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

   1 /*
   2  * Copyright (c) 2015 Brocade Communications 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.entityownership;
   9
  10 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.CANDIDATE_NODE_ID;
  11 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_ID_NODE_ID;
  12 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_ID_QNAME;
  13 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_NODE_ID;
  14 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_OWNERS_PATH;
  15 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_OWNER_NODE_ID;
  16 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_OWNER_QNAME;
  17 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_TYPES_PATH;
  18 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_TYPE_NODE_ID;
  19 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_TYPE_QNAME;
  20 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.candidateMapEntry;
  21 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.candidateNodeKey;
  22 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.candidatePath;
  23 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.createEntity;
  24 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.entityOwnersWithCandidate;
  25 import akka.actor.ActorRef;
  26 import akka.actor.ActorSelection;
  27 import akka.actor.Cancellable;
  28 import akka.pattern.Patterns;
  29 import com.google.common.base.Optional;
  30 import com.google.common.base.Preconditions;
  31 import com.google.common.base.Strings;
  32 import java.util.ArrayList;
  33 import java.util.Collection;
  34 import java.util.HashMap;
  35 import java.util.HashSet;
  36 import java.util.Map;
  37 import java.util.Set;
  38 import java.util.concurrent.TimeUnit;
  39 import org.opendaylight.controller.cluster.datastore.DatastoreContext;
  40 import org.opendaylight.controller.cluster.datastore.Shard;
  41 import org.opendaylight.controller.cluster.datastore.entityownership.messages.CandidateAdded;
  42 import org.opendaylight.controller.cluster.datastore.entityownership.messages.CandidateRemoved;
  43 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RegisterCandidateLocal;
  44 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RegisterListenerLocal;
  45 import org.opendaylight.controller.cluster.datastore.entityownership.messages.SelectOwner;
  46 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterCandidateLocal;
  47 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterListenerLocal;
  48 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategy;
  49 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategyConfig;
  50 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  51 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  52 import org.opendaylight.controller.cluster.datastore.messages.PeerDown;
  53 import org.opendaylight.controller.cluster.datastore.messages.PeerUp;
  54 import org.opendaylight.controller.cluster.datastore.messages.SuccessReply;
  55 import org.opendaylight.controller.cluster.datastore.modification.DeleteModification;
  56 import org.opendaylight.controller.cluster.datastore.modification.MergeModification;
  57 import org.opendaylight.controller.cluster.datastore.modification.WriteModification;
  58 import org.opendaylight.controller.md.sal.common.api.clustering.Entity;
  59 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  60 import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
  61 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  62 import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
  63 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  64 import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
  65 import scala.concurrent.Future;
  66 import scala.concurrent.duration.FiniteDuration;
  67
  68 /**
  69  * Special Shard for EntityOwnership.
  70  *
  71  * @author Thomas Pantelis
  72  */
  73 class EntityOwnershipShard extends Shard {
  74     private final String localMemberName;
  75     private final EntityOwnershipShardCommitCoordinator commitCoordinator;
  76     private final EntityOwnershipListenerSupport listenerSupport;
  77     private final Set<String> downPeerMemberNames = new HashSet<>();
  78     private final Map<String, String> peerIdToMemberNames = new HashMap<>();
  79     private final EntityOwnerSelectionStrategyConfig strategyConfig;
  80     private final Map<YangInstanceIdentifier, Cancellable> entityToScheduledOwnershipTask = new HashMap<>();
  81     private final EntityOwnershipStatistics entityOwnershipStatistics;
  82
  83     private static DatastoreContext noPersistenceDatastoreContext(DatastoreContext datastoreContext) {
  84         return DatastoreContext.newBuilderFrom(datastoreContext).persistent(false).build();
  85     }
  86
  87     protected EntityOwnershipShard(Builder builder) {
  88         super(builder);
  89         this.localMemberName = builder.localMemberName;
