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

   1 /*
   2  * Copyright (c) 2015 Cisco 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;
   9
  10 import akka.actor.ActorRef;
  11 import akka.util.Timeout;
  12 import com.google.common.annotations.VisibleForTesting;
  13 import com.google.common.base.MoreObjects;
  14 import com.google.common.base.Optional;
  15 import com.google.common.base.Preconditions;
  16 import com.google.common.base.Stopwatch;
  17 import com.google.common.base.Ticker;
  18 import com.google.common.base.Verify;
  19 import com.google.common.collect.ImmutableList;
  20 import com.google.common.collect.ImmutableMap;
  21 import com.google.common.collect.ImmutableMap.Builder;
  22 import com.google.common.collect.Iterables;
  23 import com.google.common.primitives.UnsignedLong;
  24 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  25 import java.io.File;
  26 import java.io.IOException;
  27 import java.util.AbstractMap.SimpleEntry;
  28 import java.util.ArrayDeque;
  29 import java.util.ArrayList;
  30 import java.util.Collection;
  31 import java.util.HashMap;
  32 import java.util.Iterator;
  33 import java.util.Map;
  34 import java.util.Map.Entry;
  35 import java.util.Queue;
  36 import java.util.concurrent.ExecutionException;
  37 import java.util.concurrent.TimeUnit;
  38 import java.util.concurrent.TimeoutException;
  39 import java.util.function.Consumer;
  40 import java.util.function.UnaryOperator;
  41 import javax.annotation.Nonnull;
  42 import javax.annotation.Nullable;
  43 import javax.annotation.concurrent.NotThreadSafe;
  44 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  45 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  46 import org.opendaylight.controller.cluster.datastore.DataTreeCohortActorRegistry.CohortRegistryCommand;
  47 import org.opendaylight.controller.cluster.datastore.ShardDataTreeCohort.State;
  48 import org.opendaylight.controller.cluster.datastore.persisted.AbstractIdentifiablePayload;
  49 import org.opendaylight.controller.cluster.datastore.persisted.CloseLocalHistoryPayload;
  50 import org.opendaylight.controller.cluster.datastore.persisted.CommitTransactionPayload;
  51 import org.opendaylight.controller.cluster.datastore.persisted.CreateLocalHistoryPayload;
  52 import org.opendaylight.controller.cluster.datastore.persisted.MetadataShardDataTreeSnapshot;
  53 import org.opendaylight.controller.cluster.datastore.persisted.PurgeLocalHistoryPayload;
  54 import org.opendaylight.controller.cluster.datastore.persisted.ShardDataTreeSnapshot;
  55 import org.opendaylight.controller.cluster.datastore.persisted.ShardDataTreeSnapshotMetadata;
  56 import org.opendaylight.controller.cluster.datastore.utils.DataTreeModificationOutput;
  57 import org.opendaylight.controller.cluster.datastore.utils.PruningDataTreeModification;
  58 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  59 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataBroker.DataChangeScope;
  60 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
  61 import org.opendaylight.controller.md.sal.common.api.data.OptimisticLockFailedException;
  62 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
  63 import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeChangeListener;
  64 import org.opendaylight.controller.md.sal.dom.store.impl.DataChangeListenerRegistration;
  65 import org.opendaylight.yangtools.concepts.Identifier;
  66 import org.opendaylight.yangtools.concepts.ListenerRegistration;
  67 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  68 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  69 import org.opendaylight.yangtools.yang.data.api.schema.tree.ConflictingModificationAppliedException;
  70 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
  71 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateTip;
  72 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidates;
  73 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
  74 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeSnapshot;
  75 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeTip;
  76 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
  77 import org.opendaylight.yangtools.yang.data.api.schema.tree.TipProducingDataTree;
  78 import org.opendaylight.yangtools.yang.data.api.schema.tree.TipProducingDataTreeTip;
  79 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
  80 import org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTreeFactory;
  81 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  82 import org.slf4j.Logger;
  83 import org.slf4j.LoggerFactory;
  84 import scala.concurrent.duration.Duration;
  85
  86 /**
  87  * Internal shard state, similar to a DOMStore, but optimized for use in the actor system,
  88  * e.g. it does not expose public interfaces and assumes it is only ever called from a
  89  * single thread.
  90  *
  91  * <p>
  92  * This class is not part of the API contract and is subject to change at any time.
  93  */
  94 @NotThreadSafe
  95 public class ShardDataTree extends ShardDataTreeTransactionParent {
  96     private static final class CommitEntry {
  97         final SimpleShardDataTreeCohort cohort;
  98         long lastAccess;
  99
 100         CommitEntry(final SimpleShardDataTreeCohort cohort, final long now) {
 101             this.cohort = Preconditions.checkNotNull(cohort);
 102             lastAccess = now;
 103         }
 104     }
 105
 106     private static final Timeout COMMIT_STEP_TIMEOUT = new Timeout(Duration.create(5, TimeUnit.SECONDS));
 107     private static final Logger LOG = LoggerFactory.getLogger(ShardDataTree.class);
 108
 109     private final Map<LocalHistoryIdentifier, ShardDataTreeTransactionChain> transactionChains = new HashMap<>();
 110
 111     private final DataTreeCohortActorRegistry cohortRegistry = new DataTreeCohortActorRegistry();
 112     private final Queue<CommitEntry> pendingTransactions = new ArrayDeque<>();
 113     private final Queue<CommitEntry> pendingCommits = new ArrayDeque<>();
 114     private final Queue<CommitEntry> pendingFinishCommits = new ArrayDeque<>();
 115
 116     /**
 117      * Callbacks that need to be invoked once a payload is replicated.
 118      */
 119     private final Map<Payload, Runnable> replicationCallbacks = new HashMap<>();
 120
 121     private final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher;
 122     private final ShardDataChangeListenerPublisher dataChangeListenerPublisher;
 123     private final Collection<ShardDataTreeMetadata<?>> metadata;
 124     private final TipProducingDataTree dataTree;
 125     private final String logContext;
 126     private final Shard shard;
 127     private Runnable runOnPendingTransactionsComplete;
 128
 129     /**
 130      * Optimistic {@link DataTreeCandidate} preparation. Since our DataTree implementation is a
 131      * {@link TipProducingDataTree}, each {@link DataTreeCandidate} is also a {@link DataTreeTip}, e.g. another
 132      * candidate can be prepared on top of it. They still need to be committed in sequence. Here we track the current
 133      * tip of the data tree, which is the last DataTreeCandidate we have in flight, or the DataTree itself.
