[ML] Machine learning data frame analytics (#43544)

This merges the initial work that adds a framework for performing
machine learning analytics on data frames. The feature is currently experimental
and requires a platinum license. Note that the original commits can be
found in the `feature-ml-data-frame-analytics` branch.

A new set of APIs is added which allows the creation of data frame analytics
jobs. Configuration allows specifying different types of analysis to be performed
on a data frame. At first there is support for outlier detection.

The APIs are:

- PUT _ml/data_frame/analysis/{id}
- GET _ml/data_frame/analysis/{id}
- GET _ml/data_frame/analysis/{id}/_stats
- POST _ml/data_frame/analysis/{id}/_start
- POST _ml/data_frame/analysis/{id}/_stop
- DELETE _ml/data_frame/analysis/{id}

When a data frame analytics job is started a persistent task is created and started.
The main steps of the task are:

1. reindex the source index into the dest index
2. analyze the data through the data_frame_analyzer c++ process
3. merge the results of the process back into the destination index

In addition, an evaluation API is added which packages commonly used metrics
that provide evaluation of various analysis:

- POST _ml/data_frame/_evaluate

Author: dimitris-athanasiou

client/rest-high-level/src/main/java/org/elasticsearch/client/MLRequestConverters.java

@@ -32,19 +32,23 @@
 import org.elasticsearch.client.ml.DeleteCalendarEventRequest;
 import org.elasticsearch.client.ml.DeleteCalendarJobRequest;
 import org.elasticsearch.client.ml.DeleteCalendarRequest;
+import org.elasticsearch.client.ml.DeleteDataFrameAnalyticsRequest;
 import org.elasticsearch.client.ml.DeleteDatafeedRequest;
 import org.elasticsearch.client.ml.DeleteExpiredDataRequest;
 import org.elasticsearch.client.ml.DeleteFilterRequest;
 import org.elasticsearch.client.ml.DeleteForecastRequest;
 import org.elasticsearch.client.ml.DeleteJobRequest;
 import org.elasticsearch.client.ml.DeleteModelSnapshotRequest;
+import org.elasticsearch.client.ml.EvaluateDataFrameRequest;
 import org.elasticsearch.client.ml.FindFileStructureRequest;
 import org.elasticsearch.client.ml.FlushJobRequest;
 import org.elasticsearch.client.ml.ForecastJobRequest;
 import org.elasticsearch.client.ml.GetBucketsRequest;
 import org.elasticsearch.client.ml.GetCalendarEventsRequest;
 import org.elasticsearch.client.ml.GetCalendarsRequest;
 import org.elasticsearch.client.ml.GetCategoriesRequest;
+import org.elasticsearch.client.ml.GetDataFrameAnalyticsRequest;
+import org.elasticsearch.client.ml.GetDataFrameAnalyticsStatsRequest;
 import org.elasticsearch.client.ml.GetDatafeedRequest;
 import org.elasticsearch.client.ml.GetDatafeedStatsRequest;
 import org.elasticsearch.client.ml.GetFiltersRequest;
@@ -61,12 +65,15 @@
 import org.elasticsearch.client.ml.PreviewDatafeedRequest;
 import org.elasticsearch.client.ml.PutCalendarJobRequest;
 import org.elasticsearch.client.ml.PutCalendarRequest;
+import org.elasticsearch.client.ml.PutDataFrameAnalyticsRequest;
 import org.elasticsearch.client.ml.PutDatafeedRequest;
 import org.elasticsearch.client.ml.PutFilterRequest;
 import org.elasticsearch.client.ml.PutJobRequest;
 import org.elasticsearch.client.ml.RevertModelSnapshotRequest;
 import org.elasticsearch.client.ml.SetUpgradeModeRequest;
+import org.elasticsearch.client.ml.StartDataFrameAnalyticsRequest;
 import org.elasticsearch.client.ml.StartDatafeedRequest;
+import org.elasticsearch.client.ml.StopDataFrameAnalyticsRequest;
 import org.elasticsearch.client.ml.StopDatafeedRequest;
 import org.elasticsearch.client.ml.UpdateDatafeedRequest;
 import org.elasticsearch.client.ml.UpdateFilterRequest;
@@ -581,6 +588,115 @@ static Request deleteCalendarEvent(DeleteCalendarEventRequest deleteCalendarEven
         return new Request(HttpDelete.METHOD_NAME, endpoint);
     }
 
