opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/Shard.java

   1 /*
   2  * Copyright (c) 2014 Cisco 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
   9 package org.opendaylight.controller.cluster.datastore;
  10
  11 import akka.actor.ActorRef;
  12 import akka.actor.ActorSelection;
  13 import akka.actor.Cancellable;
  14 import akka.actor.ExtendedActorSystem;
  15 import akka.actor.Props;
  16 import akka.actor.Status;
  17 import akka.actor.Status.Failure;
  18 import akka.serialization.JavaSerializer;
  19 import akka.serialization.Serialization;
  20 import com.google.common.annotations.VisibleForTesting;
  21 import com.google.common.base.Optional;
  22 import com.google.common.base.Preconditions;
  23 import com.google.common.base.Ticker;
  24 import com.google.common.base.Verify;
  25 import com.google.common.collect.ImmutableList;
  26 import com.google.common.collect.ImmutableMap;
  27 import com.google.common.collect.Range;
  28 import java.io.IOException;
  29 import java.util.Arrays;
  30 import java.util.Collection;
  31 import java.util.Collections;
  32 import java.util.Map;
  33 import java.util.concurrent.TimeUnit;
  34 import javax.annotation.Nonnull;
  35 import javax.annotation.Nullable;
  36 import org.opendaylight.controller.cluster.access.ABIVersion;
  37 import org.opendaylight.controller.cluster.access.commands.ConnectClientRequest;
  38 import org.opendaylight.controller.cluster.access.commands.ConnectClientSuccess;
  39 import org.opendaylight.controller.cluster.access.commands.LocalHistoryRequest;
  40 import org.opendaylight.controller.cluster.access.commands.NotLeaderException;
  41 import org.opendaylight.controller.cluster.access.commands.OutOfSequenceEnvelopeException;
  42 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  43 import org.opendaylight.controller.cluster.access.concepts.ClientIdentifier;
  44 import org.opendaylight.controller.cluster.access.concepts.FrontendIdentifier;
  45 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  46 import org.opendaylight.controller.cluster.access.concepts.Request;
  47 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  48 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  49 import org.opendaylight.controller.cluster.access.concepts.RequestSuccess;
  50 import org.opendaylight.controller.cluster.access.concepts.RetiredGenerationException;
  51 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  52 import org.opendaylight.controller.cluster.access.concepts.SliceableMessage;
  53 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  54 import org.opendaylight.controller.cluster.access.concepts.UnsupportedRequestException;
  55 import org.opendaylight.controller.cluster.common.actor.CommonConfig;
  56 import org.opendaylight.controller.cluster.common.actor.Dispatchers;
  57 import org.opendaylight.controller.cluster.common.actor.Dispatchers.DispatcherType;
  58 import org.opendaylight.controller.cluster.common.actor.MessageTracker;
  59 import org.opendaylight.controller.cluster.common.actor.MessageTracker.Error;
  60 import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
  61 import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
  62 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  63 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
  64 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
  65 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
  66 import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
  67 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  68 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  69 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  70 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  71 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  72 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  73 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  74 import org.opendaylight.controller.cluster.datastore.messages.GetShardDataTree;
  75 import org.opendaylight.controller.cluster.datastore.messages.MakeLeaderLocal;
  76 import org.opendaylight.controller.cluster.datastore.messages.OnDemandShardState;
  77 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
  78 import org.opendaylight.controller.cluster.datastore.messages.PersistAbortTransactionPayload;
  79 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  80 import org.opendaylight.controller.cluster.datastore.messages.RegisterChangeListener;
  81 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  82 import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
  83 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
  84 import org.opendaylight.controller.cluster.datastore.persisted.AbortTransactionPayload;
  85 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot;
  86 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot.ShardSnapshot;
  87 import org.opendaylight.controller.cluster.messaging.MessageAssembler;
  88 import org.opendaylight.controller.cluster.messaging.MessageSlicer;
  89 import org.opendaylight.controller.cluster.messaging.SliceOptions;
  90 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  91 import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
  92 import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
  93 import org.opendaylight.controller.cluster.raft.LeadershipTransferFailedException;
  94 import org.opendaylight.controller.cluster.raft.RaftActor;
  95 import org.opendaylight.controller.cluster.raft.RaftActorRecoveryCohort;
  96 import org.opendaylight.controller.cluster.raft.RaftActorSnapshotCohort;
  97 import org.opendaylight.controller.cluster.raft.RaftState;
  98 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
  99 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
 100 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
 101 import org.opendaylight.controller.cluster.raft.messages.RequestLeadership;
 102 import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
 103 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 104 import org.opendaylight.yangtools.concepts.Identifier;
 105 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
 106 import org.opendaylight.yangtools.yang.data.api.schema.tree.TipProducingDataTree;
 107 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 108 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 109 import org.opendaylight.yangtools.yang.model.api.SchemaContextProvider;
 110 import scala.concurrent.duration.Duration;
 111 import scala.concurrent.duration.FiniteDuration;
 112
 113 /**
 114  * A Shard represents a portion of the logical data tree.
 115  *
 116  * <p>
 117  * Our Shard uses InMemoryDataTree as it's internal representation and delegates all requests it
 118  */
 119 public class Shard extends RaftActor {
 120
 121     @VisibleForTesting
 122     static final Object TX_COMMIT_TIMEOUT_CHECK_MESSAGE = new Object() {
 123         @Override
 124         public String toString() {
 125             return "txCommitTimeoutCheck";
 126         }
 127     };
 128
 129     @VisibleForTesting
 130     static final Object GET_SHARD_MBEAN_MESSAGE = new Object() {
 131         @Override
 132         public String toString() {
 133             return "getShardMBeanMessage";
 134         }
 135     };
 136
 137     static final Object RESUME_NEXT_PENDING_TRANSACTION = new Object() {
 138         @Override
 139         public String toString() {
 140             return "resumeNextPendingTransaction";
 141         }
 142     };
 143
 144     // FIXME: shard names should be encapsulated in their own class and this should be exposed as a constant.
