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

   1 /*
   2  * Copyright (c) 2014 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
   9 package org.opendaylight.controller.cluster.datastore;
  10
  11 import akka.actor.ActorPath;
  12 import akka.actor.ActorSelection;
  13 import akka.dispatch.OnComplete;
  14
  15 import com.google.common.annotations.VisibleForTesting;
  16 import com.google.common.base.FinalizablePhantomReference;
  17 import com.google.common.base.FinalizableReferenceQueue;
  18 import com.google.common.base.Optional;
  19 import com.google.common.base.Preconditions;
  20 import com.google.common.collect.Lists;
  21 import com.google.common.util.concurrent.CheckedFuture;
  22 import com.google.common.util.concurrent.Futures;
  23 import com.google.common.util.concurrent.SettableFuture;
  24
  25 import org.opendaylight.controller.cluster.datastore.identifiers.TransactionIdentifier;
  26 import org.opendaylight.controller.cluster.datastore.messages.CloseTransaction;
  27 import org.opendaylight.controller.cluster.datastore.messages.CreateTransaction;
  28 import org.opendaylight.controller.cluster.datastore.messages.CreateTransactionReply;
  29 import org.opendaylight.controller.cluster.datastore.messages.DataExists;
  30 import org.opendaylight.controller.cluster.datastore.messages.DataExistsReply;
  31 import org.opendaylight.controller.cluster.datastore.messages.DeleteData;
  32 import org.opendaylight.controller.cluster.datastore.messages.MergeData;
  33 import org.opendaylight.controller.cluster.datastore.messages.ReadData;
  34 import org.opendaylight.controller.cluster.datastore.messages.ReadDataReply;
  35 import org.opendaylight.controller.cluster.datastore.messages.ReadyTransaction;
  36 import org.opendaylight.controller.cluster.datastore.messages.ReadyTransactionReply;
  37 import org.opendaylight.controller.cluster.datastore.messages.WriteData;
  38 import org.opendaylight.controller.cluster.datastore.shardstrategy.ShardStrategyFactory;
  39 import org.opendaylight.controller.cluster.datastore.utils.ActorContext;
  40 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
  41 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
  42 import org.opendaylight.controller.sal.core.spi.data.DOMStoreThreePhaseCommitCohort;
  43 import org.opendaylight.yangtools.util.concurrent.MappingCheckedFuture;
  44 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  45 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  46 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
  47 import org.slf4j.Logger;
  48 import org.slf4j.LoggerFactory;
  49
  50 import scala.Function1;
  51 import scala.concurrent.Future;
  52 import scala.runtime.AbstractFunction1;
  53
  54 import java.util.HashMap;
  55 import java.util.List;
  56 import java.util.Map;
  57 import java.util.concurrent.ConcurrentHashMap;
  58 import java.util.concurrent.atomic.AtomicBoolean;
  59 import java.util.concurrent.atomic.AtomicLong;
  60
  61 /**
  62  * TransactionProxy acts as a proxy for one or more transactions that were created on a remote shard
  63  * <p>
  64  * Creating a transaction on the consumer side will create one instance of a transaction proxy. If during
  65  * the transaction reads and writes are done on data that belongs to different shards then a separate transaction will
  66  * be created on each of those shards by the TransactionProxy
  67  *</p>
  68  * <p>
  69  * The TransactionProxy does not make any guarantees about atomicity or order in which the transactions on the various
  70  * shards will be executed.
  71  * </p>
  72  */
  73 public class TransactionProxy implements DOMStoreReadWriteTransaction {
  74     public enum TransactionType {
  75         READ_ONLY,
  76         WRITE_ONLY,
  77         READ_WRITE
  78     }
  79
  80     static Function1<Throwable, Throwable> SAME_FAILURE_TRANSFORMER = new AbstractFunction1<
  81                                                                           Throwable, Throwable>() {
  82         @Override
  83         public Throwable apply(Throwable failure) {
  84             return failure;
  85         }
  86     };
  87
  88     private static final AtomicLong counter = new AtomicLong();
  89
  90     private static final Logger
  91         LOG = LoggerFactory.getLogger(TransactionProxy.class);
  92
  93
  94     /**
  95      * Used to enqueue the PhantomReferences for read-only TransactionProxy instances. The
  96      * FinalizableReferenceQueue is safe to use statically in an OSGi environment as it uses some
  97      * trickery to clean up its internal thread when the bundle is unloaded.
