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