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

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.cluster.datastore;
   9
  10 import static com.google.common.base.Preconditions.checkState;
  11 import static com.google.common.base.Verify.verify;
  12 import static com.google.common.base.Verify.verifyNotNull;
  13 import static java.util.Objects.requireNonNull;
  14
  15 import akka.actor.ActorRef;
  16 import akka.actor.ActorSelection;
  17 import akka.actor.Cancellable;
  18 import akka.actor.ExtendedActorSystem;
  19 import akka.actor.Props;
  20 import akka.actor.Status;
  21 import akka.actor.Status.Failure;
  22 import akka.serialization.JavaSerializer;
  23 import akka.serialization.Serialization;
  24 import com.google.common.annotations.VisibleForTesting;
  25 import com.google.common.base.Ticker;
  26 import com.google.common.base.Verify;
  27 import com.google.common.collect.ImmutableList;
  28 import com.google.common.collect.ImmutableMap;
  29 import com.google.common.collect.ImmutableSet;
  30 import com.google.common.collect.Range;
  31 import java.io.IOException;
  32 import java.util.Arrays;
  33 import java.util.Collection;
  34 import java.util.Collections;
  35 import java.util.HashMap;
  36 import java.util.Map;
  37 import java.util.Optional;
  38 import java.util.OptionalLong;
  39 import java.util.concurrent.TimeUnit;
  40 import org.eclipse.jdt.annotation.NonNull;
  41 import org.eclipse.jdt.annotation.Nullable;
  42 import org.opendaylight.controller.cluster.access.ABIVersion;
  43 import org.opendaylight.controller.cluster.access.commands.ConnectClientRequest;
  44 import org.opendaylight.controller.cluster.access.commands.ConnectClientSuccess;
  45 import org.opendaylight.controller.cluster.access.commands.LocalHistoryRequest;
  46 import org.opendaylight.controller.cluster.access.commands.NotLeaderException;
  47 import org.opendaylight.controller.cluster.access.commands.OutOfSequenceEnvelopeException;
  48 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  49 import org.opendaylight.controller.cluster.access.concepts.ClientIdentifier;
  50 import org.opendaylight.controller.cluster.access.concepts.FrontendIdentifier;
  51 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  52 import org.opendaylight.controller.cluster.access.concepts.Request;
  53 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  54 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  55 import org.opendaylight.controller.cluster.access.concepts.RequestSuccess;
  56 import org.opendaylight.controller.cluster.access.concepts.RetiredGenerationException;
  57 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  58 import org.opendaylight.controller.cluster.access.concepts.SliceableMessage;
  59 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  60 import org.opendaylight.controller.cluster.access.concepts.UnsupportedRequestException;
  61 import org.opendaylight.controller.cluster.common.actor.CommonConfig;
  62 import org.opendaylight.controller.cluster.common.actor.Dispatchers;
  63 import org.opendaylight.controller.cluster.common.actor.Dispatchers.DispatcherType;
  64 import org.opendaylight.controller.cluster.common.actor.MessageTracker;
  65 import org.opendaylight.controller.cluster.common.actor.MessageTracker.Error;
  66 import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
  67 import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
  68 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  69 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardDataTreeListenerInfoMXBeanImpl;
  70 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
  71 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
  72 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
  73 import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
  74 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  75 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  76 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  77 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  78 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  79 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  80 import org.opendaylight.controller.cluster.datastore.messages.DataTreeChangedReply;
  81 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  82 import org.opendaylight.controller.cluster.datastore.messages.GetKnownClients;
  83 import org.opendaylight.controller.cluster.datastore.messages.GetKnownClientsReply;
  84 import org.opendaylight.controller.cluster.datastore.messages.GetShardDataTree;
  85 import org.opendaylight.controller.cluster.datastore.messages.MakeLeaderLocal;
  86 import org.opendaylight.controller.cluster.datastore.messages.OnDemandShardState;
  87 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
  88 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  89 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  90 import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
  91 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
  92 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot;
  93 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot.ShardSnapshot;
  94 import org.opendaylight.controller.cluster.datastore.persisted.DisableTrackingPayload;
  95 import org.opendaylight.controller.cluster.messaging.MessageAssembler;
  96 import org.opendaylight.controller.cluster.messaging.MessageSlicer;
  97 import org.opendaylight.controller.cluster.messaging.SliceOptions;
  98 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  99 import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
 100 import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
 101 import org.opendaylight.controller.cluster.raft.LeadershipTransferFailedException;
 102 import org.opendaylight.controller.cluster.raft.RaftActor;
 103 import org.opendaylight.controller.cluster.raft.RaftActorRecoveryCohort;
 104 import org.opendaylight.controller.cluster.raft.RaftActorSnapshotCohort;
 105 import org.opendaylight.controller.cluster.raft.RaftState;
 106 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
 107 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
 108 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
 109 import org.opendaylight.controller.cluster.raft.messages.RequestLeadership;
 110 import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
 111 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 112 import org.opendaylight.yangtools.concepts.Identifier;
 113 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
 114 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
 115 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 116 import org.opendaylight.yangtools.yang.model.api.EffectiveModelContext;
 117 import org.opendaylight.yangtools.yang.model.api.EffectiveModelContextProvider;
 118 import scala.concurrent.duration.FiniteDuration;
 119
 120 /**
 121  * A Shard represents a portion of the logical data tree.
 122  *
 123  * <p>
 124  * Our Shard uses InMemoryDataTree as it's internal representation and delegates all requests it
 125  */
 126 public class Shard extends RaftActor {
 127
 128     @VisibleForTesting
 129     static final Object TX_COMMIT_TIMEOUT_CHECK_MESSAGE = new Object() {
 130         @Override
 131         public String toString() {
 132             return "txCommitTimeoutCheck";
 133         }
 134     };
 135
 136     @VisibleForTesting
 137     static final Object GET_SHARD_MBEAN_MESSAGE = new Object() {
 138         @Override
 139         public String toString() {
 140             return "getShardMBeanMessage";
 141         }
 142     };
 143
 144     static final Object RESUME_NEXT_PENDING_TRANSACTION = new Object() {
 145         @Override
 146         public String toString() {
 147             return "resumeNextPendingTransaction";
 148         }
 149     };
 150
 151     // FIXME: shard names should be encapsulated in their own class and this should be exposed as a constant.
