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

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8
   9 package org.opendaylight.controller.cluster.datastore;
  10
  11 import akka.actor.ActorRef;
  12 import akka.actor.ActorSelection;
  13 import akka.actor.Cancellable;
  14 import akka.actor.Props;
  15 import akka.actor.Status;
  16 import akka.actor.Status.Failure;
  17 import akka.serialization.Serialization;
  18 import com.google.common.annotations.VisibleForTesting;
  19 import com.google.common.base.Optional;
  20 import com.google.common.base.Preconditions;
  21 import com.google.common.base.Ticker;
  22 import com.google.common.base.Verify;
  23 import com.google.common.collect.ImmutableList;
  24 import com.google.common.collect.ImmutableMap;
  25 import com.google.common.collect.Range;
  26 import java.io.IOException;
  27 import java.util.Arrays;
  28 import java.util.Collection;
  29 import java.util.Collections;
  30 import java.util.Map;
  31 import java.util.concurrent.TimeUnit;
  32 import javax.annotation.Nonnull;
  33 import javax.annotation.Nullable;
  34 import org.opendaylight.controller.cluster.access.ABIVersion;
  35 import org.opendaylight.controller.cluster.access.commands.ConnectClientRequest;
  36 import org.opendaylight.controller.cluster.access.commands.ConnectClientSuccess;
  37 import org.opendaylight.controller.cluster.access.commands.LocalHistoryRequest;
  38 import org.opendaylight.controller.cluster.access.commands.NotLeaderException;
  39 import org.opendaylight.controller.cluster.access.commands.OutOfSequenceEnvelopeException;
  40 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  41 import org.opendaylight.controller.cluster.access.concepts.ClientIdentifier;
  42 import org.opendaylight.controller.cluster.access.concepts.FrontendIdentifier;
  43 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  44 import org.opendaylight.controller.cluster.access.concepts.Request;
  45 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  46 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  47 import org.opendaylight.controller.cluster.access.concepts.RequestSuccess;
  48 import org.opendaylight.controller.cluster.access.concepts.RetiredGenerationException;
  49 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  50 import org.opendaylight.controller.cluster.access.concepts.SliceableMessage;
  51 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  52 import org.opendaylight.controller.cluster.access.concepts.UnsupportedRequestException;
  53 import org.opendaylight.controller.cluster.common.actor.CommonConfig;
  54 import org.opendaylight.controller.cluster.common.actor.Dispatchers;
  55 import org.opendaylight.controller.cluster.common.actor.Dispatchers.DispatcherType;
  56 import org.opendaylight.controller.cluster.common.actor.MessageTracker;
  57 import org.opendaylight.controller.cluster.common.actor.MessageTracker.Error;
  58 import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
  59 import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
  60 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  61 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
  62 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
  63 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
  64 import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
  65 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  66 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  67 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  68 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  69 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  70 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  71 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  72 import org.opendaylight.controller.cluster.datastore.messages.GetShardDataTree;
  73 import org.opendaylight.controller.cluster.datastore.messages.MakeLeaderLocal;
  74 import org.opendaylight.controller.cluster.datastore.messages.OnDemandShardState;
  75 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
  76 import org.opendaylight.controller.cluster.datastore.messages.PersistAbortTransactionPayload;
  77 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  78 import org.opendaylight.controller.cluster.datastore.messages.RegisterChangeListener;
  79 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  80 import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
  81 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
  82 import org.opendaylight.controller.cluster.datastore.persisted.AbortTransactionPayload;
  83 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot;
  84 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot.ShardSnapshot;
  85 import org.opendaylight.controller.cluster.messaging.MessageSlicer;
  86 import org.opendaylight.controller.cluster.messaging.SliceOptions;
  87 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  88 import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
  89 import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
  90 import org.opendaylight.controller.cluster.raft.LeadershipTransferFailedException;
  91 import org.opendaylight.controller.cluster.raft.RaftActor;
  92 import org.opendaylight.controller.cluster.raft.RaftActorRecoveryCohort;
  93 import org.opendaylight.controller.cluster.raft.RaftActorSnapshotCohort;
  94 import org.opendaylight.controller.cluster.raft.RaftState;
  95 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
  96 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  97 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
  98 import org.opendaylight.controller.cluster.raft.messages.RequestLeadership;
  99 import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
 100 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 101 import org.opendaylight.yangtools.concepts.Identifier;
 102 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
 103 import org.opendaylight.yangtools.yang.data.api.schema.tree.TipProducingDataTree;
 104 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 105 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 106 import org.opendaylight.yangtools.yang.model.api.SchemaContextProvider;
 107 import scala.concurrent.duration.Duration;
 108 import scala.concurrent.duration.FiniteDuration;
 109
 110 /**
 111  * A Shard represents a portion of the logical data tree.
 112  *
 113  * <p>
 114  * Our Shard uses InMemoryDataTree as it's internal representation and delegates all requests it
 115  */
 116 public class Shard extends RaftActor {
 117
 118     @VisibleForTesting
 119     static final Object TX_COMMIT_TIMEOUT_CHECK_MESSAGE = new Object() {
 120         @Override
 121         public String toString() {
 122             return "txCommitTimeoutCheck";
 123         }
 124     };
 125
 126     @VisibleForTesting
 127     static final Object GET_SHARD_MBEAN_MESSAGE = new Object() {
 128         @Override
 129         public String toString() {
 130             return "getShardMBeanMessage";
 131         }
 132     };
 133
 134     static final Object RESUME_NEXT_PENDING_TRANSACTION = new Object() {
 135         @Override
 136         public String toString() {
 137             return "resumeNextPendingTransaction";
 138         }
 139     };
 140
 141     // FIXME: shard names should be encapsulated in their own class and this should be exposed as a constant.
