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.Failure;
  12 import akka.serialization.Serialization;
  13 import com.google.common.annotations.VisibleForTesting;
  14 import com.google.common.base.Preconditions;
  15 import java.util.ArrayList;
  16 import java.util.Collection;
  17 import java.util.Collections;
  18 import java.util.HashMap;
  19 import java.util.Iterator;
  20 import java.util.LinkedList;
  21 import java.util.List;
  22 import java.util.Map;
  23 import java.util.Queue;
  24 import java.util.concurrent.ExecutionException;
  25 import org.opendaylight.controller.cluster.datastore.DataTreeCohortActorRegistry.CohortRegistryCommand;
  26 import org.opendaylight.controller.cluster.datastore.messages.AbortTransactionReply;
  27 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  28 import org.opendaylight.controller.cluster.datastore.messages.BatchedModificationsReply;
  29 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransaction;
  30 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransactionReply;
  31 import org.opendaylight.controller.cluster.datastore.messages.CommitTransaction;
  32 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  33 import org.opendaylight.controller.cluster.datastore.messages.ReadyLocalTransaction;
  34 import org.opendaylight.controller.cluster.datastore.messages.ReadyTransactionReply;
  35 import org.opendaylight.controller.cluster.datastore.utils.AbstractBatchedModificationsCursor;
  36 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
  37 import org.opendaylight.yangtools.concepts.Identifier;
  38 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  39 import org.slf4j.Logger;
  40
  41 /**
  42  * Coordinates commits for a shard ensuring only one concurrent 3-phase commit.
  43  *
  44  * @author Thomas Pantelis
  45  */
  46 final class ShardCommitCoordinator {
  47
  48     // Interface hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
  49     public interface CohortDecorator {
  50         ShardDataTreeCohort decorate(Identifier transactionID, ShardDataTreeCohort actual);
  51     }
  52
  53     private final Map<Identifier, CohortEntry> cohortCache = new HashMap<>();
  54
  55     private CohortEntry currentCohortEntry;
  56
  57     private final ShardDataTree dataTree;
  58
  59     private final DataTreeCohortActorRegistry cohortRegistry = new DataTreeCohortActorRegistry();
  60
  61     // We use a LinkedList here to avoid synchronization overhead with concurrent queue impls
  62     // since this should only be accessed on the shard's dispatcher.
  63     private final Queue<CohortEntry> queuedCohortEntries = new LinkedList<>();
  64
  65     private int queueCapacity;
  66
  67     private final Logger log;
  68
  69     private final String name;
  70
  71     private final long cacheExpiryTimeoutInMillis;
  72
  73     // This is a hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
  74     private CohortDecorator cohortDecorator;
  75
  76     private ReadyTransactionReply readyTransactionReply;
  77
  78     private Runnable runOnPendingTransactionsComplete;
  79
  80     ShardCommitCoordinator(ShardDataTree dataTree, long cacheExpiryTimeoutInMillis, int queueCapacity, Logger log,
  81             String name) {
  82
  83         this.queueCapacity = queueCapacity;
  84         this.log = log;
  85         this.name = name;
  86         this.dataTree = Preconditions.checkNotNull(dataTree);
  87         this.cacheExpiryTimeoutInMillis = cacheExpiryTimeoutInMillis;
  88     }
  89
  90     int getQueueSize() {
  91         return queuedCohortEntries.size();
  92     }
  93
  94     int getCohortCacheSize() {
  95         return cohortCache.size();
  96     }
  97
  98     void setQueueCapacity(int queueCapacity) {
  99         this.queueCapacity = queueCapacity;
 100     }
 101
 102     private ReadyTransactionReply readyTransactionReply(Shard shard) {
 103         if(readyTransactionReply == null) {
 104             readyTransactionReply = new ReadyTransactionReply(Serialization.serializedActorPath(shard.self()));
 105         }
 106
 107         return readyTransactionReply;
 108     }
 109
 110     private boolean queueCohortEntry(CohortEntry cohortEntry, ActorRef sender, Shard shard) {
 111         if(queuedCohortEntries.size() < queueCapacity) {
 112             queuedCohortEntries.offer(cohortEntry);
 113
 114             log.debug("{}: Enqueued transaction {}, queue size {}", name, cohortEntry.getTransactionID(),
 115                     queuedCohortEntries.size());
 116
 117             return true;
 118         } else {
 119             cohortCache.remove(cohortEntry.getTransactionID());
 120
 121             final RuntimeException ex = new RuntimeException(
 122                     String.format("%s: Could not enqueue transaction %s - the maximum commit queue"+
 123                                   " capacity %d has been reached.",
 124                                   name, cohortEntry.getTransactionID(), queueCapacity));
 125             log.error(ex.getMessage());
 126             sender.tell(new Failure(ex), shard.self());
 127             return false;
 128         }
 129     }
 130
 131     /**
 132      * This method is called to ready a transaction that was prepared by ShardTransaction actor. It caches
 133      * the prepared cohort entry for the given transactions ID in preparation for the subsequent 3-phase commit.
