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

   1 /*
   2  * Copyright (c) 2014 Brocade Communications Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.cluster.datastore;
   9
  10 import akka.actor.ActorRef;
  11 import akka.actor.Status;
  12 import akka.serialization.Serialization;
  13 import com.google.common.annotations.VisibleForTesting;
  14 import com.google.common.base.Preconditions;
  15 import com.google.common.base.Stopwatch;
  16 import java.util.HashMap;
  17 import java.util.Iterator;
  18 import java.util.LinkedList;
  19 import java.util.Map;
  20 import java.util.Queue;
  21 import java.util.concurrent.ExecutionException;
  22 import java.util.concurrent.TimeUnit;
  23 import org.opendaylight.controller.cluster.datastore.compat.BackwardsCompatibleThreePhaseCommitCohort;
  24 import org.opendaylight.controller.cluster.datastore.messages.AbortTransactionReply;
  25 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  26 import org.opendaylight.controller.cluster.datastore.messages.BatchedModificationsReply;
  27 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransactionReply;
  28 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  29 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  30 import org.opendaylight.controller.cluster.datastore.messages.ReadyTransactionReply;
  31 import org.opendaylight.controller.cluster.datastore.modification.Modification;
  32 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
  33 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
  34 import org.slf4j.Logger;
  35
  36 /**
  37  * Coordinates commits for a shard ensuring only one concurrent 3-phase commit.
  38  *
  39  * @author Thomas Pantelis
  40  */
  41 class ShardCommitCoordinator {
  42
  43     // Interface hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
  44     public interface CohortDecorator {
  45         ShardDataTreeCohort decorate(String transactionID, ShardDataTreeCohort actual);
  46     }
  47
  48     private final Map<String, CohortEntry> cohortCache = new HashMap<>();
  49
  50     private CohortEntry currentCohortEntry;
  51
  52     private final ShardDataTree dataTree;
  53
  54     // We use a LinkedList here to avoid synchronization overhead with concurrent queue impls
  55     // since this should only be accessed on the shard's dispatcher.
  56     private final Queue<CohortEntry> queuedCohortEntries = new LinkedList<>();
  57
  58     private int queueCapacity;
  59
  60     private final Logger log;
  61
  62     private final String name;
  63
  64     private final long cacheExpiryTimeoutInMillis;
  65
  66     // This is a hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
  67     private CohortDecorator cohortDecorator;
  68
  69     private ReadyTransactionReply readyTransactionReply;
  70
  71     ShardCommitCoordinator(ShardDataTree dataTree,
  72             long cacheExpiryTimeoutInMillis, int queueCapacity, Logger log, String name) {
  73
  74         this.queueCapacity = queueCapacity;
  75         this.log = log;
  76         this.name = name;
  77         this.dataTree = Preconditions.checkNotNull(dataTree);
  78         this.cacheExpiryTimeoutInMillis = cacheExpiryTimeoutInMillis;
  79     }
  80
  81     int getQueueSize() {
  82         return queuedCohortEntries.size();
  83     }
  84
  85     void setQueueCapacity(int queueCapacity) {
  86         this.queueCapacity = queueCapacity;
  87     }
  88
  89     private ReadyTransactionReply readyTransactionReply(Shard shard) {
  90         if(readyTransactionReply == null) {
  91             readyTransactionReply = new ReadyTransactionReply(Serialization.serializedActorPath(shard.self()));
  92         }
  93
  94         return readyTransactionReply;
  95     }
  96
  97     private boolean queueCohortEntry(CohortEntry cohortEntry, ActorRef sender, Shard shard) {
  98         if(queuedCohortEntries.size() < queueCapacity) {
  99             queuedCohortEntries.offer(cohortEntry);
 100
 101             log.debug("{}: Enqueued transaction {}, queue size {}", name, cohortEntry.getTransactionID(),
 102                     queuedCohortEntries.size());
 103
 104             return true;
 105         } else {
 106             cohortCache.remove(cohortEntry.getTransactionID());
 107
 108             RuntimeException ex = new RuntimeException(
 109                     String.format("%s: Could not enqueue transaction %s - the maximum commit queue"+
 110                                   " capacity %d has been reached.",
 111                                   name, cohortEntry.getTransactionID(), queueCapacity));
 112             log.error(ex.getMessage());
 113             sender.tell(new Status.Failure(ex), shard.self());
 114             return false;
 115         }
 116     }
 117
 118     /**
 119      * This method is called to ready a transaction that was prepared by ShardTransaction actor. It caches
 120      * the prepared cohort entry for the given transactions ID in preparation for the subsequent 3-phase commit.
