presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/AssignmentLimiter.java/AssignmentLimiter/clearOnlineNodes
class AssignmentLimiter:    private void clearOnlineNodes()
    {
        Set<String> onlineNodes = nodeSupplier.getWorkerNodes().stream()
                .map(Node::getNodeIdentifier)
                .collect(toSet());

        synchronized (this) {
            delayedNodes.keySet().removeAll(onlineNodes);
            offlineNodes.removeAll(onlineNodes);
        }
    }