Currently, using ActionFuture#actionGet will cause an ElasticSearchException to be thrown, but, it can be wrapped, for example, with a RemoteTransportException. The wrapping can be important, as it provides a "trace" to the origin of the failure.

We can automatically unwrap to the actual failure when throwing a failure from actionGet, and add to ActionFuture a helper method called getRootFailure which provides the actual (possibly wrapped) exception.