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.Optional;
  14 import com.google.common.base.Preconditions;
  15 import com.google.common.base.Stopwatch;
  16 import com.google.common.base.Ticker;
  17 import com.google.common.base.Verify;
  18 import com.google.common.collect.ImmutableList;
  19 import com.google.common.collect.ImmutableMap;
  20 import com.google.common.collect.ImmutableMap.Builder;
  21 import com.google.common.primitives.UnsignedLong;
  22 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  23 import java.io.File;
  24 import java.io.IOException;
  25 import java.util.AbstractMap.SimpleEntry;
  26 import java.util.ArrayDeque;
  27 import java.util.ArrayList;
  28 import java.util.Collection;
  29 import java.util.HashMap;
  30 import java.util.Iterator;
  31 import java.util.Map;
  32 import java.util.Map.Entry;
  33 import java.util.Queue;
  34 import java.util.concurrent.ExecutionException;
  35 import java.util.concurrent.TimeUnit;
  36 import java.util.concurrent.TimeoutException;
  37 import java.util.function.UnaryOperator;
  38 import javax.annotation.Nonnull;
  39 import javax.annotation.concurrent.NotThreadSafe;
  40 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  41 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  42 import org.opendaylight.controller.cluster.datastore.DataTreeCohortActorRegistry.CohortRegistryCommand;
  43 import org.opendaylight.controller.cluster.datastore.ShardDataTreeCohort.State;
  44 import org.opendaylight.controller.cluster.datastore.persisted.CommitTransactionPayload;
  45 import org.opendaylight.controller.cluster.datastore.persisted.MetadataShardDataTreeSnapshot;
  46 import org.opendaylight.controller.cluster.datastore.persisted.ShardDataTreeSnapshot;
  47 import org.opendaylight.controller.cluster.datastore.persisted.ShardDataTreeSnapshotMetadata;
  48 import org.opendaylight.controller.cluster.datastore.utils.DataTreeModificationOutput;
  49 import org.opendaylight.controller.cluster.datastore.utils.PruningDataTreeModification;
  50 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  51 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataBroker.DataChangeScope;
  52 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
  53 import org.opendaylight.controller.md.sal.common.api.data.OptimisticLockFailedException;
  54 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
  55 import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeChangeListener;
  56 import org.opendaylight.controller.md.sal.dom.store.impl.DataChangeListenerRegistration;
  57 import org.opendaylight.yangtools.concepts.Identifier;
  58 import org.opendaylight.yangtools.concepts.ListenerRegistration;
  59 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  60 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  61 import org.opendaylight.yangtools.yang.data.api.schema.tree.ConflictingModificationAppliedException;
  62 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
  63 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateTip;
  64 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidates;
  65 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
  66 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeSnapshot;
  67 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
  68 import org.opendaylight.yangtools.yang.data.api.schema.tree.ModificationType;
  69 import org.opendaylight.yangtools.yang.data.api.schema.tree.TipProducingDataTree;
  70 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
  71 import org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTreeFactory;
  72 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  73 import org.slf4j.Logger;
  74 import org.slf4j.LoggerFactory;
  75 import scala.concurrent.duration.Duration;
  76
  77 /**
  78  * Internal shard state, similar to a DOMStore, but optimized for use in the actor system,
  79  * e.g. it does not expose public interfaces and assumes it is only ever called from a
  80  * single thread.
  81  *
  82  * <p>
  83  * This class is not part of the API contract and is subject to change at any time.