 121      *
 122      * @param ready the ForwardedReadyTransaction message to process
 123      * @param sender the sender of the message
 124      * @param shard the transaction's shard actor
 125      */
 126     void handleForwardedReadyTransaction(ForwardedReadyTransaction ready, ActorRef sender, Shard shard) {
 127         log.debug("{}: Readying transaction {}, client version {}", name,
 128                 ready.getTransactionID(), ready.getTxnClientVersion());
 129
 130         CohortEntry cohortEntry = new CohortEntry(ready.getTransactionID(), ready.getCohort());
 131         cohortCache.put(ready.getTransactionID(), cohortEntry);
 132
 133         if(!queueCohortEntry(cohortEntry, sender, shard)) {
 134             return;
 135         }
 136
 137         if(ready.getTxnClientVersion() < DataStoreVersions.LITHIUM_VERSION) {
 138             // Return our actor path as we'll handle the three phase commit except if the Tx client
 139             // version < Helium-1 version which means the Tx was initiated by a base Helium version node.
 140             // In that case, the subsequent 3-phase commit messages won't contain the transactionId so to
 141             // maintain backwards compatibility, we create a separate cohort actor to provide the compatible behavior.
 142             ActorRef replyActorPath = shard.self();
 143             if(ready.getTxnClientVersion() < DataStoreVersions.HELIUM_1_VERSION) {
 144                 log.debug("{}: Creating BackwardsCompatibleThreePhaseCommitCohort", name);
 145                 replyActorPath = shard.getContext().actorOf(BackwardsCompatibleThreePhaseCommitCohort.props(
 146                         ready.getTransactionID()));
 147             }
 148
 149             ReadyTransactionReply readyTransactionReply =
 150                     new ReadyTransactionReply(Serialization.serializedActorPath(replyActorPath),
 151                             ready.getTxnClientVersion());
 152             sender.tell(ready.isReturnSerialized() ? readyTransactionReply.toSerializable() :
 153                 readyTransactionReply, shard.self());
 154         } else {
 155             if(ready.isDoImmediateCommit()) {
 156                 cohortEntry.setDoImmediateCommit(true);
 157                 cohortEntry.setReplySender(sender);
 158                 cohortEntry.setShard(shard);
 159                 handleCanCommit(cohortEntry);
 160             } else {
 161                 // The caller does not want immediate commit - the 3-phase commit will be coordinated by the
 162                 // front-end so send back a ReadyTransactionReply with our actor path.
 163                 sender.tell(readyTransactionReply(shard), shard.self());
 164             }
 165         }
 166     }
 167
 168     /**
 169      * This method handles a BatchedModifications message for a transaction being prepared directly on the
 170      * Shard actor instead of via a ShardTransaction actor. If there's no currently cached
 171      * DOMStoreWriteTransaction, one is created. The batched modifications are applied to the write Tx. If
 172      * the BatchedModifications is ready to commit then a DOMStoreThreePhaseCommitCohort is created.
