nil {
+		return ErrIllegalTrailerSet
+	}
+	s.trailer = md.Copy()
+	return nil
+}
+
+func (s *Stream) write(m recvMsg) {
+	s.buf.put(&m)
+}
+
+// Read reads all the data available for this Stream from the transport and
+// passes them into the decoder, which converts them into a gRPC message stream.
+// The error is io.EOF when the stream is done or another non-nil error if
+// the stream broke.
+func (s *Stream) Read(p []byte) (n int, err error) {
+	n, err = s.dec.Read(p)
+	if err != nil {
+		return
+	}
+	s.windowHandler(n)
+	return
+}
+
+// The key to save transport.Stream in the context.
+type streamKey struct{}
+
+// newContextWithStream creates a new context from ctx and attaches stream
+// to it.
+func newContextWithStream(ctx context.Context, stream *Stream) context.Context {
+	return context.WithValue(ctx, streamKey{}, stream)
+}
+
+// StreamFromContext returns the stream saved in ctx.
+func StreamFromContext(ctx context.Context) (s *Stream, ok bool) {
+	s, ok = ctx.Value(streamKey{}).(*Stream)
+	return
+}
+
+// state of transport
+type transportState int
+
+const (
+	reachable transportState = iota
+	unreachable
+	closing
+	draining
+)
+
+// NewServerTransport creates a ServerTransport with conn or non-nil error
+// if it fails.
+func NewServerTransport(protocol string, conn net.Conn, maxStreams uint32, authInfo credentials.AuthInfo) (ServerTransport, error) {
+	return newHTTP2Server(conn, maxStreams, authInfo)
+}
+
+// ConnectOptions covers all relevant options for dialing a server.
+type ConnectOptions struct {
+	// UserAgent is the application user agent.
+	UserAgent string
+	// Dialer specifies how to dial a network address.
+	Dialer func(string, time.Duration) (net.Conn, error)
+	// AuthOptions stores the credentials required to setup a client connection and/or issue RPCs.
+	AuthOptions []credentials.Credentials
+	// Timeout specifies the timeout for dialing a client connection.
+	Timeout time.Duration
+}
+
+// NewClientTransport establishes the transport with the required ConnectOptions
+// and returns it to the caller.
+func NewClientTransport(target string, opts *ConnectOptions) (ClientTransport, error) {
+	return newHTTP2Client(target, opts)
+}
+
+// Options provides additional hints and information for message
+// transmission.
+type Options struct {
+	// Last indicates whether this write is the last piece for
+	// this stream.
+	Last bool
+
+	// Delay is a hint to the transport implementation for whether
+	// the data could be buffered for a batching write. The
+	// Transport implementation may ignore the hint.
+	Delay bool
+}
+
+// CallHdr carries the information of a particular RPC.
+type CallHdr struct {
+	// Host specifies the peer's host.
+	Host string
+
+	// Method specifies the operation to perform.
+	Method string
+
+	// RecvCompress specifies the compression algorithm applied on
+	// inbound messages.
+	RecvCompress string
+
+	// SendCompress specifies the compression algorithm applied on
+	// outbound message.
+	SendCompress string
+
+	// Flush indicates whether a new stream command should be sent
+	// to the peer without waiting for the first data. This is
+	// only a hint. The transport may modify the flush decision
+	// for performance purposes.
+	Flush bool
+}
+
+// ClientTransport is the common interface for all gRPC client-side transport
+// implementations.
+type ClientTransport interface {
+	// Close tears down this transport. Once it returns, the transport
+	// should not be accessed any more. The caller must make sure this
+	// is called only once.
+	Close() error
+
+	// GracefulClose starts to tear down the transport. It stops accepting
+	// new RPCs and wait the completion of the pending RPCs.
+	GracefulClose() error
+
+	// Write sends the data for the given stream. A nil stream indicates
+	// the write is to be performed on the transport as a whole.
+	Write(s *Stream, data []byte, opts *Options) error
+
+	// NewStream creates a Stream for an RPC.
