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Failed to get RPC descriptor

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Release： 2024-02-08 21:39:09

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获取 RPC 描述符失败

#php editor Strawberry will introduce you to a common problem today: when making a remote procedure call (RPC), you may encounter the error "Failed to obtain RPC descriptor". This error usually means that the client cannot establish a valid connection with the server, which may be caused by network problems, server-side configuration errors, or permission issues. In this article, we will explain the cause of this error in detail and provide some solutions to fix it. Whether you are a beginner or an experienced developer, you will get useful information from this article on resolving the "Failed to get RPC descriptor" error.

Question content

I have the following prototype file:

service_myservice.proto

service MyService {
    rpc GetData(GetRequest) returns (GetResponse) {}
}

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server.go

type Server struct {
    pb.UnimplementedMyServiceServer
    config util.Config
}

// NewServer creates a new gRPC server.
func NewServer(config util.Config) (*Server, error) {
    server := &Server{
        config: config,
    }

    return server, nil
}

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Then I call this function in the main package

func runGrpcServer(config util.Config) {
    server, err := gapi.NewServer(config)
    if err != nil {
        log.Fatal().Err(err).Msg("cannot create server")
    }

    grpcLogger := grpc.UnaryInterceptor(gapi.GrpcLogger)
    grpcServer := grpc.NewServer(grpcLogger)
    pb.RegisterMyServiceServer(grpcServer, server)
    reflection.Register(grpcServer)

    listener, err := net.Listen("tcp", config.GRPCServerAddress)
    if err != nil {
        log.Fatal().Err(err).Msg("cannot create listener")
    }

    log.Info().Msgf("start gRPC server at %s", listener.Addr().String())
    err = grpcServer.Serve(listener)
    if err != nil {
        log.Fatal().Err(err).Msg("cannot start gRPC server")
    }
}

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I'm using evans (https://github.com/ktr0731/evans) to test my grpc calls. My gRPC server is running and I can use evans to connect to localhost on a specific port (9090).

However, when I call show service in Evans, I get the following response:

localhost:9090> show service
+---------+-----+--------------+---------------+
| SERVICE | RPC | REQUEST TYPE | RESPONSE TYPE |
+---------+-----+--------------+---------------+
+---------+-----+--------------+---------------+
localhost:9090> call GetData
command call: failed to get the RPC descriptor for: GetData: service unselected

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I think if I add pb.UnimplementedMyServiceServer in the Server structure, then this is forward compatible. But obviously, I'm missing some code.

What parts are missing to make MyService forward compatible?

Solution

REPLWhen using evans in mode, you should select the package and call ## before calling show service Service should be selected before #call GetData.

localhost:9090> show package
+-------------------------+
|         PACKAGE         |
+-------------------------+
| example                 |
| grpc.reflection.v1      |
| grpc.reflection.v1alpha |
+-------------------------+

localhost:9090> package example

example@localhost:9090> show service
+-----------+---------+--------------+---------------+
|  SERVICE  |   RPC   | REQUEST TYPE | RESPONSE TYPE |
+-----------+---------+--------------+---------------+
| MyService | GetData | GetRequest   | GetResponse   |
+-----------+---------+--------------+---------------+

example@localhost:9090> service MyService

example.MyService@localhost:9090> call GetData
id (TYPE_INT32) => 1

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