 173      *
 174      * @param batched the BatchedModifications message to process
 175      * @param sender the sender of the message
 176      * @param shard the transaction's shard actor
 177      */
 178     void handleBatchedModifications(BatchedModifications batched, ActorRef sender, Shard shard) {
 179         CohortEntry cohortEntry = cohortCache.get(batched.getTransactionID());
 180         if(cohortEntry == null) {
 181             cohortEntry = new CohortEntry(batched.getTransactionID(),
 182                     dataTree.newReadWriteTransaction(batched.getTransactionID(),
 183                         batched.getTransactionChainID()));
 184             cohortCache.put(batched.getTransactionID(), cohortEntry);
 185         }
 186
 187         if(log.isDebugEnabled()) {
 188             log.debug("{}: Applying {} batched modifications for Tx {}", name,
 189                     batched.getModifications().size(), batched.getTransactionID());
 190         }
 191
 192         cohortEntry.applyModifications(batched.getModifications());
 193
 194         if(batched.isReady()) {
 195             if(cohortEntry.getLastBatchedModificationsException() != null) {
 196                 cohortCache.remove(cohortEntry.getTransactionID());
 197                 throw cohortEntry.getLastBatchedModificationsException();
 198             }
 199
 200             if(cohortEntry.getTotalBatchedModificationsReceived() != batched.getTotalMessagesSent()) {
 201                 cohortCache.remove(cohortEntry.getTransactionID());
 202                 throw new IllegalStateException(String.format(
 203                         "The total number of batched messages received %d does not match the number sent %d",
 204                         cohortEntry.getTotalBatchedModificationsReceived(), batched.getTotalMessagesSent()));
 205             }
 206
 207             if(!queueCohortEntry(cohortEntry, sender, shard)) {
 208                 return;
 209             }
 210
 211             if(log.isDebugEnabled()) {
 212                 log.debug("{}: Readying Tx {}, client version {}", name,
 213                         batched.getTransactionID(), batched.getVersion());
 214             }
 215
 216             cohortEntry.ready(cohortDecorator, batched.isDoCommitOnReady());
 217
 218             if(batched.isDoCommitOnReady()) {
 219                 cohortEntry.setReplySender(sender);
 220                 cohortEntry.setShard(shard);
 221                 handleCanCommit(cohortEntry);
 222             } else {
 223                 sender.tell(readyTransactionReply(shard), shard.self());
 224             }
 225         } else {
 226             sender.tell(new BatchedModificationsReply(batched.getModifications().size()), shard.self());
 227         }
 228     }
 229
 230     /**
 231      * This method handles {@link ReadyLocalTransaction} message. All transaction modifications have
 232      * been prepared beforehand by the sender and we just need to drive them through into the dataTree.
 233      *
 234      * @param message the ReadyLocalTransaction message to process
 235      * @param sender the sender of the message
 236      * @param shard the transaction's shard actor
 237      */
 238     void handleReadyLocalTransaction(ReadyLocalTransaction message, ActorRef sender, Shard shard) {
 239         final ShardDataTreeCohort cohort = new SimpleShardDataTreeCohort(dataTree, message.getModification(),
 240                 message.getTransactionID());
 241         final CohortEntry cohortEntry = new CohortEntry(message.getTransactionID(), cohort);
 242         cohortCache.put(message.getTransactionID(), cohortEntry);
 243         cohortEntry.setDoImmediateCommit(message.isDoCommitOnReady());
 244
 245         if(!queueCohortEntry(cohortEntry, sender, shard)) {
 246             return;
 247         }
 248
 249         log.debug("{}: Applying local modifications for Tx {}", name, message.getTransactionID());
 250
 251         if (message.isDoCommitOnReady()) {
 252             cohortEntry.setReplySender(sender);
 253             cohortEntry.setShard(shard);
 254             handleCanCommit(cohortEntry);
 255         } else {
 256             sender.tell(readyTransactionReply(shard), shard.self());
 257         }
 258     }
 259
 260     private void handleCanCommit(CohortEntry cohortEntry) {
 261         String transactionID = cohortEntry.getTransactionID();
 262
 263         cohortEntry.updateLastAccessTime();
 264
 265         if(currentCohortEntry != null) {
 266             // There's already a Tx commit in progress so we can't process this entry yet - but it's in the
 267             // queue and will get processed after all prior entries complete.