 134      */
 135     private TipProducingDataTreeTip tip;
 136
 137     private SchemaContext schemaContext;
 138
 139     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TipProducingDataTree dataTree,
 140             final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher,
 141             final ShardDataChangeListenerPublisher dataChangeListenerPublisher, final String logContext,
 142             final ShardDataTreeMetadata<?>... metadata) {
 143         this.dataTree = Preconditions.checkNotNull(dataTree);
 144         updateSchemaContext(schemaContext);
 145
 146         this.shard = Preconditions.checkNotNull(shard);
 147         this.treeChangeListenerPublisher = Preconditions.checkNotNull(treeChangeListenerPublisher);
 148         this.dataChangeListenerPublisher = Preconditions.checkNotNull(dataChangeListenerPublisher);
 149         this.logContext = Preconditions.checkNotNull(logContext);
 150         this.metadata = ImmutableList.copyOf(metadata);
 151         tip = dataTree;
 152     }
 153
 154     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TreeType treeType,
 155             final YangInstanceIdentifier root,
 156             final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher,
 157             final ShardDataChangeListenerPublisher dataChangeListenerPublisher, final String logContext) {
 158         this(shard, schemaContext, InMemoryDataTreeFactory.getInstance().create(treeType, root),
 159                 treeChangeListenerPublisher, dataChangeListenerPublisher, logContext);
 160     }
 161
 162     @VisibleForTesting
 163     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TreeType treeType) {
 164         this(shard, schemaContext, treeType, YangInstanceIdentifier.EMPTY,
 165                 new DefaultShardDataTreeChangeListenerPublisher(), new DefaultShardDataChangeListenerPublisher(), "");
 166     }
 167
 168     final String logContext() {
 169         return logContext;
 170     }
 171
 172     final Ticker ticker() {
 173         return shard.ticker();
 174     }
 175
 176     public TipProducingDataTree getDataTree() {
 177         return dataTree;
 178     }
 179
 180     SchemaContext getSchemaContext() {
 181         return schemaContext;
 182     }
 183
 184     void updateSchemaContext(final SchemaContext newSchemaContext) {
 185         dataTree.setSchemaContext(newSchemaContext);
 186         this.schemaContext = Preconditions.checkNotNull(newSchemaContext);
 187     }
 188
 189     /**
 190      * Take a snapshot of current state for later recovery.
 191      *
 192      * @return A state snapshot
 193      */
 194     @Nonnull ShardDataTreeSnapshot takeStateSnapshot() {
 195         final NormalizedNode<?, ?> rootNode = dataTree.takeSnapshot().readNode(YangInstanceIdentifier.EMPTY).get();
 196         final Builder<Class<? extends ShardDataTreeSnapshotMetadata<?>>, ShardDataTreeSnapshotMetadata<?>> metaBuilder =
 197                 ImmutableMap.builder();
 198
 199         for (ShardDataTreeMetadata<?> m : metadata) {
 200             final ShardDataTreeSnapshotMetadata<?> meta = m.toSnapshot();
 201             if (meta != null) {
 202                 metaBuilder.put(meta.getType(), meta);
 203             }
 204         }
 205
 206         return new MetadataShardDataTreeSnapshot(rootNode, metaBuilder.build());
 207     }
 208
 209     private boolean anyPendingTransactions() {
 210         return !pendingTransactions.isEmpty() || !pendingCommits.isEmpty() || !pendingFinishCommits.isEmpty();
 211     }
 212
 213     private void applySnapshot(@Nonnull final ShardDataTreeSnapshot snapshot,
 214             final UnaryOperator<DataTreeModification> wrapper) throws DataValidationFailedException {
 215         final Stopwatch elapsed = Stopwatch.createStarted();
 216
 217         if (anyPendingTransactions()) {
 218             LOG.warn("{}: applying state snapshot with pending transactions", logContext);
 219         }
 220
 221         final Map<Class<? extends ShardDataTreeSnapshotMetadata<?>>, ShardDataTreeSnapshotMetadata<?>> snapshotMeta;
 222         if (snapshot instanceof MetadataShardDataTreeSnapshot) {
 223             snapshotMeta = ((MetadataShardDataTreeSnapshot) snapshot).getMetadata();
 224         } else {
 225             snapshotMeta = ImmutableMap.of();
 226         }
 227
 228         for (ShardDataTreeMetadata<?> m : metadata) {
 229             final ShardDataTreeSnapshotMetadata<?> s = snapshotMeta.get(m.getSupportedType());
 230             if (s != null) {
 231                 m.applySnapshot(s);
 232             } else {
 233                 m.reset();
 234             }
 235         }
 236
 237         final DataTreeModification mod = wrapper.apply(dataTree.takeSnapshot().newModification());
 238         // delete everything first
 239         mod.delete(YangInstanceIdentifier.EMPTY);
 240
 241         final java.util.Optional<NormalizedNode<?, ?>> maybeNode = snapshot.getRootNode();
 242         if (maybeNode.isPresent()) {
 243             // Add everything from the remote node back
 244             mod.write(YangInstanceIdentifier.EMPTY, maybeNode.get());
 245         }
 246         mod.ready();
 247
 248         final DataTreeModification unwrapped = unwrap(mod);
 249         dataTree.validate(unwrapped);
 250         DataTreeCandidateTip candidate = dataTree.prepare(unwrapped);
 251         dataTree.commit(candidate);
 252         notifyListeners(candidate);
 253
 254         LOG.debug("{}: state snapshot applied in %s", logContext, elapsed);
 255     }
 256
 257     /**
 258      * Apply a snapshot coming from the leader. This method assumes the leader and follower SchemaContexts match and
 259      * does not perform any pruning.