  84  */
  85 @NotThreadSafe
  86 public class ShardDataTree extends ShardDataTreeTransactionParent {
  87     private static final class CommitEntry {
  88         final SimpleShardDataTreeCohort cohort;
  89         long lastAccess;
  90
  91         CommitEntry(final SimpleShardDataTreeCohort cohort, final long now) {
  92             this.cohort = Preconditions.checkNotNull(cohort);
  93             lastAccess = now;
  94         }
  95     }
  96
  97     private static final Timeout COMMIT_STEP_TIMEOUT = new Timeout(Duration.create(5, TimeUnit.SECONDS));
  98     private static final Logger LOG = LoggerFactory.getLogger(ShardDataTree.class);
  99
 100     private final Map<LocalHistoryIdentifier, ShardDataTreeTransactionChain> transactionChains = new HashMap<>();
 101     private final DataTreeCohortActorRegistry cohortRegistry = new DataTreeCohortActorRegistry();
 102     private final Queue<CommitEntry> pendingTransactions = new ArrayDeque<>();
 103     private final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher;
 104     private final ShardDataChangeListenerPublisher dataChangeListenerPublisher;
 105     private final Collection<ShardDataTreeMetadata<?>> metadata;
 106     private final TipProducingDataTree dataTree;
 107     private final String logContext;
 108     private final Shard shard;
 109     private Runnable runOnPendingTransactionsComplete;
 110
 111     private SchemaContext schemaContext;
 112
 113     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TipProducingDataTree dataTree,
 114             final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher,
 115             final ShardDataChangeListenerPublisher dataChangeListenerPublisher, final String logContext,
 116             final ShardDataTreeMetadata<?>... metadata) {
 117         this.dataTree = Preconditions.checkNotNull(dataTree);
 118         updateSchemaContext(schemaContext);
 119
 120         this.shard = Preconditions.checkNotNull(shard);
 121         this.treeChangeListenerPublisher = Preconditions.checkNotNull(treeChangeListenerPublisher);
 122         this.dataChangeListenerPublisher = Preconditions.checkNotNull(dataChangeListenerPublisher);
 123         this.logContext = Preconditions.checkNotNull(logContext);
 124         this.metadata = ImmutableList.copyOf(metadata);
 125     }
 126
 127     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TreeType treeType,
 128             final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher,
 129             final ShardDataChangeListenerPublisher dataChangeListenerPublisher, final String logContext) {
 130         this(shard, schemaContext, InMemoryDataTreeFactory.getInstance().create(treeType),
 131                 treeChangeListenerPublisher, dataChangeListenerPublisher, logContext);
 132     }
 133
 134     @VisibleForTesting
 135     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TreeType treeType) {
 136         this(shard, schemaContext, treeType, new DefaultShardDataTreeChangeListenerPublisher(),
 137                 new DefaultShardDataChangeListenerPublisher(), "");
 138     }
 139
 140     final String logContext() {
 141         return logContext;
 142     }
 143
 144     final Ticker ticker() {
 145         return shard.ticker();
 146     }
 147
 148     public TipProducingDataTree getDataTree() {
 149         return dataTree;
 150     }
 151
 152     SchemaContext getSchemaContext() {
 153         return schemaContext;
 154     }
 155
 156     void updateSchemaContext(final SchemaContext newSchemaContext) {
 157         dataTree.setSchemaContext(newSchemaContext);
 158         this.schemaContext = Preconditions.checkNotNull(newSchemaContext);
 159     }
 160
 161     /**
 162      * Take a snapshot of current state for later recovery.
 163      *
 164      * @return A state snapshot
 165      */
 166     @Nonnull ShardDataTreeSnapshot takeStateSnapshot() {
 167         final NormalizedNode<?, ?> rootNode = dataTree.takeSnapshot().readNode(YangInstanceIdentifier.EMPTY).get();
 168         final Builder<Class<? extends ShardDataTreeSnapshotMetadata<?>>, ShardDataTreeSnapshotMetadata<?>> metaBuilder =
 169                 ImmutableMap.builder();
 170
 171         for (ShardDataTreeMetadata<?> m : metadata) {
 172             final ShardDataTreeSnapshotMetadata<?> meta = m.toSnapshot();
 173             if (meta != null) {
 174                 metaBuilder.put(meta.getType(), meta);
 175             }
 176         }
 177
 178         return new MetadataShardDataTreeSnapshot(rootNode, metaBuilder.build());
 179     }
 180
 181     private void applySnapshot(@Nonnull final ShardDataTreeSnapshot snapshot,
 182             final UnaryOperator<DataTreeModification> wrapper) throws DataValidationFailedException {
 183         final Stopwatch elapsed = Stopwatch.createStarted();
 184
 185         if (!pendingTransactions.isEmpty()) {
 186             LOG.warn("{}: applying state snapshot with pending transactions", logContext);
 187         }
 188
 189         final Map<Class<? extends ShardDataTreeSnapshotMetadata<?>>, ShardDataTreeSnapshotMetadata<?>> snapshotMeta;
 190         if (snapshot instanceof MetadataShardDataTreeSnapshot) {
 191             snapshotMeta = ((MetadataShardDataTreeSnapshot) snapshot).getMetadata();
 192         } else {
 193             snapshotMeta = ImmutableMap.of();
 194         }
 195
 196         for (ShardDataTreeMetadata<?> m : metadata) {
 197             final ShardDataTreeSnapshotMetadata<?> s = snapshotMeta.get(m.getSupportedType());
 198             if (s != null) {
 199                 m.applySnapshot(s);
 200             } else {
 201                 m.reset();
 202             }
 203         }
 204
 205         final DataTreeModification mod = wrapper.apply(dataTree.takeSnapshot().newModification());
 206         // delete everything first
 207         mod.delete(YangInstanceIdentifier.EMPTY);
 208
 209         final java.util.Optional<NormalizedNode<?, ?>> maybeNode = snapshot.getRootNode();
 210         if (maybeNode.isPresent()) {
 211             // Add everything from the remote node back
 212             mod.write(YangInstanceIdentifier.EMPTY, maybeNode.get());
 213         }
 214         mod.ready();
 215
 216         final DataTreeModification unwrapped = unwrap(mod);
 217         dataTree.validate(unwrapped);
 218         DataTreeCandidateTip candidate = dataTree.prepare(unwrapped);
 219         dataTree.commit(candidate);
 220         notifyListeners(candidate);
 221
 222         LOG.debug("{}: state snapshot applied in %s", logContext, elapsed);
 223     }
 224
 225     /**
 226      * Apply a snapshot coming from the leader. This method assumes the leader and follower SchemaContexts match and
 227      * does not perform any pruning.
