opendaylight/md-sal/sal-distributed-datastore/src/test/java/org/opendaylight/controller/cluster/datastore/AbstractShardTest.java

   1 /*
   2  * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.cluster.datastore;
   9
  10 import static org.junit.Assert.assertEquals;
  11 import static org.junit.Assert.assertNotNull;
  12 import static org.junit.Assert.assertTrue;
  13 import static org.junit.Assert.fail;
  14 import static org.mockito.Matchers.any;
  15 import static org.mockito.Mockito.doAnswer;
  16 import static org.mockito.Mockito.doNothing;
  17 import static org.mockito.Mockito.doReturn;
  18 import static org.mockito.Mockito.mock;
  19 import static org.opendaylight.controller.cluster.datastore.DataStoreVersions.CURRENT_VERSION;
  20 import akka.actor.ActorRef;
  21 import akka.actor.PoisonPill;
  22 import akka.actor.Props;
  23 import akka.dispatch.Dispatchers;
  24 import akka.japi.Creator;
  25 import akka.pattern.Patterns;
  26 import akka.testkit.TestActorRef;
  27 import akka.util.Timeout;
  28 import com.google.common.base.Function;
  29 import com.google.common.base.Optional;
  30 import com.google.common.util.concurrent.Futures;
  31 import com.google.common.util.concurrent.ListenableFuture;
  32 import com.google.common.util.concurrent.Uninterruptibles;
  33 import java.util.Collections;
  34 import java.util.Set;
  35 import java.util.concurrent.CountDownLatch;
  36 import java.util.concurrent.ExecutionException;
  37 import java.util.concurrent.TimeUnit;
  38 import java.util.concurrent.TimeoutException;
  39 import java.util.concurrent.atomic.AtomicInteger;
  40 import org.junit.After;
  41 import org.junit.Assert;
  42 import org.junit.Before;
  43 import org.mockito.invocation.InvocationOnMock;
  44 import org.mockito.stubbing.Answer;
  45 import org.opendaylight.controller.cluster.datastore.DatastoreContext.Builder;
  46 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  47 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  48 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  49 import org.opendaylight.controller.cluster.datastore.modification.MutableCompositeModification;
  50 import org.opendaylight.controller.cluster.datastore.modification.WriteModification;
  51 import org.opendaylight.controller.cluster.datastore.utils.SerializationUtils;
  52 import org.opendaylight.controller.cluster.raft.ReplicatedLogEntry;
  53 import org.opendaylight.controller.cluster.raft.Snapshot;
  54 import org.opendaylight.controller.cluster.raft.TestActorFactory;
  55 import org.opendaylight.controller.cluster.raft.utils.InMemoryJournal;
  56 import org.opendaylight.controller.cluster.raft.utils.InMemorySnapshotStore;
  57 import org.opendaylight.controller.md.cluster.datastore.model.CarsModel;
  58 import org.opendaylight.controller.md.cluster.datastore.model.TestModel;
  59 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  60 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
  61 import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
  62 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  63 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  64 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
  65 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
  66 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateNode;
  67 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateTip;
  68 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
  69 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
  70 import org.opendaylight.yangtools.yang.data.api.schema.tree.ModificationType;
  71 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
  72 import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
  73 import org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTreeFactory;
  74 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  75 import scala.concurrent.Await;
  76 import scala.concurrent.Future;
  77 import scala.concurrent.duration.Duration;
  78
  79 /**
  80  * Abstract base for shard unit tests.
  81  *
  82  * @author Thomas Pantelis
  83  */
  84 public abstract class AbstractShardTest extends AbstractActorTest{
  85     protected static final SchemaContext SCHEMA_CONTEXT = TestModel.createTestContext();
  86
  87     private static final AtomicInteger NEXT_SHARD_NUM = new AtomicInteger();
  88
  89     protected final ShardIdentifier shardID = ShardIdentifier.builder().memberName("member-1")
  90             .shardName("inventory").type("config" + NEXT_SHARD_NUM.getAndIncrement()).build();
  91
  92     protected final Builder dataStoreContextBuilder = DatastoreContext.newBuilder().
