Created by: reyoung

Make paddle support using protobuf 3.0+ library, and capatiable to proto2.

Maybe we should update protobuf to 3.0+, because

• one_of & map is very good to passing layer attributes.

message Attribute {
one_of {
   bool bVal;
   int iVal;
   real rVal;
   string sVal;
}
}

message LayerConfig {
   map<string, Attribute> ExtraAttributes; 
}

• gRPC is only supported protobuf3

  • http://stackoverflow.com/questions/33986339/encountering-remote-error-using-grpc-with-protobuf2-6-in-python
  • To refactor currently PServer/PClient, or even only to make paddle as a RPC service, gRPC is a very good choice. Because it use http/2, and support ssl by default.
    • http/2's performance is good. ssl can resolve the authentication problems.

• protobuf3 is in production release(v 3.1.0).