go.etcd.io/etcd@v3.3.27+incompatible/proxy/grpcproxy/adapter/chan_stream.go (about)

     1  // Copyright 2017 The etcd Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package adapter
    16  
    17  import (
    18  	"context"
    19  
    20  	"google.golang.org/grpc"
    21  	"google.golang.org/grpc/metadata"
    22  )
    23  
    24  // chanServerStream implements grpc.ServerStream with a chanStream
    25  type chanServerStream struct {
    26  	headerc  chan<- metadata.MD
    27  	trailerc chan<- metadata.MD
    28  	grpc.Stream
    29  
    30  	headers []metadata.MD
    31  }
    32  
    33  func (ss *chanServerStream) SendHeader(md metadata.MD) error {
    34  	if ss.headerc == nil {
    35  		return errAlreadySentHeader
    36  	}
    37  	outmd := make(map[string][]string)
    38  	for _, h := range append(ss.headers, md) {
    39  		for k, v := range h {
    40  			outmd[k] = v
    41  		}
    42  	}
    43  	select {
    44  	case ss.headerc <- outmd:
    45  		ss.headerc = nil
    46  		ss.headers = nil
    47  		return nil
    48  	case <-ss.Context().Done():
    49  	}
    50  	return ss.Context().Err()
    51  }
    52  
    53  func (ss *chanServerStream) SetHeader(md metadata.MD) error {
    54  	if ss.headerc == nil {
    55  		return errAlreadySentHeader
    56  	}
    57  	ss.headers = append(ss.headers, md)
    58  	return nil
    59  }
    60  
    61  func (ss *chanServerStream) SetTrailer(md metadata.MD) {
    62  	ss.trailerc <- md
    63  }
    64  
    65  // chanClientStream implements grpc.ClientStream with a chanStream
    66  type chanClientStream struct {
    67  	headerc  <-chan metadata.MD
    68  	trailerc <-chan metadata.MD
    69  	*chanStream
    70  }
    71  
    72  func (cs *chanClientStream) Header() (metadata.MD, error) {
    73  	select {
    74  	case md := <-cs.headerc:
    75  		return md, nil
    76  	case <-cs.Context().Done():
    77  	}
    78  	return nil, cs.Context().Err()
    79  }
    80  
    81  func (cs *chanClientStream) Trailer() metadata.MD {
    82  	select {
    83  	case md := <-cs.trailerc:
    84  		return md
    85  	case <-cs.Context().Done():
    86  		return nil
    87  	}
    88  }
    89  
    90  func (cs *chanClientStream) CloseSend() error {
    91  	close(cs.chanStream.sendc)
    92  	return nil
    93  }
    94  
    95  // chanStream implements grpc.Stream using channels
    96  type chanStream struct {
    97  	recvc  <-chan interface{}
    98  	sendc  chan<- interface{}
    99  	ctx    context.Context
   100  	cancel context.CancelFunc
   101  }
   102  
   103  func (s *chanStream) Context() context.Context { return s.ctx }
   104  
   105  func (s *chanStream) SendMsg(m interface{}) error {
   106  	select {
   107  	case s.sendc <- m:
   108  		if err, ok := m.(error); ok {
   109  			return err
   110  		}
   111  		return nil
   112  	case <-s.ctx.Done():
   113  	}
   114  	return s.ctx.Err()
   115  }
   116  
   117  func (s *chanStream) RecvMsg(m interface{}) error {
   118  	v := m.(*interface{})
   119  	for {
   120  		select {
   121  		case msg, ok := <-s.recvc:
   122  			if !ok {
   123  				return grpc.ErrClientConnClosing
   124  			}
   125  			if err, ok := msg.(error); ok {
   126  				return err
   127  			}
   128  			*v = msg
   129  			return nil
   130  		case <-s.ctx.Done():
   131  		}
   132  		if len(s.recvc) == 0 {
   133  			// prioritize any pending recv messages over canceled context
   134  			break
   135  		}
   136  	}
   137  	return s.ctx.Err()
   138  }
   139  
   140  func newPipeStream(ctx context.Context, ssHandler func(chanServerStream) error) chanClientStream {
   141  	// ch1 is buffered so server can send error on close
   142  	ch1, ch2 := make(chan interface{}, 1), make(chan interface{})
   143  	headerc, trailerc := make(chan metadata.MD, 1), make(chan metadata.MD, 1)
   144  
   145  	cctx, ccancel := context.WithCancel(ctx)
   146  	cli := &chanStream{recvc: ch1, sendc: ch2, ctx: cctx, cancel: ccancel}
   147  	cs := chanClientStream{headerc, trailerc, cli}
   148  
   149  	sctx, scancel := context.WithCancel(ctx)
   150  	srv := &chanStream{recvc: ch2, sendc: ch1, ctx: sctx, cancel: scancel}
   151  	ss := chanServerStream{headerc, trailerc, srv, nil}
   152  
   153  	go func() {
   154  		if err := ssHandler(ss); err != nil {
   155  			select {
   156  			case srv.sendc <- err:
   157  			case <-sctx.Done():
   158  			case <-cctx.Done():
   159  			}
   160  		}
   161  		scancel()
   162  		ccancel()
   163  	}()
   164  	return cs
   165  }