Initialization

A RestClient instance can be built through the corresponding RestClientBuilder class, created via RestClient#builder(HttpHost...) static method. The only required argument is one or more hosts that the client will communicate with, provided as instances of HttpHost as follows:

RestClient restClient = RestClient.builder(
        new HttpHost("localhost", 9200, "http"),
        new HttpHost("localhost", 9201, "http")).build();

The RestClient class is thread-safe and ideally has the same lifecycle as the application that uses it. It is important that it gets closed when no longer needed so that all the resources used by it get properly released, as well as the underlying http client instance and its threads:

restClient.close();

RestClientBuilder also allows to optionally set the following configuration parameters while building the RestClient instance:

RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
Header[] defaultHeaders = new Header[]{new BasicHeader("header", "value")};
builder.setDefaultHeaders(defaultHeaders); 

Set the default headers that need to be sent with each request, to prevent having to specify them with each single request

RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
builder.setMaxRetryTimeoutMillis(10000); 

Set the timeout that should be honoured in case multiple attempts are made for the same request. The default value is 30 seconds, same as the default socket timeout. In case the socket timeout is customized, the maximum retry timeout should be adjusted accordingly

RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
builder.setFailureListener(new RestClient.FailureListener() {
    @Override
    public void onFailure(HttpHost host) {
        
    }
});

Set a listener that gets notified every time a node fails, in case actions need to be taken. Used internally when sniffing on failure is enabled.

RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
builder.setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
    @Override
    public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder requestConfigBuilder) {
        return requestConfigBuilder.setSocketTimeout(10000); 
    }
});

Set a callback that allows to modify the default request configuration (e.g. request timeouts, authentication, or anything that the org.apache.http.client.config.RequestConfig.Builder allows to set)

RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "http"));
builder.setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
    @Override
    public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
        return httpClientBuilder.setProxy(new HttpHost("proxy", 9000, "http"));  
    }
});

Set a callback that allows to modify the http client configuration (e.g. encrypted communication over ssl, or anything that the org.apache.http.impl.nio.client.HttpAsyncClientBuilder allows to set)