 145     public static final String DEFAULT_NAME = "default";
 146
 147     private static final Collection<ABIVersion> SUPPORTED_ABIVERSIONS;
 148
 149     static {
 150         final ABIVersion[] values = ABIVersion.values();
 151         final ABIVersion[] real = Arrays.copyOfRange(values, 1, values.length - 1);
 152         SUPPORTED_ABIVERSIONS = ImmutableList.copyOf(real).reverse();
 153     }
 154
 155     // FIXME: make this a dynamic property based on mailbox size and maximum number of clients
 156     private static final int CLIENT_MAX_MESSAGES = 1000;
 157
 158     // The state of this Shard
 159     private final ShardDataTree store;
 160
 161     /// The name of this shard
 162     private final String name;
 163
 164     private final ShardStats shardMBean;
 165
 166     private DatastoreContext datastoreContext;
 167
 168     private final ShardCommitCoordinator commitCoordinator;
 169
 170     private long transactionCommitTimeout;
 171
 172     private Cancellable txCommitTimeoutCheckSchedule;
 173
 174     private final Optional<ActorRef> roleChangeNotifier;
 175
 176     private final MessageTracker appendEntriesReplyTracker;
 177
 178     private final ShardTransactionActorFactory transactionActorFactory;
 179
 180     private final ShardSnapshotCohort snapshotCohort;
 181
 182     private final DataTreeChangeListenerSupport treeChangeSupport = new DataTreeChangeListenerSupport(this);
 183     private final DataChangeListenerSupport changeSupport = new DataChangeListenerSupport(this);
 184
 185
 186     private ShardSnapshot restoreFromSnapshot;
 187
 188     private final ShardTransactionMessageRetrySupport messageRetrySupport;
 189
 190     private final FrontendMetadata frontendMetadata;
 191     private Map<FrontendIdentifier, LeaderFrontendState> knownFrontends = ImmutableMap.of();
 192     private boolean paused;
 193
 194     private final MessageSlicer responseMessageSlicer;
 195     private final Dispatchers dispatchers;
 196
 197     private final MessageAssembler requestMessageAssembler;
 198
 199     protected Shard(final AbstractBuilder<?, ?> builder) {
 200         super(builder.getId().toString(), builder.getPeerAddresses(),
 201                 Optional.of(builder.getDatastoreContext().getShardRaftConfig()), DataStoreVersions.CURRENT_VERSION);
 202
 203         this.name = builder.getId().toString();
 204         this.datastoreContext = builder.getDatastoreContext();
 205         this.restoreFromSnapshot = builder.getRestoreFromSnapshot();
 206         this.frontendMetadata = new FrontendMetadata(name);
 207
 208         setPersistence(datastoreContext.isPersistent());
 209
 210         LOG.info("Shard created : {}, persistent : {}", name, datastoreContext.isPersistent());
 211
 212         ShardDataTreeChangeListenerPublisherActorProxy treeChangeListenerPublisher =
 213                 new ShardDataTreeChangeListenerPublisherActorProxy(getContext(), name + "-DTCL-publisher", name);
 214         ShardDataChangeListenerPublisherActorProxy dataChangeListenerPublisher =
 215                 new ShardDataChangeListenerPublisherActorProxy(getContext(), name + "-DCL-publisher", name);
 216         if (builder.getDataTree() != null) {
 217             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getDataTree(),
 218                     treeChangeListenerPublisher, dataChangeListenerPublisher, name, frontendMetadata);
 219         } else {
 220             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getTreeType(),
 221                     builder.getDatastoreContext().getStoreRoot(), treeChangeListenerPublisher,
 222                     dataChangeListenerPublisher, name, frontendMetadata);
 223         }
 224
 225         shardMBean = ShardMBeanFactory.getShardStatsMBean(name, datastoreContext.getDataStoreMXBeanType(), this);
 226
 227         if (isMetricsCaptureEnabled()) {
 228             getContext().become(new MeteringBehavior(this));
 229         }
 230
 231         commitCoordinator = new ShardCommitCoordinator(store, LOG, this.name);
 232
 233         setTransactionCommitTimeout();
 234
 235         // create a notifier actor for each cluster member
 236         roleChangeNotifier = createRoleChangeNotifier(name);
 237
 238         appendEntriesReplyTracker = new MessageTracker(AppendEntriesReply.class,
 239                 getRaftActorContext().getConfigParams().getIsolatedCheckIntervalInMillis());
 240
 241         dispatchers = new Dispatchers(context().system().dispatchers());
 242         transactionActorFactory = new ShardTransactionActorFactory(store, datastoreContext,
 243             dispatchers.getDispatcherPath(Dispatchers.DispatcherType.Transaction),
 244                 self(), getContext(), shardMBean, builder.getId().getShardName());
 245
 246         snapshotCohort = ShardSnapshotCohort.create(getContext(), builder.getId().getMemberName(), store, LOG,
 247             this.name);
 248
 249         messageRetrySupport = new ShardTransactionMessageRetrySupport(this);
 250
 251         responseMessageSlicer = MessageSlicer.builder().logContext(this.name)
 252                 .messageSliceSize(datastoreContext.getMaximumMessageSliceSize())
 253                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 254                 .expireStateAfterInactivity(2, TimeUnit.MINUTES).build();
 255
 256         requestMessageAssembler = MessageAssembler.builder().logContext(this.name)
 257                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 258                 .assembledMessageCallback((message, sender) -> self().tell(message, sender))
 259                 .expireStateAfterInactivity(datastoreContext.getRequestTimeout(), TimeUnit.NANOSECONDS).build();
 260     }
 261
 262     private void setTransactionCommitTimeout() {
 263         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
 264                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS) / 2;
 265     }
 266
 267     private Optional<ActorRef> createRoleChangeNotifier(final String shardId) {
 268         ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
 269             RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
 270         return Optional.of(shardRoleChangeNotifier);
 271     }
 272
 273     @Override
 274     public void postStop() {
 275         LOG.info("Stopping Shard {}", persistenceId());
 276
 277         super.postStop();
 278
 279         messageRetrySupport.close();
 280
 281         if (txCommitTimeoutCheckSchedule != null) {
 282             txCommitTimeoutCheckSchedule.cancel();
 283         }
 284
 285         commitCoordinator.abortPendingTransactions("Transaction aborted due to shutdown.", this);
 286
 287         shardMBean.unregisterMBean();
 288     }
 289
 290     @Override
 291     protected void handleRecover(final Object message) {
 292         LOG.debug("{}: onReceiveRecover: Received message {} from {}", persistenceId(), message.getClass(),
 293             getSender());
 294
 295         super.handleRecover(message);
 296         if (LOG.isTraceEnabled()) {
 297             appendEntriesReplyTracker.begin();