  90         this.commitCoordinator = new EntityOwnershipShardCommitCoordinator(builder.localMemberName, LOG);
  91         this.listenerSupport = new EntityOwnershipListenerSupport(getContext(), persistenceId());
  92         this.strategyConfig = builder.ownerSelectionStrategyConfig;
  93         this.entityOwnershipStatistics = new EntityOwnershipStatistics();
  94         this.entityOwnershipStatistics.init(getDataStore());
  95
  96         for(String peerId: getRaftActorContext().getPeerIds()) {
  97             ShardIdentifier shardId = ShardIdentifier.builder().fromShardIdString(peerId).build();
  98             peerIdToMemberNames.put(peerId, shardId.getMemberName());
  99         }
 100     }
 101
 102     @Override
 103     protected void onDatastoreContext(DatastoreContext context) {
 104         super.onDatastoreContext(noPersistenceDatastoreContext(context));
 105     }
 106
 107     @Override
 108     protected void onRecoveryComplete() {
 109         super.onRecoveryComplete();
 110
 111         new CandidateListChangeListener(getSelf(), persistenceId()).init(getDataStore());
 112         new EntityOwnerChangeListener(localMemberName, listenerSupport).init(getDataStore());
 113     }
 114
 115     @Override
 116     public void onReceiveCommand(final Object message) throws Exception {
 117         if(message instanceof RegisterCandidateLocal) {
 118             onRegisterCandidateLocal((RegisterCandidateLocal) message);
 119         } else if(message instanceof UnregisterCandidateLocal) {
 120             onUnregisterCandidateLocal((UnregisterCandidateLocal)message);
 121         } else if(message instanceof CandidateAdded){
 122             onCandidateAdded((CandidateAdded) message);
 123         } else if(message instanceof CandidateRemoved){
 124             onCandidateRemoved((CandidateRemoved) message);
 125         } else if(message instanceof PeerDown) {
 126             onPeerDown((PeerDown) message);
 127         } else if(message instanceof PeerUp) {
 128             onPeerUp((PeerUp) message);
 129         } else if(message instanceof RegisterListenerLocal) {
 130             onRegisterListenerLocal((RegisterListenerLocal)message);
 131         } else if(message instanceof UnregisterListenerLocal) {
 132             onUnregisterListenerLocal((UnregisterListenerLocal) message);
 133         } else if(message instanceof SelectOwner) {
 134             onSelectOwner((SelectOwner) message);
 135         } else if(!commitCoordinator.handleMessage(message, this)) {
 136             super.onReceiveCommand(message);
 137         }
 138     }
 139
 140     private void onSelectOwner(SelectOwner selectOwner) {
 141         LOG.debug("{}: onSelectOwner: {}", persistenceId(), selectOwner);
 142
 143         String currentOwner = getCurrentOwner(selectOwner.getEntityPath());
 144         if(Strings.isNullOrEmpty(currentOwner)) {
 145             String entityType = EntityOwnersModel.entityTypeFromEntityPath(selectOwner.getEntityPath());
 146             writeNewOwner(selectOwner.getEntityPath(), newOwner(currentOwner, selectOwner.getAllCandidates(),
 147                     entityOwnershipStatistics.byEntityType(entityType),
 148                     selectOwner.getOwnerSelectionStrategy()));
 149
 150             Cancellable cancellable = entityToScheduledOwnershipTask.get(selectOwner.getEntityPath());
 151             if(cancellable != null){
 152                 if(!cancellable.isCancelled()){
 153                     cancellable.cancel();
 154                 }
 155                 entityToScheduledOwnershipTask.remove(selectOwner.getEntityPath());
 156             }
 157         }
 158     }
 159
 160     private void onRegisterCandidateLocal(RegisterCandidateLocal registerCandidate) {
 161         LOG.debug("{}: onRegisterCandidateLocal: {}", persistenceId(), registerCandidate);
 162
 163         listenerSupport.setHasCandidateForEntity(registerCandidate.getEntity());
 164
 165         NormalizedNode<?, ?> entityOwners = entityOwnersWithCandidate(registerCandidate.getEntity().getType(),
 166                 registerCandidate.getEntity().getId(), localMemberName);
 167         commitCoordinator.commitModification(new MergeModification(ENTITY_OWNERS_PATH, entityOwners), this);
 168
 169         getSender().tell(SuccessReply.INSTANCE, getSelf());
 170     }
 171
 172     private void onUnregisterCandidateLocal(UnregisterCandidateLocal unregisterCandidate) {
 173         LOG.debug("{}: onUnregisterCandidateLocal: {}", persistenceId(), unregisterCandidate);
 174
 175         Entity entity = unregisterCandidate.getEntity();
 176         listenerSupport.unsetHasCandidateForEntity(entity);
 177
 178         YangInstanceIdentifier candidatePath = candidatePath(entity.getType(), entity.getId(), localMemberName);
 179         commitCoordinator.commitModification(new DeleteModification(candidatePath), this);
 180
 181         getSender().tell(SuccessReply.INSTANCE, getSelf());
 182     }
 183
 184     private void onRegisterListenerLocal(final RegisterListenerLocal registerListener) {
