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.ShardDataTreeListenerInfoMXBeanImpl;
  64 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
  65 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
  66 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
  67 import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
  68 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  69 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  70 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  71 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  72 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  73 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  74 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  75 import org.opendaylight.controller.cluster.datastore.messages.GetShardDataTree;
  76 import org.opendaylight.controller.cluster.datastore.messages.MakeLeaderLocal;
  77 import org.opendaylight.controller.cluster.datastore.messages.OnDemandShardState;
  78 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
  79 import org.opendaylight.controller.cluster.datastore.messages.PersistAbortTransactionPayload;
  80 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  81 import org.opendaylight.controller.cluster.datastore.messages.RegisterChangeListener;
  82 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  83 import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
  84 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
  85 import org.opendaylight.controller.cluster.datastore.persisted.AbortTransactionPayload;
  86 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot;
  87 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot.ShardSnapshot;
  88 import org.opendaylight.controller.cluster.messaging.MessageAssembler;
  89 import org.opendaylight.controller.cluster.messaging.MessageSlicer;
  90 import org.opendaylight.controller.cluster.messaging.SliceOptions;
  91 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  92 import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
  93 import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
  94 import org.opendaylight.controller.cluster.raft.LeadershipTransferFailedException;
  95 import org.opendaylight.controller.cluster.raft.RaftActor;
  96 import org.opendaylight.controller.cluster.raft.RaftActorRecoveryCohort;
  97 import org.opendaylight.controller.cluster.raft.RaftActorSnapshotCohort;
  98 import org.opendaylight.controller.cluster.raft.RaftState;
  99 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
 100 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
 101 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
 102 import org.opendaylight.controller.cluster.raft.messages.RequestLeadership;
 103 import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
 104 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 105 import org.opendaylight.yangtools.concepts.Identifier;
 106 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
 107 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
 108 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 109 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 110 import org.opendaylight.yangtools.yang.model.api.SchemaContextProvider;
 111 import scala.concurrent.duration.Duration;
 112 import scala.concurrent.duration.FiniteDuration;
 113
 114 /**
 115  * A Shard represents a portion of the logical data tree.
 116  *
 117  * <p>
 118  * Our Shard uses InMemoryDataTree as it's internal representation and delegates all requests it
 119  */
 120 public class Shard extends RaftActor {
 121
 122     @VisibleForTesting
 123     static final Object TX_COMMIT_TIMEOUT_CHECK_MESSAGE = new Object() {
 124         @Override
 125         public String toString() {
 126             return "txCommitTimeoutCheck";
 127         }
 128     };
 129
 130     @VisibleForTesting
 131     static final Object GET_SHARD_MBEAN_MESSAGE = new Object() {
 132         @Override
 133         public String toString() {
 134             return "getShardMBeanMessage";
 135         }
 136     };
 137
 138     static final Object RESUME_NEXT_PENDING_TRANSACTION = new Object() {
 139         @Override
 140         public String toString() {
 141             return "resumeNextPendingTransaction";
 142         }
 143     };
 144
 145     // FIXME: shard names should be encapsulated in their own class and this should be exposed as a constant.
 146     public static final String DEFAULT_NAME = "default";
 147
 148     private static final Collection<ABIVersion> SUPPORTED_ABIVERSIONS;
 149
 150     static {
 151         final ABIVersion[] values = ABIVersion.values();
 152         final ABIVersion[] real = Arrays.copyOfRange(values, 1, values.length - 1);
 153         SUPPORTED_ABIVERSIONS = ImmutableList.copyOf(real).reverse();
 154     }
 155
 156     // FIXME: make this a dynamic property based on mailbox size and maximum number of clients
 157     private static final int CLIENT_MAX_MESSAGES = 1000;
 158
 159     // The state of this Shard
 160     private final ShardDataTree store;
 161
 162     /// The name of this shard
 163     private final String name;
 164
 165     private final String shardName;
 166
 167     private final ShardStats shardMBean;
 168
 169     private final ShardDataTreeListenerInfoMXBeanImpl listenerInfoMXBean;
 170
 171     private DatastoreContext datastoreContext;
 172
 173     private final ShardCommitCoordinator commitCoordinator;
 174
 175     private long transactionCommitTimeout;
 176
 177     private Cancellable txCommitTimeoutCheckSchedule;
 178
 179     private final Optional<ActorRef> roleChangeNotifier;
 180
 181     private final MessageTracker appendEntriesReplyTracker;
 182
 183     private final ShardTransactionActorFactory transactionActorFactory;
 184
 185     private final ShardSnapshotCohort snapshotCohort;
 186
 187     private final DataTreeChangeListenerSupport treeChangeSupport = new DataTreeChangeListenerSupport(this);
 188     private final DataChangeListenerSupport changeSupport = new DataChangeListenerSupport(this);
 189
 190
 191     private ShardSnapshot restoreFromSnapshot;
 192
 193     private final ShardTransactionMessageRetrySupport messageRetrySupport;
 194
 195     private final FrontendMetadata frontendMetadata;
 196     private Map<FrontendIdentifier, LeaderFrontendState> knownFrontends = ImmutableMap.of();
 197     private boolean paused;
 198
 199     private final MessageSlicer responseMessageSlicer;
 200     private final Dispatchers dispatchers;
 201
 202     private final MessageAssembler requestMessageAssembler;
 203
 204     protected Shard(final AbstractBuilder<?, ?> builder) {
 205         super(builder.getId().toString(), builder.getPeerAddresses(),
