private boolean anotherNodeInGroupAlreadyAllowed(StorageNodeInfo nodeInfo, String newDescription) {
        MutableBoolean alreadyAllowed = new MutableBoolean(false);

        groupVisiting.visit(group -> {
            if (!groupContainsNode(group, nodeInfo.getNode()))
                return true;

            alreadyAllowed.set(anotherNodeInGroupAlreadyAllowed(group, nodeInfo.getNode(), newDescription));

            // Have found the leaf group we were looking for, halt the visiting.
            return false;
        });

        return alreadyAllowed.get();
    }
Returns a disallow-result, if there is a node in the group with wanted state != UP.
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/NodeStateChangeChecker.java