 134      *
 135      * @param ready the ForwardedReadyTransaction message to process
 136      * @param sender the sender of the message
 137      * @param shard the transaction's shard actor
 138      * @param schema
 139      */
 140     void handleForwardedReadyTransaction(ForwardedReadyTransaction ready, ActorRef sender, Shard shard,
 141             SchemaContext schema) {
 142         log.debug("{}: Readying transaction {}, client version {}", name,
 143                 ready.getTransactionID(), ready.getTxnClientVersion());
 144
 145         final ShardDataTreeCohort cohort = ready.getTransaction().ready();
 146         final CohortEntry cohortEntry = new CohortEntry(ready.getTransactionID(), cohort, cohortRegistry, schema, ready.getTxnClientVersion());
 147         cohortCache.put(cohortEntry.getTransactionID(), cohortEntry);
 148
 149         if(!queueCohortEntry(cohortEntry, sender, shard)) {
 150             return;
 151         }
 152
 153         if(ready.isDoImmediateCommit()) {
 154             cohortEntry.setDoImmediateCommit(true);
 155             cohortEntry.setReplySender(sender);
 156             cohortEntry.setShard(shard);
 157             handleCanCommit(cohortEntry);
 158         } else {
 159             // The caller does not want immediate commit - the 3-phase commit will be coordinated by the
 160             // front-end so send back a ReadyTransactionReply with our actor path.
 161             sender.tell(readyTransactionReply(shard), shard.self());
 162         }
 163     }
 164
 165     /**
 166      * This method handles a BatchedModifications message for a transaction being prepared directly on the
 167      * Shard actor instead of via a ShardTransaction actor. If there's no currently cached
 168      * DOMStoreWriteTransaction, one is created. The batched modifications are applied to the write Tx. If
 169      * the BatchedModifications is ready to commit then a DOMStoreThreePhaseCommitCohort is created.
 170      *
 171      * @param batched the BatchedModifications message to process
 172      * @param sender the sender of the message
 173      */
 174     void handleBatchedModifications(BatchedModifications batched, ActorRef sender, Shard shard) {
 175         CohortEntry cohortEntry = cohortCache.get(batched.getTransactionID());
 176         if(cohortEntry == null) {
 177             cohortEntry = new CohortEntry(batched.getTransactionID(),
 178                     dataTree.newReadWriteTransaction(batched.getTransactionID()),
 179                     cohortRegistry, dataTree.getSchemaContext(), batched.getVersion());
 180             cohortCache.put(cohortEntry.getTransactionID(), cohortEntry);
 181         }
 182
 183         if(log.isDebugEnabled()) {
 184             log.debug("{}: Applying {} batched modifications for Tx {}", name,
 185                     batched.getModifications().size(), batched.getTransactionID());
 186         }
 187
 188         cohortEntry.applyModifications(batched.getModifications());
 189
 190         if(batched.isReady()) {
 191             if(cohortEntry.getLastBatchedModificationsException() != null) {
 192                 cohortCache.remove(cohortEntry.getTransactionID());
 193                 throw cohortEntry.getLastBatchedModificationsException();
 194             }
 195
 196             if(cohortEntry.getTotalBatchedModificationsReceived() != batched.getTotalMessagesSent()) {
 197                 cohortCache.remove(cohortEntry.getTransactionID());
 198                 throw new IllegalStateException(String.format(
 199                         "The total number of batched messages received %d does not match the number sent %d",
 200                         cohortEntry.getTotalBatchedModificationsReceived(), batched.getTotalMessagesSent()));
 201             }
 202
 203             if(!queueCohortEntry(cohortEntry, sender, shard)) {
 204                 return;
 205             }
 206
 207             if(log.isDebugEnabled()) {
 208                 log.debug("{}: Readying Tx {}, client version {}", name,
 209                         batched.getTransactionID(), batched.getVersion());