 228      *
 229      * @param snapshot Snapshot that needs to be applied
 230      * @throws DataValidationFailedException when the snapshot fails to apply
 231      */
 232     void applySnapshot(@Nonnull final ShardDataTreeSnapshot snapshot) throws DataValidationFailedException {
 233         applySnapshot(snapshot, UnaryOperator.identity());
 234     }
 235
 236     private PruningDataTreeModification wrapWithPruning(final DataTreeModification delegate) {
 237         return new PruningDataTreeModification(delegate, dataTree, schemaContext);
 238     }
 239
 240     private static DataTreeModification unwrap(final DataTreeModification modification) {
 241         if (modification instanceof PruningDataTreeModification) {
 242             return ((PruningDataTreeModification)modification).delegate();
 243         }
 244         return modification;
 245     }
 246
 247     /**
 248      * Apply a snapshot coming from recovery. This method does not assume the SchemaContexts match and performs data
 249      * pruning in an attempt to adjust the state to our current SchemaContext.
 250      *
 251      * @param snapshot Snapshot that needs to be applied
 252      * @throws DataValidationFailedException when the snapshot fails to apply
 253      */
 254     void applyRecoverySnapshot(final @Nonnull ShardDataTreeSnapshot snapshot) throws DataValidationFailedException {
 255         applySnapshot(snapshot, this::wrapWithPruning);
 256     }
 257
 258     @SuppressWarnings("checkstyle:IllegalCatch")
 259     private void applyRecoveryCandidate(final DataTreeCandidate candidate) throws DataValidationFailedException {
 260         final PruningDataTreeModification mod = wrapWithPruning(dataTree.takeSnapshot().newModification());
 261         DataTreeCandidates.applyToModification(mod, candidate);
 262         mod.ready();
 263
 264         final DataTreeModification unwrapped = mod.delegate();
 265         LOG.trace("{}: Applying recovery modification {}", logContext, unwrapped);
 266
 267         try {
 268             dataTree.validate(unwrapped);
 269             dataTree.commit(dataTree.prepare(unwrapped));
 270         } catch (Exception e) {
 271             File file = new File(System.getProperty("karaf.data", "."),
 272                     "failed-recovery-payload-" + logContext + ".out");
 273             DataTreeModificationOutput.toFile(file, unwrapped);
 274             throw new IllegalStateException(String.format(
 275                     "%s: Failed to apply recovery payload. Modification data was written to file %s",
 276                     logContext, file), e);
 277         }
 278     }
 279
 280     /**
 281      * Apply a payload coming from recovery. This method does not assume the SchemaContexts match and performs data
 282      * pruning in an attempt to adjust the state to our current SchemaContext.
 283      *
 284      * @param payload Payload
 285      * @throws IOException when the snapshot fails to deserialize
 286      * @throws DataValidationFailedException when the snapshot fails to apply
 287      */
 288     void applyRecoveryPayload(final @Nonnull Payload payload) throws IOException, DataValidationFailedException {
 289         if (payload instanceof CommitTransactionPayload) {
 290             final Entry<TransactionIdentifier, DataTreeCandidate> e =
 291                     ((CommitTransactionPayload) payload).getCandidate();
 292             applyRecoveryCandidate(e.getValue());
 293             allMetadataCommittedTransaction(e.getKey());
 294         } else if (payload instanceof DataTreeCandidatePayload) {
 295             applyRecoveryCandidate(((DataTreeCandidatePayload) payload).getCandidate());
 296         } else {
 297             LOG.debug("{}: ignoring unhandled payload {}", logContext, payload);
 298         }
 299     }
 300
 301     private void applyReplicatedCandidate(final Identifier identifier, final DataTreeCandidate foreign)
 302             throws DataValidationFailedException {
 303         LOG.debug("{}: Applying foreign transaction {}", logContext, identifier);
 304
 305         final DataTreeModification mod = dataTree.takeSnapshot().newModification();
 306         DataTreeCandidates.applyToModification(mod, foreign);
 307         mod.ready();
 308
 309         LOG.trace("{}: Applying foreign modification {}", logContext, mod);
 310         dataTree.validate(mod);
 311         final DataTreeCandidate candidate = dataTree.prepare(mod);
 312         dataTree.commit(candidate);
 313
 314         notifyListeners(candidate);
 315     }
 316
 317     /**
 318      * Apply a payload coming from the leader, which could actually be us. This method assumes the leader and follower
 319      * SchemaContexts match and does not perform any pruning.
