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
  25 import akka.actor.ActorRef;
  26 import akka.actor.ActorSelection;
  27 import akka.actor.Cancellable;
  28 import akka.cluster.Cluster;
  29 import akka.cluster.ClusterEvent.CurrentClusterState;
  30 import akka.cluster.Member;
  31 import akka.cluster.MemberStatus;
  32 import akka.pattern.Patterns;
  33 import com.google.common.base.Optional;
  34 import com.google.common.base.Preconditions;
  35 import com.google.common.base.Strings;
  36 import com.google.common.collect.ImmutableSet;
  37 import java.util.ArrayList;
  38 import java.util.Collection;
  39 import java.util.HashMap;
  40 import java.util.HashSet;
  41 import java.util.List;
  42 import java.util.Map;
  43 import java.util.Set;
  44 import java.util.concurrent.TimeUnit;
  45 import org.opendaylight.controller.cluster.access.concepts.MemberName;
  46 import org.opendaylight.controller.cluster.datastore.DatastoreContext;
  47 import org.opendaylight.controller.cluster.datastore.Shard;
  48 import org.opendaylight.controller.cluster.datastore.entityownership.messages.CandidateAdded;
  49 import org.opendaylight.controller.cluster.datastore.entityownership.messages.CandidateRemoved;
  50 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RegisterCandidateLocal;
  51 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RegisterListenerLocal;
  52 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RemoveAllCandidates;
  53 import org.opendaylight.controller.cluster.datastore.entityownership.messages.SelectOwner;
  54 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterCandidateLocal;
  55 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterListenerLocal;
  56 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategy;
  57 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategyConfig;
  58 import org.opendaylight.controller.cluster.datastore.identifiers.ShardIdentifier;
  59 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  60 import org.opendaylight.controller.cluster.datastore.messages.PeerDown;
  61 import org.opendaylight.controller.cluster.datastore.messages.PeerUp;
  62 import org.opendaylight.controller.cluster.datastore.messages.SuccessReply;
  63 import org.opendaylight.controller.cluster.datastore.modification.DeleteModification;
  64 import org.opendaylight.controller.cluster.datastore.modification.MergeModification;
  65 import org.opendaylight.controller.cluster.datastore.modification.Modification;
  66 import org.opendaylight.controller.cluster.datastore.modification.WriteModification;
  67 import org.opendaylight.controller.cluster.raft.RaftState;
  68 import org.opendaylight.controller.cluster.raft.VotingState;
  69 import org.opendaylight.mdsal.eos.dom.api.DOMEntity;
  70 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  71 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
  72 import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
  73 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  74 import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
  75 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  76 import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
  77 import scala.concurrent.Future;
  78 import scala.concurrent.duration.FiniteDuration;
  79
  80 /**
  81  * Special Shard for EntityOwnership.
  82  *
  83  * @author Thomas Pantelis
  84  */
  85 class EntityOwnershipShard extends Shard {
  86     private final MemberName localMemberName;
  87     private final EntityOwnershipShardCommitCoordinator commitCoordinator;
  88     private final EntityOwnershipListenerSupport listenerSupport;
  89     private final Set<MemberName> downPeerMemberNames = new HashSet<>();
  90     private final EntityOwnerSelectionStrategyConfig strategyConfig;
  91     private final Map<YangInstanceIdentifier, Cancellable> entityToScheduledOwnershipTask = new HashMap<>();
  92     private final EntityOwnershipStatistics entityOwnershipStatistics;
  93     private boolean removeAllInitialCandidates = true;
  94
  95     protected EntityOwnershipShard(final Builder builder) {
  96         super(builder);
  97         this.localMemberName = builder.localMemberName;
  98         this.commitCoordinator = new EntityOwnershipShardCommitCoordinator(builder.localMemberName, LOG);
  99         this.listenerSupport = new EntityOwnershipListenerSupport(getContext(), persistenceId());
 100         this.strategyConfig = builder.ownerSelectionStrategyConfig;
 101         this.entityOwnershipStatistics = new EntityOwnershipStatistics();
 102         this.entityOwnershipStatistics.init(getDataStore());
 103     }
 104
 105     private static DatastoreContext noPersistenceDatastoreContext(final DatastoreContext datastoreContext) {
 106         return DatastoreContext.newBuilderFrom(datastoreContext).persistent(false).build();
 107     }
 108
 109     @Override
 110     protected void onDatastoreContext(final DatastoreContext context) {
 111         super.onDatastoreContext(noPersistenceDatastoreContext(context));
 112     }
 113
 114     @Override
 115     protected void onRecoveryComplete() {
 116         super.onRecoveryComplete();
