http-proxy-with-in-ram-cache.go

package main

import (
	"log"
	"fmt"
	"encoding/json"
	"github.com/valyala/fasthttp"
)

var (
	proxyClient = &fasthttp.HostClient{
		Addr: "cdimage.debian.org:80",
	}
	storage = make(map[string]*fasthttp.Response)
)

func ReverseProxyHandler(ctx *fasthttp.RequestCtx) {
	req := &ctx.Request
	resp := &ctx.Response
	path := string(ctx.Request.URI().Path())
	
	if path == "/stats" {
		storageDump := make(map[string]int)
		for k, v := range storage {
			storageDump[k] = len(v.Body())
		}
		j, je := json.Marshal(storageDump)
		if je == nil {
			fmt.Fprintf(ctx, string(j))
		}
		return
	}
	
	_, exist := storage[path]
	if !exist {
		ctx.Logger().Printf("request")
		if err := proxyClient.Do(req, resp); err != nil {
			ctx.Logger().Printf("error when proxying the request: %s", err)
		}
		storage[path] = &fasthttp.Response{}
		resp.CopyTo(storage[path])
	}
	storage[path].CopyTo(resp)
}

func main() {
	if err := fasthttp.ListenAndServe(":8080", ReverseProxyHandler); err != nil {
		log.Fatalf("error in fasthttp server: %s", err)
	}
}