  93             shardJournalRecoveryLogBatchSize(3).shardSnapshotBatchCount(5000).
  94             shardHeartbeatIntervalInMillis(100);
  95
  96     protected final TestActorFactory actorFactory = new TestActorFactory(getSystem());
  97
  98     @Before
  99     public void setUp() {
 100         InMemorySnapshotStore.clear();
 101         InMemoryJournal.clear();
 102     }
 103
 104     @After
 105     public void tearDown() {
 106         InMemorySnapshotStore.clear();
 107         InMemoryJournal.clear();
 108         actorFactory.close();
 109     }
 110
 111     protected DatastoreContext newDatastoreContext() {
 112         return dataStoreContextBuilder.build();
 113     }
 114
 115     protected Props newShardProps() {
 116         return newShardBuilder().props();
 117     }
 118
 119     protected Shard.Builder newShardBuilder() {
 120         return Shard.builder().id(shardID).datastoreContext(newDatastoreContext()).schemaContext(SCHEMA_CONTEXT);
 121     }
 122
 123     protected void testRecovery(final Set<Integer> listEntryKeys) throws Exception {
 124         // Create the actor and wait for recovery complete.
 125
 126         final int nListEntries = listEntryKeys.size();
 127
 128         final CountDownLatch recoveryComplete = new CountDownLatch(1);
 129
 130         @SuppressWarnings("serial")
 131         final
 132         Creator<Shard> creator = new Creator<Shard>() {
 133             @Override
 134             public Shard create() throws Exception {
 135                 return new Shard(newShardBuilder()) {
 136                     @Override
 137                     protected void onRecoveryComplete() {
 138                         try {
 139                             super.onRecoveryComplete();
 140                         } finally {
 141                             recoveryComplete.countDown();
 142                         }
 143                     }
 144                 };
 145             }
 146         };
 147
 148         final TestActorRef<Shard> shard = TestActorRef.create(getSystem(),
 149                 Props.create(new DelegatingShardCreator(creator)).withDispatcher(Dispatchers.DefaultDispatcherId()), "testRecovery");
 150
 151         assertEquals("Recovery complete", true, recoveryComplete.await(5, TimeUnit.SECONDS));
 152
 153         // Verify data in the data store.
 154
 155         final NormalizedNode<?, ?> outerList = readStore(shard, TestModel.OUTER_LIST_PATH);
 156         assertNotNull(TestModel.OUTER_LIST_QNAME.getLocalName() + " not found", outerList);
 157         assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " value is not Iterable",
 158                 outerList.getValue() instanceof Iterable);
 159         for(final Object entry: (Iterable<?>) outerList.getValue()) {
 160             assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " entry is not MapEntryNode",
 161                     entry instanceof MapEntryNode);
 162             final MapEntryNode mapEntry = (MapEntryNode)entry;
 163             final Optional<DataContainerChild<? extends PathArgument, ?>> idLeaf =
 164                     mapEntry.getChild(new YangInstanceIdentifier.NodeIdentifier(TestModel.ID_QNAME));
 165             assertTrue("Missing leaf " + TestModel.ID_QNAME.getLocalName(), idLeaf.isPresent());
 166             final Object value = idLeaf.get().getValue();
 167             assertTrue("Unexpected value for leaf "+ TestModel.ID_QNAME.getLocalName() + ": " + value,
 168                     listEntryKeys.remove(value));
 169         }
 170
 171         if(!listEntryKeys.isEmpty()) {
 172             fail("Missing " + TestModel.OUTER_LIST_QNAME.getLocalName() + " entries with keys: " +
 173                     listEntryKeys);
 174         }
 175
 176         assertEquals("Last log index", nListEntries,
 177                 shard.underlyingActor().getShardMBean().getLastLogIndex());
 178         assertEquals("Commit index", nListEntries,
 179                 shard.underlyingActor().getShardMBean().getCommitIndex());
 180         assertEquals("Last applied", nListEntries,
 181                 shard.underlyingActor().getShardMBean().getLastApplied());
 182
