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

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