No it’s not documented because it’s an internal API, part of the Kibana plugin support. I’ve not been publicising this much as I don’t want to commit to its stability during time.
But if you feel like using it, who am I to stop you?
Because people have been asking for this, not understanding it, and falling back to writing the “.readonlyrest” index manualy (and making a mess). This is the settings update API:
This REST API is used to update the settings in a running cluster:
POST $ES_URL/_readonlyrest/admin/config
{
"settings": "...JSON escaped settings YAML"
}
This is to read the currently loaded ROR settings
GET $ES_URL/_readonlyrest/admin/config
Please use and protect the access to this endpoint at your own risk.