  98      */
  99     private static final FinalizableReferenceQueue phantomReferenceQueue =
 100                                                                   new FinalizableReferenceQueue();
 101
 102     /**
 103      * This stores the TransactionProxyCleanupPhantomReference instances statically, This is
 104      * necessary because PhantomReferences need a hard reference so they're not garbage collected.
 105      * Once finalized, the TransactionProxyCleanupPhantomReference removes itself from this map
 106      * and thus becomes eligible for garbage collection.
 107      */
 108     private static final Map<TransactionProxyCleanupPhantomReference,
 109                              TransactionProxyCleanupPhantomReference> phantomReferenceCache =
 110                                                                         new ConcurrentHashMap<>();
 111
 112     /**
 113      * A PhantomReference that closes remote transactions for a TransactionProxy when it's
 114      * garbage collected. This is used for read-only transactions as they're not explicitly closed
 115      * by clients. So the only way to detect that a transaction is no longer in use and it's safe
 116      * to clean up is when it's garbage collected. It's inexact as to when an instance will be GC'ed
 117      * but TransactionProxy instances should generally be short-lived enough to avoid being moved
 118      * to the old generation space and thus should be cleaned up in a timely manner as the GC
 119      * runs on the young generation (eden, swap1...) space much more frequently.
 120      */
 121     private static class TransactionProxyCleanupPhantomReference
 122                                            extends FinalizablePhantomReference<TransactionProxy> {
 123
 124         private final List<ActorSelection> remoteTransactionActors;
 125         private final AtomicBoolean remoteTransactionActorsMB;
 126         private final ActorContext actorContext;
 127         private final TransactionIdentifier identifier;
 128
 129         protected TransactionProxyCleanupPhantomReference(TransactionProxy referent) {
 130             super(referent, phantomReferenceQueue);
 131
 132             // Note we need to cache the relevant fields from the TransactionProxy as we can't
 133             // have a hard reference to the TransactionProxy instance itself.
 134
 135             remoteTransactionActors = referent.remoteTransactionActors;
 136             remoteTransactionActorsMB = referent.remoteTransactionActorsMB;
 137             actorContext = referent.actorContext;
 138             identifier = referent.identifier;
 139         }
 140
 141         @Override
 142         public void finalizeReferent() {
 143             LOG.trace("Cleaning up {} Tx actors for TransactionProxy {}",
 144                     remoteTransactionActors.size(), identifier);
 145
 146             phantomReferenceCache.remove(this);
 147
 148             // Access the memory barrier volatile to ensure all previous updates to the
 149             // remoteTransactionActors list are visible to this thread.
 150
 151             if(remoteTransactionActorsMB.get()) {
 152                 for(ActorSelection actor : remoteTransactionActors) {
 153                     LOG.trace("Sending CloseTransaction to {}", actor);
 154                     actorContext.sendRemoteOperationAsync(actor,
 155                             new CloseTransaction().toSerializable());
 156                 }
 157             }
 158         }
 159     }
 160
 161     /**
 162      * Stores the remote Tx actors for each requested data store path to be used by the
 163      * PhantomReference to close the remote Tx's. This is only used for read-only Tx's. The
 164      * remoteTransactionActorsMB volatile serves as a memory barrier to publish updates to the
 165      * remoteTransactionActors list so they will be visible to the thread accessing the
 166      * PhantomReference.
