I found a community beat https://github.com/radoondas/elasticbeat to grab elasticsearch metrics, I dont understand why there is no an official beat for that?
There is one 
. Metricbeat has an Elasticsearch module, check https://www.elastic.co/guide/en/beats/metricbeat/current/metricbeat-module-elasticsearch.html for more details
Ho! didnt check version 6, thanks you.