draft
check cluster health
endpoint=http://localhost:9200 curl -i "$endpoint/_cluster/health?pretty" -u $user:$passwd
look for existing indices
curl "http://localhost:9200/_cat/indices?v"
https://www.elastic.co/guide/en/elastic-stack-overview/index.html old doc (6.3 - 7.4)
https://www.elastic.co/guide/en/elasticsearch/reference/index.html new doc