Elasticsearch cluster 'master_not_discovered_exception'

I resolved with this line:

network.publish_host: ec2-xx-xx-xx-xx.eu-west-1.compute.amazonaws.com

every elasticsearch.yml config file must have this line with your hostname

The root cause of master not discovered exception is the nodes are not able to ping each other on port 9300. And this needs to be both ways. i.e node1 should be able to ping node2 on 9300 and vice versa.

Note : Elasticsearch reserves port 9300-9400 for cluster communication and port 9200-9300 for accessing the elasticsearch APIs.

A simple telnet would be able to confirm. From node1, fire telnet node2 9300.

If it succeeds, next from node2 try telnet node1 9300.

In case of master not discovered exception, at least one of the above telnet would be failing.

In case you don't have telnet installed, you could even do a curl.

Hope this helps.