Enable engine factory to be pluggable (#31183)

This commit enables the engine factory to be pluggable based on index
settings used when creating the index service for an index.

server/src/main/java/org/elasticsearch/index/IndexModule.java

@@ -19,8 +19,8 @@
 
 package org.elasticsearch.index;
 
-import org.apache.lucene.search.similarities.Similarity;
 import org.apache.lucene.search.similarities.BM25Similarity;
+import org.apache.lucene.search.similarities.Similarity;
 import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.Version;
 import org.elasticsearch.client.Client;
@@ -60,6 +60,7 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.BiFunction;
@@ -104,8 +105,7 @@ public final class IndexModule {
 
     private final IndexSettings indexSettings;
     private final AnalysisRegistry analysisRegistry;
-    // pkg private so tests can mock
-    final SetOnce<EngineFactory> engineFactory = new SetOnce<>();
+    private final EngineFactory engineFactory;
     private SetOnce<IndexSearcherWrapperFactory> indexSearcherWrapper = new SetOnce<>();
     private final Set<IndexEventListener> indexEventListeners = new HashSet<>();
     private final Map<String, TriFunction<Settings, Version, ScriptService, Similarity>> similarities = new HashMap<>();
@@ -115,9 +115,18 @@ public final class IndexModule {
     private final List<IndexingOperationListener> indexOperationListeners = new ArrayList<>();
     private final AtomicBoolean frozen = new AtomicBoolean(false);
 
-    public IndexModule(IndexSettings indexSettings, AnalysisRegistry analysisRegistry) {
+    /**
+     * Construct the index module for the index with the specified index settings. The index module contains extension points for plugins
+     * via {@link org.elasticsearch.plugins.PluginsService#onIndexModule(IndexModule)}.
+     *
+     * @param indexSettings    the index settings
+     * @param analysisRegistry the analysis registry
+     * @param engineFactory    the engine factory
+     */
+    public IndexModule(final IndexSettings indexSettings, final AnalysisRegistry analysisRegistry, final EngineFactory engineFactory) {
         this.indexSettings = indexSettings;
         this.analysisRegistry = analysisRegistry;
+        this.engineFactory = Objects.requireNonNull(engineFactory);
         this.searchOperationListeners.add(new SearchSlowLog(indexSettings));
         this.indexOperationListeners.add(new IndexingSlowLog(indexSettings));
     }
@@ -158,6 +167,15 @@ public final class IndexModule {
         return indexSettings.getIndex();
     }
 
+    /**
+     * The engine factory provided during construction of this index module.
+     *
+     * @return the engine factory
+     */
+    EngineFactory getEngineFactory() {
+        return engineFactory;
+    }
+
     /**
      * Adds an {@link IndexEventListener} for this index. All listeners added here
      * are maintained for the entire index lifecycle on this node. Once an index is closed or deleted these
@@ -364,7 +382,7 @@ public final class IndexModule {
         }
         return new IndexService(indexSettings, environment, xContentRegistry,
                 new SimilarityService(indexSettings, scriptService, similarities),
-                shardStoreDeleter, analysisRegistry, engineFactory.get(), circuitBreakerService, bigArrays, threadPool, scriptService,
+                shardStoreDeleter, analysisRegistry, engineFactory, circuitBreakerService, bigArrays, threadPool, scriptService,
                 client, queryCache, store, eventListener, searcherWrapperFactory, mapperRegistry,
                 indicesFieldDataCache, searchOperationListeners, indexOperationListeners, namedWriteableRegistry);
     }

server/src/main/java/org/elasticsearch/index/IndexService.java

@@ -139,7 +139,7 @@ public class IndexService extends AbstractIndexComponent implements IndicesClust
             SimilarityService similarityService,
             ShardStoreDeleter shardStoreDeleter,
             AnalysisRegistry registry,
-            @Nullable EngineFactory engineFactory,
+            EngineFactory engineFactory,
             CircuitBreakerService circuitBreakerService,
             BigArrays bigArrays,
             ThreadPool threadPool,
@@ -188,7 +188,7 @@ public class IndexService extends AbstractIndexComponent implements IndicesClust
         this.warmer = new IndexWarmer(indexSettings.getSettings(), threadPool, indexFieldData,
             bitsetFilterCache.createListener(threadPool));
         this.indexCache = new IndexCache(indexSettings, queryCache, bitsetFilterCache);
-        this.engineFactory = engineFactory;
+        this.engineFactory = Objects.requireNonNull(engineFactory);
         // initialize this last -- otherwise if the wrapper requires any other member to be non-null we fail with an NPE
         this.searcherWrapper = wrapperFactory.newWrapper(this);
         this.searchOperationListeners = Collections.unmodifiableList(searchOperationListeners);
@@ -681,9 +681,9 @@ public class IndexService extends AbstractIndexComponent implements IndicesClust
         void addPendingDelete(ShardId shardId, IndexSettings indexSettings);
     }
 
-    final EngineFactory getEngineFactory() {
+    public final EngineFactory getEngineFactory() {
         return engineFactory;
-    } // pkg private for testing
+    }
 
     final IndexSearcherWrapper getSearcherWrapper() {
         return searcherWrapper;