 260      *
 261      * @param snapshot Snapshot that needs to be applied
 262      * @throws DataValidationFailedException when the snapshot fails to apply
 263      */
 264     void applySnapshot(@Nonnull final ShardDataTreeSnapshot snapshot) throws DataValidationFailedException {
 265         applySnapshot(snapshot, UnaryOperator.identity());
 266     }
 267
 268     private PruningDataTreeModification wrapWithPruning(final DataTreeModification delegate) {
 269         return new PruningDataTreeModification(delegate, dataTree, schemaContext);
 270     }
 271
 272     private static DataTreeModification unwrap(final DataTreeModification modification) {
 273         if (modification instanceof PruningDataTreeModification) {
 274             return ((PruningDataTreeModification)modification).delegate();
 275         }
 276         return modification;
 277     }
 278
 279     /**
 280      * Apply a snapshot coming from recovery. This method does not assume the SchemaContexts match and performs data
 281      * pruning in an attempt to adjust the state to our current SchemaContext.
 282      *
 283      * @param snapshot Snapshot that needs to be applied
 284      * @throws DataValidationFailedException when the snapshot fails to apply
 285      */
 286     void applyRecoverySnapshot(final @Nonnull ShardDataTreeSnapshot snapshot) throws DataValidationFailedException {
 287         applySnapshot(snapshot, this::wrapWithPruning);
 288     }
 289
 290     @SuppressWarnings("checkstyle:IllegalCatch")
 291     private void applyRecoveryCandidate(final DataTreeCandidate candidate) throws DataValidationFailedException {
 292         final PruningDataTreeModification mod = wrapWithPruning(dataTree.takeSnapshot().newModification());
 293         DataTreeCandidates.applyToModification(mod, candidate);
 294         mod.ready();
 295
 296         final DataTreeModification unwrapped = mod.delegate();
 297         LOG.trace("{}: Applying recovery modification {}", logContext, unwrapped);
 298
 299         try {
 300             dataTree.validate(unwrapped);
 301             dataTree.commit(dataTree.prepare(unwrapped));
 302         } catch (Exception e) {
 303             File file = new File(System.getProperty("karaf.data", "."),
 304                     "failed-recovery-payload-" + logContext + ".out");
 305             DataTreeModificationOutput.toFile(file, unwrapped);
 306             throw new IllegalStateException(String.format(
 307                     "%s: Failed to apply recovery payload. Modification data was written to file %s",
 308                     logContext, file), e);
 309         }
 310     }
 311
 312     /**
 313      * Apply a payload coming from recovery. This method does not assume the SchemaContexts match and performs data
 314      * pruning in an attempt to adjust the state to our current SchemaContext.
 315      *
 316      * @param payload Payload
 317      * @throws IOException when the snapshot fails to deserialize
 318      * @throws DataValidationFailedException when the snapshot fails to apply
 319      */
 320     void applyRecoveryPayload(final @Nonnull Payload payload) throws IOException, DataValidationFailedException {
 321         if (payload instanceof CommitTransactionPayload) {
 322             final Entry<TransactionIdentifier, DataTreeCandidate> e =
 323                     ((CommitTransactionPayload) payload).getCandidate();
 324             applyRecoveryCandidate(e.getValue());
 325             allMetadataCommittedTransaction(e.getKey());
 326         } else if (payload instanceof CreateLocalHistoryPayload) {
 327             allMetadataCreatedLocalHistory(((CreateLocalHistoryPayload) payload).getIdentifier());
 328         } else if (payload instanceof CloseLocalHistoryPayload) {
 329             allMetadataClosedLocalHistory(((CloseLocalHistoryPayload) payload).getIdentifier());
 330         } else if (payload instanceof PurgeLocalHistoryPayload) {
 331             allMetadataPurgedLocalHistory(((PurgeLocalHistoryPayload) payload).getIdentifier());
 332         } else if (payload instanceof DataTreeCandidatePayload) {
 333             applyRecoveryCandidate(((DataTreeCandidatePayload) payload).getCandidate());
 334         } else {
 335             LOG.debug("{}: ignoring unhandled payload {}", logContext, payload);
 336         }
 337     }
 338
 339     private void applyReplicatedCandidate(final Identifier identifier, final DataTreeCandidate foreign)
 340             throws DataValidationFailedException {
 341         LOG.debug("{}: Applying foreign transaction {}", logContext, identifier);
 342
 343         final DataTreeModification mod = dataTree.takeSnapshot().newModification();
 344         DataTreeCandidates.applyToModification(mod, foreign);
 345         mod.ready();
 346
 347         LOG.trace("{}: Applying foreign modification {}", logContext, mod);
 348         dataTree.validate(mod);
 349         final DataTreeCandidate candidate = dataTree.prepare(mod);
 350         dataTree.commit(candidate);
 351
 352         notifyListeners(candidate);
 353     }
 354
 355     /**
 356      * Apply a payload coming from the leader, which could actually be us. This method assumes the leader and follower
 357      * SchemaContexts match and does not perform any pruning.
 358      *
 359      * @param identifier Payload identifier as returned from RaftActor
 360      * @param payload Payload
 361      * @throws IOException when the snapshot fails to deserialize
 362      * @throws DataValidationFailedException when the snapshot fails to apply
 363      */
 364     void applyReplicatedPayload(final Identifier identifier, final Payload payload) throws IOException,
 365             DataValidationFailedException {
 366         /*
 367          * This is a bit more involved than it needs to be due to to the fact we do not want to be touching the payload
 368          * if we are the leader and it has originated with us.
 369          *
 370          * The identifier will only ever be non-null when we were the leader which achieved consensus. Unfortunately,
 371          * though, this may not be the case anymore, as we are being called some time afterwards and we may not be
 372          * acting in that capacity anymore.
 373          *
 374          * In any case, we know that this is an entry coming from replication, hence we can be sure we will not observe
 375          * pre-Boron state -- which limits the number of options here.