 183         shard.tell(PoisonPill.getInstance(), ActorRef.noSender());
 184     }
 185
 186     protected void verifyLastApplied(final TestActorRef<Shard> shard, final long expectedValue) {
 187         long lastApplied = -1;
 188         for(int i = 0; i < 20 * 5; i++) {
 189             lastApplied = shard.underlyingActor().getShardMBean().getLastApplied();
 190             if(lastApplied == expectedValue) {
 191                 return;
 192             }
 193             Uninterruptibles.sleepUninterruptibly(50, TimeUnit.MILLISECONDS);
 194         }
 195
 196         Assert.fail(String.format("Expected last applied: %d, Actual: %d", expectedValue, lastApplied));
 197     }
 198
 199     protected ShardDataTreeCohort setupMockWriteTransaction(final String cohortName,
 200             final ShardDataTree dataStore, final YangInstanceIdentifier path, final NormalizedNode<?, ?> data,
 201             final MutableCompositeModification modification) {
 202         return setupMockWriteTransaction(cohortName, dataStore, path, data, modification, null);
 203     }
 204
 205     protected ShardDataTreeCohort setupMockWriteTransaction(final String cohortName,
 206             final ShardDataTree dataStore, final YangInstanceIdentifier path, final NormalizedNode<?, ?> data,
 207             final MutableCompositeModification modification,
 208             final Function<ShardDataTreeCohort, ListenableFuture<Void>> preCommit) {
 209
 210         final ReadWriteShardDataTreeTransaction tx = dataStore.newReadWriteTransaction("setup-mock-" + cohortName, null);
 211         tx.getSnapshot().write(path, data);
 212         final ShardDataTreeCohort cohort = createDelegatingMockCohort(cohortName, dataStore.finishTransaction(tx), preCommit);
 213
 214         modification.addModification(new WriteModification(path, data));
 215
 216         return cohort;
 217     }
 218
 219     protected ShardDataTreeCohort createDelegatingMockCohort(final String cohortName,
 220             final ShardDataTreeCohort actual) {
 221         return createDelegatingMockCohort(cohortName, actual, null);
 222     }
 223
 224     protected ShardDataTreeCohort createDelegatingMockCohort(final String cohortName,
 225             final ShardDataTreeCohort actual,
 226             final Function<ShardDataTreeCohort, ListenableFuture<Void>> preCommit) {
 227         final ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class, cohortName);
 228
 229         doAnswer(new Answer<ListenableFuture<Boolean>>() {
 230             @Override
 231             public ListenableFuture<Boolean> answer(final InvocationOnMock invocation) {
 232                 return actual.canCommit();
 233             }
 234         }).when(cohort).canCommit();
 235
 236         doAnswer(new Answer<ListenableFuture<Void>>() {
 237             @Override
 238             public ListenableFuture<Void> answer(final InvocationOnMock invocation) throws Throwable {
 239                 if(preCommit != null) {
 240                     return preCommit.apply(actual);
 241                 } else {
 242                     return actual.preCommit();
 243                 }
 244             }
 245         }).when(cohort).preCommit();
 246
 247         doAnswer(new Answer<ListenableFuture<Void>>() {
 248             @Override
 249             public ListenableFuture<Void> answer(final InvocationOnMock invocation) throws Throwable {
 250                 return actual.commit();
 251             }
 252         }).when(cohort).commit();
 253
 254         doAnswer(new Answer<ListenableFuture<Void>>() {
 255             @Override
 256             public ListenableFuture<Void> answer(final InvocationOnMock invocation) throws Throwable {
 257                 return actual.abort();
 258             }
 259         }).when(cohort).abort();
 260
 261         doAnswer(new Answer<DataTreeCandidateTip>() {
 262             @Override
 263             public DataTreeCandidateTip answer(final InvocationOnMock invocation) {
 264                 return actual.getCandidate();
 265             }
 266         }).when(cohort).getCandidate();
 267
 268         return cohort;
 269     }
 270
