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.Map;
  42 import java.util.Set;
  43 import java.util.concurrent.TimeUnit;
  44 import org.opendaylight.controller.cluster.access.concepts.MemberName;
  45 import org.opendaylight.controller.cluster.datastore.DatastoreContext;
  46 import org.opendaylight.controller.cluster.datastore.Shard;
  47 import org.opendaylight.controller.cluster.datastore.entityownership.messages.CandidateAdded;
  48 import org.opendaylight.controller.cluster.datastore.entityownership.messages.CandidateRemoved;
  49 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RegisterCandidateLocal;
  50 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RegisterListenerLocal;
  51 import org.opendaylight.controller.cluster.datastore.entityownership.messages.RemoveAllCandidates;
  52 import org.opendaylight.controller.cluster.datastore.entityownership.messages.SelectOwner;
  53 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterCandidateLocal;
  54 import org.opendaylight.controller.cluster.datastore.entityownership.messages.UnregisterListenerLocal;
  55 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategy;
  56 import org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy.EntityOwnerSelectionStrategyConfig;
  57 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  58 import org.opendaylight.controller.cluster.datastore.messages.PeerDown;
  59 import org.opendaylight.controller.cluster.datastore.messages.PeerUp;
  60 import org.opendaylight.controller.cluster.datastore.messages.SuccessReply;
  61 import org.opendaylight.controller.cluster.datastore.modification.DeleteModification;
  62 import org.opendaylight.controller.cluster.datastore.modification.MergeModification;
  63 import org.opendaylight.controller.cluster.datastore.modification.WriteModification;
  64 import org.opendaylight.controller.cluster.raft.RaftState;
  65 import org.opendaylight.mdsal.eos.dom.api.DOMEntity;
  66 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  67 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
  68 import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
  69 import org.opendaylight.yangtools.yang.data.api.schema.MapEntryNode;
  70 import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
  71 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  72 import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
  73 import scala.concurrent.Future;
  74 import scala.concurrent.duration.FiniteDuration;
  75
  76 /**
  77  * Special Shard for EntityOwnership.
  78  *
  79  * @author Thomas Pantelis
  80  */
  81 class EntityOwnershipShard extends Shard {
  82     private final MemberName localMemberName;
  83     private final EntityOwnershipShardCommitCoordinator commitCoordinator;
  84     private final EntityOwnershipListenerSupport listenerSupport;
  85     private final Set<MemberName> downPeerMemberNames = new HashSet<>();
  86     private final EntityOwnerSelectionStrategyConfig strategyConfig;
  87     private final Map<YangInstanceIdentifier, Cancellable> entityToScheduledOwnershipTask = new HashMap<>();
  88     private final EntityOwnershipStatistics entityOwnershipStatistics;
  89     private boolean removeAllInitialCandidates = true;
  90
  91     protected EntityOwnershipShard(final 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
 101     private static DatastoreContext noPersistenceDatastoreContext(final DatastoreContext datastoreContext) {
 102         return DatastoreContext.newBuilderFrom(datastoreContext).persistent(false).build();
 103     }
 104
 105     @Override
 106     protected void onDatastoreContext(final DatastoreContext context) {
 107         super.onDatastoreContext(noPersistenceDatastoreContext(context));
 108     }
 109
 110     @Override
 111     protected void onRecoveryComplete() {
 112         super.onRecoveryComplete();
 113
 114         new CandidateListChangeListener(getSelf(), persistenceId()).init(getDataStore());
 115         new EntityOwnerChangeListener(localMemberName, listenerSupport).init(getDataStore());
 116     }
 117
 118     @Override
 119     public void handleNonRaftCommand(final Object message) {
 120         if (message instanceof RegisterCandidateLocal) {
 121             onRegisterCandidateLocal((RegisterCandidateLocal) message);
 122         } else if (message instanceof UnregisterCandidateLocal) {
