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
  75     private final TransactionChainProxy transactionChainProxy;
  76
  77
  78
  79     public enum TransactionType {
  80         READ_ONLY,
  81         WRITE_ONLY,
  82         READ_WRITE
  83     }
  84
  85     static Function1<Throwable, Throwable> SAME_FAILURE_TRANSFORMER = new AbstractFunction1<
  86                                                                           Throwable, Throwable>() {
  87         @Override
  88         public Throwable apply(Throwable failure) {
  89             return failure;
  90         }
  91     };
  92
  93     private static final AtomicLong counter = new AtomicLong();
  94
  95     private static final Logger
  96         LOG = LoggerFactory.getLogger(TransactionProxy.class);
  97
  98
  99     /**
 100      * Used to enqueue the PhantomReferences for read-only TransactionProxy instances. The
 101      * FinalizableReferenceQueue is safe to use statically in an OSGi environment as it uses some
 102      * trickery to clean up its internal thread when the bundle is unloaded.
 103      */
 104     private static final FinalizableReferenceQueue phantomReferenceQueue =
 105                                                                   new FinalizableReferenceQueue();
 106
 107     /**
 108      * This stores the TransactionProxyCleanupPhantomReference instances statically, This is
 109      * necessary because PhantomReferences need a hard reference so they're not garbage collected.
 110      * Once finalized, the TransactionProxyCleanupPhantomReference removes itself from this map
 111      * and thus becomes eligible for garbage collection.
 112      */
 113     private static final Map<TransactionProxyCleanupPhantomReference,
 114                              TransactionProxyCleanupPhantomReference> phantomReferenceCache =
 115                                                                         new ConcurrentHashMap<>();
 116
 117     /**
 118      * A PhantomReference that closes remote transactions for a TransactionProxy when it's
 119      * garbage collected. This is used for read-only transactions as they're not explicitly closed
 120      * by clients. So the only way to detect that a transaction is no longer in use and it's safe
 121      * to clean up is when it's garbage collected. It's inexact as to when an instance will be GC'ed
 122      * but TransactionProxy instances should generally be short-lived enough to avoid being moved
 123      * to the old generation space and thus should be cleaned up in a timely manner as the GC
 124      * runs on the young generation (eden, swap1...) space much more frequently.
 125      */
 126     private static class TransactionProxyCleanupPhantomReference
 127                                            extends FinalizablePhantomReference<TransactionProxy> {
 128
 129         private final List<ActorSelection> remoteTransactionActors;
 130         private final AtomicBoolean remoteTransactionActorsMB;
 131         private final ActorContext actorContext;
 132         private final TransactionIdentifier identifier;
 133
 134         protected TransactionProxyCleanupPhantomReference(TransactionProxy referent) {
 135             super(referent, phantomReferenceQueue);
 136
 137             // Note we need to cache the relevant fields from the TransactionProxy as we can't
 138             // have a hard reference to the TransactionProxy instance itself.
 139
 140             remoteTransactionActors = referent.remoteTransactionActors;
 141             remoteTransactionActorsMB = referent.remoteTransactionActorsMB;
 142             actorContext = referent.actorContext;
 143             identifier = referent.identifier;
 144         }
 145
 146         @Override
 147         public void finalizeReferent() {
 148             LOG.trace("Cleaning up {} Tx actors for TransactionProxy {}",
 149                     remoteTransactionActors.size(), identifier);
 150
 151             phantomReferenceCache.remove(this);
 152
 153             // Access the memory barrier volatile to ensure all previous updates to the
 154             // remoteTransactionActors list are visible to this thread.
 155
 156             if(remoteTransactionActorsMB.get()) {
 157                 for(ActorSelection actor : remoteTransactionActors) {
 158                     LOG.trace("Sending CloseTransaction to {}", actor);
 159                     actorContext.sendRemoteOperationAsync(actor,
 160                             new CloseTransaction().toSerializable());
 161                 }
 162             }
 163         }
 164     }
 165
 166     /**
 167      * Stores the remote Tx actors for each requested data store path to be used by the
 168      * PhantomReference to close the remote Tx's. This is only used for read-only Tx's. The
 169      * remoteTransactionActorsMB volatile serves as a memory barrier to publish updates to the
 170      * remoteTransactionActors list so they will be visible to the thread accessing the
 171      * PhantomReference.