+    static Request putDataFrameAnalytics(PutDataFrameAnalyticsRequest putRequest) throws IOException {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "analytics")
+            .addPathPart(putRequest.getConfig().getId())
+            .build();
+        Request request = new Request(HttpPut.METHOD_NAME, endpoint);
+        request.setEntity(createEntity(putRequest, REQUEST_BODY_CONTENT_TYPE));
+        return request;
+    }
+
+    static Request getDataFrameAnalytics(GetDataFrameAnalyticsRequest getRequest) {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "analytics")
+            .addPathPart(Strings.collectionToCommaDelimitedString(getRequest.getIds()))
+            .build();
+        Request request = new Request(HttpGet.METHOD_NAME, endpoint);
+        RequestConverters.Params params = new RequestConverters.Params();
+        if (getRequest.getPageParams() != null) {
+            PageParams pageParams = getRequest.getPageParams();
+            if (pageParams.getFrom() != null) {
+                params.putParam(PageParams.FROM.getPreferredName(), pageParams.getFrom().toString());
+            }
+            if (pageParams.getSize() != null) {
+                params.putParam(PageParams.SIZE.getPreferredName(), pageParams.getSize().toString());
+            }
+        }
+        if (getRequest.getAllowNoMatch() != null) {
+            params.putParam(GetDataFrameAnalyticsRequest.ALLOW_NO_MATCH.getPreferredName(), Boolean.toString(getRequest.getAllowNoMatch()));
+        }
+        request.addParameters(params.asMap());
+        return request;
+    }
+
+    static Request getDataFrameAnalyticsStats(GetDataFrameAnalyticsStatsRequest getStatsRequest) {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "analytics")
+            .addPathPart(Strings.collectionToCommaDelimitedString(getStatsRequest.getIds()))
+            .addPathPartAsIs("_stats")
+            .build();
+        Request request = new Request(HttpGet.METHOD_NAME, endpoint);
+        RequestConverters.Params params = new RequestConverters.Params();
+        if (getStatsRequest.getPageParams() != null) {
+            PageParams pageParams = getStatsRequest.getPageParams();
+            if (pageParams.getFrom() != null) {
+                params.putParam(PageParams.FROM.getPreferredName(), pageParams.getFrom().toString());
+            }
+            if (pageParams.getSize() != null) {
+                params.putParam(PageParams.SIZE.getPreferredName(), pageParams.getSize().toString());
+            }
+        }
+        if (getStatsRequest.getAllowNoMatch() != null) {
+            params.putParam(GetDataFrameAnalyticsStatsRequest.ALLOW_NO_MATCH.getPreferredName(),
+                Boolean.toString(getStatsRequest.getAllowNoMatch()));
+        }
+        request.addParameters(params.asMap());
+        return request;
+    }
+
+    static Request startDataFrameAnalytics(StartDataFrameAnalyticsRequest startRequest) {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "analytics")
+            .addPathPart(startRequest.getId())
+            .addPathPartAsIs("_start")
+            .build();
+        Request request = new Request(HttpPost.METHOD_NAME, endpoint);
+        RequestConverters.Params params = new RequestConverters.Params();
+        if (startRequest.getTimeout() != null) {
+            params.withTimeout(startRequest.getTimeout());
+        }
+        request.addParameters(params.asMap());
+        return request;
+    }
+
+    static Request stopDataFrameAnalytics(StopDataFrameAnalyticsRequest stopRequest) {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "analytics")
+            .addPathPart(stopRequest.getId())
+            .addPathPartAsIs("_stop")
+            .build();
+        Request request = new Request(HttpPost.METHOD_NAME, endpoint);
+        RequestConverters.Params params = new RequestConverters.Params();
+        if (stopRequest.getTimeout() != null) {
+            params.withTimeout(stopRequest.getTimeout());
+        }
+        if (stopRequest.getAllowNoMatch() != null) {
+            params.putParam(
+                StopDataFrameAnalyticsRequest.ALLOW_NO_MATCH.getPreferredName(), Boolean.toString(stopRequest.getAllowNoMatch()));
+        }
+        request.addParameters(params.asMap());
+        return request;
+    }
+
+    static Request deleteDataFrameAnalytics(DeleteDataFrameAnalyticsRequest deleteRequest) {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "analytics")
+            .addPathPart(deleteRequest.getId())
+            .build();
+        return new Request(HttpDelete.METHOD_NAME, endpoint);
+    }
+
+    static Request evaluateDataFrame(EvaluateDataFrameRequest evaluateRequest) throws IOException {
+        String endpoint = new EndpointBuilder()
+            .addPathPartAsIs("_ml", "data_frame", "_evaluate")
+            .build();
+        Request request = new Request(HttpPost.METHOD_NAME, endpoint);
+        request.setEntity(createEntity(evaluateRequest, REQUEST_BODY_CONTENT_TYPE));
+        return request;
+    }
+
     static Request putFilter(PutFilterRequest putFilterRequest) throws IOException {
         String endpoint = new EndpointBuilder()
             .addPathPartAsIs("_ml")