 117
 118         new CandidateListChangeListener(getSelf(), persistenceId()).init(getDataStore());
 119         new EntityOwnerChangeListener(localMemberName, listenerSupport).init(getDataStore());
 120     }
 121
 122     @Override
 123     public void handleNonRaftCommand(final Object message) {
 124         if (message instanceof RegisterCandidateLocal) {
 125             onRegisterCandidateLocal((RegisterCandidateLocal) message);
 126         } else if (message instanceof UnregisterCandidateLocal) {
 127             onUnregisterCandidateLocal((UnregisterCandidateLocal) message);
 128         } else if (message instanceof CandidateAdded) {
 129             onCandidateAdded((CandidateAdded) message);
 130         } else if (message instanceof CandidateRemoved) {
 131             onCandidateRemoved((CandidateRemoved) message);
 132         } else if (message instanceof PeerDown) {
 133             onPeerDown((PeerDown) message);
 134         } else if (message instanceof PeerUp) {
 135             onPeerUp((PeerUp) message);
 136         } else if (message instanceof RegisterListenerLocal) {
 137             onRegisterListenerLocal((RegisterListenerLocal) message);
 138         } else if (message instanceof UnregisterListenerLocal) {
 139             onUnregisterListenerLocal((UnregisterListenerLocal) message);
 140         } else if (message instanceof SelectOwner) {
 141             onSelectOwner((SelectOwner) message);
 142         } else if (message instanceof RemoveAllCandidates) {
 143             onRemoveAllCandidates((RemoveAllCandidates) message);
 144         } else if (!commitCoordinator.handleMessage(message, this)) {
 145             super.handleNonRaftCommand(message);
 146         }
 147     }
 148
 149     private void onRemoveAllCandidates(final RemoveAllCandidates message) {
 150         LOG.debug("{}: onRemoveAllCandidates: {}", persistenceId(), message);
 151
 152         removeCandidateFromEntities(message.getMemberName());
 153     }
 154
 155     private void onSelectOwner(final SelectOwner selectOwner) {
 156         LOG.debug("{}: onSelectOwner: {}", persistenceId(), selectOwner);
 157
 158         String currentOwner = getCurrentOwner(selectOwner.getEntityPath());
 159         if (Strings.isNullOrEmpty(currentOwner)) {
 160             writeNewOwner(selectOwner.getEntityPath(), newOwner(currentOwner, selectOwner.getAllCandidates(),
 161                     selectOwner.getOwnerSelectionStrategy()));
 162
 163             Cancellable cancellable = entityToScheduledOwnershipTask.get(selectOwner.getEntityPath());
 164             if (cancellable != null) {
 165                 if (!cancellable.isCancelled()) {
 166                     cancellable.cancel();
 167                 }
 168                 entityToScheduledOwnershipTask.remove(selectOwner.getEntityPath());
 169             }
 170         }
 171     }
 172
 173     private void onRegisterCandidateLocal(final RegisterCandidateLocal registerCandidate) {
 174         LOG.debug("{}: onRegisterCandidateLocal: {}", persistenceId(), registerCandidate);
 175
 176         NormalizedNode<?, ?> entityOwners = entityOwnersWithCandidate(registerCandidate.getEntity().getType(),
 177                 registerCandidate.getEntity().getIdentifier(), localMemberName.getName());
 178         commitCoordinator.commitModification(new MergeModification(ENTITY_OWNERS_PATH, entityOwners), this);
 179
 180         getSender().tell(SuccessReply.INSTANCE, getSelf());
 181     }
 182
 183     private void onUnregisterCandidateLocal(final UnregisterCandidateLocal unregisterCandidate) {
 184         LOG.debug("{}: onUnregisterCandidateLocal: {}", persistenceId(), unregisterCandidate);
 185
 186         DOMEntity entity = unregisterCandidate.getEntity();
 187         YangInstanceIdentifier candidatePath = candidatePath(entity.getType(), entity.getIdentifier(),
 188                 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             java.util.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                 java.util.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(final UnregisterListenerLocal unregisterListener) {
 227         LOG.debug("{}: onUnregisterListenerLocal: {}", persistenceId(), unregisterListener);
 228
 229         listenerSupport.removeEntityOwnershipListener(unregisterListener.getEntityType(),
 230                 unregisterListener.getListener());
 231
 232         getSender().tell(SuccessReply.INSTANCE, getSelf());
 233     }
 234
 235     void tryCommitModifications(final BatchedModifications modifications) {
 236         if (isLeader()) {
 237             LOG.debug("{}: Committing BatchedModifications {} locally", persistenceId(),
 238                     modifications.getTransactionId());
 239
 240             // Note that it's possible the commit won't get consensus and will timeout and not be applied
 241             // to the state. However we don't need to retry it in that case b/c it will be committed to
 242             // the journal first and, once a majority of followers come back on line and it is replicated,
 243             // it will be applied at that point.