 185         LOG.debug("{}: onRegisterListenerLocal: {}", persistenceId(), registerListener);
 186
 187         listenerSupport.addEntityOwnershipListener(registerListener.getEntityType(), registerListener.getListener());
 188
 189         getSender().tell(SuccessReply.INSTANCE, getSelf());
 190
 191         searchForEntities(new EntityWalker() {
 192             @Override
 193             public void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode) {
 194                 Optional<DataContainerChild<?, ?>> possibleType = entityTypeNode.getChild(ENTITY_TYPE_NODE_ID);
 195                 String entityType = possibleType.isPresent() ? possibleType.get().getValue().toString() : null;
 196                 if (registerListener.getEntityType().equals(entityType)) {
 197                     final boolean hasOwner;
 198                     final boolean isOwner;
 199
 200                     Optional<DataContainerChild<?, ?>> possibleOwner = entityNode.getChild(ENTITY_OWNER_NODE_ID);
 201                     if (possibleOwner.isPresent()) {
 202                         isOwner = localMemberName.equals(possibleOwner.get().getValue().toString());
 203                         hasOwner = true;
 204                     } else {
 205                         isOwner = false;
 206                         hasOwner = false;
 207                     }
 208
 209                     Entity entity = new Entity(entityType,
 210                         (YangInstanceIdentifier) entityNode.getChild(ENTITY_ID_NODE_ID).get().getValue());
 211
 212                     listenerSupport.notifyEntityOwnershipListener(entity, false, isOwner, hasOwner,
 213                         registerListener.getListener());
 214                 }
 215             }
 216         });
 217     }
 218
 219     private void onUnregisterListenerLocal(UnregisterListenerLocal unregisterListener) {
 220         LOG.debug("{}: onUnregisterListenerLocal: {}", persistenceId(), unregisterListener);
 221
 222         listenerSupport.removeEntityOwnershipListener(unregisterListener.getEntityType(), unregisterListener.getListener());
 223
 224         getSender().tell(SuccessReply.INSTANCE, getSelf());
 225     }
 226
 227     void tryCommitModifications(final BatchedModifications modifications) {
 228         if(isLeader()) {
 229             LOG.debug("{}: Committing BatchedModifications {} locally", persistenceId(), modifications.getTransactionID());
 230
 231             // Note that it's possible the commit won't get consensus and will timeout and not be applied
 232             // to the state. However we don't need to retry it in that case b/c it will be committed to
 233             // the journal first and, once a majority of followers come back on line and it is replicated,
 234             // it will be applied at that point.
 235             handleBatchedModificationsLocal(modifications, self());
 236         } else {
 237             final ActorSelection leader = getLeader();
 238             if (leader != null) {
 239                 if(LOG.isDebugEnabled()) {
 240                     LOG.debug("{}: Sending BatchedModifications {} to leader {}", persistenceId(),
 241                             modifications.getTransactionID(), leader);
 242                 }
 243
 244                 Future<Object> future = Patterns.ask(leader, modifications, TimeUnit.SECONDS.toMillis(
 245                         getDatastoreContext().getShardTransactionCommitTimeoutInSeconds()));
 246
 247                 Patterns.pipe(future, getContext().dispatcher()).pipeTo(getSelf(), ActorRef.noSender());
 248             }
 249         }
 250     }
 251
 252     boolean hasLeader() {
 253         return getLeader() != null && !isIsolatedLeader();
 254     }
 255
 256     @Override
 257     protected void onStateChanged() {
 258         super.onStateChanged();
 259
 260         boolean isLeader = isLeader();
 261         if(LOG.isDebugEnabled()) {
 262             LOG.debug("{}: onStateChanged: isLeader: {}, hasLeader: {}", persistenceId(), isLeader, hasLeader());
 263         }
 264
 265         commitCoordinator.onStateChanged(this, isLeader);
 266     }
 267
 268     @Override
 269     protected void onLeaderChanged(String oldLeader, String newLeader) {
 270         super.onLeaderChanged(oldLeader, newLeader);
 271
 272         boolean isLeader = isLeader();
 273         LOG.debug("{}: onLeaderChanged: oldLeader: {}, newLeader: {}, isLeader: {}", persistenceId(), oldLeader,
 274                 newLeader, isLeader);
 275
 276         if(isLeader) {
 277
 278             // Clear all existing strategies so that they get re-created when we call createStrategy again
 279             // This allows the strategies to be re-initialized with existing statistics maintained by
 280             // EntityOwnershipStatistics
 281             strategyConfig.clearStrategies();
 282             // We were just elected leader. If the old leader is down, select new owners for the entities
 283             // owned by the down leader.
