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

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.cluster.datastore;
   9
  10 import static com.google.common.base.Verify.verify;
  11
  12 import akka.actor.ActorRef;
  13 import akka.actor.ActorSelection;
  14 import akka.actor.Cancellable;
  15 import akka.actor.ExtendedActorSystem;
  16 import akka.actor.Props;
  17 import akka.actor.Status;
  18 import akka.actor.Status.Failure;
  19 import akka.serialization.JavaSerializer;
  20 import akka.serialization.Serialization;
  21 import com.google.common.annotations.VisibleForTesting;
  22 import com.google.common.base.Optional;
  23 import com.google.common.base.Preconditions;
  24 import com.google.common.base.Ticker;
  25 import com.google.common.base.Verify;
  26 import com.google.common.collect.ImmutableList;
  27 import com.google.common.collect.ImmutableMap;
  28 import com.google.common.collect.Range;
  29 import java.io.IOException;
  30 import java.util.Arrays;
  31 import java.util.Collection;
  32 import java.util.Collections;
  33 import java.util.Map;
  34 import java.util.concurrent.TimeUnit;
  35 import org.eclipse.jdt.annotation.NonNull;
  36 import org.eclipse.jdt.annotation.Nullable;
  37 import org.opendaylight.controller.cluster.access.ABIVersion;
  38 import org.opendaylight.controller.cluster.access.commands.ConnectClientRequest;
  39 import org.opendaylight.controller.cluster.access.commands.ConnectClientSuccess;
  40 import org.opendaylight.controller.cluster.access.commands.LocalHistoryRequest;
  41 import org.opendaylight.controller.cluster.access.commands.NotLeaderException;
  42 import org.opendaylight.controller.cluster.access.commands.OutOfSequenceEnvelopeException;
  43 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  44 import org.opendaylight.controller.cluster.access.concepts.ClientIdentifier;
  45 import org.opendaylight.controller.cluster.access.concepts.FrontendIdentifier;
  46 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  47 import org.opendaylight.controller.cluster.access.concepts.Request;
  48 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  49 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  50 import org.opendaylight.controller.cluster.access.concepts.RequestSuccess;
  51 import org.opendaylight.controller.cluster.access.concepts.RetiredGenerationException;
  52 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  53 import org.opendaylight.controller.cluster.access.concepts.SliceableMessage;
  54 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  55 import org.opendaylight.controller.cluster.access.concepts.UnsupportedRequestException;
  56 import org.opendaylight.controller.cluster.common.actor.CommonConfig;
  57 import org.opendaylight.controller.cluster.common.actor.Dispatchers;
  58 import org.opendaylight.controller.cluster.common.actor.Dispatchers.DispatcherType;
  59 import org.opendaylight.controller.cluster.common.actor.MessageTracker;
  60 import org.opendaylight.controller.cluster.common.actor.MessageTracker.Error;
  61 import org.opendaylight.controller.cluster.common.actor.MeteringBehavior;
  62 import org.opendaylight.controller.cluster.datastore.exceptions.NoShardLeaderException;
  63 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  64 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardDataTreeListenerInfoMXBeanImpl;
  65 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardMBeanFactory;
  66 import org.opendaylight.controller.cluster.datastore.jmx.mbeans.shard.ShardStats;
  67 import org.opendaylight.controller.cluster.datastore.messages.AbortTransaction;
  68 import org.opendaylight.controller.cluster.datastore.messages.ActorInitialized;
  69 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  70 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  71 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  72 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  73 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  74 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  75 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  76 import org.opendaylight.controller.cluster.datastore.messages.GetShardDataTree;
  77 import org.opendaylight.controller.cluster.datastore.messages.MakeLeaderLocal;
  78 import org.opendaylight.controller.cluster.datastore.messages.OnDemandShardState;
  79 import org.opendaylight.controller.cluster.datastore.messages.PeerAddressResolved;
  80 import org.opendaylight.controller.cluster.datastore.messages.PersistAbortTransactionPayload;
  81 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  82 import org.opendaylight.controller.cluster.datastore.messages.RegisterDataTreeChangeListener;
  83 import org.opendaylight.controller.cluster.datastore.messages.ShardLeaderStateChanged;
  84 import org.opendaylight.controller.cluster.datastore.messages.UpdateSchemaContext;
  85 import org.opendaylight.controller.cluster.datastore.persisted.AbortTransactionPayload;
  86 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot;
  87 import org.opendaylight.controller.cluster.datastore.persisted.DatastoreSnapshot.ShardSnapshot;
  88 import org.opendaylight.controller.cluster.datastore.persisted.DisableTrackingPayload;
  89 import org.opendaylight.controller.cluster.datastore.persisted.PurgeTransactionPayload;
  90 import org.opendaylight.controller.cluster.messaging.MessageAssembler;
  91 import org.opendaylight.controller.cluster.messaging.MessageSlicer;
  92 import org.opendaylight.controller.cluster.messaging.SliceOptions;
  93 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  94 import org.opendaylight.controller.cluster.notifications.RegisterRoleChangeListener;
  95 import org.opendaylight.controller.cluster.notifications.RoleChangeNotifier;
  96 import org.opendaylight.controller.cluster.raft.LeadershipTransferFailedException;
  97 import org.opendaylight.controller.cluster.raft.RaftActor;
  98 import org.opendaylight.controller.cluster.raft.RaftActorRecoveryCohort;
  99 import org.opendaylight.controller.cluster.raft.RaftActorSnapshotCohort;
 100 import org.opendaylight.controller.cluster.raft.RaftState;
 101 import org.opendaylight.controller.cluster.raft.base.messages.FollowerInitialSyncUpStatus;
 102 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
 103 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
 104 import org.opendaylight.controller.cluster.raft.messages.RequestLeadership;
 105 import org.opendaylight.controller.cluster.raft.messages.ServerRemoved;
 106 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
 107 import org.opendaylight.yangtools.concepts.Identifier;
 108 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
 109 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
 110 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
 111 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
 112 import org.opendaylight.yangtools.yang.model.api.SchemaContextProvider;
 113 import scala.concurrent.duration.FiniteDuration;
 114
 115 /**
 116  * A Shard represents a portion of the logical data tree.
 117  *
 118  * <p>
 119  * Our Shard uses InMemoryDataTree as it's internal representation and delegates all requests it
 120  */
 121 public class Shard extends RaftActor {
 122
 123     @VisibleForTesting
 124     static final Object TX_COMMIT_TIMEOUT_CHECK_MESSAGE = new Object() {
 125         @Override
 126         public String toString() {
 127             return "txCommitTimeoutCheck";
 128         }
 129     };
 130
 131     @VisibleForTesting
 132     static final Object GET_SHARD_MBEAN_MESSAGE = new Object() {
 133         @Override
 134         public String toString() {
 135             return "getShardMBeanMessage";
 136         }
 137     };
 138
 139     static final Object RESUME_NEXT_PENDING_TRANSACTION = new Object() {
 140         @Override
 141         public String toString() {
 142             return "resumeNextPendingTransaction";
 143         }
 144     };
 145
 146     // FIXME: shard names should be encapsulated in their own class and this should be exposed as a constant.
