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_NAME_NODE_ID;
  11 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.CANDIDATE_NODE_ID;
  12 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_ID_NODE_ID;
  13 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_ID_QNAME;
  14 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_NODE_ID;
  15 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_OWNERS_PATH;
  16 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_OWNER_NODE_ID;
  17 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_OWNER_QNAME;
  18 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_TYPES_PATH;
  19 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_TYPE_NODE_ID;
  20 import static org.opendaylight.controller.cluster.datastore.entityownership.EntityOwnersModel.ENTITY_TYPE_QNAME;
  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.entityOwnersWithCandidate;
  24 import akka.actor.ActorRef;
  25 import akka.actor.ActorSelection;
  26 import akka.actor.Cancellable;
  27 import akka.pattern.Patterns;
  28 import com.google.common.base.Optional;
  29 import com.google.common.base.Preconditions;
  30 import com.google.common.base.Strings;
  31 import java.util.ArrayList;
  32 import java.util.Collection;
  33 import java.util.HashMap;
  34 import java.util.HashSet;
  35 import java.util.Map;
  36 import java.util.Set;
  37 import java.util.concurrent.TimeUnit;
  38 import org.opendaylight.controller.cluster.access.concepts.MemberName;
  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.RemoveAllCandidates;
  46 import org.opendaylight.controller.cluster.datastore.entityownership.messages.SelectOwner;
  47 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterCandidateLocal;
  48 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterListenerLocal;
  49 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategy;
  50 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategyConfig;
  51 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  52 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  53 import org.opendaylight.controller.cluster.datastore.messages.PeerDown;
  54 import org.opendaylight.controller.cluster.datastore.messages.PeerUp;
  55 import org.opendaylight.controller.cluster.datastore.messages.SuccessReply;
  56 import org.opendaylight.controller.cluster.datastore.modification.DeleteModification;
  57 import org.opendaylight.controller.cluster.datastore.modification.MergeModification;
  58 import org.opendaylight.controller.cluster.datastore.modification.WriteModification;
  59 import org.opendaylight.controller.cluster.raft.RaftState;
  60 import org.opendaylight.mdsal.eos.dom.api.DOMEntity;
  61 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  62 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
  63 import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
  64 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  65 import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
  66 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  67 import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
  68 import scala.concurrent.Future;
  69 import scala.concurrent.duration.FiniteDuration;
  70
  71 /**
  72  * Special Shard for EntityOwnership.
  73  *
  74  * @author Thomas Pantelis
  75  */
  76 class EntityOwnershipShard extends Shard {
  77     private final MemberName localMemberName;
  78     private final EntityOwnershipShardCommitCoordinator commitCoordinator;
  79     private final EntityOwnershipListenerSupport listenerSupport;
  80     private final Set<MemberName> downPeerMemberNames = new HashSet<>();
  81     private final Map<String, MemberName> peerIdToMemberNames = new HashMap<>();
  82     private final EntityOwnerSelectionStrategyConfig strategyConfig;
  83     private final Map<YangInstanceIdentifier, Cancellable> entityToScheduledOwnershipTask = new HashMap<>();
  84     private final EntityOwnershipStatistics entityOwnershipStatistics;
  85     private boolean removeAllInitialCandidates = true;
  86
  87     private static DatastoreContext noPersistenceDatastoreContext(DatastoreContext datastoreContext) {
  88         return DatastoreContext.newBuilderFrom(datastoreContext).persistent(false).build();
  89     }
  90
  91     protected EntityOwnershipShard(Builder builder) {
  92         super(builder);
  93         this.localMemberName = builder.localMemberName;
  94         this.commitCoordinator = new EntityOwnershipShardCommitCoordinator(builder.localMemberName, LOG);
  95         this.listenerSupport = new EntityOwnershipListenerSupport(getContext(), persistenceId());
  96         this.strategyConfig = builder.ownerSelectionStrategyConfig;