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -82,7 +82,6 @@ import org.elasticsearch.index.engine.EngineConfig;
 import org.elasticsearch.index.engine.EngineException;
 import org.elasticsearch.index.engine.EngineFactory;
 import org.elasticsearch.index.engine.InternalEngine;
-import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.engine.RefreshFailedEngineException;
 import org.elasticsearch.index.engine.Segment;
 import org.elasticsearch.index.engine.SegmentsStats;
@@ -194,7 +193,7 @@ public class IndexShard extends AbstractIndexShardComponent implements IndicesCl
     protected volatile IndexShardState state;
     protected volatile long primaryTerm;
     protected final AtomicReference<Engine> currentEngineReference = new AtomicReference<>();
-    protected final EngineFactory engineFactory;
+    final EngineFactory engineFactory;
 
     private final IndexingOperationListener indexingOperationListeners;
     private final Runnable globalCheckpointSyncer;
@@ -267,7 +266,7 @@ public class IndexShard extends AbstractIndexShardComponent implements IndicesCl
         this.warmer = warmer;
         this.similarityService = similarityService;
         Objects.requireNonNull(store, "Store must be provided to the index shard");
-        this.engineFactory = engineFactory == null ? new InternalEngineFactory() : engineFactory;
+        this.engineFactory = Objects.requireNonNull(engineFactory);
         this.store = store;
         this.indexSortSupplier = indexSortSupplier;
         this.indexEventListener = indexEventListener;

server/src/main/java/org/elasticsearch/indices/IndicesModule.java

@@ -27,6 +27,8 @@ import org.elasticsearch.action.resync.TransportResyncReplicationAction;
 import org.elasticsearch.common.geo.ShapesAvailability;
 import org.elasticsearch.common.inject.AbstractModule;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry.Entry;
+import org.elasticsearch.index.IndexSettings;
+import org.elasticsearch.index.engine.EngineFactory;
 import org.elasticsearch.index.mapper.BinaryFieldMapper;
 import org.elasticsearch.index.mapper.BooleanFieldMapper;
 import org.elasticsearch.index.mapper.CompletionFieldMapper;
@@ -60,10 +62,12 @@ import org.elasticsearch.indices.store.TransportNodesListShardStoreMetaData;
 import org.elasticsearch.plugins.MapperPlugin;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.function.Predicate;
@@ -234,4 +238,9 @@ public class IndicesModule extends AbstractModule {
     public MapperRegistry getMapperRegistry() {
         return mapperRegistry;
     }
+
+    public Collection<Function<IndexSettings, Optional<EngineFactory>>> getEngineFactories() {
+        return Collections.emptyList();
+    }
+
 }

server/src/main/java/org/elasticsearch/indices/IndicesService.java

@@ -25,7 +25,6 @@ import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.store.AlreadyClosedException;
 import org.apache.lucene.store.LockObtainFailedException;
 import org.apache.lucene.util.CollectionUtil;
-import org.elasticsearch.core.internal.io.IOUtils;
 import org.apache.lucene.util.RamUsageEstimator;
 import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ResourceAlreadyExistsException;
@@ -45,6 +44,7 @@ import org.elasticsearch.common.CheckedFunction;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.breaker.CircuitBreaker;
 import org.elasticsearch.common.bytes.BytesReference;
+import org.elasticsearch.common.collect.Tuple;
 import org.elasticsearch.common.component.AbstractLifecycleComponent;
 import org.elasticsearch.common.io.FileSystemUtils;
 import org.elasticsearch.common.io.stream.BytesStreamOutput;
@@ -67,6 +67,7 @@ import org.elasticsearch.common.xcontent.NamedXContentRegistry;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.common.xcontent.XContentType;
+import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.env.ShardLock;
 import org.elasticsearch.env.ShardLockObtainFailedException;
@@ -79,6 +80,8 @@ import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.analysis.AnalysisRegistry;
 import org.elasticsearch.index.cache.request.ShardRequestCache;
+import org.elasticsearch.index.engine.EngineFactory;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.fielddata.IndexFieldDataCache;
 import org.elasticsearch.index.flush.FlushStats;
 import org.elasticsearch.index.get.GetStats;
@@ -116,10 +119,14 @@ import java.io.Closeable;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutorService;
@@ -172,6 +179,7 @@ public class IndicesService extends AbstractLifecycleComponent
     private final IndicesRequestCache indicesRequestCache;
     private final IndicesQueryCache indicesQueryCache;
     private final MetaStateService metaStateService;
+    private final Collection<Function<IndexSettings, Optional<EngineFactory>>> engineFactoryProviders;
 
     @Override
     protected void doStart() {
@@ -183,7 +191,8 @@ public class IndicesService extends AbstractLifecycleComponent
                           AnalysisRegistry analysisRegistry, IndexNameExpressionResolver indexNameExpressionResolver,
                           MapperRegistry mapperRegistry, NamedWriteableRegistry namedWriteableRegistry, ThreadPool threadPool,
                           IndexScopedSettings indexScopedSettings, CircuitBreakerService circuitBreakerService, BigArrays bigArrays,
-                          ScriptService scriptService, Client client, MetaStateService metaStateService) {
+                          ScriptService scriptService, Client client, MetaStateService metaStateService,
+                          Collection<Function<IndexSettings, Optional<EngineFactory>>> engineFactoryProviders) {
         super(settings);
         this.threadPool = threadPool;
         this.pluginsService = pluginsService;
@@ -214,6 +223,7 @@ public class IndicesService extends AbstractLifecycleComponent
         this.cleanInterval = INDICES_CACHE_CLEAN_INTERVAL_SETTING.get(settings);
         this.cacheCleaner = new CacheCleaner(indicesFieldDataCache, indicesRequestCache,  logger, threadPool, this.cleanInterval);
         this.metaStateService = metaStateService;
+        this.engineFactoryProviders = engineFactoryProviders;
     }
 
     @Override
@@ -442,7 +452,7 @@ public class IndicesService extends AbstractLifecycleComponent
             idxSettings.getNumberOfReplicas(),
             reason);
 
-        final IndexModule indexModule = new IndexModule(idxSettings, analysisRegistry);
+        final IndexModule indexModule = new IndexModule(idxSettings, analysisRegistry, getEngineFactory(idxSettings));
         for (IndexingOperationListener operationListener : indexingOperationListeners) {
             indexModule.addIndexOperationListener(operationListener);
         }
@@ -466,6 +476,34 @@ public class IndicesService extends AbstractLifecycleComponent
         );
     }
 
