Elastics Logstash provides internal statistics based on X-Pack, which comes for free. Those statistics are written to an Elasticsearch index and can therefor be viewed in Grafana easily. No additional client or exporter is needed. More information on how to enable the internal Logstash statistics can be found at:
The metrics found in this dashboard are based on the ones available in the official Kibana Dashboard for monitoring Logstash. If you have multiple Logstash Nodes you can select one via variable. The Node Overview and Node Advanced Stats Dashboard Rows show all of the Graphs grouped by Node. If you would like to have each of these dashboard rows per Logstash node (so repeated by node) please find my other dashboard which does exactly that. This is my first dashboard upload and i hope you find it as useful as i do.
If you would like to see the dashboard in action - you can bring up a Grafana-PLEI stack (Grafana bundled with (P)rometheus, (L)ogstash, (E)lasicsearch & (I)nfluxDB) with docker-compose and try it yourself. You can find it here:
Moreover you can open issues and pull requests regarding this dashboard or the PLEI stack via this GitHub repo.