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         super.onStateChanged();
 326
 327         boolean isLeader = isLeader();
 328         LOG.debug("{}: onStateChanged: isLeader: {}, hasLeader: {}", persistenceId(), isLeader, hasLeader());
 329
 330         // Examine current RAFT state to see if we are in jeopardy, potentially notifying all listeners
 331         final boolean inJeopardy = inJeopardy(getRaftState());
 332         final boolean wasInJeopardy = listenerSupport.setInJeopardy(inJeopardy);
 333         if (inJeopardy != wasInJeopardy) {
 334             LOG.debug("{}: {} jeopardy state, notifying all listeners", persistenceId(),
 335                 inJeopardy ? "entered" : "left");
 336             notifyAllListeners();
 337         }
 338
 339         commitCoordinator.onStateChanged(this, isLeader);
 340     }
 341
 342     @Override
 343     protected void onLeaderChanged(String oldLeader, String newLeader) {
 344         super.onLeaderChanged(oldLeader, newLeader);
 345
 346         boolean isLeader = isLeader();
 347         LOG.debug("{}: onLeaderChanged: oldLeader: {}, newLeader: {}, isLeader: {}", persistenceId(), oldLeader,
 348                 newLeader, isLeader);
 349
 350         if (isLeader) {
 351
 352             // Clear all existing strategies so that they get re-created when we call createStrategy again
 353             // This allows the strategies to be re-initialized with existing statistics maintained by
 354             // EntityOwnershipStatistics
 355             strategyConfig.clearStrategies();
 356
 357             // Re-assign owners for all members that are known to be down. In a cluster which has greater than
 358             // 3 nodes it is possible for a some node beside the leader being down when the leadership transitions
 359             // it makes sense to use this event to re-assign owners for those downed nodes
 360             for (MemberName downPeerName : downPeerMemberNames) {
 361                 selectNewOwnerForEntitiesOwnedBy(downPeerName);
 362             }
 363         } else {
 364             // The leader changed - notify the coordinator to check if pending modifications need to be sent.
 365             // While onStateChanged also does this, this method handles the case where the shard hears from a
 366             // leader and stays in the follower state. In that case no behavior state change occurs.
 367             commitCoordinator.onStateChanged(this, isLeader);
 368         }
 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             if(message.getRemovedCandidate().equals(currentOwner) || message.getRemainingCandidates().isEmpty()){
 377                 writeNewOwner(message.getEntityPath(),
 378                         newOwner(currentOwner, message.getRemainingCandidates(), getEntityOwnerElectionStrategy(message.getEntityPath())));
 379             }
 380         }
 381     }
 382
 383     private EntityOwnerSelectionStrategy getEntityOwnerElectionStrategy(YangInstanceIdentifier entityPath) {
 384         final String entityType = EntityOwnersModel.entityTypeFromEntityPath(entityPath);
 385         return strategyConfig.createStrategy(entityType, entityOwnershipStatistics.byEntityType(entityType));
 386     }
 387
 388     private void onCandidateAdded(CandidateAdded message) {
 389         if(!isLeader()){
 390             return;
 391         }
 392
 393         LOG.debug("{}: onCandidateAdded: {}", persistenceId(), message);
 394
 395         // Since a node's candidate member is only added by the node itself, we can assume the node is up so
 396         // remove it from the downPeerMemberNames.
 397         downPeerMemberNames.remove(MemberName.forName(message.getNewCandidate()));
 398
 399         final String currentOwner = getCurrentOwner(message.getEntityPath());
 400         final EntityOwnerSelectionStrategy strategy = getEntityOwnerElectionStrategy(message.getEntityPath());
 401
 402         // Available members is all the known peers - the number of peers that are down + self
 403         // So if there are 2 peers and 1 is down then availableMembers will be 2
 404         final int availableMembers = peerIdToMemberNames.size() - downPeerMemberNames.size() + 1;
 405
 406         LOG.debug("{}: Using strategy {} to select owner, currentOwner = {}", persistenceId(), strategy, currentOwner);
 407
 408         if(strategy.getSelectionDelayInMillis() == 0L) {
 409             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 410                     strategy));
 411         } else if(message.getAllCandidates().size() == availableMembers) {
 412             LOG.debug("{}: Received the maximum candidates requests : {} writing new owner",
 413                     persistenceId(), availableMembers);
 414             cancelOwnerSelectionTask(message.getEntityPath());
 415             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 416                     strategy));
 417         } else {
 418             scheduleOwnerSelection(message.getEntityPath(), message.getAllCandidates(), strategy);
 419         }
 420     }
 421
 422     private void onPeerDown(PeerDown peerDown) {
 423         LOG.info("{}: onPeerDown: {}", persistenceId(), peerDown);
 424
 425         MemberName downMemberName = peerDown.getMemberName();
 426         if(downPeerMemberNames.add(downMemberName) && isLeader()) {
 427             // Select new owners for entities owned by the down peer and which have other candidates. For an entity for
 428             // which the down peer is the only candidate, we leave it as the owner and don't clear it. This is done to
 429             // handle the case where the peer member process is actually still running but the node is partitioned.