 268
 269             if(log.isDebugEnabled()) {
 270                 log.debug("{}: Commit for Tx {} already in progress - skipping canCommit for {} for now",
 271                         name, currentCohortEntry.getTransactionID(), transactionID);
 272             }
 273
 274             return;
 275         }
 276
 277         // No Tx commit currently in progress - check if this entry is the next one in the queue, If so make
 278         // it the current entry and proceed with canCommit.
 279         // Purposely checking reference equality here.
 280         if(queuedCohortEntries.peek() == cohortEntry) {
 281             currentCohortEntry = queuedCohortEntries.poll();
 282             doCanCommit(currentCohortEntry);
 283         } else {
 284             if(log.isDebugEnabled()) {
 285                 log.debug("{}: Tx {} is the next pending canCommit - skipping {} for now",
 286                         name, queuedCohortEntries.peek().getTransactionID(), transactionID);
 287             }
 288         }
 289     }
 290
 291     /**
 292      * This method handles the canCommit phase for a transaction.
 293      *
 294      * @param transactionID the ID of the transaction to canCommit
 295      * @param sender the actor to which to send the response
 296      * @param shard the transaction's shard actor
 297      */
 298     void handleCanCommit(String transactionID, final ActorRef sender, final Shard shard) {
 299         // Lookup the cohort entry that was cached previously (or should have been) by
 300         // transactionReady (via the ForwardedReadyTransaction message).
 301         final CohortEntry cohortEntry = cohortCache.get(transactionID);
 302         if(cohortEntry == null) {
 303             // Either canCommit was invoked before ready(shouldn't happen)  or a long time passed
 304             // between canCommit and ready and the entry was expired from the cache.
 305             IllegalStateException ex = new IllegalStateException(
 306                     String.format("%s: No cohort entry found for transaction %s", name, transactionID));
 307             log.error(ex.getMessage());
 308             sender.tell(new Status.Failure(ex), shard.self());
 309             return;
 310         }
 311
 312         cohortEntry.setReplySender(sender);
 313         cohortEntry.setShard(shard);
 314
 315         handleCanCommit(cohortEntry);
 316     }
 317
 318     private void doCanCommit(final CohortEntry cohortEntry) {
 319         boolean canCommit = false;
 320         try {
 321             canCommit = cohortEntry.canCommit();
 322
 323             log.debug("{}: canCommit for {}: {}", name, cohortEntry.getTransactionID(), canCommit);
 324
 325             if(cohortEntry.isDoImmediateCommit()) {
 326                 if(canCommit) {
 327                     doCommit(cohortEntry);
 328                 } else {
 329                     cohortEntry.getReplySender().tell(new Status.Failure(new TransactionCommitFailedException(
 330                                 "Can Commit failed, no detailed cause available.")), cohortEntry.getShard().self());
 331                 }
 332             } else {
 333                 cohortEntry.getReplySender().tell(
 334                         canCommit ? CanCommitTransactionReply.YES.toSerializable() :
 335                             CanCommitTransactionReply.NO.toSerializable(), cohortEntry.getShard().self());
 336             }
 337         } catch (Exception e) {
 338             log.debug("{}: An exception occurred during canCommit", name, e);
 339
 340             Throwable failure = e;
 341             if(e instanceof ExecutionException) {
 342                 failure = e.getCause();
 343             }
 344
 345             cohortEntry.getReplySender().tell(new Status.Failure(failure), cohortEntry.getShard().self());
 346         } finally {
 347             if(!canCommit) {
 348                 // Remove the entry from the cache now.