 123             onUnregisterCandidateLocal((UnregisterCandidateLocal) message);
 124         } else if (message instanceof CandidateAdded) {
 125             onCandidateAdded((CandidateAdded) message);
 126         } else if (message instanceof CandidateRemoved) {
 127             onCandidateRemoved((CandidateRemoved) message);
 128         } else if (message instanceof PeerDown) {
 129             onPeerDown((PeerDown) message);
 130         } else if (message instanceof PeerUp) {
 131             onPeerUp((PeerUp) message);
 132         } else if (message instanceof RegisterListenerLocal) {
 133             onRegisterListenerLocal((RegisterListenerLocal) message);
 134         } else if (message instanceof UnregisterListenerLocal) {
 135             onUnregisterListenerLocal((UnregisterListenerLocal) message);
 136         } else if (message instanceof SelectOwner) {
 137             onSelectOwner((SelectOwner) message);
 138         } else if (message instanceof RemoveAllCandidates) {
 139             onRemoveAllCandidates((RemoveAllCandidates) message);
 140         } else if (!commitCoordinator.handleMessage(message, this)) {
 141             super.handleNonRaftCommand(message);
 142         }
 143     }
 144
 145     private void onRemoveAllCandidates(final RemoveAllCandidates message) {
 146         LOG.debug("{}: onRemoveAllCandidates: {}", persistenceId(), message);
 147
 148         removeCandidateFromEntities(message.getMemberName());
 149     }
 150
 151     private void onSelectOwner(final SelectOwner selectOwner) {
 152         LOG.debug("{}: onSelectOwner: {}", persistenceId(), selectOwner);
 153
 154         String currentOwner = getCurrentOwner(selectOwner.getEntityPath());
 155         if (Strings.isNullOrEmpty(currentOwner)) {
 156             writeNewOwner(selectOwner.getEntityPath(), newOwner(currentOwner, selectOwner.getAllCandidates(),
 157                     selectOwner.getOwnerSelectionStrategy()));
 158
 159             Cancellable cancellable = entityToScheduledOwnershipTask.get(selectOwner.getEntityPath());
 160             if (cancellable != null) {
 161                 if (!cancellable.isCancelled()) {
 162                     cancellable.cancel();
 163                 }
 164                 entityToScheduledOwnershipTask.remove(selectOwner.getEntityPath());
 165             }
 166         }
 167     }
 168
 169     private void onRegisterCandidateLocal(final RegisterCandidateLocal registerCandidate) {
 170         LOG.debug("{}: onRegisterCandidateLocal: {}", persistenceId(), registerCandidate);
 171
 172         NormalizedNode<?, ?> entityOwners = entityOwnersWithCandidate(registerCandidate.getEntity().getType(),
 173                 registerCandidate.getEntity().getIdentifier(), localMemberName.getName());
 174         commitCoordinator.commitModification(new MergeModification(ENTITY_OWNERS_PATH, entityOwners), this);
 175
 176         getSender().tell(SuccessReply.INSTANCE, getSelf());
 177     }
 178
 179     private void onUnregisterCandidateLocal(final UnregisterCandidateLocal unregisterCandidate) {
 180         LOG.debug("{}: onUnregisterCandidateLocal: {}", persistenceId(), unregisterCandidate);
 181
 182         DOMEntity entity = unregisterCandidate.getEntity();
 183         YangInstanceIdentifier candidatePath = candidatePath(entity.getType(), entity.getIdentifier(),
 184                 localMemberName.getName());
 185         commitCoordinator.commitModification(new DeleteModification(candidatePath), this);
 186
 187         getSender().tell(SuccessReply.INSTANCE, getSelf());
 188     }
 189
 190     private void onRegisterListenerLocal(final RegisterListenerLocal registerListener) {
 191         LOG.debug("{}: onRegisterListenerLocal: {}", persistenceId(), registerListener);
 192
 193         listenerSupport.addEntityOwnershipListener(registerListener.getEntityType(), registerListener.getListener());
 194
 195         getSender().tell(SuccessReply.INSTANCE, getSelf());
 196
 197         searchForEntities((entityTypeNode, entityNode) -> {
 198             Optional<DataContainerChild<?, ?>> possibleType = entityTypeNode.getChild(ENTITY_TYPE_NODE_ID);
 199             String entityType = possibleType.isPresent() ? possibleType.get().getValue().toString() : null;
 200             if (registerListener.getEntityType().equals(entityType)) {