 284
 285             String oldLeaderMemberName = peerIdToMemberNames.get(oldLeader);
 286
 287             LOG.debug("{}: oldLeaderMemberName: {}", persistenceId(), oldLeaderMemberName);
 288
 289             if(downPeerMemberNames.contains(oldLeaderMemberName)) {
 290                 removeCandidateFromEntities(oldLeaderMemberName);
 291             }
 292         } else {
 293             // The leader changed - notify the coordinator to check if pending modifications need to be sent.
 294             // While onStateChanged also does this, this method handles the case where the shard hears from a
 295             // leader and stays in the follower state. In that case no behavior state change occurs.
 296             commitCoordinator.onStateChanged(this, isLeader);
 297         }
 298     }
 299
 300     private void onCandidateRemoved(CandidateRemoved message) {
 301         LOG.debug("{}: onCandidateRemoved: {}", persistenceId(), message);
 302
 303         if(isLeader()) {
 304             String currentOwner = getCurrentOwner(message.getEntityPath());
 305             if(message.getRemovedCandidate().equals(currentOwner) || message.getRemainingCandidates().size() == 0){
 306                 String entityType = EntityOwnersModel.entityTypeFromEntityPath(message.getEntityPath());
 307                 writeNewOwner(message.getEntityPath(),
 308                         newOwner(currentOwner, message.getRemainingCandidates(), entityOwnershipStatistics.byEntityType(entityType),
 309                                 getEntityOwnerElectionStrategy(message.getEntityPath())));
 310             }
 311         } else {
 312             // We're not the leader. If the removed candidate is our local member then check if we actually
 313             // have a local candidate registered. If we do then we must have been partitioned from the leader
 314             // and the leader removed our candidate since the leader can't tell the difference between a
 315             // temporary network partition and a node's process actually restarted. So, in that case, re-add
 316             // our candidate.
 317             if(localMemberName.equals(message.getRemovedCandidate()) &&
 318                     listenerSupport.hasCandidateForEntity(createEntity(message.getEntityPath()))) {
 319                 LOG.debug("Local candidate member was removed but a local candidate is registered for {}" +
 320                     " - adding back local candidate", message.getEntityPath());
 321
 322                 commitCoordinator.commitModification(new MergeModification(
 323                         candidatePath(message.getEntityPath(), localMemberName),
 324                         candidateMapEntry(localMemberName)), this);
 325             }
 326         }
 327     }
 328
 329     private EntityOwnerSelectionStrategy getEntityOwnerElectionStrategy(YangInstanceIdentifier entityPath) {
 330         final String entityType = EntityOwnersModel.entityTypeFromEntityPath(entityPath);
 331         return strategyConfig.createStrategy(entityType, entityOwnershipStatistics.byEntityType(entityType));
 332     }
 333
 334     private void onCandidateAdded(CandidateAdded message) {
 335         if(!isLeader()){
 336             return;
 337         }
 338
 339         LOG.debug("{}: onCandidateAdded: {}", persistenceId(), message);
 340
 341         // Since a node's candidate member is only added by the node itself, we can assume the node is up so
 342         // remove it from the downPeerMemberNames.