 142     public static final String DEFAULT_NAME = "default";
 143
 144     private static final Collection<ABIVersion> SUPPORTED_ABIVERSIONS;
 145
 146     static {
 147         final ABIVersion[] values = ABIVersion.values();
 148         final ABIVersion[] real = Arrays.copyOfRange(values, 1, values.length - 1);
 149         SUPPORTED_ABIVERSIONS = ImmutableList.copyOf(real).reverse();
 150     }
 151
 152     // FIXME: make this a dynamic property based on mailbox size and maximum number of clients
 153     private static final int CLIENT_MAX_MESSAGES = 1000;
 154
 155     // The state of this Shard
 156     private final ShardDataTree store;
 157
 158     /// The name of this shard
 159     private final String name;
 160
 161     private final ShardStats shardMBean;
 162
 163     private DatastoreContext datastoreContext;
 164
 165     private final ShardCommitCoordinator commitCoordinator;
 166
 167     private long transactionCommitTimeout;
 168
 169     private Cancellable txCommitTimeoutCheckSchedule;
 170
 171     private final Optional<ActorRef> roleChangeNotifier;
 172
 173     private final MessageTracker appendEntriesReplyTracker;
 174
 175     private final ShardTransactionActorFactory transactionActorFactory;
 176
 177     private final ShardSnapshotCohort snapshotCohort;
 178
 179     private final DataTreeChangeListenerSupport treeChangeSupport = new DataTreeChangeListenerSupport(this);
 180     private final DataChangeListenerSupport changeSupport = new DataChangeListenerSupport(this);
 181
 182
 183     private ShardSnapshot restoreFromSnapshot;
 184
 185     private final ShardTransactionMessageRetrySupport messageRetrySupport;
 186
 187     private final FrontendMetadata frontendMetadata;
 188     private Map<FrontendIdentifier, LeaderFrontendState> knownFrontends = ImmutableMap.of();
 189     private boolean paused;
 190
 191     private final MessageSlicer responseMessageSlicer;
 192     private final Dispatchers dispatchers;
 193
 194     protected Shard(final AbstractBuilder<?, ?> builder) {
 195         super(builder.getId().toString(), builder.getPeerAddresses(),
 196                 Optional.of(builder.getDatastoreContext().getShardRaftConfig()), DataStoreVersions.CURRENT_VERSION);
 197
 198         this.name = builder.getId().toString();
 199         this.datastoreContext = builder.getDatastoreContext();
 200         this.restoreFromSnapshot = builder.getRestoreFromSnapshot();
 201         this.frontendMetadata = new FrontendMetadata(name);
 202
 203         setPersistence(datastoreContext.isPersistent());
 204
 205         LOG.info("Shard created : {}, persistent : {}", name, datastoreContext.isPersistent());
 206
 207         ShardDataTreeChangeListenerPublisherActorProxy treeChangeListenerPublisher =
 208                 new ShardDataTreeChangeListenerPublisherActorProxy(getContext(), name + "-DTCL-publisher", name);
 209         ShardDataChangeListenerPublisherActorProxy dataChangeListenerPublisher =
 210                 new ShardDataChangeListenerPublisherActorProxy(getContext(), name + "-DCL-publisher", name);
 211         if (builder.getDataTree() != null) {
 212             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getDataTree(),
 213                     treeChangeListenerPublisher, dataChangeListenerPublisher, name, frontendMetadata);
 214         } else {
 215             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getTreeType(),
 216                     builder.getDatastoreContext().getStoreRoot(), treeChangeListenerPublisher,
 217                     dataChangeListenerPublisher, name, frontendMetadata);
 218         }
 219
 220         shardMBean = ShardMBeanFactory.getShardStatsMBean(name, datastoreContext.getDataStoreMXBeanType(), this);
 221
 222         if (isMetricsCaptureEnabled()) {
 223             getContext().become(new MeteringBehavior(this));
 224         }
 225
 226         commitCoordinator = new ShardCommitCoordinator(store, LOG, this.name);
 227
 228         setTransactionCommitTimeout();
 229
 230         // create a notifier actor for each cluster member
 231         roleChangeNotifier = createRoleChangeNotifier(name);
 232
 233         appendEntriesReplyTracker = new MessageTracker(AppendEntriesReply.class,
 234                 getRaftActorContext().getConfigParams().getIsolatedCheckIntervalInMillis());
 235
 236         dispatchers = new Dispatchers(context().system().dispatchers());
 237         transactionActorFactory = new ShardTransactionActorFactory(store, datastoreContext,
 238             dispatchers.getDispatcherPath(Dispatchers.DispatcherType.Transaction),
 239                 self(), getContext(), shardMBean, builder.getId().getShardName());
 240
 241         snapshotCohort = ShardSnapshotCohort.create(getContext(), builder.getId().getMemberName(), store, LOG,
 242             this.name);
 243
 244         messageRetrySupport = new ShardTransactionMessageRetrySupport(this);
 245
 246         responseMessageSlicer = MessageSlicer.builder().logContext(this.name)
 247                 .messageSliceSize(datastoreContext.getMaximumMessageSliceSize())
 248                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 249                 .expireStateAfterInactivity(2, TimeUnit.MINUTES).build();
 250     }
 251
 252     private void setTransactionCommitTimeout() {
 253         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
 254                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS) / 2;
 255     }
 256
 257     private Optional<ActorRef> createRoleChangeNotifier(final String shardId) {
 258         ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
 259             RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
 260         return Optional.of(shardRoleChangeNotifier);
 261     }
 262
 263     @Override
 264     public void postStop() {
 265         LOG.info("Stopping Shard {}", persistenceId());
 266
 267         super.postStop();
 268
 269         messageRetrySupport.close();
 270
 271         if (txCommitTimeoutCheckSchedule != null) {
 272             txCommitTimeoutCheckSchedule.cancel();
 273         }
 274
 275         commitCoordinator.abortPendingTransactions("Transaction aborted due to shutdown.", this);
 276
 277         shardMBean.unregisterMBean();
 278     }
 279
 280     @Override
 281     protected void handleRecover(final Object message) {
 282         LOG.debug("{}: onReceiveRecover: Received message {} from {}", persistenceId(), message.getClass(),
 283             getSender());
 284
 285         super.handleRecover(message);
 286         if (LOG.isTraceEnabled()) {
 287             appendEntriesReplyTracker.begin();
 288         }
 289     }
 290
 291     @Override
 292     protected void handleNonRaftCommand(final Object message) {
 293         try (MessageTracker.Context context = appendEntriesReplyTracker.received(message)) {
 294             final Optional<Error> maybeError = context.error();
 295             if (maybeError.isPresent()) {
