Add Cluster Feature for L2 Norm

docs/changelog/129181.yaml

@@ -0,0 +1,5 @@
+pr: 129181
+summary: Add Cluster Feature for L2 Norm
+area: "Search"
+type: bug
+issues: []

x-pack/plugin/rank-rrf/src/main/java/org/elasticsearch/xpack/rank/RankRRFFeatures.java

@@ -13,6 +13,7 @@
 import java.util.Set;
 
 import static org.elasticsearch.search.retriever.CompoundRetrieverBuilder.INNER_RETRIEVERS_FILTER_SUPPORT;
+import static org.elasticsearch.xpack.rank.linear.L2ScoreNormalizer.LINEAR_RETRIEVER_L2_NORM;
 import static org.elasticsearch.xpack.rank.linear.MinMaxScoreNormalizer.LINEAR_RETRIEVER_MINMAX_SINGLE_DOC_FIX;
 
 public class RankRRFFeatures implements FeatureSpecification {
@@ -26,6 +27,6 @@ public Set<NodeFeature> getFeatures() {
 
     @Override
     public Set<NodeFeature> getTestFeatures() {
-        return Set.of(INNER_RETRIEVERS_FILTER_SUPPORT, LINEAR_RETRIEVER_MINMAX_SINGLE_DOC_FIX);
+        return Set.of(INNER_RETRIEVERS_FILTER_SUPPORT, LINEAR_RETRIEVER_MINMAX_SINGLE_DOC_FIX, LINEAR_RETRIEVER_L2_NORM);
     }
 }

x-pack/plugin/rank-rrf/src/main/java/org/elasticsearch/xpack/rank/linear/L2ScoreNormalizer.java

@@ -9,6 +9,7 @@
 package org.elasticsearch.xpack.rank.linear;
 
 import org.apache.lucene.search.ScoreDoc;
+import org.elasticsearch.features.NodeFeature;
 
 /**
  * A score normalizer that applies L2 normalization to a set of scores.
@@ -25,6 +26,8 @@ public class L2ScoreNormalizer extends ScoreNormalizer {
 
     private static final float EPSILON = 1e-6f;
 
+    public static final NodeFeature LINEAR_RETRIEVER_L2_NORM = new NodeFeature("linear_retriever.l2_norm");
+
     public L2ScoreNormalizer() {}
 
     @Override

x-pack/plugin/rank-rrf/src/yamlRestTest/resources/rest-api-spec/test/linear/10_linear_retriever.yml

@@ -266,6 +266,9 @@ setup:
 
 ---
 "should normalize initial scores with l2_norm":
+  - requires:
+      cluster_features: [ "linear_retriever.l2_norm" ]
+      reason: "Requires l2_norm normalization support in linear retriever"
   - do:
       search:
         index: test
@@ -319,6 +322,9 @@ setup:
 
 ---
 "should handle all zero scores in normalization":
+  - requires:
+      cluster_features: [ "linear_retriever.l2_norm" ]
+      reason: "Requires l2_norm normalization support in linear retriever"
   - do:
       search:
         index: test