  97         this.entityOwnershipStatistics = new EntityOwnershipStatistics();
  98         this.entityOwnershipStatistics.init(getDataStore());
  99
 100         for(String peerId: getRaftActorContext().getPeerIds()) {
 101             ShardIdentifier shardId = ShardIdentifier.fromShardIdString(peerId);
 102             peerIdToMemberNames.put(peerId, shardId.getMemberName());
 103         }
 104     }
 105
 106     @Override
 107     protected void onDatastoreContext(DatastoreContext context) {
 108         super.onDatastoreContext(noPersistenceDatastoreContext(context));
 109     }
 110
 111     @Override
 112     protected void onRecoveryComplete() {
 113         super.onRecoveryComplete();
 114
 115         new CandidateListChangeListener(getSelf(), persistenceId()).init(getDataStore());
 116         new EntityOwnerChangeListener(localMemberName, listenerSupport).init(getDataStore());
 117     }
 118
 119     @Override
 120     public void handleNonRaftCommand(final Object message) {
 121         if(message instanceof RegisterCandidateLocal) {
 122             onRegisterCandidateLocal((RegisterCandidateLocal) message);
 123         } else if(message instanceof UnregisterCandidateLocal) {
 124             onUnregisterCandidateLocal((UnregisterCandidateLocal)message);
 125         } else if(message instanceof CandidateAdded){
 126             onCandidateAdded((CandidateAdded) message);
 127         } else if(message instanceof CandidateRemoved){
 128             onCandidateRemoved((CandidateRemoved) message);
 129         } else if(message instanceof PeerDown) {
 130             onPeerDown((PeerDown) message);
 131         } else if(message instanceof PeerUp) {
 132             onPeerUp((PeerUp) message);
 133         } else if(message instanceof RegisterListenerLocal) {
 134             onRegisterListenerLocal((RegisterListenerLocal)message);
 135         } else if(message instanceof UnregisterListenerLocal) {
 136             onUnregisterListenerLocal((UnregisterListenerLocal) message);
 137         } else if(message instanceof SelectOwner) {
 138             onSelectOwner((SelectOwner) message);
 139         } else if(message instanceof RemoveAllCandidates) {
 140             onRemoveAllCandidates((RemoveAllCandidates) message);
 141         } else if(!commitCoordinator.handleMessage(message, this)) {
 142             super.handleNonRaftCommand(message);
 143         }
 144     }
 145
 146     private void onRemoveAllCandidates(RemoveAllCandidates message) {
 147         LOG.debug("{}: onRemoveAllCandidates: {}", persistenceId(), message);
 148
 149         removeCandidateFromEntities(message.getMemberName());
 150     }
 151
 152     private void onSelectOwner(SelectOwner selectOwner) {
 153         LOG.debug("{}: onSelectOwner: {}", persistenceId(), selectOwner);
 154
 155         String currentOwner = getCurrentOwner(selectOwner.getEntityPath());
 156         if(Strings.isNullOrEmpty(currentOwner)) {
 157             writeNewOwner(selectOwner.getEntityPath(), newOwner(currentOwner, selectOwner.getAllCandidates(),
 158                     selectOwner.getOwnerSelectionStrategy()));
 159
 160             Cancellable cancellable = entityToScheduledOwnershipTask.get(selectOwner.getEntityPath());
 161             if(cancellable != null){
 162                 if(!cancellable.isCancelled()){
 163                     cancellable.cancel();
 164                 }
 165                 entityToScheduledOwnershipTask.remove(selectOwner.getEntityPath());
 166             }
 167         }
 168     }
 169
 170     private void onRegisterCandidateLocal(RegisterCandidateLocal registerCandidate) {
 171         LOG.debug("{}: onRegisterCandidateLocal: {}", persistenceId(), registerCandidate);
 172
 173         listenerSupport.setHasCandidateForEntity(registerCandidate.getEntity());
 174
 175         NormalizedNode<?, ?> entityOwners = entityOwnersWithCandidate(registerCandidate.getEntity().getType(),
 176                 registerCandidate.getEntity().getIdentifier(), localMemberName.getName());
 177         commitCoordinator.commitModification(new MergeModification(ENTITY_OWNERS_PATH, entityOwners), this);
 178
 179         getSender().tell(SuccessReply.INSTANCE, getSelf());
 180     }
 181
 182     private void onUnregisterCandidateLocal(UnregisterCandidateLocal unregisterCandidate) {
 183         LOG.debug("{}: onUnregisterCandidateLocal: {}", persistenceId(), unregisterCandidate);
 184
 185         DOMEntity entity = unregisterCandidate.getEntity();
 186         listenerSupport.unsetHasCandidateForEntity(entity);
 187
 188         YangInstanceIdentifier candidatePath = candidatePath(entity.getType(), entity.getIdentifier(), localMemberName.getName());