 206                 Optional.of(builder.getDatastoreContext().getShardRaftConfig()), DataStoreVersions.CURRENT_VERSION);
 207
 208         this.name = builder.getId().toString();
 209         this.shardName = builder.getId().getShardName();
 210         this.datastoreContext = builder.getDatastoreContext();
 211         this.restoreFromSnapshot = builder.getRestoreFromSnapshot();
 212         this.frontendMetadata = new FrontendMetadata(name);
 213
 214         setPersistence(datastoreContext.isPersistent());
 215
 216         LOG.info("Shard created : {}, persistent : {}", name, datastoreContext.isPersistent());
 217
 218         ShardDataTreeChangeListenerPublisherActorProxy treeChangeListenerPublisher =
 219                 new ShardDataTreeChangeListenerPublisherActorProxy(getContext(), name + "-DTCL-publisher", name);
 220         ShardDataChangeListenerPublisherActorProxy dataChangeListenerPublisher =
 221                 new ShardDataChangeListenerPublisherActorProxy(getContext(), name + "-DCL-publisher", name);
 222         if (builder.getDataTree() != null) {
 223             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getDataTree(),
 224                     treeChangeListenerPublisher, dataChangeListenerPublisher, name, frontendMetadata);
 225         } else {
 226             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getTreeType(),
 227                     builder.getDatastoreContext().getStoreRoot(), treeChangeListenerPublisher,
 228                     dataChangeListenerPublisher, name, frontendMetadata);
 229         }
 230
 231         shardMBean = ShardMBeanFactory.getShardStatsMBean(name, datastoreContext.getDataStoreMXBeanType(), this);
 232
 233         if (isMetricsCaptureEnabled()) {
 234             getContext().become(new MeteringBehavior(this));
 235         }
 236
 237         commitCoordinator = new ShardCommitCoordinator(store, LOG, this.name);
 238
 239         setTransactionCommitTimeout();
 240
 241         // create a notifier actor for each cluster member
 242         roleChangeNotifier = createRoleChangeNotifier(name);
 243
 244         appendEntriesReplyTracker = new MessageTracker(AppendEntriesReply.class,
 245                 getRaftActorContext().getConfigParams().getIsolatedCheckIntervalInMillis());
 246
 247         dispatchers = new Dispatchers(context().system().dispatchers());
 248         transactionActorFactory = new ShardTransactionActorFactory(store, datastoreContext,
 249             dispatchers.getDispatcherPath(Dispatchers.DispatcherType.Transaction),
 250                 self(), getContext(), shardMBean, builder.getId().getShardName());
 251
 252         snapshotCohort = ShardSnapshotCohort.create(getContext(), builder.getId().getMemberName(), store, LOG,
 253             this.name);
 254
 255         messageRetrySupport = new ShardTransactionMessageRetrySupport(this);
 256
 257         responseMessageSlicer = MessageSlicer.builder().logContext(this.name)
 258                 .messageSliceSize(datastoreContext.getMaximumMessageSliceSize())
 259                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 260                 .expireStateAfterInactivity(2, TimeUnit.MINUTES).build();
 261
 262         requestMessageAssembler = MessageAssembler.builder().logContext(this.name)
 263                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 264                 .assembledMessageCallback((message, sender) -> self().tell(message, sender))
 265                 .expireStateAfterInactivity(datastoreContext.getRequestTimeout(), TimeUnit.NANOSECONDS).build();
 266
 267         listenerInfoMXBean = new ShardDataTreeListenerInfoMXBeanImpl(name, datastoreContext.getDataStoreMXBeanType(),
 268                 self());
 269         listenerInfoMXBean.register();
 270     }
 271
 272     private void setTransactionCommitTimeout() {
 273         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
 274                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS) / 2;
 275     }
 276
 277     private Optional<ActorRef> createRoleChangeNotifier(final String shardId) {
 278         ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
 279             RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
 280         return Optional.of(shardRoleChangeNotifier);
 281     }
 282
 283     @Override
 284     public void postStop() {
 285         LOG.info("Stopping Shard {}", persistenceId());
 286
 287         super.postStop();
 288
 289         messageRetrySupport.close();
 290
 291         if (txCommitTimeoutCheckSchedule != null) {
 292             txCommitTimeoutCheckSchedule.cancel();
 293         }
 294
 295         commitCoordinator.abortPendingTransactions("Transaction aborted due to shutdown.", this);
 296
 297         shardMBean.unregisterMBean();
 298         listenerInfoMXBean.unregister();
 299     }
 300
 301     @Override
 302     protected void handleRecover(final Object message) {
 303         LOG.debug("{}: onReceiveRecover: Received message {} from {}", persistenceId(), message.getClass(),
 304             getSender());
 305
 306         super.handleRecover(message);
 307         if (LOG.isTraceEnabled()) {
 308             appendEntriesReplyTracker.begin();
 309         }
 310     }
 311
 312     @Override
 313     protected void handleNonRaftCommand(final Object message) {
 314         try (MessageTracker.Context context = appendEntriesReplyTracker.received(message)) {
 315             final Optional<Error> maybeError = context.error();
 316             if (maybeError.isPresent()) {
 317                 LOG.trace("{} : AppendEntriesReply failed to arrive at the expected interval {}", persistenceId(),
 318                     maybeError.get());
 319             }
 320
 321             store.resetTransactionBatch();
 322
 323             if (message instanceof RequestEnvelope) {
 324                 handleRequestEnvelope((RequestEnvelope)message);
 325             } else if (MessageAssembler.isHandledMessage(message)) {
 326                 handleRequestAssemblerMessage(message);
 327             } else if (message instanceof ConnectClientRequest) {
 328                 handleConnectClient((ConnectClientRequest)message);
 329             } else if (CreateTransaction.isSerializedType(message)) {
 330                 handleCreateTransaction(message);
 331             } else if (message instanceof BatchedModifications) {
 332                 handleBatchedModifications((BatchedModifications)message);
 333             } else if (message instanceof ForwardedReadyTransaction) {
 334                 handleForwardedReadyTransaction((ForwardedReadyTransaction) message);
 335             } else if (message instanceof ReadyLocalTransaction) {
 336                 handleReadyLocalTransaction((ReadyLocalTransaction)message);