 298         }
 299     }
 300
 301     @Override
 302     protected void handleNonRaftCommand(final Object message) {
 303         try (MessageTracker.Context context = appendEntriesReplyTracker.received(message)) {
 304             final Optional<Error> maybeError = context.error();
 305             if (maybeError.isPresent()) {
 306                 LOG.trace("{} : AppendEntriesReply failed to arrive at the expected interval {}", persistenceId(),
 307                     maybeError.get());
 308             }
 309
 310             store.resetTransactionBatch();
 311
 312             if (message instanceof RequestEnvelope) {
 313                 handleRequestEnvelope((RequestEnvelope)message);
 314             } else if (requestMessageAssembler.isHandledMessage(message)) {
 315                 handleRequestAssemblerMessage(message);
 316             } else if (message instanceof ConnectClientRequest) {
 317                 handleConnectClient((ConnectClientRequest)message);
 318             } else if (CreateTransaction.isSerializedType(message)) {
 319                 handleCreateTransaction(message);
 320             } else if (message instanceof BatchedModifications) {
 321                 handleBatchedModifications((BatchedModifications)message);
 322             } else if (message instanceof ForwardedReadyTransaction) {
 323                 handleForwardedReadyTransaction((ForwardedReadyTransaction) message);
 324             } else if (message instanceof ReadyLocalTransaction) {
 325                 handleReadyLocalTransaction((ReadyLocalTransaction)message);
 326             } else if (CanCommitTransaction.isSerializedType(message)) {
 327                 handleCanCommitTransaction(CanCommitTransaction.fromSerializable(message));
 328             } else if (CommitTransaction.isSerializedType(message)) {
 329                 handleCommitTransaction(CommitTransaction.fromSerializable(message));
 330             } else if (AbortTransaction.isSerializedType(message)) {
 331                 handleAbortTransaction(AbortTransaction.fromSerializable(message));
 332             } else if (CloseTransactionChain.isSerializedType(message)) {
 333                 closeTransactionChain(CloseTransactionChain.fromSerializable(message));
 334             } else if (message instanceof RegisterChangeListener) {
 335                 changeSupport.onMessage((RegisterChangeListener) message, isLeader(), hasLeader());
 336             } else if (message instanceof RegisterDataTreeChangeListener) {
 337                 treeChangeSupport.onMessage((RegisterDataTreeChangeListener) message, isLeader(), hasLeader());
 338             } else if (message instanceof UpdateSchemaContext) {
 339                 updateSchemaContext((UpdateSchemaContext) message);
 340             } else if (message instanceof PeerAddressResolved) {
 341                 PeerAddressResolved resolved = (PeerAddressResolved) message;
 342                 setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
 343             } else if (TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
 344                 commitTimeoutCheck();
 345             } else if (message instanceof DatastoreContext) {
 346                 onDatastoreContext((DatastoreContext)message);
 347             } else if (message instanceof RegisterRoleChangeListener) {
 348                 roleChangeNotifier.get().forward(message, context());
 349             } else if (message instanceof FollowerInitialSyncUpStatus) {
 350                 shardMBean.setFollowerInitialSyncStatus(((FollowerInitialSyncUpStatus) message).isInitialSyncDone());
 351                 context().parent().tell(message, self());
 352             } else if (GET_SHARD_MBEAN_MESSAGE.equals(message)) {
 353                 sender().tell(getShardMBean(), self());
 354             } else if (message instanceof GetShardDataTree) {
 355                 sender().tell(store.getDataTree(), self());
 356             } else if (message instanceof ServerRemoved) {
 357                 context().parent().forward(message, context());
 358             } else if (ShardTransactionMessageRetrySupport.TIMER_MESSAGE_CLASS.isInstance(message)) {
 359                 messageRetrySupport.onTimerMessage(message);
 360             } else if (message instanceof DataTreeCohortActorRegistry.CohortRegistryCommand) {
 361                 store.processCohortRegistryCommand(getSender(),
 362                         (DataTreeCohortActorRegistry.CohortRegistryCommand) message);
 363             } else if (message instanceof PersistAbortTransactionPayload) {
 364                 final TransactionIdentifier txId = ((PersistAbortTransactionPayload) message).getTransactionId();
 365                 persistPayload(txId, AbortTransactionPayload.create(txId), true);
 366             } else if (message instanceof MakeLeaderLocal) {
 367                 onMakeLeaderLocal();
 368             } else if (RESUME_NEXT_PENDING_TRANSACTION.equals(message)) {
 369                 store.resumeNextPendingTransaction();
 370             } else if (!responseMessageSlicer.handleMessage(message)) {
 371                 super.handleNonRaftCommand(message);
 372             }
 373         }
 374     }
 375
 376     private void handleRequestAssemblerMessage(Object message) {
 377         dispatchers.getDispatcher(DispatcherType.Serialization).execute(() -> {
 378             JavaSerializer.currentSystem().value_$eq((ExtendedActorSystem) context().system());
 379             requestMessageAssembler.handleMessage(message, self());
 380         });
 381     }
 382
 383     @SuppressWarnings("checkstyle:IllegalCatch")
 384     private void handleRequestEnvelope(final RequestEnvelope envelope) {
 385         final long now = ticker().read();
 386         try {
 387             final RequestSuccess<?, ?> success = handleRequest(envelope, now);
 388             if (success != null) {
 389                 final long executionTimeNanos = ticker().read() - now;
 390                 if (success instanceof SliceableMessage) {
 391                     dispatchers.getDispatcher(DispatcherType.Serialization).execute(() ->
 392                         responseMessageSlicer.slice(SliceOptions.builder().identifier(success.getTarget())
 393                             .message(envelope.newSuccessEnvelope(success, executionTimeNanos))
 394                             .sendTo(envelope.getMessage().getReplyTo()).replyTo(self())
 395                             .onFailureCallback(t -> {
 396                                 LOG.warn("Error slicing response {}", success, t);
 397                             }).build()));
 398                 } else {
 399                     envelope.sendSuccess(success, executionTimeNanos);
 400                 }
 401             }
 402         } catch (RequestException e) {
 403             LOG.debug("{}: request {} failed", persistenceId(), envelope, e);
 404             envelope.sendFailure(e, ticker().read() - now);
 405         } catch (Exception e) {
 406             LOG.debug("{}: request {} caused failure", persistenceId(), envelope, e);
