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 package org.opendaylight.controller.cluster.datastore;
   9
  10 import akka.actor.ActorRef;
  11 import akka.actor.ActorSelection;
  12 import akka.actor.Cancellable;
  13 import akka.actor.ExtendedActorSystem;
  14 import akka.actor.Props;
  15 import akka.actor.Status;
  16 import akka.actor.Status.Failure;
  17 import akka.serialization.JavaSerializer;
  18 import akka.serialization.Serialization;
  19 import com.google.common.annotations.VisibleForTesting;
  20 import com.google.common.base.Optional;
  21 import com.google.common.base.Preconditions;
  22 import com.google.common.base.Ticker;
  23 import com.google.common.base.Verify;
  24 import com.google.common.collect.ImmutableList;
  25 import com.google.common.collect.ImmutableMap;
  26 import com.google.common.collect.Range;
  27 import java.io.IOException;
  28 import java.util.Arrays;
  29 import java.util.Collection;
  30 import java.util.Collections;
  31 import java.util.Map;
  32 import java.util.concurrent.TimeUnit;
  33 import org.eclipse.jdt.annotation.NonNull;
  34 import org.eclipse.jdt.annotation.Nullable;
  35 import org.opendaylight.controller.cluster.access.ABIVersion;
  36 import org.opendaylight.controller.cluster.access.commands.ConnectClientRequest;
  37 import org.opendaylight.controller.cluster.access.commands.ConnectClientSuccess;
  38 import org.opendaylight.controller.cluster.access.commands.LocalHistoryRequest;
  39 import org.opendaylight.controller.cluster.access.commands.NotLeaderException;
  40 import org.opendaylight.controller.cluster.access.commands.OutOfSequenceEnvelopeException;
  41 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  42 import org.opendaylight.controller.cluster.access.concepts.ClientIdentifier;
  43 import org.opendaylight.controller.cluster.access.concepts.FrontendIdentifier;
  44 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  45 import org.opendaylight.controller.cluster.access.concepts.Request;
  46 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  47 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  48 import org.opendaylight.controller.cluster.access.concepts.RequestSuccess;
  49 import org.opendaylight.controller.cluster.access.concepts.RetiredGenerationException;
  50 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  51 import org.opendaylight.controller.cluster.access.concepts.SliceableMessage;
  52 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  53 import org.opendaylight.controller.cluster.access.concepts.UnsupportedRequestException;
  54 import org.opendaylight.controller.cluster.common.actor.CommonConfig;
  55 import org.opendaylight.controller.cluster.common.actor.Dispatchers;
  56 import org.opendaylight.controller.cluster.common.actor.Dispatchers.DispatcherType;
  57 import org.opendaylight.controller.cluster.common.actor.MessageTracker;
  58 import org.opendaylight.controller.cluster.common.actor.MessageTracker.Error;
  59 import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
  60 import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
  61 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  62 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardDataTreeListenerInfoMXBeanImpl;
  63 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
  64 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
  65 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
  66 import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
  67 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  68 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  69 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  70 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  71 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  72 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  73 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  74 import org.opendaylight.controller.cluster.datastore.messages.GetShardDataTree;
  75 import org.opendaylight.controller.cluster.datastore.messages.MakeLeaderLocal;
  76 import org.opendaylight.controller.cluster.datastore.messages.OnDemandShardState;
  77 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
  78 import org.opendaylight.controller.cluster.datastore.messages.PersistAbortTransactionPayload;
  79 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  80 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  81 import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
  82 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
  83 import org.opendaylight.controller.cluster.datastore.persisted.AbortTransactionPayload;
  84 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot;
  85 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot.ShardSnapshot;
  86 import org.opendaylight.controller.cluster.datastore.persisted.PurgeTransactionPayload;
  87 import org.opendaylight.controller.cluster.messaging.MessageAssembler;
  88 import org.opendaylight.controller.cluster.messaging.MessageSlicer;
  89 import org.opendaylight.controller.cluster.messaging.SliceOptions;
  90 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  91 import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
  92 import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
  93 import org.opendaylight.controller.cluster.raft.LeadershipTransferFailedException;
  94 import org.opendaylight.controller.cluster.raft.RaftActor;
  95 import org.opendaylight.controller.cluster.raft.RaftActorRecoveryCohort;
  96 import org.opendaylight.controller.cluster.raft.RaftActorSnapshotCohort;
  97 import org.opendaylight.controller.cluster.raft.RaftState;
  98 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
  99 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
 100 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
 101 import org.opendaylight.controller.cluster.raft.messages.RequestLeadership;
 102 import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
 103 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 104 import org.opendaylight.yangtools.concepts.Identifier;
 105 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
 106 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
 107 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 108 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 109 import org.opendaylight.yangtools.yang.model.api.SchemaContextProvider;
 110 import scala.concurrent.duration.FiniteDuration;
 111
 112 /**
 113  * A Shard represents a portion of the logical data tree.
 114  *
 115  * <p>
 116  * Our Shard uses InMemoryDataTree as it's internal representation and delegates all requests it
 117  */
 118 public class Shard extends RaftActor {
 119
 120     @VisibleForTesting
 121     static final Object TX_COMMIT_TIMEOUT_CHECK_MESSAGE = new Object() {
 122         @Override
 123         public String toString() {
 124             return "txCommitTimeoutCheck";
 125         }
 126     };
 127
 128     @VisibleForTesting
 129     static final Object GET_SHARD_MBEAN_MESSAGE = new Object() {
 130         @Override
 131         public String toString() {
 132             return "getShardMBeanMessage";
 133         }
 134     };
 135
 136     static final Object RESUME_NEXT_PENDING_TRANSACTION = new Object() {
 137         @Override
 138         public String toString() {
 139             return "resumeNextPendingTransaction";
 140         }
 141     };
 142
 143     // FIXME: shard names should be encapsulated in their own class and this should be exposed as a constant.