 152     public static final String DEFAULT_NAME = "default";
 153
 154     private static final Collection<ABIVersion> SUPPORTED_ABIVERSIONS;
 155
 156     // Make sure to keep this in sync with the journal configuration in factory-akka.conf
 157     public static final String NON_PERSISTENT_JOURNAL_ID = "akka.persistence.non-persistent.journal";
 158
 159     static {
 160         final ABIVersion[] values = ABIVersion.values();
 161         final ABIVersion[] real = Arrays.copyOfRange(values, 1, values.length - 1);
 162         SUPPORTED_ABIVERSIONS = ImmutableList.copyOf(real).reverse();
 163     }
 164
 165     // FIXME: make this a dynamic property based on mailbox size and maximum number of clients
 166     private static final int CLIENT_MAX_MESSAGES = 1000;
 167
 168     // The state of this Shard
 169     private final ShardDataTree store;
 170
 171     /// The name of this shard
 172     private final String name;
 173
 174     private final String shardName;
 175
 176     private final ShardStats shardMBean;
 177
 178     private final ShardDataTreeListenerInfoMXBeanImpl listenerInfoMXBean;
 179
 180     private DatastoreContext datastoreContext;
 181
 182     private final ShardCommitCoordinator commitCoordinator;
 183
 184     private long transactionCommitTimeout;
 185
 186     private Cancellable txCommitTimeoutCheckSchedule;
 187
 188     private final Optional<ActorRef> roleChangeNotifier;
 189
 190     private final MessageTracker appendEntriesReplyTracker;
 191
 192     private final ShardTransactionActorFactory transactionActorFactory;
 193
 194     private final ShardSnapshotCohort snapshotCohort;
 195
 196     private final DataTreeChangeListenerSupport treeChangeSupport = new DataTreeChangeListenerSupport(this);
 197
 198     private ShardSnapshot restoreFromSnapshot;
 199
 200     private final ShardTransactionMessageRetrySupport messageRetrySupport;
 201
 202     @VisibleForTesting
 203     final FrontendMetadata frontendMetadata;
 204
 205     private Map<FrontendIdentifier, LeaderFrontendState> knownFrontends = ImmutableMap.of();
 206     private boolean paused;
 207
 208     private final MessageSlicer responseMessageSlicer;
 209     private final Dispatchers dispatchers;
 210
 211     private final MessageAssembler requestMessageAssembler;
 212
 213     protected Shard(final AbstractBuilder<?, ?> builder) {
 214         super(builder.getId().toString(), builder.getPeerAddresses(),
 215                 Optional.of(builder.getDatastoreContext().getShardRaftConfig()), DataStoreVersions.CURRENT_VERSION);
 216
 217         this.name = builder.getId().toString();
 218         this.shardName = builder.getId().getShardName();
 219         this.datastoreContext = builder.getDatastoreContext();
 220         this.restoreFromSnapshot = builder.getRestoreFromSnapshot();
 221         this.frontendMetadata = new FrontendMetadata(name);
 222
 223         setPersistence(datastoreContext.isPersistent());
 224
 225         LOG.info("Shard created : {}, persistent : {}", name, datastoreContext.isPersistent());
 226
 227         ShardDataTreeChangeListenerPublisherActorProxy treeChangeListenerPublisher =
 228                 new ShardDataTreeChangeListenerPublisherActorProxy(getContext(), name + "-DTCL-publisher", name);
 229         if (builder.getDataTree() != null) {
 230             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getDataTree(),
 231                     treeChangeListenerPublisher, name,
 232                     frontendMetadata);
 233         } else {
 234             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getTreeType(),
 235                     builder.getDatastoreContext().getStoreRoot(), treeChangeListenerPublisher, name,
 236                     frontendMetadata);
 237         }
 238
 239         shardMBean = ShardMBeanFactory.getShardStatsMBean(name, datastoreContext.getDataStoreMXBeanType(), this);
 240
 241         if (isMetricsCaptureEnabled()) {
 242             getContext().become(new MeteringBehavior(this));
 243         }
 244
 245         commitCoordinator = new ShardCommitCoordinator(store, LOG, this.name);
 246
 247         setTransactionCommitTimeout();
 248
 249         // create a notifier actor for each cluster member
 250         roleChangeNotifier = createRoleChangeNotifier(name);
 251
 252         appendEntriesReplyTracker = new MessageTracker(AppendEntriesReply.class,
 253                 getRaftActorContext().getConfigParams().getIsolatedCheckIntervalInMillis());
 254
 255         dispatchers = new Dispatchers(context().system().dispatchers());
 256         transactionActorFactory = new ShardTransactionActorFactory(store, datastoreContext,
 257             dispatchers.getDispatcherPath(Dispatchers.DispatcherType.Transaction),
 258                 self(), getContext(), shardMBean, builder.getId().getShardName());
 259
 260         snapshotCohort = ShardSnapshotCohort.create(getContext(), builder.getId().getMemberName(), store, LOG,
 261             this.name, datastoreContext);
 262
 263         messageRetrySupport = new ShardTransactionMessageRetrySupport(this);
 264
 265         responseMessageSlicer = MessageSlicer.builder().logContext(this.name)
 266                 .messageSliceSize(datastoreContext.getMaximumMessageSliceSize())
 267                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 268                 .expireStateAfterInactivity(2, TimeUnit.MINUTES).build();
 269
 270         requestMessageAssembler = MessageAssembler.builder().logContext(this.name)
 271                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 272                 .assembledMessageCallback((message, sender) -> self().tell(message, sender))
 273                 .expireStateAfterInactivity(datastoreContext.getRequestTimeout(), TimeUnit.NANOSECONDS).build();
 274
 275         listenerInfoMXBean = new ShardDataTreeListenerInfoMXBeanImpl(name, datastoreContext.getDataStoreMXBeanType(),
 276                 self());
 277         listenerInfoMXBean.register();
 278     }
 279
 280     private void setTransactionCommitTimeout() {
 281         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
 282                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS) / 2;
 283     }
 284
 285     private Optional<ActorRef> createRoleChangeNotifier(final String shardId) {
 286         ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
 287             RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
 288         return Optional.of(shardRoleChangeNotifier);
 289     }
 290
 291     @Override
 292     public void postStop() throws Exception {
 293         LOG.info("Stopping Shard {}", persistenceId());
 294
 295         super.postStop();
 296
 297         messageRetrySupport.close();
 298
 299         if (txCommitTimeoutCheckSchedule != null) {
 300             txCommitTimeoutCheckSchedule.cancel();
 301         }
 302
 303         commitCoordinator.abortPendingTransactions("Transaction aborted due to shutdown.", this);
 304
 305         shardMBean.unregisterMBean();
 306         listenerInfoMXBean.unregister();
 307     }
 308
 309     @Override
 310     protected void handleRecover(final Object message) {
 311         LOG.debug("{}: onReceiveRecover: Received message {} from {}", persistenceId(), message.getClass(),
 312             getSender());
 313
 314         super.handleRecover(message);
 315         if (LOG.isTraceEnabled()) {
 316             appendEntriesReplyTracker.begin();
 317         }
 318     }
 319
 320     @Override
 321     protected void handleNonRaftCommand(final Object message) {
 322         try (MessageTracker.Context context = appendEntriesReplyTracker.received(message)) {
 323             final Optional<Error> maybeError = context.error();