 349                 currentTransactionComplete(cohortEntry.getTransactionID(), true);
 350             }
 351         }
 352     }
 353
 354     private boolean doCommit(CohortEntry cohortEntry) {
 355         log.debug("{}: Committing transaction {}", name, cohortEntry.getTransactionID());
 356
 357         boolean success = false;
 358
 359         // We perform the preCommit phase here atomically with the commit phase. This is an
 360         // optimization to eliminate the overhead of an extra preCommit message. We lose front-end
 361         // coordination of preCommit across shards in case of failure but preCommit should not
 362         // normally fail since we ensure only one concurrent 3-phase commit.
 363
 364         try {
 365             cohortEntry.preCommit();
 366
 367             cohortEntry.getShard().continueCommit(cohortEntry);
 368
 369             cohortEntry.updateLastAccessTime();
 370
 371             success = true;
 372         } catch (Exception e) {
 373             log.error("{} An exception occurred while preCommitting transaction {}",
 374                     name, cohortEntry.getTransactionID(), e);
 375             cohortEntry.getReplySender().tell(new akka.actor.Status.Failure(e), cohortEntry.getShard().self());
 376
 377             currentTransactionComplete(cohortEntry.getTransactionID(), true);
 378         }
 379
 380         return success;
 381     }
 382
 383     /**
 384      * This method handles the preCommit and commit phases for a transaction.
 385      *
 386      * @param transactionID the ID of the transaction to commit
 387      * @param sender the actor to which to send the response
 388      * @param shard the transaction's shard actor
 389      * @return true if the transaction was successfully prepared, false otherwise.
 390      */
 391     boolean handleCommit(final String transactionID, final ActorRef sender, final Shard shard) {
 392         // Get the current in-progress cohort entry in the commitCoordinator if it corresponds to
 393         // this transaction.
 394         final CohortEntry cohortEntry = getCohortEntryIfCurrent(transactionID);
 395         if(cohortEntry == null) {
 396             // We're not the current Tx - the Tx was likely expired b/c it took too long in
 397             // between the canCommit and commit messages.
 398             IllegalStateException ex = new IllegalStateException(
 399                     String.format("%s: Cannot commit transaction %s - it is not the current transaction",
 400                             name, transactionID));
 401             log.error(ex.getMessage());
 402             sender.tell(new akka.actor.Status.Failure(ex), shard.self());
 403             return false;
 404         }
 405
 406         cohortEntry.setReplySender(sender);
 407         return doCommit(cohortEntry);
 408     }
 409
 410     void handleAbort(final String transactionID, final ActorRef sender, final Shard shard) {
 411         CohortEntry cohortEntry = getCohortEntryIfCurrent(transactionID);
 412         if(cohortEntry != null) {
 413             // We don't remove the cached cohort entry here (ie pass false) in case the Tx was
 414             // aborted during replication in which case we may still commit locally if replication
 415             // succeeds.
 416             currentTransactionComplete(transactionID, false);
 417         } else {
 418             cohortEntry = getAndRemoveCohortEntry(transactionID);
 419         }
 420
 421         if(cohortEntry == null) {
 422             return;
 423         }
 424
 425         log.debug("{}: Aborting transaction {}", name, transactionID);
 426
 427         final ActorRef self = shard.getSelf();
 428         try {
 429             cohortEntry.abort();
 430
 431             shard.getShardMBean().incrementAbortTransactionsCount();
 432
 433             if(sender != null) {
 434                 sender.tell(new AbortTransactionReply().toSerializable(), self);
 435             }
 436         } catch (Exception e) {
 437             log.error("{}: An exception happened during abort", name, e);
 438
 439             if(sender != null) {
 440                 sender.tell(new akka.actor.Status.Failure(e), self);
 441             }
 442         }
 443     }
 444
 445     /**
 446      * Returns the cohort entry for the Tx commit currently in progress if the given transaction ID
 447      * matches the current entry.
 448      *
 449      * @param transactionID the ID of the transaction
 450      * @return the current CohortEntry or null if the given transaction ID does not match the
 451      *         current entry.