 244             handleBatchedModificationsLocal(modifications, self());
 245         } else {
 246             final ActorSelection leader = getLeader();
 247             if (leader != null) {
 248                 possiblyRemoveAllInitialCandidates(leader);
 249
 250                 LOG.debug("{}: Sending BatchedModifications {} to leader {}", persistenceId(),
 251                         modifications.getTransactionId(), leader);
 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(final 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             default:
 296                 throw new IllegalStateException("Unsupported RAFT state " + state);
 297         }
 298     }
 299
 300     private void notifyAllListeners() {
 301         searchForEntities((entityTypeNode, entityNode) -> {
 302             java.util.Optional<DataContainerChild<?, ?>> possibleType = entityTypeNode.getChild(ENTITY_TYPE_NODE_ID);
 303             if (possibleType.isPresent()) {
 304                 final boolean hasOwner;
 305                 final boolean isOwner;
 306
 307                 java.util.Optional<DataContainerChild<?, ?>> possibleOwner = entityNode.getChild(ENTITY_OWNER_NODE_ID);
 308                 if (possibleOwner.isPresent()) {
 309                     isOwner = localMemberName.getName().equals(possibleOwner.get().getValue().toString());
 310                     hasOwner = true;
 311                 } else {
 312                     isOwner = false;
 313                     hasOwner = false;
 314                 }
 315
 316                 DOMEntity entity = new DOMEntity(possibleType.get().getValue().toString(),
 317                     (YangInstanceIdentifier) entityNode.getChild(ENTITY_ID_NODE_ID).get().getValue());
 318
 319                 listenerSupport.notifyEntityOwnershipListeners(entity, isOwner, isOwner, hasOwner);
 320             }
 321         });
 322     }
 323
 324     @Override
 325     protected void onStateChanged() {
 326         boolean isLeader = isLeader();
 327         LOG.debug("{}: onStateChanged: isLeader: {}, hasLeader: {}", persistenceId(), isLeader, hasLeader());
 328
 329         // Examine current RAFT state to see if we are in jeopardy, potentially notifying all listeners
 330         final boolean inJeopardy = inJeopardy(getRaftState());
 331         final boolean wasInJeopardy = listenerSupport.setInJeopardy(inJeopardy);
 332         if (inJeopardy != wasInJeopardy) {
 333             LOG.debug("{}: {} jeopardy state, notifying all listeners", persistenceId(),
 334                 inJeopardy ? "entered" : "left");
 335             notifyAllListeners();
 336         }
 337
 338         commitCoordinator.onStateChanged(this, isLeader);
 339
 340         super.onStateChanged();
 341     }
 342
 343     @Override
 344     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 345         boolean isLeader = isLeader();
 346         LOG.debug("{}: onLeaderChanged: oldLeader: {}, newLeader: {}, isLeader: {}", persistenceId(), oldLeader,
 347                 newLeader, isLeader);
 348
 349         if (isLeader) {
 350
 351             // Re-initialize the downPeerMemberNames from the current akka Cluster state. The previous leader, if any,
 352             // is most likely down however it's possible we haven't received the PeerDown message yet.
 353             initializeDownPeerMemberNamesFromClusterState();
 354
 355             // Clear all existing strategies so that they get re-created when we call createStrategy again
 356             // This allows the strategies to be re-initialized with existing statistics maintained by
 357             // EntityOwnershipStatistics
 358             strategyConfig.clearStrategies();
 359
 360             // Re-assign owners for all members that are known to be down. In a cluster which has greater than
 361             // 3 nodes it is possible for some node beside the leader being down when the leadership transitions
 362             // it makes sense to use this event to re-assign owners for those downed nodes.
