正常关闭gRPC下游_course

<div class="post-text" itemprop="text"> <p>Using the following proto buffer code :</p> <pre><code>syntax = "proto3"; package pb; message SimpleRequest { int64 number = 1; } message SimpleResponse { int64 doubled = 1; } // All the calls in this serivce preform the action of doubling a number. // The streams will continuously send the next double, eg. 1, 2, 4, 8, 16. service Test { // This RPC streams from the server only. rpc Downstream(SimpleRequest) returns (stream SimpleResponse); } </code></pre> <p>I'm able to successfully open a stream, and continuously get the next doubled number from the server.</p> <p>My go code for running this looks like :</p> <pre><code>ctxDownstream, cancel := context.WithCancel(ctx) downstream, err := testClient.Downstream(ctxDownstream, &amp;pb.SimpleRequest{Number: 1}) for { responseDownstream, err := downstream.Recv() if err != io.EOF { println(fmt.Sprintf("downstream response: %d, error: %v", responseDownstream.Doubled, err)) if responseDownstream.Doubled &gt;= 32 { break } } } cancel() // !!This is not a graceful shutdown println(fmt.Sprintf("%v", downstream.Trailer())) </code></pre> <p>The problem I'm having is using a context cancellation means my downstream.Trailer() response is empty. Is there a way to gracefully close this connection from the client side and receive downstream.Trailer().</p> <p>Note: if I close the downstream connection from the server side, my trailers are populated. But I have no way of instructing my server side to close this particular stream. So there must be a way to gracefully close a stream client side.</p> <p>Thanks.</p> <p>As requested some server code : </p> <pre><code>func (b *binding) Downstream(req *pb.SimpleRequest, stream pb.Test_DownstreamServer) error { request := req r := make(chan *pb.SimpleResponse) e := make(chan error) ticker := time.NewTicker(200 * time.Millisecond) defer func() { ticker.Stop(); close(r); close(e) }() go func() { defer func() { recover() }() for { select { case &lt;-ticker.C: response, err := b.Endpoint(stream.Context(), request) if err != nil { e &lt;- err } r &lt;- response } } }() for { select { case err := &lt;-e: return err case response := &lt;-r: if err := stream.Send(response); err != nil { return err } request.Number = response.Doubled case &lt;-stream.Context().Done(): return nil } } } </code></pre> <p>You will still need to populate the trailer with some information. I use the grpc.StreamServerInterceptor to do this.</p> </div>