 147     public static final String DEFAULT_NAME = "default";
 148
 149     private static final Collection<ABIVersion> SUPPORTED_ABIVERSIONS;
 150
 151     static {
 152         final ABIVersion[] values = ABIVersion.values();
 153         final ABIVersion[] real = Arrays.copyOfRange(values, 1, values.length - 1);
 154         SUPPORTED_ABIVERSIONS = ImmutableList.copyOf(real).reverse();
 155     }
 156
 157     // FIXME: make this a dynamic property based on mailbox size and maximum number of clients
 158     private static final int CLIENT_MAX_MESSAGES = 1000;
 159
 160     // The state of this Shard
 161     private final ShardDataTree store;
 162
 163     /// The name of this shard
 164     private final String name;
 165
 166     private final String shardName;
 167
 168     private final ShardStats shardMBean;
 169
 170     private final ShardDataTreeListenerInfoMXBeanImpl listenerInfoMXBean;
 171
 172     private DatastoreContext datastoreContext;
 173
 174     private final ShardCommitCoordinator commitCoordinator;
 175
 176     private long transactionCommitTimeout;
 177
 178     private Cancellable txCommitTimeoutCheckSchedule;
 179
 180     private final Optional<ActorRef> roleChangeNotifier;
 181
 182     private final MessageTracker appendEntriesReplyTracker;
 183
 184     private final ShardTransactionActorFactory transactionActorFactory;
 185
 186     private final ShardSnapshotCohort snapshotCohort;
 187
 188     private final DataTreeChangeListenerSupport treeChangeSupport = new DataTreeChangeListenerSupport(this);
 189
 190     private ShardSnapshot restoreFromSnapshot;
 191
 192     private final ShardTransactionMessageRetrySupport messageRetrySupport;
 193
 194     private final FrontendMetadata frontendMetadata;
 195     private Map<FrontendIdentifier, LeaderFrontendState> knownFrontends = ImmutableMap.of();
 196     private boolean paused;
 197
 198     private final MessageSlicer responseMessageSlicer;
 199     private final Dispatchers dispatchers;
 200
 201     private final MessageAssembler requestMessageAssembler;
 202
 203     protected Shard(final AbstractBuilder<?, ?> builder) {
 204         super(builder.getId().toString(), builder.getPeerAddresses(),
 205                 Optional.of(builder.getDatastoreContext().getShardRaftConfig()), DataStoreVersions.CURRENT_VERSION);
 206
 207         this.name = builder.getId().toString();
 208         this.shardName = builder.getId().getShardName();
 209         this.datastoreContext = builder.getDatastoreContext();
 210         this.restoreFromSnapshot = builder.getRestoreFromSnapshot();
 211         this.frontendMetadata = new FrontendMetadata(name);
 212
 213         setPersistence(datastoreContext.isPersistent());
 214
 215         LOG.info("Shard created : {}, persistent : {}", name, datastoreContext.isPersistent());
 216
 217         ShardDataTreeChangeListenerPublisherActorProxy treeChangeListenerPublisher =
 218                 new ShardDataTreeChangeListenerPublisherActorProxy(getContext(), name + "-DTCL-publisher", name);
 219         if (builder.getDataTree() != null) {
 220             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getDataTree(),
 221                     treeChangeListenerPublisher, name, frontendMetadata);
 222         } else {
 223             store = new ShardDataTree(this, builder.getSchemaContext(), builder.getTreeType(),
 224                     builder.getDatastoreContext().getStoreRoot(), treeChangeListenerPublisher, name, frontendMetadata);
 225         }
 226
 227         shardMBean = ShardMBeanFactory.getShardStatsMBean(name, datastoreContext.getDataStoreMXBeanType(), this);
 228
 229         if (isMetricsCaptureEnabled()) {
 230             getContext().become(new MeteringBehavior(this));
 231         }
 232
 233         commitCoordinator = new ShardCommitCoordinator(store, LOG, this.name);
 234
 235         setTransactionCommitTimeout();
 236
 237         // create a notifier actor for each cluster member
 238         roleChangeNotifier = createRoleChangeNotifier(name);
 239
 240         appendEntriesReplyTracker = new MessageTracker(AppendEntriesReply.class,
 241                 getRaftActorContext().getConfigParams().getIsolatedCheckIntervalInMillis());
 242
 243         dispatchers = new Dispatchers(context().system().dispatchers());
 244         transactionActorFactory = new ShardTransactionActorFactory(store, datastoreContext,
 245             dispatchers.getDispatcherPath(Dispatchers.DispatcherType.Transaction),
 246                 self(), getContext(), shardMBean, builder.getId().getShardName());
 247
 248         snapshotCohort = ShardSnapshotCohort.create(getContext(), builder.getId().getMemberName(), store, LOG,
 249             this.name);
 250
 251         messageRetrySupport = new ShardTransactionMessageRetrySupport(this);
 252
 253         responseMessageSlicer = MessageSlicer.builder().logContext(this.name)
 254                 .messageSliceSize(datastoreContext.getMaximumMessageSliceSize())
 255                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 256                 .expireStateAfterInactivity(2, TimeUnit.MINUTES).build();
 257
 258         requestMessageAssembler = MessageAssembler.builder().logContext(this.name)
 259                 .fileBackedStreamFactory(getRaftActorContext().getFileBackedOutputStreamFactory())
 260                 .assembledMessageCallback((message, sender) -> self().tell(message, sender))
 261                 .expireStateAfterInactivity(datastoreContext.getRequestTimeout(), TimeUnit.NANOSECONDS).build();
 262
 263         listenerInfoMXBean = new ShardDataTreeListenerInfoMXBeanImpl(name, datastoreContext.getDataStoreMXBeanType(),
 264                 self());
 265         listenerInfoMXBean.register();
 266     }
 267
 268     private void setTransactionCommitTimeout() {
 269         transactionCommitTimeout = TimeUnit.MILLISECONDS.convert(
 270                 datastoreContext.getShardTransactionCommitTimeoutInSeconds(), TimeUnit.SECONDS) / 2;
 271     }
 272
 273     private Optional<ActorRef> createRoleChangeNotifier(final String shardId) {
 274         ActorRef shardRoleChangeNotifier = this.getContext().actorOf(
 275             RoleChangeNotifier.getProps(shardId), shardId + "-notifier");
 276         return Optional.of(shardRoleChangeNotifier);
 277     }
 278
 279     @Override
 280     public void postStop() {
 281         LOG.info("Stopping Shard {}", persistenceId());
 282
 283         super.postStop();
 284
 285         messageRetrySupport.close();
 286
 287         if (txCommitTimeoutCheckSchedule != null) {
 288             txCommitTimeoutCheckSchedule.cancel();
 289         }
 290
 291         commitCoordinator.abortPendingTransactions("Transaction aborted due to shutdown.", this);
 292
 293         shardMBean.unregisterMBean();
 294         listenerInfoMXBean.unregister();
 295     }
 296
 297     @Override
 298     protected void handleRecover(final Object message) {
 299         LOG.debug("{}: onReceiveRecover: Received message {} from {}", persistenceId(), message.getClass(),
 300             getSender());
 301
 302         super.handleRecover(message);
 303         if (LOG.isTraceEnabled()) {
 304             appendEntriesReplyTracker.begin();
 305         }
 306     }
 307
 308     @Override
 309     protected void handleNonRaftCommand(final Object message) {
 310         try (MessageTracker.Context context = appendEntriesReplyTracker.received(message)) {
 311             final Optional<Error> maybeError = context.error();
 312             if (maybeError.isPresent()) {
 313                 LOG.trace("{} : AppendEntriesReply failed to arrive at the expected interval {}", persistenceId(),
 314                     maybeError.get());
 315             }
 316