 189         commitCoordinator.commitModification(new DeleteModification(candidatePath), this);
 190
 191         getSender().tell(SuccessReply.INSTANCE, getSelf());
 192     }
 193
 194     private void onRegisterListenerLocal(final RegisterListenerLocal registerListener) {
 195         LOG.debug("{}: onRegisterListenerLocal: {}", persistenceId(), registerListener);
 196
 197         listenerSupport.addEntityOwnershipListener(registerListener.getEntityType(), registerListener.getListener());
 198
 199         getSender().tell(SuccessReply.INSTANCE, getSelf());
 200
 201         searchForEntities((entityTypeNode, entityNode) -> {
 202             Optional<DataContainerChild<?, ?>> possibleType = entityTypeNode.getChild(ENTITY_TYPE_NODE_ID);
 203             String entityType = possibleType.isPresent() ? possibleType.get().getValue().toString() : null;
 204             if (registerListener.getEntityType().equals(entityType)) {
 205                 final boolean hasOwner;
 206                 final boolean isOwner;
 207
 208                 Optional<DataContainerChild<?, ?>> possibleOwner = entityNode.getChild(ENTITY_OWNER_NODE_ID);
 209                 if (possibleOwner.isPresent()) {
 210                     isOwner = localMemberName.getName().equals(possibleOwner.get().getValue().toString());
 211                     hasOwner = true;
 212                 } else {
 213                     isOwner = false;
 214                     hasOwner = false;
 215                 }
 216
 217                 DOMEntity entity = new DOMEntity(entityType,
 218                     (YangInstanceIdentifier) entityNode.getChild(ENTITY_ID_NODE_ID).get().getValue());
 219
 220                 listenerSupport.notifyEntityOwnershipListener(entity, false, isOwner, hasOwner,
 221                     registerListener.getListener());
 222             }
 223         });
 224     }
 225
 226     private void onUnregisterListenerLocal(UnregisterListenerLocal unregisterListener) {
 227         LOG.debug("{}: onUnregisterListenerLocal: {}", persistenceId(), unregisterListener);
 228
 229         listenerSupport.removeEntityOwnershipListener(unregisterListener.getEntityType(), unregisterListener.getListener());
 230
 231         getSender().tell(SuccessReply.INSTANCE, getSelf());
 232     }
 233
 234     void tryCommitModifications(final BatchedModifications modifications) {
 235         if(isLeader()) {
 236             LOG.debug("{}: Committing BatchedModifications {} locally", persistenceId(), modifications.getTransactionID());
 237
 238             // Note that it's possible the commit won't get consensus and will timeout and not be applied
 239             // to the state. However we don't need to retry it in that case b/c it will be committed to
 240             // the journal first and, once a majority of followers come back on line and it is replicated,
 241             // it will be applied at that point.
 242             handleBatchedModificationsLocal(modifications, self());
 243         } else {
 244             final ActorSelection leader = getLeader();
 245             if (leader != null) {
 246                 possiblyRemoveAllInitialCandidates(leader);
 247
 248                 if(LOG.isDebugEnabled()) {
 249                     LOG.debug("{}: Sending BatchedModifications {} to leader {}", persistenceId(),
 250                             modifications.getTransactionID(), leader);
 251                 }
 252
 253                 Future<Object> future = Patterns.ask(leader, modifications, TimeUnit.SECONDS.toMillis(
 254                         getDatastoreContext().getShardTransactionCommitTimeoutInSeconds()));
 255
 256                 Patterns.pipe(future, getContext().dispatcher()).pipeTo(getSelf(), ActorRef.noSender());
 257             }
 258         }
 259     }
 260
 261     void possiblyRemoveAllInitialCandidates(ActorSelection leader) {
 262         // The following handles removing all candidates on startup when re-joining with a remote leader. When a
 263         // follower is detected as down, the leader will re-assign new owners to entities that were owned by the
 264         // down member but doesn't remove the down member as a candidate, as the down node may actually be isolated
 265         // and still running. Therefore on startup we send an initial message to the remote leader to remove any
 266         // potential stale candidates we had previously registered, as it's possible a candidate may not be
 267         // registered by a client in the new incarnation. We have to send the RemoveAllCandidates message prior to any
 268         // pending registrations.