 324             if (maybeError.isPresent()) {
 325                 LOG.trace("{} : AppendEntriesReply failed to arrive at the expected interval {}", persistenceId(),
 326                     maybeError.get());
 327             }
 328
 329             store.resetTransactionBatch();
 330
 331             if (message instanceof RequestEnvelope) {
 332                 handleRequestEnvelope((RequestEnvelope)message);
 333             } else if (MessageAssembler.isHandledMessage(message)) {
 334                 handleRequestAssemblerMessage(message);
 335             } else if (message instanceof ConnectClientRequest) {
 336                 handleConnectClient((ConnectClientRequest)message);
 337             } else if (CreateTransaction.isSerializedType(message)) {
 338                 handleCreateTransaction(message);
 339             } else if (message instanceof BatchedModifications) {
 340                 handleBatchedModifications((BatchedModifications)message);
 341             } else if (message instanceof ForwardedReadyTransaction) {
 342                 handleForwardedReadyTransaction((ForwardedReadyTransaction) message);
 343             } else if (message instanceof ReadyLocalTransaction) {
 344                 handleReadyLocalTransaction((ReadyLocalTransaction)message);
 345             } else if (CanCommitTransaction.isSerializedType(message)) {
 346                 handleCanCommitTransaction(CanCommitTransaction.fromSerializable(message));
 347             } else if (CommitTransaction.isSerializedType(message)) {
 348                 handleCommitTransaction(CommitTransaction.fromSerializable(message));
 349             } else if (AbortTransaction.isSerializedType(message)) {
 350                 handleAbortTransaction(AbortTransaction.fromSerializable(message));
 351             } else if (CloseTransactionChain.isSerializedType(message)) {
 352                 closeTransactionChain(CloseTransactionChain.fromSerializable(message));
 353             } else if (message instanceof DataTreeChangedReply) {
 354                 // Ignore reply
 355             } else if (message instanceof RegisterDataTreeChangeListener) {
 356                 treeChangeSupport.onMessage((RegisterDataTreeChangeListener) message, isLeader(), hasLeader());
 357             } else if (message instanceof UpdateSchemaContext) {
 358                 updateSchemaContext((UpdateSchemaContext) message);
 359             } else if (message instanceof PeerAddressResolved) {
 360                 PeerAddressResolved resolved = (PeerAddressResolved) message;
 361                 setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
 362             } else if (TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
 363                 commitTimeoutCheck();
 364             } else if (message instanceof DatastoreContext) {
 365                 onDatastoreContext((DatastoreContext)message);
 366             } else if (message instanceof RegisterRoleChangeListener) {
 367                 roleChangeNotifier.get().forward(message, context());
 368             } else if (message instanceof FollowerInitialSyncUpStatus) {
 369                 shardMBean.setFollowerInitialSyncStatus(((FollowerInitialSyncUpStatus) message).isInitialSyncDone());
 370                 context().parent().tell(message, self());
 371             } else if (GET_SHARD_MBEAN_MESSAGE.equals(message)) {
 372                 sender().tell(getShardMBean(), self());
 373             } else if (message instanceof GetShardDataTree) {
 374                 sender().tell(store.getDataTree(), self());
 375             } else if (message instanceof ServerRemoved) {
 376                 context().parent().forward(message, context());
 377             } else if (ShardTransactionMessageRetrySupport.TIMER_MESSAGE_CLASS.isInstance(message)) {
 378                 messageRetrySupport.onTimerMessage(message);
 379             } else if (message instanceof DataTreeCohortActorRegistry.CohortRegistryCommand) {
 380                 store.processCohortRegistryCommand(getSender(),
 381                         (DataTreeCohortActorRegistry.CohortRegistryCommand) message);
 382             } else if (message instanceof MakeLeaderLocal) {
 383                 onMakeLeaderLocal();
 384             } else if (RESUME_NEXT_PENDING_TRANSACTION.equals(message)) {
 385                 store.resumeNextPendingTransaction();
 386             } else if (GetKnownClients.INSTANCE.equals(message)) {
 387                 handleGetKnownClients();
 388             } else if (!responseMessageSlicer.handleMessage(message)) {
 389                 super.handleNonRaftCommand(message);
 390             }
 391         }
 392     }
 393
 394     private void handleRequestAssemblerMessage(final Object message) {
 395         dispatchers.getDispatcher(DispatcherType.Serialization).execute(() -> {
 396             JavaSerializer.currentSystem().value_$eq((ExtendedActorSystem) context().system());
 397             requestMessageAssembler.handleMessage(message, self());
 398         });
 399     }
 400
 401     @SuppressWarnings("checkstyle:IllegalCatch")
 402     private void handleRequestEnvelope(final RequestEnvelope envelope) {
 403         final long now = ticker().read();
 404         try {
 405             final RequestSuccess<?, ?> success = handleRequest(envelope, now);
 406             if (success != null) {
 407                 final long executionTimeNanos = ticker().read() - now;
 408                 if (success instanceof SliceableMessage) {
 409                     dispatchers.getDispatcher(DispatcherType.Serialization).execute(() ->
 410                         responseMessageSlicer.slice(SliceOptions.builder().identifier(success.getTarget())
 411                             .message(envelope.newSuccessEnvelope(success, executionTimeNanos))
 412                             .sendTo(envelope.getMessage().getReplyTo()).replyTo(self())
 413                             .onFailureCallback(t -> LOG.warn("Error slicing response {}", success, t)).build()));
 414                 } else {
 415                     envelope.sendSuccess(success, executionTimeNanos);
 416                 }
 417             }
 418         } catch (RequestException e) {
 419             LOG.debug("{}: request {} failed", persistenceId(), envelope, e);
 420             envelope.sendFailure(e, ticker().read() - now);
 421         } catch (Exception e) {
 422             LOG.debug("{}: request {} caused failure", persistenceId(), envelope, e);
 423             envelope.sendFailure(new RuntimeRequestException("Request failed to process", e),
 424                 ticker().read() - now);
 425         }
 426     }
 427
 428     private void commitTimeoutCheck() {
 429         store.checkForExpiredTransactions(transactionCommitTimeout, this::updateAccess);
 430         commitCoordinator.checkForExpiredTransactions(transactionCommitTimeout, this);
 431         requestMessageAssembler.checkExpiredAssembledMessageState();
 432     }
 433
 434     private OptionalLong updateAccess(final SimpleShardDataTreeCohort cohort) {
 435         final FrontendIdentifier frontend = cohort.getIdentifier().getHistoryId().getClientId().getFrontendId();
 436         final LeaderFrontendState state = knownFrontends.get(frontend);
 437         if (state == null) {
 438             // Not tell-based protocol, do nothing
 439             return OptionalLong.empty();
 440         }
 441
 442         if (isIsolatedLeader()) {
 443             // We are isolated and no new request can come through until we emerge from it. We are still updating
 444             // liveness of frontend when we see it attempting to communicate. Use the last access timer.