 210             }
 211
 212             cohortEntry.ready(cohortDecorator, batched.isDoCommitOnReady());
 213
 214             if(batched.isDoCommitOnReady()) {
 215                 cohortEntry.setReplySender(sender);
 216                 cohortEntry.setShard(shard);
 217                 handleCanCommit(cohortEntry);
 218             } else {
 219                 sender.tell(readyTransactionReply(shard), shard.self());
 220             }
 221         } else {
 222             sender.tell(new BatchedModificationsReply(batched.getModifications().size()), shard.self());
 223         }
 224     }
 225
 226     /**
 227      * This method handles {@link ReadyLocalTransaction} message. All transaction modifications have
 228      * been prepared beforehand by the sender and we just need to drive them through into the
 229      * dataTree.
 230      *
 231      * @param message the ReadyLocalTransaction message to process
 232      * @param sender the sender of the message
 233      * @param shard the transaction's shard actor
 234      */
 235     void handleReadyLocalTransaction(ReadyLocalTransaction message, ActorRef sender, Shard shard) {
 236         final ShardDataTreeCohort cohort = new SimpleShardDataTreeCohort(dataTree, message.getModification(),
 237                 message.getTransactionID());
 238         final CohortEntry cohortEntry = new CohortEntry(message.getTransactionID(), cohort, cohortRegistry,
 239             dataTree.getSchemaContext(), DataStoreVersions.CURRENT_VERSION);
 240         cohortCache.put(cohortEntry.getTransactionID(), cohortEntry);
 241         cohortEntry.setDoImmediateCommit(message.isDoCommitOnReady());
 242
 243         if(!queueCohortEntry(cohortEntry, sender, shard)) {
 244             return;
 245         }
 246
 247         log.debug("{}: Applying local modifications for Tx {}", name, message.getTransactionID());
 248
 249         if (message.isDoCommitOnReady()) {
 250             cohortEntry.setReplySender(sender);
 251             cohortEntry.setShard(shard);
 252             handleCanCommit(cohortEntry);
 253         } else {
 254             sender.tell(readyTransactionReply(shard), shard.self());
 255         }
 256     }
 257
 258     Collection<BatchedModifications> createForwardedBatchedModifications(final BatchedModifications from,
 259             final int maxModificationsPerBatch) {
 260         CohortEntry cohortEntry = getAndRemoveCohortEntry(from.getTransactionID());
 261         if(cohortEntry == null || cohortEntry.getTransaction() == null) {
 262             return Collections.singletonList(from);
 263         }
 264
 265         cohortEntry.applyModifications(from.getModifications());
 266
 267         final LinkedList<BatchedModifications> newModifications = new LinkedList<>();
 268         cohortEntry.getTransaction().getSnapshot().applyToCursor(new AbstractBatchedModificationsCursor() {
 269             @Override
 270             protected BatchedModifications getModifications() {
 271                 if(newModifications.isEmpty() ||
 272                         newModifications.getLast().getModifications().size() >= maxModificationsPerBatch) {
 273                     newModifications.add(new BatchedModifications(from.getTransactionID(), from.getVersion()));
 274                 }
 275
 276                 return newModifications.getLast();
 277             }
 278         });
 279
 280         BatchedModifications last = newModifications.getLast();
 281         last.setDoCommitOnReady(from.isDoCommitOnReady());
 282         last.setReady(from.isReady());
 283         last.setTotalMessagesSent(newModifications.size());
 284         return newModifications;
 285     }
 286
 287     private void handleCanCommit(CohortEntry cohortEntry) {
 288         cohortEntry.updateLastAccessTime();
 289
 290         if(currentCohortEntry != null) {
 291             // There's already a Tx commit in progress so we can't process this entry yet - but it's in the
 292             // queue and will get processed after all prior entries complete.