 269         if(removeAllInitialCandidates && leader != null) {
 270             removeAllInitialCandidates = false;
 271             if(!isLeader()) {
 272                 LOG.debug("{} - got new leader {} on startup - sending RemoveAllCandidates", persistenceId(), leader);
 273
 274                 leader.tell(new RemoveAllCandidates(localMemberName), ActorRef.noSender());
 275             }
 276         }
 277     }
 278
 279     boolean hasLeader() {
 280         return getLeader() != null && (!isLeader() || isLeaderActive());
 281     }
 282
 283     /**
 284      * Determine if we are in jeopardy based on observed RAFT state.
 285      */
 286     private static boolean inJeopardy(final RaftState state) {
 287         switch (state) {
 288             case Candidate:
 289             case Follower:
 290             case Leader:
 291             case PreLeader:
 292                 return false;
 293             case IsolatedLeader:
 294                 return true;
 295         }
 296         throw new IllegalStateException("Unsupported RAFT state " + state);
 297     }
 298
 299     private void notifyAllListeners() {
 300         searchForEntities((entityTypeNode, entityNode) -> {
 301             Optional<DataContainerChild<?, ?>> possibleType = entityTypeNode.getChild(ENTITY_TYPE_NODE_ID);
 302             if (possibleType.isPresent()) {
 303                 final boolean hasOwner;
 304                 final boolean isOwner;
 305
 306                 Optional<DataContainerChild<?, ?>> possibleOwner = entityNode.getChild(ENTITY_OWNER_NODE_ID);
 307                 if (possibleOwner.isPresent()) {
 308                     isOwner = localMemberName.getName().equals(possibleOwner.get().getValue().toString());
 309                     hasOwner = true;
 310                 } else {
 311                     isOwner = false;
 312                     hasOwner = false;
 313                 }
 314
 315                 DOMEntity entity = new DOMEntity(possibleType.get().getValue().toString(),
 316                     (YangInstanceIdentifier) entityNode.getChild(ENTITY_ID_NODE_ID).get().getValue());
 317
 318                 listenerSupport.notifyEntityOwnershipListeners(entity, isOwner, isOwner, hasOwner);
 319             }
 320         });
 321     }
 322
 323     @Override
 324     protected void onStateChanged() {
 325         boolean isLeader = isLeader();
 326         LOG.debug("{}: onStateChanged: isLeader: {}, hasLeader: {}", persistenceId(), isLeader, hasLeader());
 327
 328         // Examine current RAFT state to see if we are in jeopardy, potentially notifying all listeners
 329         final boolean inJeopardy = inJeopardy(getRaftState());
 330         final boolean wasInJeopardy = listenerSupport.setInJeopardy(inJeopardy);
 331         if (inJeopardy != wasInJeopardy) {
 332             LOG.debug("{}: {} jeopardy state, notifying all listeners", persistenceId(),
 333                 inJeopardy ? "entered" : "left");
 334             notifyAllListeners();
 335         }
 336
 337         commitCoordinator.onStateChanged(this, isLeader);
 338
 339         super.onStateChanged();
 340     }
 341
 342     @Override
 343     protected void onLeaderChanged(String oldLeader, String newLeader) {
 344         boolean isLeader = isLeader();
 345         LOG.debug("{}: onLeaderChanged: oldLeader: {}, newLeader: {}, isLeader: {}", persistenceId(), oldLeader,
 346                 newLeader, isLeader);
 347
 348         if (isLeader) {
 349
 350             // Clear all existing strategies so that they get re-created when we call createStrategy again
 351             // This allows the strategies to be re-initialized with existing statistics maintained by
 352             // EntityOwnershipStatistics
 353             strategyConfig.clearStrategies();
 354
 355             // Re-assign owners for all members that are known to be down. In a cluster which has greater than
 356             // 3 nodes it is possible for a some node beside the leader being down when the leadership transitions
 357             // it makes sense to use this event to re-assign owners for those downed nodes
 358             for (MemberName downPeerName : downPeerMemberNames) {
 359                 selectNewOwnerForEntitiesOwnedBy(downPeerName);
 360             }
 361         } else {
 362             // The leader changed - notify the coordinator to check if pending modifications need to be sent.