 343         downPeerMemberNames.remove(message.getNewCandidate());
 344
 345         final String currentOwner = getCurrentOwner(message.getEntityPath());
 346         final EntityOwnerSelectionStrategy strategy = getEntityOwnerElectionStrategy(message.getEntityPath());
 347         final String entityType = EntityOwnersModel.entityTypeFromEntityPath(message.getEntityPath());
 348
 349         // Available members is all the known peers - the number of peers that are down + self
 350         // So if there are 2 peers and 1 is down then availableMembers will be 2
 351         final int availableMembers = (peerIdToMemberNames.size() - downPeerMemberNames.size()) + 1;
 352
 353         LOG.debug("{}: Using strategy {} to select owner", persistenceId(), strategy);
 354         if(Strings.isNullOrEmpty(currentOwner)){
 355             if(strategy.getSelectionDelayInMillis() == 0L) {
 356                 writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 357                         entityOwnershipStatistics.byEntityType(entityType), strategy));
 358             } else if(message.getAllCandidates().size() == availableMembers) {
 359                 LOG.debug("{}: Received the maximum candidates requests : {} writing new owner",
 360                         persistenceId(), availableMembers);
 361                 cancelOwnerSelectionTask(message.getEntityPath());
 362                 writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 363                         entityOwnershipStatistics.byEntityType(entityType), strategy));
 364             } else {
 365                 scheduleOwnerSelection(message.getEntityPath(), message.getAllCandidates(), strategy);
 366             }
 367         }
 368     }
 369
 370     private void onPeerDown(PeerDown peerDown) {
 371         LOG.info("{}: onPeerDown: {}", persistenceId(), peerDown);
 372
 373         String downMemberName = peerDown.getMemberName();
 374         if(downPeerMemberNames.add(downMemberName) && isLeader()) {
 375             // Remove the down peer as a candidate from all entities.
 376             removeCandidateFromEntities(downMemberName);
 377         }
 378     }
 379
 380     private void onPeerUp(PeerUp peerUp) {
 381         LOG.debug("{}: onPeerUp: {}", persistenceId(), peerUp);
 382
 383         peerIdToMemberNames.put(peerUp.getPeerId(), peerUp.getMemberName());
 384         downPeerMemberNames.remove(peerUp.getMemberName());
 385
 386         // Notify the coordinator to check if pending modifications need to be sent. We do this here
 387         // to handle the case where the leader's peer address isn't now yet when a prior state or
 388         // leader change occurred.
 389         commitCoordinator.onStateChanged(this, isLeader());
 390     }
 391
 392     private void removeCandidateFromEntities(final String owner) {
 393         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 394         searchForEntities(new EntityWalker() {
 395             @Override
 396             public void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode) {
 397                 if (hasCandidate(entityNode, owner)) {
 398                     YangInstanceIdentifier entityId =
 399                             (YangInstanceIdentifier) entityNode.getIdentifier().getKeyValues().get(ENTITY_ID_QNAME);
 400                     YangInstanceIdentifier candidatePath = candidatePath(
 401                             entityTypeNode.getIdentifier().getKeyValues().get(ENTITY_TYPE_QNAME).toString(),
 402                             entityId, owner);
 403
 404                     LOG.info("{}: Found entity {}, removing candidate {}, path {}", persistenceId(), entityId,
 405                             owner, candidatePath);
 406
 407                     modifications.addModification(new DeleteModification(candidatePath));
 408                 }
 409             }
 410         });
 411
 412         commitCoordinator.commitModifications(modifications, this);
 413     }
 414
 415     private static boolean hasCandidate(MapEntryNode entity, String candidateName) {
 416         return ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getChild(candidateNodeKey(candidateName)).isPresent();
 417     }
 418
 419     private void searchForEntities(EntityWalker walker) {
 420         Optional<NormalizedNode<?, ?>> possibleEntityTypes = getDataStore().readNode(ENTITY_TYPES_PATH);
 421         if(!possibleEntityTypes.isPresent()) {
 422             return;
 423         }
 424
 425         for(MapEntryNode entityType:  ((MapNode) possibleEntityTypes.get()).getValue()) {
 426             Optional<DataContainerChild<?, ?>> possibleEntities = entityType.getChild(ENTITY_NODE_ID);
 427             if(!possibleEntities.isPresent()) {
 428                 // shouldn't happen but handle anyway
 429                 continue;
 430             }
 431
 432             for(MapEntryNode entity:  ((MapNode) possibleEntities.get()).getValue()) {
 433                 walker.onEntity(entityType, entity);
 434             }
 435         }
 436     }
 437
 438     private void writeNewOwner(YangInstanceIdentifier entityPath, String newOwner) {
 439         LOG.debug("{}: Writing new owner {} for entity {}", persistenceId(), newOwner, entityPath);
 440
 441         commitCoordinator.commitModification(new WriteModification(entityPath.node(ENTITY_OWNER_QNAME),
 442                 ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)), this);
 443     }
 444
 445     /**
 446      * Schedule a new owner selection job. Cancelling any outstanding job if it has not been cancelled.