 430             // When the partition is healed, the peer just remains as the owner. If the peer process actually restarted,
 431             // it will first remove all its candidates on startup. If another candidate is registered during the time
 432             // the peer is down, the new candidate will be selected as the new owner.
 433
 434             selectNewOwnerForEntitiesOwnedBy(downMemberName);
 435         }
 436     }
 437
 438     private void selectNewOwnerForEntitiesOwnedBy(MemberName downMemberName) {
 439         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 440         searchForEntitiesOwnedBy(downMemberName.getName(), (entityTypeNode, entityNode) -> {
 441             YangInstanceIdentifier entityPath = YangInstanceIdentifier.builder(ENTITY_TYPES_PATH).
 442                     node(entityTypeNode.getIdentifier()).node(ENTITY_NODE_ID).node(entityNode.getIdentifier()).
 443                     node(ENTITY_OWNER_NODE_ID).build();
 444             String newOwner = newOwner(getCurrentOwner(entityPath), getCandidateNames(entityNode),
 445                     getEntityOwnerElectionStrategy(entityPath));
 446
 447             if(!newOwner.isEmpty()) {
 448                 LOG.debug("{}: Found entity {}, writing new owner {}", persistenceId(), entityPath, newOwner);
 449
 450                 modifications.addModification(new WriteModification(entityPath,
 451                         ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)));
 452
 453             } else {
 454                 LOG.debug("{}: Found entity {} but no other candidates - not clearing owner", persistenceId(),
 455                         entityPath, newOwner);
 456             }
 457         });
 458
 459         commitCoordinator.commitModifications(modifications, this);
 460     }
 461
 462     private void onPeerUp(PeerUp peerUp) {
 463         LOG.debug("{}: onPeerUp: {}", persistenceId(), peerUp);
 464
 465         peerIdToMemberNames.put(peerUp.getPeerId(), peerUp.getMemberName());
 466         downPeerMemberNames.remove(peerUp.getMemberName());
 467
 468         // Notify the coordinator to check if pending modifications need to be sent. We do this here
 469         // to handle the case where the leader's peer address isn't known yet when a prior state or
 470         // leader change occurred.
 471         commitCoordinator.onStateChanged(this, isLeader());
 472     }
 473
 474     private Collection<String> getCandidateNames(MapEntryNode entity) {
 475         Collection<MapEntryNode> candidates = ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getValue();
 476         Collection<String> candidateNames = new ArrayList<>(candidates.size());
 477         for(MapEntryNode candidate: candidates) {
 478             candidateNames.add(candidate.getChild(CANDIDATE_NAME_NODE_ID).get().getValue().toString());
 479         }
 480
 481         return candidateNames;
 482     }
 483
 484     private void searchForEntitiesOwnedBy(final String owner, final EntityWalker walker) {
 485         LOG.debug("{}: Searching for entities owned by {}", persistenceId(), owner);
 486
 487         searchForEntities((entityTypeNode, entityNode) -> {
 488             Optional<DataContainerChild<? extends PathArgument, ?>> possibleOwner =
 489                     entityNode.getChild(ENTITY_OWNER_NODE_ID);
 490             if(possibleOwner.isPresent() && owner.equals(possibleOwner.get().getValue().toString())) {
 491                 walker.onEntity(entityTypeNode, entityNode);
 492             }
 493         });
 494     }
 495
 496     private void removeCandidateFromEntities(final MemberName member) {
 497         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 498         searchForEntities((entityTypeNode, entityNode) -> {
 499             if (hasCandidate(entityNode, member)) {
 500                 YangInstanceIdentifier entityId =
 501                         (YangInstanceIdentifier) entityNode.getIdentifier().getKeyValues().get(ENTITY_ID_QNAME);
 502                 YangInstanceIdentifier candidatePath = candidatePath(
 503                         entityTypeNode.getIdentifier().getKeyValues().get(ENTITY_TYPE_QNAME).toString(),
 504                         entityId, member.getName());
 505
 506                 LOG.info("{}: Found entity {}, removing candidate {}, path {}", persistenceId(), entityId,
 507                         member, candidatePath);
 508
 509                 modifications.addModification(new DeleteModification(candidatePath));
 510             }
 511         });
 512
 513         commitCoordinator.commitModifications(modifications, this);
 514     }
 515
 516     private static boolean hasCandidate(MapEntryNode entity, MemberName candidateName) {
 517         return ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getChild(candidateNodeKey(candidateName.getName()))
 518                 .isPresent();
 519     }
 520
 521     private void searchForEntities(EntityWalker walker) {
 522         Optional<NormalizedNode<?, ?>> possibleEntityTypes = getDataStore().readNode(ENTITY_TYPES_PATH);
 523         if(!possibleEntityTypes.isPresent()) {
 524             return;
 525         }
 526
 527         for(MapEntryNode entityType:  ((MapNode) possibleEntityTypes.get()).getValue()) {
 528             Optional<DataContainerChild<?, ?>> possibleEntities = entityType.getChild(ENTITY_NODE_ID);
 529             if(!possibleEntities.isPresent()) {
 530                 // shouldn't happen but handle anyway
 531                 continue;
 532             }
 533
 534             for(MapEntryNode entity:  ((MapNode) possibleEntities.get()).getValue()) {
 535                 walker.onEntity(entityType, entity);
 536             }
 537         }
 538     }
 539
 540     private void writeNewOwner(YangInstanceIdentifier entityPath, String newOwner) {
 541         LOG.debug("{}: Writing new owner {} for entity {}", persistenceId(), newOwner, entityPath);
 542
 543         commitCoordinator.commitModification(new WriteModification(entityPath.node(ENTITY_OWNER_QNAME),
 544                 ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)), this);
 545     }
 546
 547     /**
 548      * Schedule a new owner selection job. Cancelling any outstanding job if it has not been cancelled.
