http://www.aossama.com/search-engine-with-apache-nutch-mongodb-and-elasticsearch/
http://saskia-vola.com/nutch-2-2-elasticsearch-1-x-hbase/
https://qbox.io/blog/scraping-the-web-with-nutch-for-elasticsearch
https://github.com/hunguyen1702/ApacheNutchCourse/wiki/Nutch-2.3.1-Quick-Start
https://github.com/wjhwsh/notes/wiki/Setup-nutch2-and-elasticsearch-on-CentOS-7.2