 296                 LOG.trace("{} : AppendEntriesReply failed to arrive at the expected interval {}", persistenceId(),
 297                     maybeError.get());
 298             }
 299
 300             store.resetTransactionBatch();
 301
 302             if (message instanceof RequestEnvelope) {
 303                 handleRequestEnvelope((RequestEnvelope)message);
 304             } else if (message instanceof ConnectClientRequest) {
 305                 handleConnectClient((ConnectClientRequest)message);
 306             } else if (CreateTransaction.isSerializedType(message)) {
 307                 handleCreateTransaction(message);
 308             } else if (message instanceof BatchedModifications) {
 309                 handleBatchedModifications((BatchedModifications)message);
 310             } else if (message instanceof ForwardedReadyTransaction) {
 311                 handleForwardedReadyTransaction((ForwardedReadyTransaction) message);
 312             } else if (message instanceof ReadyLocalTransaction) {
 313                 handleReadyLocalTransaction((ReadyLocalTransaction)message);
 314             } else if (CanCommitTransaction.isSerializedType(message)) {
 315                 handleCanCommitTransaction(CanCommitTransaction.fromSerializable(message));
 316             } else if (CommitTransaction.isSerializedType(message)) {
 317                 handleCommitTransaction(CommitTransaction.fromSerializable(message));
 318             } else if (AbortTransaction.isSerializedType(message)) {
 319                 handleAbortTransaction(AbortTransaction.fromSerializable(message));
 320             } else if (CloseTransactionChain.isSerializedType(message)) {
 321                 closeTransactionChain(CloseTransactionChain.fromSerializable(message));
 322             } else if (message instanceof RegisterChangeListener) {
 323                 changeSupport.onMessage((RegisterChangeListener) message, isLeader(), hasLeader());
 324             } else if (message instanceof RegisterDataTreeChangeListener) {
 325                 treeChangeSupport.onMessage((RegisterDataTreeChangeListener) message, isLeader(), hasLeader());
 326             } else if (message instanceof UpdateSchemaContext) {
 327                 updateSchemaContext((UpdateSchemaContext) message);
 328             } else if (message instanceof PeerAddressResolved) {
 329                 PeerAddressResolved resolved = (PeerAddressResolved) message;
 330                 setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
 331             } else if (TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
 332                 commitTimeoutCheck();
 333             } else if (message instanceof DatastoreContext) {
 334                 onDatastoreContext((DatastoreContext)message);
 335             } else if (message instanceof RegisterRoleChangeListener) {
 336                 roleChangeNotifier.get().forward(message, context());
 337             } else if (message instanceof FollowerInitialSyncUpStatus) {
 338                 shardMBean.setFollowerInitialSyncStatus(((FollowerInitialSyncUpStatus) message).isInitialSyncDone());
 339                 context().parent().tell(message, self());
 340             } else if (GET_SHARD_MBEAN_MESSAGE.equals(message)) {
 341                 sender().tell(getShardMBean(), self());
 342             } else if (message instanceof GetShardDataTree) {
 343                 sender().tell(store.getDataTree(), self());
 344             } else if (message instanceof ServerRemoved) {
 345                 context().parent().forward(message, context());
 346             } else if (ShardTransactionMessageRetrySupport.TIMER_MESSAGE_CLASS.isInstance(message)) {
 347                 messageRetrySupport.onTimerMessage(message);
 348             } else if (message instanceof DataTreeCohortActorRegistry.CohortRegistryCommand) {
 349                 store.processCohortRegistryCommand(getSender(),
 350                         (DataTreeCohortActorRegistry.CohortRegistryCommand) message);
 351             } else if (message instanceof PersistAbortTransactionPayload) {
 352                 final TransactionIdentifier txId = ((PersistAbortTransactionPayload) message).getTransactionId();
 353                 persistPayload(txId, AbortTransactionPayload.create(txId), true);
 354             } else if (message instanceof MakeLeaderLocal) {
 355                 onMakeLeaderLocal();
 356             } else if (RESUME_NEXT_PENDING_TRANSACTION.equals(message)) {
 357                 store.resumeNextPendingTransaction();
 358             } else if (!responseMessageSlicer.handleMessage(message)) {
 359                 super.handleNonRaftCommand(message);
 360             }
 361         }
 362     }
 363
 364     @SuppressWarnings("checkstyle:IllegalCatch")
 365     private void handleRequestEnvelope(final RequestEnvelope envelope) {
 366         final long now = ticker().read();
 367         try {
 368             final RequestSuccess<?, ?> success = handleRequest(envelope, now);
 369             if (success != null) {
 370                 final long executionTimeNanos = ticker().read() - now;
 371                 if (success instanceof SliceableMessage) {
 372                     dispatchers.getDispatcher(DispatcherType.Serialization).execute(() ->
 373                         responseMessageSlicer.slice(SliceOptions.builder().identifier(success.getTarget())
 374                             .message(envelope.newSuccessEnvelope(success, executionTimeNanos))
 375                             .sendTo(envelope.getMessage().getReplyTo()).replyTo(self())
 376                             .onFailureCallback(t -> {
 377                                 LOG.warn("Error slicing response {}", success, t);
 378                             }).build()));
 379                 } else {
 380                     envelope.sendSuccess(success, executionTimeNanos);
 381                 }
 382             }
 383         } catch (RequestException e) {
 384             LOG.debug("{}: request {} failed", persistenceId(), envelope, e);
 385             envelope.sendFailure(e, ticker().read() - now);
 386         } catch (Exception e) {
 387             LOG.debug("{}: request {} caused failure", persistenceId(), envelope, e);
 388             envelope.sendFailure(new RuntimeRequestException("Request failed to process", e),
 389                 ticker().read() - now);
 390         }
 391     }
 392
 393     private void commitTimeoutCheck() {
 394         store.checkForExpiredTransactions(transactionCommitTimeout, this::updateAccess);
 395         commitCoordinator.checkForExpiredTransactions(transactionCommitTimeout, this);
 396     }
 397
 398     private Optional<Long> updateAccess(final SimpleShardDataTreeCohort cohort) {
 399         final FrontendIdentifier frontend = cohort.getIdentifier().getHistoryId().getClientId().getFrontendId();
 400         // If this frontend has freshly connected, give it some time to catch up before killing its transactions.
