Creating a cluster action

In the previous recipe, we saw how to create a REST entry point but, to execute the action at cluster level, we need to create a cluster action.

An ElasticSearch action is generally executed and distributed in the cluster; in this recipe, we will see how to implement this kind of action. The cluster's action will be a bare minimum; we will send a string with a value for every shard, and the shards echo a resultant string, which is a concatenation of the string with the shard number.

Getting ready

You need a working ElasticSearch node, a Maven build tool, and an optional Java IDE. The code of this recipe is available in the chapter12/rest_plugin directory.

How to do it...

In this recipe, we will see that a REST call is converted to an internal cluster action. To execute an internal cluster action, the following classes are required:

• The Request and Response classes to communicate with the cluster.
• A RequestBuilder class used to execute a request to the cluster.
• An...