+	NewStream(ctx context.Context, callHdr *CallHdr) (*Stream, error)
+
+	// CloseStream clears the footprint of a stream when the stream is
+	// not needed any more. The err indicates the error incurred when
+	// CloseStream is called. Must be called when a stream is finished
+	// unless the associated transport is closing.
+	CloseStream(stream *Stream, err error)
+
+	// Error returns a channel that is closed when some I/O error
+	// happens. Typically the caller should have a goroutine to monitor
+	// this in order to take action (e.g., close the current transport
+	// and create a new one) in error case. It should not return nil
+	// once the transport is initiated.
+	Error() <-chan struct{}
+}
+
+// ServerTransport is the common interface for all gRPC server-side transport
+// implementations.
+//
+// Methods may be called concurrently from multiple goroutines, but
+// Write methods for a given Stream will be called serially.
+type ServerTransport interface {
+	// HandleStreams receives incoming streams using the given handler.
+	HandleStreams(func(*Stream))
+
+	// WriteHeader sends the header metadata for the given stream.
+	// WriteHeader may not be called on all streams.
+	WriteHeader(s *Stream, md metadata.MD) error
+
+	// Write sends the data for the given stream.
+	// Write may not be called on all streams.
+	Write(s *Stream, data []byte, opts *Options) error
+
+	// WriteStatus sends the status of a stream to the client.
+	// WriteStatus is the final call made on a stream and always
+	// occurs.
+	WriteStatus(s *Stream, statusCode codes.Code, statusDesc string) error
+
+	// Close tears down the transport. Once it is called, the transport
+	// should not be accessed any more. All the pending streams and their
+	// handlers will be terminated asynchronously.
+	Close() error
+
+	// RemoteAddr returns the remote network address.
+	RemoteAddr() net.Addr
+}
+
+// StreamErrorf creates an StreamError with the specified error code and description.
+func StreamErrorf(c codes.Code, format string, a ...interface{}) StreamError {
+	return StreamError{
+		Code: c,
+		Desc: fmt.Sprintf(format, a...),
+	}
+}
+
+// ConnectionErrorf creates an ConnectionError with the specified error description.
+func ConnectionErrorf(format string, a ...interface{}) ConnectionError {
+	return ConnectionError{
+		Desc: fmt.Sprintf(format, a...),
+	}
+}
+
+// ConnectionError is an error that results in the termination of the
+// entire connection and the retry of all the active streams.
+type ConnectionError struct {
+	Desc string
+}
+
+func (e ConnectionError) Error() string {
+	return fmt.Sprintf("connection error: desc = %q", e.Desc)
+}
+
+// Define some common ConnectionErrors.
+var ErrConnClosing = ConnectionError{Desc: "transport is closing"}
+
+// StreamError is an error that only affects one stream within a connection.
+type StreamError struct {
+	Code codes.Code
+	Desc string
+}
+
+func (e StreamError) Error() string {
+	return fmt.Sprintf("stream error: code = %d desc = %q", e.Code, e.Desc)
+}
+
+// ContextErr converts the error from context package into a StreamError.
+func ContextErr(err error) StreamError {
+	switch err {
+	case context.DeadlineExceeded:
+		return StreamErrorf(codes.DeadlineExceeded, "%v", err)
+	case context.Canceled:
+		return StreamErrorf(codes.Canceled, "%v", err)
+	}
+	panic(fmt.Sprintf("Unexpected error from context packet: %v", err))
+}
+
+// wait blocks until it can receive from ctx.Done, closing, or proceed.
+// If it receives from ctx.Done, it returns 0, the StreamError for ctx.Err.
+// If it receives from closing, it returns 0, ErrConnClosing.
+// If it receives from proceed, it returns the received integer, nil.
+func wait(ctx context.Context, closing <-chan struct{}, proceed <-chan int) (int, error) {
+	select {
+	case <-ctx.Done():
+		return 0, ContextErr(ctx.Err())
+	case <-closing:
+		return 0, ErrConnClosing
+	case i := <-proceed:
+		return i, nil
+	}
+}