 293
 294             if(log.isDebugEnabled()) {
 295                 log.debug("{}: Commit for Tx {} already in progress - skipping canCommit for {} for now",
 296                         name, currentCohortEntry.getTransactionID(), cohortEntry.getTransactionID());
 297             }
 298
 299             return;
 300         }
 301
 302         // No Tx commit currently in progress - check if this entry is the next one in the queue, If so make
 303         // it the current entry and proceed with canCommit.
 304         // Purposely checking reference equality here.
 305         if(queuedCohortEntries.peek() == cohortEntry) {
 306             currentCohortEntry = queuedCohortEntries.poll();
 307             doCanCommit(currentCohortEntry);
 308         } else {
 309             if(log.isDebugEnabled()) {
 310                 log.debug("{}: Tx {} is the next pending canCommit - skipping {} for now", name,
 311                         queuedCohortEntries.peek() != null ? queuedCohortEntries.peek().getTransactionID() : "???",
 312                                 cohortEntry.getTransactionID());
 313             }
 314         }
 315     }
 316
 317     /**
 318      * This method handles the canCommit phase for a transaction.
 319      *
 320      * @param transactionID the ID of the transaction to canCommit
 321      * @param sender the actor to which to send the response
 322      * @param shard the transaction's shard actor
 323      */
 324     void handleCanCommit(Identifier transactionID, final ActorRef sender, final Shard shard) {
 325         // Lookup the cohort entry that was cached previously (or should have been) by
 326         // transactionReady (via the ForwardedReadyTransaction message).
 327         final CohortEntry cohortEntry = cohortCache.get(transactionID);
 328         if(cohortEntry == null) {
 329             // Either canCommit was invoked before ready(shouldn't happen)  or a long time passed
 330             // between canCommit and ready and the entry was expired from the cache.
 331             IllegalStateException ex = new IllegalStateException(
 332                     String.format("%s: No cohort entry found for transaction %s", name, transactionID));
 333             log.error(ex.getMessage());
 334             sender.tell(new Failure(ex), shard.self());
 335             return;
 336         }
 337
 338         cohortEntry.setReplySender(sender);
 339         cohortEntry.setShard(shard);
 340
 341         handleCanCommit(cohortEntry);
 342     }
 343
 344     private void doCanCommit(final CohortEntry cohortEntry) {
 345         boolean canCommit = false;
 346         try {
 347             canCommit = cohortEntry.canCommit();
 348
 349             log.debug("{}: canCommit for {}: {}", name, cohortEntry.getTransactionID(), canCommit);
 350
 351             if(cohortEntry.isDoImmediateCommit()) {
 352                 if(canCommit) {
 353                     doCommit(cohortEntry);
 354                 } else {
 355                     cohortEntry.getReplySender().tell(new Failure(new TransactionCommitFailedException(
 356                                 "Can Commit failed, no detailed cause available.")), cohortEntry.getShard().self());
 357                 }
 358             } else {
 359                 cohortEntry.getReplySender().tell(
 360                         canCommit ? CanCommitTransactionReply.yes(cohortEntry.getClientVersion()).toSerializable() :
 361                             CanCommitTransactionReply.no(cohortEntry.getClientVersion()).toSerializable(),
 362                         cohortEntry.getShard().self());
 363             }
 364         } catch (Exception e) {
 365             log.debug("{}: An exception occurred during canCommit", name, e);
 366
 367             Throwable failure = e;
 368             if(e instanceof ExecutionException) {
 369                 failure = e.getCause();
 370             }
 371
 372             cohortEntry.getReplySender().tell(new Failure(failure), cohortEntry.getShard().self());
 373         } finally {
 374             if(!canCommit) {
 375                 // Remove the entry from the cache now.
