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