Another solution is to have them share an s3 key and have 'client' nodes write a file like <s3>/private_dir/client.192.168.1.1 a controller node recognises them

Another solution is to have them share an s3 key and have 'client' nodes write a file like <s3>/private_dir/client.192.168.1.1 a controller node recognises them and issues work.