I have upgraded my ES to 7.3.2, and I have the correct elasticsearch.yml files.
The 2 nodes are on EC2 and both master and data. Following are elasticsearch.yml for node -1 and node-2 respectively:
Node1:
cluster.name: cluster
node.master: true
node.data: true
node.ingest: true
path.data: /app/data/lib/elasticsearch
path.logs: /app/log/elasticsearch
network.host: 10.250.60.22
http.port: 9200
discovery.seed_hosts: ["10.250.60.22","10.250.70.232"]
cluster.initial_master_nodes: ["10.250.60.22","10.250.70.232"]
logger.org.elasticsearch.discovery: TRACE
Node 2:
cluster.name: cluster
node.master: true
node.data: true
node.ingest: true
path.data: /app/data/lib/elasticsearch
path.logs: /app/log/elasticsearch
network.host: 10.250.70.232
http.port: 9200
discovery.seed_hosts: ["10.250.60.22","10.250.70.232"]
cluster.initial_master_nodes: ["10.250.60.22","10.250.70.232"]
logger.org.elasticsearch.discovery: TRACE
As you can see, I enabled TRACE settings and see the following in server: 10.250.60.22
[2019-09-23T18:31:48,642][TRACE][o.e.d.SeedHostsResolver ] [ip-10-250-60-22] resolved host [10.250.60.22] to [10.250.60.22:9300]
[2019-09-23T18:31:48,643][TRACE][o.e.d.SeedHostsResolver ] [ip-10-250-60-22] resolved host [10.250.70.232] to [10.250.70.232:9300]
[2019-09-23T18:31:48,644][TRACE][o.e.d.PeerFinder ] [ip-10-250-60-22] probing resolved transport addresses [10.250.70.232:9300]
So communication and network is not an issue.
Also, when I change the other node to be just data, and not master, the cluster shows 2 nodes.
But it seems unstable.
Any suggestions, as I am inclined to think this is an ES 7.3.2 issue.