 376                 currentTransactionComplete(cohortEntry.getTransactionID(), true);
 377             }
 378         }
 379     }
 380
 381     private boolean doCommit(CohortEntry cohortEntry) {
 382         log.debug("{}: Committing transaction {}", name, cohortEntry.getTransactionID());
 383
 384         boolean success = false;
 385
 386         // We perform the preCommit phase here atomically with the commit phase. This is an
 387         // optimization to eliminate the overhead of an extra preCommit message. We lose front-end
 388         // coordination of preCommit across shards in case of failure but preCommit should not
 389         // normally fail since we ensure only one concurrent 3-phase commit.
 390
 391         try {
 392             cohortEntry.preCommit();
 393
 394             cohortEntry.getShard().continueCommit(cohortEntry);
 395
 396             cohortEntry.updateLastAccessTime();
 397
 398             success = true;
 399         } catch (Exception e) {
 400             log.error("{} An exception occurred while preCommitting transaction {}",
 401                     name, cohortEntry.getTransactionID(), e);
 402             cohortEntry.getReplySender().tell(new Failure(e), cohortEntry.getShard().self());
 403
 404             currentTransactionComplete(cohortEntry.getTransactionID(), true);
 405         }
 406
 407         return success;
 408     }
 409
 410     /**
 411      * This method handles the preCommit and commit phases for a transaction.
 412      *
 413      * @param transactionID the ID of the transaction to commit
 414      * @param sender the actor to which to send the response
 415      * @param shard the transaction's shard actor
 416      * @return true if the transaction was successfully prepared, false otherwise.
 417      */
 418     boolean handleCommit(final Identifier transactionID, final ActorRef sender, final Shard shard) {
 419         // Get the current in-progress cohort entry in the commitCoordinator if it corresponds to
 420         // this transaction.
 421         final CohortEntry cohortEntry = getCohortEntryIfCurrent(transactionID);
 422         if(cohortEntry == null) {
 423             // We're not the current Tx - the Tx was likely expired b/c it took too long in
 424             // between the canCommit and commit messages.
 425             IllegalStateException ex = new IllegalStateException(
 426                     String.format("%s: Cannot commit transaction %s - it is not the current transaction",
 427                             name, transactionID));
 428             log.error(ex.getMessage());
 429             sender.tell(new Failure(ex), shard.self());
 430             return false;
 431         }
 432
 433         cohortEntry.setReplySender(sender);
 434         return doCommit(cohortEntry);
 435     }
 436
 437     void handleAbort(final Identifier transactionID, final ActorRef sender, final Shard shard) {
 438         CohortEntry cohortEntry = getCohortEntryIfCurrent(transactionID);
 439         if(cohortEntry != null) {
 440             // We don't remove the cached cohort entry here (ie pass false) in case the Tx was
 441             // aborted during replication in which case we may still commit locally if replication
 442             // succeeds.
 443             currentTransactionComplete(transactionID, false);
 444         } else {
 445             cohortEntry = getAndRemoveCohortEntry(transactionID);
 446         }
 447
 448         if(cohortEntry == null) {
 449             return;
 450         }
 451
 452         log.debug("{}: Aborting transaction {}", name, transactionID);
 453
 454         final ActorRef self = shard.getSelf();
 455         try {
 456             cohortEntry.abort();
 457
 458             shard.getShardMBean().incrementAbortTransactionsCount();
 459
 460             if(sender != null) {
 461                 sender.tell(AbortTransactionReply.instance(cohortEntry.getClientVersion()).toSerializable(), self);
 462             }
 463         } catch (Exception e) {
 464             log.error("{}: An exception happened during abort", name, e);
 465
 466             if(sender != null) {
 467                 sender.tell(new Failure(e), self);
 468             }
 469         }
 470     }
 471
 472     void checkForExpiredTransactions(final long timeout, final Shard shard) {
 473         CohortEntry cohortEntry = getCurrentCohortEntry();
 474         if(cohortEntry != null) {
 475             if(cohortEntry.isExpired(timeout)) {