 337             } else if (CanCommitTransaction.isSerializedType(message)) {
 338                 handleCanCommitTransaction(CanCommitTransaction.fromSerializable(message));
 339             } else if (CommitTransaction.isSerializedType(message)) {
 340                 handleCommitTransaction(CommitTransaction.fromSerializable(message));
 341             } else if (AbortTransaction.isSerializedType(message)) {
 342                 handleAbortTransaction(AbortTransaction.fromSerializable(message));
 343             } else if (CloseTransactionChain.isSerializedType(message)) {
 344                 closeTransactionChain(CloseTransactionChain.fromSerializable(message));
 345             } else if (message instanceof RegisterChangeListener) {
 346                 changeSupport.onMessage((RegisterChangeListener) message, isLeader(), hasLeader());
 347             } else if (message instanceof RegisterDataTreeChangeListener) {
 348                 treeChangeSupport.onMessage((RegisterDataTreeChangeListener) message, isLeader(), hasLeader());
 349             } else if (message instanceof UpdateSchemaContext) {
 350                 updateSchemaContext((UpdateSchemaContext) message);
 351             } else if (message instanceof PeerAddressResolved) {
 352                 PeerAddressResolved resolved = (PeerAddressResolved) message;
 353                 setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
 354             } else if (TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
 355                 commitTimeoutCheck();
 356             } else if (message instanceof DatastoreContext) {
 357                 onDatastoreContext((DatastoreContext)message);
 358             } else if (message instanceof RegisterRoleChangeListener) {
 359                 roleChangeNotifier.get().forward(message, context());
 360             } else if (message instanceof FollowerInitialSyncUpStatus) {
 361                 shardMBean.setFollowerInitialSyncStatus(((FollowerInitialSyncUpStatus) message).isInitialSyncDone());
 362                 context().parent().tell(message, self());
 363             } else if (GET_SHARD_MBEAN_MESSAGE.equals(message)) {
 364                 sender().tell(getShardMBean(), self());
 365             } else if (message instanceof GetShardDataTree) {
 366                 sender().tell(store.getDataTree(), self());
 367             } else if (message instanceof ServerRemoved) {
 368                 context().parent().forward(message, context());
 369             } else if (ShardTransactionMessageRetrySupport.TIMER_MESSAGE_CLASS.isInstance(message)) {
 370                 messageRetrySupport.onTimerMessage(message);
 371             } else if (message instanceof DataTreeCohortActorRegistry.CohortRegistryCommand) {
 372                 store.processCohortRegistryCommand(getSender(),
 373                         (DataTreeCohortActorRegistry.CohortRegistryCommand) message);
 374             } else if (message instanceof PersistAbortTransactionPayload) {
 375                 final TransactionIdentifier txId = ((PersistAbortTransactionPayload) message).getTransactionId();
 376                 persistPayload(txId, AbortTransactionPayload.create(txId), true);
 377             } else if (message instanceof MakeLeaderLocal) {
 378                 onMakeLeaderLocal();
 379             } else if (RESUME_NEXT_PENDING_TRANSACTION.equals(message)) {
 380                 store.resumeNextPendingTransaction();
 381             } else if (!responseMessageSlicer.handleMessage(message)) {
 382                 super.handleNonRaftCommand(message);
 383             }
 384         }
 385     }
 386
 387     private void handleRequestAssemblerMessage(final Object message) {
 388         dispatchers.getDispatcher(DispatcherType.Serialization).execute(() -> {
 389             JavaSerializer.currentSystem().value_$eq((ExtendedActorSystem) context().system());
 390             requestMessageAssembler.handleMessage(message, self());
 391         });
 392     }
 393
 394     @SuppressWarnings("checkstyle:IllegalCatch")
 395     private void handleRequestEnvelope(final RequestEnvelope envelope) {
 396         final long now = ticker().read();
 397         try {
 398             final RequestSuccess<?, ?> success = handleRequest(envelope, now);
 399             if (success != null) {
 400                 final long executionTimeNanos = ticker().read() - now;
 401                 if (success instanceof SliceableMessage) {
 402                     dispatchers.getDispatcher(DispatcherType.Serialization).execute(() ->
 403                         responseMessageSlicer.slice(SliceOptions.builder().identifier(success.getTarget())
 404                             .message(envelope.newSuccessEnvelope(success, executionTimeNanos))
 405                             .sendTo(envelope.getMessage().getReplyTo()).replyTo(self())
 406                             .onFailureCallback(t -> {
 407                                 LOG.warn("Error slicing response {}", success, t);
 408                             }).build()));
 409                 } else {
 410                     envelope.sendSuccess(success, executionTimeNanos);
 411                 }
 412             }
 413         } catch (RequestException e) {
 414             LOG.debug("{}: request {} failed", persistenceId(), envelope, e);
 415             envelope.sendFailure(e, ticker().read() - now);
 416         } catch (Exception e) {
 417             LOG.debug("{}: request {} caused failure", persistenceId(), envelope, e);
 418             envelope.sendFailure(new RuntimeRequestException("Request failed to process", e),
 419                 ticker().read() - now);
 420         }
 421     }
 422
 423     private void commitTimeoutCheck() {
 424         store.checkForExpiredTransactions(transactionCommitTimeout, this::updateAccess);
 425         commitCoordinator.checkForExpiredTransactions(transactionCommitTimeout, this);
 426         requestMessageAssembler.checkExpiredAssembledMessageState();
 427     }
 428
 429     private Optional<Long> updateAccess(final SimpleShardDataTreeCohort cohort) {
 430         final FrontendIdentifier frontend = cohort.getIdentifier().getHistoryId().getClientId().getFrontendId();
 431         final LeaderFrontendState state = knownFrontends.get(frontend);
 432         if (state == null) {
 433             // Not tell-based protocol, do nothing
 434             return Optional.absent();
 435         }
 436
 437         if (isIsolatedLeader()) {
 438             // We are isolated and no new request can come through until we emerge from it. We are still updating
 439             // liveness of frontend when we see it attempting to communicate. Use the last access timer.