 201                 final boolean hasOwner;
 202                 final boolean isOwner;
 203
 204                 Optional<DataContainerChild<?, ?>> possibleOwner = entityNode.getChild(ENTITY_OWNER_NODE_ID);
 205                 if (possibleOwner.isPresent()) {
 206                     isOwner = localMemberName.getName().equals(possibleOwner.get().getValue().toString());
 207                     hasOwner = true;
 208                 } else {
 209                     isOwner = false;
 210                     hasOwner = false;
 211                 }
 212
 213                 DOMEntity entity = new DOMEntity(entityType,
 214                     (YangInstanceIdentifier) entityNode.getChild(ENTITY_ID_NODE_ID).get().getValue());
 215
 216                 listenerSupport.notifyEntityOwnershipListener(entity, false, isOwner, hasOwner,
 217                     registerListener.getListener());
 218             }
 219         });
 220     }
 221
 222     private void onUnregisterListenerLocal(final UnregisterListenerLocal unregisterListener) {
 223         LOG.debug("{}: onUnregisterListenerLocal: {}", persistenceId(), unregisterListener);
 224
 225         listenerSupport.removeEntityOwnershipListener(unregisterListener.getEntityType(),
 226                 unregisterListener.getListener());
 227
 228         getSender().tell(SuccessReply.INSTANCE, getSelf());
 229     }
 230
 231     void tryCommitModifications(final BatchedModifications modifications) {
 232         if (isLeader()) {
 233             LOG.debug("{}: Committing BatchedModifications {} locally", persistenceId(),
 234                     modifications.getTransactionId());
 235
 236             // Note that it's possible the commit won't get consensus and will timeout and not be applied
 237             // to the state. However we don't need to retry it in that case b/c it will be committed to
 238             // the journal first and, once a majority of followers come back on line and it is replicated,
 239             // it will be applied at that point.
 240             handleBatchedModificationsLocal(modifications, self());
 241         } else {
 242             final ActorSelection leader = getLeader();
 243             if (leader != null) {
 244                 possiblyRemoveAllInitialCandidates(leader);
 245
 246                 LOG.debug("{}: Sending BatchedModifications {} to leader {}", persistenceId(),
 247                         modifications.getTransactionId(), leader);
 248
 249                 Future<Object> future = Patterns.ask(leader, modifications, TimeUnit.SECONDS.toMillis(
 250                         getDatastoreContext().getShardTransactionCommitTimeoutInSeconds()));
 251
 252                 Patterns.pipe(future, getContext().dispatcher()).pipeTo(getSelf(), ActorRef.noSender());
 253             }
 254         }
 255     }
 256
 257     void possiblyRemoveAllInitialCandidates(final ActorSelection leader) {
 258         // The following handles removing all candidates on startup when re-joining with a remote leader. When a
 259         // follower is detected as down, the leader will re-assign new owners to entities that were owned by the
 260         // down member but doesn't remove the down member as a candidate, as the down node may actually be isolated
 261         // and still running. Therefore on startup we send an initial message to the remote leader to remove any
 262         // potential stale candidates we had previously registered, as it's possible a candidate may not be
 263         // registered by a client in the new incarnation. We have to send the RemoveAllCandidates message prior to any
 264         // pending registrations.
 265         if (removeAllInitialCandidates && leader != null) {
 266             removeAllInitialCandidates = false;
 267             if (!isLeader()) {
 268                 LOG.debug("{} - got new leader {} on startup - sending RemoveAllCandidates", persistenceId(), leader);
 269
 270                 leader.tell(new RemoveAllCandidates(localMemberName), ActorRef.noSender());
 271             }
 272         }
 273     }
 274
 275     boolean hasLeader() {
 276         return getLeader() != null && (!isLeader() || isLeaderActive());
 277     }
 278
 279     /**
 280      * Determine if we are in jeopardy based on observed RAFT state.
