I have two elastic search instances in two different machines in a LAN. I have also installed plugin-head in the two machines. Each of the plugins shows that the two elasticsearch instances are in cluster, one as master and one as worker. I have not changed the elastic search yml. Can you please confirm whether such installations creates a cluster by default?
Prior to ES 2.0, multicast discovery was enabled by default so any ES nodes in the same network and with the same cluster name would form a cluster. This practice isn't recommended anymore, i.e. you should use unicast discovery and explicitly set which nodes should be part of any cluster.
So, if I want to disable this default clustering, what should I do? Shall I upgrade to Elasticsearch 2.1.1 or there is some parameter in the elasticsearch.yml that will disable the default clustering?
You can disable multicast.
discovery.zen.ping.multicast.enabled: false
And change your cluster name:
cluster.name: mycluster
Also you can bind only to localhost:
network.host: 127.0.0.1