 445             return OptionalLong.of(state.getLastSeenTicks());
 446         }
 447
 448         // If this frontend has freshly connected, give it some time to catch up before killing its transactions.
 449         return OptionalLong.of(state.getLastConnectTicks());
 450     }
 451
 452     private void disableTracking(final DisableTrackingPayload payload) {
 453         final ClientIdentifier clientId = payload.getIdentifier();
 454         LOG.debug("{}: disabling tracking of {}", persistenceId(), clientId);
 455         frontendMetadata.disableTracking(clientId);
 456
 457         if (isLeader()) {
 458             final FrontendIdentifier frontendId = clientId.getFrontendId();
 459             final LeaderFrontendState frontend = knownFrontends.get(frontendId);
 460             if (frontend != null) {
 461                 if (clientId.equals(frontend.getIdentifier())) {
 462                     if (!(frontend instanceof LeaderFrontendState.Disabled)) {
 463                         verify(knownFrontends.replace(frontendId, frontend,
 464                             new LeaderFrontendState.Disabled(persistenceId(), clientId, store)));
 465                         LOG.debug("{}: leader state for {} disabled", persistenceId(), clientId);
 466                     } else {
 467                         LOG.debug("{}: leader state {} is already disabled", persistenceId(), frontend);
 468                     }
 469                 } else {
 470                     LOG.debug("{}: leader state {} does not match {}", persistenceId(), frontend, clientId);
 471                 }
 472             } else {
 473                 LOG.debug("{}: leader state for {} not found", persistenceId(), clientId);
 474                 knownFrontends.put(frontendId, new LeaderFrontendState.Disabled(persistenceId(), clientId,
 475                     getDataStore()));
 476             }
 477         }
 478     }
 479
 480     private void onMakeLeaderLocal() {
 481         LOG.debug("{}: onMakeLeaderLocal received", persistenceId());
 482         if (isLeader()) {
 483             getSender().tell(new Status.Success(null), getSelf());
 484             return;
 485         }
 486
 487         final ActorSelection leader = getLeader();
 488
 489         if (leader == null) {
 490             // Leader is not present. The cluster is most likely trying to
 491             // elect a leader and we should let that run its normal course
 492
 493             // TODO we can wait for the election to complete and retry the
 494             // request. We can also let the caller retry by sending a flag
 495             // in the response indicating the request is "reTryable".
 496             getSender().tell(new Failure(
 497                     new LeadershipTransferFailedException("We cannot initiate leadership transfer to local node. "
 498                             + "Currently there is no leader for " + persistenceId())),
 499                     getSelf());
 500             return;
 501         }
 502
 503         leader.tell(new RequestLeadership(getId(), getSender()), getSelf());
 504     }
 505
 506     // Acquire our frontend tracking handle and verify generation matches
 507     private @Nullable LeaderFrontendState findFrontend(final ClientIdentifier clientId) throws RequestException {
 508         final LeaderFrontendState existing = knownFrontends.get(clientId.getFrontendId());
 509         if (existing != null) {
 510             final int cmp = Long.compareUnsigned(existing.getIdentifier().getGeneration(), clientId.getGeneration());
 511             if (cmp == 0) {
 512                 existing.touch();
 513                 return existing;
 514             }
 515             if (cmp > 0) {
 516                 LOG.debug("{}: rejecting request from outdated client {}", persistenceId(), clientId);
 517                 throw new RetiredGenerationException(clientId.getGeneration(),
 518                     existing.getIdentifier().getGeneration());
 519             }
 520
 521             LOG.info("{}: retiring state {}, outdated by request from client {}", persistenceId(), existing, clientId);
 522             existing.retire();
 523             knownFrontends.remove(clientId.getFrontendId());
 524         } else {
 525             LOG.debug("{}: client {} is not yet known", persistenceId(), clientId);
 526         }
 527
 528         return null;
 529     }
 530
 531     private LeaderFrontendState getFrontend(final ClientIdentifier clientId) throws RequestException {
 532         final LeaderFrontendState ret = findFrontend(clientId);
 533         if (ret != null) {
 534             return ret;
 535         }
 536
 537         // TODO: a dedicated exception would be better, but this is technically true, too
 538         throw new OutOfSequenceEnvelopeException(0);
 539     }
 540
 541     private static @NonNull ABIVersion selectVersion(final ConnectClientRequest message) {
 542         final Range<ABIVersion> clientRange = Range.closed(message.getMinVersion(), message.getMaxVersion());
 543         for (ABIVersion v : SUPPORTED_ABIVERSIONS) {
 544             if (clientRange.contains(v)) {
 545                 return v;
 546             }
 547         }
 548
 549         throw new IllegalArgumentException(String.format(
 550             "No common version between backend versions %s and client versions %s", SUPPORTED_ABIVERSIONS,
 551             clientRange));
 552     }
 553
 554     @SuppressWarnings("checkstyle:IllegalCatch")
 555     private void handleConnectClient(final ConnectClientRequest message) {
 556         try {
 557             final ClientIdentifier clientId = message.getTarget();
 558             final LeaderFrontendState existing = findFrontend(clientId);
 559             if (existing != null) {
 560                 existing.touch();
 561             }
 562
 563             if (!isLeader() || !isLeaderActive()) {
 564                 LOG.info("{}: not currently leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 565                                 + "isLeadershipTransferInProgress: {}.",
 566                         persistenceId(), message, isLeader(), isLeaderActive(), isLeadershipTransferInProgress());
 567                 throw new NotLeaderException(getSelf());
 568             }
 569
 570             final ABIVersion selectedVersion = selectVersion(message);
 571             final LeaderFrontendState frontend;
 572             if (existing == null) {
 573                 frontend = new LeaderFrontendState.Enabled(persistenceId(), clientId, store);
 574                 knownFrontends.put(clientId.getFrontendId(), frontend);
 575                 LOG.debug("{}: created state {} for client {}", persistenceId(), frontend, clientId);
 576             } else {
 577                 frontend = existing;
 578             }
 579
 580             frontend.reconnect();
 581             message.getReplyTo().tell(new ConnectClientSuccess(message.getTarget(), message.getSequence(), getSelf(),
 582                 ImmutableList.of(), store.getDataTree(), CLIENT_MAX_MESSAGES).toVersion(selectedVersion),
 583                 ActorRef.noSender());
 584         } catch (RequestException | RuntimeException e) {
 585             message.getReplyTo().tell(new Failure(e), ActorRef.noSender());
 586         }
 587     }
 588
 589     private @Nullable RequestSuccess<?, ?> handleRequest(final RequestEnvelope envelope, final long now)
 590             throws RequestException {
 591         // We are not the leader, hence we want to fail-fast.