 320      *
 321      * @param identifier Payload identifier as returned from RaftActor
 322      * @param payload Payload
 323      * @throws IOException when the snapshot fails to deserialize
 324      * @throws DataValidationFailedException when the snapshot fails to apply
 325      */
 326     void applyReplicatedPayload(final Identifier identifier, final Payload payload) throws IOException,
 327             DataValidationFailedException {
 328         /*
 329          * 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
 330          * if we are the leader and it has originated with us.
 331          *
 332          * The identifier will only ever be non-null when we were the leader which achieved consensus. Unfortunately,
 333          * though, this may not be the case anymore, as we are being called some time afterwards and we may not be
 334          * acting in that capacity anymore.
 335          *
 336          * In any case, we know that this is an entry coming from replication, hence we can be sure we will not observe
 337          * pre-Boron state -- which limits the number of options here.
 338          */
 339         if (payload instanceof CommitTransactionPayload) {
 340             if (identifier == null) {
 341                 final Entry<TransactionIdentifier, DataTreeCandidate> e =
 342                         ((CommitTransactionPayload) payload).getCandidate();
 343                 applyReplicatedCandidate(e.getKey(), e.getValue());
 344                 allMetadataCommittedTransaction(e.getKey());
 345             } else {
 346                 Verify.verify(identifier instanceof TransactionIdentifier);
 347                 payloadReplicationComplete((TransactionIdentifier) identifier);
 348             }
 349         } else {
 350             LOG.warn("{}: ignoring unhandled identifier {} payload {}", logContext, identifier, payload);
 351         }
 352     }
 353
 354     private void payloadReplicationComplete(final TransactionIdentifier txId) {
 355         final CommitEntry current = pendingTransactions.peek();
 356         if (current == null) {
 357             LOG.warn("{}: No outstanding transactions, ignoring consensus on transaction {}", logContext, txId);
 358             return;
 359         }
 360
 361         if (!current.cohort.getIdentifier().equals(txId)) {
 362             LOG.warn("{}: Head of queue is {}, ignoring consensus on transaction {}", logContext,
 363                 current.cohort.getIdentifier(), txId);
 364             return;
 365         }
 366
 367         finishCommit(current.cohort);
 368     }
 369
 370     private void allMetadataCommittedTransaction(final TransactionIdentifier txId) {
 371         for (ShardDataTreeMetadata<?> m : metadata) {
 372             m.onTransactionCommitted(txId);
 373         }
 374     }
 375
 376     ShardDataTreeTransactionChain ensureTransactionChain(final LocalHistoryIdentifier localHistoryIdentifier) {
 377         ShardDataTreeTransactionChain chain = transactionChains.get(localHistoryIdentifier);
 378         if (chain == null) {
 379             chain = new ShardDataTreeTransactionChain(localHistoryIdentifier, this);
 380             transactionChains.put(localHistoryIdentifier, chain);
 381         }
 382
 383         return chain;
 384     }
 385
 386     ReadOnlyShardDataTreeTransaction newReadOnlyTransaction(final TransactionIdentifier txId) {
 387         if (txId.getHistoryId().getHistoryId() == 0) {
 388             return new ReadOnlyShardDataTreeTransaction(txId, dataTree.takeSnapshot());
 389         }
 390
 391         return ensureTransactionChain(txId.getHistoryId()).newReadOnlyTransaction(txId);
 392     }
 393
 394     ReadWriteShardDataTreeTransaction newReadWriteTransaction(final TransactionIdentifier txId) {
 395         if (txId.getHistoryId().getHistoryId() == 0) {
 396             return new ReadWriteShardDataTreeTransaction(ShardDataTree.this, txId, dataTree.takeSnapshot()
 397                     .newModification());
 398         }
 399
 400         return ensureTransactionChain(txId.getHistoryId()).newReadWriteTransaction(txId);
 401     }
 402
 403     @VisibleForTesting
 404     public void notifyListeners(final DataTreeCandidate candidate) {
 405         treeChangeListenerPublisher.publishChanges(candidate, logContext);
 406         dataChangeListenerPublisher.publishChanges(candidate, logContext);
 407     }
 408