 440             return Optional.of(state.getLastSeenTicks());
 441         }
 442
 443         // If this frontend has freshly connected, give it some time to catch up before killing its transactions.
 444         return Optional.of(state.getLastConnectTicks());
 445     }
 446
 447     private void onMakeLeaderLocal() {
 448         LOG.debug("{}: onMakeLeaderLocal received", persistenceId());
 449         if (isLeader()) {
 450             getSender().tell(new Status.Success(null), getSelf());
 451             return;
 452         }
 453
 454         final ActorSelection leader = getLeader();
 455
 456         if (leader == null) {
 457             // Leader is not present. The cluster is most likely trying to
 458             // elect a leader and we should let that run its normal course
 459
 460             // TODO we can wait for the election to complete and retry the
 461             // request. We can also let the caller retry by sending a flag
 462             // in the response indicating the request is "reTryable".
 463             getSender().tell(new Failure(
 464                     new LeadershipTransferFailedException("We cannot initiate leadership transfer to local node. "
 465                             + "Currently there is no leader for " + persistenceId())),
 466                     getSelf());
 467             return;
 468         }
 469
 470         leader.tell(new RequestLeadership(getId(), getSender()), getSelf());
 471     }
 472
 473     // Acquire our frontend tracking handle and verify generation matches
 474     @Nullable
 475     private LeaderFrontendState findFrontend(final ClientIdentifier clientId) throws RequestException {
 476         final LeaderFrontendState existing = knownFrontends.get(clientId.getFrontendId());
 477         if (existing != null) {
 478             final int cmp = Long.compareUnsigned(existing.getIdentifier().getGeneration(), clientId.getGeneration());
 479             if (cmp == 0) {
 480                 existing.touch();
 481                 return existing;
 482             }
 483             if (cmp > 0) {
 484                 LOG.debug("{}: rejecting request from outdated client {}", persistenceId(), clientId);
 485                 throw new RetiredGenerationException(existing.getIdentifier().getGeneration());
 486             }
 487
 488             LOG.info("{}: retiring state {}, outdated by request from client {}", persistenceId(), existing, clientId);
 489             existing.retire();
 490             knownFrontends.remove(clientId.getFrontendId());
 491         } else {
 492             LOG.debug("{}: client {} is not yet known", persistenceId(), clientId);
 493         }
 494
 495         return null;
 496     }
 497
 498     private LeaderFrontendState getFrontend(final ClientIdentifier clientId) throws RequestException {
 499         final LeaderFrontendState ret = findFrontend(clientId);
 500         if (ret != null) {
 501             return ret;
 502         }
 503
 504         // TODO: a dedicated exception would be better, but this is technically true, too
 505         throw new OutOfSequenceEnvelopeException(0);
 506     }
 507
 508     @Nonnull
 509     private static ABIVersion selectVersion(final ConnectClientRequest message) {
 510         final Range<ABIVersion> clientRange = Range.closed(message.getMinVersion(), message.getMaxVersion());
 511         for (ABIVersion v : SUPPORTED_ABIVERSIONS) {
 512             if (clientRange.contains(v)) {
 513                 return v;
 514             }
 515         }
 516
 517         throw new IllegalArgumentException(String.format(
 518             "No common version between backend versions %s and client versions %s", SUPPORTED_ABIVERSIONS,
 519             clientRange));
 520     }
 521
 522     @SuppressWarnings("checkstyle:IllegalCatch")
 523     private void handleConnectClient(final ConnectClientRequest message) {
 524         try {
 525             final ClientIdentifier clientId = message.getTarget();
 526             final LeaderFrontendState existing = findFrontend(clientId);
 527             if (existing != null) {
 528                 existing.touch();
 529             }
 530
 531             if (!isLeader() || !isLeaderActive()) {
 532                 LOG.info("{}: not currently leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 533                                 + "isLeadershipTransferInProgress: {}.",
 534                         persistenceId(), message, isLeader(), isLeaderActive(), isLeadershipTransferInProgress());
 535                 throw new NotLeaderException(getSelf());
 536             }
 537
 538             final ABIVersion selectedVersion = selectVersion(message);
 539             final LeaderFrontendState frontend;
 540             if (existing == null) {
 541                 frontend = new LeaderFrontendState(persistenceId(), clientId, store);
 542                 knownFrontends.put(clientId.getFrontendId(), frontend);
 543                 LOG.debug("{}: created state {} for client {}", persistenceId(), frontend, clientId);
 544             } else {
 545                 frontend = existing;
 546             }
 547
 548             frontend.reconnect();
 549             message.getReplyTo().tell(new ConnectClientSuccess(message.getTarget(), message.getSequence(), getSelf(),
 550                 ImmutableList.of(), store.getDataTree(), CLIENT_MAX_MESSAGES).toVersion(selectedVersion),
 551                 ActorRef.noSender());
 552         } catch (RequestException | RuntimeException e) {
 553             message.getReplyTo().tell(new Failure(e), ActorRef.noSender());
 554         }
 555     }
 556
 557     @Nullable
 558     private RequestSuccess<?, ?> handleRequest(final RequestEnvelope envelope, final long now)
 559             throws RequestException {
 560         // We are not the leader, hence we want to fail-fast.