 144     public static final String DEFAULT_NAME = "default";
 145
 146     private static final Collection<ABIVersion> SUPPORTED_ABIVERSIONS;
 147
 148     static {
 149         final ABIVersion[] values = ABIVersion.values();
 150         final ABIVersion[] real = Arrays.copyOfRange(values, 1, values.length - 1);
 151         SUPPORTED_ABIVERSIONS = ImmutableList.copyOf(real).reverse();
 152     }
 153
 154     // FIXME: make this a dynamic property based on mailbox size and maximum number of clients
 155     private static final int CLIENT_MAX_MESSAGES = 1000;
 156
 157     // The state of this Shard
 158     private final ShardDataTree store;
 159
 160     /// The name of this shard
 161     private final String name;
 162
 163     private final String shardName;
 164
 165     private final ShardStats shardMBean;
 166
 167     private final ShardDataTreeListenerInfoMXBeanImpl listenerInfoMXBean;
 168
 169     private DatastoreContext datastoreContext;
 170
 171     private final ShardCommitCoordinator commitCoordinator;
 172
 173     private long transactionCommitTimeout;
 174
 175     private Cancellable txCommitTimeoutCheckSchedule;
 176
 177     private final Optional<ActorRef> roleChangeNotifier;
 178
 179     private final MessageTracker appendEntriesReplyTracker;
 180
 181     private final ShardTransactionActorFactory transactionActorFactory;
 182
 183     private final ShardSnapshotCohort snapshotCohort;
 184
 185     private final DataTreeChangeListenerSupport treeChangeSupport = new DataTreeChangeListenerSupport(this);
 186
 187     private ShardSnapshot restoreFromSnapshot;
 188
 189     private final ShardTransactionMessageRetrySupport messageRetrySupport;
 190
 191     private final FrontendMetadata frontendMetadata;
 192     private Map<FrontendIdentifier, LeaderFrontendState> knownFrontends = ImmutableMap.of();
 193     private boolean paused;
 194
 195     private final MessageSlicer responseMessageSlicer;
 196     private final Dispatchers dispatchers;
 197
 198     private final MessageAssembler requestMessageAssembler;
 199
 200     protected Shard(final AbstractBuilder<?, ?> builder) {
 201         super(builder.getId().toString(), builder.getPeerAddresses(),
 202                 Optional.of(builder.getDatastoreContext().getShardRaftConfig()), DataStoreVersions.CURRENT_VERSION);
 203
 204         this.name = builder.getId().toString();
 205         this.shardName = builder.getId().getShardName();
 206         this.datastoreContext = builder.getDatastoreContext();
 207         this.restoreFromSnapshot = builder.getRestoreFromSnapshot();
 208         this.frontendMetadata = new FrontendMetadata(name);
 209
 210         setPersistence(datastoreContext.isPersistent());
 211
 212         LOG.info("Shard created : {}, persistent : {}", name, datastoreContext.isPersistent());
 213
 214         ShardDataTreeChangeListenerPublisherActorProxy treeChangeListenerPublisher =
 215                 new ShardDataTreeChangeListenerPublisherActorProxy(getContext(), name + "-DTCL-publisher", name);
 216         if (builder.getDataTree() != null) {
 217             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getDataTree(),
 218                     treeChangeListenerPublisher, name, frontendMetadata);
 219         } else {
 220             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getTreeType(),
 221                     builder.getDatastoreContext().getStoreRoot(), treeChangeListenerPublisher, name, frontendMetadata);
 222         }
 223
 224         shardMBean = ShardMBeanFactory.getShardStatsMBean(name, datastoreContext.getDataStoreMXBeanType(), this);
 225
 226         if (isMetricsCaptureEnabled()) {
 227             getContext().become(new MeteringBehavior(this));
 228         }
 229
 230         commitCoordinator = new ShardCommitCoordinator(store, LOG, this.name);
 231
 232         setTransactionCommitTimeout();
 233
 234         // create a notifier actor for each cluster member
 235         roleChangeNotifier = createRoleChangeNotifier(name);
 236
 237         appendEntriesReplyTracker = new MessageTracker(AppendEntriesReply.class,
 238                 getRaftActorContext().getConfigParams().getIsolatedCheckIntervalInMillis());
 239
 240         dispatchers = new Dispatchers(context().system().dispatchers());
 241         transactionActorFactory = new ShardTransactionActorFactory(store, datastoreContext,
 242             dispatchers.getDispatcherPath(Dispatchers.DispatcherType.Transaction),
 243                 self(), getContext(), shardMBean, builder.getId().getShardName());
 244
 245         snapshotCohort = ShardSnapshotCohort.create(getContext(), builder.getId().getMemberName(), store, LOG,
 246             this.name);
 247
 248         messageRetrySupport = new ShardTransactionMessageRetrySupport(this);
 249
 250         responseMessageSlicer = MessageSlicer.builder().logContext(this.name)
 251                 .messageSliceSize(datastoreContext.getMaximumMessageSliceSize())
 252                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 253                 .expireStateAfterInactivity(2, TimeUnit.MINUTES).build();
 254
 255         requestMessageAssembler = MessageAssembler.builder().logContext(this.name)
 256                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 257                 .assembledMessageCallback((message, sender) -> self().tell(message, sender))
 258                 .expireStateAfterInactivity(datastoreContext.getRequestTimeout(), TimeUnit.NANOSECONDS).build();
 259
 260         listenerInfoMXBean = new ShardDataTreeListenerInfoMXBeanImpl(name, datastoreContext.getDataStoreMXBeanType(),
 261                 self());
 262         listenerInfoMXBean.register();
 263     }
 264
 265     private void setTransactionCommitTimeout() {
 266         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
 267                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS) / 2;
 268     }
 269
 270     private Optional<ActorRef> createRoleChangeNotifier(final String shardId) {
 271         ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
 272             RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
 273         return Optional.of(shardRoleChangeNotifier);
 274     }
 275
 276     @Override
 277     public void postStop() {
 278         LOG.info("Stopping Shard {}", persistenceId());
 279
 280         super.postStop();
 281
 282         messageRetrySupport.close();
 283
 284         if (txCommitTimeoutCheckSchedule != null) {
 285             txCommitTimeoutCheckSchedule.cancel();
 286         }
 287
 288         commitCoordinator.abortPendingTransactions("Transaction aborted due to shutdown.", this);
 289
 290         shardMBean.unregisterMBean();
 291         listenerInfoMXBean.unregister();
 292     }
 293
 294     @Override
 295     protected void handleRecover(final Object message) {
 296         LOG.debug("{}: onReceiveRecover: Received message {} from {}", persistenceId(), message.getClass(),
 297             getSender());
 298
 299         super.handleRecover(message);
 300         if (LOG.isTraceEnabled()) {
 301             appendEntriesReplyTracker.begin();
 302         }
 303     }
 304
 305     @Override
 306     protected void handleNonRaftCommand(final Object message) {
 307         try (MessageTracker.Context context = appendEntriesReplyTracker.received(message)) {
 308             final Optional<Error> maybeError = context.error();
 309             if (maybeError.isPresent()) {
 310                 LOG.trace("{} : AppendEntriesReply failed to arrive at the expected interval {}", persistenceId(),
 311                     maybeError.get());
 312             }
 313
 314             store.resetTransactionBatch();
 315