 409     void notifyOfInitialData(final DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
 410             NormalizedNode<?, ?>>> listenerReg, final Optional<DataTreeCandidate> currentState) {
 411         if (currentState.isPresent()) {
 412             ShardDataChangeListenerPublisher localPublisher = dataChangeListenerPublisher.newInstance();
 413             localPublisher.registerDataChangeListener(listenerReg.getPath(), listenerReg.getInstance(),
 414                     listenerReg.getScope());
 415             localPublisher.publishChanges(currentState.get(), logContext);
 416         }
 417     }
 418
 419     void notifyOfInitialData(final YangInstanceIdentifier path, final DOMDataTreeChangeListener listener,
 420             final Optional<DataTreeCandidate> currentState) {
 421         if (currentState.isPresent()) {
 422             ShardDataTreeChangeListenerPublisher localPublisher = treeChangeListenerPublisher.newInstance();
 423             localPublisher.registerTreeChangeListener(path, listener);
 424             localPublisher.publishChanges(currentState.get(), logContext);
 425         }
 426     }
 427
 428     void closeAllTransactionChains() {
 429         for (ShardDataTreeTransactionChain chain : transactionChains.values()) {
 430             chain.close();
 431         }
 432
 433         transactionChains.clear();
 434     }
 435
 436     void closeTransactionChain(final LocalHistoryIdentifier transactionChainId) {
 437         final ShardDataTreeTransactionChain chain = transactionChains.remove(transactionChainId);
 438         if (chain != null) {
 439             chain.close();
 440         } else {
 441             LOG.debug("{}: Closing non-existent transaction chain {}", logContext, transactionChainId);
 442         }
 443     }
 444
 445     Entry<DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>>,
 446             Optional<DataTreeCandidate>> registerChangeListener(final YangInstanceIdentifier path,
 447                     final AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> listener,
 448                     final DataChangeScope scope) {
 449         DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>> reg =
 450                 dataChangeListenerPublisher.registerDataChangeListener(path, listener, scope);
 451
 452         return new SimpleEntry<>(reg, readCurrentData());
 453     }
 454
 455     private Optional<DataTreeCandidate> readCurrentData() {
 456         final Optional<NormalizedNode<?, ?>> currentState =
 457                 dataTree.takeSnapshot().readNode(YangInstanceIdentifier.EMPTY);
 458         return currentState.isPresent() ? Optional.of(DataTreeCandidates.fromNormalizedNode(
 459             YangInstanceIdentifier.EMPTY, currentState.get())) : Optional.<DataTreeCandidate>absent();
 460     }
 461
 462     public Entry<ListenerRegistration<DOMDataTreeChangeListener>, Optional<DataTreeCandidate>>
 463             registerTreeChangeListener(final YangInstanceIdentifier path, final DOMDataTreeChangeListener listener) {
 464         final ListenerRegistration<DOMDataTreeChangeListener> reg =
 465                 treeChangeListenerPublisher.registerTreeChangeListener(path, listener);
 466
 467         return new SimpleEntry<>(reg, readCurrentData());
 468     }
 469
 470     int getQueueSize() {
 471         return pendingTransactions.size();
 472     }
 473
 474     @Override
 475     void abortTransaction(final AbstractShardDataTreeTransaction<?> transaction) {
 476         // Intentional no-op
 477     }
 478
 479     @Override
 480     ShardDataTreeCohort finishTransaction(final ReadWriteShardDataTreeTransaction transaction) {
 481         final DataTreeModification snapshot = transaction.getSnapshot();
 482         snapshot.ready();
 483
 484         return createReadyCohort(transaction.getIdentifier(), snapshot);
 485     }
 486
 487     public Optional<NormalizedNode<?, ?>> readNode(final YangInstanceIdentifier path) {
 488         return dataTree.takeSnapshot().readNode(path);
 489     }
 490
 491     DataTreeSnapshot takeSnapshot() {
 492         return dataTree.takeSnapshot();
 493     }
 494
 495     @VisibleForTesting
 496     public DataTreeModification newModification() {
 497         return dataTree.takeSnapshot().newModification();
 498     }
 499
 500     /**
 501      * Commits a modification.
 502      *
 503      * @deprecated This method violates DataTree containment and will be removed.
