GET /_nodes not showing offline nodes

[chdudfield (Craig Dudfield)]

I am running Elasticsearch 5.5.2 with 3 nodes in a cluster, one master only and the other two master and data. When i do a "GET /_nodes" command from within Kibana it returns
"_nodes": {
"total": 3,
"successful": 3,
"failed": 0
}
which is what i would expect.
However when i turn one of the nodes off and do the same command it returns
"_nodes": {
"total": 2,
"successful": 2,
"failed": 0
}
Is this expected behavior and is there a way to force Elasticsearch to search for all three nodes and show an error if one is offline?
The yml config file has all three nodes configured like discovery.zen.ping.unicast.hosts: ["IP_ADDRESS_OR_HOSTNAME1", "IP_ADDRESS_OR_HOSTNAME2", "IP_ADDRESS_OR_HOSTNAME3"]

[DavidTurner]

@chdudfield

Is this expected behavior and is there a way to force Elasticsearch to search for all three nodes and show an error if one is offline?

Yes, that's the expected behaviour. You can use alerting to alert you if the cluster isn't in the state you expect. There's nothing in core Elasticsearch to check this because there's nothing that Elasticsearch itself can do about it.