 167      */
 168     private List<ActorSelection> remoteTransactionActors;
 169     private AtomicBoolean remoteTransactionActorsMB;
 170
 171     private final Map<String, TransactionContext> remoteTransactionPaths = new HashMap<>();
 172
 173     private final TransactionType transactionType;
 174     private final ActorContext actorContext;
 175     private final TransactionIdentifier identifier;
 176     private final SchemaContext schemaContext;
 177     private boolean inReadyState;
 178
 179     public TransactionProxy(ActorContext actorContext, TransactionType transactionType) {
 180         this.actorContext = Preconditions.checkNotNull(actorContext,
 181                 "actorContext should not be null");
 182         this.transactionType = Preconditions.checkNotNull(transactionType,
 183                 "transactionType should not be null");
 184         this.schemaContext = Preconditions.checkNotNull(actorContext.getSchemaContext(),
 185                 "schemaContext should not be null");
 186
 187         String memberName = actorContext.getCurrentMemberName();
 188         if(memberName == null){
 189             memberName = "UNKNOWN-MEMBER";
 190         }
 191
 192         this.identifier = TransactionIdentifier.builder().memberName(memberName).counter(
 193                 counter.getAndIncrement()).build();
 194
 195         if(transactionType == TransactionType.READ_ONLY) {
 196             // Read-only Tx's aren't explicitly closed by the client so we create a PhantomReference
 197             // to close the remote Tx's when this instance is no longer in use and is garbage
 198             // collected.
 199
 200             remoteTransactionActors = Lists.newArrayList();
 201             remoteTransactionActorsMB = new AtomicBoolean();
 202
 203             TransactionProxyCleanupPhantomReference cleanup =
 204                                               new TransactionProxyCleanupPhantomReference(this);
 205             phantomReferenceCache.put(cleanup, cleanup);
 206         }
 207
 208         LOG.debug("Created txn {} of type {}", identifier, transactionType);
 209     }
 210
 211     @VisibleForTesting
 212     List<Future<Object>> getRecordedOperationFutures() {
 213         List<Future<Object>> recordedOperationFutures = Lists.newArrayList();
 214         for(TransactionContext transactionContext : remoteTransactionPaths.values()) {
 215             recordedOperationFutures.addAll(transactionContext.getRecordedOperationFutures());
 216         }
 217
 218         return recordedOperationFutures;
 219     }
 220
 221     @Override
 222     public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read(
 223             final YangInstanceIdentifier path) {
 224
 225         Preconditions.checkState(transactionType != TransactionType.WRITE_ONLY,
 226                 "Read operation on write-only transaction is not allowed");
 227
 228         LOG.debug("Tx {} read {}", identifier, path);
 229
 230         createTransactionIfMissing(actorContext, path);
 231
 232         return transactionContext(path).readData(path);
 233     }
 234
 235     @Override
 236     public CheckedFuture<Boolean, ReadFailedException> exists(YangInstanceIdentifier path) {
 237
 238         Preconditions.checkState(transactionType != TransactionType.WRITE_ONLY,
 239                 "Exists operation on write-only transaction is not allowed");
 240
 241         LOG.debug("Tx {} exists {}", identifier, path);
 242
 243         createTransactionIfMissing(actorContext, path);
 244
 245         return transactionContext(path).dataExists(path);
 246     }
 247
 248     private void checkModificationState() {
 249         Preconditions.checkState(transactionType != TransactionType.READ_ONLY,
 250                 "Modification operation on read-only transaction is not allowed");
 251         Preconditions.checkState(!inReadyState,
 252                 "Transaction is sealed - further modifications are not allowed");
 253     }
 254
 255     @Override
 256     public void write(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 257
 258         checkModificationState();
 259
 260         LOG.debug("Tx {} write {}", identifier, path);
 261
 262         createTransactionIfMissing(actorContext, path);
 263