 407             envelope.sendFailure(new RuntimeRequestException("Request failed to process", e),
 408                 ticker().read() - now);
 409         }
 410     }
 411
 412     private void commitTimeoutCheck() {
 413         store.checkForExpiredTransactions(transactionCommitTimeout, this::updateAccess);
 414         commitCoordinator.checkForExpiredTransactions(transactionCommitTimeout, this);
 415         requestMessageAssembler.checkExpiredAssembledMessageState();
 416     }
 417
 418     private Optional<Long> updateAccess(final SimpleShardDataTreeCohort cohort) {
 419         final FrontendIdentifier frontend = cohort.getIdentifier().getHistoryId().getClientId().getFrontendId();
 420         final LeaderFrontendState state = knownFrontends.get(frontend);
 421         if (state == null) {
 422             // Not tell-based protocol, do nothing
 423             return Optional.absent();
 424         }
 425
 426         if (isIsolatedLeader()) {
 427             // We are isolated and no new request can come through until we emerge from it. We are still updating
 428             // liveness of frontend when we see it attempting to communicate. Use the last access timer.
 429             return Optional.of(state.getLastSeenTicks());
 430         }
 431
 432         // If this frontend has freshly connected, give it some time to catch up before killing its transactions.
 433         return Optional.of(state.getLastConnectTicks());
 434     }
 435
 436     private void onMakeLeaderLocal() {
 437         LOG.debug("{}: onMakeLeaderLocal received", persistenceId());
 438         if (isLeader()) {
 439             getSender().tell(new Status.Success(null), getSelf());
 440             return;
 441         }
 442
 443         final ActorSelection leader = getLeader();
 444
 445         if (leader == null) {
 446             // Leader is not present. The cluster is most likely trying to
 447             // elect a leader and we should let that run its normal course
 448
 449             // TODO we can wait for the election to complete and retry the
 450             // request. We can also let the caller retry by sending a flag
 451             // in the response indicating the request is "reTryable".
 452             getSender().tell(new Failure(
 453                     new LeadershipTransferFailedException("We cannot initiate leadership transfer to local node. "
 454                             + "Currently there is no leader for " + persistenceId())),
 455                     getSelf());
 456             return;
 457         }
 458
 459         leader.tell(new RequestLeadership(getId(), getSender()), getSelf());
 460     }
 461
 462     // Acquire our frontend tracking handle and verify generation matches
 463     @Nullable
 464     private LeaderFrontendState findFrontend(final ClientIdentifier clientId) throws RequestException {
 465         final LeaderFrontendState existing = knownFrontends.get(clientId.getFrontendId());
 466         if (existing != null) {
 467             final int cmp = Long.compareUnsigned(existing.getIdentifier().getGeneration(), clientId.getGeneration());
 468             if (cmp == 0) {
 469                 existing.touch();
 470                 return existing;
 471             }
 472             if (cmp > 0) {
 473                 LOG.debug("{}: rejecting request from outdated client {}", persistenceId(), clientId);
 474                 throw new RetiredGenerationException(existing.getIdentifier().getGeneration());
 475             }
 476
 477             LOG.info("{}: retiring state {}, outdated by request from client {}", persistenceId(), existing, clientId);
 478             existing.retire();
 479             knownFrontends.remove(clientId.getFrontendId());
 480         } else {
 481             LOG.debug("{}: client {} is not yet known", persistenceId(), clientId);
 482         }
 483
 484         return null;
 485     }
 486
 487     private LeaderFrontendState getFrontend(final ClientIdentifier clientId) throws RequestException {
 488         final LeaderFrontendState ret = findFrontend(clientId);
 489         if (ret != null) {
 490             return ret;
 491         }
 492
 493         // TODO: a dedicated exception would be better, but this is technically true, too
 494         throw new OutOfSequenceEnvelopeException(0);
 495     }
 496
 497     private static @Nonnull ABIVersion selectVersion(final ConnectClientRequest message) {
 498         final Range<ABIVersion> clientRange = Range.closed(message.getMinVersion(), message.getMaxVersion());
 499         for (ABIVersion v : SUPPORTED_ABIVERSIONS) {
 500             if (clientRange.contains(v)) {
 501                 return v;
 502             }
 503         }
 504
 505         throw new IllegalArgumentException(String.format(
 506             "No common version between backend versions %s and client versions %s", SUPPORTED_ABIVERSIONS,
 507             clientRange));
 508     }
 509
 510     @SuppressWarnings("checkstyle:IllegalCatch")
 511     private void handleConnectClient(final ConnectClientRequest message) {
 512         try {
 513             final ClientIdentifier clientId = message.getTarget();
 514             final LeaderFrontendState existing = findFrontend(clientId);
 515             if (existing != null) {
 516                 existing.touch();
 517             }
 518
 519             if (!isLeader() || !isLeaderActive()) {
 520                 LOG.info("{}: not currently leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 521                                 + "isLeadershipTransferInProgress: {}.",
 522                         persistenceId(), message, isLeader(), isLeaderActive(), isLeadershipTransferInProgress());
 523                 throw new NotLeaderException(getSelf());
 524             }
 525
 526             final ABIVersion selectedVersion = selectVersion(message);
 527             final LeaderFrontendState frontend;
 528             if (existing == null) {
 529                 frontend = new LeaderFrontendState(persistenceId(), clientId, store);
 530                 knownFrontends.put(clientId.getFrontendId(), frontend);
 531                 LOG.debug("{}: created state {} for client {}", persistenceId(), frontend, clientId);
 532             } else {
 533                 frontend = existing;
 534             }
 535
 536             frontend.reconnect();
 537             message.getReplyTo().tell(new ConnectClientSuccess(message.getTarget(), message.getSequence(), getSelf(),
 538                 ImmutableList.of(), store.getDataTree(), CLIENT_MAX_MESSAGES).toVersion(selectedVersion),
 539                 ActorRef.noSender());
 540         } catch (RequestException | RuntimeException e) {
 541             message.getReplyTo().tell(new Failure(e), ActorRef.noSender());
 542         }
 543     }
 544
 545     private @Nullable RequestSuccess<?, ?> handleRequest(final RequestEnvelope envelope, final long now)
 546             throws RequestException {
 547         // We are not the leader, hence we want to fail-fast.