 561         if (!isLeader() || paused || !isLeaderActive()) {
 562             LOG.debug("{}: not currently active leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 563                             + "isLeadershipTransferInProgress: {}, paused: {}",
 564                     persistenceId(), envelope, isLeader(), isLeaderActive(), isLeadershipTransferInProgress(), paused);
 565             throw new NotLeaderException(getSelf());
 566         }
 567
 568         final Request<?, ?> request = envelope.getMessage();
 569         if (request instanceof TransactionRequest) {
 570             final TransactionRequest<?> txReq = (TransactionRequest<?>)request;
 571             final ClientIdentifier clientId = txReq.getTarget().getHistoryId().getClientId();
 572             return getFrontend(clientId).handleTransactionRequest(txReq, envelope, now);
 573         } else if (request instanceof LocalHistoryRequest) {
 574             final LocalHistoryRequest<?> lhReq = (LocalHistoryRequest<?>)request;
 575             final ClientIdentifier clientId = lhReq.getTarget().getClientId();
 576             return getFrontend(clientId).handleLocalHistoryRequest(lhReq, envelope, now);
 577         } else {
 578             LOG.warn("{}: rejecting unsupported request {}", persistenceId(), request);
 579             throw new UnsupportedRequestException(request);
 580         }
 581     }
 582
 583     private boolean hasLeader() {
 584         return getLeaderId() != null;
 585     }
 586
 587     public int getPendingTxCommitQueueSize() {
 588         return store.getQueueSize();
 589     }
 590
 591     public int getCohortCacheSize() {
 592         return commitCoordinator.getCohortCacheSize();
 593     }
 594
 595     @Override
 596     protected Optional<ActorRef> getRoleChangeNotifier() {
 597         return roleChangeNotifier;
 598     }
 599
 600     String getShardName() {
 601         return shardName;
 602     }
 603
 604     @Override
 605     protected LeaderStateChanged newLeaderStateChanged(final String memberId, final String leaderId,
 606             final short leaderPayloadVersion) {
 607         return isLeader() ? new ShardLeaderStateChanged(memberId, leaderId, store.getDataTree(), leaderPayloadVersion)
 608                 : new ShardLeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 609     }
 610
 611     protected void onDatastoreContext(final DatastoreContext context) {
 612         datastoreContext = context;
 613
 614         setTransactionCommitTimeout();
 615
 616         setPersistence(datastoreContext.isPersistent());
 617
 618         updateConfigParams(datastoreContext.getShardRaftConfig());
 619     }
 620
 621     // applyState() will be invoked once consensus is reached on the payload
 622     void persistPayload(final Identifier id, final Payload payload, final boolean batchHint) {
 623         boolean canSkipPayload = !hasFollowers() && !persistence().isRecoveryApplicable();
 624         if (canSkipPayload) {
 625             applyState(self(), id, payload);
 626         } else {
 627             // We are faking the sender
 628             persistData(self(), id, payload, batchHint);
 629         }
 630     }
 631
 632     private void handleCommitTransaction(final CommitTransaction commit) {
 633         if (isLeader()) {
 634             commitCoordinator.handleCommit(commit.getTransactionId(), getSender(), this);
 635         } else {
 636             ActorSelection leader = getLeader();
 637             if (leader == null) {
 638                 messageRetrySupport.addMessageToRetry(commit, getSender(),
 639                         "Could not commit transaction " + commit.getTransactionId());
 640             } else {
 641                 LOG.debug("{}: Forwarding CommitTransaction to leader {}", persistenceId(), leader);
 642                 leader.forward(commit, getContext());
 643             }
 644         }
 645     }
 646
 647     private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
 648         LOG.debug("{}: Can committing transaction {}", persistenceId(), canCommit.getTransactionId());
 649
 650         if (isLeader()) {
 651             commitCoordinator.handleCanCommit(canCommit.getTransactionId(), getSender(), this);
 652         } else {
 653             ActorSelection leader = getLeader();
 654             if (leader == null) {
 655                 messageRetrySupport.addMessageToRetry(canCommit, getSender(),
 656                         "Could not canCommit transaction " + canCommit.getTransactionId());
 657             } else {
 658                 LOG.debug("{}: Forwarding CanCommitTransaction to leader {}", persistenceId(), leader);
 659                 leader.forward(canCommit, getContext());
 660             }
 661         }
 662     }
 663
 664     @SuppressWarnings("checkstyle:IllegalCatch")
 665     protected void handleBatchedModificationsLocal(final BatchedModifications batched, final ActorRef sender) {
 666         try {
 667             commitCoordinator.handleBatchedModifications(batched, sender, this);
 668         } catch (Exception e) {
 669             LOG.error("{}: Error handling BatchedModifications for Tx {}", persistenceId(),
 670                     batched.getTransactionId(), e);
 671             sender.tell(new Failure(e), getSelf());
 672         }
 673     }
 674
 675     private void handleBatchedModifications(final BatchedModifications batched) {
 676         // This message is sent to prepare the modifications transaction directly on the Shard as an
 677         // optimization to avoid the extra overhead of a separate ShardTransaction actor. On the last
 678         // BatchedModifications message, the caller sets the ready flag in the message indicating
 679         // modifications are complete. The reply contains the cohort actor path (this actor) for the caller
 680         // to initiate the 3-phase commit. This also avoids the overhead of sending an additional
 681         // ReadyTransaction message.
 682
 683         // If we're not the leader then forward to the leader. This is a safety measure - we shouldn't
 684         // normally get here if we're not the leader as the front-end (TransactionProxy) should determine
 685         // the primary/leader shard. However with timing and caching on the front-end, there's a small
 686         // window where it could have a stale leader during leadership transitions.
 687         //
 688         boolean isLeaderActive = isLeaderActive();
 689         if (isLeader() && isLeaderActive) {
 690             handleBatchedModificationsLocal(batched, getSender());
 691         } else {
 692             ActorSelection leader = getLeader();
 693             if (!isLeaderActive || leader == null) {
 694                 messageRetrySupport.addMessageToRetry(batched, getSender(),
 695                         "Could not process BatchedModifications " + batched.getTransactionId());
 696             } else {
 697                 // If this is not the first batch and leadership changed in between batched messages,
 698                 // we need to reconstruct previous BatchedModifications from the transaction
 699                 // DataTreeModification, honoring the max batched modification count, and forward all the
 700                 // previous BatchedModifications to the new leader.