 592         if (!isLeader() || paused || !isLeaderActive()) {
 593             LOG.debug("{}: not currently active leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 594                             + "isLeadershipTransferInProgress: {}, paused: {}",
 595                     persistenceId(), envelope, isLeader(), isLeaderActive(), isLeadershipTransferInProgress(), paused);
 596             throw new NotLeaderException(getSelf());
 597         }
 598
 599         final Request<?, ?> request = envelope.getMessage();
 600         if (request instanceof TransactionRequest) {
 601             final TransactionRequest<?> txReq = (TransactionRequest<?>)request;
 602             final ClientIdentifier clientId = txReq.getTarget().getHistoryId().getClientId();
 603             return getFrontend(clientId).handleTransactionRequest(txReq, envelope, now);
 604         } else if (request instanceof LocalHistoryRequest) {
 605             final LocalHistoryRequest<?> lhReq = (LocalHistoryRequest<?>)request;
 606             final ClientIdentifier clientId = lhReq.getTarget().getClientId();
 607             return getFrontend(clientId).handleLocalHistoryRequest(lhReq, envelope, now);
 608         } else {
 609             LOG.warn("{}: rejecting unsupported request {}", persistenceId(), request);
 610             throw new UnsupportedRequestException(request);
 611         }
 612     }
 613
 614     private void handleGetKnownClients() {
 615         final ImmutableSet<ClientIdentifier> clients;
 616         if (isLeader()) {
 617             clients = knownFrontends.values().stream()
 618                     .map(LeaderFrontendState::getIdentifier)
 619                     .collect(ImmutableSet.toImmutableSet());
 620         } else {
 621             clients = frontendMetadata.getClients();
 622         }
 623         sender().tell(new GetKnownClientsReply(clients), self());
 624     }
 625
 626     private boolean hasLeader() {
 627         return getLeaderId() != null;
 628     }
 629
 630     public int getPendingTxCommitQueueSize() {
 631         return store.getQueueSize();
 632     }
 633
 634     public int getCohortCacheSize() {
 635         return commitCoordinator.getCohortCacheSize();
 636     }
 637
 638     @Override
 639     protected Optional<ActorRef> getRoleChangeNotifier() {
 640         return roleChangeNotifier;
 641     }
 642
 643     String getShardName() {
 644         return shardName;
 645     }
 646
 647     @Override
 648     protected LeaderStateChanged newLeaderStateChanged(final String memberId, final String leaderId,
 649             final short leaderPayloadVersion) {
 650         return isLeader() ? new ShardLeaderStateChanged(memberId, leaderId, store.getDataTree(), leaderPayloadVersion)
 651                 : new ShardLeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 652     }
 653
 654     protected void onDatastoreContext(final DatastoreContext context) {
 655         datastoreContext = verifyNotNull(context);
 656
 657         setTransactionCommitTimeout();
 658
 659         setPersistence(datastoreContext.isPersistent());
 660
 661         updateConfigParams(datastoreContext.getShardRaftConfig());
 662     }
 663
 664     // applyState() will be invoked once consensus is reached on the payload
 665     void persistPayload(final Identifier id, final Payload payload, final boolean batchHint) {
 666         boolean canSkipPayload = !hasFollowers() && !persistence().isRecoveryApplicable();
 667         if (canSkipPayload) {
 668             applyState(self(), id, payload);
 669         } else {
 670             // We are faking the sender
 671             persistData(self(), id, payload, batchHint);
 672         }
 673     }
 674
 675     private void handleCommitTransaction(final CommitTransaction commit) {
 676         final TransactionIdentifier txId = commit.getTransactionId();
 677         if (isLeader()) {
 678             askProtocolEncountered(txId);
 679             commitCoordinator.handleCommit(txId, getSender(), this);
 680         } else {
 681             ActorSelection leader = getLeader();
 682             if (leader == null) {
 683                 messageRetrySupport.addMessageToRetry(commit, getSender(), "Could not commit transaction " + txId);
 684             } else {
 685                 LOG.debug("{}: Forwarding CommitTransaction to leader {}", persistenceId(), leader);
 686                 leader.forward(commit, getContext());
 687             }
 688         }
 689     }
 690
 691     private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
 692         final TransactionIdentifier txId = canCommit.getTransactionId();
 693         LOG.debug("{}: Can committing transaction {}", persistenceId(), txId);
 694
 695         if (isLeader()) {
 696             askProtocolEncountered(txId);
 697             commitCoordinator.handleCanCommit(txId, getSender(), this);
 698         } else {
 699             ActorSelection leader = getLeader();
 700             if (leader == null) {
 701                 messageRetrySupport.addMessageToRetry(canCommit, getSender(),
 702                         "Could not canCommit transaction " + txId);
 703             } else {
 704                 LOG.debug("{}: Forwarding CanCommitTransaction to leader {}", persistenceId(), leader);
 705                 leader.forward(canCommit, getContext());
 706             }
 707         }
 708     }
 709
 710     @SuppressWarnings("checkstyle:IllegalCatch")
 711     protected void handleBatchedModificationsLocal(final BatchedModifications batched, final ActorRef sender) {
 712         askProtocolEncountered(batched.getTransactionId());
 713
 714         try {
 715             commitCoordinator.handleBatchedModifications(batched, sender, this);
 716         } catch (Exception e) {
 717             LOG.error("{}: Error handling BatchedModifications for Tx {}", persistenceId(),
 718                     batched.getTransactionId(), e);
 719             sender.tell(new Failure(e), getSelf());
 720         }
 721     }
 722
 723     private void handleBatchedModifications(final BatchedModifications batched) {
 724         // This message is sent to prepare the modifications transaction directly on the Shard as an
 725         // optimization to avoid the extra overhead of a separate ShardTransaction actor. On the last
 726         // BatchedModifications message, the caller sets the ready flag in the message indicating
 727         // modifications are complete. The reply contains the cohort actor path (this actor) for the caller
 728         // to initiate the 3-phase commit. This also avoids the overhead of sending an additional
 729         // ReadyTransaction message.
 730
 731         // If we're not the leader then forward to the leader. This is a safety measure - we shouldn't
 732         // normally get here if we're not the leader as the front-end (TransactionProxy) should determine
 733         // the primary/leader shard. However with timing and caching on the front-end, there's a small
 734         // window where it could have a stale leader during leadership transitions.