 264         transactionContext(path).writeData(path, data);
 265     }
 266
 267     @Override
 268     public void merge(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 269
 270         checkModificationState();
 271
 272         LOG.debug("Tx {} merge {}", identifier, path);
 273
 274         createTransactionIfMissing(actorContext, path);
 275
 276         transactionContext(path).mergeData(path, data);
 277     }
 278
 279     @Override
 280     public void delete(YangInstanceIdentifier path) {
 281
 282         checkModificationState();
 283
 284         LOG.debug("Tx {} delete {}", identifier, path);
 285
 286         createTransactionIfMissing(actorContext, path);
 287
 288         transactionContext(path).deleteData(path);
 289     }
 290
 291     @Override
 292     public DOMStoreThreePhaseCommitCohort ready() {
 293
 294         checkModificationState();
 295
 296         inReadyState = true;
 297
 298         LOG.debug("Tx {} Trying to get {} transactions ready for commit", identifier,
 299                 remoteTransactionPaths.size());
 300
 301         List<Future<ActorPath>> cohortPathFutures = Lists.newArrayList();
 302
 303         for(TransactionContext transactionContext : remoteTransactionPaths.values()) {
 304
 305             LOG.debug("Tx {} Readying transaction for shard {}", identifier,
 306                     transactionContext.getShardName());
 307
 308             cohortPathFutures.add(transactionContext.readyTransaction());
 309         }
 310
 311         return new ThreePhaseCommitCohortProxy(actorContext, cohortPathFutures,
 312                 identifier.toString());
 313     }
 314
 315     @Override
 316     public Object getIdentifier() {
 317         return this.identifier;
 318     }
 319
 320     @Override
 321     public void close() {
 322         for(TransactionContext transactionContext : remoteTransactionPaths.values()) {
 323             transactionContext.closeTransaction();
 324         }
 325
 326         remoteTransactionPaths.clear();
 327
 328         if(transactionType == TransactionType.READ_ONLY) {
 329             remoteTransactionActors.clear();
 330             remoteTransactionActorsMB.set(true);
 331         }
 332     }
 333
 334     private TransactionContext transactionContext(YangInstanceIdentifier path){
 335         String shardName = shardNameFromIdentifier(path);
 336         return remoteTransactionPaths.get(shardName);
 337     }
 338
 339     private String shardNameFromIdentifier(YangInstanceIdentifier path){
 340         return ShardStrategyFactory.getStrategy(path).findShard(path);
 341     }
 342
 343     private void createTransactionIfMissing(ActorContext actorContext, YangInstanceIdentifier path) {
 344         String shardName = ShardStrategyFactory.getStrategy(path).findShard(path);
 345
 346         TransactionContext transactionContext =
 347             remoteTransactionPaths.get(shardName);
 348
 349         if(transactionContext != null){
 350             // A transaction already exists with that shard
 351             return;
 352         }
 353
 354         try {
 355             Object response = actorContext.executeShardOperation(shardName,
 356                 new CreateTransaction(identifier.toString(),this.transactionType.ordinal() ).toSerializable());
 357             if (response.getClass().equals(CreateTransactionReply.SERIALIZABLE_CLASS)) {
 358                 CreateTransactionReply reply =
 359                     CreateTransactionReply.fromSerializable(response);
 360
 361                 String transactionPath = reply.getTransactionPath();
 362
 363                 LOG.debug("Tx {} Received transaction path = {}", identifier, transactionPath);
 364
 365                 ActorSelection transactionActor = actorContext.actorSelection(transactionPath);
 366
 367                 if(transactionType == TransactionType.READ_ONLY) {
 368                     // Add the actor to the remoteTransactionActors list for access by the
 369                     // cleanup PhantonReference.
 370                     remoteTransactionActors.add(transactionActor);
 371
 372                     // Write to the memory barrier volatile to publish the above update to the
 373                     // remoteTransactionActors list for thread visibility.
