presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/DatabaseShardManager.java/DatabaseShardManager/getNodeIdentifiers
class DatabaseShardManager:    private Set<String> getNodeIdentifiers()
    {
        Set<String> nodeIds = nodeSupplier.getWorkerNodes().stream()
                .map(Node::getNodeIdentifier)
                .collect(toSet());
        if (nodeIds.isEmpty()) {
            throw new PrestoException(NO_NODES_AVAILABLE, "No nodes available for bucket assignments");
        }
        return nodeIds;
    }