https://www.elastic.co/guide/en/elasticsearch/guide/current/near-real-time.html
https://www.elastic.co/guide/en/elasticsearch/reference/1.4/_modifying_your_data.html
https://www.elastic.co/guide/en/elasticsearch/reference/5.0/docs-refresh.html#docs-refresh
http://stackoverflow.com/questions/31499575/how-to-deal-with-elasticsearch-index-delay
http://stackoverflow.com/questions/38414504/elasticsearch-read-and-write-consistency
http://stackoverflow.com/questions/36458284/elasticsearch-create-update-certain-index-documents-with-strong-consistency