 271     protected Object prepareReadyTransactionMessage(boolean remoteReadWriteTransaction, Shard shard, ShardDataTreeCohort cohort,
 272                                                                   String transactionID,
 273                                                                   MutableCompositeModification modification,
 274                                                                   boolean doCommitOnReady) {
 275         if(remoteReadWriteTransaction){
 276             return prepareForwardedReadyTransaction(cohort, transactionID, CURRENT_VERSION,
 277                     doCommitOnReady);
 278         } else {
 279             setupCohortDecorator(shard, cohort);
 280             return prepareBatchedModifications(transactionID, modification, doCommitOnReady);
 281         }
 282     }
 283
 284     protected ShardDataTreeCohort mockShardDataTreeCohort() {
 285         ShardDataTreeCohort cohort = mock(ShardDataTreeCohort.class);
 286         doReturn(Futures.immediateFuture(Boolean.TRUE)).when(cohort).canCommit();
 287         doReturn(Futures.immediateFuture(null)).when(cohort).preCommit();
 288         doReturn(Futures.immediateFuture(null)).when(cohort).commit();
 289         doReturn(mockCandidate("candidate")).when(cohort).getCandidate();
 290         return cohort;
 291     }
 292
 293     static ShardDataTreeTransactionParent newShardDataTreeTransactionParent(ShardDataTreeCohort cohort) {
 294         ShardDataTreeTransactionParent mockParent = mock(ShardDataTreeTransactionParent.class);
 295         doReturn(cohort).when(mockParent).finishTransaction(any(ReadWriteShardDataTreeTransaction.class));
 296         doNothing().when(mockParent).abortTransaction(any(AbstractShardDataTreeTransaction.class));
 297         return mockParent;
 298     }
 299
 300     protected ForwardedReadyTransaction prepareForwardedReadyTransaction(ShardDataTreeCohort cohort,
 301             String transactionID, short version, boolean doCommitOnReady) {
 302         return new ForwardedReadyTransaction(transactionID, version,
 303                 new ReadWriteShardDataTreeTransaction(newShardDataTreeTransactionParent(cohort), transactionID,
 304                         mock(DataTreeModification.class)), true, doCommitOnReady);
 305     }
 306
 307     protected Object prepareReadyTransactionMessage(boolean remoteReadWriteTransaction, Shard shard, ShardDataTreeCohort cohort,
 308                                                                   String transactionID,
 309                                                                   MutableCompositeModification modification) {
 310         return prepareReadyTransactionMessage(remoteReadWriteTransaction, shard, cohort, transactionID, modification, false);
 311     }
 312
 313     protected void setupCohortDecorator(Shard shard, final ShardDataTreeCohort cohort) {
 314         shard.getCommitCoordinator().setCohortDecorator(new ShardCommitCoordinator.CohortDecorator() {
 315             @Override
 316             public ShardDataTreeCohort decorate(String transactionID, ShardDataTreeCohort actual) {
 317                 return cohort;
 318             }
 319         });
 320     }
 321
 322     protected BatchedModifications prepareBatchedModifications(String transactionID,
 323                                                                MutableCompositeModification modification) {
 324         return prepareBatchedModifications(transactionID, modification, false);
 325     }
 326
 327     private static BatchedModifications prepareBatchedModifications(String transactionID,
 328                                                              MutableCompositeModification modification,
 329                                                              boolean doCommitOnReady) {
 330         final BatchedModifications batchedModifications = new BatchedModifications(transactionID, CURRENT_VERSION, null);
 331         batchedModifications.addModification(modification);
 332         batchedModifications.setReady(true);
 333         batchedModifications.setDoCommitOnReady(doCommitOnReady);
 334         batchedModifications.setTotalMessagesSent(1);
 335         return batchedModifications;
