Fix LTR rescorer with model alias

docs/changelog/126273.yaml

@@ -0,0 +1,5 @@
+pr: 126273
+summary: Fix LTR rescorer with model alias
+area: Ranking
+type: bug
+issues: []

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/loadingservice/ModelLoadingService.java

@@ -239,8 +239,7 @@ public ModelLoadingService(
         this.licenseState = licenseState;
     }
 
-    // for testing
-    String getModelId(String modelIdOrAlias) {
+    public String getModelId(String modelIdOrAlias) {
         return modelAliasToId.getOrDefault(modelIdOrAlias, modelIdOrAlias);
     }
 

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/ltr/LearningToRankService.java

@@ -101,7 +101,7 @@ public void loadLocalModel(String modelId, ActionListener<LocalModel> listener)
      */
     public void loadLearningToRankConfig(String modelId, Map<String, Object> params, ActionListener<LearningToRankConfig> listener) {
         trainedModelProvider.getTrainedModel(
-            modelId,
+            modelLoadingService.getModelId(modelId),
             GetTrainedModelsAction.Includes.all(),
             null,
             ActionListener.wrap(trainedModelConfig -> {

x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/inference/ltr/LearningToRankServiceTests.java

@@ -42,12 +42,14 @@
 import static org.hamcrest.Matchers.hasKey;
 import static org.hamcrest.Matchers.hasSize;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.argThat;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.isA;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
 public class LearningToRankServiceTests extends ESTestCase {
     public static final String GOOD_MODEL = "inference-entity-id";
@@ -185,7 +187,10 @@ protected NamedXContentRegistry xContentRegistry() {
     }
 
     private ModelLoadingService mockModelLoadingService() {
-        return mock(ModelLoadingService.class);
+        ModelLoadingService modelLoadingService = mock(ModelLoadingService.class);
+        when(modelLoadingService.getModelId(anyString())).thenAnswer(i -> i.getArgument(0));
+
+        return modelLoadingService;
     }
 
     @SuppressWarnings("unchecked")

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/ml/learning_to_rank_rescorer.yml

@@ -147,11 +147,15 @@ setup:
           { "index": {} }
           { "product": "Laptop", "cost": 500}
 
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      ml.put_trained_model_alias:
+        model_id: "ltr-model"
+        model_alias: "ltr-model-alias"
+
 ---
 "Test rescore with stored model":
-  - skip:
-      awaits_fix: "https://github.com/elastic/elasticsearch/issues/80703"
-
   - do:
       search:
         index: store
@@ -182,12 +186,11 @@ setup:
   - match: { hits.hits.0._score: 6.0 }
   - match: { hits.hits.1._score: 6.0 }
   - match: { hits.hits.2._score: 3.0 }
+
 ---
 "Test rescore with stored model and smaller window_size":
-  - skip:
-      awaits_fix: "https://github.com/elastic/elasticsearch/issues/80703"
-
   - do:
+      catch: bad_request
       search:
         index: store
         size: 5
@@ -198,16 +201,12 @@ setup:
               "learning_to_rank": { "model_id": "ltr-model" }
             }
           }
-  - match: { hits.hits.0._score: 17.0 }
-  - match: { hits.hits.1._score: 17.0 }
-  - match: { hits.hits.2._score: 1.0 }
-  - match: { hits.hits.3._score: 1.0 }
-  - match: { hits.hits.4._score: 1.0 }
+  - match: { status: 400 }
+  - match: { error.root_cause.0.type: "action_request_validation_exception" }
+  - match: { error.root_cause.0.reason: "Validation Failed: 1: rescorer [window_size] is too small and should be at least the value of [from + size: 4] but was [2];" }
+
 ---
 "Test rescore with stored model and chained rescorers":
-  - skip:
-      awaits_fix: "https://github.com/elastic/elasticsearch/issues/80703"
-
   - do:
       search:
         index: store
@@ -216,11 +215,11 @@ setup:
           {
             "rescore": [
             {
-              "window_size": 4,
+              "window_size": 10,
               "query": { "rescore_query":{ "script_score": {"query": {"match_all": {}}, "script": {"source": "return 4"}}}}
             },
             {
-              "window_size": 3,
+              "window_size": 5,
               "learning_to_rank": { "model_id": "ltr-model" }
             },
             {
@@ -232,8 +231,9 @@ setup:
   - match: { hits.hits.0._score: 37.0 }
   - match: { hits.hits.1._score: 37.0 }
   - match: { hits.hits.2._score: 14.0 }
-  - match: { hits.hits.3._score: 5.0 }
-  - match: { hits.hits.4._score: 1.0 }
+  - match: { hits.hits.3._score: 6.0 }
+  - match: { hits.hits.4._score: 6.0 }
+
 ---
 "Test rescore with missing model":
   - do:
@@ -247,8 +247,12 @@ setup:
               "learning_to_rank": { "model_id": "ltr-missing" }
             }
           }
+  - match: { status: 404 }
+  - match: { error.root_cause.0.type: "resource_not_found_exception" }
+  - match: { error.root_cause.0.reason: "Could not find trained model [ltr-missing]" }
+
 ---
-"Test rescore with no hits model":
+"Test rescore with no hits":
   - do:
       search:
         index: store
@@ -261,6 +265,26 @@ setup:
             }
           }
   - length: { hits.hits: 0 }
+
+---
+"Test rescore using model alias":
+  - skip:
+      features: headers
+  - do:
+      search:
+        index: store
+        size: 3
+        body: >
+          {
+            "rescore": {
+              "window_size": 10,
+              "learning_to_rank": { "model_id": "ltr-model-alias" }
+            }
+          }
+  - match: { hits.hits.0._score: 17.0 }
+  - match: { hits.hits.1._score: 17.0 }
+  - match: { hits.hits.2._score: 14.0 }
+
 ---
 "Test model input validation":
   - skip: