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