 316             if (message instanceof RequestEnvelope) {
 317                 handleRequestEnvelope((RequestEnvelope)message);
 318             } else if (MessageAssembler.isHandledMessage(message)) {
 319                 handleRequestAssemblerMessage(message);
 320             } else if (message instanceof ConnectClientRequest) {
 321                 handleConnectClient((ConnectClientRequest)message);
 322             } else if (CreateTransaction.isSerializedType(message)) {
 323                 handleCreateTransaction(message);
 324             } else if (message instanceof BatchedModifications) {
 325                 handleBatchedModifications((BatchedModifications)message);
 326             } else if (message instanceof ForwardedReadyTransaction) {
 327                 handleForwardedReadyTransaction((ForwardedReadyTransaction) message);
 328             } else if (message instanceof ReadyLocalTransaction) {
 329                 handleReadyLocalTransaction((ReadyLocalTransaction)message);
 330             } else if (CanCommitTransaction.isSerializedType(message)) {
 331                 handleCanCommitTransaction(CanCommitTransaction.fromSerializable(message));
 332             } else if (CommitTransaction.isSerializedType(message)) {
 333                 handleCommitTransaction(CommitTransaction.fromSerializable(message));
 334             } else if (AbortTransaction.isSerializedType(message)) {
 335                 handleAbortTransaction(AbortTransaction.fromSerializable(message));
 336             } else if (CloseTransactionChain.isSerializedType(message)) {
 337                 closeTransactionChain(CloseTransactionChain.fromSerializable(message));
 338             } else if (message instanceof RegisterDataTreeChangeListener) {
 339                 treeChangeSupport.onMessage((RegisterDataTreeChangeListener) message, isLeader(), hasLeader());
 340             } else if (message instanceof UpdateSchemaContext) {
 341                 updateSchemaContext((UpdateSchemaContext) message);
 342             } else if (message instanceof PeerAddressResolved) {
 343                 PeerAddressResolved resolved = (PeerAddressResolved) message;
 344                 setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
 345             } else if (TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
 346                 commitTimeoutCheck();
 347             } else if (message instanceof DatastoreContext) {
 348                 onDatastoreContext((DatastoreContext)message);
 349             } else if (message instanceof RegisterRoleChangeListener) {
 350                 roleChangeNotifier.get().forward(message, context());
 351             } else if (message instanceof FollowerInitialSyncUpStatus) {
 352                 shardMBean.setFollowerInitialSyncStatus(((FollowerInitialSyncUpStatus) message).isInitialSyncDone());
 353                 context().parent().tell(message, self());
 354             } else if (GET_SHARD_MBEAN_MESSAGE.equals(message)) {
 355                 sender().tell(getShardMBean(), self());
 356             } else if (message instanceof GetShardDataTree) {
 357                 sender().tell(store.getDataTree(), self());
 358             } else if (message instanceof ServerRemoved) {
 359                 context().parent().forward(message, context());
 360             } else if (ShardTransactionMessageRetrySupport.TIMER_MESSAGE_CLASS.isInstance(message)) {
 361                 messageRetrySupport.onTimerMessage(message);
 362             } else if (message instanceof DataTreeCohortActorRegistry.CohortRegistryCommand) {
 363                 store.processCohortRegistryCommand(getSender(),
 364                         (DataTreeCohortActorRegistry.CohortRegistryCommand) message);
 365             } else if (message instanceof PersistAbortTransactionPayload) {
 366                 final TransactionIdentifier txId = ((PersistAbortTransactionPayload) message).getTransactionId();
 367                 persistPayload(txId, AbortTransactionPayload.create(txId,
 368                     datastoreContext.getInitialPayloadSerializedBufferCapacity()), true);
 369                 persistPayload(txId, PurgeTransactionPayload.create(txId,
 370                     datastoreContext.getInitialPayloadSerializedBufferCapacity()), false);
 371             } else if (message instanceof MakeLeaderLocal) {
 372                 onMakeLeaderLocal();
 373             } else if (RESUME_NEXT_PENDING_TRANSACTION.equals(message)) {
 374                 store.resumeNextPendingTransaction();
 375             } else if (!responseMessageSlicer.handleMessage(message)) {
 376                 super.handleNonRaftCommand(message);
 377             }
 378         }
 379     }
 380
 381     private void handleRequestAssemblerMessage(final Object message) {
 382         dispatchers.getDispatcher(DispatcherType.Serialization).execute(() -> {
 383             JavaSerializer.currentSystem().value_$eq((ExtendedActorSystem) context().system());
 384             requestMessageAssembler.handleMessage(message, self());
 385         });
 386     }
 387
 388     @SuppressWarnings("checkstyle:IllegalCatch")
 389     private void handleRequestEnvelope(final RequestEnvelope envelope) {
 390         final long now = ticker().read();
 391         try {
 392             final RequestSuccess<?, ?> success = handleRequest(envelope, now);
 393             if (success != null) {
 394                 final long executionTimeNanos = ticker().read() - now;
 395                 if (success instanceof SliceableMessage) {
 396                     dispatchers.getDispatcher(DispatcherType.Serialization).execute(() ->
 397                         responseMessageSlicer.slice(SliceOptions.builder().identifier(success.getTarget())
 398                             .message(envelope.newSuccessEnvelope(success, executionTimeNanos))
 399                             .sendTo(envelope.getMessage().getReplyTo()).replyTo(self())
 400                             .onFailureCallback(t -> LOG.warn("Error slicing response {}", success, t)).build()));
 401                 } else {
 402                     envelope.sendSuccess(success, executionTimeNanos);
 403                 }
 404             }
 405         } catch (RequestException e) {
 406             LOG.debug("{}: request {} failed", persistenceId(), envelope, e);
 407             envelope.sendFailure(e, ticker().read() - now);
 408         } catch (Exception e) {
 409             LOG.debug("{}: request {} caused failure", persistenceId(), envelope, e);
 410             envelope.sendFailure(new RuntimeRequestException("Request failed to process", e),
 411                 ticker().read() - now);
 412         }
 413     }
 414
 415     private void commitTimeoutCheck() {
 416         store.checkForExpiredTransactions(transactionCommitTimeout, this::updateAccess);
 417         commitCoordinator.checkForExpiredTransactions(transactionCommitTimeout, this);
 418         requestMessageAssembler.checkExpiredAssembledMessageState();
 419     }
 420
 421     private Optional<Long> updateAccess(final SimpleShardDataTreeCohort cohort) {
 422         final FrontendIdentifier frontend = cohort.getIdentifier().getHistoryId().getClientId().getFrontendId();
 423         final LeaderFrontendState state = knownFrontends.get(frontend);
 424         if (state == null) {
 425             // Not tell-based protocol, do nothing
 426             return Optional.absent();
 427         }
 428
 429         if (isIsolatedLeader()) {
 430             // We are isolated and no new request can come through until we emerge from it. We are still updating
 431             // liveness of frontend when we see it attempting to communicate. Use the last access timer.