 549      *
 550      * @param entityPath
 551      * @param allCandidates
 552      */
 553     public void scheduleOwnerSelection(YangInstanceIdentifier entityPath, Collection<String> allCandidates,
 554                                        EntityOwnerSelectionStrategy strategy){
 555         cancelOwnerSelectionTask(entityPath);
 556
 557         LOG.debug("{}: Scheduling owner selection after {} ms", persistenceId(), strategy.getSelectionDelayInMillis());
 558
 559         final Cancellable lastScheduledTask = context().system().scheduler().scheduleOnce(
 560                 FiniteDuration.apply(strategy.getSelectionDelayInMillis(), TimeUnit.MILLISECONDS)
 561                 , self(), new SelectOwner(entityPath, allCandidates, strategy)
 562                 , context().system().dispatcher(), self());
 563
 564         entityToScheduledOwnershipTask.put(entityPath, lastScheduledTask);
 565     }
 566
 567     private void cancelOwnerSelectionTask(YangInstanceIdentifier entityPath){
 568         final Cancellable lastScheduledTask = entityToScheduledOwnershipTask.get(entityPath);
 569         if(lastScheduledTask != null && !lastScheduledTask.isCancelled()){
 570             lastScheduledTask.cancel();
 571         }
 572     }
 573
 574     private String newOwner(String currentOwner, Collection<String> candidates, EntityOwnerSelectionStrategy ownerSelectionStrategy) {
 575         Collection<String> viableCandidates = getViableCandidates(candidates);
 576         if(viableCandidates.isEmpty()){
 577             return "";
 578         }
 579         return ownerSelectionStrategy.newOwner(currentOwner, viableCandidates);
 580     }
 581
 582     private Collection<String> getViableCandidates(Collection<String> candidates) {
 583         Collection<String> viableCandidates = new ArrayList<>();
 584
 585         for (String candidate : candidates) {
 586             if (!downPeerMemberNames.contains(MemberName.forName(candidate))) {
 587                 viableCandidates.add(candidate);
 588             }
 589         }
 590         return viableCandidates;
 591     }
 592
 593     private String getCurrentOwner(YangInstanceIdentifier entityId) {
 594         Optional<NormalizedNode<?, ?>> optionalEntityOwner = getDataStore().readNode(entityId.node(ENTITY_OWNER_QNAME));
 595         if(optionalEntityOwner.isPresent()){
 596             return optionalEntityOwner.get().getValue().toString();
 597         }
 598         return null;
 599     }
 600
 601     @FunctionalInterface
 602     private interface EntityWalker {
 603         void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode);
 604     }
 605
 606     public static Builder newBuilder() {
 607         return new Builder();
 608     }
 609
 610     static class Builder extends Shard.AbstractBuilder<Builder, EntityOwnershipShard> {
 611         private MemberName localMemberName;
 612         private EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig;
 613
 614         protected Builder() {
 615             super(EntityOwnershipShard.class);
 616         }
 617
 618         Builder localMemberName(MemberName localMemberName) {
 619             checkSealed();
 620             this.localMemberName = localMemberName;
 621             return this;
 622         }
 623
 624         Builder ownerSelectionStrategyConfig(EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig){
 625             checkSealed();
 626             this.ownerSelectionStrategyConfig = ownerSelectionStrategyConfig;
 627             return this;
 628         }
 629
 630         @Override
 631         protected void verify() {
 632             super.verify();
 633             Preconditions.checkNotNull(localMemberName, "localMemberName should not be null");
 634             Preconditions.checkNotNull(ownerSelectionStrategyConfig, "ownerSelectionStrategyConfig should not be null");
 635         }
 636     }
 637 }