 548         if (!isLeader() || paused || !isLeaderActive()) {
 549             LOG.debug("{}: not currently active leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 550                             + "isLeadershipTransferInProgress: {}, paused: {}",
 551                     persistenceId(), envelope, isLeader(), isLeaderActive(), isLeadershipTransferInProgress(), paused);
 552             throw new NotLeaderException(getSelf());
 553         }
 554
 555         final Request<?, ?> request = envelope.getMessage();
 556         if (request instanceof TransactionRequest) {
 557             final TransactionRequest<?> txReq = (TransactionRequest<?>)request;
 558             final ClientIdentifier clientId = txReq.getTarget().getHistoryId().getClientId();
 559             return getFrontend(clientId).handleTransactionRequest(txReq, envelope, now);
 560         } else if (request instanceof LocalHistoryRequest) {
 561             final LocalHistoryRequest<?> lhReq = (LocalHistoryRequest<?>)request;
 562             final ClientIdentifier clientId = lhReq.getTarget().getClientId();
 563             return getFrontend(clientId).handleLocalHistoryRequest(lhReq, envelope, now);
 564         } else {
 565             LOG.warn("{}: rejecting unsupported request {}", persistenceId(), request);
 566             throw new UnsupportedRequestException(request);
 567         }
 568     }
 569
 570     private boolean hasLeader() {
 571         return getLeaderId() != null;
 572     }
 573
 574     public int getPendingTxCommitQueueSize() {
 575         return store.getQueueSize();
 576     }
 577
 578     public int getCohortCacheSize() {
 579         return commitCoordinator.getCohortCacheSize();
 580     }
 581
 582     @Override
 583     protected Optional<ActorRef> getRoleChangeNotifier() {
 584         return roleChangeNotifier;
 585     }
 586
 587     @Override
 588     protected LeaderStateChanged newLeaderStateChanged(final String memberId, final String leaderId,
 589             final short leaderPayloadVersion) {
 590         return isLeader() ? new ShardLeaderStateChanged(memberId, leaderId, store.getDataTree(), leaderPayloadVersion)
 591                 : new ShardLeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 592     }
 593
 594     protected void onDatastoreContext(final DatastoreContext context) {
 595         datastoreContext = context;
 596
 597         setTransactionCommitTimeout();
 598
 599         setPersistence(datastoreContext.isPersistent());
 600
 601         updateConfigParams(datastoreContext.getShardRaftConfig());
 602     }
 603
 604     // applyState() will be invoked once consensus is reached on the payload
 605     void persistPayload(final Identifier id, final Payload payload, final boolean batchHint) {
 606         boolean canSkipPayload = !hasFollowers() && !persistence().isRecoveryApplicable();
 607         if (canSkipPayload) {
 608             applyState(self(), id, payload);
 609         } else {
 610             // We are faking the sender
 611             persistData(self(), id, payload, batchHint);
 612         }
 613     }
 614
 615     private void handleCommitTransaction(final CommitTransaction commit) {
 616         if (isLeader()) {
 617             commitCoordinator.handleCommit(commit.getTransactionId(), getSender(), this);
 618         } else {
 619             ActorSelection leader = getLeader();
 620             if (leader == null) {
 621                 messageRetrySupport.addMessageToRetry(commit, getSender(),
 622                         "Could not commit transaction " + commit.getTransactionId());
 623             } else {
 624                 LOG.debug("{}: Forwarding CommitTransaction to leader {}", persistenceId(), leader);
 625                 leader.forward(commit, getContext());
 626             }
 627         }
 628     }
 629
 630     private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
 631         LOG.debug("{}: Can committing transaction {}", persistenceId(), canCommit.getTransactionId());
 632
 633         if (isLeader()) {
 634             commitCoordinator.handleCanCommit(canCommit.getTransactionId(), getSender(), this);
 635         } else {
 636             ActorSelection leader = getLeader();
 637             if (leader == null) {
 638                 messageRetrySupport.addMessageToRetry(canCommit, getSender(),
 639                         "Could not canCommit transaction " + canCommit.getTransactionId());
 640             } else {
 641                 LOG.debug("{}: Forwarding CanCommitTransaction to leader {}", persistenceId(), leader);
 642                 leader.forward(canCommit, getContext());
 643             }
 644         }
 645     }
 646
 647     @SuppressWarnings("checkstyle:IllegalCatch")
 648     protected void handleBatchedModificationsLocal(final BatchedModifications batched, final ActorRef sender) {
 649         try {
 650             commitCoordinator.handleBatchedModifications(batched, sender, this);
 651         } catch (Exception e) {
 652             LOG.error("{}: Error handling BatchedModifications for Tx {}", persistenceId(),
 653                     batched.getTransactionId(), e);
 654             sender.tell(new Failure(e), getSelf());
 655         }
 656     }
 657
 658     private void handleBatchedModifications(final BatchedModifications batched) {
 659         // This message is sent to prepare the modifications transaction directly on the Shard as an
 660         // optimization to avoid the extra overhead of a separate ShardTransaction actor. On the last
 661         // BatchedModifications message, the caller sets the ready flag in the message indicating
 662         // modifications are complete. The reply contains the cohort actor path (this actor) for the caller
 663         // to initiate the 3-phase commit. This also avoids the overhead of sending an additional
 664         // ReadyTransaction message.