 336     }
 337
 338
 339     public static NormalizedNode<?,?> readStore(final TestActorRef<? extends Shard> shard, final YangInstanceIdentifier id)
 340             throws ExecutionException, InterruptedException {
 341         return shard.underlyingActor().getDataStore().readNode(id).orNull();
 342     }
 343
 344     public static NormalizedNode<?,?> readStore(final DataTree store, final YangInstanceIdentifier id) {
 345         return store.takeSnapshot().readNode(id).orNull();
 346     }
 347
 348     public static void writeToStore(final TestActorRef<Shard> shard, final YangInstanceIdentifier id,
 349             final NormalizedNode<?,?> node) throws InterruptedException, ExecutionException {
 350         Future<Object> future = Patterns.ask(shard, newBatchedModifications("tx", id, node, true, true, 1),
 351                 new Timeout(5, TimeUnit.SECONDS));
 352         try {
 353             Await.ready(future, Duration.create(5, TimeUnit.SECONDS));
 354         } catch(TimeoutException e) {
 355             throw new ExecutionException(e);
 356         }
 357     }
 358
 359     public static void writeToStore(final ShardDataTree store, final YangInstanceIdentifier id,
 360             final NormalizedNode<?,?> node) throws InterruptedException, ExecutionException {
 361         final ReadWriteShardDataTreeTransaction transaction = store.newReadWriteTransaction("writeToStore", null);
 362
 363         transaction.getSnapshot().write(id, node);
 364         final ShardDataTreeCohort cohort = transaction.ready();
 365         cohort.canCommit().get();
 366         cohort.preCommit().get();
 367         cohort.commit();
 368     }
 369
 370     public static void mergeToStore(final ShardDataTree store, final YangInstanceIdentifier id,
 371             final NormalizedNode<?,?> node) throws InterruptedException, ExecutionException {
 372         final ReadWriteShardDataTreeTransaction transaction = store.newReadWriteTransaction("writeToStore", null);
 373
 374         transaction.getSnapshot().merge(id, node);
 375         final ShardDataTreeCohort cohort = transaction.ready();
 376         cohort.canCommit().get();
 377         cohort.preCommit().get();
 378         cohort.commit();
 379     }
 380
 381     public static void writeToStore(final DataTree store, final YangInstanceIdentifier id,
 382             final NormalizedNode<?,?> node) throws DataValidationFailedException {
 383         final DataTreeModification transaction = store.takeSnapshot().newModification();
 384
 385         transaction.write(id, node);
 386         transaction.ready();
 387         store.validate(transaction);
 388         final DataTreeCandidate candidate = store.prepare(transaction);
 389         store.commit(candidate);
 390     }
 391
 392     DataTree setupInMemorySnapshotStore() throws DataValidationFailedException {
 393         final DataTree testStore = InMemoryDataTreeFactory.getInstance().create(TreeType.OPERATIONAL);
 394         testStore.setSchemaContext(SCHEMA_CONTEXT);
 395
 396         writeToStore(testStore, TestModel.TEST_PATH, ImmutableNodes.containerNode(TestModel.TEST_QNAME));
 397
 398         final NormalizedNode<?, ?> root = readStore(testStore, YangInstanceIdentifier.builder().build());
 399
 400         InMemorySnapshotStore.addSnapshot(shardID.toString(), Snapshot.create(
 401                 SerializationUtils.serializeNormalizedNode(root),
 402                 Collections.<ReplicatedLogEntry>emptyList(), 0, 1, -1, -1));
 403         return testStore;
 404     }
 405
 406     static DataTreeCandidatePayload payloadForModification(final DataTree source, final DataTreeModification mod) throws DataValidationFailedException {
 407         source.validate(mod);
 408         final DataTreeCandidate candidate = source.prepare(mod);
 409         source.commit(candidate);
 410         return DataTreeCandidatePayload.create(candidate);
 411     }
 412
 413     static BatchedModifications newBatchedModifications(final String transactionID, final YangInstanceIdentifier path,
 414             final NormalizedNode<?, ?> data, final boolean ready, final boolean doCommitOnReady, final int messagesSent) {