+    private EngineFactory getEngineFactory(final IndexSettings idxSettings) {
+        final List<Optional<EngineFactory>> engineFactories =
+                engineFactoryProviders
+                        .stream()
+                        .map(engineFactoryProvider -> engineFactoryProvider.apply(idxSettings))
+                        .filter(maybe -> Objects.requireNonNull(maybe).isPresent())
+                        .collect(Collectors.toList());
+        if (engineFactories.isEmpty()) {
+            return new InternalEngineFactory();
+        } else if (engineFactories.size() == 1) {
+            assert engineFactories.get(0).isPresent();
+            return engineFactories.get(0).get();
+        } else {
+            final String message = String.format(
+                    Locale.ROOT,
+                    "multiple engine factories provided for %s: %s",
+                    idxSettings.getIndex(),
+                    engineFactories
+                            .stream()
+                            .map(t -> {
+                                assert t.isPresent();
+                                return "[" + t.get().getClass().getName() + "]";
+                            })
+                            .collect(Collectors.joining(",")));
+            throw new IllegalStateException(message);
+        }
+    }
+
     /**
      * creates a new mapper service for the given index, in order to do administrative work like mapping updates.
      * This *should not* be used for document parsing. Doing so will result in an exception.
@@ -474,7 +512,7 @@ public class IndicesService extends AbstractLifecycleComponent
      */
     public synchronized MapperService createIndexMapperService(IndexMetaData indexMetaData) throws IOException {
         final IndexSettings idxSettings = new IndexSettings(indexMetaData, this.settings, indexScopedSettings);
-        final IndexModule indexModule = new IndexModule(idxSettings, analysisRegistry);
+        final IndexModule indexModule = new IndexModule(idxSettings, analysisRegistry, getEngineFactory(idxSettings));
         pluginsService.onIndexModule(indexModule);
         return indexModule.newIndexMapperService(xContentRegistry, mapperRegistry, scriptService);
     }

server/src/main/java/org/elasticsearch/node/Node.java

@@ -21,7 +21,6 @@ package org.elasticsearch.node;
 
 import org.apache.logging.log4j.Logger;
 import org.apache.lucene.util.Constants;
-import org.elasticsearch.core.internal.io.IOUtils;
 import org.apache.lucene.util.SetOnce;
 import org.elasticsearch.Build;
 import org.elasticsearch.ElasticsearchException;
@@ -58,12 +57,10 @@ import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.StopWatch;
 import org.elasticsearch.common.component.Lifecycle;
 import org.elasticsearch.common.component.LifecycleComponent;
-import org.elasticsearch.common.inject.Binder;
 import org.elasticsearch.common.inject.Injector;
 import org.elasticsearch.common.inject.Key;
 import org.elasticsearch.common.inject.Module;
 import org.elasticsearch.common.inject.ModulesBuilder;
-import org.elasticsearch.common.inject.util.Providers;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.lease.Releasables;
 import org.elasticsearch.common.logging.DeprecationLogger;
@@ -82,6 +79,7 @@ import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.BigArrays;
 import org.elasticsearch.common.util.PageCacheRecycler;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.discovery.Discovery;
 import org.elasticsearch.discovery.DiscoveryModule;
 import org.elasticsearch.discovery.DiscoverySettings;
@@ -93,8 +91,10 @@ import org.elasticsearch.gateway.GatewayModule;
 import org.elasticsearch.gateway.GatewayService;
 import org.elasticsearch.gateway.MetaStateService;
 import org.elasticsearch.http.HttpServerTransport;
-import org.elasticsearch.http.HttpTransportSettings;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.analysis.AnalysisRegistry;
+import org.elasticsearch.index.engine.Engine;
+import org.elasticsearch.index.engine.EngineFactory;
 import org.elasticsearch.indices.IndicesModule;
 import org.elasticsearch.indices.IndicesService;
 import org.elasticsearch.indices.analysis.AnalysisModule;
@@ -109,10 +109,15 @@ import org.elasticsearch.indices.store.IndicesStore;
 import org.elasticsearch.ingest.IngestService;
 import org.elasticsearch.monitor.MonitorService;
 import org.elasticsearch.monitor.jvm.JvmInfo;
+import org.elasticsearch.persistent.PersistentTasksClusterService;
+import org.elasticsearch.persistent.PersistentTasksExecutor;
+import org.elasticsearch.persistent.PersistentTasksExecutorRegistry;
+import org.elasticsearch.persistent.PersistentTasksService;
 import org.elasticsearch.plugins.ActionPlugin;
 import org.elasticsearch.plugins.AnalysisPlugin;
 import org.elasticsearch.plugins.ClusterPlugin;
 import org.elasticsearch.plugins.DiscoveryPlugin;
+import org.elasticsearch.plugins.EnginePlugin;
 import org.elasticsearch.plugins.IngestPlugin;
 import org.elasticsearch.plugins.MapperPlugin;
 import org.elasticsearch.plugins.MetaDataUpgrader;
@@ -140,10 +145,6 @@ import org.elasticsearch.transport.TransportInterceptor;
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.usage.UsageService;
 import org.elasticsearch.watcher.ResourceWatcherService;
-import org.elasticsearch.persistent.PersistentTasksClusterService;
-import org.elasticsearch.persistent.PersistentTasksExecutor;
-import org.elasticsearch.persistent.PersistentTasksExecutorRegistry;
-import org.elasticsearch.persistent.PersistentTasksService;
 