 432             return Optional.of(state.getLastSeenTicks());
 433         }
 434
 435         // If this frontend has freshly connected, give it some time to catch up before killing its transactions.
 436         return Optional.of(state.getLastConnectTicks());
 437     }
 438
 439     private void onMakeLeaderLocal() {
 440         LOG.debug("{}: onMakeLeaderLocal received", persistenceId());
 441         if (isLeader()) {
 442             getSender().tell(new Status.Success(null), getSelf());
 443             return;
 444         }
 445
 446         final ActorSelection leader = getLeader();
 447
 448         if (leader == null) {
 449             // Leader is not present. The cluster is most likely trying to
 450             // elect a leader and we should let that run its normal course
 451
 452             // TODO we can wait for the election to complete and retry the
 453             // request. We can also let the caller retry by sending a flag
 454             // in the response indicating the request is "reTryable".
 455             getSender().tell(new Failure(
 456                     new LeadershipTransferFailedException("We cannot initiate leadership transfer to local node. "
 457                             + "Currently there is no leader for " + persistenceId())),
 458                     getSelf());
 459             return;
 460         }
 461
 462         leader.tell(new RequestLeadership(getId(), getSender()), getSelf());
 463     }
 464
 465     // Acquire our frontend tracking handle and verify generation matches
 466     private @Nullable LeaderFrontendState findFrontend(final ClientIdentifier clientId) throws RequestException {
 467         final LeaderFrontendState existing = knownFrontends.get(clientId.getFrontendId());
 468         if (existing != null) {
 469             final int cmp = Long.compareUnsigned(existing.getIdentifier().getGeneration(), clientId.getGeneration());
 470             if (cmp == 0) {
 471                 existing.touch();
 472                 return existing;
 473             }
 474             if (cmp > 0) {
 475                 LOG.debug("{}: rejecting request from outdated client {}", persistenceId(), clientId);
 476                 throw new RetiredGenerationException(clientId.getGeneration(),
 477                     existing.getIdentifier().getGeneration());
 478             }
 479
 480             LOG.info("{}: retiring state {}, outdated by request from client {}", persistenceId(), existing, clientId);
 481             existing.retire();
 482             knownFrontends.remove(clientId.getFrontendId());
 483         } else {
 484             LOG.debug("{}: client {} is not yet known", persistenceId(), clientId);
 485         }
 486
 487         return null;
 488     }
 489
 490     private LeaderFrontendState getFrontend(final ClientIdentifier clientId) throws RequestException {
 491         final LeaderFrontendState ret = findFrontend(clientId);
 492         if (ret != null) {
 493             return ret;
 494         }
 495
 496         // TODO: a dedicated exception would be better, but this is technically true, too
 497         throw new OutOfSequenceEnvelopeException(0);
 498     }
 499
 500     private static @NonNull ABIVersion selectVersion(final ConnectClientRequest message) {
 501         final Range<ABIVersion> clientRange = Range.closed(message.getMinVersion(), message.getMaxVersion());
 502         for (ABIVersion v : SUPPORTED_ABIVERSIONS) {
 503             if (clientRange.contains(v)) {
 504                 return v;
 505             }
 506         }
 507
 508         throw new IllegalArgumentException(String.format(
 509             "No common version between backend versions %s and client versions %s", SUPPORTED_ABIVERSIONS,
 510             clientRange));
 511     }
 512
 513     @SuppressWarnings("checkstyle:IllegalCatch")
 514     private void handleConnectClient(final ConnectClientRequest message) {
 515         try {
 516             final ClientIdentifier clientId = message.getTarget();
 517             final LeaderFrontendState existing = findFrontend(clientId);
 518             if (existing != null) {
 519                 existing.touch();
 520             }
 521
 522             if (!isLeader() || !isLeaderActive()) {
 523                 LOG.info("{}: not currently leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 524                                 + "isLeadershipTransferInProgress: {}.",
 525                         persistenceId(), message, isLeader(), isLeaderActive(), isLeadershipTransferInProgress());
 526                 throw new NotLeaderException(getSelf());
 527             }
 528
 529             final ABIVersion selectedVersion = selectVersion(message);
 530             final LeaderFrontendState frontend;
 531             if (existing == null) {
 532                 frontend = new LeaderFrontendState(persistenceId(), clientId, store);
 533                 knownFrontends.put(clientId.getFrontendId(), frontend);
 534                 LOG.debug("{}: created state {} for client {}", persistenceId(), frontend, clientId);
 535             } else {
 536                 frontend = existing;
 537             }
 538
 539             frontend.reconnect();
 540             message.getReplyTo().tell(new ConnectClientSuccess(message.getTarget(), message.getSequence(), getSelf(),
 541                 ImmutableList.of(), store.getDataTree(), CLIENT_MAX_MESSAGES).toVersion(selectedVersion),
 542                 ActorRef.noSender());
 543         } catch (RequestException | RuntimeException e) {
 544             message.getReplyTo().tell(new Failure(e), ActorRef.noSender());
 545         }
 546     }
 547
 548     private @Nullable RequestSuccess<?, ?> handleRequest(final RequestEnvelope envelope, final long now)
 549             throws RequestException {
 550         // We are not the leader, hence we want to fail-fast.
