allocate local port dynamically, fixes #290 (#292)

config/config.go

@@ -93,6 +93,7 @@ type Config struct {
 
 	FileName string `toml:"-"`
 
+	// Addr can be empty to assign a local address dynamically
 	Addr string `toml:"addr"`
 
 	AddrUnixSocketPerm string `toml:"addr_unixsocketperm"`
@@ -136,13 +137,14 @@ func NewConfigWithFile(fileName string) (*Config, error) {
 		return nil, err
 	}
 
-	if cfg, err := NewConfigWithData(data); err != nil {
+	cfg, err := NewConfigWithData(data)
+	if err != nil {
 		return nil, err
-	} else {
+	}
+
 	cfg.FileName = fileName
 	return cfg, nil
 }
-}
 
 func NewConfigWithData(data []byte) (*Config, error) {
 	cfg := NewConfigDefault()
@@ -203,9 +205,9 @@ func NewConfigDefault() *Config {
 func getDefault(d int, s int) int {
 	if s <= 0 {
 		return d
-	} else {
-		return s
 	}
+
+	return s
 }
 
 func (cfg *Config) adjust() {

server/app.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"fmt"
 	"net"
 	"net/http"
 	"os"
@@ -55,9 +56,9 @@ type App struct {
 func netType(s string) string {
 	if strings.Contains(s, "/") {
 		return "unix"
-	} else {
-		return "tcp"
 	}
+
+	return "tcp"
 }
 
 func NewApp(cfg *config.Config) (*App, error) {
@@ -88,6 +89,7 @@ func NewApp(cfg *config.Config) (*App, error) {
 		return nil, err
 	}
 
+	if cfg.Addr != "" {
 		addrNetType := netType(cfg.Addr)
 
 		if app.listener, err = net.Listen(addrNetType, cfg.Addr); err != nil {
@@ -103,6 +105,14 @@ func NewApp(cfg *config.Config) (*App, error) {
 				return nil, err
 			}
 		}
+	} else {
+		app.listener, err = net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			if app.listener, err = net.Listen("tcp6", "[::1]:0"); err != nil {
+				return nil, fmt.Errorf("app: failed to listen on a port: %v", err)
+			}
+		}
+	}
 
 	if len(cfg.HttpAddr) > 0 {
 		if app.httpListener, err = net.Listen(netType(cfg.HttpAddr), cfg.HttpAddr); err != nil {
@@ -227,3 +237,7 @@ func (app *App) httpServe() {
 func (app *App) Ledis() *ledis.Ledis {
 	return app.ldb
 }
+
+func (app *App) Address() string {
+	return app.listener.Addr().String()
+}