 import java.io.BufferedWriter;
 import java.io.Closeable;
@@ -161,6 +162,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
@@ -395,11 +397,21 @@ public class Node implements Closeable {
                 .flatMap(Function.identity()).collect(toList()));
             modules.add(new RepositoriesModule(this.environment, pluginsService.filterPlugins(RepositoryPlugin.class), xContentRegistry));
             final MetaStateService metaStateService = new MetaStateService(settings, nodeEnvironment, xContentRegistry);
-            final IndicesService indicesService = new IndicesService(settings, pluginsService, nodeEnvironment, xContentRegistry,
-                    analysisModule.getAnalysisRegistry(),
-                clusterModule.getIndexNameExpressionResolver(), indicesModule.getMapperRegistry(), namedWriteableRegistry,
-                threadPool, settingsModule.getIndexScopedSettings(), circuitBreakerService, bigArrays, scriptModule.getScriptService(),
-                client, metaStateService);
+
+            // collect engine factory providers from server and from plugins
+            final Collection<EnginePlugin> enginePlugins = pluginsService.filterPlugins(EnginePlugin.class);
+            final Collection<Function<IndexSettings, Optional<EngineFactory>>> engineFactoryProviders =
+                    Stream.concat(
+                            indicesModule.getEngineFactories().stream(),
+                            enginePlugins.stream().map(plugin -> plugin::getEngineFactory))
+                    .collect(Collectors.toList());
+
+            final IndicesService indicesService =
+                    new IndicesService(settings, pluginsService, nodeEnvironment, xContentRegistry, analysisModule.getAnalysisRegistry(),
+                            clusterModule.getIndexNameExpressionResolver(), indicesModule.getMapperRegistry(), namedWriteableRegistry,
+                            threadPool, settingsModule.getIndexScopedSettings(), circuitBreakerService, bigArrays,
+                            scriptModule.getScriptService(), client, metaStateService, engineFactoryProviders);
+
 
             Collection<Object> pluginComponents = pluginsService.filterPlugins(Plugin.class).stream()
                 .flatMap(p -> p.createComponents(client, clusterService, threadPool, resourceWatcherService,

server/src/main/java/org/elasticsearch/plugins/EnginePlugin.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.plugins;
+
+import org.elasticsearch.index.IndexSettings;
+import org.elasticsearch.index.engine.EngineFactory;
+
+import java.util.Optional;
+
+/**
+ * A plugin that provides alternative engine implementations.
+ */
+public interface EnginePlugin {
+
+    /**
+     * When an index is created this method is invoked for each engine plugin. Engine plugins can inspect the index settings to determine
+     * whether or not to provide an engine factory for the given index. A plugin that is not overriding the default engine should return
+     * {@link Optional#empty()}. If multiple plugins return an engine factory for a given index the index will not be created and an
+     * {@link IllegalStateException} will be thrown during index creation.
+     *
+     * @return an optional engine factory
+     */
+    Optional<EngineFactory> getEngineFactory(IndexSettings indexSettings);
+
+}

server/src/test/java/org/elasticsearch/index/IndexModuleTests.java

@@ -30,7 +30,6 @@ import org.apache.lucene.search.TermStatistics;
 import org.apache.lucene.search.Weight;
 import org.apache.lucene.search.similarities.BM25Similarity;
 import org.apache.lucene.search.similarities.Similarity;
-import org.elasticsearch.core.internal.io.IOUtils;
 import org.apache.lucene.util.SetOnce.AlreadySetException;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
@@ -40,6 +39,7 @@ import org.elasticsearch.common.settings.Setting.Property;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.BigArrays;
 import org.elasticsearch.common.util.PageCacheRecycler;
+import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.NodeEnvironment;
 import org.elasticsearch.env.ShardLock;
@@ -50,6 +50,7 @@ import org.elasticsearch.index.cache.query.IndexQueryCache;
 import org.elasticsearch.index.cache.query.QueryCache;
 import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineException;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.engine.InternalEngineTests;
 import org.elasticsearch.index.fielddata.IndexFieldDataCache;
 import org.elasticsearch.index.mapper.ParsedDocument;
@@ -146,13 +147,12 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testWrapperIsBound() throws IOException {
-        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry);
+        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry, new MockEngineFactory(AssertingDirectoryReader.class));
         module.setSearcherWrapper((s) -> new Wrapper());
-        module.engineFactory.set(new MockEngineFactory(AssertingDirectoryReader.class));
 
         IndexService indexService = newIndexService(module);
         assertTrue(indexService.getSearcherWrapper() instanceof Wrapper);
-        assertSame(indexService.getEngineFactory(), module.engineFactory.get());
+        assertSame(indexService.getEngineFactory(), module.getEngineFactory());
         indexService.close("simon says", false);
     }
 
@@ -165,7 +165,7 @@ public class IndexModuleTests extends ESTestCase {
             .put(IndexModule.INDEX_STORE_TYPE_SETTING.getKey(), "foo_store")
             .build();
         IndexSettings indexSettings = IndexSettingsModule.newIndexSettings(index, settings);
-        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry);
+        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry, new InternalEngineFactory());
         module.addIndexStore("foo_store", FooStore::new);
         try {
             module.addIndexStore("foo_store", FooStore::new);
@@ -189,7 +189,7 @@ public class IndexModuleTests extends ESTestCase {
             }
         };
         IndexSettings indexSettings = IndexSettingsModule.newIndexSettings(index, settings);
-        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry);
+        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry, new InternalEngineFactory());
         module.addIndexEventListener(eventListener);
         IndexService indexService = newIndexService(module);
         IndexSettings x = indexService.getIndexSettings();
@@ -203,7 +203,8 @@ public class IndexModuleTests extends ESTestCase {
 