 172      */
 173     private List<ActorSelection> remoteTransactionActors;
 174     private AtomicBoolean remoteTransactionActorsMB;
 175
 176     private final Map<String, TransactionContext> remoteTransactionPaths = new HashMap<>();
 177
 178     private final TransactionType transactionType;
 179     private final ActorContext actorContext;
 180     private final TransactionIdentifier identifier;
 181     private final SchemaContext schemaContext;
 182     private boolean inReadyState;
 183
 184     public TransactionProxy(ActorContext actorContext, TransactionType transactionType) {
 185         this(actorContext, transactionType, null);
 186     }
 187
 188     @VisibleForTesting
 189     List<Future<Object>> getRecordedOperationFutures() {
 190         List<Future<Object>> recordedOperationFutures = Lists.newArrayList();
 191         for(TransactionContext transactionContext : remoteTransactionPaths.values()) {
 192             recordedOperationFutures.addAll(transactionContext.getRecordedOperationFutures());
 193         }
 194
 195         return recordedOperationFutures;
 196     }
 197
 198     public TransactionProxy(ActorContext actorContext, TransactionType transactionType, TransactionChainProxy transactionChainProxy) {
 199         this.actorContext = Preconditions.checkNotNull(actorContext,
 200             "actorContext should not be null");
 201         this.transactionType = Preconditions.checkNotNull(transactionType,
 202             "transactionType should not be null");
 203         this.schemaContext = Preconditions.checkNotNull(actorContext.getSchemaContext(),
 204             "schemaContext should not be null");
 205         this.transactionChainProxy = transactionChainProxy;
 206
 207         String memberName = actorContext.getCurrentMemberName();
 208         if(memberName == null){
 209             memberName = "UNKNOWN-MEMBER";
 210         }
 211
 212         this.identifier = TransactionIdentifier.builder().memberName(memberName).counter(
 213             counter.getAndIncrement()).build();
 214
 215         if(transactionType == TransactionType.READ_ONLY) {
 216             // Read-only Tx's aren't explicitly closed by the client so we create a PhantomReference
 217             // to close the remote Tx's when this instance is no longer in use and is garbage
 218             // collected.
 219
 220             remoteTransactionActors = Lists.newArrayList();
 221             remoteTransactionActorsMB = new AtomicBoolean();
 222
 223             TransactionProxyCleanupPhantomReference cleanup =
 224                 new TransactionProxyCleanupPhantomReference(this);
 225             phantomReferenceCache.put(cleanup, cleanup);
 226         }
 227         if(LOG.isDebugEnabled()) {
 228             LOG.debug("Created txn {} of type {}", identifier, transactionType);
 229         }
 230     }
 231
 232     @Override
 233     public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read(
 234             final YangInstanceIdentifier path) {
 235
 236         Preconditions.checkState(transactionType != TransactionType.WRITE_ONLY,
 237                 "Read operation on write-only transaction is not allowed");
 238
 239         if(LOG.isDebugEnabled()) {
 240             LOG.debug("Tx {} read {}", identifier, path);
 241         }
 242         createTransactionIfMissing(actorContext, path);
 243
 244         return transactionContext(path).readData(path);
 245     }
 246
 247     @Override
 248     public CheckedFuture<Boolean, ReadFailedException> exists(YangInstanceIdentifier path) {
 249
 250         Preconditions.checkState(transactionType != TransactionType.WRITE_ONLY,
 251                 "Exists operation on write-only transaction is not allowed");
 252
 253         if(LOG.isDebugEnabled()) {
 254             LOG.debug("Tx {} exists {}", identifier, path);
 255         }
 256         createTransactionIfMissing(actorContext, path);
 257
 258         return transactionContext(path).dataExists(path);
 259     }
 260
 261     private void checkModificationState() {
 262         Preconditions.checkState(transactionType != TransactionType.READ_ONLY,
 263                 "Modification operation on read-only transaction is not allowed");
 264         Preconditions.checkState(!inReadyState,
 265                 "Transaction is sealed - further modifications are not allowed");
 266     }
 267
 268     @Override
 269     public void write(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 270
 271         checkModificationState();
 272
 273         if(LOG.isDebugEnabled()) {
 274             LOG.debug("Tx {} write {}", identifier, path);
 275         }
 276         createTransactionIfMissing(actorContext, path);
 277
 278         transactionContext(path).writeData(path, data);
 279     }
 280
 281     @Override
 282     public void merge(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 283
 284         checkModificationState();
 285
 286         if(LOG.isDebugEnabled()) {
 287             LOG.debug("Tx {} merge {}", identifier, path);
 288         }
 289         createTransactionIfMissing(actorContext, path);
 290
 291         transactionContext(path).mergeData(path, data);
 292     }
 293
 294     @Override
 295     public void delete(YangInstanceIdentifier path) {
 296
 297         checkModificationState();
 298         if(LOG.isDebugEnabled()) {
 299             LOG.debug("Tx {} delete {}", identifier, path);
 300         }
 301         createTransactionIfMissing(actorContext, path);
 302
 303         transactionContext(path).deleteData(path);
 304     }
 305
 306     @Override
 307     public DOMStoreThreePhaseCommitCohort ready() {
 308
 309         checkModificationState();
 310
 311         inReadyState = true;
 312
 313         if(LOG.isDebugEnabled()) {