 504      */
 505     @VisibleForTesting
 506     @Deprecated
 507     public DataTreeCandidate commit(final DataTreeModification modification) throws DataValidationFailedException {
 508         modification.ready();
 509         dataTree.validate(modification);
 510         DataTreeCandidate candidate = dataTree.prepare(modification);
 511         dataTree.commit(candidate);
 512         return candidate;
 513     }
 514
 515     public Collection<ShardDataTreeCohort> getAndClearPendingTransactions() {
 516         Collection<ShardDataTreeCohort> ret = new ArrayList<>(pendingTransactions.size());
 517         for (CommitEntry entry: pendingTransactions) {
 518             ret.add(entry.cohort);
 519         }
 520
 521         pendingTransactions.clear();
 522         return ret;
 523     }
 524
 525     @SuppressWarnings("checkstyle:IllegalCatch")
 526     private void processNextTransaction() {
 527         while (!pendingTransactions.isEmpty()) {
 528             final CommitEntry entry = pendingTransactions.peek();
 529             final SimpleShardDataTreeCohort cohort = entry.cohort;
 530             final DataTreeModification modification = cohort.getDataTreeModification();
 531
 532             if (cohort.getState() != State.CAN_COMMIT_PENDING) {
 533                 break;
 534             }
 535
 536             LOG.debug("{}: Validating transaction {}", logContext, cohort.getIdentifier());
 537             Exception cause;
 538             try {
 539                 dataTree.validate(modification);
 540                 LOG.debug("{}: Transaction {} validated", logContext, cohort.getIdentifier());
 541                 cohort.successfulCanCommit();
 542                 entry.lastAccess = shard.ticker().read();
 543                 return;
 544             } catch (ConflictingModificationAppliedException e) {
 545                 LOG.warn("{}: Store Tx {}: Conflicting modification for path {}.", logContext, cohort.getIdentifier(),
 546                     e.getPath());
 547                 cause = new OptimisticLockFailedException("Optimistic lock failed.", e);
 548             } catch (DataValidationFailedException e) {
 549                 LOG.warn("{}: Store Tx {}: Data validation failed for path {}.", logContext, cohort.getIdentifier(),
 550                     e.getPath(), e);
 551
 552                 // For debugging purposes, allow dumping of the modification. Coupled with the above
 553                 // precondition log, it should allow us to understand what went on.
 554                 LOG.debug("{}: Store Tx {}: modifications: {} tree: {}", cohort.getIdentifier(), modification,
 555                         dataTree);
 556                 cause = new TransactionCommitFailedException("Data did not pass validation.", e);
 557             } catch (Exception e) {
 558                 LOG.warn("{}: Unexpected failure in validation phase", logContext, e);
 559                 cause = e;
 560             }
 561
 562             // Failure path: propagate the failure, remove the transaction from the queue and loop to the next one
 563             pendingTransactions.poll().cohort.failedCanCommit(cause);
 564         }
 565
 566         maybeRunOperationOnPendingTransactionsComplete();
 567     }
 568
 569     void startCanCommit(final SimpleShardDataTreeCohort cohort) {
 570         final SimpleShardDataTreeCohort current = pendingTransactions.peek().cohort;
 571         if (!cohort.equals(current)) {
 572             LOG.debug("{}: Transaction {} scheduled for canCommit step", logContext, cohort.getIdentifier());
 573             return;
 574         }
 575
 576         processNextTransaction();
 577     }
 578
 579     private void failPreCommit(final Exception cause) {
 580         shard.getShardMBean().incrementFailedTransactionsCount();
 581         pendingTransactions.poll().cohort.failedPreCommit(cause);
 582         processNextTransaction();
 583     }
 584
 585     @SuppressWarnings("checkstyle:IllegalCatch")
 586     void startPreCommit(final SimpleShardDataTreeCohort cohort) {
 587         final CommitEntry entry = pendingTransactions.peek();
 588         Preconditions.checkState(entry != null, "Attempted to pre-commit of %s when no transactions pending", cohort);
 589
 590         final SimpleShardDataTreeCohort current = entry.cohort;
 591         Verify.verify(cohort.equals(current), "Attempted to pre-commit %s while %s is pending", cohort, current);
 592         final DataTreeCandidateTip candidate;
 593         try {
 594             candidate = dataTree.prepare(cohort.getDataTreeModification());
 595         } catch (Exception e) {
 596             failPreCommit(e);
 597             return;
 598         }
 599
 600         try {
 601             cohort.userPreCommit(candidate);
 602         } catch (ExecutionException | TimeoutException e) {
 603             failPreCommit(e);
 604             return;
 605         }
 606
 607         entry.lastAccess = shard.ticker().read();
 608         cohort.successfulPreCommit(candidate);