 665
 666         // If we're not the leader then forward to the leader. This is a safety measure - we shouldn't
 667         // normally get here if we're not the leader as the front-end (TransactionProxy) should determine
 668         // the primary/leader shard. However with timing and caching on the front-end, there's a small
 669         // window where it could have a stale leader during leadership transitions.
 670         //
 671         boolean isLeaderActive = isLeaderActive();
 672         if (isLeader() && isLeaderActive) {
 673             handleBatchedModificationsLocal(batched, getSender());
 674         } else {
 675             ActorSelection leader = getLeader();
 676             if (!isLeaderActive || leader == null) {
 677                 messageRetrySupport.addMessageToRetry(batched, getSender(),
 678                         "Could not commit transaction " + batched.getTransactionId());
 679             } else {
 680                 // If this is not the first batch and leadership changed in between batched messages,
 681                 // we need to reconstruct previous BatchedModifications from the transaction
 682                 // DataTreeModification, honoring the max batched modification count, and forward all the
 683                 // previous BatchedModifications to the new leader.
 684                 Collection<BatchedModifications> newModifications = commitCoordinator
 685                         .createForwardedBatchedModifications(batched,
 686                                 datastoreContext.getShardBatchedModificationCount());
 687
 688                 LOG.debug("{}: Forwarding {} BatchedModifications to leader {}", persistenceId(),
 689                         newModifications.size(), leader);
 690
 691                 for (BatchedModifications bm : newModifications) {
 692                     leader.forward(bm, getContext());
 693                 }
 694             }
 695         }
 696     }
 697
 698     private boolean failIfIsolatedLeader(final ActorRef sender) {
 699         if (isIsolatedLeader()) {
 700             sender.tell(new Failure(new NoShardLeaderException(String.format(
 701                     "Shard %s was the leader but has lost contact with all of its followers. Either all"
 702                     + " other follower nodes are down or this node is isolated by a network partition.",
 703                     persistenceId()))), getSelf());
 704             return true;
 705         }
 706
 707         return false;
 708     }
 709
 710     protected boolean isIsolatedLeader() {
 711         return getRaftState() == RaftState.IsolatedLeader;
 712     }
 713
 714     @SuppressWarnings("checkstyle:IllegalCatch")
 715     private void handleReadyLocalTransaction(final ReadyLocalTransaction message) {
 716         LOG.debug("{}: handleReadyLocalTransaction for {}", persistenceId(), message.getTransactionId());
 717
 718         boolean isLeaderActive = isLeaderActive();
 719         if (isLeader() && isLeaderActive) {
 720             try {
 721                 commitCoordinator.handleReadyLocalTransaction(message, getSender(), this);
 722             } catch (Exception e) {
 723                 LOG.error("{}: Error handling ReadyLocalTransaction for Tx {}", persistenceId(),
 724                         message.getTransactionId(), e);
 725                 getSender().tell(new Failure(e), getSelf());
 726             }
 727         } else {
 728             ActorSelection leader = getLeader();
 729             if (!isLeaderActive || leader == null) {
 730                 messageRetrySupport.addMessageToRetry(message, getSender(),
 731                         "Could not commit transaction " + message.getTransactionId());
 732             } else {
 733                 LOG.debug("{}: Forwarding ReadyLocalTransaction to leader {}", persistenceId(), leader);
 734                 message.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 735                 leader.forward(message, getContext());
 736             }
 737         }
 738     }
 739
 740     private void handleForwardedReadyTransaction(final ForwardedReadyTransaction forwardedReady) {
 741         LOG.debug("{}: handleForwardedReadyTransaction for {}", persistenceId(), forwardedReady.getTransactionId());
 742
 743         boolean isLeaderActive = isLeaderActive();
 744         if (isLeader() && isLeaderActive) {
 745             commitCoordinator.handleForwardedReadyTransaction(forwardedReady, getSender(), this);
 746         } else {
 747             ActorSelection leader = getLeader();
 748             if (!isLeaderActive || leader == null) {
 749                 messageRetrySupport.addMessageToRetry(forwardedReady, getSender(),
 750                         "Could not commit transaction " + forwardedReady.getTransactionId());
 751             } else {
 752                 LOG.debug("{}: Forwarding ForwardedReadyTransaction to leader {}", persistenceId(), leader);
 753
 754                 ReadyLocalTransaction readyLocal = new ReadyLocalTransaction(forwardedReady.getTransactionId(),
 755                         forwardedReady.getTransaction().getSnapshot(), forwardedReady.isDoImmediateCommit());
 756                 readyLocal.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 757                 leader.forward(readyLocal, getContext());
 758             }
 759         }
 760     }
 761
 762     private void handleAbortTransaction(final AbortTransaction abort) {
 763         doAbortTransaction(abort.getTransactionId(), getSender());
 764     }
 765
 766     void doAbortTransaction(final Identifier transactionID, final ActorRef sender) {
 767         commitCoordinator.handleAbort(transactionID, sender, this);
 768     }
 769
 770     private void handleCreateTransaction(final Object message) {
 771         if (isLeader()) {
 772             createTransaction(CreateTransaction.fromSerializable(message));
 773         } else if (getLeader() != null) {
 774             getLeader().forward(message, getContext());
 775         } else {
 776             getSender().tell(new Failure(new NoShardLeaderException(
 777                     "Could not create a shard transaction", persistenceId())), getSelf());
 778         }
 779     }
 780
 781     private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
 782         final LocalHistoryIdentifier id = closeTransactionChain.getIdentifier();
 783         store.closeTransactionChain(id, null);
 784         store.purgeTransactionChain(id, null);
 785     }
 786
 787     @SuppressWarnings("checkstyle:IllegalCatch")
 788     private void createTransaction(final CreateTransaction createTransaction) {
 789         try {
 790             if (TransactionType.fromInt(createTransaction.getTransactionType()) != TransactionType.READ_ONLY
 791                     && failIfIsolatedLeader(getSender())) {
 792                 return;
 793             }
 794
 795             ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
 796                 createTransaction.getTransactionId());
 797