 363             Set<String> ownedBy = new HashSet<>(downPeerMemberNames.size() + 1);
 364             for (MemberName downPeerName : downPeerMemberNames) {
 365                 ownedBy.add(downPeerName.getName());
 366             }
 367
 368             // Also try to assign owners for entities that have no current owner. See explanation in onPeerUp.
 369             ownedBy.add("");
 370             selectNewOwnerForEntitiesOwnedBy(ownedBy);
 371         } else {
 372             // The leader changed - notify the coordinator to check if pending modifications need to be sent.
 373             // While onStateChanged also does this, this method handles the case where the shard hears from a
 374             // leader and stays in the follower state. In that case no behavior state change occurs.
 375             commitCoordinator.onStateChanged(this, isLeader);
 376         }
 377
 378         super.onLeaderChanged(oldLeader, newLeader);
 379     }
 380
 381     @Override
 382     protected void onVotingStateChangeComplete() {
 383         // Re-evaluate ownership for all entities - if a member changed from voting to non-voting it should lose
 384         // ownership and vice versa it now is a candidate to become owner.
 385         final List<Modification> modifications = new ArrayList<>();
 386         searchForEntities((entityTypeNode, entityNode) -> {
 387             YangInstanceIdentifier entityPath = YangInstanceIdentifier.builder(ENTITY_TYPES_PATH)
 388                     .node(entityTypeNode.getIdentifier()).node(ENTITY_NODE_ID).node(entityNode.getIdentifier())
 389                     .node(ENTITY_OWNER_NODE_ID).build();
 390
 391             java.util.Optional<String> possibleOwner =
 392                     entityNode.getChild(ENTITY_OWNER_NODE_ID).map(node -> node.getValue().toString());
 393             String newOwner = newOwner(possibleOwner.orElse(null), getCandidateNames(entityNode),
 394                     getEntityOwnerElectionStrategy(entityPath));
 395
 396             if (!newOwner.equals(possibleOwner.orElse(""))) {
 397                 modifications.add(new WriteModification(entityPath,
 398                         ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)));
 399             }
 400         });
 401
 402         commitCoordinator.commitModifications(modifications, this);
 403     }
 404
 405     private void initializeDownPeerMemberNamesFromClusterState() {
 406         java.util.Optional<Cluster> cluster = getRaftActorContext().getCluster();
 407         if (!cluster.isPresent()) {
 408             return;
 409         }
 410
 411         CurrentClusterState state = cluster.get().state();
 412         Set<Member> unreachable = state.getUnreachable();
 413
 414         LOG.debug(
 415             "{}: initializeDownPeerMemberNamesFromClusterState - current downPeerMemberNames: {}, unreachable: {}",
 416             persistenceId(), downPeerMemberNames, unreachable);
 417
 418         downPeerMemberNames.clear();
 419         for (Member m: unreachable) {
 420             downPeerMemberNames.add(MemberName.forName(m.getRoles().iterator().next()));
 421         }
 422
 423         for (Member m: state.getMembers()) {
 424             if (m.status() != MemberStatus.up() && m.status() != MemberStatus.weaklyUp()) {
 425                 LOG.debug("{}: Adding down member with status {}", persistenceId(), m.status());
 426                 downPeerMemberNames.add(MemberName.forName(m.getRoles().iterator().next()));
 427             }
 428         }
 429
 430         LOG.debug("{}: new downPeerMemberNames: {}", persistenceId(), downPeerMemberNames);
 431     }
 432
 433     private void onCandidateRemoved(final CandidateRemoved message) {
 434         LOG.debug("{}: onCandidateRemoved: {}", persistenceId(), message);
 435
 436         if (isLeader()) {
 437             String currentOwner = getCurrentOwner(message.getEntityPath());
 438             writeNewOwner(message.getEntityPath(),
 439                     newOwner(currentOwner, message.getRemainingCandidates(),
 440                             getEntityOwnerElectionStrategy(message.getEntityPath())));
 441         }
 442     }
 443
 444     private EntityOwnerSelectionStrategy getEntityOwnerElectionStrategy(final YangInstanceIdentifier entityPath) {
 445         final String entityType = EntityOwnersModel.entityTypeFromEntityPath(entityPath);
 446         return strategyConfig.createStrategy(entityType, entityOwnershipStatistics.byEntityType(entityType));
 447     }
 448
 449     private void onCandidateAdded(final CandidateAdded message) {
 450         if (!isLeader()) {
 451             return;
 452         }
 453
 454         LOG.debug("{}: onCandidateAdded: {}", persistenceId(), message);
 455
 456         // Since a node's candidate member is only added by the node itself, we can assume the node is up so
 457         // remove it from the downPeerMemberNames.
