[Backport 2.16] Add initial search request inference processor (#2731)

Author: opensearch-trigger-bot[bot]

plugin/src/main/java/org/opensearch/ml/plugin/MachineLearningPlugin.java

@@ -213,6 +213,7 @@
 import org.opensearch.ml.model.MLModelCacheHelper;
 import org.opensearch.ml.model.MLModelManager;
 import org.opensearch.ml.processor.MLInferenceIngestProcessor;
+import org.opensearch.ml.processor.MLInferenceSearchRequestProcessor;
 import org.opensearch.ml.repackage.com.google.common.collect.ImmutableList;
 import org.opensearch.ml.rest.RestMLCreateConnectorAction;
 import org.opensearch.ml.rest.RestMLCreateControllerAction;
@@ -977,7 +978,11 @@ public Map<String, Processor.Factory<SearchRequestProcessor>> getRequestProcesso
                 GenerativeQAProcessorConstants.REQUEST_PROCESSOR_TYPE,
                 new GenerativeQARequestProcessor.Factory(() -> this.ragSearchPipelineEnabled)
             );
-
+        requestProcessors
+            .put(
+                MLInferenceSearchRequestProcessor.TYPE,
+                new MLInferenceSearchRequestProcessor.Factory(parameters.client, parameters.namedXContentRegistry)
+            );
         return requestProcessors;
     }
 

plugin/src/main/java/org/opensearch/ml/processor/MLInferenceSearchRequestProcessor.java

@@ -189,7 +189,13 @@ default Object getModelOutputValue(MLOutput mlOutput, String modelOutputFieldNam
                 return modelTensorOutputMap;
             } else {
                 try {
-                    return JsonPath.parse(modelTensorOutputMap).read(modelOutputFieldName);
+                    Object modelOutputValue = JsonPath.parse(modelTensorOutputMap).read(modelOutputFieldName);
+                    if (modelOutputValue == null) {
+                        throw new IllegalArgumentException(
+                            "model inference output cannot find such json path: " + modelOutputFieldName + " in " + modelTensorOutputMap
+                        );
+                    }
+                    return modelOutputValue;
                 } catch (Exception e) {
                     if (ignoreMissing) {
                         return modelTensorOutputMap;
@@ -313,7 +319,6 @@ default List<String> writeNewDotPathForNestedObject(Object json, String dotPath)
      * @return the converted dot path notation string
      */
     default String convertToDotPath(String path) {
-
         return path.replaceAll("\\[(\\d+)\\]", "$1\\.").replaceAll("\\['(.*?)']", "$1\\.").replaceAll("^\\$", "").replaceAll("\\.$", "");
     }
 

plugin/src/main/java/org/opensearch/ml/processor/ModelExecutor.java

@@ -38,6 +38,7 @@
 import org.opensearch.ml.common.spi.MLCommonsExtension;
 import org.opensearch.ml.common.spi.tools.Tool;
 import org.opensearch.ml.engine.tools.MLModelTool;
+import org.opensearch.ml.processor.MLInferenceSearchRequestProcessor;
 import org.opensearch.plugins.ExtensiblePlugin;
 import org.opensearch.plugins.SearchPipelinePlugin;
 import org.opensearch.plugins.SearchPlugin;
@@ -73,10 +74,11 @@ public void testGetSearchExts() {
     public void testGetRequestProcessors() {
         SearchPipelinePlugin.Parameters parameters = mock(SearchPipelinePlugin.Parameters.class);
         Map<String, ?> requestProcessors = plugin.getRequestProcessors(parameters);
-        assertEquals(1, requestProcessors.size());
+        assertEquals(2, requestProcessors.size());
         assertTrue(
             requestProcessors.get(GenerativeQAProcessorConstants.REQUEST_PROCESSOR_TYPE) instanceof GenerativeQARequestProcessor.Factory
         );
+        assertTrue(requestProcessors.get(MLInferenceSearchRequestProcessor.TYPE) instanceof MLInferenceSearchRequestProcessor.Factory);
     }
 
     @Test