 452      */
 453     public CohortEntry getCohortEntryIfCurrent(String transactionID) {
 454         if(isCurrentTransaction(transactionID)) {
 455             return currentCohortEntry;
 456         }
 457
 458         return null;
 459     }
 460
 461     public CohortEntry getCurrentCohortEntry() {
 462         return currentCohortEntry;
 463     }
 464
 465     public CohortEntry getAndRemoveCohortEntry(String transactionID) {
 466         return cohortCache.remove(transactionID);
 467     }
 468
 469     public boolean isCurrentTransaction(String transactionID) {
 470         return currentCohortEntry != null &&
 471                 currentCohortEntry.getTransactionID().equals(transactionID);
 472     }
 473
 474     /**
 475      * This method is called when a transaction is complete, successful or not. If the given
 476      * given transaction ID matches the current in-progress transaction, the next cohort entry,
 477      * if any, is dequeued and processed.
 478      *
 479      * @param transactionID the ID of the completed transaction
 480      * @param removeCohortEntry if true the CohortEntry for the transaction is also removed from
 481      *        the cache.
 482      */
 483     public void currentTransactionComplete(String transactionID, boolean removeCohortEntry) {
 484         if(removeCohortEntry) {
 485             cohortCache.remove(transactionID);
 486         }
 487
 488         if(isCurrentTransaction(transactionID)) {
 489             currentCohortEntry = null;
 490
 491             log.debug("{}: currentTransactionComplete: {}", name, transactionID);
 492
 493             maybeProcessNextCohortEntry();
 494         }
 495     }
 496
 497     private void maybeProcessNextCohortEntry() {
 498         // Check if there's a next cohort entry waiting in the queue and if it is ready to commit. Also
 499         // clean out expired entries.
 500         Iterator<CohortEntry> iter = queuedCohortEntries.iterator();
 501         while(iter.hasNext()) {
 502             CohortEntry next = iter.next();
 503             if(next.isReadyToCommit()) {
 504                 if(currentCohortEntry == null) {
 505                     if(log.isDebugEnabled()) {
 506                         log.debug("{}: Next entry to canCommit {}", name, next);
 507                     }
 508
 509                     iter.remove();
 510                     currentCohortEntry = next;
 511                     currentCohortEntry.updateLastAccessTime();
 512                     doCanCommit(currentCohortEntry);
 513                 }
 514
 515                 break;
 516             } else if(next.isExpired(cacheExpiryTimeoutInMillis)) {
 517                 log.warn("{}: canCommit for transaction {} was not received within {} ms - entry removed from cache",
 518                         name, next.getTransactionID(), cacheExpiryTimeoutInMillis);
 519             } else if(!next.isAborted()) {
 520                 break;
 521             }
 522
 523             iter.remove();
 524             cohortCache.remove(next.getTransactionID());
 525         }
 526     }
 527
 528     void cleanupExpiredCohortEntries() {
 529         maybeProcessNextCohortEntry();
 530     }
 531
 532     @VisibleForTesting
 533     void setCohortDecorator(CohortDecorator cohortDecorator) {
 534         this.cohortDecorator = cohortDecorator;
 535     }
 536
 537     static class CohortEntry {
 538         private final String transactionID;
 539         private ShardDataTreeCohort cohort;
 540         private final ReadWriteShardDataTreeTransaction transaction;
 541         private RuntimeException lastBatchedModificationsException;
 542         private ActorRef replySender;
 543         private Shard shard;
 544         private boolean doImmediateCommit;
 545         private final Stopwatch lastAccessTimer = Stopwatch.createStarted();
 546         private int totalBatchedModificationsReceived;
 547         private boolean aborted;
 548
 549         CohortEntry(String transactionID, ReadWriteShardDataTreeTransaction transaction) {
 550             this.transaction = Preconditions.checkNotNull(transaction);
 551             this.transactionID = transactionID;
 552         }
 553
 554         CohortEntry(String transactionID, ShardDataTreeCohort cohort) {
 555             this.transactionID = transactionID;
 556             this.cohort = cohort;
 557             this.transaction = null;