 376          */
 377         if (payload instanceof CommitTransactionPayload) {
 378             if (identifier == null) {
 379                 final Entry<TransactionIdentifier, DataTreeCandidate> e =
 380                         ((CommitTransactionPayload) payload).getCandidate();
 381                 applyReplicatedCandidate(e.getKey(), e.getValue());
 382                 allMetadataCommittedTransaction(e.getKey());
 383             } else {
 384                 Verify.verify(identifier instanceof TransactionIdentifier);
 385                 payloadReplicationComplete((TransactionIdentifier) identifier);
 386             }
 387         } else if (payload instanceof CloseLocalHistoryPayload) {
 388             if (identifier != null) {
 389                 payloadReplicationComplete((CloseLocalHistoryPayload) payload);
 390             } else {
 391                 allMetadataClosedLocalHistory(((CloseLocalHistoryPayload) payload).getIdentifier());
 392             }
 393         } else if (payload instanceof CreateLocalHistoryPayload) {
 394             if (identifier != null) {
 395                 payloadReplicationComplete((CreateLocalHistoryPayload)payload);
 396             } else {
 397                 allMetadataCreatedLocalHistory(((CreateLocalHistoryPayload) payload).getIdentifier());
 398             }
 399         } else if (payload instanceof PurgeLocalHistoryPayload) {
 400             if (identifier != null) {
 401                 payloadReplicationComplete((PurgeLocalHistoryPayload)payload);
 402             } else {
 403                 allMetadataPurgedLocalHistory(((PurgeLocalHistoryPayload) payload).getIdentifier());
 404             }
 405         } else {
 406             LOG.warn("{}: ignoring unhandled identifier {} payload {}", logContext, identifier, payload);
 407         }
 408     }
 409
 410     private void replicatePayload(final Identifier id, final Payload payload, @Nullable final Runnable callback) {
 411         if (callback != null) {
 412             replicationCallbacks.put(payload, callback);
 413         }
 414         shard.persistPayload(id, payload, true);
 415     }
 416
 417     private void payloadReplicationComplete(final AbstractIdentifiablePayload<?> payload) {
 418         final Runnable callback = replicationCallbacks.remove(payload);
 419         if (callback != null) {
 420             LOG.debug("{}: replication of {} completed, invoking {}", logContext, payload.getIdentifier(), callback);
 421             callback.run();
 422         } else {
 423             LOG.debug("{}: replication of {} has no callback", logContext, payload.getIdentifier());
 424         }
 425     }
 426
 427     private void payloadReplicationComplete(final TransactionIdentifier txId) {
 428         final CommitEntry current = pendingFinishCommits.peek();
 429         if (current == null) {
 430             LOG.warn("{}: No outstanding transactions, ignoring consensus on transaction {}", logContext, txId);
 431             return;
 432         }
 433
 434         if (!current.cohort.getIdentifier().equals(txId)) {
 435             LOG.debug("{}: Head of pendingFinishCommits queue is {}, ignoring consensus on transaction {}", logContext,
 436                 current.cohort.getIdentifier(), txId);
 437             return;
 438         }
 439
 440         finishCommit(current.cohort);
 441     }
 442
 443     private void allMetadataCommittedTransaction(final TransactionIdentifier txId) {
 444         for (ShardDataTreeMetadata<?> m : metadata) {
 445             m.onTransactionCommitted(txId);
 446         }
 447     }
 448
 449     private void allMetadataCreatedLocalHistory(final LocalHistoryIdentifier historyId) {
 450         for (ShardDataTreeMetadata<?> m : metadata) {
 451             m.onHistoryCreated(historyId);
 452         }
 453     }
 454
 455     private void allMetadataClosedLocalHistory(final LocalHistoryIdentifier historyId) {
 456         for (ShardDataTreeMetadata<?> m : metadata) {
 457             m.onHistoryClosed(historyId);
 458         }
 459     }
 460
 461     private void allMetadataPurgedLocalHistory(final LocalHistoryIdentifier historyId) {
 462         for (ShardDataTreeMetadata<?> m : metadata) {
 463             m.onHistoryPurged(historyId);
 464         }
 465     }
 466
 467     ShardDataTreeTransactionChain ensureTransactionChain(final LocalHistoryIdentifier historyId) {
 468         ShardDataTreeTransactionChain chain = transactionChains.get(historyId);
 469         if (chain == null) {
 470             chain = new ShardDataTreeTransactionChain(historyId, this);
 471             transactionChains.put(historyId, chain);
 472             shard.persistPayload(historyId, CreateLocalHistoryPayload.create(historyId), true);
 473         }
 474
 475         return chain;
 476     }
 477
 478     ReadOnlyShardDataTreeTransaction newReadOnlyTransaction(final TransactionIdentifier txId) {
 479         if (txId.getHistoryId().getHistoryId() == 0) {
 480             return new ReadOnlyShardDataTreeTransaction(txId, dataTree.takeSnapshot());
 481         }
 482
 483         return ensureTransactionChain(txId.getHistoryId()).newReadOnlyTransaction(txId);
 484     }
 485
 486     ReadWriteShardDataTreeTransaction newReadWriteTransaction(final TransactionIdentifier txId) {
 487         if (txId.getHistoryId().getHistoryId() == 0) {
 488             return new ReadWriteShardDataTreeTransaction(ShardDataTree.this, txId, dataTree.takeSnapshot()
 489                     .newModification());
 490         }
 491
 492         return ensureTransactionChain(txId.getHistoryId()).newReadWriteTransaction(txId);
 493     }
 494
 495     @VisibleForTesting
 496     public void notifyListeners(final DataTreeCandidate candidate) {
 497         treeChangeListenerPublisher.publishChanges(candidate, logContext);
 498         dataChangeListenerPublisher.publishChanges(candidate, logContext);
 499     }
 500
 501     void notifyOfInitialData(final DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
 502             NormalizedNode<?, ?>>> listenerReg, final Optional<DataTreeCandidate> currentState) {
 503         if (currentState.isPresent()) {
 504             ShardDataChangeListenerPublisher localPublisher = dataChangeListenerPublisher.newInstance();
 505             localPublisher.registerDataChangeListener(listenerReg.getPath(), listenerReg.getInstance(),
 506                     listenerReg.getScope());
 507             localPublisher.publishChanges(currentState.get(), logContext);
 508         }
 509     }
 510
 511     void notifyOfInitialData(final YangInstanceIdentifier path, final DOMDataTreeChangeListener listener,
 512             final Optional<DataTreeCandidate> currentState) {
 513         if (currentState.isPresent()) {
 514             ShardDataTreeChangeListenerPublisher localPublisher = treeChangeListenerPublisher.newInstance();
 515             localPublisher.registerTreeChangeListener(path, listener);
 516             localPublisher.publishChanges(currentState.get(), logContext);
 517         }
 518     }
 519
 520     /**
 521      * Immediately close all transaction chains.