 447      *
 448      * @param entityPath
 449      * @param allCandidates
 450      */
 451     public void scheduleOwnerSelection(YangInstanceIdentifier entityPath, Collection<String> allCandidates,
 452                                        EntityOwnerSelectionStrategy strategy){
 453         cancelOwnerSelectionTask(entityPath);
 454
 455         LOG.debug("{}: Scheduling owner selection after {} ms", persistenceId(), strategy.getSelectionDelayInMillis());
 456
 457         final Cancellable lastScheduledTask = context().system().scheduler().scheduleOnce(
 458                 FiniteDuration.apply(strategy.getSelectionDelayInMillis(), TimeUnit.MILLISECONDS)
 459                 , self(), new SelectOwner(entityPath, allCandidates, strategy)
 460                 , context().system().dispatcher(), self());
 461
 462         entityToScheduledOwnershipTask.put(entityPath, lastScheduledTask);
 463     }
 464
 465     private void cancelOwnerSelectionTask(YangInstanceIdentifier entityPath){
 466         final Cancellable lastScheduledTask = entityToScheduledOwnershipTask.get(entityPath);
 467         if(lastScheduledTask != null && !lastScheduledTask.isCancelled()){
 468             lastScheduledTask.cancel();
 469         }
 470     }
 471
 472     private String newOwner(String currentOwner, Collection<String> candidates, Map<String, Long> statistics, EntityOwnerSelectionStrategy ownerSelectionStrategy) {
 473         Collection<String> viableCandidates = getViableCandidates(candidates);
 474         if(viableCandidates.size() == 0){
 475             return "";
 476         }
 477         return ownerSelectionStrategy.newOwner(currentOwner, viableCandidates);
 478     }
 479
 480     private Collection<String> getViableCandidates(Collection<String> candidates) {
 481         Collection<String> viableCandidates = new ArrayList<>();
 482
 483         for (String candidate : candidates) {
 484             if (!downPeerMemberNames.contains(candidate)) {
 485                 viableCandidates.add(candidate);
 486             }
 487         }
 488         return viableCandidates;
 489     }
 490
 491     private String getCurrentOwner(YangInstanceIdentifier entityId) {
 492         Optional<NormalizedNode<?, ?>> optionalEntityOwner = getDataStore().readNode(entityId.node(ENTITY_OWNER_QNAME));
 493         if(optionalEntityOwner.isPresent()){
 494             return optionalEntityOwner.get().getValue().toString();
 495         }
 496         return null;
 497     }
 498
 499     private static interface EntityWalker {
 500         void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode);
 501     }
 502
 503     public static Builder newBuilder() {
 504         return new Builder();
 505     }
 506
 507     static class Builder extends Shard.AbstractBuilder<Builder, EntityOwnershipShard> {
 508         private String localMemberName;
 509         private EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig;
 510
 511         protected Builder() {
 512             super(EntityOwnershipShard.class);
 513         }
 514
 515         Builder localMemberName(String localMemberName) {
 516             checkSealed();
 517             this.localMemberName = localMemberName;
 518             return this;
 519         }
 520
 521         Builder ownerSelectionStrategyConfig(EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig){
 522             checkSealed();
 523             this.ownerSelectionStrategyConfig = ownerSelectionStrategyConfig;
 524             return this;
 525         }
 526
 527         @Override
 528         protected void verify() {
 529             super.verify();
 530             Preconditions.checkNotNull(localMemberName, "localMemberName should not be null");
 531             Preconditions.checkNotNull(ownerSelectionStrategyConfig, "ownerSelectionStrategyConfig should not be null");
 532         }
 533     }
 534 }