 374                     remoteTransactionActorsMB.set(true);
 375                 }
 376
 377                 transactionContext = new TransactionContextImpl(shardName, transactionPath,
 378                         transactionActor, identifier, actorContext, schemaContext);
 379
 380                 remoteTransactionPaths.put(shardName, transactionContext);
 381             } else {
 382                 throw new IllegalArgumentException(String.format(
 383                         "Invalid reply type {} for CreateTransaction", response.getClass()));
 384             }
 385         } catch(Exception e){
 386             LOG.debug("Tx {} Creating NoOpTransaction because of : {}", identifier, e.getMessage());
 387             remoteTransactionPaths.put(shardName, new NoOpTransactionContext(shardName, e, identifier));
 388         }
 389     }
 390
 391     private interface TransactionContext {
 392         String getShardName();
 393
 394         void closeTransaction();
 395
 396         Future<ActorPath> readyTransaction();
 397
 398         void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
 399
 400         void deleteData(YangInstanceIdentifier path);
 401
 402         void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
 403
 404         CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
 405                 final YangInstanceIdentifier path);
 406
 407         CheckedFuture<Boolean, ReadFailedException> dataExists(YangInstanceIdentifier path);
 408
 409         List<Future<Object>> getRecordedOperationFutures();
 410     }
 411
 412     private static abstract class AbstractTransactionContext implements TransactionContext {
 413
 414         protected final TransactionIdentifier identifier;
 415         protected final String shardName;
 416         protected final List<Future<Object>> recordedOperationFutures = Lists.newArrayList();
 417
 418         AbstractTransactionContext(String shardName, TransactionIdentifier identifier) {
 419             this.shardName = shardName;
 420             this.identifier = identifier;
 421         }
 422
 423         @Override
 424         public String getShardName() {
 425             return shardName;
 426         }
 427
 428         @Override
 429         public List<Future<Object>> getRecordedOperationFutures() {
 430             return recordedOperationFutures;
 431         }
 432     }
 433
 434     private static class TransactionContextImpl extends AbstractTransactionContext {
 435         private final Logger LOG = LoggerFactory.getLogger(TransactionContextImpl.class);
 436
 437         private final ActorContext actorContext;
 438         private final SchemaContext schemaContext;
 439         private final String actorPath;
 440         private final ActorSelection actor;
 441
 442         private TransactionContextImpl(String shardName, String actorPath,
 443                 ActorSelection actor, TransactionIdentifier identifier, ActorContext actorContext,
 444                 SchemaContext schemaContext) {
 445             super(shardName, identifier);
 446             this.actorPath = actorPath;
 447             this.actor = actor;
 448             this.actorContext = actorContext;
 449             this.schemaContext = schemaContext;
 450         }
 451
 452         private ActorSelection getActor() {
 453             return actor;
 454         }
 455
 456         private String getResolvedCohortPath(String cohortPath) {
 457             return actorContext.resolvePath(actorPath, cohortPath);
 458         }
 459
 460         @Override
 461         public void closeTransaction() {
 462             LOG.debug("Tx {} closeTransaction called", identifier);
 463             actorContext.sendRemoteOperationAsync(getActor(), new CloseTransaction().toSerializable());
 464         }
 465
 466         @Override
 467         public Future<ActorPath> readyTransaction() {
 468             LOG.debug("Tx {} readyTransaction called with {} previous recorded operations pending",
 469                     identifier, recordedOperationFutures.size());
 470
 471             // Send the ReadyTransaction message to the Tx actor.
 472
 473             final Future<Object> replyFuture = actorContext.executeRemoteOperationAsync(getActor(),
 474                     new ReadyTransaction().toSerializable());
 475
 476             // Combine all the previously recorded put/merge/delete operation reply Futures and the
 477             // ReadyTransactionReply Future into one Future. If any one fails then the combined
 478             // Future will fail. We need all prior operations and the ready operation to succeed
 479             // in order to attempt commit.
 480
 481             List<Future<Object>> futureList =
 482                     Lists.newArrayListWithCapacity(recordedOperationFutures.size() + 1);
 483             futureList.addAll(recordedOperationFutures);
 484             futureList.add(replyFuture);
 485
 486             Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(futureList,
 487                     actorContext.getActorSystem().dispatcher());
 488
 489             // Transform the combined Future into a Future that returns the cohort actor path from
 490             // the ReadyTransactionReply. That's the end result of the ready operation.
