chan_stream.go

Documentation: go.etcd.io/etcd/server/v3/proxy/grpcproxy/adapter

     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/codes"
    22  	"google.golang.org/grpc/metadata"
    23  	"google.golang.org/grpc/status"
    24  )
    25  
    26  // chanServerStream implements grpc.ServerStream with a chanStream
    27  type chanServerStream struct {
    28  	headerc  chan<- metadata.MD
    29  	trailerc chan<- metadata.MD
    30  	grpc.Stream
    31  
    32  	headers []metadata.MD
    33  }
    34  
    35  func (ss *chanServerStream) SendHeader(md metadata.MD) error {
    36  	if ss.headerc == nil {
    37  		return errAlreadySentHeader
    38  	}
    39  	outmd := make(map[string][]string)
    40  	for _, h := range append(ss.headers, md) {
    41  		for k, v := range h {
    42  			outmd[k] = v
    43  		}
    44  	}
    45  	select {
    46  	case ss.headerc <- outmd:
    47  		ss.headerc = nil
    48  		ss.headers = nil
    49  		return nil
    50  	case <-ss.Context().Done():
    51  	}
    52  	return ss.Context().Err()
    53  }
    54  
    55  func (ss *chanServerStream) SetHeader(md metadata.MD) error {
    56  	if ss.headerc == nil {
    57  		return errAlreadySentHeader
    58  	}
    59  	ss.headers = append(ss.headers, md)
    60  	return nil
    61  }
    62  
    63  func (ss *chanServerStream) SetTrailer(md metadata.MD) {
    64  	ss.trailerc <- md
    65  }
    66  
    67  // chanClientStream implements grpc.ClientStream with a chanStream
    68  type chanClientStream struct {
    69  	headerc  <-chan metadata.MD
    70  	trailerc <-chan metadata.MD
    71  	*chanStream
    72  }
    73  
    74  func (cs *chanClientStream) Header() (metadata.MD, error) {
    75  	select {
    76  	case md := <-cs.headerc:
    77  		return md, nil
    78  	case <-cs.Context().Done():
    79  	}
    80  	return nil, cs.Context().Err()
    81  }
    82  
    83  func (cs *chanClientStream) Trailer() metadata.MD {
    84  	select {
    85  	case md := <-cs.trailerc:
    86  		return md
    87  	case <-cs.Context().Done():
    88  		return nil
    89  	}
    90  }
    91  
    92  func (cs *chanClientStream) CloseSend() error {
    93  	close(cs.chanStream.sendc)
    94  	return nil
    95  }
    96  
    97  // chanStream implements grpc.Stream using channels
    98  type chanStream struct {
    99  	recvc  <-chan interface{}
   100  	sendc  chan<- interface{}
   101  	ctx    context.Context
   102  	cancel context.CancelFunc
   103  }
   104  
   105  func (s *chanStream) Context() context.Context { return s.ctx }
   106  
   107  func (s *chanStream) SendMsg(m interface{}) error {
   108  	select {
   109  	case s.sendc <- m:
   110  		if err, ok := m.(error); ok {
   111  			return err
   112  		}
   113  		return nil
   114  	case <-s.ctx.Done():
   115  	}
   116  	return s.ctx.Err()
   117  }
   118  
   119  func (s *chanStream) RecvMsg(m interface{}) error {
   120  	v := m.(*interface{})
   121  	for {
   122  		select {
   123  		case msg, ok := <-s.recvc:
   124  			if !ok {
   125  				return status.Error(codes.Canceled, "the client connection is closing")
   126  			}
   127  			if err, ok := msg.(error); ok {
   128  				return err
   129  			}
   130  			*v = msg
   131  			return nil
   132  		case <-s.ctx.Done():
   133  		}
   134  		if len(s.recvc) == 0 {
   135  			// prioritize any pending recv messages over canceled context
   136  			break
   137  		}
   138  	}
   139  	return s.ctx.Err()
   140  }
   141  
   142  func newPipeStream(ctx context.Context, ssHandler func(chanServerStream) error) chanClientStream {
   143  	// ch1 is buffered so server can send error on close
   144  	ch1, ch2 := make(chan interface{}, 1), make(chan interface{})
   145  	headerc, trailerc := make(chan metadata.MD, 1), make(chan metadata.MD, 1)
   146  
   147  	cctx, ccancel := context.WithCancel(ctx)
   148  	cli := &chanStream{recvc: ch1, sendc: ch2, ctx: cctx, cancel: ccancel}
   149  	cs := chanClientStream{headerc, trailerc, cli}
   150  
   151  	sctx, scancel := context.WithCancel(ctx)
   152  	srv := &chanStream{recvc: ch2, sendc: ch1, ctx: sctx, cancel: scancel}
   153  	ss := chanServerStream{headerc, trailerc, srv, nil}
   154  
   155  	go func() {
   156  		if err := ssHandler(ss); err != nil {
   157  			select {
   158  			case srv.sendc <- err:
   159  			case <-sctx.Done():
   160  			case <-cctx.Done():
   161  			}
   162  		}
   163  		scancel()
   164  		ccancel()
   165  	}()
   166  	return cs
   167  }
   168
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