在C++中如何在错误时中止gRPC流并指出错误

Question

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如果发生客户端错误，我将如何中止此序列，并向服务器指示这一点？

Answer 1

您需要执行一个client_context.trycancel()，后跟一个Finish（）。在https://github.com/grpc/grpc/blob/master/test/cpp/end2end/end2end_test.cc，ClientCancelsRequestStream中有一些例子。我对它进行了修改，使其看起来更接近您的代码。

RequestType request;
ResponseType response;
ClientContext context;
request.set_message("hello");

auto client_writer = stub_->YourRPC(&context, &response);
client_writer->Write(request);
client_writer->Write(request);

client_context.TryCancel();

Status s = client_writer->Finish();

如果取消成功，则s.error_code()==GRPC::StatusCode::Canceled。

以下是grpc存储库中client_context.h中clientContext::tryCancel()的注释：

/// Send a best-effort out-of-band cancel on the call associated with
/// this client context.  The call could be in any stage; e.g., if it is
/// already finished, it may still return success.
///
/// There is no guarantee the call will be cancelled.