Keba: fix race in listener (#7495)

charger/keba.go

@@ -75,12 +75,9 @@ func NewKebaFromConfig(other map[string]interface{}) (api.Charger, error) {
 func NewKeba(uri, serial string, rfid RFID, timeout time.Duration) (*Keba, error) {
 	log := util.NewLogger("keba")
 
-	if keba.Instance == nil {
-		var err error
-		keba.Instance, err = keba.New(log)
-		if err != nil {
-			return nil, err
-		}
+	instance, err := keba.Instance(log)
+	if err != nil {
+		return nil, err
 	}
 
 	// add default port
@@ -101,7 +98,7 @@ func NewKeba(uri, serial string, rfid RFID, timeout time.Duration) (*Keba, error
 		serial = conn
 	}
 
-	keba.Instance.Subscribe(serial, c.recv)
+	instance.Subscribe(serial, c.recv)
 
 	return c, err
 }

charger/keba/listener.go

@@ -23,9 +23,12 @@ const (
 	Any = "<any>"
 )
 
-// Instance is the KEBA listener instance
+// instance is the KEBA listener instance
 // This is needed since KEBAs ignore the sender port and always UDP back to port 7090
-var Instance *Listener
+var (
+	mu       sync.Mutex
+	instance *Listener
+)
 
 // UDPMsg transports the KEBA response. Report is any of Report1,2,3
 type UDPMsg struct {
@@ -43,6 +46,18 @@ type Listener struct {
 	cache   map[string]string
 }
 
+func Instance(log *util.Logger) (*Listener, error) {
+	mu.Lock()
+	defer mu.Unlock()
+
+	var err error
+	if instance == nil {
+		instance, err = New(log)
+	}
+
+	return instance, err
+}
+
 // New creates a UDP listener that clients can subscribe to
 func New(log *util.Logger) (*Listener, error) {
 	laddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf(":%d", Port))