 476                 log.warn("{}: Current transaction {} has timed out after {} ms - aborting",
 477                         name, cohortEntry.getTransactionID(), timeout);
 478
 479                 handleAbort(cohortEntry.getTransactionID(), null, shard);
 480             }
 481         }
 482
 483         cleanupExpiredCohortEntries();
 484     }
 485
 486     void abortPendingTransactions(final String reason, final Shard shard) {
 487         if(currentCohortEntry == null && queuedCohortEntries.isEmpty()) {
 488             return;
 489         }
 490
 491         List<CohortEntry> cohortEntries = getAndClearPendingCohortEntries();
 492
 493         log.debug("{}: Aborting {} pending queued transactions", name, cohortEntries.size());
 494
 495         for(CohortEntry cohortEntry: cohortEntries) {
 496             if(cohortEntry.getReplySender() != null) {
 497                 cohortEntry.getReplySender().tell(new Failure(new RuntimeException(reason)), shard.self());
 498             }
 499         }
 500     }
 501
 502     private List<CohortEntry> getAndClearPendingCohortEntries() {
 503         List<CohortEntry> cohortEntries = new ArrayList<>();
 504
 505         if(currentCohortEntry != null) {
 506             cohortEntries.add(currentCohortEntry);
 507             cohortCache.remove(currentCohortEntry.getTransactionID());
 508             currentCohortEntry = null;
 509         }
 510
 511         for(CohortEntry cohortEntry: queuedCohortEntries) {
 512             cohortEntries.add(cohortEntry);
 513             cohortCache.remove(cohortEntry.getTransactionID());
 514         }
 515
 516         queuedCohortEntries.clear();
 517         return cohortEntries;
 518     }
 519
 520     Collection<Object> convertPendingTransactionsToMessages(final int maxModificationsPerBatch) {
 521         if(currentCohortEntry == null && queuedCohortEntries.isEmpty()) {
 522             return Collections.emptyList();
 523         }
 524
 525         Collection<Object> messages = new ArrayList<>();
 526         List<CohortEntry> cohortEntries = getAndClearPendingCohortEntries();
 527         for(CohortEntry cohortEntry: cohortEntries) {
 528             if(cohortEntry.isExpired(cacheExpiryTimeoutInMillis) || cohortEntry.isAborted()) {
 529                 continue;
 530             }
 531
 532             final LinkedList<BatchedModifications> newModifications = new LinkedList<>();
 533             cohortEntry.getDataTreeModification().applyToCursor(new AbstractBatchedModificationsCursor() {
 534                 @Override
 535                 protected BatchedModifications getModifications() {
 536                     if(newModifications.isEmpty() ||
 537                             newModifications.getLast().getModifications().size() >= maxModificationsPerBatch) {
 538                         newModifications.add(new BatchedModifications(cohortEntry.getTransactionID(),
 539                                 cohortEntry.getClientVersion()));
 540         }
 541
 542                     return newModifications.getLast();
 543                 }
 544             });
 545
 546             if(!newModifications.isEmpty()) {
 547                 BatchedModifications last = newModifications.getLast();
 548                 last.setDoCommitOnReady(cohortEntry.isDoImmediateCommit());
 549                 last.setReady(true);
 550                 last.setTotalMessagesSent(newModifications.size());
 551                 messages.addAll(newModifications);
 552
 553                 if(!cohortEntry.isDoImmediateCommit() && cohortEntry.getState() == CohortEntry.State.CAN_COMMITTED) {
 554                     messages.add(new CanCommitTransaction(cohortEntry.getTransactionID(),
 555                             cohortEntry.getClientVersion()));
 556                 }
 557
 558                 if(!cohortEntry.isDoImmediateCommit() && cohortEntry.getState() == CohortEntry.State.PRE_COMMITTED) {
 559                     messages.add(new CommitTransaction(cohortEntry.getTransactionID(),
 560                             cohortEntry.getClientVersion()));
 561                 }
 562             }
 563         }
 564
 565         return messages;
 566     }
 567
 568     /**
 569      * Returns the cohort entry for the Tx commit currently in progress if the given transaction ID
 570      * matches the current entry.
 571      *
 572      * @param transactionID the ID of the transaction
 573      * @return the current CohortEntry or null if the given transaction ID does not match the
 574      *         current entry.
