Adding feature flag

Author: jonathan-buttner

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

@@ -19,7 +19,8 @@ public enum FeatureFlag {
     TIME_SERIES_MODE("es.index_mode_feature_flag_registered=true", Version.fromString("8.0.0"), null),
     SUB_OBJECTS_AUTO_ENABLED("es.sub_objects_auto_feature_flag_enabled=true", Version.fromString("8.16.0"), null),
     DOC_VALUES_SKIPPER("es.doc_values_skipper_feature_flag_enabled=true", Version.fromString("8.18.1"), null),
-    USE_LUCENE101_POSTINGS_FORMAT("es.use_lucene101_postings_format_feature_flag_enabled=true", Version.fromString("9.1.0"), null);
+    USE_LUCENE101_POSTINGS_FORMAT("es.use_lucene101_postings_format_feature_flag_enabled=true", Version.fromString("9.1.0"), null),
+    INFERENCE_CUSTOM_SERVICE_ENABLED("es.inference_custom_service_feature_flag_enabled=true", Version.fromString("8.19.0"), null);
 
     public final String systemProperty;
     public final Version from;

x-pack/plugin/inference/qa/inference-service-tests/src/javaRestTest/java/org/elasticsearch/xpack/inference/BaseMockEISAuthServerTest.java

@@ -14,6 +14,7 @@
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.test.cluster.ElasticsearchCluster;
+import org.elasticsearch.test.cluster.FeatureFlag;
 import org.elasticsearch.test.cluster.local.distribution.DistributionType;
 import org.elasticsearch.test.rest.ESRestTestCase;
 import org.junit.ClassRule;
@@ -46,6 +47,7 @@ public class BaseMockEISAuthServerTest extends ESRestTestCase {
         // This plugin is located in the inference/qa/test-service-plugin package, look for TestInferenceServicePlugin
         .plugin("inference-service-test")
         .user("x_pack_rest_user", "x-pack-test-password")
+        .feature(FeatureFlag.INFERENCE_CUSTOM_SERVICE_ENABLED)
         .build();
 
     // The reason we're doing this is to make sure the mock server is initialized first so we can get the address before communicating

x-pack/plugin/inference/qa/inference-service-tests/src/javaRestTest/java/org/elasticsearch/xpack/inference/InferenceBaseRestTest.java

@@ -20,6 +20,7 @@
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.inference.TaskType;
 import org.elasticsearch.test.cluster.ElasticsearchCluster;
+import org.elasticsearch.test.cluster.FeatureFlag;
 import org.elasticsearch.test.cluster.local.distribution.DistributionType;
 import org.elasticsearch.test.rest.ESRestTestCase;
 import org.elasticsearch.xcontent.XContentBuilder;
@@ -50,6 +51,7 @@ public class InferenceBaseRestTest extends ESRestTestCase {
         .setting("xpack.security.enabled", "true")
         .plugin("inference-service-test")
         .user("x_pack_rest_user", "x-pack-test-password")
+        .feature(FeatureFlag.INFERENCE_CUSTOM_SERVICE_ENABLED)
         .build();
 
     @ClassRule

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

@@ -0,0 +1,21 @@
+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference;
+
+import org.elasticsearch.common.util.FeatureFlag;
+
+public class CustomServiceFeatureFlag {
+    /**
+     * {@link org.elasticsearch.xpack.inference.services.custom.CustomService} feature flag. When the feature is complete,
+     * this flag will be removed.
+     * Enable feature via JVM option: `-Des.inference_custom_service_feature_flag_enabled=true`.
+     */
+    public static final FeatureFlag CUSTOM_SERVICE_FEATURE_FLAG = new FeatureFlag("inference_custom_service");
+
+    private CustomServiceFeatureFlag() {}
+}

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

@@ -114,6 +114,8 @@
 import java.util.ArrayList;
 import java.util.List;
 
