fix: prevent service degradation on config reload failure

main.go

@@ -299,12 +299,26 @@ func proxyConfigChanged(cfgCp *config.ConnectionPool, rp *reverseProxy) bool {
 }
 
 func applyConfig(cfg *config.Config) error {
-	if proxy == nil || proxyConfigChanged(&cfg.ConnectionPool, proxy) {
-		proxy = newReverseProxy(&cfg.ConnectionPool)
-	}
-	if err := proxy.applyConfig(cfg); err != nil {
-		return err
+	needNewProxy := proxy == nil || proxyConfigChanged(&cfg.ConnectionPool, proxy)
+
+	if needNewProxy {
+		newProxy := newReverseProxy(&cfg.ConnectionPool)
+		if err := newProxy.applyConfig(cfg); err != nil {
+			close(newProxy.reloadSignal)
+			newProxy.reloadWG.Wait()
+			return err
+		}
+		if proxy != nil {
+			close(proxy.reloadSignal)
+			proxy.reloadWG.Wait()
+		}
+		proxy = newProxy
+	} else {
+		if err := proxy.applyConfig(cfg); err != nil {
+			return err
+		}
 	}
+
 	allowedNetworksHTTP.Store(&cfg.Server.HTTP.AllowedNetworks)
 	allowedNetworksHTTPS.Store(&cfg.Server.HTTPS.AllowedNetworks)
 	allowedNetworksMetrics.Store(&cfg.Server.Metrics.AllowedNetworks)

proxy.go

@@ -78,7 +78,7 @@ func newReverseProxy(cfgCp *config.ConnectionPool) *reverseProxy {
 		},
 		reloadSignal:        make(chan struct{}),
 		reloadWG:            sync.WaitGroup{},
-		maxIdleConns:        cfgCp.MaxIdleConnsPerHost,
+		maxIdleConns:        cfgCp.MaxIdleConns,
 		maxIdleConnsPerHost: cfgCp.MaxIdleConnsPerHost,
 	}
 }