 575      */
 576     CohortEntry getCohortEntryIfCurrent(Identifier transactionID) {
 577         if(isCurrentTransaction(transactionID)) {
 578             return currentCohortEntry;
 579         }
 580
 581         return null;
 582     }
 583
 584     CohortEntry getCurrentCohortEntry() {
 585         return currentCohortEntry;
 586     }
 587
 588     CohortEntry getAndRemoveCohortEntry(Identifier transactionID) {
 589         return cohortCache.remove(transactionID);
 590     }
 591
 592     boolean isCurrentTransaction(Identifier transactionID) {
 593         return currentCohortEntry != null &&
 594                 currentCohortEntry.getTransactionID().equals(transactionID);
 595     }
 596
 597     /**
 598      * This method is called when a transaction is complete, successful or not. If the given
 599      * given transaction ID matches the current in-progress transaction, the next cohort entry,
 600      * if any, is dequeued and processed.
 601      *
 602      * @param transactionID the ID of the completed transaction
 603      * @param removeCohortEntry if true the CohortEntry for the transaction is also removed from
 604      *        the cache.
 605      */
 606     void currentTransactionComplete(Identifier transactionID, boolean removeCohortEntry) {
 607         if(removeCohortEntry) {
 608             cohortCache.remove(transactionID);
 609         }
 610
 611         if(isCurrentTransaction(transactionID)) {
 612             currentCohortEntry = null;
 613
 614             log.debug("{}: currentTransactionComplete: {}", name, transactionID);
 615
 616             maybeProcessNextCohortEntry();
 617         }
 618     }
 619
 620     private void maybeProcessNextCohortEntry() {
 621         // Check if there's a next cohort entry waiting in the queue and if it is ready to commit. Also
 622         // clean out expired entries.
 623         final Iterator<CohortEntry> iter = queuedCohortEntries.iterator();
 624         while(iter.hasNext()) {
 625             final CohortEntry next = iter.next();
 626             if(next.isReadyToCommit()) {
 627                 if(currentCohortEntry == null) {
 628                     if(log.isDebugEnabled()) {
 629                         log.debug("{}: Next entry to canCommit {}", name, next);
 630                     }
 631
 632                     iter.remove();
 633                     currentCohortEntry = next;
 634                     currentCohortEntry.updateLastAccessTime();
 635                     doCanCommit(currentCohortEntry);
 636                 }
 637
 638                 break;
 639             } else if(next.isExpired(cacheExpiryTimeoutInMillis)) {
 640                 log.warn("{}: canCommit for transaction {} was not received within {} ms - entry removed from cache",
 641                         name, next.getTransactionID(), cacheExpiryTimeoutInMillis);
 642             } else if(!next.isAborted()) {
 643                 break;
 644             }
 645
 646             iter.remove();
 647             cohortCache.remove(next.getTransactionID());
 648         }
 649
 650         maybeRunOperationOnPendingTransactionsComplete();
 651     }
 652
 653     void cleanupExpiredCohortEntries() {
 654         maybeProcessNextCohortEntry();
 655     }
 656
 657     void setRunOnPendingTransactionsComplete(Runnable operation) {
 658         runOnPendingTransactionsComplete = operation;
 659         maybeRunOperationOnPendingTransactionsComplete();
 660     }
 661
 662     private void maybeRunOperationOnPendingTransactionsComplete() {
 663         if(runOnPendingTransactionsComplete != null && currentCohortEntry == null && queuedCohortEntries.isEmpty()) {
 664             log.debug("{}: Pending transactions complete - running operation {}", name, runOnPendingTransactionsComplete);
 665
 666             runOnPendingTransactionsComplete.run();
 667             runOnPendingTransactionsComplete = null;
 668         }
 669     }
 670
 671     @VisibleForTesting
 672     void setCohortDecorator(CohortDecorator cohortDecorator) {
 673         this.cohortDecorator = cohortDecorator;
 674     }
 675
 676    void processCohortRegistryCommand(ActorRef sender, CohortRegistryCommand message) {
 677         cohortRegistry.process(sender, message);
 678     }
 679 }