 281      */
 282     private static boolean inJeopardy(final RaftState state) {
 283         switch (state) {
 284             case Candidate:
 285             case Follower:
 286             case Leader:
 287             case PreLeader:
 288                 return false;
 289             case IsolatedLeader:
 290                 return true;
 291             default:
 292                 throw new IllegalStateException("Unsupported RAFT state " + state);
 293         }
 294     }
 295
 296     private void notifyAllListeners() {
 297         searchForEntities((entityTypeNode, entityNode) -> {
 298             Optional<DataContainerChild<?, ?>> possibleType = entityTypeNode.getChild(ENTITY_TYPE_NODE_ID);
 299             if (possibleType.isPresent()) {
 300                 final boolean hasOwner;
 301                 final boolean isOwner;
 302
 303                 Optional<DataContainerChild<?, ?>> possibleOwner = entityNode.getChild(ENTITY_OWNER_NODE_ID);
 304                 if (possibleOwner.isPresent()) {
 305                     isOwner = localMemberName.getName().equals(possibleOwner.get().getValue().toString());
 306                     hasOwner = true;
 307                 } else {
 308                     isOwner = false;
 309                     hasOwner = false;
 310                 }
 311
 312                 DOMEntity entity = new DOMEntity(possibleType.get().getValue().toString(),
 313                     (YangInstanceIdentifier) entityNode.getChild(ENTITY_ID_NODE_ID).get().getValue());
 314
 315                 listenerSupport.notifyEntityOwnershipListeners(entity, isOwner, isOwner, hasOwner);
 316             }
 317         });
 318     }
 319
 320     @Override
 321     protected void onStateChanged() {
 322         boolean isLeader = isLeader();
 323         LOG.debug("{}: onStateChanged: isLeader: {}, hasLeader: {}", persistenceId(), isLeader, hasLeader());
 324
 325         // Examine current RAFT state to see if we are in jeopardy, potentially notifying all listeners
 326         final boolean inJeopardy = inJeopardy(getRaftState());
 327         final boolean wasInJeopardy = listenerSupport.setInJeopardy(inJeopardy);
 328         if (inJeopardy != wasInJeopardy) {
 329             LOG.debug("{}: {} jeopardy state, notifying all listeners", persistenceId(),
 330                 inJeopardy ? "entered" : "left");
 331             notifyAllListeners();
 332         }
 333
 334         commitCoordinator.onStateChanged(this, isLeader);
 335
 336         super.onStateChanged();
 337     }
 338
 339     @Override
 340     protected void onLeaderChanged(final String oldLeader, final String newLeader) {
 341         boolean isLeader = isLeader();
 342         LOG.debug("{}: onLeaderChanged: oldLeader: {}, newLeader: {}, isLeader: {}", persistenceId(), oldLeader,
 343                 newLeader, isLeader);
 344
 345         if (isLeader) {
 346
 347             // Re-initialize the downPeerMemberNames from the current akka Cluster state. The previous leader, if any,
 348             // is most likely down however it's possible we haven't received the PeerDown message yet.
 349             initializeDownPeerMemberNamesFromClusterState();
 350
 351             // Clear all existing strategies so that they get re-created when we call createStrategy again
 352             // This allows the strategies to be re-initialized with existing statistics maintained by
 353             // EntityOwnershipStatistics
 354             strategyConfig.clearStrategies();
 355
 356             // Re-assign owners for all members that are known to be down. In a cluster which has greater than
 357             // 3 nodes it is possible for some node beside the leader being down when the leadership transitions
 358             // it makes sense to use this event to re-assign owners for those downed nodes.