 522      */
 523     void closeAllTransactionChains() {
 524         for (ShardDataTreeTransactionChain chain : transactionChains.values()) {
 525             chain.close();
 526         }
 527
 528         transactionChains.clear();
 529     }
 530
 531     /**
 532      * Close a single transaction chain.
 533      *
 534      * @param id History identifier
 535      * @param callback Callback to invoke upon completion, may be null
 536      */
 537     void closeTransactionChain(final LocalHistoryIdentifier id, @Nullable final Runnable callback) {
 538         final ShardDataTreeTransactionChain chain = transactionChains.get(id);
 539         if (chain == null) {
 540             LOG.debug("{}: Closing non-existent transaction chain {}", logContext, id);
 541             if (callback != null) {
 542                 callback.run();
 543             }
 544             return;
 545         }
 546
 547         chain.close();
 548         replicatePayload(id, CloseLocalHistoryPayload.create(id), callback);
 549     }
 550
 551     /**
 552      * Purge a single transaction chain.
 553      *
 554      * @param id History identifier
 555      * @param callback Callback to invoke upon completion, may be null
 556      */
 557     void purgeTransactionChain(final LocalHistoryIdentifier id, @Nullable final Runnable callback) {
 558         final ShardDataTreeTransactionChain chain = transactionChains.remove(id);
 559         if (chain == null) {
 560             LOG.debug("{}: Purging non-existent transaction chain {}", logContext, id);
 561             if (callback != null) {
 562                 callback.run();
 563             }
 564             return;
 565         }
 566
 567         replicatePayload(id, PurgeLocalHistoryPayload.create(id), callback);
 568     }
 569
 570     Entry<DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>>,
 571             Optional<DataTreeCandidate>> registerChangeListener(final YangInstanceIdentifier path,
 572                     final AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> listener,
 573                     final DataChangeScope scope) {
 574         DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>> reg =
 575                 dataChangeListenerPublisher.registerDataChangeListener(path, listener, scope);
 576
 577         return new SimpleEntry<>(reg, readCurrentData());
 578     }
 579
 580     private Optional<DataTreeCandidate> readCurrentData() {
 581         final Optional<NormalizedNode<?, ?>> currentState =
 582                 dataTree.takeSnapshot().readNode(YangInstanceIdentifier.EMPTY);
 583         return currentState.isPresent() ? Optional.of(DataTreeCandidates.fromNormalizedNode(
 584             YangInstanceIdentifier.EMPTY, currentState.get())) : Optional.<DataTreeCandidate>absent();
 585     }
 586
 587     public Entry<ListenerRegistration<DOMDataTreeChangeListener>, Optional<DataTreeCandidate>>
 588             registerTreeChangeListener(final YangInstanceIdentifier path, final DOMDataTreeChangeListener listener) {
 589         final ListenerRegistration<DOMDataTreeChangeListener> reg =
 590                 treeChangeListenerPublisher.registerTreeChangeListener(path, listener);
 591
 592         return new SimpleEntry<>(reg, readCurrentData());
 593     }
 594
 595     int getQueueSize() {
 596         return pendingTransactions.size() + pendingCommits.size() + pendingFinishCommits.size();
 597     }
 598
 599     @Override
 600     void abortTransaction(final AbstractShardDataTreeTransaction<?> transaction) {
 601         // Intentional no-op
 602     }
 603
 604     @Override
 605     ShardDataTreeCohort finishTransaction(final ReadWriteShardDataTreeTransaction transaction) {
 606         final DataTreeModification snapshot = transaction.getSnapshot();
 607         snapshot.ready();
 608
 609         return createReadyCohort(transaction.getIdentifier(), snapshot);
 610     }
 611
 612     public Optional<NormalizedNode<?, ?>> readNode(final YangInstanceIdentifier path) {
 613         return dataTree.takeSnapshot().readNode(path);
 614     }
 615
 616     DataTreeSnapshot takeSnapshot() {
 617         return dataTree.takeSnapshot();
 618     }
 619
 620     @VisibleForTesting
 621     public DataTreeModification newModification() {
 622         return dataTree.takeSnapshot().newModification();
 623     }
 624
 625     /**
 626      * Commits a modification.
 627      *
 628      * @deprecated This method violates DataTree containment and will be removed.