 701                 Collection<BatchedModifications> newModifications = commitCoordinator
 702                         .createForwardedBatchedModifications(batched,
 703                                 datastoreContext.getShardBatchedModificationCount());
 704
 705                 LOG.debug("{}: Forwarding {} BatchedModifications to leader {}", persistenceId(),
 706                         newModifications.size(), leader);
 707
 708                 for (BatchedModifications bm : newModifications) {
 709                     leader.forward(bm, getContext());
 710                 }
 711             }
 712         }
 713     }
 714
 715     private boolean failIfIsolatedLeader(final ActorRef sender) {
 716         if (isIsolatedLeader()) {
 717             sender.tell(new Failure(new NoShardLeaderException(String.format(
 718                     "Shard %s was the leader but has lost contact with all of its followers. Either all"
 719                     + " other follower nodes are down or this node is isolated by a network partition.",
 720                     persistenceId()))), getSelf());
 721             return true;
 722         }
 723
 724         return false;
 725     }
 726
 727     protected boolean isIsolatedLeader() {
 728         return getRaftState() == RaftState.IsolatedLeader;
 729     }
 730
 731     @SuppressWarnings("checkstyle:IllegalCatch")
 732     private void handleReadyLocalTransaction(final ReadyLocalTransaction message) {
 733         LOG.debug("{}: handleReadyLocalTransaction for {}", persistenceId(), message.getTransactionId());
 734
 735         boolean isLeaderActive = isLeaderActive();
 736         if (isLeader() && isLeaderActive) {
 737             try {
 738                 commitCoordinator.handleReadyLocalTransaction(message, getSender(), this);
 739             } catch (Exception e) {
 740                 LOG.error("{}: Error handling ReadyLocalTransaction for Tx {}", persistenceId(),
 741                         message.getTransactionId(), e);
 742                 getSender().tell(new Failure(e), getSelf());
 743             }
 744         } else {
 745             ActorSelection leader = getLeader();
 746             if (!isLeaderActive || leader == null) {
 747                 messageRetrySupport.addMessageToRetry(message, getSender(),
 748                         "Could not process ready local transaction " + message.getTransactionId());
 749             } else {
 750                 LOG.debug("{}: Forwarding ReadyLocalTransaction to leader {}", persistenceId(), leader);
 751                 message.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 752                 leader.forward(message, getContext());
 753             }
 754         }
 755     }
 756
 757     private void handleForwardedReadyTransaction(final ForwardedReadyTransaction forwardedReady) {
 758         LOG.debug("{}: handleForwardedReadyTransaction for {}", persistenceId(), forwardedReady.getTransactionId());
 759
 760         boolean isLeaderActive = isLeaderActive();
 761         if (isLeader() && isLeaderActive) {
 762             commitCoordinator.handleForwardedReadyTransaction(forwardedReady, getSender(), this);
 763         } else {
 764             ActorSelection leader = getLeader();
 765             if (!isLeaderActive || leader == null) {
 766                 messageRetrySupport.addMessageToRetry(forwardedReady, getSender(),
 767                         "Could not process forwarded ready transaction " + forwardedReady.getTransactionId());
 768             } else {
 769                 LOG.debug("{}: Forwarding ForwardedReadyTransaction to leader {}", persistenceId(), leader);
 770
 771                 ReadyLocalTransaction readyLocal = new ReadyLocalTransaction(forwardedReady.getTransactionId(),
 772                         forwardedReady.getTransaction().getSnapshot(), forwardedReady.isDoImmediateCommit(),
 773                         forwardedReady.getParticipatingShardNames());
 774                 readyLocal.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 775                 leader.forward(readyLocal, getContext());
 776             }
 777         }
 778     }
 779
 780     private void handleAbortTransaction(final AbortTransaction abort) {
 781         doAbortTransaction(abort.getTransactionId(), getSender());
 782     }
 783
 784     void doAbortTransaction(final Identifier transactionID, final ActorRef sender) {
 785         commitCoordinator.handleAbort(transactionID, sender, this);
 786     }
 787
 788     private void handleCreateTransaction(final Object message) {
 789         if (isLeader()) {
 790             createTransaction(CreateTransaction.fromSerializable(message));
 791         } else if (getLeader() != null) {
 792             getLeader().forward(message, getContext());
 793         } else {
 794             getSender().tell(new Failure(new NoShardLeaderException(
 795                     "Could not create a shard transaction", persistenceId())), getSelf());
 796         }
 797     }
 798
 799     private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
 800         final LocalHistoryIdentifier id = closeTransactionChain.getIdentifier();
 801         store.closeTransactionChain(id, null);
 802         store.purgeTransactionChain(id, null);
 803     }
 804
 805     @SuppressWarnings("checkstyle:IllegalCatch")
 806     private void createTransaction(final CreateTransaction createTransaction) {
 807         try {
 808             if (TransactionType.fromInt(createTransaction.getTransactionType()) != TransactionType.READ_ONLY
 809                     && failIfIsolatedLeader(getSender())) {
 810                 return;
 811             }
 812
 813             ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
 814                 createTransaction.getTransactionId());
 815
 816             getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
 817                     createTransaction.getTransactionId(), createTransaction.getVersion()).toSerializable(), getSelf());
 818         } catch (Exception e) {
 819             getSender().tell(new Failure(e), getSelf());
 820         }
 821     }
 822
 823     private ActorRef createTransaction(final int transactionType, final TransactionIdentifier transactionId) {
 824         LOG.debug("{}: Creating transaction : {} ", persistenceId(), transactionId);
 825         return transactionActorFactory.newShardTransaction(TransactionType.fromInt(transactionType),
 826             transactionId);
 827     }
 828
 829     private void updateSchemaContext(final UpdateSchemaContext message) {
 830         updateSchemaContext(message.getSchemaContext());
 831     }
 832
 833     @VisibleForTesting
 834     void updateSchemaContext(final SchemaContext schemaContext) {
 835         store.updateSchemaContext(schemaContext);
 836     }
 837
 838     private boolean isMetricsCaptureEnabled() {
 839         CommonConfig config = new CommonConfig(getContext().system().settings().config());
 840         return config.isMetricCaptureEnabled();
 841     }
 842
 843     @Override
 844     @VisibleForTesting
 845     public RaftActorSnapshotCohort getRaftActorSnapshotCohort() {
 846         return snapshotCohort;
 847     }
 848
 849     @Override
 850     @Nonnull
 851     protected RaftActorRecoveryCohort getRaftActorRecoveryCohort() {
 852         if (restoreFromSnapshot == null) {
 853             return ShardRecoveryCoordinator.create(store, persistenceId(), LOG);
 854         }
 855
 856         return ShardRecoveryCoordinator.forSnapshot(store, persistenceId(), LOG, restoreFromSnapshot.getSnapshot());
 857     }
 858
 859     @Override
 860     protected void onRecoveryComplete() {
 861         restoreFromSnapshot = null;
 862
 863         //notify shard manager
 864         getContext().parent().tell(new ActorInitialized(), getSelf());
 865
 866         // Being paranoid here - this method should only be called once but just in case...