 551         if (!isLeader() || paused || !isLeaderActive()) {
 552             LOG.debug("{}: not currently active leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 553                             + "isLeadershipTransferInProgress: {}, paused: {}",
 554                     persistenceId(), envelope, isLeader(), isLeaderActive(), isLeadershipTransferInProgress(), paused);
 555             throw new NotLeaderException(getSelf());
 556         }
 557
 558         final Request<?, ?> request = envelope.getMessage();
 559         if (request instanceof TransactionRequest) {
 560             final TransactionRequest<?> txReq = (TransactionRequest<?>)request;
 561             final ClientIdentifier clientId = txReq.getTarget().getHistoryId().getClientId();
 562             return getFrontend(clientId).handleTransactionRequest(txReq, envelope, now);
 563         } else if (request instanceof LocalHistoryRequest) {
 564             final LocalHistoryRequest<?> lhReq = (LocalHistoryRequest<?>)request;
 565             final ClientIdentifier clientId = lhReq.getTarget().getClientId();
 566             return getFrontend(clientId).handleLocalHistoryRequest(lhReq, envelope, now);
 567         } else {
 568             LOG.warn("{}: rejecting unsupported request {}", persistenceId(), request);
 569             throw new UnsupportedRequestException(request);
 570         }
 571     }
 572
 573     private boolean hasLeader() {
 574         return getLeaderId() != null;
 575     }
 576
 577     public int getPendingTxCommitQueueSize() {
 578         return store.getQueueSize();
 579     }
 580
 581     public int getCohortCacheSize() {
 582         return commitCoordinator.getCohortCacheSize();
 583     }
 584
 585     @Override
 586     protected Optional<ActorRef> getRoleChangeNotifier() {
 587         return roleChangeNotifier;
 588     }
 589
 590     String getShardName() {
 591         return shardName;
 592     }
 593
 594     @Override
 595     protected LeaderStateChanged newLeaderStateChanged(final String memberId, final String leaderId,
 596             final short leaderPayloadVersion) {
 597         return isLeader() ? new ShardLeaderStateChanged(memberId, leaderId, store.getDataTree(), leaderPayloadVersion)
 598                 : new ShardLeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 599     }
 600
 601     protected void onDatastoreContext(final DatastoreContext context) {
 602         datastoreContext = context;
 603
 604         setTransactionCommitTimeout();
 605
 606         setPersistence(datastoreContext.isPersistent());
 607
 608         updateConfigParams(datastoreContext.getShardRaftConfig());
 609     }
 610
 611     // applyState() will be invoked once consensus is reached on the payload
 612     void persistPayload(final Identifier id, final Payload payload, final boolean batchHint) {
 613         boolean canSkipPayload = !hasFollowers() && !persistence().isRecoveryApplicable();
 614         if (canSkipPayload) {
 615             applyState(self(), id, payload);
 616         } else {
 617             // We are faking the sender
 618             persistData(self(), id, payload, batchHint);
 619         }
 620     }
 621
 622     private void handleCommitTransaction(final CommitTransaction commit) {
 623         if (isLeader()) {
 624             commitCoordinator.handleCommit(commit.getTransactionId(), getSender(), this);
 625         } else {
 626             ActorSelection leader = getLeader();
 627             if (leader == null) {
 628                 messageRetrySupport.addMessageToRetry(commit, getSender(),
 629                         "Could not commit transaction " + commit.getTransactionId());
 630             } else {
 631                 LOG.debug("{}: Forwarding CommitTransaction to leader {}", persistenceId(), leader);
 632                 leader.forward(commit, getContext());
 633             }
 634         }
 635     }
 636
 637     private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
 638         LOG.debug("{}: Can committing transaction {}", persistenceId(), canCommit.getTransactionId());
 639
 640         if (isLeader()) {
 641             commitCoordinator.handleCanCommit(canCommit.getTransactionId(), getSender(), this);
 642         } else {
 643             ActorSelection leader = getLeader();
 644             if (leader == null) {
 645                 messageRetrySupport.addMessageToRetry(canCommit, getSender(),
 646                         "Could not canCommit transaction " + canCommit.getTransactionId());
 647             } else {
 648                 LOG.debug("{}: Forwarding CanCommitTransaction to leader {}", persistenceId(), leader);
 649                 leader.forward(canCommit, getContext());
 650             }
 651         }
 652     }
 653
 654     @SuppressWarnings("checkstyle:IllegalCatch")
 655     protected void handleBatchedModificationsLocal(final BatchedModifications batched, final ActorRef sender) {
 656         try {
 657             commitCoordinator.handleBatchedModifications(batched, sender, this);
 658         } catch (Exception e) {
 659             LOG.error("{}: Error handling BatchedModifications for Tx {}", persistenceId(),
 660                     batched.getTransactionId(), e);
 661             sender.tell(new Failure(e), getSelf());
 662         }
 663     }
 664
 665     private void handleBatchedModifications(final BatchedModifications batched) {
 666         // This message is sent to prepare the modifications transaction directly on the Shard as an
 667         // optimization to avoid the extra overhead of a separate ShardTransaction actor. On the last
 668         // BatchedModifications message, the caller sets the ready flag in the message indicating
 669         // modifications are complete. The reply contains the cohort actor path (this actor) for the caller
 670         // to initiate the 3-phase commit. This also avoids the overhead of sending an additional
 671         // ReadyTransaction message.
