fix binding issues for monitor (issue #1)

domain/monitor/config.go

@@ -1,6 +1,7 @@
 package monitor
 
 import (
+	"errors"
 	"net"
 	"path/filepath"
 	"strconv"
@@ -40,5 +41,10 @@ func (cfg *Config) Binding() (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return addrs[0].(*net.IPNet).IP.String() + ":" + strconv.Itoa(cfg.Port), nil
+	for _, addr := range addrs {
+		if v, ok := addr.(*net.IPNet); ok && v.IP.IsGlobalUnicast() {
+			return v.IP.String() + ":" + strconv.Itoa(cfg.Port), nil
+		}
+	}
+	return "127.0.0.1:0", errors.New("unable to detect binding address")
 }

domain/monitor/service.go

@@ -17,6 +17,8 @@ import (
 	"time"
 )
 
+const retryInterval = 3 * time.Second
+
 func (cfg Config) CreateAndRun(ctx context.Context) (*service, error) {
 	bind, err := cfg.Binding()
 	if err != nil {
@@ -31,9 +33,22 @@ func (cfg Config) CreateAndRun(ctx context.Context) (*service, error) {
 		cancel:        cancel,
 		events:        cfg.events,
 	}
-	listener, err := net.Listen("tcp", bind)
-	if err != nil {
-		return nil, err
+
+	var listener net.Listener
+
+	for {
+		serverListener, err := net.Listen("tcp", bind)
+		if err != nil {
+			log.Println(err)
+		} else {
+			listener = serverListener
+			break
+		}
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case <-time.After(retryInterval):
+		}
 	}
 	api := srv.createAPI()