 609     }
 610
 611     private void failCommit(final Exception cause) {
 612         shard.getShardMBean().incrementFailedTransactionsCount();
 613         pendingTransactions.poll().cohort.failedCommit(cause);
 614         processNextTransaction();
 615     }
 616
 617     @SuppressWarnings("checkstyle:IllegalCatch")
 618     private void finishCommit(final SimpleShardDataTreeCohort cohort) {
 619         final TransactionIdentifier txId = cohort.getIdentifier();
 620         final DataTreeCandidate candidate = cohort.getCandidate();
 621
 622         LOG.debug("{}: Resuming commit of transaction {}", logContext, txId);
 623
 624         try {
 625             dataTree.commit(candidate);
 626         } catch (Exception e) {
 627             LOG.error("{}: Failed to commit transaction {}", logContext, txId, e);
 628             failCommit(e);
 629             return;
 630         }
 631
 632         shard.getShardMBean().incrementCommittedTransactionCount();
 633         shard.getShardMBean().setLastCommittedTransactionTime(System.currentTimeMillis());
 634
 635         // FIXME: propagate journal index
 636         pendingTransactions.poll().cohort.successfulCommit(UnsignedLong.ZERO);
 637
 638         LOG.trace("{}: Transaction {} committed, proceeding to notify", logContext, txId);
 639         notifyListeners(candidate);
 640
 641         processNextTransaction();
 642     }
 643
 644     void startCommit(final SimpleShardDataTreeCohort cohort, final DataTreeCandidate candidate) {
 645         final CommitEntry entry = pendingTransactions.peek();
 646         Preconditions.checkState(entry != null, "Attempted to start commit of %s when no transactions pending", cohort);
 647
 648         final SimpleShardDataTreeCohort current = entry.cohort;
 649         Verify.verify(cohort.equals(current), "Attempted to commit %s while %s is pending", cohort, current);
 650
 651         if (shard.canSkipPayload() || candidate.getRootNode().getModificationType() == ModificationType.UNMODIFIED) {
 652             LOG.debug("{}: No replication required, proceeding to finish commit", logContext);
 653             finishCommit(cohort);
 654             return;
 655         }
 656
 657         final TransactionIdentifier txId = cohort.getIdentifier();
 658         final Payload payload;
 659         try {
 660             payload = CommitTransactionPayload.create(txId, candidate);
 661         } catch (IOException e) {
 662             LOG.error("{}: Failed to encode transaction {} candidate {}", logContext, txId, candidate, e);
 663             pendingTransactions.poll().cohort.failedCommit(e);
 664             return;
 665         }
 666
 667         // Once completed, we will continue via payloadReplicationComplete
 668         entry.lastAccess = shard.ticker().read();
 669         shard.persistPayload(txId, payload);
 670         LOG.debug("{}: Transaction {} submitted to persistence", logContext, txId);
 671     }
 672
 673     void processCohortRegistryCommand(final ActorRef sender, final CohortRegistryCommand message) {
 674         cohortRegistry.process(sender, message);
 675     }
 676
 677     @Override
 678     ShardDataTreeCohort createReadyCohort(final TransactionIdentifier txId,
 679             final DataTreeModification modification) {
 680         SimpleShardDataTreeCohort cohort = new SimpleShardDataTreeCohort(this, modification, txId,
 681                 cohortRegistry.createCohort(schemaContext, txId, COMMIT_STEP_TIMEOUT));
 682         pendingTransactions.add(new CommitEntry(cohort, shard.ticker().read()));
 683         return cohort;
 684     }
 685
 686     @SuppressFBWarnings(value = {"RV_RETURN_VALUE_IGNORED", "DB_DUPLICATE_SWITCH_CLAUSES"},
 687             justification = "See inline comments below.")
 688     void checkForExpiredTransactions(final long transactionCommitTimeoutMillis) {
 689         final long timeout = TimeUnit.MILLISECONDS.toNanos(transactionCommitTimeoutMillis);
 690         final long now = shard.ticker().read();
 691         final CommitEntry currentTx = pendingTransactions.peek();
 692         if (currentTx != null && currentTx.lastAccess + timeout < now) {
 693             LOG.warn("{}: Current transaction {} has timed out after {} ms in state {}", logContext,
 694                     currentTx.cohort.getIdentifier(), transactionCommitTimeoutMillis, currentTx.cohort.getState());
 695             boolean processNext = true;
 696             switch (currentTx.cohort.getState()) {
 697                 case CAN_COMMIT_PENDING:
 698                     pendingTransactions.poll().cohort.failedCanCommit(new TimeoutException());
 699                     break;
 700                 case CAN_COMMIT_COMPLETE:
 701                     // The suppression of the FindBugs "DB_DUPLICATE_SWITCH_CLAUSES" warning pertains to this clause
 702                     // whose code is duplicated with PRE_COMMIT_COMPLETE. The clauses aren't combined in case the code
 703                     // in PRE_COMMIT_COMPLETE is changed.