 317             store.resetTransactionBatch();
 318
 319             if (message instanceof RequestEnvelope) {
 320                 handleRequestEnvelope((RequestEnvelope)message);
 321             } else if (MessageAssembler.isHandledMessage(message)) {
 322                 handleRequestAssemblerMessage(message);
 323             } else if (message instanceof ConnectClientRequest) {
 324                 handleConnectClient((ConnectClientRequest)message);
 325             } else if (CreateTransaction.isSerializedType(message)) {
 326                 handleCreateTransaction(message);
 327             } else if (message instanceof BatchedModifications) {
 328                 handleBatchedModifications((BatchedModifications)message);
 329             } else if (message instanceof ForwardedReadyTransaction) {
 330                 handleForwardedReadyTransaction((ForwardedReadyTransaction) message);
 331             } else if (message instanceof ReadyLocalTransaction) {
 332                 handleReadyLocalTransaction((ReadyLocalTransaction)message);
 333             } else if (CanCommitTransaction.isSerializedType(message)) {
 334                 handleCanCommitTransaction(CanCommitTransaction.fromSerializable(message));
 335             } else if (CommitTransaction.isSerializedType(message)) {
 336                 handleCommitTransaction(CommitTransaction.fromSerializable(message));
 337             } else if (AbortTransaction.isSerializedType(message)) {
 338                 handleAbortTransaction(AbortTransaction.fromSerializable(message));
 339             } else if (CloseTransactionChain.isSerializedType(message)) {
 340                 closeTransactionChain(CloseTransactionChain.fromSerializable(message));
 341             } else if (message instanceof RegisterDataTreeChangeListener) {
 342                 treeChangeSupport.onMessage((RegisterDataTreeChangeListener) message, isLeader(), hasLeader());
 343             } else if (message instanceof UpdateSchemaContext) {
 344                 updateSchemaContext((UpdateSchemaContext) message);
 345             } else if (message instanceof PeerAddressResolved) {
 346                 PeerAddressResolved resolved = (PeerAddressResolved) message;
 347                 setPeerAddress(resolved.getPeerId(), resolved.getPeerAddress());
 348             } else if (TX_COMMIT_TIMEOUT_CHECK_MESSAGE.equals(message)) {
 349                 commitTimeoutCheck();
 350             } else if (message instanceof DatastoreContext) {
 351                 onDatastoreContext((DatastoreContext)message);
 352             } else if (message instanceof RegisterRoleChangeListener) {
 353                 roleChangeNotifier.get().forward(message, context());
 354             } else if (message instanceof FollowerInitialSyncUpStatus) {
 355                 shardMBean.setFollowerInitialSyncStatus(((FollowerInitialSyncUpStatus) message).isInitialSyncDone());
 356                 context().parent().tell(message, self());
 357             } else if (GET_SHARD_MBEAN_MESSAGE.equals(message)) {
 358                 sender().tell(getShardMBean(), self());
 359             } else if (message instanceof GetShardDataTree) {
 360                 sender().tell(store.getDataTree(), self());
 361             } else if (message instanceof ServerRemoved) {
 362                 context().parent().forward(message, context());
 363             } else if (ShardTransactionMessageRetrySupport.TIMER_MESSAGE_CLASS.isInstance(message)) {
 364                 messageRetrySupport.onTimerMessage(message);
 365             } else if (message instanceof DataTreeCohortActorRegistry.CohortRegistryCommand) {
 366                 store.processCohortRegistryCommand(getSender(),
 367                         (DataTreeCohortActorRegistry.CohortRegistryCommand) message);
 368             } else if (message instanceof PersistAbortTransactionPayload) {
 369                 final TransactionIdentifier txId = ((PersistAbortTransactionPayload) message).getTransactionId();
 370                 persistPayload(txId, AbortTransactionPayload.create(txId,
 371                     datastoreContext.getInitialPayloadSerializedBufferCapacity()), true);
 372                 persistPayload(txId, PurgeTransactionPayload.create(txId,
 373                     datastoreContext.getInitialPayloadSerializedBufferCapacity()), false);
 374             } else if (message instanceof MakeLeaderLocal) {
 375                 onMakeLeaderLocal();
 376             } else if (RESUME_NEXT_PENDING_TRANSACTION.equals(message)) {
 377                 store.resumeNextPendingTransaction();
 378             } else if (!responseMessageSlicer.handleMessage(message)) {
 379                 super.handleNonRaftCommand(message);
 380             }
 381         }
 382     }
 383
 384     private void handleRequestAssemblerMessage(final Object message) {
 385         dispatchers.getDispatcher(DispatcherType.Serialization).execute(() -> {
 386             JavaSerializer.currentSystem().value_$eq((ExtendedActorSystem) context().system());
 387             requestMessageAssembler.handleMessage(message, self());
 388         });
 389     }
 390
 391     @SuppressWarnings("checkstyle:IllegalCatch")
 392     private void handleRequestEnvelope(final RequestEnvelope envelope) {
 393         final long now = ticker().read();
 394         try {
 395             final RequestSuccess<?, ?> success = handleRequest(envelope, now);
 396             if (success != null) {
 397                 final long executionTimeNanos = ticker().read() - now;
 398                 if (success instanceof SliceableMessage) {
 399                     dispatchers.getDispatcher(DispatcherType.Serialization).execute(() ->
 400                         responseMessageSlicer.slice(SliceOptions.builder().identifier(success.getTarget())
 401                             .message(envelope.newSuccessEnvelope(success, executionTimeNanos))
 402                             .sendTo(envelope.getMessage().getReplyTo()).replyTo(self())
 403                             .onFailureCallback(t -> LOG.warn("Error slicing response {}", success, t)).build()));
 404                 } else {
 405                     envelope.sendSuccess(success, executionTimeNanos);
 406                 }
 407             }
 408         } catch (RequestException e) {
 409             LOG.debug("{}: request {} failed", persistenceId(), envelope, e);
 410             envelope.sendFailure(e, ticker().read() - now);
 411         } catch (Exception e) {
 412             LOG.debug("{}: request {} caused failure", persistenceId(), envelope, e);
 413             envelope.sendFailure(new RuntimeRequestException("Request failed to process", e),
 414                 ticker().read() - now);
 415         }
 416     }
 417
 418     private void commitTimeoutCheck() {
 419         store.checkForExpiredTransactions(transactionCommitTimeout, this::updateAccess);
 420         commitCoordinator.checkForExpiredTransactions(transactionCommitTimeout, this);
 421         requestMessageAssembler.checkExpiredAssembledMessageState();
 422     }
 423
 424     private Optional<Long> updateAccess(final SimpleShardDataTreeCohort cohort) {
 425         final FrontendIdentifier frontend = cohort.getIdentifier().getHistoryId().getClientId().getFrontendId();
 426         final LeaderFrontendState state = knownFrontends.get(frontend);
 427         if (state == null) {
 428             // Not tell-based protocol, do nothing
 429             return Optional.absent();
 430         }
 431
 432         if (isIsolatedLeader()) {
 433             // We are isolated and no new request can come through until we emerge from it. We are still updating
 434             // liveness of frontend when we see it attempting to communicate. Use the last access timer.
