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