 401         final LeaderFrontendState state = knownFrontends.get(frontend);
 402         return state == null ? Optional.absent() : Optional.of(state.getLastConnectTicks());
 403     }
 404
 405     private void onMakeLeaderLocal() {
 406         LOG.debug("{}: onMakeLeaderLocal received", persistenceId());
 407         if (isLeader()) {
 408             getSender().tell(new Status.Success(null), getSelf());
 409             return;
 410         }
 411
 412         final ActorSelection leader = getLeader();
 413
 414         if (leader == null) {
 415             // Leader is not present. The cluster is most likely trying to
 416             // elect a leader and we should let that run its normal course
 417
 418             // TODO we can wait for the election to complete and retry the
 419             // request. We can also let the caller retry by sending a flag
 420             // in the response indicating the request is "reTryable".
 421             getSender().tell(new Failure(
 422                     new LeadershipTransferFailedException("We cannot initiate leadership transfer to local node. "
 423                             + "Currently there is no leader for " + persistenceId())),
 424                     getSelf());
 425             return;
 426         }
 427
 428         leader.tell(new RequestLeadership(getId(), getSender()), getSelf());
 429     }
 430
 431     // Acquire our frontend tracking handle and verify generation matches
 432     @Nullable
 433     private LeaderFrontendState findFrontend(final ClientIdentifier clientId) throws RequestException {
 434         final LeaderFrontendState existing = knownFrontends.get(clientId.getFrontendId());
 435         if (existing != null) {
 436             final int cmp = Long.compareUnsigned(existing.getIdentifier().getGeneration(), clientId.getGeneration());
 437             if (cmp == 0) {
 438                 existing.touch();
 439                 return existing;
 440             }
 441             if (cmp > 0) {
 442                 LOG.debug("{}: rejecting request from outdated client {}", persistenceId(), clientId);
 443                 throw new RetiredGenerationException(existing.getIdentifier().getGeneration());
 444             }
 445
 446             LOG.info("{}: retiring state {}, outdated by request from client {}", persistenceId(), existing, clientId);
 447             existing.retire();
 448             knownFrontends.remove(clientId.getFrontendId());
 449         } else {
 450             LOG.debug("{}: client {} is not yet known", persistenceId(), clientId);
 451         }
 452
 453         return null;
 454     }
 455
 456     private LeaderFrontendState getFrontend(final ClientIdentifier clientId) throws RequestException {
 457         final LeaderFrontendState ret = findFrontend(clientId);
 458         if (ret != null) {
 459             return ret;
 460         }
 461
 462         // TODO: a dedicated exception would be better, but this is technically true, too
 463         throw new OutOfSequenceEnvelopeException(0);
 464     }
 465
 466     private static @Nonnull ABIVersion selectVersion(final ConnectClientRequest message) {
 467         final Range<ABIVersion> clientRange = Range.closed(message.getMinVersion(), message.getMaxVersion());
 468         for (ABIVersion v : SUPPORTED_ABIVERSIONS) {
 469             if (clientRange.contains(v)) {
 470                 return v;
 471             }
 472         }
 473
 474         throw new IllegalArgumentException(String.format(
 475             "No common version between backend versions %s and client versions %s", SUPPORTED_ABIVERSIONS,
 476             clientRange));
 477     }
 478
 479     @SuppressWarnings("checkstyle:IllegalCatch")
 480     private void handleConnectClient(final ConnectClientRequest message) {
 481         try {
 482             final ClientIdentifier clientId = message.getTarget();
 483             final LeaderFrontendState existing = findFrontend(clientId);
 484             if (existing != null) {
 485                 existing.touch();
 486             }
 487
 488             if (!isLeader() || !isLeaderActive()) {
 489                 LOG.info("{}: not currently leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 490                                 + "isLeadershipTransferInProgress: {}.",
 491                         persistenceId(), message, isLeader(), isLeaderActive(), isLeadershipTransferInProgress());
 492                 throw new NotLeaderException(getSelf());
 493             }
 494
 495             final ABIVersion selectedVersion = selectVersion(message);
 496             final LeaderFrontendState frontend;
 497             if (existing == null) {
 498                 frontend = new LeaderFrontendState(persistenceId(), clientId, store);
 499                 knownFrontends.put(clientId.getFrontendId(), frontend);
 500                 LOG.debug("{}: created state {} for client {}", persistenceId(), frontend, clientId);
 501             } else {
 502                 frontend = existing;
 503             }
 504
 505             frontend.reconnect();
 506             message.getReplyTo().tell(new ConnectClientSuccess(message.getTarget(), message.getSequence(), getSelf(),
 507                 ImmutableList.of(), store.getDataTree(), CLIENT_MAX_MESSAGES).toVersion(selectedVersion),
 508                 ActorRef.noSender());
 509         } catch (RequestException | RuntimeException e) {
 510             message.getReplyTo().tell(new Failure(e), ActorRef.noSender());
 511         }
 512     }
 513
 514     private @Nullable RequestSuccess<?, ?> handleRequest(final RequestEnvelope envelope, final long now)
 515             throws RequestException {
 516         // We are not the leader, hence we want to fail-fast.
