RPC vs Http
在评估 4G SDK 方案中，嵌入同事方案中使用 RPC 方案与服务器通信，让我感觉很奇怪，因为在我们的 web server 里通信一般都是 https 通信方式。
RPC
wikipedia’s List of network protocols (OSI model)
RPC 属于 Session Layer,
HTTP vs RPC
rpc 是远端过程调用，其调用协议通常包含传输协议和序列化协议。
传输协议包含：如著名的 [gRPC](grpc / grpc.io) 使用的 http2 协议，也有如 dubbo 一类的自定义报文的 tcp 协议。 序列化协议包含：如基于文本编码的 xml json，也有二进制编码的 protobuf hessian 等。
HTTP 长连接
在参考[2] 中提到 httpServer 怎么处理长连接的： httpServer 创建一个 goroutine，更确切的说，是为了为一个新的 tcp 连接去创建一个 goroutine， 详细参考文章的源码。
Compare gRPC services with HTTP APIs
gRPC is designed for HTTP/2, vs HTTP 1.x:
- binary framing and compression.
- Multiplexing of multiple HTTP/2 calls over a single TCP connection. Multiplexing eliminates head-of-line-blocking
| Feature | gRPC | HTTP APIs with JSON |
|---|---|---|
| Contract | Required (.proto) |
Optional (OpenAPI) |
| Protocol | HTTP/2 | HTTP |
| Payload | Protobuf (small, binary) | JSON (large, human readable) |
| Prescriptiveness | Strict specification | Loose. Any HTTP is valid. |
| Streaming | Client, server, bi-directional | Client, server |
| Browser support | No (requires grpc-web) | Yes |
| Security | Transport (TLS) | Transport (TLS) |
| Client code-generation | Yes | OpenAPI + third-party tooling |
表格来自 https://docs.microsoft.com/en-us/aspnet/core/grpc/comparison
Head-of-line Blocking
详细描述了HOL https://engineering.cred.club/head-of-line-hol-blocking-in-http-1-and-http-2-50b24e9e3372
Key Points:
- Frame
- Message
- Stream
The HOL Blocking issue is resolved at the HTTP layer in HTTP/2, but it now moves to the TCP layer.
HTTP/3 or QUIC solves HOL Blocking at TCP layer by leveraging UDP instead of TCP as the transport protocol.
参考
-
既然有 http，为什么还要 RPC 调用？ https://www.zhihu.com/question/41609070
-
Golang httpServer 对 KeepAlive 长连接的处理方式 https://blog.csdn.net/jeffrey11223/article/details/81222774