ES monitoring
https://www.quora.com/What-is-the-best-monitoring-tool-for-Elasticsearch-I-also-want-log-monitoring-to-make-sure-no-error-messages-get-missed
https://www.datadoghq.com/blog/collect-elasticsearch-metrics/
https://www.oreilly.com/ideas/10-elasticsearch-metrics-to-watch
https://medium.com/@dionnis/elasticsearch-monitoring-and-maintenance-tools-research-18c5fb45a747
https://www.opsview.com/resources/elasticsearch/blog/elasticsearch-monitoring-tools
https://www.datadoghq.com/blog/monitor-elasticsearch-performance-metrics/
https://thenewstack.io/properly-monitor-elasticsearch/
https://sematext.com/blog/elasticsearch-monitoring-marvel-alternative/
https://signalfx.com/blog/how-we-monitor-and-run-elasticsearch-at-scale/
https://www.elastic.co/blog/monitoring-kafka-with-elastic-stack-1-filebeat