 798             getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
 799                     createTransaction.getTransactionId(), createTransaction.getVersion()).toSerializable(), getSelf());
 800         } catch (Exception e) {
 801             getSender().tell(new Failure(e), getSelf());
 802         }
 803     }
 804
 805     private ActorRef createTransaction(final int transactionType, final TransactionIdentifier transactionId) {
 806         LOG.debug("{}: Creating transaction : {} ", persistenceId(), transactionId);
 807         return transactionActorFactory.newShardTransaction(TransactionType.fromInt(transactionType),
 808             transactionId);
 809     }
 810
 811     private void updateSchemaContext(final UpdateSchemaContext message) {
 812         updateSchemaContext(message.getSchemaContext());
 813     }
 814
 815     @VisibleForTesting
 816     void updateSchemaContext(final SchemaContext schemaContext) {
 817         store.updateSchemaContext(schemaContext);
 818     }
 819
 820     private boolean isMetricsCaptureEnabled() {
 821         CommonConfig config = new CommonConfig(getContext().system().settings().config());
 822         return config.isMetricCaptureEnabled();
 823     }
 824
 825     @Override
 826     @VisibleForTesting
 827     public RaftActorSnapshotCohort getRaftActorSnapshotCohort() {
 828         return snapshotCohort;
 829     }
 830
 831     @Override
 832     @Nonnull
 833     protected RaftActorRecoveryCohort getRaftActorRecoveryCohort() {
 834         return new ShardRecoveryCoordinator(store,
 835             restoreFromSnapshot != null ? restoreFromSnapshot.getSnapshot() : null, persistenceId(), LOG);
 836     }
 837
 838     @Override
 839     protected void onRecoveryComplete() {
 840         restoreFromSnapshot = null;
 841
 842         //notify shard manager
 843         getContext().parent().tell(new ActorInitialized(), getSelf());
 844
 845         // Being paranoid here - this method should only be called once but just in case...
 846         if (txCommitTimeoutCheckSchedule == null) {
 847             // Schedule a message to be periodically sent to check if the current in-progress
 848             // transaction should be expired and aborted.
 849             FiniteDuration period = Duration.create(transactionCommitTimeout / 3, TimeUnit.MILLISECONDS);
 850             txCommitTimeoutCheckSchedule = getContext().system().scheduler().schedule(
 851                     period, period, getSelf(),
 852                     TX_COMMIT_TIMEOUT_CHECK_MESSAGE, getContext().dispatcher(), ActorRef.noSender());
 853         }
 854     }
 855
 856     @Override
 857     protected void applyState(final ActorRef clientActor, final Identifier identifier, final Object data) {
 858         if (data instanceof Payload) {
 859             try {
 860                 store.applyReplicatedPayload(identifier, (Payload)data);
 861             } catch (DataValidationFailedException | IOException e) {
 862                 LOG.error("{}: Error applying replica {}", persistenceId(), identifier, e);
 863             }
 864         } else {
 865             LOG.error("{}: Unknown state for {} received {}", persistenceId(), identifier, data);
 866         }
 867     }
 868
 869     @Override
 870     protected void onStateChanged() {
 871         boolean isLeader = isLeader();
 872         boolean hasLeader = hasLeader();
 873         changeSupport.onLeadershipChange(isLeader, hasLeader);
 874         treeChangeSupport.onLeadershipChange(isLeader, hasLeader);
 875
 876         // If this actor is no longer the leader close all the transaction chains
 877         if (!isLeader) {
 878             if (LOG.isDebugEnabled()) {
 879                 LOG.debug(
 880                     "{}: onStateChanged: Closing all transaction chains because shard {} is no longer the leader",
 881                     persistenceId(), getId());
 882             }
 883
 884             paused = false;
 885             store.purgeLeaderState();
 886         }
 887
 888         if (hasLeader && !isIsolatedLeader()) {
 889             messageRetrySupport.retryMessages();
 890         }
 891     }
 892
 893     @Override
 894     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 895         shardMBean.incrementLeadershipChangeCount();
 896         paused = false;
 897
 898         if (!isLeader()) {
 899             if (!knownFrontends.isEmpty()) {
 900                 LOG.debug("{}: removing frontend state for {}", persistenceId(), knownFrontends.keySet());
 901                 knownFrontends = ImmutableMap.of();
 902             }
 903
 904             requestMessageAssembler.close();
 905
 906             if (!hasLeader()) {
 907                 // No leader anywhere, nothing else to do
 908                 return;
 909             }
 910
 911             // Another leader was elected. If we were the previous leader and had pending transactions, convert
 912             // them to transaction messages and send to the new leader.
 913             ActorSelection leader = getLeader();
 914             if (leader != null) {
 915                 Collection<?> messagesToForward = convertPendingTransactionsToMessages();
 916
 917                 if (!messagesToForward.isEmpty()) {
 918                     LOG.debug("{}: Forwarding {} pending transaction messages to leader {}", persistenceId(),
 919                             messagesToForward.size(), leader);
 920
 921                     for (Object message : messagesToForward) {
 922                         leader.tell(message, self());
 923                     }
 924                 }
 925             } else {
 926                 commitCoordinator.abortPendingTransactions("The transacton was aborted due to inflight leadership "
 927                         + "change and the leader address isn't available.", this);
 928             }
 929         } else {
 930             // We have become the leader, we need to reconstruct frontend state
 931             knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 932             LOG.debug("{}: became leader with frontend state for {}", persistenceId(), knownFrontends.keySet());
 933         }
 934
 935         if (!isIsolatedLeader()) {
 936             messageRetrySupport.retryMessages();
 937         }
 938     }
 939
 940     /**
 941      * Clears all pending transactions and converts them to messages to be forwarded to a new leader.
 942      *
 943      * @return the converted messages
 944      */
 945     public Collection<?> convertPendingTransactionsToMessages() {
 946         return commitCoordinator.convertPendingTransactionsToMessages(
 947                 datastoreContext.getShardBatchedModificationCount());
 948     }
 949
 950     @Override
 951     protected void pauseLeader(final Runnable operation) {
 952         LOG.debug("{}: In pauseLeader, operation: {}", persistenceId(), operation);
 953         paused = true;
 954
 955         // Tell-based protocol can replay transaction state, so it is safe to blow it up when we are paused.