 363             // While onStateChanged also does this, this method handles the case where the shard hears from a
 364             // leader and stays in the follower state. In that case no behavior state change occurs.
 365             commitCoordinator.onStateChanged(this, isLeader);
 366         }
 367
 368         super.onLeaderChanged(oldLeader, newLeader);
 369     }
 370
 371     private void onCandidateRemoved(CandidateRemoved message) {
 372         LOG.debug("{}: onCandidateRemoved: {}", persistenceId(), message);
 373
 374         if(isLeader()) {
 375             String currentOwner = getCurrentOwner(message.getEntityPath());
 376             writeNewOwner(message.getEntityPath(),
 377                     newOwner(currentOwner, message.getRemainingCandidates(), getEntityOwnerElectionStrategy(message.getEntityPath())));
 378         }
 379     }
 380
 381     private EntityOwnerSelectionStrategy getEntityOwnerElectionStrategy(YangInstanceIdentifier entityPath) {
 382         final String entityType = EntityOwnersModel.entityTypeFromEntityPath(entityPath);
 383         return strategyConfig.createStrategy(entityType, entityOwnershipStatistics.byEntityType(entityType));
 384     }
 385
 386     private void onCandidateAdded(CandidateAdded message) {
 387         if(!isLeader()){
 388             return;
 389         }
 390
 391         LOG.debug("{}: onCandidateAdded: {}", persistenceId(), message);
 392
 393         // Since a node's candidate member is only added by the node itself, we can assume the node is up so
 394         // remove it from the downPeerMemberNames.
 395         downPeerMemberNames.remove(MemberName.forName(message.getNewCandidate()));
 396
 397         final String currentOwner = getCurrentOwner(message.getEntityPath());
 398         final EntityOwnerSelectionStrategy strategy = getEntityOwnerElectionStrategy(message.getEntityPath());
 399
 400         // Available members is all the known peers - the number of peers that are down + self
 401         // So if there are 2 peers and 1 is down then availableMembers will be 2
 402         final int availableMembers = peerIdToMemberNames.size() - downPeerMemberNames.size() + 1;
 403
 404         LOG.debug("{}: Using strategy {} to select owner, currentOwner = {}", persistenceId(), strategy, currentOwner);
 405
 406         if(strategy.getSelectionDelayInMillis() == 0L) {
 407             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 408                     strategy));
 409         } else if(message.getAllCandidates().size() == availableMembers) {
 410             LOG.debug("{}: Received the maximum candidates requests : {} writing new owner",
 411                     persistenceId(), availableMembers);
 412             cancelOwnerSelectionTask(message.getEntityPath());
 413             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 414                     strategy));
 415         } else {
 416             scheduleOwnerSelection(message.getEntityPath(), message.getAllCandidates(), strategy);
 417         }
 418     }
 419
 420     private void onPeerDown(PeerDown peerDown) {
 421         LOG.info("{}: onPeerDown: {}", persistenceId(), peerDown);
 422
 423         MemberName downMemberName = peerDown.getMemberName();
 424         if(downPeerMemberNames.add(downMemberName) && isLeader()) {
 425             // Select new owners for entities owned by the down peer and which have other candidates. For an entity for
 426             // which the down peer is the only candidate, we leave it as the owner and don't clear it. This is done to
 427             // handle the case where the peer member process is actually still running but the node is partitioned.
 428             // When the partition is healed, the peer just remains as the owner. If the peer process actually restarted,
 429             // it will first remove all its candidates on startup. If another candidate is registered during the time
 430             // the peer is down, the new candidate will be selected as the new owner.
 431
 432             selectNewOwnerForEntitiesOwnedBy(downMemberName);
 433         }
 434     }
 435
 436     private void selectNewOwnerForEntitiesOwnedBy(MemberName downMemberName) {
 437         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 438         searchForEntitiesOwnedBy(downMemberName.getName(), (entityTypeNode, entityNode) -> {
 439             YangInstanceIdentifier entityPath = YangInstanceIdentifier.builder(ENTITY_TYPES_PATH).
 440                     node(entityTypeNode.getIdentifier()).node(ENTITY_NODE_ID).node(entityNode.getIdentifier()).