 435             return Optional.of(state.getLastSeenTicks());
 436         }
 437
 438         // If this frontend has freshly connected, give it some time to catch up before killing its transactions.
 439         return Optional.of(state.getLastConnectTicks());
 440     }
 441
 442     private void disableTracking(final DisableTrackingPayload payload) {
 443         final ClientIdentifier clientId = payload.getIdentifier();
 444         LOG.debug("{}: disabling tracking of {}", persistenceId(), clientId);
 445         frontendMetadata.disableTracking(clientId);
 446
 447         if (isLeader()) {
 448             final FrontendIdentifier frontendId = clientId.getFrontendId();
 449             final LeaderFrontendState frontend = knownFrontends.get(frontendId);
 450             if (frontend != null) {
 451                 if (clientId.equals(frontend.getIdentifier())) {
 452                     if (!(frontend instanceof LeaderFrontendState.Disabled)) {
 453                         verify(knownFrontends.replace(frontendId, frontend,
 454                             new LeaderFrontendState.Disabled(persistenceId(), clientId, store)));
 455                         LOG.debug("{}: leader state for {} disabled", persistenceId(), clientId);
 456                     } else {
 457                         LOG.debug("{}: leader state {} is already disabled", persistenceId(), frontend);
 458                     }
 459                 } else {
 460                     LOG.debug("{}: leader state {} does not match {}", persistenceId(), frontend, clientId);
 461                 }
 462             } else {
 463                 LOG.debug("{}: leader state for {} not found", persistenceId(), clientId);
 464             }
 465         }
 466     }
 467
 468     private void onMakeLeaderLocal() {
 469         LOG.debug("{}: onMakeLeaderLocal received", persistenceId());
 470         if (isLeader()) {
 471             getSender().tell(new Status.Success(null), getSelf());
 472             return;
 473         }
 474
 475         final ActorSelection leader = getLeader();
 476
 477         if (leader == null) {
 478             // Leader is not present. The cluster is most likely trying to
 479             // elect a leader and we should let that run its normal course
 480
 481             // TODO we can wait for the election to complete and retry the
 482             // request. We can also let the caller retry by sending a flag
 483             // in the response indicating the request is "reTryable".
 484             getSender().tell(new Failure(
 485                     new LeadershipTransferFailedException("We cannot initiate leadership transfer to local node. "
 486                             + "Currently there is no leader for " + persistenceId())),
 487                     getSelf());
 488             return;
 489         }
 490
 491         leader.tell(new RequestLeadership(getId(), getSender()), getSelf());
 492     }
 493
 494     // Acquire our frontend tracking handle and verify generation matches
 495     private @Nullable LeaderFrontendState findFrontend(final ClientIdentifier clientId) throws RequestException {
 496         final LeaderFrontendState existing = knownFrontends.get(clientId.getFrontendId());
 497         if (existing != null) {
 498             final int cmp = Long.compareUnsigned(existing.getIdentifier().getGeneration(), clientId.getGeneration());
 499             if (cmp == 0) {
 500                 existing.touch();
 501                 return existing;
 502             }
 503             if (cmp > 0) {
 504                 LOG.debug("{}: rejecting request from outdated client {}", persistenceId(), clientId);
 505                 throw new RetiredGenerationException(clientId.getGeneration(),
 506                     existing.getIdentifier().getGeneration());
 507             }
 508
 509             LOG.info("{}: retiring state {}, outdated by request from client {}", persistenceId(), existing, clientId);
 510             existing.retire();
 511             knownFrontends.remove(clientId.getFrontendId());
 512         } else {
 513             LOG.debug("{}: client {} is not yet known", persistenceId(), clientId);
 514         }
 515
 516         return null;
 517     }
 518
 519     private LeaderFrontendState getFrontend(final ClientIdentifier clientId) throws RequestException {
 520         final LeaderFrontendState ret = findFrontend(clientId);
 521         if (ret != null) {
 522             return ret;
 523         }
 524
 525         // TODO: a dedicated exception would be better, but this is technically true, too
 526         throw new OutOfSequenceEnvelopeException(0);
 527     }
 528
 529     private static @NonNull ABIVersion selectVersion(final ConnectClientRequest message) {
 530         final Range<ABIVersion> clientRange = Range.closed(message.getMinVersion(), message.getMaxVersion());
 531         for (ABIVersion v : SUPPORTED_ABIVERSIONS) {
 532             if (clientRange.contains(v)) {
 533                 return v;
 534             }
 535         }
 536
 537         throw new IllegalArgumentException(String.format(
 538             "No common version between backend versions %s and client versions %s", SUPPORTED_ABIVERSIONS,
 539             clientRange));
 540     }
 541
 542     @SuppressWarnings("checkstyle:IllegalCatch")
 543     private void handleConnectClient(final ConnectClientRequest message) {
 544         try {
 545             final ClientIdentifier clientId = message.getTarget();
 546             final LeaderFrontendState existing = findFrontend(clientId);
 547             if (existing != null) {
 548                 existing.touch();
 549             }
 550
 551             if (!isLeader() || !isLeaderActive()) {
 552                 LOG.info("{}: not currently leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 553                                 + "isLeadershipTransferInProgress: {}.",
 554                         persistenceId(), message, isLeader(), isLeaderActive(), isLeadershipTransferInProgress());
 555                 throw new NotLeaderException(getSelf());
 556             }
 557
 558             final ABIVersion selectedVersion = selectVersion(message);
 559             final LeaderFrontendState frontend;
 560             if (existing == null) {
 561                 frontend = new LeaderFrontendState.Enabled(persistenceId(), clientId, store);
 562                 knownFrontends.put(clientId.getFrontendId(), frontend);
 563                 LOG.debug("{}: created state {} for client {}", persistenceId(), frontend, clientId);
 564             } else {
 565                 frontend = existing;
 566             }
 567
 568             frontend.reconnect();
 569             message.getReplyTo().tell(new ConnectClientSuccess(message.getTarget(), message.getSequence(), getSelf(),
 570                 ImmutableList.of(), store.getDataTree(), CLIENT_MAX_MESSAGES).toVersion(selectedVersion),
 571                 ActorRef.noSender());
 572         } catch (RequestException | RuntimeException e) {
 573             message.getReplyTo().tell(new Failure(e), ActorRef.noSender());
 574         }
 575     }
 576
 577     private @Nullable RequestSuccess<?, ?> handleRequest(final RequestEnvelope envelope, final long now)
 578             throws RequestException {
 579         // We are not the leader, hence we want to fail-fast.
