Lightweight HTTP1&2 Protocol to avoid direct depend on grpc-go library.

[chickenlj]

According to the Dubbo3 architecture, Triple protocol should be defined as a slim HTTP-based protocol for building browser and gRPC-compatible, high-performance web and rpc services.

With the above goal in mind, the Triple implementation in Dubbo-go should be able to do the following:

• Communicate with original gRPC servers seamlessly.
• Being able to be consumed by the browser directly
• Can be easily integrated with all kinds of Dubbo features such as Filter, Router, Registry, etc. with low maintenance efforts and good user experience.
• Lightweight enough with only a few hundred or thousands of lines of code.
• Introduce as less third-party libraries as possible.
• Generated stub should have a gopher-friendly programming API.

But the current implementation is still far away or even impossible to meet those requirements. The current implementation depends directly on grpc-go library to fulfill data exchange purpose and is a way proven to have many drawbacks:

• Hard to integrate with the extensions and features defined by Dubbo.
• Hard to upgrade the grpc-go library since the new version might bring breaking changes.
• The whole grpc-go binary package is introduced in the dependency tree but only the RPC protocol part is used.
• It's hard to support HTTP based programming model directly on grpc-go, so the only option is proxy-based grpc-web.
• We have our own stub generator which has nothing to do with protoc-gen-grpc.

So, I think we should provide our lightweight HTTP/2 rpc protocol implementation, and to achieve that, a very similar one provided by Buf Connect Go can be a very good reference to start.

[AlexStocks]

这个工作建议跟李志信沟通下，知道下当年选用 grpc-go 的背景，然后再讨论。

[chickenlj]

这个工作建议跟李志信沟通下，知道下当年选用 grpc-go 的背景，然后再讨论。

Actually, we had a brief discussion and reached the above conclusion. So let's see what others think about it.

[pyh4]

@chickenlj Hi, there! I am a graduate student in software engineering at Zhejiang University. I have experience in Golang. I have contributed to open source project before and I am interested in this issue.

I have gone through the details and here are my understandings of the issue:

• Triple protocol is based on HTTP/2 + gRPC and is fully compatible with gRPC over HTTP/2.
• dubbo-go is currently using grpc-go to fulfill data exchange and leads to many drawbacks.
• Implement a lightweight HTTP/2 RPC protocol instead of introducing grpc-go as a dependency.
• Refer to protocol "Connect" in bufbuild/connect-go, which works over HTTP/2.

Any further advice and guidance would be appreciated.

[106umao]

I am very interested in this issue and will submit a proposal. I look forward to further communicating with the community about this issue.

[DMwangnima]

Temporary triple design documentation：

Triple-go

设计目标

1. 在完全兼容Grpc，保证与老应用正常通信的基础上，支持h1和h2下采用curl，浏览器等web方式直接访问服务，无需任何配置
2. 剥除对grpc-go的依赖，使用net/http
3. 保持 编写IDL文件->protoc编译自动生成stub代码->实现业务逻辑 的工作模式，stub代码结构与接口向Grpc靠近(暂定)

设计细节

组成

Rest + Grpc，服务端在单端口上同时支持这两种协议，客户端由用户选择调用方式，默认为Grpc

协议区分

统一进入ServeHTTP(responseWriter http.ResponseWriter, request *http.Request)后，

POST/GET? + content-type: application/ -> Rest

POST + content-type: application/grpc -> Grpc

Rest

1. 额外Header: triple-timeout-ms, triple-version

2. rpc错误信息: json编码的Error

   type WireError struct {
      Code    Code                 `json:"code"`
      Message string               `json:"message,omitempty"`
      // google.golang.org/genproto/googleapis/rpc/errdetails
      Details []*ErrorDetail       `json:"details,omitempty"`
   }
   

3. Triple Error Code与HTTP Code映射:

   switch code {
   case CodeCanceled:
      return 408
   case CodeUnknown:
      return 500
   case CodeInvalidArgument:
      return 400
   case CodeDeadlineExceeded:
      return 408
   case CodeNotFound:
      return 404
   case CodeAlreadyExists:
      return 409
   case CodePermissionDenied:
      return 403
   case CodeResourceExhausted:
      return 429
   case CodeFailedPrecondition:
      return 412
   case CodeAborted:
      return 409
   case CodeOutOfRange:
      return 400
   case CodeUnimplemented:
      return 404
   case CodeInternal:
      return 500
   case CodeUnavailable:
      return 503
   case CodeDataLoss:
      return 500
   case CodeUnauthenticated:
      return 401
   

4. GET query params(ignore)

   triple=v1 // 协议版本

   encoding=json //编码方式，等同于content-type

   message=... //编码后的请求参数，还需要经过base64序列化

   compression=gzip //压缩方式，等同于content-encoding

   eg:

   GET /buf.greet.v1.GreetService/Greet?triple=v1&encoding=json&msg=%7B%22name%22%3A%22Buf%22%7D HTTP/1.1 Host: demo.connect.build

   < HTTP/1.1 200 OK < Content-Type: application/json < < {"greeting": "Hello, Buf!"}

5. 只支持unary，不支持stream

6. 对于具有幂等性的调用，才支持GET(ignore)

Grpc

1. 参照https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md进行实现，完全使用net/http
2. 需要性能测试得出与grpc-go的具体差距
3. 需要cross-test，triple client -> grpc-go server, grpc-go client -> triple server，可考虑新起一个项目保证triple本身足够轻量

protoc-gen-triple-go

1. 为了兼容dubbo-go，引入ClientImpl和ProviderBase

   对于用户端，var cli = new(ClientImpl);config.SetConsumerService(cli);config.Load()后直接使用cli即可

   对于服务端，用户编写的struct需要wrap一下ProviderBase

2. 目前triple-go和protoc-gen-triple-go为泛型版本，需要考虑是否更改为非泛型版本。对于用户来说，除了版本升级问题，接口处的请求参数也需要NewRequest wrap一下。