     public void testListener() throws IOException {
         Setting<Boolean> booleanSetting = Setting.boolSetting("index.foo.bar", false, Property.Dynamic, Property.IndexScope);
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings(index, settings, booleanSetting), emptyAnalysisRegistry);
+        final IndexSettings indexSettings = IndexSettingsModule.newIndexSettings(index, settings, booleanSetting);
+        IndexModule module = new IndexModule(indexSettings, emptyAnalysisRegistry, new InternalEngineFactory());
         Setting<Boolean> booleanSetting2 = Setting.boolSetting("index.foo.bar.baz", false, Property.Dynamic, Property.IndexScope);
         AtomicBoolean atomicBoolean = new AtomicBoolean(false);
         module.addSettingsUpdateConsumer(booleanSetting, atomicBoolean::set);
@@ -222,7 +223,8 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testAddIndexOperationListener() throws IOException {
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings(index, settings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings(index, settings), emptyAnalysisRegistry, new InternalEngineFactory());
         AtomicBoolean executed = new AtomicBoolean(false);
         IndexingOperationListener listener = new IndexingOperationListener() {
             @Override
@@ -252,7 +254,8 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testAddSearchOperationListener() throws IOException {
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings(index, settings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings(index, settings), emptyAnalysisRegistry, new InternalEngineFactory());
         AtomicBoolean executed = new AtomicBoolean(false);
         SearchOperationListener listener = new SearchOperationListener() {
 
@@ -279,13 +282,14 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testAddSimilarity() throws IOException {
-        Settings indexSettings = Settings.builder()
+        Settings settings = Settings.builder()
                 .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
                 .put("index.similarity.my_similarity.type", "test_similarity")
                 .put("index.similarity.my_similarity.key", "there is a key")
                 .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toString())
                 .build();
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings("foo", indexSettings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings("foo", settings), emptyAnalysisRegistry, new InternalEngineFactory());
         module.addSimilarity("test_similarity",
                 (providerSettings, indexCreatedVersion, scriptService) -> new TestSimilarity(providerSettings.get("key")));
 
@@ -299,7 +303,8 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testFrozen() {
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings(index, settings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings(index, settings), emptyAnalysisRegistry, new InternalEngineFactory());
         module.freeze();
         String msg = "Can't modify IndexModule once the index service has been created";
         assertEquals(msg, expectThrows(IllegalStateException.class, () -> module.addSearchOperationListener(null)).getMessage());
@@ -312,32 +317,35 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testSetupUnknownSimilarity() throws IOException {
-        Settings indexSettings = Settings.builder()
+        Settings settings = Settings.builder()
                 .put("index.similarity.my_similarity.type", "test_similarity")
                 .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
                 .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toString())
                 .build();
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings("foo", indexSettings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings("foo", settings), emptyAnalysisRegistry, new InternalEngineFactory());
         Exception ex = expectThrows(IllegalArgumentException.class, () -> newIndexService(module));
         assertEquals("Unknown Similarity type [test_similarity] for [my_similarity]", ex.getMessage());
     }
 
     public void testSetupWithoutType() throws IOException {
-        Settings indexSettings = Settings.builder()
+        Settings settings = Settings.builder()
                 .put("index.similarity.my_similarity.foo", "bar")
                 .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toString())
                 .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
                 .build();
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings("foo", indexSettings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings("foo", settings), emptyAnalysisRegistry, new InternalEngineFactory());
         Exception ex = expectThrows(IllegalArgumentException.class, () -> newIndexService(module));
         assertEquals("Similarity [my_similarity] must have an associated type", ex.getMessage());
     }
 
     public void testForceCustomQueryCache() throws IOException {
-        Settings indexSettings = Settings.builder()
+        Settings settings = Settings.builder()
                 .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toString())
                 .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT).build();
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings("foo", indexSettings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings("foo", settings), emptyAnalysisRegistry, new InternalEngineFactory());
         module.forceQueryCacheProvider((a, b) -> new CustomQueryCache());
         expectThrows(AlreadySetException.class, () -> module.forceQueryCacheProvider((a, b) -> new CustomQueryCache()));
         IndexService indexService = newIndexService(module);
@@ -346,21 +354,23 @@ public class IndexModuleTests extends ESTestCase {
     }
 
     public void testDefaultQueryCacheImplIsSelected() throws IOException {
-        Settings indexSettings = Settings.builder()
+        Settings settings = Settings.builder()
                 .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toString())
                 .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT).build();
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings("foo", indexSettings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings("foo", settings), emptyAnalysisRegistry, new InternalEngineFactory());
         IndexService indexService = newIndexService(module);
         assertTrue(indexService.cache().query() instanceof IndexQueryCache);
         indexService.close("simon says", false);
     }
 
     public void testDisableQueryCacheHasPrecedenceOverForceQueryCache() throws IOException {
-        Settings indexSettings = Settings.builder()
+        Settings settings = Settings.builder()
             .put(IndexModule.INDEX_QUERY_CACHE_ENABLED_SETTING.getKey(), false)
             .put(Environment.PATH_HOME_SETTING.getKey(), createTempDir().toString())
             .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT).build();
-        IndexModule module = new IndexModule(IndexSettingsModule.newIndexSettings("foo", indexSettings), emptyAnalysisRegistry);
+        IndexModule module =
+                new IndexModule(IndexSettingsModule.newIndexSettings("foo", settings), emptyAnalysisRegistry, new InternalEngineFactory());
         module.forceQueryCacheProvider((a, b) -> new CustomQueryCache());
         IndexService indexService = newIndexService(module);
         assertTrue(indexService.cache().query() instanceof DisabledQueryCache);

server/src/test/java/org/elasticsearch/index/replication/ESIndexLevelReplicationTestCase.java

@@ -60,6 +60,7 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.index.engine.EngineFactory;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.seqno.GlobalCheckpointSyncAction;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.index.shard.IndexShardTestCase;
@@ -160,7 +161,7 @@ public abstract class ESIndexLevelReplicationTestCase extends IndexShardTestCase
         }
 
         protected EngineFactory getEngineFactory(ShardRouting routing) {
-            return null;
+            return new InternalEngineFactory();
         }
 
         public int indexDocs(final int numOfDoc) throws Exception {

server/src/test/java/org/elasticsearch/index/replication/RecoveryDuringReplicationTests.java