+import static org.elasticsearch.xpack.inference.CustomServiceFeatureFlag.CUSTOM_SERVICE_FEATURE_FLAG;
+
 public class InferenceNamedWriteablesProvider {
 
     private InferenceNamedWriteablesProvider() {}
@@ -177,6 +179,10 @@ public static List<NamedWriteableRegistry.Entry> getNamedWriteables() {
     }
 
     private static void addCustomNamedWriteables(List<NamedWriteableRegistry.Entry> namedWriteables) {
+        if (CUSTOM_SERVICE_FEATURE_FLAG.isEnabled() == false) {
+            return;
+        }
+
         namedWriteables.add(
             new NamedWriteableRegistry.Entry(ServiceSettings.class, CustomServiceSettings.NAME, CustomServiceSettings::new)
         );

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

@@ -149,8 +149,10 @@
 import java.util.Set;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 import static java.util.Collections.singletonList;
+import static org.elasticsearch.xpack.inference.CustomServiceFeatureFlag.CUSTOM_SERVICE_FEATURE_FLAG;
 import static org.elasticsearch.xpack.inference.action.filter.ShardBulkInferenceActionFilter.INDICES_INFERENCE_BATCH_SIZE;
 import static org.elasticsearch.xpack.inference.common.InferenceAPIClusterAwareRateLimitingFeature.INFERENCE_API_CLUSTER_AWARE_RATE_LIMITING_FEATURE_FLAG;
 
@@ -380,7 +382,11 @@ public void loadExtensions(ExtensionLoader loader) {
     }
 
     public List<InferenceServiceExtension.Factory> getInferenceServiceFactories() {
-        return List.of(
+        List<InferenceServiceExtension.Factory> conditionalServices = CUSTOM_SERVICE_FEATURE_FLAG.isEnabled()
+            ? List.of(context -> new CustomService(httpFactory.get(), serviceComponents.get()))
+            : List.of();
+
+        List<InferenceServiceExtension.Factory> availableServices =  List.of(
             context -> new HuggingFaceElserService(httpFactory.get(), serviceComponents.get()),
             context -> new HuggingFaceService(httpFactory.get(), serviceComponents.get()),
             context -> new OpenAiService(httpFactory.get(), serviceComponents.get()),
@@ -397,9 +403,11 @@ public List<InferenceServiceExtension.Factory> getInferenceServiceFactories() {
             context -> new JinaAIService(httpFactory.get(), serviceComponents.get()),
             context -> new VoyageAIService(httpFactory.get(), serviceComponents.get()),
             context -> new DeepSeekService(httpFactory.get(), serviceComponents.get()),
-            context -> new CustomService(httpFactory.get(), serviceComponents.get()),
             ElasticsearchInternalService::new
         );
+
+        return Stream.concat(availableServices.stream(), conditionalServices.stream())
+            .toList();
     }
 
     @Override

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

@@ -206,7 +206,7 @@ public static void throwIfNotEmptyMap(Map<String, Object> settingsMap, String fi
     public static ElasticsearchStatusException unknownSettingsError(Map<String, Object> config, String serviceName) {
         // TODO map as JSON
         return new ElasticsearchStatusException(
-            "Model configuration contains settings [{}] unknown to the [{}] service",
+            "Configuration contains settings [{}] unknown to the [{}] service",
             RestStatus.BAD_REQUEST,
             config,
             serviceName
@@ -215,7 +215,7 @@ public static ElasticsearchStatusException unknownSettingsError(Map<String, Obje
 
     public static ElasticsearchStatusException unknownSettingsError(Map<String, Object> config, String field, String scope) {
         return new ElasticsearchStatusException(
-            "Model configuration contains unknown settings [{}] while parsing field [{}] for settings [{}]",
+            "Configuration contains unknown settings [{}] while parsing field [{}] for settings [{}]",
             RestStatus.BAD_REQUEST,
             config,
             field,