least-connected load-balancing, per-host rate-limiting & load from config

config.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"encoding/json"
+	"golang.org/x/time/rate"
+	"io/ioutil"
+	"os"
+	"time"
+)
+
+type HostConfig struct {
+	Every   string            `json:"every"`
+	Burst   int               `json:"burst"`
+	Headers map[string]string `json:"headers"`
+}
+
+type ProxyConfig struct {
+	Name string `json:"name"`
+	Url  string `json:"url"`
+}
+
+var config struct {
+	Addr    string                `json:"addr"`
+	Hosts   map[string]HostConfig `json:"hosts"`
+	Proxies []ProxyConfig         `json:"proxies"`
+}
+
+func loadConfig() {
+
+	configFile, err := os.Open("config.json")
+	handleErr(err)
+
+	configBytes, err := ioutil.ReadAll(configFile)
+	handleErr(err)
+
+	err = json.Unmarshal(configBytes, &config)
+	handleErr(err)
+}
+
+func applyConfig(proxy *Proxy) {
+
+	for host, conf := range config.Hosts {
+		duration, err := time.ParseDuration(conf.Every)
+		handleErr(err)
+		proxy.Limiters.Store(host, rate.NewLimiter(rate.Every(duration), conf.Burst))
+	}
+}
+
+func handleErr(err error) {
+	if err != nil {
+		panic(err)
+	}
+}