@@ -38,6 +38,7 @@ import org.elasticsearch.index.VersionType;
 import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineConfig;
 import org.elasticsearch.index.engine.EngineFactory;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.engine.InternalEngineTests;
 import org.elasticsearch.index.mapper.SourceToParse;
 import org.elasticsearch.index.shard.IndexShard;
@@ -406,7 +407,7 @@ public class RecoveryDuringReplicationTests extends ESIndexLevelReplicationTestC
                 if (routing.primary()) {
                     return primaryEngineFactory;
                 } else {
-                    return null;
+                    return new InternalEngineFactory();
                 }
             }
         }) {
@@ -500,7 +501,7 @@ public class RecoveryDuringReplicationTests extends ESIndexLevelReplicationTestC
                     @Override
                     protected EngineFactory getEngineFactory(final ShardRouting routing) {
                         if (routing.primary()) {
-                            return null;
+                            return new InternalEngineFactory();
                         } else {
                             return replicaEngineFactory;
                         }

server/src/test/java/org/elasticsearch/index/shard/IndexShardTests.java

@@ -76,6 +76,7 @@ import org.elasticsearch.index.VersionType;
 import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineException;
 import org.elasticsearch.index.engine.InternalEngine;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.engine.Segment;
 import org.elasticsearch.index.engine.SegmentsStats;
 import org.elasticsearch.index.fielddata.FieldDataStats;
@@ -838,7 +839,8 @@ public class IndexShardTests extends IndexShardTestCase {
                 .build();
         final IndexMetaData.Builder indexMetadata = IndexMetaData.builder(shardRouting.getIndexName()).settings(settings).primaryTerm(0, 1);
         final AtomicBoolean synced = new AtomicBoolean();
-        final IndexShard primaryShard = newShard(shardRouting, indexMetadata.build(), null, null, () -> { synced.set(true); });
+        final IndexShard primaryShard =
+                newShard(shardRouting, indexMetadata.build(), null, new InternalEngineFactory(), () -> synced.set(true));
         // add a replica
         recoverShardFromStore(primaryShard);
         final IndexShard replicaShard = newShard(shardId, false);
@@ -1885,8 +1887,13 @@ public class IndexShardTests extends IndexShardTestCase {
         };
         closeShards(shard);
         IndexShard newShard = newShard(
-            ShardRoutingHelper.initWithSameId(shard.routingEntry(), RecoverySource.StoreRecoverySource.EXISTING_STORE_INSTANCE),
-            shard.shardPath(), shard.indexSettings().getIndexMetaData(), wrapper, null, () -> {}, EMPTY_EVENT_LISTENER);
+                ShardRoutingHelper.initWithSameId(shard.routingEntry(), RecoverySource.StoreRecoverySource.EXISTING_STORE_INSTANCE),
+                shard.shardPath(),
+                shard.indexSettings().getIndexMetaData(),
+                wrapper,
+                new InternalEngineFactory(),
+                () -> {},
+                EMPTY_EVENT_LISTENER);
 
         recoverShardFromStore(newShard);
 
@@ -2032,8 +2039,13 @@ public class IndexShardTests extends IndexShardTestCase {
 
         closeShards(shard);
         IndexShard newShard = newShard(
-            ShardRoutingHelper.initWithSameId(shard.routingEntry(), RecoverySource.StoreRecoverySource.EXISTING_STORE_INSTANCE),
-            shard.shardPath(), shard.indexSettings().getIndexMetaData(), wrapper, null, () -> {}, EMPTY_EVENT_LISTENER);
+                ShardRoutingHelper.initWithSameId(shard.routingEntry(), RecoverySource.StoreRecoverySource.EXISTING_STORE_INSTANCE),
+                shard.shardPath(),
+                shard.indexSettings().getIndexMetaData(),
+                wrapper,
+                new InternalEngineFactory(),
+                () -> {},
+                EMPTY_EVENT_LISTENER);
 
         recoverShardFromStore(newShard);
 
@@ -3016,7 +3028,7 @@ public class IndexShardTests extends IndexShardTestCase {
         ShardPath shardPath = new ShardPath(false, nodePath.resolve(shardId), nodePath.resolve(shardId), shardId);
         AtomicBoolean markedInactive = new AtomicBoolean();
         AtomicReference<IndexShard> primaryRef = new AtomicReference<>();
-        IndexShard primary = newShard(shardRouting, shardPath, metaData, null, null, () -> {
+        IndexShard primary = newShard(shardRouting, shardPath, metaData, null, new InternalEngineFactory(), () -> {
         }, new IndexEventListener() {
             @Override
             public void onShardInactive(IndexShard indexShard) {

server/src/test/java/org/elasticsearch/indices/IndicesServiceTests.java

@@ -31,6 +31,7 @@ import org.elasticsearch.cluster.metadata.MetaData;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.UUIDs;
 import org.elasticsearch.common.io.FileSystemUtils;
+import org.elasticsearch.common.settings.Setting;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.env.NodeEnvironment;
@@ -42,6 +43,11 @@ import org.elasticsearch.index.Index;
 import org.elasticsearch.index.IndexModule;
 import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.IndexSettings;
+import org.elasticsearch.index.engine.Engine;
+import org.elasticsearch.index.engine.EngineConfig;
+import org.elasticsearch.index.engine.EngineFactory;
+import org.elasticsearch.index.engine.InternalEngine;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.mapper.KeywordFieldMapper;
 import org.elasticsearch.index.mapper.Mapper;
 import org.elasticsearch.index.mapper.MapperService;
@@ -51,10 +57,12 @@ import org.elasticsearch.index.shard.IndexShardState;
 import org.elasticsearch.index.shard.ShardId;
 import org.elasticsearch.index.shard.ShardPath;
 import org.elasticsearch.indices.IndicesService.ShardDeletionCheckResult;
+import org.elasticsearch.plugins.EnginePlugin;
 import org.elasticsearch.plugins.MapperPlugin;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.test.ESSingleNodeTestCase;
 import org.elasticsearch.test.IndexSettingsModule;
+import org.elasticsearch.test.hamcrest.RegexMatcher;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -63,14 +71,18 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static org.elasticsearch.action.support.WriteRequest.RefreshPolicy.IMMEDIATE;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertHitCount;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.hasToString;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.not;
 import static org.mockito.Mockito.mock;
@@ -88,9 +100,70 @@ public class IndicesServiceTests extends ESSingleNodeTestCase {
 
