Check duplicate external labels for all stores included existed store (…

…#1157)

When we change the external labels after store has already joined into
storesets that will makes the external labels duplicated

Check duplicate external labels before checking whether the store is exist or not

pkg/query/storeset.go

@@ -236,11 +236,6 @@ func (s *StoreSet) Update(ctx context.Context) {
 
 	// Add stores that are not yet in s.stores.
 	for addr, store := range healthyStores {
-		if _, ok := s.stores[addr]; ok {
-			s.updateStoreStatus(store, nil)
-			continue
-		}
-
 		// Check if it has some external labels specified.
 		// No external labels means strictly store gateway or ruler and it is fine to have access to multiple instances of them.
 		//
@@ -252,6 +247,11 @@ func (s *StoreSet) Update(ctx context.Context) {
 			continue
 		}
 
+		if _, ok := s.stores[addr]; ok {
+			s.updateStoreStatus(store, nil)
+			continue
+		}
+
 		s.stores[addr] = store
 		s.updateStoreStatus(store, nil)
 		level.Info(s.logger).Log("msg", "adding new store to query storeset", "address", addr)