 517         if (!isLeader() || paused || !isLeaderActive()) {
 518             LOG.debug("{}: not currently active leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 519                             + "isLeadershipTransferInProgress: {}, paused: {}",
 520                     persistenceId(), envelope, isLeader(), isLeaderActive(), isLeadershipTransferInProgress(), paused);
 521             throw new NotLeaderException(getSelf());
 522         }
 523
 524         final Request<?, ?> request = envelope.getMessage();
 525         if (request instanceof TransactionRequest) {
 526             final TransactionRequest<?> txReq = (TransactionRequest<?>)request;
 527             final ClientIdentifier clientId = txReq.getTarget().getHistoryId().getClientId();
 528             return getFrontend(clientId).handleTransactionRequest(txReq, envelope, now);
 529         } else if (request instanceof LocalHistoryRequest) {
 530             final LocalHistoryRequest<?> lhReq = (LocalHistoryRequest<?>)request;
 531             final ClientIdentifier clientId = lhReq.getTarget().getClientId();
 532             return getFrontend(clientId).handleLocalHistoryRequest(lhReq, envelope, now);
 533         } else {
 534             LOG.warn("{}: rejecting unsupported request {}", persistenceId(), request);
 535             throw new UnsupportedRequestException(request);
 536         }
 537     }
 538
 539     private boolean hasLeader() {
 540         return getLeaderId() != null;
 541     }
 542
 543     public int getPendingTxCommitQueueSize() {
 544         return store.getQueueSize();
 545     }
 546
 547     public int getCohortCacheSize() {
 548         return commitCoordinator.getCohortCacheSize();
 549     }
 550
 551     @Override
 552     protected Optional<ActorRef> getRoleChangeNotifier() {
 553         return roleChangeNotifier;
 554     }
 555
 556     @Override
 557     protected LeaderStateChanged newLeaderStateChanged(final String memberId, final String leaderId,
 558             final short leaderPayloadVersion) {
 559         return isLeader() ? new ShardLeaderStateChanged(memberId, leaderId, store.getDataTree(), leaderPayloadVersion)
 560                 : new ShardLeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 561     }
 562
 563     protected void onDatastoreContext(final DatastoreContext context) {
 564         datastoreContext = context;
 565
 566         setTransactionCommitTimeout();
 567
 568         setPersistence(datastoreContext.isPersistent());
 569
 570         updateConfigParams(datastoreContext.getShardRaftConfig());
 571     }
 572
 573     // applyState() will be invoked once consensus is reached on the payload
 574     void persistPayload(final Identifier id, final Payload payload, final boolean batchHint) {
 575         boolean canSkipPayload = !hasFollowers() && !persistence().isRecoveryApplicable();
 576         if (canSkipPayload) {
 577             applyState(self(), id, payload);
 578         } else {
 579             // We are faking the sender
 580             persistData(self(), id, payload, batchHint);
 581         }
 582     }
 583
 584     private void handleCommitTransaction(final CommitTransaction commit) {
 585         if (isLeader()) {
 586             commitCoordinator.handleCommit(commit.getTransactionId(), getSender(), this);
 587         } else {
 588             ActorSelection leader = getLeader();
 589             if (leader == null) {
 590                 messageRetrySupport.addMessageToRetry(commit, getSender(),
 591                         "Could not commit transaction " + commit.getTransactionId());
 592             } else {
 593                 LOG.debug("{}: Forwarding CommitTransaction to leader {}", persistenceId(), leader);
 594                 leader.forward(commit, getContext());
 595             }
 596         }
 597     }
 598
 599     private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
 600         LOG.debug("{}: Can committing transaction {}", persistenceId(), canCommit.getTransactionId());
 601
 602         if (isLeader()) {
 603             commitCoordinator.handleCanCommit(canCommit.getTransactionId(), getSender(), this);
 604         } else {
 605             ActorSelection leader = getLeader();
 606             if (leader == null) {
 607                 messageRetrySupport.addMessageToRetry(canCommit, getSender(),
 608                         "Could not canCommit transaction " + canCommit.getTransactionId());
 609             } else {
 610                 LOG.debug("{}: Forwarding CanCommitTransaction to leader {}", persistenceId(), leader);
 611                 leader.forward(canCommit, getContext());
 612             }
 613         }
 614     }
 615
 616     @SuppressWarnings("checkstyle:IllegalCatch")
 617     protected void handleBatchedModificationsLocal(final BatchedModifications batched, final ActorRef sender) {
 618         try {
 619             commitCoordinator.handleBatchedModifications(batched, sender, this);
 620         } catch (Exception e) {
 621             LOG.error("{}: Error handling BatchedModifications for Tx {}", persistenceId(),
 622                     batched.getTransactionId(), e);
 623             sender.tell(new Failure(e), getSelf());
 624         }
 625     }
 626
 627     private void handleBatchedModifications(final BatchedModifications batched) {
 628         // This message is sent to prepare the modifications transaction directly on the Shard as an
 629         // optimization to avoid the extra overhead of a separate ShardTransaction actor. On the last
 630         // BatchedModifications message, the caller sets the ready flag in the message indicating
 631         // modifications are complete. The reply contains the cohort actor path (this actor) for the caller
 632         // to initiate the 3-phase commit. This also avoids the overhead of sending an additional
 633         // ReadyTransaction message.
 634
 635         // If we're not the leader then forward to the leader. This is a safety measure - we shouldn't
 636         // normally get here if we're not the leader as the front-end (TransactionProxy) should determine
 637         // the primary/leader shard. However with timing and caching on the front-end, there's a small
 638         // window where it could have a stale leader during leadership transitions.
