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transport.go
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transport.go
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/*
*
* 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"
"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) isItem() bool {
return true
}
// All items in an out of a recvBuffer should be the same type.
type item interface {
isItem() bool
}
// 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()
b.backlog = append(b.backlog, r)
select {
case b.c <- b.backlog[0]:
b.backlog = b.backlog[1:]
default:
}
}
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
buf *recvBuffer
dec io.Reader
// updateStreams indicates whether the transport's streamsQuota needed
// to be updated when this stream is closed. It is false when the transport
// sticks to the initial infinite value of the number of concurrent streams.
// Ture otherwise.
updateStreams bool
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
}
// 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
}
// 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
}
type key int
// The key to save transport.Stream in the context.
const streamKey = key(0)
// 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
)
// NewServerTransport creates a ServerTransport with conn or non-nil error
// if it fails.
func NewServerTransport(protocol string, conn net.Conn, maxStreams uint32) (ServerTransport, error) {
return newHTTP2Server(conn, maxStreams)
}
// ConnectOptions covers all relevant options for dialing a server.
type ConnectOptions struct {
Dialer func(string, time.Duration) (net.Conn, error)
AuthOptions []credentials.Credentials
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 {
// Indicate whether it is the last piece for this stream.
Last bool
// The hint to transport impl whether the data could be buffered for
// batching write. Transport impl can feel free to ignore it.
Delay bool
}
// CallHdr carries the information of a particular RPC.
type CallHdr struct {
Host string // peer host
Method string // the operation to perform on the specified host
}
// 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
// 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.
type ServerTransport interface {
// WriteStatus sends the status of a stream to the client.
WriteStatus(s *Stream, statusCode codes.Code, statusDesc string) error
// Write sends the data for the given stream.
Write(s *Stream, data []byte, opts *Options) error
// WriteHeader sends the header metedata for the given stream.
WriteHeader(s *Stream, md metadata.MD) error
// HandleStreams receives incoming streams using the given handler.
HandleStreams(func(*Stream))
// 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
}
// 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
}
}