All APIs in the
RestHighLevelClient accept a
RequestOptions which you can
use to customize the request in ways that won’t change how Elasticsearch
executes the request. For example, this is the place where you’d specify a
NodeSelector to control which node receives the request. See the
low level client documentation for
more examples of customizing the options.
=== Asynchronous usage
All of the the methods across the different clients exist in a traditional synchronous and asynchronous variant. The difference is that the asynchronous ones use asynchronous requests in the REST Low Level Client. This is useful if you are doing multiple requests or are using e.g. rx java, Kotlin co-routines, or similar frameworks.
The asynchronous methods are recognizable by the fact that they have the word "Async" in their name
and return a
Cancellable instance. The asynchronous methods accept the same request object
as the synchronous variant and accept a generic
T is the return
type of the synchronous method.
All asynchronous methods return a
Cancellable object with a
cancel method that you may call
in case you want to abort the request. Cancelling
no longer needed requests is a good way to avoid putting unnecessary
load on Elasticsearch.
Cancellable instance is optional and you can safely ignore this if you have
no need for this. A use case for this would be using this with e.g. Kotlin’s