 639         //
 640         boolean isLeaderActive = isLeaderActive();
 641         if (isLeader() && isLeaderActive) {
 642             handleBatchedModificationsLocal(batched, getSender());
 643         } else {
 644             ActorSelection leader = getLeader();
 645             if (!isLeaderActive || leader == null) {
 646                 messageRetrySupport.addMessageToRetry(batched, getSender(),
 647                         "Could not commit transaction " + batched.getTransactionId());
 648             } else {
 649                 // If this is not the first batch and leadership changed in between batched messages,
 650                 // we need to reconstruct previous BatchedModifications from the transaction
 651                 // DataTreeModification, honoring the max batched modification count, and forward all the
 652                 // previous BatchedModifications to the new leader.
 653                 Collection<BatchedModifications> newModifications = commitCoordinator
 654                         .createForwardedBatchedModifications(batched,
 655                                 datastoreContext.getShardBatchedModificationCount());
 656
 657                 LOG.debug("{}: Forwarding {} BatchedModifications to leader {}", persistenceId(),
 658                         newModifications.size(), leader);
 659
 660                 for (BatchedModifications bm : newModifications) {
 661                     leader.forward(bm, getContext());
 662                 }
 663             }
 664         }
 665     }
 666
 667     private boolean failIfIsolatedLeader(final ActorRef sender) {
 668         if (isIsolatedLeader()) {
 669             sender.tell(new Failure(new NoShardLeaderException(String.format(
 670                     "Shard %s was the leader but has lost contact with all of its followers. Either all"
 671                     + " other follower nodes are down or this node is isolated by a network partition.",
 672                     persistenceId()))), getSelf());
 673             return true;
 674         }
 675
 676         return false;
 677     }
 678
 679     protected boolean isIsolatedLeader() {
 680         return getRaftState() == RaftState.IsolatedLeader;
 681     }
 682
 683     @SuppressWarnings("checkstyle:IllegalCatch")
 684     private void handleReadyLocalTransaction(final ReadyLocalTransaction message) {
 685         LOG.debug("{}: handleReadyLocalTransaction for {}", persistenceId(), message.getTransactionId());
 686
 687         boolean isLeaderActive = isLeaderActive();
 688         if (isLeader() && isLeaderActive) {
 689             try {
 690                 commitCoordinator.handleReadyLocalTransaction(message, getSender(), this);
 691             } catch (Exception e) {
 692                 LOG.error("{}: Error handling ReadyLocalTransaction for Tx {}", persistenceId(),
 693                         message.getTransactionId(), e);
 694                 getSender().tell(new Failure(e), getSelf());
 695             }
 696         } else {
 697             ActorSelection leader = getLeader();
 698             if (!isLeaderActive || leader == null) {
 699                 messageRetrySupport.addMessageToRetry(message, getSender(),
 700                         "Could not commit transaction " + message.getTransactionId());
 701             } else {
 702                 LOG.debug("{}: Forwarding ReadyLocalTransaction to leader {}", persistenceId(), leader);
 703                 message.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 704                 leader.forward(message, getContext());
 705             }
 706         }
 707     }
 708
 709     private void handleForwardedReadyTransaction(final ForwardedReadyTransaction forwardedReady) {
 710         LOG.debug("{}: handleForwardedReadyTransaction for {}", persistenceId(), forwardedReady.getTransactionId());
 711
 712         boolean isLeaderActive = isLeaderActive();
 713         if (isLeader() && isLeaderActive) {
 714             commitCoordinator.handleForwardedReadyTransaction(forwardedReady, getSender(), this);
 715         } else {
 716             ActorSelection leader = getLeader();
 717             if (!isLeaderActive || leader == null) {
 718                 messageRetrySupport.addMessageToRetry(forwardedReady, getSender(),
 719                         "Could not commit transaction " + forwardedReady.getTransactionId());
 720             } else {
 721                 LOG.debug("{}: Forwarding ForwardedReadyTransaction to leader {}", persistenceId(), leader);
 722
 723                 ReadyLocalTransaction readyLocal = new ReadyLocalTransaction(forwardedReady.getTransactionId(),
 724                         forwardedReady.getTransaction().getSnapshot(), forwardedReady.isDoImmediateCommit());
 725                 readyLocal.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 726                 leader.forward(readyLocal, getContext());
 727             }
 728         }
 729     }
 730
 731     private void handleAbortTransaction(final AbortTransaction abort) {
 732         doAbortTransaction(abort.getTransactionId(), getSender());
 733     }
 734
 735     void doAbortTransaction(final Identifier transactionID, final ActorRef sender) {
 736         commitCoordinator.handleAbort(transactionID, sender, this);
 737     }
 738
 739     private void handleCreateTransaction(final Object message) {
 740         if (isLeader()) {
 741             createTransaction(CreateTransaction.fromSerializable(message));
 742         } else if (getLeader() != null) {
 743             getLeader().forward(message, getContext());
 744         } else {
 745             getSender().tell(new Failure(new NoShardLeaderException(
 746                     "Could not create a shard transaction", persistenceId())), getSelf());
 747         }
 748     }
 749
 750     private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
 751         final LocalHistoryIdentifier id = closeTransactionChain.getIdentifier();
 752         store.closeTransactionChain(id, null);
 753         store.purgeTransactionChain(id, null);
 754     }
 755
 756     @SuppressWarnings("checkstyle:IllegalCatch")
 757     private void createTransaction(final CreateTransaction createTransaction) {
 758         try {
 759             if (TransactionType.fromInt(createTransaction.getTransactionType()) != TransactionType.READ_ONLY
 760                     && failIfIsolatedLeader(getSender())) {
 761                 return;
 762             }
 763
 764             ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
 765                 createTransaction.getTransactionId());
 766
 767             getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
 768                     createTransaction.getTransactionId(), createTransaction.getVersion()).toSerializable(), getSelf());
 769         } catch (Exception e) {
 770             getSender().tell(new Failure(e), getSelf());
 771         }
 772     }
 773
 774     private ActorRef createTransaction(final int transactionType, final TransactionIdentifier transactionId) {
 775         LOG.debug("{}: Creating transaction : {} ", persistenceId(), transactionId);
 776         return transactionActorFactory.newShardTransaction(TransactionType.fromInt(transactionType),
 777             transactionId);
 778     }
 779
 780     private void updateSchemaContext(final UpdateSchemaContext message) {
 781         updateSchemaContext(message.getSchemaContext());
 782     }
 783
 784     @VisibleForTesting
 785     void updateSchemaContext(final SchemaContext schemaContext) {
 786         store.updateSchemaContext(schemaContext);
 787     }
 788
 789     private boolean isMetricsCaptureEnabled() {
 790         CommonConfig config = new CommonConfig(getContext().system().settings().config());
 791         return config.isMetricCaptureEnabled();
 792     }
 793
 794     @Override
 795     @VisibleForTesting
 796     public RaftActorSnapshotCohort getRaftActorSnapshotCohort() {
 797         return snapshotCohort;
 798     }
 799
 800     @Override
 801     @Nonnull
 802     protected RaftActorRecoveryCohort getRaftActorRecoveryCohort() {
 803         return new ShardRecoveryCoordinator(store,
 804             restoreFromSnapshot != null ? restoreFromSnapshot.getSnapshot() : null, persistenceId(), LOG);
 805     }
 806
 807     @Override
 808     protected void onRecoveryComplete() {
 809         restoreFromSnapshot = null;
 810
 811         //notify shard manager
 812         getContext().parent().tell(new ActorInitialized(), getSelf());
 813
 814         // Being paranoid here - this method should only be called once but just in case...