 629      */
 630     @VisibleForTesting
 631     @Deprecated
 632     public DataTreeCandidate commit(final DataTreeModification modification) throws DataValidationFailedException {
 633         // Direct modification commit is a utility, which cannot be used while we have transactions in-flight
 634         Preconditions.checkState(tip == dataTree, "Cannot modify data tree while transacgitons are pending");
 635
 636         modification.ready();
 637         dataTree.validate(modification);
 638         DataTreeCandidate candidate = dataTree.prepare(modification);
 639         dataTree.commit(candidate);
 640         return candidate;
 641     }
 642
 643     public Collection<ShardDataTreeCohort> getAndClearPendingTransactions() {
 644         Collection<ShardDataTreeCohort> ret = new ArrayList<>(getQueueSize());
 645
 646         for (CommitEntry entry: pendingFinishCommits) {
 647             ret.add(entry.cohort);
 648         }
 649
 650         for (CommitEntry entry: pendingCommits) {
 651             ret.add(entry.cohort);
 652         }
 653
 654         for (CommitEntry entry: pendingTransactions) {
 655             ret.add(entry.cohort);
 656         }
 657
 658         pendingFinishCommits.clear();
 659         pendingCommits.clear();
 660         pendingTransactions.clear();
 661         tip = dataTree;
 662         return ret;
 663     }
 664
 665     @SuppressWarnings("checkstyle:IllegalCatch")
 666     private void processNextPendingTransaction() {
 667         processNextPending(pendingTransactions, State.CAN_COMMIT_PENDING, entry -> {
 668             final SimpleShardDataTreeCohort cohort = entry.cohort;
 669             final DataTreeModification modification = cohort.getDataTreeModification();
 670
 671             LOG.debug("{}: Validating transaction {}", logContext, cohort.getIdentifier());
 672             Exception cause;
 673             try {
 674                 tip.validate(modification);
 675                 LOG.debug("{}: Transaction {} validated", logContext, cohort.getIdentifier());
 676                 cohort.successfulCanCommit();
 677                 entry.lastAccess = ticker().read();
 678                 return;
 679             } catch (ConflictingModificationAppliedException e) {
 680                 LOG.warn("{}: Store Tx {}: Conflicting modification for path {}.", logContext, cohort.getIdentifier(),
 681                     e.getPath());
 682                 cause = new OptimisticLockFailedException("Optimistic lock failed.", e);
 683             } catch (DataValidationFailedException e) {
 684                 LOG.warn("{}: Store Tx {}: Data validation failed for path {}.", logContext, cohort.getIdentifier(),
 685                     e.getPath(), e);
 686
 687                 // For debugging purposes, allow dumping of the modification. Coupled with the above
 688                 // precondition log, it should allow us to understand what went on.
 689                 LOG.debug("{}: Store Tx {}: modifications: {} tree: {}", cohort.getIdentifier(), modification,
 690                         dataTree);
 691                 cause = new TransactionCommitFailedException("Data did not pass validation.", e);
 692             } catch (Exception e) {
 693                 LOG.warn("{}: Unexpected failure in validation phase", logContext, e);
 694                 cause = e;
 695             }
 696
 697             // Failure path: propagate the failure, remove the transaction from the queue and loop to the next one
 698             pendingTransactions.poll().cohort.failedCanCommit(cause);
 699         });
 700     }
 701
 702     private void processNextPending() {
 703         processNextPendingCommit();
 704         processNextPendingTransaction();
 705     }
 706
 707     private void processNextPending(final Queue<CommitEntry> queue, final State allowedState,
 708             final Consumer<CommitEntry> processor) {
 709         while (!queue.isEmpty()) {
 710             final CommitEntry entry = queue.peek();
 711             final SimpleShardDataTreeCohort cohort = entry.cohort;
 712
 713             if (cohort.isFailed()) {
 714                 LOG.debug("{}: Removing failed transaction {}", logContext, cohort.getIdentifier());
 715                 queue.remove();
 716                 continue;
 717             }
 718
 719             if (cohort.getState() == allowedState) {
 720                 processor.accept(entry);
 721             }
 722
 723             break;
 724         }
 725
 726         maybeRunOperationOnPendingTransactionsComplete();
 727     }
 728
 729     private void processNextPendingCommit() {
 730         processNextPending(pendingCommits, State.COMMIT_PENDING,
 731             entry -> startCommit(entry.cohort, entry.cohort.getCandidate()));
 732     }
 733
 734     private boolean peekNextPendingCommit() {
 735         final CommitEntry first = pendingCommits.peek();
 736         return first != null && first.cohort.getState() == State.COMMIT_PENDING;
 737     }
 738
 739     void startCanCommit(final SimpleShardDataTreeCohort cohort) {
 740         final SimpleShardDataTreeCohort current = pendingTransactions.peek().cohort;
 741         if (!cohort.equals(current)) {
 742             LOG.debug("{}: Transaction {} scheduled for canCommit step", logContext, cohort.getIdentifier());
 743             return;
 744         }
 745
 746         processNextPendingTransaction();
 747     }
 748
 749     private void failPreCommit(final Exception cause) {
 750         shard.getShardMBean().incrementFailedTransactionsCount();
 751         pendingTransactions.poll().cohort.failedPreCommit(cause);
 752         processNextPendingTransaction();
 753     }
 754
 755     @SuppressWarnings("checkstyle:IllegalCatch")
 756     void startPreCommit(final SimpleShardDataTreeCohort cohort) {
 757         final CommitEntry entry = pendingTransactions.peek();
 758         Preconditions.checkState(entry != null, "Attempted to pre-commit of %s when no transactions pending", cohort);
 759
 760         final SimpleShardDataTreeCohort current = entry.cohort;
 761         Verify.verify(cohort.equals(current), "Attempted to pre-commit %s while %s is pending", cohort, current);
 762
 763         LOG.debug("{}: Preparing transaction {}", logContext, current.getIdentifier());
 764
 765         final DataTreeCandidateTip candidate;
 766         try {
 767             candidate = tip.prepare(cohort.getDataTreeModification());
 768             cohort.userPreCommit(candidate);
 769         } catch (ExecutionException | TimeoutException | RuntimeException e) {
 770             failPreCommit(e);
 771             return;
 772         }
 773
 774         // Set the tip of the data tree.
 775         tip = Verify.verifyNotNull(candidate);
 776
 777         entry.lastAccess = ticker().read();
 778
 779         pendingTransactions.remove();
 780         pendingCommits.add(entry);
 781
 782         LOG.debug("{}: Transaction {} prepared", logContext, current.getIdentifier());
 783
 784         cohort.successfulPreCommit(candidate);
 785
 786         processNextPendingTransaction();
 787     }
 788
 789     private void failCommit(final Exception cause) {
 790         shard.getShardMBean().incrementFailedTransactionsCount();
 791         pendingFinishCommits.poll().cohort.failedCommit(cause);
 792         processNextPending();
 793     }
 794
 795     @SuppressWarnings("checkstyle:IllegalCatch")
 796     private void finishCommit(final SimpleShardDataTreeCohort cohort) {
 797         final TransactionIdentifier txId = cohort.getIdentifier();
 798         final DataTreeCandidate candidate = cohort.getCandidate();
 799
 800         LOG.debug("{}: Resuming commit of transaction {}", logContext, txId);
 801
 802         if (tip == candidate) {
 803             // All pending candidates have been committed, reset the tip to the data tree.
