Logstash to ES cluster

Elastic Stack Logstash
1

how should be the conf for Sending data to ES cluster (of 3 nodes) from Logstash

should i give all the urls of the cluster in output as:

output {
elasticsearch { hosts => ["es-client-01:9200","es-master-01:9200","es-data-01"] }
}

or
only a single ES instance is enough?

pls explain the internals of Load balancing

thanks
soumya

2

If you only have a single data node I don't think there is any point in creating separate node types.

3

List all 3.
See https://www.elastic.co/guide/en/logstash/5.5/plugins-outputs-elasticsearch.html#plugins-outputs-elasticsearch-hosts for more.