 359             Set<String> ownedBy = new HashSet<>(downPeerMemberNames.size() + 1);
 360             for (MemberName downPeerName : downPeerMemberNames) {
 361                 ownedBy.add(downPeerName.getName());
 362             }
 363
 364             // Also try to assign owners for entities that have no current owner. See explanation in onPeerUp.
 365             ownedBy.add("");
 366             selectNewOwnerForEntitiesOwnedBy(ownedBy);
 367         } else {
 368             // The leader changed - notify the coordinator to check if pending modifications need to be sent.
 369             // While onStateChanged also does this, this method handles the case where the shard hears from a
 370             // leader and stays in the follower state. In that case no behavior state change occurs.
 371             commitCoordinator.onStateChanged(this, isLeader);
 372         }
 373
 374         super.onLeaderChanged(oldLeader, newLeader);
 375     }
 376
 377     private void initializeDownPeerMemberNamesFromClusterState() {
 378         java.util.Optional<Cluster> cluster = getRaftActorContext().getCluster();
 379         if (!cluster.isPresent()) {
 380             return;
 381         }
 382
 383         CurrentClusterState state = cluster.get().state();
 384         Set<Member> unreachable = state.getUnreachable();
 385
 386         LOG.debug(
 387             "{}: initializeDownPeerMemberNamesFromClusterState - current downPeerMemberNames: {}, unreachable: {}",
 388             persistenceId(), downPeerMemberNames, unreachable);
 389
 390         downPeerMemberNames.clear();
 391         for (Member m: unreachable) {
 392             downPeerMemberNames.add(MemberName.forName(m.getRoles().iterator().next()));
 393         }
 394
 395         for (Member m: state.getMembers()) {
 396             if (m.status() != MemberStatus.up() && m.status() != MemberStatus.weaklyUp()) {
 397                 LOG.debug("{}: Adding down member with status {}", persistenceId(), m.status());
 398                 downPeerMemberNames.add(MemberName.forName(m.getRoles().iterator().next()));
 399             }
 400         }
 401
 402         LOG.debug("{}: new downPeerMemberNames: {}", persistenceId(), downPeerMemberNames);
 403     }
 404
 405     private void onCandidateRemoved(final CandidateRemoved message) {
 406         LOG.debug("{}: onCandidateRemoved: {}", persistenceId(), message);
 407
 408         if (isLeader()) {
 409             String currentOwner = getCurrentOwner(message.getEntityPath());
 410             writeNewOwner(message.getEntityPath(),
 411                     newOwner(currentOwner, message.getRemainingCandidates(),
 412                             getEntityOwnerElectionStrategy(message.getEntityPath())));
 413         }
 414     }
 415
 416     private EntityOwnerSelectionStrategy getEntityOwnerElectionStrategy(final YangInstanceIdentifier entityPath) {
 417         final String entityType = EntityOwnersModel.entityTypeFromEntityPath(entityPath);
 418         return strategyConfig.createStrategy(entityType, entityOwnershipStatistics.byEntityType(entityType));
 419     }
 420
 421     private void onCandidateAdded(final CandidateAdded message) {
 422         if (!isLeader()) {
 423             return;
 424         }
 425
 426         LOG.debug("{}: onCandidateAdded: {}", persistenceId(), message);
 427
 428         // Since a node's candidate member is only added by the node itself, we can assume the node is up so
 429         // remove it from the downPeerMemberNames.
