Removing elastic reranker chunking feature flag and allow return_documents to be false (#136045)

* Removing elastic reranker chunking feature flag

* Allow return_documents to be set to false

* Updating unit tests to verify returned document strings

---------

Co-authored-by: Elastic Machine <[email protected]>

Author: dan-rubinstein

test/test-clusters/src/main/java/org/elasticsearch/test/cluster/FeatureFlag.java

@@ -25,8 +25,7 @@ public enum FeatureFlag {
         "es.index_dimensions_tsid_optimization_feature_flag_enabled=true",
         Version.fromString("9.2.0"),
         null
-    ),
-    ELASTIC_RERANKER_CHUNKING("es.elastic_reranker_chunking_long_documents=true", Version.fromString("9.2.0"), null);
+    );
 
     public final String systemProperty;
     public final Version from;

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/chunking/RerankRequestChunker.java

@@ -53,10 +53,13 @@ public List<String> getChunkedInputs() {
         return chunkedInputs;
     }
 
-    public ActionListener<InferenceServiceResults> parseChunkedRerankResultsListener(ActionListener<InferenceServiceResults> listener) {
+    public ActionListener<InferenceServiceResults> parseChunkedRerankResultsListener(
+        ActionListener<InferenceServiceResults> listener,
+        boolean returnDocuments
+    ) {
         return ActionListener.wrap(results -> {
             if (results instanceof RankedDocsResults rankedDocsResults) {
-                listener.onResponse(parseRankedDocResultsForChunks(rankedDocsResults));
+                listener.onResponse(parseRankedDocResultsForChunks(rankedDocsResults, returnDocuments));
 
             } else {
                 listener.onFailure(new IllegalArgumentException("Expected RankedDocsResults but got: " + results.getClass()));
@@ -65,7 +68,7 @@ public ActionListener<InferenceServiceResults> parseChunkedRerankResultsListener
         }, listener::onFailure);
     }
 
-    private RankedDocsResults parseRankedDocResultsForChunks(RankedDocsResults rankedDocsResults) {
+    private RankedDocsResults parseRankedDocResultsForChunks(RankedDocsResults rankedDocsResults, boolean returnDocuments) {
         List<RankedDocsResults.RankedDoc> topRankedDocs = new ArrayList<>();
         Set<Integer> docIndicesSeen = new HashSet<>();
 
@@ -80,7 +83,7 @@ private RankedDocsResults parseRankedDocResultsForChunks(RankedDocsResults ranke
                 RankedDocsResults.RankedDoc updatedRankedDoc = new RankedDocsResults.RankedDoc(
                     docIndex,
                     rankedDoc.relevanceScore(),
-                    inputs.get(docIndex)
+                    returnDocuments ? inputs.get(docIndex) : null
                 );
                 topRankedDocs.add(updatedRankedDoc);
                 docIndicesSeen.add(docIndex);

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/elasticsearch/ElasticRerankerServiceSettings.java

@@ -22,7 +22,6 @@
 
 import static org.elasticsearch.xpack.inference.services.ServiceUtils.extractOptionalEnum;
 import static org.elasticsearch.xpack.inference.services.ServiceUtils.extractOptionalPositiveInteger;
-import static org.elasticsearch.xpack.inference.services.elasticsearch.ElasticsearchInternalService.ELASTIC_RERANKER_CHUNKING;
 import static org.elasticsearch.xpack.inference.services.elasticsearch.ElasticsearchInternalService.RERANKER_ID;
 
 public class ElasticRerankerServiceSettings extends ElasticsearchInternalServiceSettings {
@@ -102,30 +101,26 @@ public static ElasticRerankerServiceSettings fromMap(Map<String, Object> map) {
         ValidationException validationException = new ValidationException();
         var baseSettings = ElasticsearchInternalServiceSettings.fromMap(map, validationException);
 
