c++ - 后台线程中的grpc服务器c++

Question

我正在尝试在 MFC 应用程序的线程中运行 grpc 服务器。

我有(直接来自 GRPC 示例的 grpc 部分):

MyAppDlg.h:

#include <thread>
#include <grpcpp\grpcpp.h>

class MyAppDlg : public CDialog
{
public:
    MyAppDlg( CString aFileName, CWnd *pParent = NULL );
    virtual ~MyAppDlg();

    std::unique_ptr<grpc::Server> grpcServer;

    std::thread grpcThread;

    void RunServer();

MyAppDlg.cpp:

class GreeterServiceImpl final : public Greeter::Service {
    Status SayHello(ServerContext* context, const HelloRequest* request,
        HelloReply* reply) override {
        std::string prefix("Hello ");
        reply->set_message(prefix + request->name());
        return Status::OK;
    }
};

void MyAppDlg::RunServer() {
    std::string server_address("0.0.0.0:50051");
    GreeterServiceImpl service;
    grpc::EnableDefaultHealthCheckService(true);
    grpc::reflection::InitProtoReflectionServerBuilderPlugin();
    ServerBuilder builder;
    builder.AddListeningPort(server_address, grpc::InsecureServerCredentials());
    builder.RegisterService(&service);
    std::unique_ptr<Server> grpcServer(builder.BuildAndStart());
    std::cout << "Server listening on " << server_address << std::endl;

    // Wait for the server to shutdown. Note that some other thread must be
    // responsible for shutting down the server for this call to ever return.
    grpcServer->Wait(); <-- Leaving this out causes the server to close immediately again.
}

MyAppDlg::MyAppDlg( CString aFileName, CWnd* pParent /* =NULL */ )
{
    ... stuff ...
    // RunServer(); <-- using this works but blocks the thread
    grpcThread(RunServer); <-- does not work

}

MyAppDlg::~MyAppDlg()
{
    grpcServer->Shutdown();
    grpcThread.join();
}

没有线程，它运行良好(客户端可以连接并调用 SayHello)，但由于 grpcServer-> 阻塞了 RunServer() 的构造函数等待 () 调用。在线程中尝试，我得到一个编译器错误:call of an object of a class type without appropriate operator() or conversion functions to pointer-to-function type

不调用 grpcServer->Wait() 导致服务器在 RunServer() 退出后立即关闭，尽管变量 grpcServer 仍然存在只要类实例正在运行就在范围内。

如何正确启动 grpcServer 并将其置于后台？

Answer 1

我认为问题出在 MyAppDlg::RunServer() 中的这一行:

std::unique_ptr<Server> grpcServer(builder.BuildAndStart());

您正在定义一个名为 grpcServer 的局部变量，而不是分配给同名的类数据成员，因此它会在 RunServer() 返回。我认为应该是:

grpcServer.reset(builder.BuildAndStart());