 580         if (!isLeader() || paused || !isLeaderActive()) {
 581             LOG.debug("{}: not currently active leader, rejecting request {}. isLeader: {}, isLeaderActive: {},"
 582                             + "isLeadershipTransferInProgress: {}, paused: {}",
 583                     persistenceId(), envelope, isLeader(), isLeaderActive(), isLeadershipTransferInProgress(), paused);
 584             throw new NotLeaderException(getSelf());
 585         }
 586
 587         final Request<?, ?> request = envelope.getMessage();
 588         if (request instanceof TransactionRequest) {
 589             final TransactionRequest<?> txReq = (TransactionRequest<?>)request;
 590             final ClientIdentifier clientId = txReq.getTarget().getHistoryId().getClientId();
 591             return getFrontend(clientId).handleTransactionRequest(txReq, envelope, now);
 592         } else if (request instanceof LocalHistoryRequest) {
 593             final LocalHistoryRequest<?> lhReq = (LocalHistoryRequest<?>)request;
 594             final ClientIdentifier clientId = lhReq.getTarget().getClientId();
 595             return getFrontend(clientId).handleLocalHistoryRequest(lhReq, envelope, now);
 596         } else {
 597             LOG.warn("{}: rejecting unsupported request {}", persistenceId(), request);
 598             throw new UnsupportedRequestException(request);
 599         }
 600     }
 601
 602     private boolean hasLeader() {
 603         return getLeaderId() != null;
 604     }
 605
 606     public int getPendingTxCommitQueueSize() {
 607         return store.getQueueSize();
 608     }
 609
 610     public int getCohortCacheSize() {
 611         return commitCoordinator.getCohortCacheSize();
 612     }
 613
 614     @Override
 615     protected Optional<ActorRef> getRoleChangeNotifier() {
 616         return roleChangeNotifier;
 617     }
 618
 619     String getShardName() {
 620         return shardName;
 621     }
 622
 623     @Override
 624     protected LeaderStateChanged newLeaderStateChanged(final String memberId, final String leaderId,
 625             final short leaderPayloadVersion) {
 626         return isLeader() ? new ShardLeaderStateChanged(memberId, leaderId, store.getDataTree(), leaderPayloadVersion)
 627                 : new ShardLeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 628     }
 629
 630     protected void onDatastoreContext(final DatastoreContext context) {
 631         datastoreContext = context;
 632
 633         setTransactionCommitTimeout();
 634
 635         setPersistence(datastoreContext.isPersistent());
 636
 637         updateConfigParams(datastoreContext.getShardRaftConfig());
 638     }
 639
 640     // applyState() will be invoked once consensus is reached on the payload
 641     void persistPayload(final Identifier id, final Payload payload, final boolean batchHint) {
 642         boolean canSkipPayload = !hasFollowers() && !persistence().isRecoveryApplicable();
 643         if (canSkipPayload) {
 644             applyState(self(), id, payload);
 645         } else {
 646             // We are faking the sender
 647             persistData(self(), id, payload, batchHint);
 648         }
 649     }
 650
 651     private void handleCommitTransaction(final CommitTransaction commit) {
 652         final TransactionIdentifier txId = commit.getTransactionId();
 653         if (isLeader()) {
 654             askProtocolEncountered(txId);
 655             commitCoordinator.handleCommit(txId, getSender(), this);
 656         } else {
 657             ActorSelection leader = getLeader();
 658             if (leader == null) {
 659                 messageRetrySupport.addMessageToRetry(commit, getSender(), "Could not commit transaction " + txId);
 660             } else {
 661                 LOG.debug("{}: Forwarding CommitTransaction to leader {}", persistenceId(), leader);
 662                 leader.forward(commit, getContext());
 663             }
 664         }
 665     }
 666
 667     private void handleCanCommitTransaction(final CanCommitTransaction canCommit) {
 668         final TransactionIdentifier txId = canCommit.getTransactionId();
 669         LOG.debug("{}: Can committing transaction {}", persistenceId(), txId);
 670
 671         if (isLeader()) {
 672             askProtocolEncountered(txId);
 673             commitCoordinator.handleCanCommit(txId, getSender(), this);
 674         } else {
 675             ActorSelection leader = getLeader();
 676             if (leader == null) {
 677                 messageRetrySupport.addMessageToRetry(canCommit, getSender(),
 678                         "Could not canCommit transaction " + txId);
 679             } else {
 680                 LOG.debug("{}: Forwarding CanCommitTransaction to leader {}", persistenceId(), leader);
 681                 leader.forward(canCommit, getContext());
 682             }
 683         }
 684     }
 685
 686     @SuppressWarnings("checkstyle:IllegalCatch")
 687     protected void handleBatchedModificationsLocal(final BatchedModifications batched, final ActorRef sender) {
 688         askProtocolEncountered(batched.getTransactionId());
 689
 690         try {
 691             commitCoordinator.handleBatchedModifications(batched, sender, this);
 692         } catch (Exception e) {
 693             LOG.error("{}: Error handling BatchedModifications for Tx {}", persistenceId(),
 694                     batched.getTransactionId(), e);
 695             sender.tell(new Failure(e), getSelf());
 696         }
 697     }
 698
 699     private void handleBatchedModifications(final BatchedModifications batched) {
 700         // This message is sent to prepare the modifications transaction directly on the Shard as an
 701         // optimization to avoid the extra overhead of a separate ShardTransaction actor. On the last
 702         // BatchedModifications message, the caller sets the ready flag in the message indicating
 703         // modifications are complete. The reply contains the cohort actor path (this actor) for the caller
 704         // to initiate the 3-phase commit. This also avoids the overhead of sending an additional
 705         // ReadyTransaction message.