 672
 673         // If we're not the leader then forward to the leader. This is a safety measure - we shouldn't
 674         // normally get here if we're not the leader as the front-end (TransactionProxy) should determine
 675         // the primary/leader shard. However with timing and caching on the front-end, there's a small
 676         // window where it could have a stale leader during leadership transitions.
 677         //
 678         boolean isLeaderActive = isLeaderActive();
 679         if (isLeader() && isLeaderActive) {
 680             handleBatchedModificationsLocal(batched, getSender());
 681         } else {
 682             ActorSelection leader = getLeader();
 683             if (!isLeaderActive || leader == null) {
 684                 messageRetrySupport.addMessageToRetry(batched, getSender(),
 685                         "Could not process BatchedModifications " + batched.getTransactionId());
 686             } else {
 687                 // If this is not the first batch and leadership changed in between batched messages,
 688                 // we need to reconstruct previous BatchedModifications from the transaction
 689                 // DataTreeModification, honoring the max batched modification count, and forward all the
 690                 // previous BatchedModifications to the new leader.
 691                 Collection<BatchedModifications> newModifications = commitCoordinator
 692                         .createForwardedBatchedModifications(batched,
 693                                 datastoreContext.getShardBatchedModificationCount());
 694
 695                 LOG.debug("{}: Forwarding {} BatchedModifications to leader {}", persistenceId(),
 696                         newModifications.size(), leader);
 697
 698                 for (BatchedModifications bm : newModifications) {
 699                     leader.forward(bm, getContext());
 700                 }
 701             }
 702         }
 703     }
 704
 705     private boolean failIfIsolatedLeader(final ActorRef sender) {
 706         if (isIsolatedLeader()) {
 707             sender.tell(new Failure(new NoShardLeaderException(String.format(
 708                     "Shard %s was the leader but has lost contact with all of its followers. Either all"
 709                     + " other follower nodes are down or this node is isolated by a network partition.",
 710                     persistenceId()))), getSelf());
 711             return true;
 712         }
 713
 714         return false;
 715     }
 716
 717     protected boolean isIsolatedLeader() {
 718         return getRaftState() == RaftState.IsolatedLeader;
 719     }
 720
 721     @SuppressWarnings("checkstyle:IllegalCatch")
 722     private void handleReadyLocalTransaction(final ReadyLocalTransaction message) {
 723         LOG.debug("{}: handleReadyLocalTransaction for {}", persistenceId(), message.getTransactionId());
 724
 725         boolean isLeaderActive = isLeaderActive();
 726         if (isLeader() && isLeaderActive) {
 727             try {
 728                 commitCoordinator.handleReadyLocalTransaction(message, getSender(), this);
 729             } catch (Exception e) {
 730                 LOG.error("{}: Error handling ReadyLocalTransaction for Tx {}", persistenceId(),
 731                         message.getTransactionId(), e);
 732                 getSender().tell(new Failure(e), getSelf());
 733             }
 734         } else {
 735             ActorSelection leader = getLeader();
 736             if (!isLeaderActive || leader == null) {
 737                 messageRetrySupport.addMessageToRetry(message, getSender(),
 738                         "Could not process ready local transaction " + message.getTransactionId());
 739             } else {
 740                 LOG.debug("{}: Forwarding ReadyLocalTransaction to leader {}", persistenceId(), leader);
 741                 message.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 742                 leader.forward(message, getContext());
 743             }
 744         }
 745     }
 746
 747     private void handleForwardedReadyTransaction(final ForwardedReadyTransaction forwardedReady) {
 748         LOG.debug("{}: handleForwardedReadyTransaction for {}", persistenceId(), forwardedReady.getTransactionId());
 749
 750         boolean isLeaderActive = isLeaderActive();
 751         if (isLeader() && isLeaderActive) {
 752             commitCoordinator.handleForwardedReadyTransaction(forwardedReady, getSender(), this);
 753         } else {
 754             ActorSelection leader = getLeader();
 755             if (!isLeaderActive || leader == null) {
 756                 messageRetrySupport.addMessageToRetry(forwardedReady, getSender(),
 757                         "Could not process forwarded ready transaction " + forwardedReady.getTransactionId());
 758             } else {
 759                 LOG.debug("{}: Forwarding ForwardedReadyTransaction to leader {}", persistenceId(), leader);
 760
 761                 ReadyLocalTransaction readyLocal = new ReadyLocalTransaction(forwardedReady.getTransactionId(),
 762                         forwardedReady.getTransaction().getSnapshot(), forwardedReady.isDoImmediateCommit(),
 763                         forwardedReady.getParticipatingShardNames());
 764                 readyLocal.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 765                 leader.forward(readyLocal, getContext());
 766             }
 767         }
 768     }
 769
 770     private void handleAbortTransaction(final AbortTransaction abort) {
 771         doAbortTransaction(abort.getTransactionId(), getSender());
 772     }
 773
 774     void doAbortTransaction(final Identifier transactionID, final ActorRef sender) {
 775         commitCoordinator.handleAbort(transactionID, sender, this);
 776     }
 777
 778     private void handleCreateTransaction(final Object message) {
 779         if (isLeader()) {
 780             createTransaction(CreateTransaction.fromSerializable(message));
 781         } else if (getLeader() != null) {
 782             getLeader().forward(message, getContext());
 783         } else {
 784             getSender().tell(new Failure(new NoShardLeaderException(
 785                     "Could not create a shard transaction", persistenceId())), getSelf());
 786         }
 787     }
 788
 789     private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
 790         if (isLeader()) {
 791             final LocalHistoryIdentifier id = closeTransactionChain.getIdentifier();
 792             // FIXME: CONTROLLER-1628: stage purge once no transactions are present
 793             store.closeTransactionChain(id, null);
 794             store.purgeTransactionChain(id, null);
 795         } else if (getLeader() != null) {
 796             getLeader().forward(closeTransactionChain, getContext());
 797         } else {
 798             LOG.warn("{}: Could not close transaction {}", persistenceId(), closeTransactionChain.getIdentifier());
 799         }
 800     }
 801
 802     @SuppressWarnings("checkstyle:IllegalCatch")