 441                     node(ENTITY_OWNER_NODE_ID).build();
 442             String newOwner = newOwner(getCurrentOwner(entityPath), getCandidateNames(entityNode),
 443                     getEntityOwnerElectionStrategy(entityPath));
 444
 445             if(!newOwner.isEmpty()) {
 446                 LOG.debug("{}: Found entity {}, writing new owner {}", persistenceId(), entityPath, newOwner);
 447
 448                 modifications.addModification(new WriteModification(entityPath,
 449                         ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)));
 450
 451             } else {
 452                 LOG.debug("{}: Found entity {} but no other candidates - not clearing owner", persistenceId(),
 453                         entityPath, newOwner);
 454             }
 455         });
 456
 457         commitCoordinator.commitModifications(modifications, this);
 458     }
 459
 460     private void onPeerUp(PeerUp peerUp) {
 461         LOG.debug("{}: onPeerUp: {}", persistenceId(), peerUp);
 462
 463         peerIdToMemberNames.put(peerUp.getPeerId(), peerUp.getMemberName());
 464         downPeerMemberNames.remove(peerUp.getMemberName());
 465
 466         // Notify the coordinator to check if pending modifications need to be sent. We do this here
 467         // to handle the case where the leader's peer address isn't known yet when a prior state or
 468         // leader change occurred.
 469         commitCoordinator.onStateChanged(this, isLeader());
 470     }
 471
 472     private Collection<String> getCandidateNames(MapEntryNode entity) {
 473         Collection<MapEntryNode> candidates = ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getValue();
 474         Collection<String> candidateNames = new ArrayList<>(candidates.size());
 475         for(MapEntryNode candidate: candidates) {
 476             candidateNames.add(candidate.getChild(CANDIDATE_NAME_NODE_ID).get().getValue().toString());
 477         }
 478
 479         return candidateNames;
 480     }
 481
 482     private void searchForEntitiesOwnedBy(final String owner, final EntityWalker walker) {
 483         LOG.debug("{}: Searching for entities owned by {}", persistenceId(), owner);
 484
 485         searchForEntities((entityTypeNode, entityNode) -> {
 486             Optional<DataContainerChild<? extends PathArgument, ?>> possibleOwner =
 487                     entityNode.getChild(ENTITY_OWNER_NODE_ID);
 488             if(possibleOwner.isPresent() && owner.equals(possibleOwner.get().getValue().toString())) {
 489                 walker.onEntity(entityTypeNode, entityNode);
 490             }
 491         });
 492     }
 493
 494     private void removeCandidateFromEntities(final MemberName member) {
 495         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 496         searchForEntities((entityTypeNode, entityNode) -> {
 497             if (hasCandidate(entityNode, member)) {
 498                 YangInstanceIdentifier entityId =
 499                         (YangInstanceIdentifier) entityNode.getIdentifier().getKeyValues().get(ENTITY_ID_QNAME);
 500                 YangInstanceIdentifier candidatePath = candidatePath(
 501                         entityTypeNode.getIdentifier().getKeyValues().get(ENTITY_TYPE_QNAME).toString(),
 502                         entityId, member.getName());
 503
 504                 LOG.info("{}: Found entity {}, removing candidate {}, path {}", persistenceId(), entityId,
 505                         member, candidatePath);
 506
 507                 modifications.addModification(new DeleteModification(candidatePath));
 508             }
 509         });
 510
 511         commitCoordinator.commitModifications(modifications, this);
 512     }
 513
 514     private static boolean hasCandidate(MapEntryNode entity, MemberName candidateName) {
 515         return ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getChild(candidateNodeKey(candidateName.getName()))
 516                 .isPresent();
 517     }
 518
 519     private void searchForEntities(EntityWalker walker) {
 520         Optional<NormalizedNode<?, ?>> possibleEntityTypes = getDataStore().readNode(ENTITY_TYPES_PATH);
 521         if(!possibleEntityTypes.isPresent()) {
 522             return;
 523         }
 524
 525         for(MapEntryNode entityType:  ((MapNode) possibleEntityTypes.get()).getValue()) {
 526             Optional<DataContainerChild<?, ?>> possibleEntities = entityType.getChild(ENTITY_NODE_ID);
 527             if(!possibleEntities.isPresent()) {
 528                 // shouldn't happen but handle anyway
 529                 continue;
 530             }
 531
 532             for(MapEntryNode entity:  ((MapNode) possibleEntities.get()).getValue()) {
 533                 walker.onEntity(entityType, entity);
 534             }
 535         }
 536     }
 537
 538     private void writeNewOwner(YangInstanceIdentifier entityPath, String newOwner) {
 539         LOG.debug("{}: Writing new owner {} for entity {}", persistenceId(), newOwner, entityPath);
 540
 541         commitCoordinator.commitModification(new WriteModification(entityPath.node(ENTITY_OWNER_QNAME),
 542                 ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)), this);
 543     }
 544
 545     /**
 546      * Schedule a new owner selection job. Cancelling any outstanding job if it has not been cancelled.