 735         //
 736         boolean isLeaderActive = isLeaderActive();
 737         if (isLeader() && isLeaderActive) {
 738             handleBatchedModificationsLocal(batched, getSender());
 739         } else {
 740             ActorSelection leader = getLeader();
 741             if (!isLeaderActive || leader == null) {
 742                 messageRetrySupport.addMessageToRetry(batched, getSender(),
 743                         "Could not process BatchedModifications " + batched.getTransactionId());
 744             } else {
 745                 // If this is not the first batch and leadership changed in between batched messages,
 746                 // we need to reconstruct previous BatchedModifications from the transaction
 747                 // DataTreeModification, honoring the max batched modification count, and forward all the
 748                 // previous BatchedModifications to the new leader.
 749                 Collection<BatchedModifications> newModifications = commitCoordinator
 750                         .createForwardedBatchedModifications(batched,
 751                                 datastoreContext.getShardBatchedModificationCount());
 752
 753                 LOG.debug("{}: Forwarding {} BatchedModifications to leader {}", persistenceId(),
 754                         newModifications.size(), leader);
 755
 756                 for (BatchedModifications bm : newModifications) {
 757                     leader.forward(bm, getContext());
 758                 }
 759             }
 760         }
 761     }
 762
 763     private boolean failIfIsolatedLeader(final ActorRef sender) {
 764         if (isIsolatedLeader()) {
 765             sender.tell(new Failure(new NoShardLeaderException(String.format(
 766                     "Shard %s was the leader but has lost contact with all of its followers. Either all"
 767                     + " other follower nodes are down or this node is isolated by a network partition.",
 768                     persistenceId()))), getSelf());
 769             return true;
 770         }
 771
 772         return false;
 773     }
 774
 775     protected boolean isIsolatedLeader() {
 776         return getRaftState() == RaftState.IsolatedLeader;
 777     }
 778
 779     @SuppressWarnings("checkstyle:IllegalCatch")
 780     private void handleReadyLocalTransaction(final ReadyLocalTransaction message) {
 781         LOG.debug("{}: handleReadyLocalTransaction for {}", persistenceId(), message.getTransactionId());
 782
 783         boolean isLeaderActive = isLeaderActive();
 784         if (isLeader() && isLeaderActive) {
 785             try {
 786                 commitCoordinator.handleReadyLocalTransaction(message, getSender(), this);
 787             } catch (Exception e) {
 788                 LOG.error("{}: Error handling ReadyLocalTransaction for Tx {}", persistenceId(),
 789                         message.getTransactionId(), e);
 790                 getSender().tell(new Failure(e), getSelf());
 791             }
 792         } else {
 793             ActorSelection leader = getLeader();
 794             if (!isLeaderActive || leader == null) {
 795                 messageRetrySupport.addMessageToRetry(message, getSender(),
 796                         "Could not process ready local transaction " + message.getTransactionId());
 797             } else {
 798                 LOG.debug("{}: Forwarding ReadyLocalTransaction to leader {}", persistenceId(), leader);
 799                 message.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 800                 leader.forward(message, getContext());
 801             }
 802         }
 803     }
 804
 805     private void handleForwardedReadyTransaction(final ForwardedReadyTransaction forwardedReady) {
 806         LOG.debug("{}: handleForwardedReadyTransaction for {}", persistenceId(), forwardedReady.getTransactionId());
 807
 808         boolean isLeaderActive = isLeaderActive();
 809         if (isLeader() && isLeaderActive) {
 810             askProtocolEncountered(forwardedReady.getTransactionId());
 811             commitCoordinator.handleForwardedReadyTransaction(forwardedReady, getSender(), this);
 812         } else {
 813             ActorSelection leader = getLeader();
 814             if (!isLeaderActive || leader == null) {
 815                 messageRetrySupport.addMessageToRetry(forwardedReady, getSender(),
 816                         "Could not process forwarded ready transaction " + forwardedReady.getTransactionId());
 817             } else {
 818                 LOG.debug("{}: Forwarding ForwardedReadyTransaction to leader {}", persistenceId(), leader);
 819
 820                 ReadyLocalTransaction readyLocal = new ReadyLocalTransaction(forwardedReady.getTransactionId(),
 821                         forwardedReady.getTransaction().getSnapshot(), forwardedReady.isDoImmediateCommit(),
 822                         forwardedReady.getParticipatingShardNames());
 823                 readyLocal.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 824                 leader.forward(readyLocal, getContext());
 825             }
 826         }
 827     }
 828
 829     private void handleAbortTransaction(final AbortTransaction abort) {
 830         final TransactionIdentifier transactionId = abort.getTransactionId();
 831         askProtocolEncountered(transactionId);
 832         doAbortTransaction(transactionId, getSender());
 833     }
 834
 835     void doAbortTransaction(final Identifier transactionID, final ActorRef sender) {
 836         commitCoordinator.handleAbort(transactionID, sender, this);
 837     }
 838
 839     private void handleCreateTransaction(final Object message) {
 840         if (isLeader()) {
 841             createTransaction(CreateTransaction.fromSerializable(message));
 842         } else if (getLeader() != null) {
 843             getLeader().forward(message, getContext());
 844         } else {
 845             getSender().tell(new Failure(new NoShardLeaderException(
 846                     "Could not create a shard transaction", persistenceId())), getSelf());
 847         }
 848     }
 849
 850     private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
 851         if (isLeader()) {
 852             final LocalHistoryIdentifier id = closeTransactionChain.getIdentifier();
 853             askProtocolEncountered(id.getClientId());
 854             store.closeTransactionChain(id);
 855         } else if (getLeader() != null) {
 856             getLeader().forward(closeTransactionChain, getContext());
 857         } else {
 858             LOG.warn("{}: Could not close transaction {}", persistenceId(), closeTransactionChain.getIdentifier());
 859         }
 860     }
 861
 862     @SuppressWarnings("checkstyle:IllegalCatch")
 863     private void createTransaction(final CreateTransaction createTransaction) {
 864         askProtocolEncountered(createTransaction.getTransactionId());
 865
 866         try {
 867             if (TransactionType.fromInt(createTransaction.getTransactionType()) != TransactionType.READ_ONLY
 868                     && failIfIsolatedLeader(getSender())) {
 869                 return;
 870             }
 871
 872             ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
 873                 createTransaction.getTransactionId());
 874
 875             getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
 876                     createTransaction.getTransactionId(), createTransaction.getVersion()).toSerializable(), getSelf());
 877         } catch (Exception e) {
 878             getSender().tell(new Failure(e), getSelf());