 430         downPeerMemberNames.remove(MemberName.forName(message.getNewCandidate()));
 431
 432         final String currentOwner = getCurrentOwner(message.getEntityPath());
 433         final EntityOwnerSelectionStrategy strategy = getEntityOwnerElectionStrategy(message.getEntityPath());
 434
 435         // Available members is all the known peers - the number of peers that are down + self
 436         // So if there are 2 peers and 1 is down then availableMembers will be 2
 437         final int availableMembers = getRaftActorContext().getPeerIds().size() - downPeerMemberNames.size() + 1;
 438
 439         LOG.debug("{}: Using strategy {} to select owner, currentOwner = {}", persistenceId(), strategy, currentOwner);
 440
 441         if (strategy.getSelectionDelayInMillis() == 0L) {
 442             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 443                     strategy));
 444         } else if (message.getAllCandidates().size() == availableMembers) {
 445             LOG.debug("{}: Received the maximum candidates requests : {} writing new owner",
 446                     persistenceId(), availableMembers);
 447             cancelOwnerSelectionTask(message.getEntityPath());
 448             writeNewOwner(message.getEntityPath(), newOwner(currentOwner, message.getAllCandidates(),
 449                     strategy));
 450         } else {
 451             scheduleOwnerSelection(message.getEntityPath(), message.getAllCandidates(), strategy);
 452         }
 453     }
 454
 455     private void onPeerDown(final PeerDown peerDown) {
 456         LOG.info("{}: onPeerDown: {}", persistenceId(), peerDown);
 457
 458         MemberName downMemberName = peerDown.getMemberName();
 459         if (downPeerMemberNames.add(downMemberName) && isLeader()) {
 460             // Select new owners for entities owned by the down peer and which have other candidates. For an entity for
 461             // which the down peer is the only candidate, we leave it as the owner and don't clear it. This is done to
 462             // handle the case where the peer member process is actually still running but the node is partitioned.
 463             // When the partition is healed, the peer just remains as the owner. If the peer process actually restarted,
 464             // it will first remove all its candidates on startup. If another candidate is registered during the time
 465             // the peer is down, the new candidate will be selected as the new owner.
 466
 467             selectNewOwnerForEntitiesOwnedBy(ImmutableSet.of(downMemberName.getName()));
 468         }
 469     }
 470
 471     private void selectNewOwnerForEntitiesOwnedBy(final Set<String> ownedBy) {
 472         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 473         searchForEntitiesOwnedBy(ownedBy, (entityTypeNode, entityNode) -> {
 474             YangInstanceIdentifier entityPath = YangInstanceIdentifier.builder(ENTITY_TYPES_PATH)
 475                     .node(entityTypeNode.getIdentifier()).node(ENTITY_NODE_ID).node(entityNode.getIdentifier())
 476                     .node(ENTITY_OWNER_NODE_ID).build();
 477             String newOwner = newOwner(getCurrentOwner(entityPath), getCandidateNames(entityNode),
 478                     getEntityOwnerElectionStrategy(entityPath));
 479
 480             if (!newOwner.isEmpty()) {
 481                 LOG.debug("{}: Found entity {}, writing new owner {}", persistenceId(), entityPath, newOwner);
 482
 483                 modifications.addModification(new WriteModification(entityPath,
 484                         ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)));
 485
 486             } else {
 487                 LOG.debug("{}: Found entity {} but no other candidates - not clearing owner", persistenceId(),
 488                         entityPath, newOwner);
 489             }
 490         });
 491
 492         commitCoordinator.commitModifications(modifications, this);
 493     }
 494
 495     private void onPeerUp(final PeerUp peerUp) {
 496         LOG.debug("{}: onPeerUp: {}", persistenceId(), peerUp);
 497
 498         downPeerMemberNames.remove(peerUp.getMemberName());
 499
 500         // Notify the coordinator to check if pending modifications need to be sent. We do this here
 501         // to handle the case where the leader's peer address isn't known yet when a prior state or
 502         // leader change occurred.
 503         commitCoordinator.onStateChanged(this, isLeader());
 504
 505         if (isLeader()) {
 506             // Try to assign owners for entities that have no current owner. It's possible the peer that is now up
 507             // had previously registered as a candidate and was the only candidate but the owner write tx couldn't be
 508             // committed due to a leader change. Eg, the leader is able to successfully commit the candidate add tx but
 509             // becomes isolated before it can commit the owner change and switches to follower. The majority partition
 510             // with a new leader has the candidate but the entity has no owner. When the partition is healed and the
 511             // previously isolated leader reconnects, we'll receive onPeerUp and, if there's still no owner, the
 512             // previous leader will gain ownership.