 804             tip = dataTree;
 805         }
 806
 807         try {
 808             dataTree.commit(candidate);
 809         } catch (Exception e) {
 810             LOG.error("{}: Failed to commit transaction {}", logContext, txId, e);
 811             failCommit(e);
 812             return;
 813         }
 814
 815         shard.getShardMBean().incrementCommittedTransactionCount();
 816         shard.getShardMBean().setLastCommittedTransactionTime(System.currentTimeMillis());
 817
 818         // FIXME: propagate journal index
 819         pendingFinishCommits.poll().cohort.successfulCommit(UnsignedLong.ZERO);
 820
 821         LOG.trace("{}: Transaction {} committed, proceeding to notify", logContext, txId);
 822         notifyListeners(candidate);
 823
 824         processNextPending();
 825     }
 826
 827     void startCommit(final SimpleShardDataTreeCohort cohort, final DataTreeCandidate candidate) {
 828         final CommitEntry entry = pendingCommits.peek();
 829         Preconditions.checkState(entry != null, "Attempted to start commit of %s when no transactions pending", cohort);
 830
 831         final SimpleShardDataTreeCohort current = entry.cohort;
 832         if (!cohort.equals(current)) {
 833             LOG.debug("{}: Transaction {} scheduled for commit step", logContext, cohort.getIdentifier());
 834             return;
 835         }
 836
 837         LOG.debug("{}: Starting commit for transaction {}", logContext, current.getIdentifier());
 838
 839         final TransactionIdentifier txId = cohort.getIdentifier();
 840         final Payload payload;
 841         try {
 842             payload = CommitTransactionPayload.create(txId, candidate);
 843         } catch (IOException e) {
 844             LOG.error("{}: Failed to encode transaction {} candidate {}", logContext, txId, candidate, e);
 845             pendingCommits.poll().cohort.failedCommit(e);
 846             processNextPending();
 847             return;
 848         }
 849
 850         // We process next transactions pending canCommit before we call persistPayload to possibly progress subsequent
 851         // transactions to the COMMIT_PENDING state so the payloads can be batched for replication. This is done for
 852         // single-shard transactions that immediately transition from canCommit to preCommit to commit. Note that
 853         // if the next pending transaction is progressed to COMMIT_PENDING and this method (startCommit) is called,
 854         // the next transaction will not attempt to replicate b/c the current transaction is still at the head of the
 855         // pendingCommits queue.
 856         processNextPendingTransaction();
 857
 858         // After processing next pending transactions, we can now remove the current transaction from pendingCommits.
 859         // Note this must be done before the call to peekNextPendingCommit below so we check the next transaction
 860         // in order to properly determine the batchHint flag for the call to persistPayload.
 861         pendingCommits.remove();
 862         pendingFinishCommits.add(entry);
 863
 864         // See if the next transaction is pending commit (ie in the COMMIT_PENDING state) so it can be batched with
 865         // this transaction for replication.
 866         boolean replicationBatchHint = peekNextPendingCommit();
 867
 868         // Once completed, we will continue via payloadReplicationComplete
 869         shard.persistPayload(txId, payload, replicationBatchHint);
 870
 871         entry.lastAccess = shard.ticker().read();
 872
 873         LOG.debug("{}: Transaction {} submitted to persistence", logContext, txId);
 874
 875         // Process the next transaction pending commit, if any. If there is one it will be batched with this
 876         // transaction for replication.
 877         processNextPendingCommit();
 878     }
 879
 880     Collection<ActorRef> getCohortActors() {
 881         return cohortRegistry.getCohortActors();
 882     }
 883
 884     void processCohortRegistryCommand(final ActorRef sender, final CohortRegistryCommand message) {
 885         cohortRegistry.process(sender, message);
 886     }
 887
 888     @Override
 889     ShardDataTreeCohort createReadyCohort(final TransactionIdentifier txId,
 890             final DataTreeModification modification) {
 891         SimpleShardDataTreeCohort cohort = new SimpleShardDataTreeCohort(this, modification, txId,
 892                 cohortRegistry.createCohort(schemaContext, txId, COMMIT_STEP_TIMEOUT));
 893         pendingTransactions.add(new CommitEntry(cohort, ticker().read()));
 894         return cohort;
 895     }
 896
 897     @SuppressFBWarnings(value = "DB_DUPLICATE_SWITCH_CLAUSES", justification = "See inline comments below.")
 898     void checkForExpiredTransactions(final long transactionCommitTimeoutMillis) {
 899         final long timeout = TimeUnit.MILLISECONDS.toNanos(transactionCommitTimeoutMillis);
 900         final long now = ticker().read();
 901
 902         final Queue<CommitEntry> currentQueue = !pendingFinishCommits.isEmpty() ? pendingFinishCommits :
 903             !pendingCommits.isEmpty() ? pendingCommits : pendingTransactions;
 904         final CommitEntry currentTx = currentQueue.peek();
 905         if (currentTx != null && currentTx.lastAccess + timeout < now) {
 906             LOG.warn("{}: Current transaction {} has timed out after {} ms in state {}", logContext,
 907                     currentTx.cohort.getIdentifier(), transactionCommitTimeoutMillis, currentTx.cohort.getState());
 908             boolean processNext = true;
 909             switch (currentTx.cohort.getState()) {
 910                 case CAN_COMMIT_PENDING:
 911                     currentQueue.remove().cohort.failedCanCommit(new TimeoutException());
 912                     break;
 913                 case CAN_COMMIT_COMPLETE:
 914                     // The suppression of the FindBugs "DB_DUPLICATE_SWITCH_CLAUSES" warning pertains to this clause
 915                     // whose code is duplicated with PRE_COMMIT_COMPLETE. The clauses aren't combined in case the code
 916                     // in PRE_COMMIT_COMPLETE is changed.
