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