An idea for framing gRPC requests from JavaScript WebSockets to a generic proxy.

framing.proto

syntax = "proto3";

option go_package = "proxy";

// Frames an API request message.
//
// Each request to the API has a unique stream id per-connection, starting at one.
// This stream id associates all request and response messages for a single request
// together.
//
// The stream id must be included for each frame, and there is a 1:1 relationship
// between frames and request messages. Each frame encapsulates a single, full and
// unsegmented request message.
//
// GRPC calls consist of unary or streaming requests and unary or streaming responses.
// For unary request messages and the first message of a streaming request, the
// service and method names must be set, and the client streams and server streams
// values must be valid. Subsequent request messages for streaming requests should
// not set service or method names, and should not set client streams or server
// streams. The server will ignore those values for subsequent request messages.
// The last request message for a streaming request must set close stream to true.
// Close stream is ignored for unary requests.
message RequestFrame {
	int64 stream_id = 1;
	bytes message = 2;
	string service = 3;
	string method = 4;
	bool client_streams = 5;
	bool server_streams = 6;
	bool close_stream = 7;
}

// Frames API response messages.
//
// The stream id associates each response message with its originating request.
// The stream id must be included for each frame, and there is a 1:1 relationship
// between frames and response messages. Each frame encapsulates a single, full and
// unsegmented response message.
//
// GRPC responses can be unary or streaming. Unary response messages, or the last
// response message for a streaming response, must set status, and can optionally
// set status message. Setting status closes a response stream.
//
// Status is defined as a gRPC status code PLUS ONE. This helps distinguish
// between no status set and GRPC_STATUS_OK.
message ResponseFrame {
	int64 stream_id = 1;
	bytes message = 2;
	int64 status = 3;
	string status_message = 4;
}

// Future support:
//   grpc-timeout (no timeout for now)
//   compression (use WebSocket compression for now)
//   override authority (defaults to WebSocket host)
//   content-type (protobuf only for now)
//   user-agent (defaults to WebSocket header)
//   custom headers (no custom headers for now)