 513             selectNewOwnerForEntitiesOwnedBy(ImmutableSet.of(""));
 514         }
 515     }
 516
 517     private static Collection<String> getCandidateNames(final MapEntryNode entity) {
 518         Collection<MapEntryNode> candidates = ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getValue();
 519         Collection<String> candidateNames = new ArrayList<>(candidates.size());
 520         for (MapEntryNode candidate: candidates) {
 521             candidateNames.add(candidate.getChild(CANDIDATE_NAME_NODE_ID).get().getValue().toString());
 522         }
 523
 524         return candidateNames;
 525     }
 526
 527     private void searchForEntitiesOwnedBy(final Set<String> ownedBy, final EntityWalker walker) {
 528         LOG.debug("{}: Searching for entities owned by {}", persistenceId(), ownedBy);
 529
 530         searchForEntities((entityTypeNode, entityNode) -> {
 531             Optional<DataContainerChild<? extends PathArgument, ?>> possibleOwner =
 532                     entityNode.getChild(ENTITY_OWNER_NODE_ID);
 533             String currentOwner = possibleOwner.isPresent() ? possibleOwner.get().getValue().toString() : "";
 534             if (ownedBy.contains(currentOwner)) {
 535                 walker.onEntity(entityTypeNode, entityNode);
 536             }
 537         });
 538     }
 539
 540     private void removeCandidateFromEntities(final MemberName member) {
 541         final BatchedModifications modifications = commitCoordinator.newBatchedModifications();
 542         searchForEntities((entityTypeNode, entityNode) -> {
 543             if (hasCandidate(entityNode, member)) {
 544                 YangInstanceIdentifier entityId =
 545                         (YangInstanceIdentifier) entityNode.getIdentifier().getKeyValues().get(ENTITY_ID_QNAME);
 546                 YangInstanceIdentifier candidatePath = candidatePath(
 547                         entityTypeNode.getIdentifier().getKeyValues().get(ENTITY_TYPE_QNAME).toString(),
 548                         entityId, member.getName());
 549
 550                 LOG.info("{}: Found entity {}, removing candidate {}, path {}", persistenceId(), entityId,
 551                         member, candidatePath);
 552
 553                 modifications.addModification(new DeleteModification(candidatePath));
 554             }
 555         });
 556
 557         commitCoordinator.commitModifications(modifications, this);
 558     }
 559
 560     private static boolean hasCandidate(final MapEntryNode entity, final MemberName candidateName) {
 561         return ((MapNode)entity.getChild(CANDIDATE_NODE_ID).get()).getChild(candidateNodeKey(candidateName.getName()))
 562                 .isPresent();
 563     }
 564
 565     private void searchForEntities(final EntityWalker walker) {
 566         Optional<NormalizedNode<?, ?>> possibleEntityTypes = getDataStore().readNode(ENTITY_TYPES_PATH);
 567         if (!possibleEntityTypes.isPresent()) {
 568             return;
 569         }
 570
 571         for (MapEntryNode entityType:  ((MapNode) possibleEntityTypes.get()).getValue()) {
 572             Optional<DataContainerChild<?, ?>> possibleEntities = entityType.getChild(ENTITY_NODE_ID);
 573             if (!possibleEntities.isPresent()) {
 574                 // shouldn't happen but handle anyway
 575                 continue;
 576             }
 577
 578             for (MapEntryNode entity:  ((MapNode) possibleEntities.get()).getValue()) {
 579                 walker.onEntity(entityType, entity);
 580             }
 581         }
 582     }
 583
 584     private void writeNewOwner(final YangInstanceIdentifier entityPath, final String newOwner) {
 585         LOG.debug("{}: Writing new owner {} for entity {}", persistenceId(), newOwner, entityPath);
 586
 587         commitCoordinator.commitModification(new WriteModification(entityPath.node(ENTITY_OWNER_QNAME),
 588                 ImmutableNodes.leafNode(ENTITY_OWNER_NODE_ID, newOwner)), this);
 589     }
 590
 591     /**
 592      * Schedule a new owner selection job. Cancelling any outstanding job if it has not been cancelled.
