Abstract codec lookup by name, to make CodecService extensible

server/src/main/java/org/elasticsearch/index/codec/CodecProvided.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.index.codec;
+
+import org.apache.lucene.codecs.Codec;
+
+/**
+ * Abstracts codec lookup by name, to make CodecService extensible.
+ */
+@FunctionalInterface
+public interface CodecProvided {
+    Codec codec(String name);
+}

server/src/main/java/org/elasticsearch/index/codec/CodecService.java

@@ -28,7 +28,7 @@
  * data-structures per field. Elasticsearch exposes the full
  * {@link Codec} capabilities through this {@link CodecService}.
  */
-public class CodecService {
+public class CodecService implements CodecProvided {
 
     public static final FeatureFlag ZSTD_STORED_FIELDS_FEATURE_FLAG = new FeatureFlag("zstd_stored_fields");
 
@@ -86,7 +86,8 @@ public Codec codec(String name) {
     }
 
     /**
-     * Returns all registered available codec names
+     * Returns all registered available codec names.
+     * Public visibility for tests.
      */
     public String[] availableCodecs() {
         return codecs.keySet().toArray(new String[0]);

server/src/main/java/org/elasticsearch/index/engine/EngineConfig.java

@@ -23,7 +23,7 @@
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.index.IndexSettings;
-import org.elasticsearch.index.codec.CodecService;
+import org.elasticsearch.index.codec.CodecProvided;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.seqno.RetentionLeases;
 import org.elasticsearch.index.shard.ShardId;
@@ -60,7 +60,7 @@ public final class EngineConfig {
     private final MergePolicy mergePolicy;
     private final Analyzer analyzer;
     private final Similarity similarity;
-    private final CodecService codecService;
+    private final CodecProvided codecProvided;
     private final Engine.EventListener eventListener;
     private final QueryCache queryCache;
     private final QueryCachingPolicy queryCachingPolicy;
@@ -148,7 +148,7 @@ public EngineConfig(
         MergePolicy mergePolicy,
         Analyzer analyzer,
         Similarity similarity,
-        CodecService codecService,
+        CodecProvided codecProvided,
         Engine.EventListener eventListener,
         QueryCache queryCache,
         QueryCachingPolicy queryCachingPolicy,
@@ -176,7 +176,7 @@ public EngineConfig(
         this.mergePolicy = mergePolicy;
         this.analyzer = analyzer;
         this.similarity = similarity;
-        this.codecService = codecService;
+        this.codecProvided = codecProvided;
         this.eventListener = eventListener;
         codecName = indexSettings.getValue(INDEX_CODEC_SETTING);
         this.mapperService = mapperService;
@@ -252,14 +252,14 @@ public boolean isEnableGcDeletes() {
      * </p>
      */
     public Codec getCodec() {
-        return codecService.codec(codecName);
+        return codecProvided.codec(codecName);
     }
 
     /**
-     * @return the {@link CodecService}
+     * @return the {@link CodecProvided}
      */
-    public CodecService getCodecService() {
-        return codecService;
+    public CodecProvided getCodecProvider() {
+        return codecProvided;
     }
 
     /**

test/framework/src/main/java/org/elasticsearch/index/engine/EngineTestCase.java

@@ -250,7 +250,7 @@ public static EngineConfig copy(EngineConfig config, LongSupplier globalCheckpoi
             config.getMergePolicy(),
             config.getAnalyzer(),
             config.getSimilarity(),
-            config.getCodecService(),
+            config.getCodecProvider(),
             config.getEventListener(),
             config.getQueryCache(),
             config.getQueryCachingPolicy(),
@@ -282,7 +282,7 @@ public EngineConfig copy(EngineConfig config, Analyzer analyzer) {
             config.getMergePolicy(),
             analyzer,
             config.getSimilarity(),
-            config.getCodecService(),
+            config.getCodecProvider(),
             config.getEventListener(),
             config.getQueryCache(),
             config.getQueryCachingPolicy(),
@@ -314,7 +314,7 @@ public EngineConfig copy(EngineConfig config, MergePolicy mergePolicy) {
             mergePolicy,
             config.getAnalyzer(),
             config.getSimilarity(),
-            config.getCodecService(),
+            config.getCodecProvider(),
             config.getEventListener(),
             config.getQueryCache(),
             config.getQueryCachingPolicy(),