 458         downPeerMemberNames.remove(MemberName.forName(message.getNewCandidate()));
 459
 460         final String currentOwner = getCurrentOwner(message.getEntityPath());
 461         final EntityOwnerSelectionStrategy strategy = getEntityOwnerElectionStrategy(message.getEntityPath());
 462
 463         // Available members is all the known peers - the number of peers that are down + self
 464         // So if there are 2 peers and 1 is down then availableMembers will be 2
 465         final int availableMembers = getRaftActorContext().getPeerIds().size() - downPeerMemberNames.size() + 1;
 466
 467         LOG.debug("{}: Using strategy {} to select owner, currentOwner = {}", persistenceId(), strategy, currentOwner);
 468
 469         if (strategy.getSelectionDelayInMillis() == 0L) {
 470             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 471                     strategy));
 472         } else if (message.getAllCandidates().size() == availableMembers) {
 473             LOG.debug("{}: Received the maximum candidates requests : {} writing new owner",
 474                     persistenceId(), availableMembers);
 475             cancelOwnerSelectionTask(message.getEntityPath());
 476             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 477                     strategy));
 478         } else {
 479             scheduleOwnerSelection(message.getEntityPath(), message.getAllCandidates(), strategy);
 480         }
 481     }
 482
 483     private void onPeerDown(final PeerDown peerDown) {
 484         LOG.info("{}: onPeerDown: {}", persistenceId(), peerDown);
 485
 486         MemberName downMemberName = peerDown.getMemberName();
 487         if (downPeerMemberNames.add(downMemberName) && isLeader()) {
 488             // Select new owners for entities owned by the down peer and which have other candidates. For an entity for
 489             // which the down peer is the only candidate, we leave it as the owner and don't clear it. This is done to
 490             // handle the case where the peer member process is actually still running but the node is partitioned.
 491             // When the partition is healed, the peer just remains as the owner. If the peer process actually restarted,
 492             // it will first remove all its candidates on startup. If another candidate is registered during the time
 493             // the peer is down, the new candidate will be selected as the new owner.
 494
 495             selectNewOwnerForEntitiesOwnedBy(ImmutableSet.of(downMemberName.getName()));
 496         }
 497     }
 498
 499     private void selectNewOwnerForEntitiesOwnedBy(final Set<String> ownedBy) {
 500         final List<Modification> modifications = new ArrayList<>();
 501         searchForEntitiesOwnedBy(ownedBy, (entityTypeNode, entityNode) -> {
 502             YangInstanceIdentifier entityPath = YangInstanceIdentifier.builder(ENTITY_TYPES_PATH)
 503                     .node(entityTypeNode.getIdentifier()).node(ENTITY_NODE_ID).node(entityNode.getIdentifier())
 504                     .node(ENTITY_OWNER_NODE_ID).build();
 505             String newOwner = newOwner(getCurrentOwner(entityPath), getCandidateNames(entityNode),
 506                     getEntityOwnerElectionStrategy(entityPath));
 507
 508             if (!newOwner.isEmpty()) {
 509                 LOG.debug("{}: Found entity {}, writing new owner {}", persistenceId(), entityPath, newOwner);
 510
 511                 modifications.add(new WriteModification(entityPath,
 512                     ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)));
 513
 514             } else {
 515                 LOG.debug("{}: Found entity {} but no other candidates - not clearing owner", persistenceId(),
 516                         entityPath);
 517             }
 518         });
 519
 520         commitCoordinator.commitModifications(modifications, this);
 521     }
 522
 523     private void onPeerUp(final PeerUp peerUp) {
 524         LOG.debug("{}: onPeerUp: {}", persistenceId(), peerUp);
 525
 526         downPeerMemberNames.remove(peerUp.getMemberName());
 527
 528         // Notify the coordinator to check if pending modifications need to be sent. We do this here
 529         // to handle the case where the leader's peer address isn't known yet when a prior state or
 530         // leader change occurred.