 706
 707         // If we're not the leader then forward to the leader. This is a safety measure - we shouldn't
 708         // normally get here if we're not the leader as the front-end (TransactionProxy) should determine
 709         // the primary/leader shard. However with timing and caching on the front-end, there's a small
 710         // window where it could have a stale leader during leadership transitions.
 711         //
 712         boolean isLeaderActive = isLeaderActive();
 713         if (isLeader() && isLeaderActive) {
 714             handleBatchedModificationsLocal(batched, getSender());
 715         } else {
 716             ActorSelection leader = getLeader();
 717             if (!isLeaderActive || leader == null) {
 718                 messageRetrySupport.addMessageToRetry(batched, getSender(),
 719                         "Could not process BatchedModifications " + batched.getTransactionId());
 720             } else {
 721                 // If this is not the first batch and leadership changed in between batched messages,
 722                 // we need to reconstruct previous BatchedModifications from the transaction
 723                 // DataTreeModification, honoring the max batched modification count, and forward all the
 724                 // previous BatchedModifications to the new leader.
 725                 Collection<BatchedModifications> newModifications = commitCoordinator
 726                         .createForwardedBatchedModifications(batched,
 727                                 datastoreContext.getShardBatchedModificationCount());
 728
 729                 LOG.debug("{}: Forwarding {} BatchedModifications to leader {}", persistenceId(),
 730                         newModifications.size(), leader);
 731
 732                 for (BatchedModifications bm : newModifications) {
 733                     leader.forward(bm, getContext());
 734                 }
 735             }
 736         }
 737     }
 738
 739     private boolean failIfIsolatedLeader(final ActorRef sender) {
 740         if (isIsolatedLeader()) {
 741             sender.tell(new Failure(new NoShardLeaderException(String.format(
 742                     "Shard %s was the leader but has lost contact with all of its followers. Either all"
 743                     + " other follower nodes are down or this node is isolated by a network partition.",
 744                     persistenceId()))), getSelf());
 745             return true;
 746         }
 747
 748         return false;
 749     }
 750
 751     protected boolean isIsolatedLeader() {
 752         return getRaftState() == RaftState.IsolatedLeader;
 753     }
 754
 755     @SuppressWarnings("checkstyle:IllegalCatch")
 756     private void handleReadyLocalTransaction(final ReadyLocalTransaction message) {
 757         LOG.debug("{}: handleReadyLocalTransaction for {}", persistenceId(), message.getTransactionId());
 758
 759         boolean isLeaderActive = isLeaderActive();
 760         if (isLeader() && isLeaderActive) {
 761             try {
 762                 commitCoordinator.handleReadyLocalTransaction(message, getSender(), this);
 763             } catch (Exception e) {
 764                 LOG.error("{}: Error handling ReadyLocalTransaction for Tx {}", persistenceId(),
 765                         message.getTransactionId(), e);
 766                 getSender().tell(new Failure(e), getSelf());
 767             }
 768         } else {
 769             ActorSelection leader = getLeader();
 770             if (!isLeaderActive || leader == null) {
 771                 messageRetrySupport.addMessageToRetry(message, getSender(),
 772                         "Could not process ready local transaction " + message.getTransactionId());
 773             } else {
 774                 LOG.debug("{}: Forwarding ReadyLocalTransaction to leader {}", persistenceId(), leader);
 775                 message.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 776                 leader.forward(message, getContext());
 777             }
 778         }
 779     }
 780
 781     private void handleForwardedReadyTransaction(final ForwardedReadyTransaction forwardedReady) {
 782         LOG.debug("{}: handleForwardedReadyTransaction for {}", persistenceId(), forwardedReady.getTransactionId());
 783
 784         boolean isLeaderActive = isLeaderActive();
 785         if (isLeader() && isLeaderActive) {
 786             askProtocolEncountered(forwardedReady.getTransactionId());
 787             commitCoordinator.handleForwardedReadyTransaction(forwardedReady, getSender(), this);
 788         } else {
 789             ActorSelection leader = getLeader();
 790             if (!isLeaderActive || leader == null) {
 791                 messageRetrySupport.addMessageToRetry(forwardedReady, getSender(),
 792                         "Could not process forwarded ready transaction " + forwardedReady.getTransactionId());
 793             } else {
 794                 LOG.debug("{}: Forwarding ForwardedReadyTransaction to leader {}", persistenceId(), leader);
 795
 796                 ReadyLocalTransaction readyLocal = new ReadyLocalTransaction(forwardedReady.getTransactionId(),
 797                         forwardedReady.getTransaction().getSnapshot(), forwardedReady.isDoImmediateCommit(),
 798                         forwardedReady.getParticipatingShardNames());
 799                 readyLocal.setRemoteVersion(getCurrentBehavior().getLeaderPayloadVersion());
 800                 leader.forward(readyLocal, getContext());
 801             }
 802         }
 803     }
 804
 805     private void handleAbortTransaction(final AbortTransaction abort) {
 806         final TransactionIdentifier transactionId = abort.getTransactionId();
 807         askProtocolEncountered(transactionId);
 808         doAbortTransaction(transactionId, getSender());
 809     }
 810
 811     void doAbortTransaction(final Identifier transactionID, final ActorRef sender) {
 812         commitCoordinator.handleAbort(transactionID, sender, this);
 813     }
 814
 815     private void handleCreateTransaction(final Object message) {
 816         if (isLeader()) {
 817             createTransaction(CreateTransaction.fromSerializable(message));
 818         } else if (getLeader() != null) {
 819             getLeader().forward(message, getContext());
 820         } else {
 821             getSender().tell(new Failure(new NoShardLeaderException(
 822                     "Could not create a shard transaction", persistenceId())), getSelf());
 823         }
 824     }
 825
 826     private void closeTransactionChain(final CloseTransactionChain closeTransactionChain) {
 827         if (isLeader()) {
 828             final LocalHistoryIdentifier id = closeTransactionChain.getIdentifier();
 829             askProtocolEncountered(id.getClientId());
 830
 831             // FIXME: CONTROLLER-1628: stage purge once no transactions are present
 832             store.closeTransactionChain(id, null);
 833             store.purgeTransactionChain(id, null);
 834         } else if (getLeader() != null) {
 835             getLeader().forward(closeTransactionChain, getContext());
 836         } else {
 837             LOG.warn("{}: Could not close transaction {}", persistenceId(), closeTransactionChain.getIdentifier());
 838         }
 839     }
 840
 841     @SuppressWarnings("checkstyle:IllegalCatch")
 842     private void createTransaction(final CreateTransaction createTransaction) {
 843         askProtocolEncountered(createTransaction.getTransactionId());
 844
 845         try {
 846             if (TransactionType.fromInt(createTransaction.getTransactionType()) != TransactionType.READ_ONLY
 847                     && failIfIsolatedLeader(getSender())) {
 848                 return;
 849             }