 956         knownFrontends.values().forEach(LeaderFrontendState::retire);
 957         knownFrontends = ImmutableMap.of();
 958
 959         store.setRunOnPendingTransactionsComplete(operation);
 960     }
 961
 962     @Override
 963     protected void unpauseLeader() {
 964         LOG.debug("{}: In unpauseLeader", persistenceId());
 965         paused = false;
 966
 967         store.setRunOnPendingTransactionsComplete(null);
 968
 969         // Restore tell-based protocol state as if we were becoming the leader
 970         knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 971     }
 972
 973     @Override
 974     protected OnDemandRaftState.AbstractBuilder<?> newOnDemandRaftStateBuilder() {
 975         return OnDemandShardState.newBuilder().treeChangeListenerActors(treeChangeSupport.getListenerActors())
 976                 .dataChangeListenerActors(changeSupport.getListenerActors())
 977                 .commitCohortActors(store.getCohortActors());
 978     }
 979
 980     @Override
 981     public String persistenceId() {
 982         return this.name;
 983     }
 984
 985     @VisibleForTesting
 986     ShardCommitCoordinator getCommitCoordinator() {
 987         return commitCoordinator;
 988     }
 989
 990     public DatastoreContext getDatastoreContext() {
 991         return datastoreContext;
 992     }
 993
 994     @VisibleForTesting
 995     public ShardDataTree getDataStore() {
 996         return store;
 997     }
 998
 999     @VisibleForTesting
1000     ShardStats getShardMBean() {
1001         return shardMBean;
1002     }
1003
1004     public static Builder builder() {
1005         return new Builder();
1006     }
1007
1008     public abstract static class AbstractBuilder<T extends AbstractBuilder<T, S>, S extends Shard> {
1009         private final Class<S> shardClass;
1010         private ShardIdentifier id;
1011         private Map<String, String> peerAddresses = Collections.emptyMap();
1012         private DatastoreContext datastoreContext;
1013         private SchemaContextProvider schemaContextProvider;
1014         private DatastoreSnapshot.ShardSnapshot restoreFromSnapshot;
1015         private TipProducingDataTree dataTree;
1016         private volatile boolean sealed;
1017
1018         protected AbstractBuilder(final Class<S> shardClass) {
1019             this.shardClass = shardClass;
1020         }
1021
1022         protected void checkSealed() {
1023             Preconditions.checkState(!sealed, "Builder isalready sealed - further modifications are not allowed");
1024         }
1025
1026         @SuppressWarnings("unchecked")
1027         private T self() {
1028             return (T) this;
1029         }
1030
1031         public T id(final ShardIdentifier newId) {
1032             checkSealed();
1033             this.id = newId;
1034             return self();
1035         }
1036
1037         public T peerAddresses(final Map<String, String> newPeerAddresses) {
1038             checkSealed();
1039             this.peerAddresses = newPeerAddresses;
1040             return self();
1041         }
1042
1043         public T datastoreContext(final DatastoreContext newDatastoreContext) {
1044             checkSealed();
1045             this.datastoreContext = newDatastoreContext;
1046             return self();
1047         }
1048
1049         public T schemaContextProvider(final SchemaContextProvider schemaContextProvider) {
1050             checkSealed();
1051             this.schemaContextProvider = Preconditions.checkNotNull(schemaContextProvider);
1052             return self();
1053         }
1054
1055         public T restoreFromSnapshot(final DatastoreSnapshot.ShardSnapshot newRestoreFromSnapshot) {
1056             checkSealed();
1057             this.restoreFromSnapshot = newRestoreFromSnapshot;
1058             return self();
1059         }
1060
1061         public T dataTree(final TipProducingDataTree newDataTree) {
1062             checkSealed();
1063             this.dataTree = newDataTree;
1064             return self();
1065         }
1066
1067         public ShardIdentifier getId() {
1068             return id;
1069         }
1070
1071         public Map<String, String> getPeerAddresses() {
1072             return peerAddresses;
1073         }
1074
1075         public DatastoreContext getDatastoreContext() {
1076             return datastoreContext;
1077         }
1078
1079         public SchemaContext getSchemaContext() {
1080             return Verify.verifyNotNull(schemaContextProvider.getSchemaContext());
1081         }
1082
1083         public DatastoreSnapshot.ShardSnapshot getRestoreFromSnapshot() {
1084             return restoreFromSnapshot;
1085         }
1086
1087         public TipProducingDataTree getDataTree() {
1088             return dataTree;
1089         }
1090
1091         public TreeType getTreeType() {
1092             switch (datastoreContext.getLogicalStoreType()) {
1093                 case CONFIGURATION:
1094                     return TreeType.CONFIGURATION;
1095                 case OPERATIONAL:
1096                     return TreeType.OPERATIONAL;
1097                 default:
1098                     throw new IllegalStateException("Unhandled logical store type "
1099                             + datastoreContext.getLogicalStoreType());
1100             }
1101         }
1102
1103         protected void verify() {
1104             Preconditions.checkNotNull(id, "id should not be null");
1105             Preconditions.checkNotNull(peerAddresses, "peerAddresses should not be null");
1106             Preconditions.checkNotNull(datastoreContext, "dataStoreContext should not be null");
1107             Preconditions.checkNotNull(schemaContextProvider, "schemaContextProvider should not be null");
1108         }
1109
1110         public Props props() {
1111             sealed = true;
1112             verify();
1113             return Props.create(shardClass, this);
1114         }
1115     }
1116
1117     public static class Builder extends AbstractBuilder<Builder, Shard> {
1118         private Builder() {
1119             super(Shard.class);
1120         }
1121     }
1122
1123     Ticker ticker() {
1124         return Ticker.systemTicker();
1125     }
1126
1127     void scheduleNextPendingTransaction() {
1128         self().tell(RESUME_NEXT_PENDING_TRANSACTION, ActorRef.noSender());
1129     }
1130 }