 815         if (txCommitTimeoutCheckSchedule == null) {
 816             // Schedule a message to be periodically sent to check if the current in-progress
 817             // transaction should be expired and aborted.
 818             FiniteDuration period = Duration.create(transactionCommitTimeout / 3, TimeUnit.MILLISECONDS);
 819             txCommitTimeoutCheckSchedule = getContext().system().scheduler().schedule(
 820                     period, period, getSelf(),
 821                     TX_COMMIT_TIMEOUT_CHECK_MESSAGE, getContext().dispatcher(), ActorRef.noSender());
 822         }
 823     }
 824
 825     @Override
 826     protected void applyState(final ActorRef clientActor, final Identifier identifier, final Object data) {
 827         if (data instanceof Payload) {
 828             try {
 829                 store.applyReplicatedPayload(identifier, (Payload)data);
 830             } catch (DataValidationFailedException | IOException e) {
 831                 LOG.error("{}: Error applying replica {}", persistenceId(), identifier, e);
 832             }
 833         } else {
 834             LOG.error("{}: Unknown state for {} received {}", persistenceId(), identifier, data);
 835         }
 836     }
 837
 838     @Override
 839     protected void onStateChanged() {
 840         boolean isLeader = isLeader();
 841         boolean hasLeader = hasLeader();
 842         changeSupport.onLeadershipChange(isLeader, hasLeader);
 843         treeChangeSupport.onLeadershipChange(isLeader, hasLeader);
 844
 845         // If this actor is no longer the leader close all the transaction chains
 846         if (!isLeader) {
 847             if (LOG.isDebugEnabled()) {
 848                 LOG.debug(
 849                     "{}: onStateChanged: Closing all transaction chains because shard {} is no longer the leader",
 850                     persistenceId(), getId());
 851             }
 852
 853             paused = false;
 854             store.purgeLeaderState();
 855         }
 856
 857         if (hasLeader && !isIsolatedLeader()) {
 858             messageRetrySupport.retryMessages();
 859         }
 860     }
 861
 862     @Override
 863     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 864         shardMBean.incrementLeadershipChangeCount();
 865         paused = false;
 866
 867         if (!isLeader()) {
 868             if (!knownFrontends.isEmpty()) {
 869                 LOG.debug("{}: removing frontend state for {}", persistenceId(), knownFrontends.keySet());
 870                 knownFrontends = ImmutableMap.of();
 871             }
 872
 873             if (!hasLeader()) {
 874                 // No leader anywhere, nothing else to do
 875                 return;
 876             }
 877
 878             // Another leader was elected. If we were the previous leader and had pending transactions, convert
 879             // them to transaction messages and send to the new leader.
 880             ActorSelection leader = getLeader();
 881             if (leader != null) {
 882                 Collection<?> messagesToForward = convertPendingTransactionsToMessages();
 883
 884                 if (!messagesToForward.isEmpty()) {
 885                     LOG.debug("{}: Forwarding {} pending transaction messages to leader {}", persistenceId(),
 886                             messagesToForward.size(), leader);
 887
 888                     for (Object message : messagesToForward) {
 889                         leader.tell(message, self());
 890                     }
 891                 }
 892             } else {
 893                 commitCoordinator.abortPendingTransactions("The transacton was aborted due to inflight leadership "
 894                         + "change and the leader address isn't available.", this);
 895             }
 896         } else {
 897             // We have become the leader, we need to reconstruct frontend state
 898             knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 899             LOG.debug("{}: became leader with frontend state for {}", persistenceId(), knownFrontends.keySet());
 900         }
 901
 902         if (!isIsolatedLeader()) {
 903             messageRetrySupport.retryMessages();
 904         }
 905     }
 906
 907     /**
 908      * Clears all pending transactions and converts them to messages to be forwarded to a new leader.
 909      *
 910      * @return the converted messages
 911      */
 912     public Collection<?> convertPendingTransactionsToMessages() {
 913         return commitCoordinator.convertPendingTransactionsToMessages(
 914                 datastoreContext.getShardBatchedModificationCount());
 915     }
 916
 917     @Override
 918     protected void pauseLeader(final Runnable operation) {
 919         LOG.debug("{}: In pauseLeader, operation: {}", persistenceId(), operation);
 920         paused = true;
 921
 922         // Tell-based protocol can replay transaction state, so it is safe to blow it up when we are paused.