 491
 492             return combinedFutures.transform(new AbstractFunction1<Iterable<Object>, ActorPath>() {
 493                 @Override
 494                 public ActorPath apply(Iterable<Object> notUsed) {
 495
 496                     LOG.debug("Tx {} readyTransaction: pending recorded operations succeeded",
 497                             identifier);
 498
 499                     // At this point all the Futures succeeded and we need to extract the cohort
 500                     // actor path from the ReadyTransactionReply. For the recorded operations, they
 501                     // don't return any data so we're only interested that they completed
 502                     // successfully. We could be paranoid and verify the correct reply types but
 503                     // that really should never happen so it's not worth the overhead of
 504                     // de-serializing each reply.
 505
 506                     // Note the Future get call here won't block as it's complete.
 507                     Object serializedReadyReply = replyFuture.value().get().get();
 508                     if(serializedReadyReply.getClass().equals(
 509                                                      ReadyTransactionReply.SERIALIZABLE_CLASS)) {
 510                         ReadyTransactionReply reply = ReadyTransactionReply.fromSerializable(
 511                                 actorContext.getActorSystem(), serializedReadyReply);
 512
 513                         String resolvedCohortPath = getResolvedCohortPath(
 514                                 reply.getCohortPath().toString());
 515
 516                         LOG.debug("Tx {} readyTransaction: resolved cohort path {}",
 517                                 identifier, resolvedCohortPath);
 518
 519                         return actorContext.actorFor(resolvedCohortPath);
 520                     } else {
 521                         // Throwing an exception here will fail the Future.
 522
 523                         throw new IllegalArgumentException(String.format("Invalid reply type {}",
 524                                 serializedReadyReply.getClass()));
 525                     }
 526                 }
 527             }, SAME_FAILURE_TRANSFORMER, actorContext.getActorSystem().dispatcher());
 528         }
 529
 530         @Override
 531         public void deleteData(YangInstanceIdentifier path) {
 532             LOG.debug("Tx {} deleteData called path = {}", identifier, path);
 533             recordedOperationFutures.add(actorContext.executeRemoteOperationAsync(getActor(),
 534                     new DeleteData(path).toSerializable() ));
 535         }
 536
 537         @Override
 538         public void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 539             LOG.debug("Tx {} mergeData called path = {}", identifier, path);
 540             recordedOperationFutures.add(actorContext.executeRemoteOperationAsync(getActor(),
 541                     new MergeData(path, data, schemaContext).toSerializable()));
 542         }
 543
 544         @Override
 545         public void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 546             LOG.debug("Tx {} writeData called path = {}", identifier, path);
 547             recordedOperationFutures.add(actorContext.executeRemoteOperationAsync(getActor(),
 548                     new WriteData(path, data, schemaContext).toSerializable()));
 549         }
 550
 551         @Override
 552         public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
 553                 final YangInstanceIdentifier path) {
 554
 555             LOG.debug("Tx {} readData called path = {}", identifier, path);
 556
 557             final SettableFuture<Optional<NormalizedNode<?, ?>>> returnFuture = SettableFuture.create();
 558
 559             // If there were any previous recorded put/merge/delete operation reply Futures then we
 560             // must wait for them to successfully complete. This is necessary to honor the read
 561             // uncommitted semantics of the public API contract. If any one fails then fail the read.
 562
 563             if(recordedOperationFutures.isEmpty()) {
 564                 finishReadData(path, returnFuture);
 565             } else {
 566                 LOG.debug("Tx {} readData: verifying {} previous recorded operations",
 567                         identifier, recordedOperationFutures.size());
 568
 569                 // Note: we make a copy of recordedOperationFutures to be on the safe side in case
 570                 // Futures#sequence accesses the passed List on a different thread, as
 571                 // recordedOperationFutures is not synchronized.
