Preview Datafeed API

The Preview Datafeed API provides the ability to preview a machine learning datafeed’s data in the cluster. It accepts a PreviewDatafeedRequest object and responds with a PreviewDatafeedResponse object.

Preview Datafeed Request

A PreviewDatafeedRequest object is created referencing a non-null datafeedId.

PreviewDatafeedRequest request = new PreviewDatafeedRequest(datafeedId); 

Constructing a new request referencing an existing datafeedId

Preview Datafeed Response

BytesReference rawPreview = response.getPreview(); 
List<Map<String, Object>> semiParsedPreview = response.getDataList(); 

The raw BytesReference of the data preview

A List<Map<String,Object>> that represents the previewed data

Synchronous Execution

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

PreviewDatafeedResponse response = client.machineLearning().previewDatafeed(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.

Asynchronous Execution

Executing a PreviewDatafeedRequest 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 preview-datafeed method:

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

The PreviewDatafeedRequest to execute and the ActionListener to use when the execution completes

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 preview-datafeed looks like:

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

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

Called when the execution is successfully completed.

Called when the whole PreviewDatafeedRequest fails.