proxy.go

package main

import (
	"bufio"
	"encoding/json"
	"flag"
	"fmt"
	"github.com/gorilla/mux"
	"log"
	"net/http"
	"net/http/httputil"
	"net/url"
	"os"
	"runtime"
)

var configFile = flag.String("f", "proxy.json", "config file to parse")

type Config struct {
	Listen string
	Sites  map[string][]string
}

func init() {
	runtime.GOMAXPROCS(runtime.NumCPU())
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
		flag.PrintDefaults()
	}
	flag.Parse()
}

func main() {
	f, _ := os.Open(*configFile)
	dec := json.NewDecoder(bufio.NewReader(f))

	var config Config

	if err := dec.Decode(&config); err != nil {
		log.Fatal(err)
	}

	r := mux.NewRouter()

	for site := range config.Sites {
		u, _ := url.Parse(site)
		p := httputil.NewSingleHostReverseProxy(u)
		for _, domain := range config.Sites[site] {
			r.NewRoute().Host(domain).Handler(p)
		}
	}

	log.Fatal(http.ListenAndServe(config.Listen, r))
}