英文:
Cast request in gRPC interceptor to relevant protobuf message
问题
我有一个UnaryServerInterceptor，它接收一个req的Interface{}。这个req可以是我的任何一个消息，但在这种情况下，我的所有消息都有一个共同的metadata子消息。
Protobuf定义（示例）
message ClientMeta {
string info = 1;
}
message PingRequest {
ClientMeta metadata = 1;
}
message OtherRequest {
ClientMeta metadata = 1;
}
service Blah {
rpc Ping (PingRequest) returns (PingResponse) {}
rpc Other (OtherRequest) returns (OtherResponses) {}
}
拦截器
func (i *authInterceptor) unary() grpc.UnaryServerInterceptor {
return func(
ctx context.Context,
req interface{},
info *grpc.UnaryServerInfo,
handler grpc.UnaryHandler,
) (interface{}, error) {
log.Info().Msgf("interceptor: %s", info.FullMethod)
}
}
我需要在拦截器中访问消息的metadata属性。问题是我不知道它是哪个消息，所以我不能直接进行类型转换。我有几个不同的消息，但它们都有共同的metadata。
有什么最好的方法来解决这个问题？
英文:
I have a UnaryServerInterceptor that receives a req Interface{}. This req could be any one of my messages, but in this case all my messages have a metadata child message in common.
Protobuf definitions (sample)
message ClientMeta {
string info = 1;
}
message PingRequest {
ClientMeta metadata = 1;
}
message OtherRequest {
ClientMeta metadata = 1;
}
service Blah {
rpc Ping (PingRequest) returns (PingResponse) {}
rpc Other (OtherRequest) returns (OtherResponses) {}
}
Interceptor
func (i *authInterceptor) unary() grpc.UnaryServerInterceptor {
return func(
ctx context.Context,
req interface{},
info *grpc.UnaryServerInfo,
handler grpc.UnaryHandler,
) (interface{}, error) {
log.Info().Msgf("interceptor: %s", info.FullMethod)
}
}
I need to access the properties of the message's metadata in my interceptor. The problem is that I don't know which message it is, so I can't just cast it. I have several different messages but they all have metadata in common.
What's the best way to go about this?
答案1
得分: 4
protoc生成的代码应该为两种类型都生成了一个名为GetMetadata的方法。你可以使用类型断言（详见Go之旅）来检查传入的消息是否实现了一个接口，然后调用该方法来获取元数据。
type HasMetadata interface {
GetMetadata() *ClientMeta
}
在处理消息的函数中，可以这样做：
if m, ok := req.(HasMetadata); ok {
return m.GetMetadata()
}
英文:
The protoc generation should have produced a method called GetMetadata for both types. You can check if the incoming message implements an interface using a type assertion (see the tour of go for more details), then call that method to get the metadata.
type HasMetadata interface {
GetMetadata() *ClientMeta
}
In the function that handles the message, do something like this
if m, ok := req.(HasMetadata); ok {
return m.GetMetadata()
}
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