 867         if (txCommitTimeoutCheckSchedule == null) {
 868             // Schedule a message to be periodically sent to check if the current in-progress
 869             // transaction should be expired and aborted.
 870             FiniteDuration period = Duration.create(transactionCommitTimeout / 3, TimeUnit.MILLISECONDS);
 871             txCommitTimeoutCheckSchedule = getContext().system().scheduler().schedule(
 872                     period, period, getSelf(),
 873                     TX_COMMIT_TIMEOUT_CHECK_MESSAGE, getContext().dispatcher(), ActorRef.noSender());
 874         }
 875     }
 876
 877     @Override
 878     protected void applyState(final ActorRef clientActor, final Identifier identifier, final Object data) {
 879         if (data instanceof Payload) {
 880             try {
 881                 store.applyReplicatedPayload(identifier, (Payload)data);
 882             } catch (DataValidationFailedException | IOException e) {
 883                 LOG.error("{}: Error applying replica {}", persistenceId(), identifier, e);
 884             }
 885         } else {
 886             LOG.error("{}: Unknown state for {} received {}", persistenceId(), identifier, data);
 887         }
 888     }
 889
 890     @Override
 891     protected void onStateChanged() {
 892         boolean isLeader = isLeader();
 893         boolean hasLeader = hasLeader();
 894         changeSupport.onLeadershipChange(isLeader, hasLeader);
 895         treeChangeSupport.onLeadershipChange(isLeader, hasLeader);
 896
 897         // If this actor is no longer the leader close all the transaction chains
 898         if (!isLeader) {
 899             if (LOG.isDebugEnabled()) {
 900                 LOG.debug(
 901                     "{}: onStateChanged: Closing all transaction chains because shard {} is no longer the leader",
 902                     persistenceId(), getId());
 903             }
 904
 905             paused = false;
 906             store.purgeLeaderState();
 907         }
 908
 909         if (hasLeader && !isIsolatedLeader()) {
 910             messageRetrySupport.retryMessages();
 911         }
 912     }
 913
 914     @Override
 915     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 916         shardMBean.incrementLeadershipChangeCount();
 917         paused = false;
 918
 919         if (!isLeader()) {
 920             if (!knownFrontends.isEmpty()) {
 921                 LOG.debug("{}: removing frontend state for {}", persistenceId(), knownFrontends.keySet());
 922                 knownFrontends = ImmutableMap.of();
 923             }
 924
 925             requestMessageAssembler.close();
 926
 927             if (!hasLeader()) {
 928                 // No leader anywhere, nothing else to do
 929                 return;
 930             }
 931
 932             // Another leader was elected. If we were the previous leader and had pending transactions, convert
 933             // them to transaction messages and send to the new leader.
 934             ActorSelection leader = getLeader();
 935             if (leader != null) {
 936                 Collection<?> messagesToForward = convertPendingTransactionsToMessages();
 937
 938                 if (!messagesToForward.isEmpty()) {
 939                     LOG.debug("{}: Forwarding {} pending transaction messages to leader {}", persistenceId(),
 940                             messagesToForward.size(), leader);
 941
 942                     for (Object message : messagesToForward) {
 943                         LOG.debug("{}: Forwarding pending transaction message {}", persistenceId(), message);
 944
 945                         leader.tell(message, self());
 946                     }
 947                 }
 948             } else {
 949                 commitCoordinator.abortPendingTransactions("The transacton was aborted due to inflight leadership "
 950                         + "change and the leader address isn't available.", this);
 951             }
 952         } else {
 953             // We have become the leader, we need to reconstruct frontend state
 954             knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 955             LOG.debug("{}: became leader with frontend state for {}", persistenceId(), knownFrontends.keySet());
 956         }
 957
 958         if (!isIsolatedLeader()) {
 959             messageRetrySupport.retryMessages();
 960         }
 961     }
 962
 963     /**
 964      * Clears all pending transactions and converts them to messages to be forwarded to a new leader.
 965      *
 966      * @return the converted messages
 967      */
 968     public Collection<?> convertPendingTransactionsToMessages() {
 969         return commitCoordinator.convertPendingTransactionsToMessages(
 970                 datastoreContext.getShardBatchedModificationCount());
 971     }
 972
 973     @Override
 974     protected void pauseLeader(final Runnable operation) {
 975         LOG.debug("{}: In pauseLeader, operation: {}", persistenceId(), operation);
 976         paused = true;
 977
 978         // Tell-based protocol can replay transaction state, so it is safe to blow it up when we are paused.
