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 and in this recipe, we will see how to implement these kinds of actions. The cluster action will be very bare, we will be sending a string with a value for every shard and these strings echo a result string concatenating the string with the shard number.

Getting ready

You need a working ElasticSearch node, a Maven built 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 have seen that a REST call is converted to an internal cluster action.

To execute an internal cluster action, the following classes are required:

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