-        LongDocumentStrategy longDocumentStrategy = null;
-        Integer maxChunksPerDoc = null;
-        if (ELASTIC_RERANKER_CHUNKING.isEnabled()) {
-            longDocumentStrategy = extractOptionalEnum(
-                map,
-                LONG_DOCUMENT_STRATEGY,
-                ModelConfigurations.SERVICE_SETTINGS,
-                LongDocumentStrategy::fromString,
-                EnumSet.allOf(LongDocumentStrategy.class),
-                validationException
+        LongDocumentStrategy longDocumentStrategy = extractOptionalEnum(
+            map,
+            LONG_DOCUMENT_STRATEGY,
+            ModelConfigurations.SERVICE_SETTINGS,
+            LongDocumentStrategy::fromString,
+            EnumSet.allOf(LongDocumentStrategy.class),
+            validationException
+        );
+
+        Integer maxChunksPerDoc = extractOptionalPositiveInteger(
+            map,
+            MAX_CHUNKS_PER_DOC,
+            ModelConfigurations.SERVICE_SETTINGS,
+            validationException
+        );
+
+        if (maxChunksPerDoc != null && (longDocumentStrategy == null || longDocumentStrategy == LongDocumentStrategy.TRUNCATE)) {
+            validationException.addValidationError(
+                "The [" + MAX_CHUNKS_PER_DOC + "] setting requires [" + LONG_DOCUMENT_STRATEGY + "] to be set to [chunk]"
             );
-
-            maxChunksPerDoc = extractOptionalPositiveInteger(
-                map,
-                MAX_CHUNKS_PER_DOC,
-                ModelConfigurations.SERVICE_SETTINGS,
-                validationException
-            );
-
-            if (maxChunksPerDoc != null && (longDocumentStrategy == null || longDocumentStrategy == LongDocumentStrategy.TRUNCATE)) {
-                validationException.addValidationError(
-                    "The [" + MAX_CHUNKS_PER_DOC + "] setting requires [" + LONG_DOCUMENT_STRATEGY + "] to be set to [chunk]"
-                );
-            }
         }
 
         if (validationException.validationErrors().isEmpty() == false) {

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/services/elasticsearch/ElasticsearchInternalService.java

@@ -16,7 +16,6 @@
 import org.elasticsearch.common.logging.DeprecationCategory;
 import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.settings.Settings;
-import org.elasticsearch.common.util.FeatureFlag;
 import org.elasticsearch.common.util.LazyInitializable;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.Strings;
@@ -116,8 +115,6 @@ public class ElasticsearchInternalService extends BaseElasticsearchInternalServi
     private static final Logger logger = LogManager.getLogger(ElasticsearchInternalService.class);
     private static final DeprecationLogger DEPRECATION_LOGGER = DeprecationLogger.getLogger(ElasticsearchInternalService.class);
 
-    public static final FeatureFlag ELASTIC_RERANKER_CHUNKING = new FeatureFlag("elastic_reranker_chunking_long_documents");
-
     /**
      * Fix for https://github.com/elastic/elasticsearch/issues/124675
      * In 8.13.0 we transitioned from model_version to model_id. Any elser inference endpoints created prior to 8.13.0 will still use
@@ -698,26 +695,26 @@ public void inferRerank(
             }
         });
 
-        if (model instanceof ElasticRerankerModel elasticRerankerModel && ELASTIC_RERANKER_CHUNKING.isEnabled()) {
+        var returnDocs = Boolean.TRUE;
+        if (returnDocuments != null) {
+            returnDocs = returnDocuments;
+        } else if (model.getTaskSettings() instanceof RerankTaskSettings modelSettings) {
+            var requestSettings = RerankTaskSettings.fromMap(requestTaskSettings);
+            returnDocs = RerankTaskSettings.of(modelSettings, requestSettings).returnDocuments();
+        }
+
+        if (model instanceof ElasticRerankerModel elasticRerankerModel) {
             var serviceSettings = elasticRerankerModel.getServiceSettings();
             var longDocumentStrategy = serviceSettings.getLongDocumentStrategy();
             if (longDocumentStrategy == ElasticRerankerServiceSettings.LongDocumentStrategy.CHUNK) {
                 var rerankChunker = new RerankRequestChunker(query, inputs, serviceSettings.getMaxChunksPerDoc());
                 inputs = rerankChunker.getChunkedInputs();
-                resultsListener = rerankChunker.parseChunkedRerankResultsListener(resultsListener);
+                resultsListener = rerankChunker.parseChunkedRerankResultsListener(resultsListener, returnDocs);
             }
 
         }
         var request = buildInferenceRequest(model.mlNodeDeploymentId(), new TextSimilarityConfigUpdate(query), inputs, inputType, timeout);
 
-        var returnDocs = Boolean.TRUE;
-        if (returnDocuments != null) {
-            returnDocs = returnDocuments;
-        } else if (model.getTaskSettings() instanceof RerankTaskSettings modelSettings) {
-            var requestSettings = RerankTaskSettings.fromMap(requestTaskSettings);
-            returnDocs = RerankTaskSettings.of(modelSettings, requestSettings).returnDocuments();
-        }
-
         Function<Integer, String> inputSupplier = returnDocs == Boolean.TRUE ? inputs::get : i -> null;
 
         ActionListener<InferModelAction.Response> mlResultsListener = resultsListener.delegateFailureAndWrap(