 547      *
 548      * @param entityPath
 549      * @param allCandidates
 550      */
 551     public void scheduleOwnerSelection(YangInstanceIdentifier entityPath, Collection<String> allCandidates,
 552                                        EntityOwnerSelectionStrategy strategy){
 553         cancelOwnerSelectionTask(entityPath);
 554
 555         LOG.debug("{}: Scheduling owner selection after {} ms", persistenceId(), strategy.getSelectionDelayInMillis());
 556
 557         final Cancellable lastScheduledTask = context().system().scheduler().scheduleOnce(
 558                 FiniteDuration.apply(strategy.getSelectionDelayInMillis(), TimeUnit.MILLISECONDS)
 559                 , self(), new SelectOwner(entityPath, allCandidates, strategy)
 560                 , context().system().dispatcher(), self());
 561
 562         entityToScheduledOwnershipTask.put(entityPath, lastScheduledTask);
 563     }
 564
 565     private void cancelOwnerSelectionTask(YangInstanceIdentifier entityPath){
 566         final Cancellable lastScheduledTask = entityToScheduledOwnershipTask.get(entityPath);
 567         if(lastScheduledTask != null && !lastScheduledTask.isCancelled()){
 568             lastScheduledTask.cancel();
 569         }
 570     }
 571
 572     private String newOwner(String currentOwner, Collection<String> candidates, EntityOwnerSelectionStrategy ownerSelectionStrategy) {
 573         Collection<String> viableCandidates = getViableCandidates(candidates);
 574         if(viableCandidates.isEmpty()){
 575             return "";
 576         }
 577         return ownerSelectionStrategy.newOwner(currentOwner, viableCandidates);
 578     }
 579
 580     private Collection<String> getViableCandidates(Collection<String> candidates) {
 581         Collection<String> viableCandidates = new ArrayList<>();
 582
 583         for (String candidate : candidates) {
 584             if (!downPeerMemberNames.contains(MemberName.forName(candidate))) {
 585                 viableCandidates.add(candidate);
 586             }
 587         }
 588         return viableCandidates;
 589     }
 590
 591     private String getCurrentOwner(YangInstanceIdentifier entityId) {
 592         Optional<NormalizedNode<?, ?>> optionalEntityOwner = getDataStore().readNode(entityId.node(ENTITY_OWNER_QNAME));
 593         if(optionalEntityOwner.isPresent()){
 594             return optionalEntityOwner.get().getValue().toString();
 595         }
 596         return null;
 597     }
 598
 599     @FunctionalInterface
 600     private interface EntityWalker {
 601         void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode);
 602     }
 603
 604     public static Builder newBuilder() {
 605         return new Builder();
 606     }
 607
 608     static class Builder extends Shard.AbstractBuilder<Builder, EntityOwnershipShard> {
 609         private MemberName localMemberName;
 610         private EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig;
 611
 612         protected Builder() {
 613             super(EntityOwnershipShard.class);
 614         }
 615
 616         Builder localMemberName(MemberName localMemberName) {
 617             checkSealed();
 618             this.localMemberName = localMemberName;
 619             return this;
 620         }
 621
 622         Builder ownerSelectionStrategyConfig(EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig){
 623             checkSealed();
 624             this.ownerSelectionStrategyConfig = ownerSelectionStrategyConfig;
 625             return this;
 626         }
 627
 628         @Override
 629         protected void verify() {
 630             super.verify();
 631             Preconditions.checkNotNull(localMemberName, "localMemberName should not be null");
 632             Preconditions.checkNotNull(ownerSelectionStrategyConfig, "ownerSelectionStrategyConfig should not be null");
 633         }
 634     }
 635 }