 531         commitCoordinator.onStateChanged(this, isLeader());
 532
 533         if (isLeader()) {
 534             // Try to assign owners for entities that have no current owner. It's possible the peer that is now up
 535             // had previously registered as a candidate and was the only candidate but the owner write tx couldn't be
 536             // committed due to a leader change. Eg, the leader is able to successfully commit the candidate add tx but
 537             // becomes isolated before it can commit the owner change and switches to follower. The majority partition
 538             // with a new leader has the candidate but the entity has no owner. When the partition is healed and the
 539             // previously isolated leader reconnects, we'll receive onPeerUp and, if there's still no owner, the
 540             // previous leader will gain ownership.
 541             selectNewOwnerForEntitiesOwnedBy(ImmutableSet.of(""));
 542         }
 543     }
 544
 545     private static Collection<String> getCandidateNames(final MapEntryNode entity) {
 546         Collection<MapEntryNode> candidates = ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getValue();
 547         Collection<String> candidateNames = new ArrayList<>(candidates.size());
 548         for (MapEntryNode candidate: candidates) {
 549             candidateNames.add(candidate.getChild(CANDIDATE_NAME_NODE_ID).get().getValue().toString());
 550         }
 551
 552         return candidateNames;
 553     }
 554
 555     private void searchForEntitiesOwnedBy(final Set<String> ownedBy, final EntityWalker walker) {
 556         LOG.debug("{}: Searching for entities owned by {}", persistenceId(), ownedBy);
 557
 558         searchForEntities((entityTypeNode, entityNode) -> {
 559             java.util.Optional<DataContainerChild<? extends PathArgument, ?>> possibleOwner =
 560                     entityNode.getChild(ENTITY_OWNER_NODE_ID);
 561             String currentOwner = possibleOwner.isPresent() ? possibleOwner.get().getValue().toString() : "";
 562             if (ownedBy.contains(currentOwner)) {
 563                 walker.onEntity(entityTypeNode, entityNode);
 564             }
 565         });
 566     }
 567
 568     private void removeCandidateFromEntities(final MemberName member) {
 569         final List<Modification> modifications = new ArrayList<>();
 570         searchForEntities((entityTypeNode, entityNode) -> {
 571             if (hasCandidate(entityNode, member)) {
 572                 YangInstanceIdentifier entityId =
 573                         (YangInstanceIdentifier) entityNode.getIdentifier().getKeyValues().get(ENTITY_ID_QNAME);
 574                 YangInstanceIdentifier candidatePath = candidatePath(
 575                         entityTypeNode.getIdentifier().getKeyValues().get(ENTITY_TYPE_QNAME).toString(),
 576                         entityId, member.getName());
 577
 578                 LOG.info("{}: Found entity {}, removing candidate {}, path {}", persistenceId(), entityId,
 579                         member, candidatePath);
 580
 581                 modifications.add(new DeleteModification(candidatePath));
 582             }
 583         });
 584
 585         commitCoordinator.commitModifications(modifications, this);
 586     }
 587
 588     private static boolean hasCandidate(final MapEntryNode entity, final MemberName candidateName) {
 589         return ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getChild(candidateNodeKey(candidateName.getName()))
 590                 .isPresent();
 591     }
 592
 593     private void searchForEntities(final EntityWalker walker) {
 594         Optional<NormalizedNode<?, ?>> possibleEntityTypes = getDataStore().readNode(ENTITY_TYPES_PATH);
 595         if (!possibleEntityTypes.isPresent()) {
 596             return;
 597         }
 598
 599         for (MapEntryNode entityType:  ((MapNode) possibleEntityTypes.get()).getValue()) {
 600             java.util.Optional<DataContainerChild<?, ?>> possibleEntities = entityType.getChild(ENTITY_NODE_ID);
 601             if (!possibleEntities.isPresent()) {
 602                 // shouldn't happen but handle anyway
 603                 continue;
 604             }
 605
 606             for (MapEntryNode entity:  ((MapNode) possibleEntities.get()).getValue()) {
 607                 walker.onEntity(entityType, entity);
 608             }
 609         }
 610     }
 611
 612     private void writeNewOwner(final YangInstanceIdentifier entityPath, final String newOwner) {
 613         LOG.debug("{}: Writing new owner {} for entity {}", persistenceId(), newOwner, entityPath);
 614
 615         commitCoordinator.commitModification(new WriteModification(entityPath.node(ENTITY_OWNER_QNAME),
 616                 ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)), this);
 617     }
 618
 619     /**
 620      * Schedule a new owner selection job. Cancelling any outstanding job if it has not been cancelled.