 415         return newBatchedModifications(transactionID, null, path, data, ready, doCommitOnReady, messagesSent);
 416     }
 417
 418     static BatchedModifications newBatchedModifications(final String transactionID, final String transactionChainID,
 419             final YangInstanceIdentifier path, final NormalizedNode<?, ?> data, final boolean ready, final boolean doCommitOnReady,
 420             final int messagesSent) {
 421         final BatchedModifications batched = new BatchedModifications(transactionID, CURRENT_VERSION, transactionChainID);
 422         batched.addModification(new WriteModification(path, data));
 423         batched.setReady(ready);
 424         batched.setDoCommitOnReady(doCommitOnReady);
 425         batched.setTotalMessagesSent(messagesSent);
 426         return batched;
 427     }
 428
 429     @SuppressWarnings("unchecked")
 430     static void verifyOuterListEntry(final TestActorRef<Shard> shard, final Object expIDValue) throws Exception {
 431         final NormalizedNode<?, ?> outerList = readStore(shard, TestModel.OUTER_LIST_PATH);
 432         assertNotNull(TestModel.OUTER_LIST_QNAME.getLocalName() + " not found", outerList);
 433         assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " value is not Iterable",
 434                 outerList.getValue() instanceof Iterable);
 435         final Object entry = ((Iterable<Object>)outerList.getValue()).iterator().next();
 436         assertTrue(TestModel.OUTER_LIST_QNAME.getLocalName() + " entry is not MapEntryNode",
 437                 entry instanceof MapEntryNode);
 438         final MapEntryNode mapEntry = (MapEntryNode)entry;
 439         final Optional<DataContainerChild<? extends PathArgument, ?>> idLeaf =
 440                 mapEntry.getChild(new YangInstanceIdentifier.NodeIdentifier(TestModel.ID_QNAME));
 441         assertTrue("Missing leaf " + TestModel.ID_QNAME.getLocalName(), idLeaf.isPresent());
 442         assertEquals(TestModel.ID_QNAME.getLocalName() + " value", expIDValue, idLeaf.get().getValue());
 443     }
 444
 445     public static DataTreeCandidateTip mockCandidate(final String name) {
 446         final DataTreeCandidateTip mockCandidate = mock(DataTreeCandidateTip.class, name);
 447         final DataTreeCandidateNode mockCandidateNode = mock(DataTreeCandidateNode.class, name + "-node");
 448         doReturn(ModificationType.WRITE).when(mockCandidateNode).getModificationType();
 449         doReturn(Optional.of(ImmutableNodes.containerNode(CarsModel.CARS_QNAME))).when(mockCandidateNode).getDataAfter();
 450         doReturn(YangInstanceIdentifier.builder().build()).when(mockCandidate).getRootPath();
 451         doReturn(mockCandidateNode).when(mockCandidate).getRootNode();
 452         return mockCandidate;
 453     }
 454
 455     static DataTreeCandidateTip mockUnmodifiedCandidate(final String name) {
 456         final DataTreeCandidateTip mockCandidate = mock(DataTreeCandidateTip.class, name);
 457         final DataTreeCandidateNode mockCandidateNode = mock(DataTreeCandidateNode.class, name + "-node");
 458         doReturn(ModificationType.UNMODIFIED).when(mockCandidateNode).getModificationType();
 459         doReturn(YangInstanceIdentifier.builder().build()).when(mockCandidate).getRootPath();
 460         doReturn(mockCandidateNode).when(mockCandidate).getRootNode();
 461         return mockCandidate;
 462     }
 463
 464     static void commitTransaction(final DataTree store, final DataTreeModification modification) throws DataValidationFailedException {
 465         modification.ready();
 466         store.validate(modification);
 467         store.commit(store.prepare(modification));
 468     }
 469
 470     @SuppressWarnings("serial")
 471     public static final class DelegatingShardCreator implements Creator<Shard> {
 472         private final Creator<Shard> delegate;
 473
 474         DelegatingShardCreator(final Creator<Shard> delegate) {
 475             this.delegate = delegate;
 476         }
 477
 478         @Override
 479         public Shard create() throws Exception {
 480             return delegate.create();
 481         }
 482     }
 483 }