 558         }
 559
 560         void updateLastAccessTime() {
 561             lastAccessTimer.reset();
 562             lastAccessTimer.start();
 563         }
 564
 565         String getTransactionID() {
 566             return transactionID;
 567         }
 568
 569         DataTreeCandidate getCandidate() {
 570             return cohort.getCandidate();
 571         }
 572
 573         int getTotalBatchedModificationsReceived() {
 574             return totalBatchedModificationsReceived;
 575         }
 576
 577         RuntimeException getLastBatchedModificationsException() {
 578             return lastBatchedModificationsException;
 579         }
 580
 581         void applyModifications(Iterable<Modification> modifications) {
 582             totalBatchedModificationsReceived++;
 583             if(lastBatchedModificationsException == null) {
 584                 for (Modification modification : modifications) {
 585                         try {
 586                             modification.apply(transaction.getSnapshot());
 587                         } catch (RuntimeException e) {
 588                             lastBatchedModificationsException = e;
 589                             throw e;
 590                         }
 591                 }
 592             }
 593         }
 594
 595         boolean canCommit() throws InterruptedException, ExecutionException {
 596             // We block on the future here (and also preCommit(), commit(), abort()) so we don't have to worry
 597             // about possibly accessing our state on a different thread outside of our dispatcher.
 598             // TODO: the ShardDataTreeCohort returns immediate Futures anyway which begs the question - why
 599             // bother even returning Futures from ShardDataTreeCohort if we have to treat them synchronously
 600             // anyway?. The Futures are really a remnant from when we were using the InMemoryDataBroker.
 601             return cohort.canCommit().get();
 602         }
 603
 604         void preCommit() throws InterruptedException, ExecutionException {
 605             cohort.preCommit().get();
 606         }
 607
 608         void commit() throws InterruptedException, ExecutionException {
 609             cohort.commit().get();
 610         }
 611
 612         void abort() throws InterruptedException, ExecutionException {
 613             aborted = true;
 614             cohort.abort().get();
 615         }
 616
 617         void ready(CohortDecorator cohortDecorator, boolean doImmediateCommit) {
 618             Preconditions.checkState(cohort == null, "cohort was already set");
 619
 620             setDoImmediateCommit(doImmediateCommit);
 621
 622             cohort = transaction.ready();
 623
 624             if(cohortDecorator != null) {
 625                 // Call the hook for unit tests.
 626                 cohort = cohortDecorator.decorate(transactionID, cohort);
 627             }
 628         }
 629
 630         boolean isReadyToCommit() {
 631             return replySender != null;
 632         }
 633
 634         boolean isExpired(long expireTimeInMillis) {
 635             return lastAccessTimer.elapsed(TimeUnit.MILLISECONDS) >= expireTimeInMillis;
 636         }
 637
 638         boolean isDoImmediateCommit() {
 639             return doImmediateCommit;
 640         }
 641
 642         void setDoImmediateCommit(boolean doImmediateCommit) {
 643             this.doImmediateCommit = doImmediateCommit;
 644         }
 645
 646         ActorRef getReplySender() {
 647             return replySender;
 648         }
 649
 650         void setReplySender(ActorRef replySender) {
 651             this.replySender = replySender;
 652         }
 653
 654         Shard getShard() {
 655             return shard;
 656         }
 657
 658         void setShard(Shard shard) {
 659             this.shard = shard;
 660         }
 661
 662
 663         boolean isAborted() {
 664             return aborted;
 665         }
 666
 667         @Override
 668         public String toString() {
 669             StringBuilder builder = new StringBuilder();
 670             builder.append("CohortEntry [transactionID=").append(transactionID).append(", doImmediateCommit=")
 671                     .append(doImmediateCommit).append("]");
 672             return builder.toString();
 673         }
 674     }
 675 }