     @Override
     protected Collection<Class<? extends Plugin>> getPlugins() {
-        ArrayList<Class<? extends Plugin>> plugins = new ArrayList<>(super.getPlugins());
-        plugins.add(TestPlugin.class);
-        return plugins;
+        return Stream.concat(
+                super.getPlugins().stream(),
+                Stream.of(TestPlugin.class, FooEnginePlugin.class, BarEnginePlugin.class))
+                .collect(Collectors.toList());
+    }
+
+    public static class FooEnginePlugin extends Plugin implements EnginePlugin {
+
+        static class FooEngineFactory implements EngineFactory {
+
+            @Override
+            public Engine newReadWriteEngine(final EngineConfig config) {
+                return new InternalEngine(config);
+            }
+
+        }
+
+        private static final Setting<Boolean> FOO_INDEX_SETTING =
+                Setting.boolSetting("index.foo_index", false, Setting.Property.IndexScope);
+
+        @Override
+        public List<Setting<?>> getSettings() {
+            return Collections.singletonList(FOO_INDEX_SETTING);
+        }
+
+        @Override
+        public Optional<EngineFactory> getEngineFactory(final IndexSettings indexSettings) {
+            if (FOO_INDEX_SETTING.get(indexSettings.getSettings())) {
+                return Optional.of(new FooEngineFactory());
+            } else {
+                return Optional.empty();
+            }
+        }
+
+    }
+
+    public static class BarEnginePlugin extends Plugin implements EnginePlugin {
+
+        static class BarEngineFactory implements EngineFactory {
+
+            @Override
+            public Engine newReadWriteEngine(final EngineConfig config) {
+                return new InternalEngine(config);
+            }
+
+        }
+
+        private static final Setting<Boolean> BAR_INDEX_SETTING =
+                Setting.boolSetting("index.bar_index", false, Setting.Property.IndexScope);
+
+        @Override
+        public List<Setting<?>> getSettings() {
+            return Collections.singletonList(BAR_INDEX_SETTING);
+        }
+
+        @Override
+        public Optional<EngineFactory> getEngineFactory(final IndexSettings indexSettings) {
+            if (BAR_INDEX_SETTING.get(indexSettings.getSettings())) {
+                return Optional.of(new BarEngineFactory());
+            } else {
+                return Optional.empty();
+            }
+        }
+
     }
 
     public static class TestPlugin extends Plugin implements MapperPlugin {
@@ -438,4 +511,56 @@ public class IndicesServiceTests extends ESSingleNodeTestCase {
             assertTrue(indicesService.isMetaDataField(builtIn));
         }
     }
+
+    public void testGetEngineFactory() throws IOException {
+        final IndicesService indicesService = getIndicesService();
+
+        final Boolean[] values = new Boolean[] { true, false, null };
+        for (final Boolean value : values) {
+            final String indexName = "foo-" + value;
+            final Index index = new Index(indexName, UUIDs.randomBase64UUID());
+            final Settings.Builder builder = Settings.builder()
+                    .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                    .put(IndexMetaData.SETTING_INDEX_UUID, index.getUUID());
+            if (value != null) {
+                builder.put(FooEnginePlugin.FOO_INDEX_SETTING.getKey(), value);
+            }
+
+            final IndexMetaData indexMetaData = new IndexMetaData.Builder(index.getName())
+                    .settings(builder.build())
+                    .numberOfShards(1)
+                    .numberOfReplicas(0)
+                    .build();
+            final IndexService indexService = indicesService.createIndex(indexMetaData, Collections.emptyList());
+            if (value != null && value) {
+                assertThat(indexService.getEngineFactory(), instanceOf(FooEnginePlugin.FooEngineFactory.class));
+            } else {
+                assertThat(indexService.getEngineFactory(), instanceOf(InternalEngineFactory.class));
+            }
+        }
+    }
+
+    public void testConflictingEngineFactories() throws IOException {
+        final String indexName = "foobar";
+        final Index index = new Index(indexName, UUIDs.randomBase64UUID());
+        final Settings settings = Settings.builder()
+                .put(IndexMetaData.SETTING_VERSION_CREATED, Version.CURRENT)
+                .put(IndexMetaData.SETTING_INDEX_UUID, index.getUUID())
+                .put(FooEnginePlugin.FOO_INDEX_SETTING.getKey(), true)
+                .put(BarEnginePlugin.BAR_INDEX_SETTING.getKey(), true)
+                .build();
+        final IndexMetaData indexMetaData = new IndexMetaData.Builder(index.getName())
+                .settings(settings)
+                .numberOfShards(1)
+                .numberOfReplicas(0)
+                .build();
+
+        final IndicesService indicesService = getIndicesService();
+        final IllegalStateException e =
+                expectThrows(IllegalStateException.class, () -> indicesService.createIndex(indexMetaData, Collections.emptyList()));
+        final String pattern =
+                ".*multiple engine factories provided for \\[foobar/.*\\]: \\[.*FooEngineFactory\\],\\[.*BarEngineFactory\\].*";
+        assertThat(e, hasToString(new RegexMatcher(pattern)));
+    }
+
 }

server/src/test/java/org/elasticsearch/repositories/blobstore/BlobStoreRepositoryRestoreTests.java

