Setup Graylog → Get started with Graylog → initial config setting
page doesn’t mention datanode at all. In fact, there’s a discussion about adding elasticsearch_hosts. Seeing the related line in server.conf, I added my datanode in elasticsearch_hosts hosts list, and wasted two days to figure out why 9200 port wasn’t working.
When, I click on … → initial config setting → Graylog server config page, again in opensearch section, elasticsearch_hosts thing mentioned. Since datanode is based on opensearch, I just assumed that instructions there have to be correct.
This is very confusing for those who’re new to graylog. Documentation could use improvement.