 879         }
 880     }
 881
 882     private ActorRef createTransaction(final int transactionType, final TransactionIdentifier transactionId) {
 883         LOG.debug("{}: Creating transaction : {} ", persistenceId(), transactionId);
 884         return transactionActorFactory.newShardTransaction(TransactionType.fromInt(transactionType),
 885             transactionId);
 886     }
 887
 888     // Called on leader only
 889     private void askProtocolEncountered(final TransactionIdentifier transactionId) {
 890         askProtocolEncountered(transactionId.getHistoryId().getClientId());
 891     }
 892
 893     // Called on leader only
 894     private void askProtocolEncountered(final ClientIdentifier clientId) {
 895         final FrontendIdentifier frontend = clientId.getFrontendId();
 896         final LeaderFrontendState state = knownFrontends.get(frontend);
 897         if (!(state instanceof LeaderFrontendState.Disabled)) {
 898             LOG.debug("{}: encountered ask-based client {}, disabling transaction tracking", persistenceId(), clientId);
 899             if (knownFrontends.isEmpty()) {
 900                 knownFrontends = new HashMap<>();
 901             }
 902             knownFrontends.put(frontend, new LeaderFrontendState.Disabled(persistenceId(), clientId, getDataStore()));
 903
 904             persistPayload(clientId, DisableTrackingPayload.create(clientId,
 905                 datastoreContext.getInitialPayloadSerializedBufferCapacity()), false);
 906         }
 907     }
 908
 909     private void updateSchemaContext(final UpdateSchemaContext message) {
 910         updateSchemaContext(message.getEffectiveModelContext());
 911     }
 912
 913     @VisibleForTesting
 914     void updateSchemaContext(final @NonNull EffectiveModelContext schemaContext) {
 915         store.updateSchemaContext(schemaContext);
 916     }
 917
 918     private boolean isMetricsCaptureEnabled() {
 919         CommonConfig config = new CommonConfig(getContext().system().settings().config());
 920         return config.isMetricCaptureEnabled();
 921     }
 922
 923     @Override
 924     @VisibleForTesting
 925     public RaftActorSnapshotCohort getRaftActorSnapshotCohort() {
 926         return snapshotCohort;
 927     }
 928
 929     @Override
 930     protected RaftActorRecoveryCohort getRaftActorRecoveryCohort() {
 931         if (restoreFromSnapshot == null) {
 932             return ShardRecoveryCoordinator.create(store, persistenceId(), LOG);
 933         }
 934
 935         return ShardRecoveryCoordinator.forSnapshot(store, persistenceId(), LOG, restoreFromSnapshot.getSnapshot());
 936     }
 937
 938     @Override
 939     protected void onRecoveryComplete() {
 940         restoreFromSnapshot = null;
 941
 942         //notify shard manager
 943         getContext().parent().tell(new ActorInitialized(), getSelf());
 944
 945         // Being paranoid here - this method should only be called once but just in case...
 946         if (txCommitTimeoutCheckSchedule == null) {
 947             // Schedule a message to be periodically sent to check if the current in-progress
 948             // transaction should be expired and aborted.
 949             FiniteDuration period = FiniteDuration.create(transactionCommitTimeout / 3, TimeUnit.MILLISECONDS);
 950             txCommitTimeoutCheckSchedule = getContext().system().scheduler().schedule(
 951                     period, period, getSelf(),
 952                     TX_COMMIT_TIMEOUT_CHECK_MESSAGE, getContext().dispatcher(), ActorRef.noSender());
 953         }
 954     }
 955
 956     @Override
 957     protected void applyState(final ActorRef clientActor, final Identifier identifier, final Object data) {
 958         if (data instanceof Payload) {
 959             if (data instanceof DisableTrackingPayload) {
 960                 disableTracking((DisableTrackingPayload) data);
 961                 return;
 962             }
 963
 964             try {
 965                 store.applyReplicatedPayload(identifier, (Payload)data);
 966             } catch (DataValidationFailedException | IOException e) {
 967                 LOG.error("{}: Error applying replica {}", persistenceId(), identifier, e);
 968             }
 969         } else {
 970             LOG.error("{}: Unknown state for {} received {}", persistenceId(), identifier, data);
 971         }
 972     }
 973
 974     @Override
 975     protected void onStateChanged() {
 976         boolean isLeader = isLeader();
 977         boolean hasLeader = hasLeader();
 978         treeChangeSupport.onLeadershipChange(isLeader, hasLeader);
 979
 980         // If this actor is no longer the leader close all the transaction chains
 981         if (!isLeader) {
 982             if (LOG.isDebugEnabled()) {
 983                 LOG.debug(
 984                     "{}: onStateChanged: Closing all transaction chains because shard {} is no longer the leader",
 985                     persistenceId(), getId());
 986             }
 987
 988             paused = false;
 989             store.purgeLeaderState();
 990         }
 991
 992         if (hasLeader && !isIsolatedLeader()) {
 993             messageRetrySupport.retryMessages();
 994         }
 995     }
 996
 997     @Override
 998     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 999         shardMBean.incrementLeadershipChangeCount();
1000         paused = false;
1001
1002         if (!isLeader()) {
1003             if (!knownFrontends.isEmpty()) {
1004                 LOG.debug("{}: removing frontend state for {}", persistenceId(), knownFrontends.keySet());
1005                 knownFrontends = ImmutableMap.of();
1006             }
1007
1008             requestMessageAssembler.close();
1009
1010             if (!hasLeader()) {
1011                 // No leader anywhere, nothing else to do
1012                 return;
1013             }
1014
1015             // Another leader was elected. If we were the previous leader and had pending transactions, convert
1016             // them to transaction messages and send to the new leader.
1017             ActorSelection leader = getLeader();
1018             if (leader != null) {
1019                 Collection<?> messagesToForward = convertPendingTransactionsToMessages();
1020
1021                 if (!messagesToForward.isEmpty()) {
1022                     LOG.debug("{}: Forwarding {} pending transaction messages to leader {}", persistenceId(),
1023                             messagesToForward.size(), leader);
1024
1025                     for (Object message : messagesToForward) {
1026                         LOG.debug("{}: Forwarding pending transaction message {}", persistenceId(), message);
1027
1028                         leader.tell(message, self());
1029                     }
1030                 }
1031             } else {
1032                 commitCoordinator.abortPendingTransactions("The transacton was aborted due to inflight leadership "
1033                         + "change and the leader address isn't available.", this);
1034             }
1035         } else {
1036             // We have become the leader, we need to reconstruct frontend state
1037             knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
1038             LOG.debug("{}: became leader with frontend state for {}", persistenceId(), knownFrontends.keySet());
1039         }
1040
1041         if (!isIsolatedLeader()) {
1042             messageRetrySupport.retryMessages();
1043         }
1044     }
1045
1046     /**
1047      * Clears all pending transactions and converts them to messages to be forwarded to a new leader.