 572
 573                 Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(
 574                         Lists.newArrayList(recordedOperationFutures),
 575                         actorContext.getActorSystem().dispatcher());
 576                 OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 577                     @Override
 578                     public void onComplete(Throwable failure, Iterable<Object> notUsed)
 579                             throws Throwable {
 580                         if(failure != null) {
 581                             LOG.debug("Tx {} readData: a recorded operation failed: {}",
 582                                     identifier, failure);
 583
 584                             returnFuture.setException(new ReadFailedException(
 585                                     "The read could not be performed because a previous put, merge,"
 586                                     + "or delete operation failed", failure));
 587                         } else {
 588                             finishReadData(path, returnFuture);
 589                         }
 590                     }
 591                 };
 592
 593                 combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 594             }
 595
 596             return MappingCheckedFuture.create(returnFuture, ReadFailedException.MAPPER);
 597         }
 598
 599         private void finishReadData(final YangInstanceIdentifier path,
 600                 final SettableFuture<Optional<NormalizedNode<?, ?>>> returnFuture) {
 601
 602             LOG.debug("Tx {} finishReadData called path = {}", identifier, path);
 603
 604             OnComplete<Object> onComplete = new OnComplete<Object>() {
 605                 @Override
 606                 public void onComplete(Throwable failure, Object readResponse) throws Throwable {
 607                     if(failure != null) {
 608                         LOG.debug("Tx {} read operation failed: {}", identifier, failure);
 609
 610                         returnFuture.setException(new ReadFailedException(
 611                                 "Error reading data for path " + path, failure));
 612
 613                     } else {
 614                         LOG.debug("Tx {} read operation succeeded", identifier, failure);
 615
 616                         if (readResponse.getClass().equals(ReadDataReply.SERIALIZABLE_CLASS)) {
 617                             ReadDataReply reply = ReadDataReply.fromSerializable(schemaContext,
 618                                     path, readResponse);
 619                             if (reply.getNormalizedNode() == null) {
 620                                 returnFuture.set(Optional.<NormalizedNode<?, ?>>absent());
 621                             } else {
 622                                 returnFuture.set(Optional.<NormalizedNode<?, ?>>of(
 623                                         reply.getNormalizedNode()));
 624                             }
 625                         } else {
 626                             returnFuture.setException(new ReadFailedException(
 627                                     "Invalid response reading data for path " + path));
 628                         }
 629                     }
 630                 }
 631             };
 632
 633             Future<Object> readFuture = actorContext.executeRemoteOperationAsync(getActor(),
 634                     new ReadData(path).toSerializable());
 635             readFuture.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 636         }
 637
 638         @Override
 639         public CheckedFuture<Boolean, ReadFailedException> dataExists(
 640                 final YangInstanceIdentifier path) {
 641
 642             LOG.debug("Tx {} dataExists called path = {}", identifier, path);
 643
 644             final SettableFuture<Boolean> returnFuture = SettableFuture.create();
 645
 646             // If there were any previous recorded put/merge/delete operation reply Futures then we
 647             // must wait for them to successfully complete. This is necessary to honor the read
 648             // uncommitted semantics of the public API contract. If any one fails then fail this
 649             // request.
 650
 651             if(recordedOperationFutures.isEmpty()) {
 652                 finishDataExists(path, returnFuture);
 653             } else {
 654                 LOG.debug("Tx {} dataExists: verifying {} previous recorded operations",
 655                         identifier, recordedOperationFutures.size());
 656
 657                 // Note: we make a copy of recordedOperationFutures to be on the safe side in case
 658                 // Futures#sequence accesses the passed List on a different thread, as
 659                 // recordedOperationFutures is not synchronized.
