Update to 7.0
- https://www.elastic.co/guide/en/elasticsearch/reference/7.0/rolling-upgrades.html
- /etc/elasticsearch/elasticsearch.yml discovery.zen.ping.unicast.hosts: ["127.0.0.1"]
- always update /etc/hosts
- always update /etc/heartbeat/monitors.d
- update td-agent plugins
- update td-agent config