1048      *
1049      * @return the converted messages
1050      */
1051     public Collection<?> convertPendingTransactionsToMessages() {
1052         return commitCoordinator.convertPendingTransactionsToMessages(
1053                 datastoreContext.getShardBatchedModificationCount());
1054     }
1055
1056     @Override
1057     protected void pauseLeader(final Runnable operation) {
1058         LOG.debug("{}: In pauseLeader, operation: {}", persistenceId(), operation);
1059         paused = true;
1060
1061         // Tell-based protocol can replay transaction state, so it is safe to blow it up when we are paused.
1062         if (datastoreContext.isUseTellBasedProtocol()) {
1063             knownFrontends.values().forEach(LeaderFrontendState::retire);
1064             knownFrontends = ImmutableMap.of();
1065         }
1066
1067         store.setRunOnPendingTransactionsComplete(operation);
1068     }
1069
1070     @Override
1071     protected void unpauseLeader() {
1072         LOG.debug("{}: In unpauseLeader", persistenceId());
1073         paused = false;
1074
1075         store.setRunOnPendingTransactionsComplete(null);
1076
1077         // Restore tell-based protocol state as if we were becoming the leader
1078         knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
1079     }
1080
1081     @Override
1082     protected OnDemandRaftState.AbstractBuilder<?, ?> newOnDemandRaftStateBuilder() {
1083         return OnDemandShardState.newBuilder().treeChangeListenerActors(treeChangeSupport.getListenerActors())
1084                 .commitCohortActors(store.getCohortActors());
1085     }
1086
1087     @Override
1088     public String persistenceId() {
1089         return this.name;
1090     }
1091
1092     @Override
1093     public String journalPluginId() {
1094         // This method may be invoked from super constructor (wonderful), hence we also need to handle the case of
1095         // the field being uninitialized because our constructor is not finished.
1096         if (datastoreContext != null && !datastoreContext.isPersistent()) {
1097             return NON_PERSISTENT_JOURNAL_ID;
1098         }
1099         return super.journalPluginId();
1100     }
1101
1102     @VisibleForTesting
1103     ShardCommitCoordinator getCommitCoordinator() {
1104         return commitCoordinator;
1105     }
1106
1107     public DatastoreContext getDatastoreContext() {
1108         return datastoreContext;
1109     }
1110
1111     @VisibleForTesting
1112     public ShardDataTree getDataStore() {
1113         return store;
1114     }
1115
1116     @VisibleForTesting
1117     ShardStats getShardMBean() {
1118         return shardMBean;
1119     }
1120
1121     public static Builder builder() {
1122         return new Builder();
1123     }
1124
1125     public abstract static class AbstractBuilder<T extends AbstractBuilder<T, S>, S extends Shard> {
1126         private final Class<? extends S> shardClass;
1127         private ShardIdentifier id;
1128         private Map<String, String> peerAddresses = Collections.emptyMap();
1129         private DatastoreContext datastoreContext;
1130         private EffectiveModelContextProvider schemaContextProvider;
1131         private DatastoreSnapshot.ShardSnapshot restoreFromSnapshot;
1132         private DataTree dataTree;
1133
1134         private volatile boolean sealed;
1135
1136         protected AbstractBuilder(final Class<? extends S> shardClass) {
1137             this.shardClass = shardClass;
1138         }
1139
1140         protected void checkSealed() {
1141             checkState(!sealed, "Builder isalready sealed - further modifications are not allowed");
1142         }
1143
1144         @SuppressWarnings("unchecked")
1145         private T self() {
1146             return (T) this;
1147         }
1148
1149         public T id(final ShardIdentifier newId) {
1150             checkSealed();
1151             this.id = newId;
1152             return self();
1153         }
1154
1155         public T peerAddresses(final Map<String, String> newPeerAddresses) {
1156             checkSealed();
1157             this.peerAddresses = newPeerAddresses;
1158             return self();
1159         }
1160
1161         public T datastoreContext(final DatastoreContext newDatastoreContext) {
1162             checkSealed();
1163             this.datastoreContext = newDatastoreContext;
1164             return self();
1165         }
1166
1167         public T schemaContextProvider(final EffectiveModelContextProvider newSchemaContextProvider) {
1168             checkSealed();
1169             this.schemaContextProvider = requireNonNull(newSchemaContextProvider);
1170             return self();
1171         }
1172
1173         public T restoreFromSnapshot(final DatastoreSnapshot.ShardSnapshot newRestoreFromSnapshot) {
1174             checkSealed();
1175             this.restoreFromSnapshot = newRestoreFromSnapshot;
1176             return self();
1177         }
1178
1179         public T dataTree(final DataTree newDataTree) {
1180             checkSealed();
1181             this.dataTree = newDataTree;
1182             return self();
1183         }
1184
1185         public ShardIdentifier getId() {
1186             return id;
1187         }
1188
1189         public Map<String, String> getPeerAddresses() {
1190             return peerAddresses;
1191         }
1192
1193         public DatastoreContext getDatastoreContext() {
1194             return datastoreContext;
1195         }
1196
1197         public EffectiveModelContext getSchemaContext() {
1198             return Verify.verifyNotNull(schemaContextProvider.getEffectiveModelContext());
1199         }
1200
1201         public DatastoreSnapshot.ShardSnapshot getRestoreFromSnapshot() {
1202             return restoreFromSnapshot;
1203         }
1204
1205         public DataTree getDataTree() {
1206             return dataTree;
1207         }
1208
1209         public TreeType getTreeType() {
1210             switch (datastoreContext.getLogicalStoreType()) {
1211                 case CONFIGURATION:
1212                     return TreeType.CONFIGURATION;
1213                 case OPERATIONAL:
1214                     return TreeType.OPERATIONAL;
1215                 default:
1216                     throw new IllegalStateException("Unhandled logical store type "
1217                             + datastoreContext.getLogicalStoreType());
1218             }
1219         }
1220
1221         protected void verify() {
1222             requireNonNull(id, "id should not be null");
1223             requireNonNull(peerAddresses, "peerAddresses should not be null");
1224             requireNonNull(datastoreContext, "dataStoreContext should not be null");
1225             requireNonNull(schemaContextProvider, "schemaContextProvider should not be null");
1226         }
1227
1228         public Props props() {
1229             sealed = true;
1230             verify();
1231             return Props.create(shardClass, this);
1232         }
1233     }
1234
1235     public static class Builder extends AbstractBuilder<Builder, Shard> {
1236         Builder() {
1237             this(Shard.class);
1238         }
1239
1240         Builder(final Class<? extends Shard> shardClass) {
1241             super(shardClass);
1242         }
1243     }
1244
1245     Ticker ticker() {
1246         return Ticker.systemTicker();
1247     }
1248
1249     void scheduleNextPendingTransaction() {
1250         self().tell(RESUME_NEXT_PENDING_TRANSACTION, ActorRef.noSender());
1251     }
1252 }