Kraken: Slight improvements to cancelOrders tracking

This just tackles the anonymous type usage, and a few occurrences of pointers not being used efficiently.
Overall the whole pattern needs redoing with a
`SendMessageGatherResponses` in websocket replacing the unencapsulated
map storage we use right now.
For another day ...

exchanges/kraken/kraken_websocket.go

@@ -72,13 +72,15 @@ var defaultSubscribedChannels = []string{
 }
 var authenticatedChannels = []string{krakenWsOwnTrades, krakenWsOpenOrders}
 
-var cancelOrdersStatusMutex sync.Mutex
-var cancelOrdersStatus = make(map[int64]*struct {
+type cancelOrdersStatus struct {
 	Total        int    // total count of orders in wsCancelOrders request
 	Successful   int    // numbers of Successfully canceled orders in wsCancelOrders request
 	Unsuccessful int    // numbers of Unsuccessfully canceled orders in wsCancelOrders request
 	Error        string // if at least one of requested order return fail, store error here
-})
+}
+
+var cancelOrdersTrackersMutex sync.Mutex
+var cancelOrdersTracker = make(map[int64]*cancelOrdersStatus)
 
 // WsConnect initiates a websocket connection
 func (k *Kraken) WsConnect() error {
@@ -173,23 +175,22 @@ func (k *Kraken) wsReadData(comms chan stream.Response) {
 	}
 }
 
-// awaitForCancelOrderResponses used to wait until all responses will received for appropriate CancelOrder request
-// success param = was the response from Kraken successful or not
+// isAwaitingCancelOrderResponses adds to the status tracker for a cancelOrders request
+// returns true if there are more cancel responses due
 func isAwaitingCancelOrderResponses(requestID int64, success bool) bool {
-	cancelOrdersStatusMutex.Lock()
-	if stat, ok := cancelOrdersStatus[requestID]; ok {
+	cancelOrdersTrackersMutex.Lock()
+	defer cancelOrdersTrackersMutex.Unlock()
+	if s, ok := cancelOrdersTracker[requestID]; ok {
 		if success {
-			cancelOrdersStatus[requestID].Successful++
+			s.Successful++
 		} else {
-			cancelOrdersStatus[requestID].Unsuccessful++
+			s.Unsuccessful++
 		}
 
-		if stat.Successful+stat.Unsuccessful != stat.Total {
-			cancelOrdersStatusMutex.Unlock()
+		if s.Successful+s.Unsuccessful != s.Total {
 			return true
 		}
 	}
-	cancelOrdersStatusMutex.Unlock()
 	return false
 }
 
@@ -256,13 +257,13 @@ func (k *Kraken) wsHandleData(respRaw []byte) error {
 		success := true
 		if status.Status == "error" {
 			success = false
-			cancelOrdersStatusMutex.Lock()
-			if _, ok := cancelOrdersStatus[status.RequestID]; ok {
-				if cancelOrdersStatus[status.RequestID].Error == "" { // save the first error, if any
-					cancelOrdersStatus[status.RequestID].Error = status.ErrorMessage
+			cancelOrdersTrackersMutex.Lock()
+			if s, ok := cancelOrdersTracker[status.RequestID]; ok {
+				if s.Error == "" { // save the first error, if any
+					s.Error = status.ErrorMessage
 				}
 			}
-			cancelOrdersStatusMutex.Unlock()
+			cancelOrdersTrackersMutex.Unlock()
 		}
 
 		if isAwaitingCancelOrderResponses(status.RequestID, success) {
@@ -1374,28 +1375,21 @@ func (k *Kraken) wsCancelOrders(orderIDs []string) error {
 		RequestID:      id,
 	}
 
-	cancelOrdersStatus[id] = &struct {
-		Total        int
-		Successful   int
-		Unsuccessful int
-		Error        string
-	}{
-		Total: len(orderIDs),
-	}
+	cancelOrdersTracker[id] = &cancelOrdersStatus{Total: len(orderIDs)}
 
-	defer delete(cancelOrdersStatus, id)
+	defer delete(cancelOrdersTracker, id)
 
 	_, err := k.Websocket.AuthConn.SendMessageReturnResponse(id, request)
 	if err != nil {
 		return err
 	}
 
-	successful := cancelOrdersStatus[id].Successful
+	successful := cancelOrdersTracker[id].Successful
 
-	if cancelOrdersStatus[id].Error != "" || len(orderIDs) != successful { // strange Kraken logic ...
+	if cancelOrdersTracker[id].Error != "" || len(orderIDs) != successful { // strange Kraken logic ...
 		var reason string
-		if cancelOrdersStatus[id].Error != "" {
-			reason = fmt.Sprintf(" Reason: %s", cancelOrdersStatus[id].Error)
+		if cancelOrdersTracker[id].Error != "" {
+			reason = fmt.Sprintf(" Reason: %s", cancelOrdersTracker[id].Error)
 		}
 		return fmt.Errorf("%s cancelled %d out of %d orders.%s",
 			k.Name, successful, len(orderIDs), reason)