 850
 851             ActorRef transactionActor = createTransaction(createTransaction.getTransactionType(),
 852                 createTransaction.getTransactionId());
 853
 854             getSender().tell(new CreateTransactionReply(Serialization.serializedActorPath(transactionActor),
 855                     createTransaction.getTransactionId(), createTransaction.getVersion()).toSerializable(), getSelf());
 856         } catch (Exception e) {
 857             getSender().tell(new Failure(e), getSelf());
 858         }
 859     }
 860
 861     private ActorRef createTransaction(final int transactionType, final TransactionIdentifier transactionId) {
 862         LOG.debug("{}: Creating transaction : {} ", persistenceId(), transactionId);
 863         return transactionActorFactory.newShardTransaction(TransactionType.fromInt(transactionType),
 864             transactionId);
 865     }
 866
 867     // Called on leader only
 868     private void askProtocolEncountered(final TransactionIdentifier transactionId) {
 869         askProtocolEncountered(transactionId.getHistoryId().getClientId());
 870     }
 871
 872     // Called on leader only
 873     private void askProtocolEncountered(final ClientIdentifier clientId) {
 874         final LeaderFrontendState state = knownFrontends.get(clientId.getFrontendId());
 875         if (state instanceof LeaderFrontendState.Enabled) {
 876             LOG.debug("{}: encountered ask-based client {}, disabling transaction tracking", persistenceId(), clientId);
 877             persistPayload(clientId, DisableTrackingPayload.create(clientId,
 878                 datastoreContext.getInitialPayloadSerializedBufferCapacity()), false);
 879         }
 880     }
 881
 882     private void updateSchemaContext(final UpdateSchemaContext message) {
 883         updateSchemaContext(message.getSchemaContext());
 884     }
 885
 886     @VisibleForTesting
 887     void updateSchemaContext(final SchemaContext schemaContext) {
 888         store.updateSchemaContext(schemaContext);
 889     }
 890
 891     private boolean isMetricsCaptureEnabled() {
 892         CommonConfig config = new CommonConfig(getContext().system().settings().config());
 893         return config.isMetricCaptureEnabled();
 894     }
 895
 896     @Override
 897     @VisibleForTesting
 898     public RaftActorSnapshotCohort getRaftActorSnapshotCohort() {
 899         return snapshotCohort;
 900     }
 901
 902     @Override
 903     protected RaftActorRecoveryCohort getRaftActorRecoveryCohort() {
 904         if (restoreFromSnapshot == null) {
 905             return ShardRecoveryCoordinator.create(store, persistenceId(), LOG);
 906         }
 907
 908         return ShardRecoveryCoordinator.forSnapshot(store, persistenceId(), LOG, restoreFromSnapshot.getSnapshot());
 909     }
 910
 911     @Override
 912     protected void onRecoveryComplete() {
 913         restoreFromSnapshot = null;
 914
 915         //notify shard manager
 916         getContext().parent().tell(new ActorInitialized(), getSelf());
 917
 918         // Being paranoid here - this method should only be called once but just in case...
 919         if (txCommitTimeoutCheckSchedule == null) {
 920             // Schedule a message to be periodically sent to check if the current in-progress
 921             // transaction should be expired and aborted.
 922             FiniteDuration period = FiniteDuration.create(transactionCommitTimeout / 3, TimeUnit.MILLISECONDS);
 923             txCommitTimeoutCheckSchedule = getContext().system().scheduler().schedule(
 924                     period, period, getSelf(),
 925                     TX_COMMIT_TIMEOUT_CHECK_MESSAGE, getContext().dispatcher(), ActorRef.noSender());
 926         }
 927     }
 928
 929     @Override
 930     protected void applyState(final ActorRef clientActor, final Identifier identifier, final Object data) {
 931         if (data instanceof Payload) {
 932             if (data instanceof DisableTrackingPayload) {
 933                 disableTracking((DisableTrackingPayload) data);
 934                 return;
 935             }
 936
 937             try {
 938                 store.applyReplicatedPayload(identifier, (Payload)data);
 939             } catch (DataValidationFailedException | IOException e) {
 940                 LOG.error("{}: Error applying replica {}", persistenceId(), identifier, e);
 941             }
 942         } else {
 943             LOG.error("{}: Unknown state for {} received {}", persistenceId(), identifier, data);
 944         }
 945     }
 946
 947     @Override
 948     protected void onStateChanged() {
 949         boolean isLeader = isLeader();
 950         boolean hasLeader = hasLeader();
 951         treeChangeSupport.onLeadershipChange(isLeader, hasLeader);
 952
 953         // If this actor is no longer the leader close all the transaction chains
 954         if (!isLeader) {
 955             if (LOG.isDebugEnabled()) {
 956                 LOG.debug(
 957                     "{}: onStateChanged: Closing all transaction chains because shard {} is no longer the leader",
 958                     persistenceId(), getId());
 959             }
 960
 961             paused = false;
 962             store.purgeLeaderState();
 963         }
 964
 965         if (hasLeader && !isIsolatedLeader()) {
 966             messageRetrySupport.retryMessages();
 967         }
 968     }
 969
 970     @Override
 971     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 972         shardMBean.incrementLeadershipChangeCount();
 973         paused = false;
 974
 975         if (!isLeader()) {
 976             if (!knownFrontends.isEmpty()) {
 977                 LOG.debug("{}: removing frontend state for {}", persistenceId(), knownFrontends.keySet());
 978                 knownFrontends = ImmutableMap.of();
 979             }
 980
 981             requestMessageAssembler.close();
 982
 983             if (!hasLeader()) {
 984                 // No leader anywhere, nothing else to do
 985                 return;
 986             }
 987
 988             // Another leader was elected. If we were the previous leader and had pending transactions, convert
 989             // them to transaction messages and send to the new leader.
 990             ActorSelection leader = getLeader();
 991             if (leader != null) {
 992                 Collection<?> messagesToForward = convertPendingTransactionsToMessages();
 993
 994                 if (!messagesToForward.isEmpty()) {
 995                     LOG.debug("{}: Forwarding {} pending transaction messages to leader {}", persistenceId(),
 996                             messagesToForward.size(), leader);
 997
 998                     for (Object message : messagesToForward) {
 999                         LOG.debug("{}: Forwarding pending transaction message {}", persistenceId(), message);
1000
1001                         leader.tell(message, self());
1002                     }
1003                 }
1004             } else {
1005                 commitCoordinator.abortPendingTransactions("The transacton was aborted due to inflight leadership "
1006                         + "change and the leader address isn't available.", this);
1007             }
1008         } else {
1009             // We have become the leader, we need to reconstruct frontend state
1010             knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
1011             LOG.debug("{}: became leader with frontend state for {}", persistenceId(), knownFrontends.keySet());
1012         }
1013
1014         if (!isIsolatedLeader()) {
1015             messageRetrySupport.retryMessages();
1016         }
1017     }
1018
1019     /**
1020      * Clears all pending transactions and converts them to messages to be forwarded to a new leader.