@@ -29,6 +29,7 @@ import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.internal.io.IOUtils;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.TestEnvironment;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.index.shard.IndexShardState;
 import org.elasticsearch.index.shard.IndexShardTestCase;
@@ -99,8 +100,14 @@ public class BlobStoreRepositoryRestoreTests extends IndexShardTestCase {
 
             // build a new shard using the same store directory as the closed shard
             ShardRouting shardRouting = ShardRoutingHelper.initWithSameId(shard.routingEntry(), EXISTING_STORE_INSTANCE);
-            shard = newShard(shardRouting, shard.shardPath(), shard.indexSettings().getIndexMetaData(), null, null, () -> {},
-                EMPTY_EVENT_LISTENER);
+            shard = newShard(
+                    shardRouting,
+                    shard.shardPath(),
+                    shard.indexSettings().getIndexMetaData(),
+                    null,
+                    new InternalEngineFactory(),
+                    () -> {},
+                    EMPTY_EVENT_LISTENER);
 
             // restore the shard
             recoverShardFromSnapshot(shard, snapshot, repository);

test/framework/src/main/java/org/elasticsearch/index/MockEngineFactoryPlugin.java

@@ -20,25 +20,23 @@ package org.elasticsearch.index;
 
 import org.apache.lucene.index.AssertingDirectoryReader;
 import org.apache.lucene.index.FilterDirectoryReader;
-import org.elasticsearch.common.inject.AbstractModule;
-import org.elasticsearch.common.inject.Module;
 import org.elasticsearch.common.settings.Setting;
-import org.elasticsearch.common.settings.SettingsModule;
+import org.elasticsearch.index.engine.EngineFactory;
+import org.elasticsearch.plugins.EnginePlugin;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.test.engine.MockEngineFactory;
 import org.elasticsearch.test.engine.MockEngineSupport;
 
 import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
 
 /**
  * A plugin to use {@link MockEngineFactory}.
  *
  * Subclasses may override the reader wrapper used.
  */
-public class MockEngineFactoryPlugin extends Plugin {
+public class MockEngineFactoryPlugin extends Plugin implements EnginePlugin {
 
     @Override
     public List<Setting<?>> getSettings() {
@@ -46,8 +44,8 @@ public class MockEngineFactoryPlugin extends Plugin {
     }
 
     @Override
-    public void onIndexModule(IndexModule module) {
-        module.engineFactory.set(new MockEngineFactory(getReaderWrapperClass()));
+    public Optional<EngineFactory> getEngineFactory(final IndexSettings indexSettings) {
+        return Optional.of(new MockEngineFactory(getReaderWrapperClass()));
     }
 
     protected Class<? extends FilterDirectoryReader> getReaderWrapperClass() {

test/framework/src/main/java/org/elasticsearch/index/shard/IndexShardTestCase.java

@@ -56,6 +56,7 @@ import org.elasticsearch.index.cache.query.DisabledQueryCache;
 import org.elasticsearch.index.engine.Engine;
 import org.elasticsearch.index.engine.EngineFactory;
 import org.elasticsearch.index.engine.EngineTestCase;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.index.mapper.IdFieldMapper;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.SourceToParse;
@@ -227,7 +228,7 @@ public abstract class IndexShardTestCase extends ESTestCase {
                                   @Nullable IndexSearcherWrapper searcherWrapper, Runnable globalCheckpointSyncer) throws IOException {
         ShardRouting shardRouting = TestShardRouting.newShardRouting(shardId, nodeId, primary, ShardRoutingState.INITIALIZING,
             primary ? RecoverySource.StoreRecoverySource.EMPTY_STORE_INSTANCE : RecoverySource.PeerRecoverySource.INSTANCE);
-        return newShard(shardRouting, indexMetaData, searcherWrapper, null, globalCheckpointSyncer);
+        return newShard(shardRouting, indexMetaData, searcherWrapper, new InternalEngineFactory(), globalCheckpointSyncer);
     }
 
 
@@ -241,7 +242,7 @@ public abstract class IndexShardTestCase extends ESTestCase {
      */
     protected IndexShard newShard(ShardRouting routing, IndexMetaData indexMetaData, IndexingOperationListener... listeners)
         throws IOException {
-        return newShard(routing, indexMetaData, null, null, () -> {}, listeners);
+        return newShard(routing, indexMetaData, null, new InternalEngineFactory(), () -> {}, listeners);
     }
 
     /**

x-pack/plugin/watcher/src/test/java/org/elasticsearch/xpack/watcher/WatcherPluginTests.java

@@ -10,6 +10,7 @@ import org.elasticsearch.env.TestEnvironment;
 import org.elasticsearch.index.IndexModule;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.analysis.AnalysisRegistry;
+import org.elasticsearch.index.engine.InternalEngineFactory;
 import org.elasticsearch.test.ESTestCase;
 import org.elasticsearch.test.IndexSettingsModule;
 import org.elasticsearch.threadpool.ExecutorBuilder;
@@ -68,7 +69,7 @@ public class WatcherPluginTests extends ESTestCase {
         IndexSettings indexSettings = IndexSettingsModule.newIndexSettings(Watch.INDEX, settings);
         AnalysisRegistry registry = new AnalysisRegistry(TestEnvironment.newEnvironment(settings), emptyMap(), emptyMap(), emptyMap(),
                 emptyMap(), emptyMap(), emptyMap(), emptyMap(), emptyMap(), emptyMap());
-        IndexModule indexModule = new IndexModule(indexSettings, registry);
+        IndexModule indexModule = new IndexModule(indexSettings, registry, new InternalEngineFactory());
         // this will trip an assertion if the watcher indexing operation listener is null (which it is) but we try to add it
         watcher.onIndexModule(indexModule);