 803     private void createTransaction(final CreateTransaction createTransaction) {
 804         try {
 805             if (TransactionType.fromInt(createTransaction.getTransactionType()) != TransactionType.READ_ONLY
 806                     && failIfIsolatedLeader(getSender())) {
 807                 return;
 808             }
 809
 810             ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
 811                 createTransaction.getTransactionId());
 812
 813             getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
 814                     createTransaction.getTransactionId(), createTransaction.getVersion()).toSerializable(), getSelf());
 815         } catch (Exception e) {
 816             getSender().tell(new Failure(e), getSelf());
 817         }
 818     }
 819
 820     private ActorRef createTransaction(final int transactionType, final TransactionIdentifier transactionId) {
 821         LOG.debug("{}: Creating transaction : {} ", persistenceId(), transactionId);
 822         return transactionActorFactory.newShardTransaction(TransactionType.fromInt(transactionType),
 823             transactionId);
 824     }
 825
 826     private void updateSchemaContext(final UpdateSchemaContext message) {
 827         updateSchemaContext(message.getSchemaContext());
 828     }
 829
 830     @VisibleForTesting
 831     void updateSchemaContext(final SchemaContext schemaContext) {
 832         store.updateSchemaContext(schemaContext);
 833     }
 834
 835     private boolean isMetricsCaptureEnabled() {
 836         CommonConfig config = new CommonConfig(getContext().system().settings().config());
 837         return config.isMetricCaptureEnabled();
 838     }
 839
 840     @Override
 841     @VisibleForTesting
 842     public RaftActorSnapshotCohort getRaftActorSnapshotCohort() {
 843         return snapshotCohort;
 844     }
 845
 846     @Override
 847     protected RaftActorRecoveryCohort getRaftActorRecoveryCohort() {
 848         if (restoreFromSnapshot == null) {
 849             return ShardRecoveryCoordinator.create(store, persistenceId(), LOG);
 850         }
 851
 852         return ShardRecoveryCoordinator.forSnapshot(store, persistenceId(), LOG, restoreFromSnapshot.getSnapshot());
 853     }
 854
 855     @Override
 856     protected void onRecoveryComplete() {
 857         restoreFromSnapshot = null;
 858
 859         //notify shard manager
 860         getContext().parent().tell(new ActorInitialized(), getSelf());
 861
 862         // Being paranoid here - this method should only be called once but just in case...
 863         if (txCommitTimeoutCheckSchedule == null) {
 864             // Schedule a message to be periodically sent to check if the current in-progress
 865             // transaction should be expired and aborted.
 866             FiniteDuration period = FiniteDuration.create(transactionCommitTimeout / 3, TimeUnit.MILLISECONDS);
 867             txCommitTimeoutCheckSchedule = getContext().system().scheduler().schedule(
 868                     period, period, getSelf(),
 869                     TX_COMMIT_TIMEOUT_CHECK_MESSAGE, getContext().dispatcher(), ActorRef.noSender());
 870         }
 871     }
 872
 873     @Override
 874     protected void applyState(final ActorRef clientActor, final Identifier identifier, final Object data) {
 875         if (data instanceof Payload) {
 876             try {
 877                 store.applyReplicatedPayload(identifier, (Payload)data);
 878             } catch (DataValidationFailedException | IOException e) {
 879                 LOG.error("{}: Error applying replica {}", persistenceId(), identifier, e);
 880             }
 881         } else {
 882             LOG.error("{}: Unknown state for {} received {}", persistenceId(), identifier, data);
 883         }
 884     }
 885
 886     @Override
 887     protected void onStateChanged() {
 888         boolean isLeader = isLeader();
 889         boolean hasLeader = hasLeader();
 890         treeChangeSupport.onLeadershipChange(isLeader, hasLeader);
 891
 892         // If this actor is no longer the leader close all the transaction chains
 893         if (!isLeader) {
 894             if (LOG.isDebugEnabled()) {
 895                 LOG.debug(
 896                     "{}: onStateChanged: Closing all transaction chains because shard {} is no longer the leader",
 897                     persistenceId(), getId());
 898             }
 899
 900             paused = false;
 901             store.purgeLeaderState();
 902         }
 903
 904         if (hasLeader && !isIsolatedLeader()) {
 905             messageRetrySupport.retryMessages();
 906         }
 907     }
 908
 909     @Override
 910     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 911         shardMBean.incrementLeadershipChangeCount();
 912         paused = false;
 913
 914         if (!isLeader()) {
 915             if (!knownFrontends.isEmpty()) {
 916                 LOG.debug("{}: removing frontend state for {}", persistenceId(), knownFrontends.keySet());
 917                 knownFrontends = ImmutableMap.of();
 918             }
 919
 920             requestMessageAssembler.close();
 921
 922             if (!hasLeader()) {
 923                 // No leader anywhere, nothing else to do
 924                 return;
 925             }
 926
 927             // Another leader was elected. If we were the previous leader and had pending transactions, convert
 928             // them to transaction messages and send to the new leader.
 929             ActorSelection leader = getLeader();
 930             if (leader != null) {
 931                 Collection<?> messagesToForward = convertPendingTransactionsToMessages();
 932
 933                 if (!messagesToForward.isEmpty()) {
 934                     LOG.debug("{}: Forwarding {} pending transaction messages to leader {}", persistenceId(),
 935                             messagesToForward.size(), leader);
 936
 937                     for (Object message : messagesToForward) {
 938                         LOG.debug("{}: Forwarding pending transaction message {}", persistenceId(), message);
 939
 940                         leader.tell(message, self());
 941                     }
 942                 }
 943             } else {
 944                 commitCoordinator.abortPendingTransactions("The transacton was aborted due to inflight leadership "
 945                         + "change and the leader address isn't available.", this);
 946             }
 947         } else {
 948             // We have become the leader, we need to reconstruct frontend state
 949             knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 950             LOG.debug("{}: became leader with frontend state for {}", persistenceId(), knownFrontends.keySet());
 951         }
 952
 953         if (!isIsolatedLeader()) {
 954             messageRetrySupport.retryMessages();
 955         }
 956     }
 957
 958     /**
 959      * Clears all pending transactions and converts them to messages to be forwarded to a new leader.
