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