 923         knownFrontends.values().forEach(LeaderFrontendState::retire);
 924         knownFrontends = ImmutableMap.of();
 925
 926         store.setRunOnPendingTransactionsComplete(operation);
 927     }
 928
 929     @Override
 930     protected void unpauseLeader() {
 931         LOG.debug("{}: In unpauseLeader", persistenceId());
 932         paused = false;
 933
 934         store.setRunOnPendingTransactionsComplete(null);
 935
 936         // Restore tell-based protocol state as if we were becoming the leader
 937         knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
 938     }
 939
 940     @Override
 941     protected OnDemandRaftState.AbstractBuilder<?> newOnDemandRaftStateBuilder() {
 942         return OnDemandShardState.newBuilder().treeChangeListenerActors(treeChangeSupport.getListenerActors())
 943                 .dataChangeListenerActors(changeSupport.getListenerActors())
 944                 .commitCohortActors(store.getCohortActors());
 945     }
 946
 947     @Override
 948     public String persistenceId() {
 949         return this.name;
 950     }
 951
 952     @VisibleForTesting
 953     ShardCommitCoordinator getCommitCoordinator() {
 954         return commitCoordinator;
 955     }
 956
 957     public DatastoreContext getDatastoreContext() {
 958         return datastoreContext;
 959     }
 960
 961     @VisibleForTesting
 962     public ShardDataTree getDataStore() {
 963         return store;
 964     }
 965
 966     @VisibleForTesting
 967     ShardStats getShardMBean() {
 968         return shardMBean;
 969     }
 970
 971     public static Builder builder() {
 972         return new Builder();
 973     }
 974
 975     public abstract static class AbstractBuilder<T extends AbstractBuilder<T, S>, S extends Shard> {
 976         private final Class<S> shardClass;
 977         private ShardIdentifier id;
 978         private Map<String, String> peerAddresses = Collections.emptyMap();
 979         private DatastoreContext datastoreContext;
 980         private SchemaContextProvider schemaContextProvider;
 981         private DatastoreSnapshot.ShardSnapshot restoreFromSnapshot;
 982         private TipProducingDataTree dataTree;
 983         private volatile boolean sealed;
 984
 985         protected AbstractBuilder(final Class<S> shardClass) {
 986             this.shardClass = shardClass;
 987         }
 988
 989         protected void checkSealed() {
 990             Preconditions.checkState(!sealed, "Builder isalready sealed - further modifications are not allowed");
 991         }
 992
 993         @SuppressWarnings("unchecked")
 994         private T self() {
 995             return (T) this;
 996         }
 997
 998         public T id(final ShardIdentifier newId) {
 999             checkSealed();
1000             this.id = newId;
1001             return self();
1002         }
1003
1004         public T peerAddresses(final Map<String, String> newPeerAddresses) {
1005             checkSealed();
1006             this.peerAddresses = newPeerAddresses;
1007             return self();
1008         }
1009
1010         public T datastoreContext(final DatastoreContext newDatastoreContext) {
1011             checkSealed();
1012             this.datastoreContext = newDatastoreContext;
1013             return self();
1014         }
1015
1016         public T schemaContextProvider(final SchemaContextProvider schemaContextProvider) {
1017             checkSealed();
1018             this.schemaContextProvider = Preconditions.checkNotNull(schemaContextProvider);
1019             return self();
1020         }
1021
1022         public T restoreFromSnapshot(final DatastoreSnapshot.ShardSnapshot newRestoreFromSnapshot) {
1023             checkSealed();
1024             this.restoreFromSnapshot = newRestoreFromSnapshot;
1025             return self();
1026         }
1027
1028         public T dataTree(final TipProducingDataTree newDataTree) {
1029             checkSealed();
1030             this.dataTree = newDataTree;
1031             return self();
1032         }
1033
1034         public ShardIdentifier getId() {
1035             return id;
1036         }
1037
1038         public Map<String, String> getPeerAddresses() {
1039             return peerAddresses;
1040         }
1041
1042         public DatastoreContext getDatastoreContext() {
1043             return datastoreContext;
1044         }
1045
1046         public SchemaContext getSchemaContext() {
1047             return Verify.verifyNotNull(schemaContextProvider.getSchemaContext());
1048         }
1049
1050         public DatastoreSnapshot.ShardSnapshot getRestoreFromSnapshot() {
1051             return restoreFromSnapshot;
1052         }
1053
1054         public TipProducingDataTree getDataTree() {
1055             return dataTree;
1056         }
1057
1058         public TreeType getTreeType() {
1059             switch (datastoreContext.getLogicalStoreType()) {
1060                 case CONFIGURATION:
1061                     return TreeType.CONFIGURATION;
1062                 case OPERATIONAL:
1063                     return TreeType.OPERATIONAL;
1064                 default:
1065                     throw new IllegalStateException("Unhandled logical store type "
1066                             + datastoreContext.getLogicalStoreType());
1067             }
1068         }
1069
1070         protected void verify() {
1071             Preconditions.checkNotNull(id, "id should not be null");
1072             Preconditions.checkNotNull(peerAddresses, "peerAddresses should not be null");
1073             Preconditions.checkNotNull(datastoreContext, "dataStoreContext should not be null");
1074             Preconditions.checkNotNull(schemaContextProvider, "schemaContextProvider should not be null");
1075         }
1076
1077         public Props props() {
1078             sealed = true;
1079             verify();
1080             return Props.create(shardClass, this);
1081         }
1082     }
1083
1084     public static class Builder extends AbstractBuilder<Builder, Shard> {
1085         private Builder() {
1086             super(Shard.class);
1087         }
1088     }
1089
1090     Ticker ticker() {
1091         return Ticker.systemTicker();
1092     }
1093
1094     void scheduleNextPendingTransaction() {
1095         self().tell(RESUME_NEXT_PENDING_TRANSACTION, ActorRef.noSender());
1096     }
1097 }