 660
 661                 Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(
 662                         Lists.newArrayList(recordedOperationFutures),
 663                         actorContext.getActorSystem().dispatcher());
 664                 OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 665                     @Override
 666                     public void onComplete(Throwable failure, Iterable<Object> notUsed)
 667                             throws Throwable {
 668                         if(failure != null) {
 669                             LOG.debug("Tx {} dataExists: a recorded operation failed: {}",
 670                                     identifier, failure);
 671
 672                             returnFuture.setException(new ReadFailedException(
 673                                     "The data exists could not be performed because a previous "
 674                                     + "put, merge, or delete operation failed", failure));
 675                         } else {
 676                             finishDataExists(path, returnFuture);
 677                         }
 678                     }
 679                 };
 680
 681                 combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 682             }
 683
 684             return MappingCheckedFuture.create(returnFuture, ReadFailedException.MAPPER);
 685         }
 686
 687         private void finishDataExists(final YangInstanceIdentifier path,
 688                 final SettableFuture<Boolean> returnFuture) {
 689
 690             LOG.debug("Tx {} finishDataExists called path = {}", identifier, path);
 691
 692             OnComplete<Object> onComplete = new OnComplete<Object>() {
 693                 @Override
 694                 public void onComplete(Throwable failure, Object response) throws Throwable {
 695                     if(failure != null) {
 696                         LOG.debug("Tx {} dataExists operation failed: {}", identifier, failure);
 697
 698                         returnFuture.setException(new ReadFailedException(
 699                                 "Error checking data exists for path " + path, failure));
 700                     } else {
 701                         LOG.debug("Tx {} dataExists operation succeeded", identifier, failure);
 702
 703                         if (response.getClass().equals(DataExistsReply.SERIALIZABLE_CLASS)) {
 704                             returnFuture.set(Boolean.valueOf(DataExistsReply.
 705                                         fromSerializable(response).exists()));
 706                         } else {
 707                             returnFuture.setException(new ReadFailedException(
 708                                     "Invalid response checking exists for path " + path));
 709                         }
 710                     }
 711                 }
 712             };
 713
 714             Future<Object> future = actorContext.executeRemoteOperationAsync(getActor(),
 715                     new DataExists(path).toSerializable());
 716             future.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 717         }
 718     }
 719
 720     private static class NoOpTransactionContext extends AbstractTransactionContext {
 721
 722         private final Logger LOG = LoggerFactory.getLogger(NoOpTransactionContext.class);
 723
 724         private final Exception failure;
 725
 726         public NoOpTransactionContext(String shardName, Exception failure,
 727                 TransactionIdentifier identifier){
 728             super(shardName, identifier);
 729             this.failure = failure;
 730         }
 731
 732         @Override
 733         public void closeTransaction() {
 734             LOG.debug("NoOpTransactionContext {} closeTransaction called", identifier);
 735         }
 736
 737         @Override
 738         public Future<ActorPath> readyTransaction() {
 739             LOG.debug("Tx {} readyTransaction called", identifier);
 740             return akka.dispatch.Futures.failed(failure);
 741         }
 742
 743         @Override
 744         public void deleteData(YangInstanceIdentifier path) {
 745             LOG.debug("Tx {} deleteData called path = {}", identifier, path);
 746         }
 747
 748         @Override
 749         public void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 750             LOG.debug("Tx {} mergeData called path = {}", identifier, path);
 751         }
 752
 753         @Override
 754         public void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 755             LOG.debug("Tx {} writeData called path = {}", identifier, path);
 756         }
 757
 758         @Override
 759         public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
 760             YangInstanceIdentifier path) {
 761             LOG.debug("Tx {} readData called path = {}", identifier, path);
 762             return Futures.immediateFailedCheckedFuture(new ReadFailedException(
 763                     "Error reading data for path " + path, failure));
 764         }
 765
 766         @Override
 767         public CheckedFuture<Boolean, ReadFailedException> dataExists(
 768             YangInstanceIdentifier path) {
 769             LOG.debug("Tx {} dataExists called path = {}", identifier, path);
 770             return Futures.immediateFailedCheckedFuture(new ReadFailedException(
 771                     "Error checking exists for path " + path, failure));
 772         }
 773     }
 774 }