The cluster nodes info API allows to retrieve one or more (or all) of the cluster nodes information.
$ curl -XGET 'http://localhost:9200/_cluster/nodes'
$ curl -XGET 'http://localhost:9200/_cluster/nodes/nodeId1,nodeId2'
The first command retrieves information of all the nodes in the cluster. The second commands selectively retrieves nodes information of only nodeId1 and nodeId2.