 593      */
 594     private void scheduleOwnerSelection(final YangInstanceIdentifier entityPath, final Collection<String> allCandidates,
 595                                        final EntityOwnerSelectionStrategy strategy) {
 596         cancelOwnerSelectionTask(entityPath);
 597
 598         LOG.debug("{}: Scheduling owner selection after {} ms", persistenceId(), strategy.getSelectionDelayInMillis());
 599
 600         final Cancellable lastScheduledTask = context().system().scheduler().scheduleOnce(
 601                 FiniteDuration.apply(strategy.getSelectionDelayInMillis(), TimeUnit.MILLISECONDS), self(),
 602                 new SelectOwner(entityPath, allCandidates, strategy), context().system().dispatcher(), self());
 603
 604         entityToScheduledOwnershipTask.put(entityPath, lastScheduledTask);
 605     }
 606
 607     private void cancelOwnerSelectionTask(final YangInstanceIdentifier entityPath) {
 608         final Cancellable lastScheduledTask = entityToScheduledOwnershipTask.get(entityPath);
 609         if (lastScheduledTask != null && !lastScheduledTask.isCancelled()) {
 610             lastScheduledTask.cancel();
 611         }
 612     }
 613
 614     private String newOwner(final String currentOwner, final Collection<String> candidates,
 615             final EntityOwnerSelectionStrategy ownerSelectionStrategy) {
 616         Collection<String> viableCandidates = getViableCandidates(candidates);
 617         if (viableCandidates.isEmpty()) {
 618             return "";
 619         }
 620         return ownerSelectionStrategy.newOwner(currentOwner, viableCandidates);
 621     }
 622
 623     private Collection<String> getViableCandidates(final Collection<String> candidates) {
 624         Collection<String> viableCandidates = new ArrayList<>();
 625
 626         for (String candidate : candidates) {
 627             if (!downPeerMemberNames.contains(MemberName.forName(candidate))) {
 628                 viableCandidates.add(candidate);
 629             }
 630         }
 631         return viableCandidates;
 632     }
 633
 634     private String getCurrentOwner(final YangInstanceIdentifier entityId) {
 635         Optional<NormalizedNode<?, ?>> optionalEntityOwner = getDataStore().readNode(entityId.node(ENTITY_OWNER_QNAME));
 636         if (optionalEntityOwner.isPresent()) {
 637             return optionalEntityOwner.get().getValue().toString();
 638         }
 639         return null;
 640     }
 641
 642     @FunctionalInterface
 643     private interface EntityWalker {
 644         void onEntity(MapEntryNode entityTypeNode, MapEntryNode entityNode);
 645     }
 646
 647     public static Builder newBuilder() {
 648         return new Builder();
 649     }
 650
 651     static class Builder extends Shard.AbstractBuilder<Builder, EntityOwnershipShard> {
 652         private MemberName localMemberName;
 653         private EntityOwnerSelectionStrategyConfig ownerSelectionStrategyConfig;
 654
 655         protected Builder() {
 656             super(EntityOwnershipShard.class);
 657         }
 658
 659         Builder localMemberName(final MemberName newLocalMemberName) {
 660             checkSealed();
 661             this.localMemberName = newLocalMemberName;
 662             return this;
 663         }
 664
 665         Builder ownerSelectionStrategyConfig(final EntityOwnerSelectionStrategyConfig newOwnerSelectionStrategyConfig) {
 666             checkSealed();
 667             this.ownerSelectionStrategyConfig = newOwnerSelectionStrategyConfig;
 668             return this;
 669         }
 670
 671         @Override
 672         protected void verify() {
 673             super.verify();
 674             Preconditions.checkNotNull(localMemberName, "localMemberName should not be null");
 675             Preconditions.checkNotNull(ownerSelectionStrategyConfig, "ownerSelectionStrategyConfig should not be null");
 676         }
 677     }
 678 }