 979         knownFrontends.values().forEach(LeaderFrontendState::retire);
 980         knownFrontends = ImmutableMap.of();
 981
 982         store.setRunOnPendingTransactionsComplete(operation);
 983     }
 984
 985     @Override
 986     protected void unpauseLeader() {
 987         LOG.debug("{}: In unpauseLeader", persistenceId());
 988         paused = false;
 989
 990         store.setRunOnPendingTransactionsComplete(null);
 991
 992         // Restore tell-based protocol state as if we were becoming the leader
 993         knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 994     }
 995
 996     @Override
 997     protected OnDemandRaftState.AbstractBuilder<?, ?> newOnDemandRaftStateBuilder() {
 998         return OnDemandShardState.newBuilder().treeChangeListenerActors(treeChangeSupport.getListenerActors())
 999                 .dataChangeListenerActors(changeSupport.getListenerActors())
1000                 .commitCohortActors(store.getCohortActors());
1001     }
1002
1003     @Override
1004     public String persistenceId() {
1005         return this.name;
1006     }
1007
1008     @VisibleForTesting
1009     ShardCommitCoordinator getCommitCoordinator() {
1010         return commitCoordinator;
1011     }
1012
1013     public DatastoreContext getDatastoreContext() {
1014         return datastoreContext;
1015     }
1016
1017     @VisibleForTesting
1018     public ShardDataTree getDataStore() {
1019         return store;
1020     }
1021
1022     @VisibleForTesting
1023     ShardStats getShardMBean() {
1024         return shardMBean;
1025     }
1026
1027     public static Builder builder() {
1028         return new Builder();
1029     }
1030
1031     public abstract static class AbstractBuilder<T extends AbstractBuilder<T, S>, S extends Shard> {
1032         private final Class<S> shardClass;
1033         private ShardIdentifier id;
1034         private Map<String, String> peerAddresses = Collections.emptyMap();
1035         private DatastoreContext datastoreContext;
1036         private SchemaContextProvider schemaContextProvider;
1037         private DatastoreSnapshot.ShardSnapshot restoreFromSnapshot;
1038         private DataTree dataTree;
1039         private volatile boolean sealed;
1040
1041         protected AbstractBuilder(final Class<S> shardClass) {
1042             this.shardClass = shardClass;
1043         }
1044
1045         protected void checkSealed() {
1046             Preconditions.checkState(!sealed, "Builder isalready sealed - further modifications are not allowed");
1047         }
1048
1049         @SuppressWarnings("unchecked")
1050         private T self() {
1051             return (T) this;
1052         }
1053
1054         public T id(final ShardIdentifier newId) {
1055             checkSealed();
1056             this.id = newId;
1057             return self();
1058         }
1059
1060         public T peerAddresses(final Map<String, String> newPeerAddresses) {
1061             checkSealed();
1062             this.peerAddresses = newPeerAddresses;
1063             return self();
1064         }
1065
1066         public T datastoreContext(final DatastoreContext newDatastoreContext) {
1067             checkSealed();
1068             this.datastoreContext = newDatastoreContext;
1069             return self();
1070         }
1071
1072         public T schemaContextProvider(final SchemaContextProvider newSchemaContextProvider) {
1073             checkSealed();
1074             this.schemaContextProvider = Preconditions.checkNotNull(newSchemaContextProvider);
1075             return self();
1076         }
1077
1078         public T restoreFromSnapshot(final DatastoreSnapshot.ShardSnapshot newRestoreFromSnapshot) {
1079             checkSealed();
1080             this.restoreFromSnapshot = newRestoreFromSnapshot;
1081             return self();
1082         }
1083
1084         public T dataTree(final DataTree newDataTree) {
1085             checkSealed();
1086             this.dataTree = newDataTree;
1087             return self();
1088         }
1089
1090         public ShardIdentifier getId() {
1091             return id;
1092         }
1093
1094         public Map<String, String> getPeerAddresses() {
1095             return peerAddresses;
1096         }
1097
1098         public DatastoreContext getDatastoreContext() {
1099             return datastoreContext;
1100         }
1101
1102         public SchemaContext getSchemaContext() {
1103             return Verify.verifyNotNull(schemaContextProvider.getSchemaContext());
1104         }
1105
1106         public DatastoreSnapshot.ShardSnapshot getRestoreFromSnapshot() {
1107             return restoreFromSnapshot;
1108         }
1109
1110         public DataTree getDataTree() {
1111             return dataTree;
1112         }
1113
1114         public TreeType getTreeType() {
1115             switch (datastoreContext.getLogicalStoreType()) {
1116                 case CONFIGURATION:
1117                     return TreeType.CONFIGURATION;
1118                 case OPERATIONAL:
1119                     return TreeType.OPERATIONAL;
1120                 default:
1121                     throw new IllegalStateException("Unhandled logical store type "
1122                             + datastoreContext.getLogicalStoreType());
1123             }
1124         }
1125
1126         protected void verify() {
1127             Preconditions.checkNotNull(id, "id should not be null");
1128             Preconditions.checkNotNull(peerAddresses, "peerAddresses should not be null");
1129             Preconditions.checkNotNull(datastoreContext, "dataStoreContext should not be null");
1130             Preconditions.checkNotNull(schemaContextProvider, "schemaContextProvider should not be null");
1131         }
1132
1133         public Props props() {
1134             sealed = true;
1135             verify();
1136             return Props.create(shardClass, this);
1137         }
1138     }
1139
1140     public static class Builder extends AbstractBuilder<Builder, Shard> {
1141         Builder() {
1142             super(Shard.class);
1143         }
1144     }
1145
1146     Ticker ticker() {
1147         return Ticker.systemTicker();
1148     }
1149
1150     void scheduleNextPendingTransaction() {
1151         self().tell(RESUME_NEXT_PENDING_TRANSACTION, ActorRef.noSender());
1152     }
1153 }