1021      *
1022      * @return the converted messages
1023      */
1024     public Collection<?> convertPendingTransactionsToMessages() {
1025         return commitCoordinator.convertPendingTransactionsToMessages(
1026                 datastoreContext.getShardBatchedModificationCount());
1027     }
1028
1029     @Override
1030     protected void pauseLeader(final Runnable operation) {
1031         LOG.debug("{}: In pauseLeader, operation: {}", persistenceId(), operation);
1032         paused = true;
1033
1034         // Tell-based protocol can replay transaction state, so it is safe to blow it up when we are paused.
1035         knownFrontends.values().forEach(LeaderFrontendState::retire);
1036         knownFrontends = ImmutableMap.of();
1037
1038         store.setRunOnPendingTransactionsComplete(operation);
1039     }
1040
1041     @Override
1042     protected void unpauseLeader() {
1043         LOG.debug("{}: In unpauseLeader", persistenceId());
1044         paused = false;
1045
1046         store.setRunOnPendingTransactionsComplete(null);
1047
1048         // Restore tell-based protocol state as if we were becoming the leader
1049         knownFrontends = Verify.verifyNotNull(frontendMetadata.toLeaderState(this));
1050     }
1051
1052     @Override
1053     protected OnDemandRaftState.AbstractBuilder<?, ?> newOnDemandRaftStateBuilder() {
1054         return OnDemandShardState.newBuilder().treeChangeListenerActors(treeChangeSupport.getListenerActors())
1055                 .commitCohortActors(store.getCohortActors());
1056     }
1057
1058     @Override
1059     public String persistenceId() {
1060         return this.name;
1061     }
1062
1063     @VisibleForTesting
1064     ShardCommitCoordinator getCommitCoordinator() {
1065         return commitCoordinator;
1066     }
1067
1068     public DatastoreContext getDatastoreContext() {
1069         return datastoreContext;
1070     }
1071
1072     @VisibleForTesting
1073     public ShardDataTree getDataStore() {
1074         return store;
1075     }
1076
1077     @VisibleForTesting
1078     ShardStats getShardMBean() {
1079         return shardMBean;
1080     }
1081
1082     public static Builder builder() {
1083         return new Builder();
1084     }
1085
1086     public abstract static class AbstractBuilder<T extends AbstractBuilder<T, S>, S extends Shard> {
1087         private final Class<S> shardClass;
1088         private ShardIdentifier id;
1089         private Map<String, String> peerAddresses = Collections.emptyMap();
1090         private DatastoreContext datastoreContext;
1091         private SchemaContextProvider schemaContextProvider;
1092         private DatastoreSnapshot.ShardSnapshot restoreFromSnapshot;
1093         private DataTree dataTree;
1094         private volatile boolean sealed;
1095
1096         protected AbstractBuilder(final Class<S> shardClass) {
1097             this.shardClass = shardClass;
1098         }
1099
1100         protected void checkSealed() {
1101             Preconditions.checkState(!sealed, "Builder isalready sealed - further modifications are not allowed");
1102         }
1103
1104         @SuppressWarnings("unchecked")
1105         private T self() {
1106             return (T) this;
1107         }
1108
1109         public T id(final ShardIdentifier newId) {
1110             checkSealed();
1111             this.id = newId;
1112             return self();
1113         }
1114
1115         public T peerAddresses(final Map<String, String> newPeerAddresses) {
1116             checkSealed();
1117             this.peerAddresses = newPeerAddresses;
1118             return self();
1119         }
1120
1121         public T datastoreContext(final DatastoreContext newDatastoreContext) {
1122             checkSealed();
1123             this.datastoreContext = newDatastoreContext;
1124             return self();
1125         }
1126
1127         public T schemaContextProvider(final SchemaContextProvider newSchemaContextProvider) {
1128             checkSealed();
1129             this.schemaContextProvider = Preconditions.checkNotNull(newSchemaContextProvider);
1130             return self();
1131         }
1132
1133         public T restoreFromSnapshot(final DatastoreSnapshot.ShardSnapshot newRestoreFromSnapshot) {
1134             checkSealed();
1135             this.restoreFromSnapshot = newRestoreFromSnapshot;
1136             return self();
1137         }
1138
1139         public T dataTree(final DataTree newDataTree) {
1140             checkSealed();
1141             this.dataTree = newDataTree;
1142             return self();
1143         }
1144
1145         public ShardIdentifier getId() {
1146             return id;
1147         }
1148
1149         public Map<String, String> getPeerAddresses() {
1150             return peerAddresses;
1151         }
1152
1153         public DatastoreContext getDatastoreContext() {
1154             return datastoreContext;
1155         }
1156
1157         public SchemaContext getSchemaContext() {
1158             return Verify.verifyNotNull(schemaContextProvider.getSchemaContext());
1159         }
1160
1161         public DatastoreSnapshot.ShardSnapshot getRestoreFromSnapshot() {
1162             return restoreFromSnapshot;
1163         }
1164
1165         public DataTree getDataTree() {
1166             return dataTree;
1167         }
1168
1169         public TreeType getTreeType() {
1170             switch (datastoreContext.getLogicalStoreType()) {
1171                 case CONFIGURATION:
1172                     return TreeType.CONFIGURATION;
1173                 case OPERATIONAL:
1174                     return TreeType.OPERATIONAL;
1175                 default:
1176                     throw new IllegalStateException("Unhandled logical store type "
1177                             + datastoreContext.getLogicalStoreType());
1178             }
1179         }
1180
1181         protected void verify() {
1182             Preconditions.checkNotNull(id, "id should not be null");
1183             Preconditions.checkNotNull(peerAddresses, "peerAddresses should not be null");
1184             Preconditions.checkNotNull(datastoreContext, "dataStoreContext should not be null");
1185             Preconditions.checkNotNull(schemaContextProvider, "schemaContextProvider should not be null");
1186         }
1187
1188         public Props props() {
1189             sealed = true;
1190             verify();
1191             return Props.create(shardClass, this);
1192         }
1193     }
1194
1195     public static class Builder extends AbstractBuilder<Builder, Shard> {
1196         Builder() {
1197             super(Shard.class);
1198         }
1199     }
1200
1201     Ticker ticker() {
1202         return Ticker.systemTicker();
1203     }
1204
1205     void scheduleNextPendingTransaction() {
1206         self().tell(RESUME_NEXT_PENDING_TRANSACTION, ActorRef.noSender());
1207     }
1208 }