Explain data frame analytics API

The request can be constructed with the id of an existing data frame analytics job.

ExplainDataFrameAnalyticsRequest request = new ExplainDataFrameAnalyticsRequest("existing_job_id"); 

It can also be constructed with a data frame analytics config to explain it before creating it.

DataFrameAnalyticsConfig config = DataFrameAnalyticsConfig.builder()
    .setSource(DataFrameAnalyticsSource.builder().setIndex("explain-df-test-source-index").build())
    .setAnalysis(org.elasticsearch.client.ml.dataframe.OutlierDetection.createDefault())
    .build();
request = new ExplainDataFrameAnalyticsRequest(config); 

When executing a ExplainDataFrameAnalyticsRequest in the following manner, the client waits for the ExplainDataFrameAnalyticsResponse to be returned before continuing with code execution:

ExplainDataFrameAnalyticsResponse response = client.machineLearning().explainDataFrameAnalytics(request,
    RequestOptions.DEFAULT);

Synchronous calls may throw an IOException in case of either failing to parse the REST response in the high-level REST client, the request times out or similar cases where there is no response coming back from the server.

In cases where the server returns a 4xx or 5xx error code, the high-level client tries to parse the response body error details instead and then throws a generic ElasticsearchException and adds the original ResponseException as a suppressed exception to it.

Executing a ExplainDataFrameAnalyticsRequest can also be done in an asynchronous fashion so that the client can return directly. Users need to specify how the response or potential failures will be handled by passing the request and a listener to the asynchronous explain-data-frame-analytics method:

client.machineLearning().explainDataFrameAnalyticsAsync(request, RequestOptions.DEFAULT, listener); 

The asynchronous method does not block and returns immediately. Once it is completed the ActionListener is called back using the onResponse method if the execution successfully completed or using the onFailure method if it failed. Failure scenarios and expected exceptions are the same as in the synchronous execution case.

A typical listener for explain-data-frame-analytics looks like:

ActionListener<ExplainDataFrameAnalyticsResponse> listener = new ActionListener<ExplainDataFrameAnalyticsResponse>() {
    @Override
    public void onResponse(ExplainDataFrameAnalyticsResponse response) {
        
    }

    @Override
    public void onFailure(Exception e) {
        
    }
};

The returned ExplainDataFrameAnalyticsResponse contains the field selection and the memory usage estimation.

List<FieldSelection> fieldSelection = response.getFieldSelection(); 
MemoryEstimation memoryEstimation = response.getMemoryEstimation();