 917                     currentQueue.remove().cohort.reportFailure(new TimeoutException());
 918                     break;
 919                 case PRE_COMMIT_PENDING:
 920                     currentQueue.remove().cohort.failedPreCommit(new TimeoutException());
 921                     break;
 922                 case PRE_COMMIT_COMPLETE:
 923                     // FIXME: this is a legacy behavior problem. Three-phase commit protocol specifies that after we
 924                     //        are ready we should commit the transaction, not abort it. Our current software stack does
 925                     //        not allow us to do that consistently, because we persist at the time of commit, hence
 926                     //        we can end up in a state where we have pre-committed a transaction, then a leader failover
 927                     //        occurred ... the new leader does not see the pre-committed transaction and does not have
 928                     //        a running timer. To fix this we really need two persistence events.
 929                     //
 930                     //        The first one, done at pre-commit time will hold the transaction payload. When consensus
 931                     //        is reached, we exit the pre-commit phase and start the pre-commit timer. Followers do not
 932                     //        apply the state in this event.
 933                     //
 934                     //        The second one, done at commit (or abort) time holds only the transaction identifier and
 935                     //        signals to followers that the state should (or should not) be applied.
 936                     //
 937                     //        In order to make the pre-commit timer working across failovers, though, we need
 938                     //        a per-shard cluster-wide monotonic time, so a follower becoming the leader can accurately
 939                     //        restart the timer.
 940                     currentQueue.remove().cohort.reportFailure(new TimeoutException());
 941                     break;
 942                 case COMMIT_PENDING:
 943                     LOG.warn("{}: Transaction {} is still committing, cannot abort", logContext,
 944                         currentTx.cohort.getIdentifier());
 945                     currentTx.lastAccess = now;
 946                     processNext = false;
 947                     return;
 948                 case ABORTED:
 949                 case COMMITTED:
 950                 case FAILED:
 951                 case READY:
 952                 default:
 953                     currentQueue.remove();
 954             }
 955
 956             if (processNext) {
 957                 processNextPending();
 958             }
 959         }
 960     }
 961
 962     boolean startAbort(final SimpleShardDataTreeCohort cohort) {
 963         final Iterator<CommitEntry> it = Iterables.concat(pendingFinishCommits, pendingCommits,
 964                 pendingTransactions).iterator();
 965         if (!it.hasNext()) {
 966             LOG.debug("{}: no open transaction while attempting to abort {}", logContext, cohort.getIdentifier());
 967             return true;
 968         }
 969
 970         // First entry is special, as it may already be committing
 971         final CommitEntry first = it.next();
 972         if (cohort.equals(first.cohort)) {
 973             if (cohort.getState() != State.COMMIT_PENDING) {
 974                 LOG.debug("{}: aborting head of queue {} in state {}", logContext, cohort.getIdentifier(),
 975                     cohort.getIdentifier());
 976
 977                 it.remove();
 978                 if (cohort.getCandidate() != null) {
 979                     rebaseTransactions(it, dataTree);
 980                 }
 981
 982                 processNextPending();
 983                 return true;
 984             }
 985
 986             LOG.warn("{}: transaction {} is committing, skipping abort", logContext, cohort.getIdentifier());
 987             return false;
 988         }
 989
 990         TipProducingDataTreeTip newTip = MoreObjects.firstNonNull(first.cohort.getCandidate(), dataTree);
 991         while (it.hasNext()) {
 992             final CommitEntry e = it.next();
 993             if (cohort.equals(e.cohort)) {
 994                 LOG.debug("{}: aborting queued transaction {}", logContext, cohort.getIdentifier());
 995
 996                 it.remove();
 997                 if (cohort.getCandidate() != null) {
 998                     rebaseTransactions(it, newTip);
 999                 }
1000
1001                 return true;
1002             } else {
1003                 newTip = MoreObjects.firstNonNull(e.cohort.getCandidate(), newTip);
1004             }
1005         }
1006
1007         LOG.debug("{}: aborted transaction {} not found in the queue", logContext, cohort.getIdentifier());
1008         return true;
1009     }
1010
1011     @SuppressWarnings("checkstyle:IllegalCatch")
1012     private void rebaseTransactions(final Iterator<CommitEntry> iter, @Nonnull final TipProducingDataTreeTip newTip) {
1013         tip = Preconditions.checkNotNull(newTip);
1014         while (iter.hasNext()) {
1015             final SimpleShardDataTreeCohort cohort = iter.next().cohort;
1016             if (cohort.getState() == State.CAN_COMMIT_COMPLETE) {
1017                 LOG.debug("{}: Revalidating queued transaction {}", logContext, cohort.getIdentifier());
1018
1019                 try {
1020                     tip.validate(cohort.getDataTreeModification());
1021                 } catch (DataValidationFailedException | RuntimeException e) {
1022                     LOG.debug("{}: Failed to revalidate queued transaction {}", logContext, cohort.getIdentifier(), e);
1023                     cohort.reportFailure(e);
1024                 }
1025             } else if (cohort.getState() == State.PRE_COMMIT_COMPLETE) {
1026                 LOG.debug("{}: Repreparing queued transaction {}", logContext, cohort.getIdentifier());
1027
1028                 try {
1029                     tip.validate(cohort.getDataTreeModification());
1030                     DataTreeCandidateTip candidate = tip.prepare(cohort.getDataTreeModification());
1031                     cohort.userPreCommit(candidate);
1032
1033                     cohort.setNewCandidate(candidate);
1034                     tip = candidate;
1035                 } catch (ExecutionException | TimeoutException | RuntimeException | DataValidationFailedException e) {
1036                     LOG.debug("{}: Failed to reprepare queued transaction {}", logContext, cohort.getIdentifier(), e);
1037                     cohort.reportFailure(e);
1038                 }
1039             }
1040         }
1041     }
1042
1043     void setRunOnPendingTransactionsComplete(final Runnable operation) {
1044         runOnPendingTransactionsComplete = operation;
1045         maybeRunOperationOnPendingTransactionsComplete();
1046     }
1047
1048     private void maybeRunOperationOnPendingTransactionsComplete() {
1049         if (runOnPendingTransactionsComplete != null && !anyPendingTransactions()) {
1050             LOG.debug("{}: Pending transactions complete - running operation {}", logContext,
1051                     runOnPendingTransactionsComplete);
1052
1053             runOnPendingTransactionsComplete.run();
1054             runOnPendingTransactionsComplete = null;
1055         }
1056     }
1057 }