 960      *
 961      * @return the converted messages
 962      */
 963     public Collection<?> convertPendingTransactionsToMessages() {
 964         return commitCoordinator.convertPendingTransactionsToMessages(
 965                 datastoreContext.getShardBatchedModificationCount());
 966     }
 967
 968     @Override
 969     protected void pauseLeader(final Runnable operation) {
 970         LOG.debug("{}: In pauseLeader, operation: {}", persistenceId(), operation);
 971         paused = true;
 972
 973         // Tell-based protocol can replay transaction state, so it is safe to blow it up when we are paused.
 974         knownFrontends.values().forEach(LeaderFrontendState::retire);
 975         knownFrontends = ImmutableMap.of();
 976
 977         store.setRunOnPendingTransactionsComplete(operation);
 978     }
 979
 980     @Override
 981     protected void unpauseLeader() {
 982         LOG.debug("{}: In unpauseLeader", persistenceId());
 983         paused = false;
 984
 985         store.setRunOnPendingTransactionsComplete(null);
 986
 987         // Restore tell-based protocol state as if we were becoming the leader
 988         knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 989     }
 990
 991     @Override
 992     protected OnDemandRaftState.AbstractBuilder<?, ?> newOnDemandRaftStateBuilder() {
 993         return OnDemandShardState.newBuilder().treeChangeListenerActors(treeChangeSupport.getListenerActors())
 994                 .commitCohortActors(store.getCohortActors());
 995     }
 996
 997     @Override
 998     public String persistenceId() {
 999         return this.name;
1000     }
1001
1002     @VisibleForTesting
1003     ShardCommitCoordinator getCommitCoordinator() {
1004         return commitCoordinator;
1005     }
1006
1007     public DatastoreContext getDatastoreContext() {
1008         return datastoreContext;
1009     }
1010
1011     @VisibleForTesting
1012     public ShardDataTree getDataStore() {
1013         return store;
1014     }
1015
1016     @VisibleForTesting
1017     ShardStats getShardMBean() {
1018         return shardMBean;
1019     }
1020
1021     public static Builder builder() {
1022         return new Builder();
1023     }
1024
1025     public abstract static class AbstractBuilder<T extends AbstractBuilder<T, S>, S extends Shard> {
1026         private final Class<S> shardClass;
1027         private ShardIdentifier id;
1028         private Map<String, String> peerAddresses = Collections.emptyMap();
1029         private DatastoreContext datastoreContext;
1030         private SchemaContextProvider schemaContextProvider;
1031         private DatastoreSnapshot.ShardSnapshot restoreFromSnapshot;
1032         private DataTree dataTree;
1033         private volatile boolean sealed;
1034
1035         protected AbstractBuilder(final Class<S> shardClass) {
1036             this.shardClass = shardClass;
1037         }
1038
1039         protected void checkSealed() {
1040             Preconditions.checkState(!sealed, "Builder isalready sealed - further modifications are not allowed");
1041         }
1042
1043         @SuppressWarnings("unchecked")
1044         private T self() {
1045             return (T) this;
1046         }
1047
1048         public T id(final ShardIdentifier newId) {
1049             checkSealed();
1050             this.id = newId;
1051             return self();
1052         }
1053
1054         public T peerAddresses(final Map<String, String> newPeerAddresses) {
1055             checkSealed();
1056             this.peerAddresses = newPeerAddresses;
1057             return self();
1058         }
1059
1060         public T datastoreContext(final DatastoreContext newDatastoreContext) {
1061             checkSealed();
1062             this.datastoreContext = newDatastoreContext;
1063             return self();
1064         }
1065
1066         public T schemaContextProvider(final SchemaContextProvider newSchemaContextProvider) {
1067             checkSealed();
1068             this.schemaContextProvider = Preconditions.checkNotNull(newSchemaContextProvider);
1069             return self();
1070         }
1071
1072         public T restoreFromSnapshot(final DatastoreSnapshot.ShardSnapshot newRestoreFromSnapshot) {
1073             checkSealed();
1074             this.restoreFromSnapshot = newRestoreFromSnapshot;
1075             return self();
1076         }
1077
1078         public T dataTree(final DataTree newDataTree) {
1079             checkSealed();
1080             this.dataTree = newDataTree;
1081             return self();
1082         }
1083
1084         public ShardIdentifier getId() {
1085             return id;
1086         }
1087
1088         public Map<String, String> getPeerAddresses() {
1089             return peerAddresses;
1090         }
1091
1092         public DatastoreContext getDatastoreContext() {
1093             return datastoreContext;
1094         }
1095
1096         public SchemaContext getSchemaContext() {
1097             return Verify.verifyNotNull(schemaContextProvider.getSchemaContext());
1098         }
1099
1100         public DatastoreSnapshot.ShardSnapshot getRestoreFromSnapshot() {
1101             return restoreFromSnapshot;
1102         }
1103
1104         public DataTree getDataTree() {
1105             return dataTree;
1106         }
1107
1108         public TreeType getTreeType() {
1109             switch (datastoreContext.getLogicalStoreType()) {
1110                 case CONFIGURATION:
1111                     return TreeType.CONFIGURATION;
1112                 case OPERATIONAL:
1113                     return TreeType.OPERATIONAL;
1114                 default:
1115                     throw new IllegalStateException("Unhandled logical store type "
1116                             + datastoreContext.getLogicalStoreType());
1117             }
1118         }
1119
1120         protected void verify() {
1121             Preconditions.checkNotNull(id, "id should not be null");
1122             Preconditions.checkNotNull(peerAddresses, "peerAddresses should not be null");
1123             Preconditions.checkNotNull(datastoreContext, "dataStoreContext should not be null");
1124             Preconditions.checkNotNull(schemaContextProvider, "schemaContextProvider should not be null");
1125         }
1126
1127         public Props props() {
1128             sealed = true;
1129             verify();
1130             return Props.create(shardClass, this);
1131         }
1132     }
1133
1134     public static class Builder extends AbstractBuilder<Builder, Shard> {
1135         Builder() {
1136             super(Shard.class);
1137         }
1138     }
1139
1140     Ticker ticker() {
1141         return Ticker.systemTicker();
1142     }
1143
1144     void scheduleNextPendingTransaction() {
1145         self().tell(RESUME_NEXT_PENDING_TRANSACTION, ActorRef.noSender());
1146     }
1147 }