I accidentally deleted all indexes, due to this serious interface flaw of elasticsearch.
I issued a CURL delete request on http://:9200 & all my indexes were lost.
Why would elasticsearch entertain such a destructive request so seamlessly, on the entire cluster ??!!
Then I added:
action.destructive_requires_name: true, mapping in config/elasticsearch.yml & again issued DELETE on a local cluster, & to shame it deleted all indices !! (Guess the config only restricts DELETE request issued on /_all urls)