 704                     pendingTransactions.poll().cohort.reportFailure(new TimeoutException());
 705                     break;
 706                 case PRE_COMMIT_PENDING:
 707                     pendingTransactions.poll().cohort.failedPreCommit(new TimeoutException());
 708                     break;
 709                 case PRE_COMMIT_COMPLETE:
 710                     // FIXME: this is a legacy behavior problem. Three-phase commit protocol specifies that after we
 711                     //        are ready we should commit the transaction, not abort it. Our current software stack does
 712                     //        not allow us to do that consistently, because we persist at the time of commit, hence
 713                     //        we can end up in a state where we have pre-committed a transaction, then a leader failover
 714                     //        occurred ... the new leader does not see the pre-committed transaction and does not have
 715                     //        a running timer. To fix this we really need two persistence events.
 716                     //
 717                     //        The first one, done at pre-commit time will hold the transaction payload. When consensus
 718                     //        is reached, we exit the pre-commit phase and start the pre-commit timer. Followers do not
 719                     //        apply the state in this event.
 720                     //
 721                     //        The second one, done at commit (or abort) time holds only the transaction identifier and
 722                     //        signals to followers that the state should (or should not) be applied.
 723                     //
 724                     //        In order to make the pre-commit timer working across failovers, though, we need
 725                     //        a per-shard cluster-wide monotonic time, so a follower becoming the leader can accurately
 726                     //        restart the timer.
 727                     pendingTransactions.poll().cohort.reportFailure(new TimeoutException());
 728                     break;
 729                 case COMMIT_PENDING:
 730                     LOG.warn("{}: Transaction {} is still committing, cannot abort", logContext,
 731                         currentTx.cohort.getIdentifier());
 732                     currentTx.lastAccess = now;
 733                     processNext = false;
 734                     return;
 735                 case ABORTED:
 736                 case COMMITTED:
 737                 case FAILED:
 738                 case READY:
 739                 default:
 740                     // The suppression of the FindBugs "RV_RETURN_VALUE_IGNORED" warning pertains to this line. In
 741                     // this case, we just want to drop the current entry that expired and thus ignore the return value.
 742                     // In fact we really shouldn't hit this case but we handle all enums for completeness.
 743                     pendingTransactions.poll();
 744             }
 745
 746             if (processNext) {
 747                 processNextTransaction();
 748             }
 749         }
 750     }
 751
 752     @SuppressFBWarnings(value = "RV_RETURN_VALUE_IGNORED", justification = "See inline comment below.")
 753     void startAbort(final SimpleShardDataTreeCohort cohort) {
 754         final Iterator<CommitEntry> it = pendingTransactions.iterator();
 755         if (!it.hasNext()) {
 756             LOG.debug("{}: no open transaction while attempting to abort {}", logContext, cohort.getIdentifier());
 757             return;
 758         }
 759
 760         // First entry is special, as it may already be committing
 761         final CommitEntry first = it.next();
 762         if (cohort.equals(first.cohort)) {
 763             if (cohort.getState() != State.COMMIT_PENDING) {
 764                 LOG.debug("{}: aborted head of queue {} in state {}", logContext, cohort.getIdentifier(),
 765                     cohort.getIdentifier());
 766
 767                 // The suppression of the FindBugs "RV_RETURN_VALUE_IGNORED" warning pertains to this line. In
 768                 // this case, we've already obtained the head of the queue above via the Iterator and we just want to
 769                 // remove it here.
 770                 pendingTransactions.poll();
 771                 processNextTransaction();
 772             } else {
 773                 LOG.warn("{}: transaction {} is committing, skipping abort", logContext, cohort.getIdentifier());
 774             }
 775
 776             return;
 777         }
 778
 779         while (it.hasNext()) {
 780             final CommitEntry e = it.next();
 781             if (cohort.equals(e.cohort)) {
 782                 LOG.debug("{}: aborting queued transaction {}", logContext, cohort.getIdentifier());
 783                 it.remove();
 784                 return;
 785             }
 786         }
 787
 788         LOG.debug("{}: aborted transaction {} not found in the queue", logContext, cohort.getIdentifier());
 789     }
 790
 791     void setRunOnPendingTransactionsComplete(final Runnable operation) {
 792         runOnPendingTransactionsComplete = operation;
 793         maybeRunOperationOnPendingTransactionsComplete();
 794     }
 795
 796     private void maybeRunOperationOnPendingTransactionsComplete() {
 797         if (runOnPendingTransactionsComplete != null && pendingTransactions.isEmpty()) {
 798             LOG.debug("{}: Pending transactions complete - running operation {}", logContext,
 799                     runOnPendingTransactionsComplete);
 800
 801             runOnPendingTransactionsComplete.run();
 802             runOnPendingTransactionsComplete = null;
 803         }
 804     }
 805 }