MCP Streamable HTTP 传输层的深度解析及实战分析

一、Streamable HTTP 传输层设计革新

1. 核心设计思想

• 协议融合：将 HTTP/1.1、HTTP/2 与 SSE 协议特性深度整合
• 动态协商：通过 HTTP Header 实现传输协议动态协商（X-MCP-Transport）
• 流式优先：默认启用流式传输，支持半双工通信
• 背压控制：基于 HTTP/2 流级流量控制实现智能速率调节

2. 与传统 HTTP+SSE 的对比

3. 协议栈架构

+----------------+     +-------------------+     +------------------+
|  Application    |     |   Streamable      |     |    HTTP/2        |
|  Layer (MCP)    |<----|  HTTP Transport   |<----|   Multiplexing   |
|                 |     |   Layer           |     | (可选)          |
+----------------+     +-------------------+     +------------------+
          |                      |                      |
          |  JSON Events         |  Binary Frames       |
          v                      v                      v
+----------------+     +-------------------+     +------------------+
|   TLS 1.3      |     |   HTTP/1.1        |     |   QUIC           |
+----------------+     +-------------------+     +------------------+

二、Spring AI Alibaba Streamable HTTP 实现

1. 核心组件架构

2. 关键代码实现

(1) 请求处理适配器

public class StreamableRequestAdapter {
   
    private final TransportMode transportMode;
    private final Decoder decoder;
    private final Encoder encoder;

    public StreamableRequestAdapter(MCPRequest request) {
   
        this.transportMode = determineTransportMode(request);
        this.decoder = createDecoder(transportMode);
        this.encoder = createEncoder(transportMode);
    }

    private TransportMode determineTransportMode(MCPRequest request) {
   
        if (request.getHeader("X-MCP-Transport").equals("binary")) {
   
            return TransportMode.HTTP2;
        }
        return request.getBodySize() > 1024 * 1024 ? TransportMode.SSE : TransportMode.JSON;
    }
}

(2) 流式响应处理器

@RestController
@RequestMapping("/mcp/v1")
public class MCPController {
   
    
    @PostMapping("/execute")
    public void executeCommand(
        @RequestBody MCPRequest request,
        HttpServletResponse response) {
   
        
        // 流式传输检测
        boolean isStreamable = request.getHeader("Accept-Stream")
            .contains("text/event-stream");
        
        StreamableResponseWriter writer = new StreamableResponseWriter(response);
        writer.setContentType(isStreamable ? "text/event-stream" : "application/json");
        
        // 执行流式处理
        try (StreamableContext ctx = new StreamableContext(request, writer)) {
   
            executeTool(ctx);
        }
    }

    private void executeTool(StreamableContext ctx) {
   
        // 模拟流式响应
        for (int i = 0; i < 5; i++) {
   
            ctx.writeEvent(new MCPEvent()
                .setStreamId(UUID.randomUUID().toString())
                .setChunk("Processing chunk " + i));
        }
        ctx.complete();
    }
}

3. Spring Boot 配置

spring:
  ai:
    mcp:
      transport:
        mode: AUTO
        http2:
          enabled: true
          max-concurrent-streams: 512
        sse:
          chunk-size: 1024
          reconnect-interval: 5000
      security:
        enabled: true
        token: ${
   MCP_TOKEN:default-secret}

三、Higress 集成方案

1. 核心网关配置

http {
    stream {
        server {
            listen 8080;
            proxy_pass backend_servers;
            proxy_protocol on;
            proxy_http_version 2;
        }
    }

    server {
        listen 8081 http2;
        location /mcp/v1 {
            proxy_pass http://mcp-service;
            proxy_set_header X-MCP-Transport $http_x_mcp_transport;
            proxy_http_version 2;
            
            # 流式传输优化
            proxy_request_buffering off;
            proxy_buffering off;
            proxy_chunked_transfer_encoding on;
            
            # 安全策略
            proxy_set_header Authorization $http_authorization;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        }
    }
}

2. WASM 智能路由模块

// higress-plugin.js
module.exports = {
   
    name: 'mcp-stream-optimizer',
    version: '1.0.0',
    async requestReceived(context) {
   
        const request = context.getRequest();
        const headers = request.getHeaders();
        
        // 流式传输检测逻辑
        if (headers['x-mcp-stream'] === 'required' && 
            headers['content-type'] === 'application/octet-stream') {
   
            
            // 强制启用 HTTP/2
            context.setTransportProtocol('h2');
            context.setResponseHeader('X-MCP-Transport', 'binary');
        }
    }
};