 621      */
 622     private void scheduleOwnerSelection(final YangInstanceIdentifier entityPath, final Collection<String> allCandidates,
 623                                        final EntityOwnerSelectionStrategy strategy) {
 624         cancelOwnerSelectionTask(entityPath);
 625
 626         LOG.debug("{}: Scheduling owner selection after {} ms", persistenceId(), strategy.getSelectionDelayInMillis());
 627
 628         final Cancellable lastScheduledTask = context().system().scheduler().scheduleOnce(
 629                 FiniteDuration.apply(strategy.getSelectionDelayInMillis(), TimeUnit.MILLISECONDS), self(),
 630                 new SelectOwner(entityPath, allCandidates, strategy), context().system().dispatcher(), self());
 631
 632         entityToScheduledOwnershipTask.put(entityPath, lastScheduledTask);
 633     }
 634
 635     private void cancelOwnerSelectionTask(final YangInstanceIdentifier entityPath) {
 636         final Cancellable lastScheduledTask = entityToScheduledOwnershipTask.get(entityPath);
 637         if (lastScheduledTask != null && !lastScheduledTask.isCancelled()) {
 638             lastScheduledTask.cancel();
 639         }
 640     }
 641
 642     private String newOwner(final String currentOwner, final Collection<String> candidates,
 643             final EntityOwnerSelectionStrategy ownerSelectionStrategy) {
 644         Collection<String> viableCandidates = getViableCandidates(candidates);
 645         if (viableCandidates.isEmpty()) {
 646             return "";
 647         }
 648         return ownerSelectionStrategy.newOwner(currentOwner, viableCandidates);
 649     }
 650
 651     private Collection<String> getViableCandidates(final Collection<String> candidates) {
 652         Map<MemberName, VotingState> memberToVotingState = new HashMap<>();
 653         getRaftActorContext().getPeers().forEach(peerInfo -> memberToVotingState.put(
 654                 ShardIdentifier.fromShardIdString(peerInfo.getId()).getMemberName(), peerInfo.getVotingState()));
 655
 656         Collection<String> viableCandidates = new ArrayList<>();
 657
 658         for (String candidate : candidates) {
 659             MemberName memberName = MemberName.forName(candidate);
 660             if (memberToVotingState.get(memberName) != VotingState.NON_VOTING
 661                     && !downPeerMemberNames.contains(memberName)) {
 662                 viableCandidates.add(candidate);
 663             }
 664         }
 665         return viableCandidates;
 666     }
 667
 668     private String getCurrentOwner(final YangInstanceIdentifier entityId) {
 669         Optional<NormalizedNode<?, ?>> optionalEntityOwner = getDataStore().readNode(entityId.node(ENTITY_OWNER_QNAME));
 670         if (optionalEntityOwner.isPresent()) {
 671             return optionalEntityOwner.get().getValue().toString();
 672         }
 673         return null;
 674     }
 675
 676     @FunctionalInterface
 677     private interface EntityWalker {
 678         void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode);
 679     }
 680
 681     public static Builder newBuilder() {
 682         return new Builder();
 683     }
 684
 685     static class Builder extends Shard.AbstractBuilder<Builder, EntityOwnershipShard> {
 686         private MemberName localMemberName;
 687         private EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig;
 688
 689         protected Builder() {
 690             super(EntityOwnershipShard.class);
 691         }
 692
 693         Builder localMemberName(final MemberName newLocalMemberName) {
 694             checkSealed();
 695             this.localMemberName = newLocalMemberName;
 696             return this;
 697         }
 698
 699         Builder ownerSelectionStrategyConfig(final EntityOwnerSelectionStrategyConfig newOwnerSelectionStrategyConfig) {
 700             checkSealed();
 701             this.ownerSelectionStrategyConfig = newOwnerSelectionStrategyConfig;
 702             return this;
 703         }
 704
 705         @Override
 706         protected void verify() {
 707             super.verify();
 708             Preconditions.checkNotNull(localMemberName, "localMemberName should not be null");
 709             Preconditions.checkNotNull(ownerSelectionStrategyConfig, "ownerSelectionStrategyConfig should not be null");
 710         }
 711     }
 712 }