 314             LOG.debug("Tx {} Trying to get {} transactions ready for commit", identifier,
 315                 remoteTransactionPaths.size());
 316         }
 317         List<Future<ActorPath>> cohortPathFutures = Lists.newArrayList();
 318
 319         for(TransactionContext transactionContext : remoteTransactionPaths.values()) {
 320
 321             if(LOG.isDebugEnabled()) {
 322                 LOG.debug("Tx {} Readying transaction for shard {}", identifier,
 323                     transactionContext.getShardName());
 324             }
 325             cohortPathFutures.add(transactionContext.readyTransaction());
 326         }
 327
 328         if(transactionChainProxy != null){
 329             transactionChainProxy.onTransactionReady(cohortPathFutures);
 330         }
 331
 332         return new ThreePhaseCommitCohortProxy(actorContext, cohortPathFutures,
 333                 identifier.toString());
 334     }
 335
 336     @Override
 337     public Object getIdentifier() {
 338         return this.identifier;
 339     }
 340
 341     @Override
 342     public void close() {
 343         for(TransactionContext transactionContext : remoteTransactionPaths.values()) {
 344             transactionContext.closeTransaction();
 345         }
 346
 347         remoteTransactionPaths.clear();
 348
 349         if(transactionType == TransactionType.READ_ONLY) {
 350             remoteTransactionActors.clear();
 351             remoteTransactionActorsMB.set(true);
 352         }
 353     }
 354
 355     private TransactionContext transactionContext(YangInstanceIdentifier path){
 356         String shardName = shardNameFromIdentifier(path);
 357         return remoteTransactionPaths.get(shardName);
 358     }
 359
 360     private String shardNameFromIdentifier(YangInstanceIdentifier path){
 361         return ShardStrategyFactory.getStrategy(path).findShard(path);
 362     }
 363
 364     private void createTransactionIfMissing(ActorContext actorContext,
 365         YangInstanceIdentifier path) {
 366
 367         if(transactionChainProxy != null){
 368             transactionChainProxy.waitTillCurrentTransactionReady();
 369         }
 370
 371         String shardName = ShardStrategyFactory.getStrategy(path).findShard(path);
 372
 373         TransactionContext transactionContext =
 374             remoteTransactionPaths.get(shardName);
 375
 376         if (transactionContext != null) {
 377             // A transaction already exists with that shard
 378             return;
 379         }
 380
 381         try {
 382             Object response = actorContext.executeShardOperation(shardName,
 383                 new CreateTransaction(identifier.toString(), this.transactionType.ordinal(),
 384                     getTransactionChainId()).toSerializable());
 385             if (response.getClass().equals(CreateTransactionReply.SERIALIZABLE_CLASS)) {
 386                 CreateTransactionReply reply =
 387                     CreateTransactionReply.fromSerializable(response);
 388
 389                 String transactionPath = reply.getTransactionPath();
 390
 391                 if(LOG.isDebugEnabled()) {
 392                     LOG.debug("Tx {} Received transaction path = {}", identifier, transactionPath);
 393                 }
 394                 ActorSelection transactionActor = actorContext.actorSelection(transactionPath);
 395
 396                 if (transactionType == TransactionType.READ_ONLY) {
 397                     // Add the actor to the remoteTransactionActors list for access by the
 398                     // cleanup PhantonReference.
 399                     remoteTransactionActors.add(transactionActor);
 400
 401                     // Write to the memory barrier volatile to publish the above update to the
 402                     // remoteTransactionActors list for thread visibility.
 403                     remoteTransactionActorsMB.set(true);
 404                 }
 405
 406                 transactionContext = new TransactionContextImpl(shardName, transactionPath,
 407                     transactionActor, identifier, actorContext, schemaContext);
 408
 409                 remoteTransactionPaths.put(shardName, transactionContext);
 410             } else {
 411                 throw new IllegalArgumentException(String.format(
 412                     "Invalid reply type {} for CreateTransaction", response.getClass()));
 413             }
 414         } catch (Exception e) {
 415             if(LOG.isDebugEnabled()) {
 416                 LOG.debug("Tx {} Creating NoOpTransaction because of : {}", identifier, e.getMessage());
 417             }
 418             remoteTransactionPaths
 419                 .put(shardName, new NoOpTransactionContext(shardName, e, identifier));
 420         }
 421     }
 422
 423     public String getTransactionChainId() {
 424         if(transactionChainProxy == null){
 425             return "";
 426         }
 427         return transactionChainProxy.getTransactionChainId();
 428     }
 429
 430
 431     private interface TransactionContext {
 432         String getShardName();
 433
 434         void closeTransaction();
 435
 436         Future<ActorPath> readyTransaction();
 437
 438         void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
 439
 440         void deleteData(YangInstanceIdentifier path);
 441
 442         void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
 443
 444         CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
 445                 final YangInstanceIdentifier path);
 446
 447         CheckedFuture<Boolean, ReadFailedException> dataExists(YangInstanceIdentifier path);
 448
 449         List<Future<Object>> getRecordedOperationFutures();
 450     }
 451
 452     private static abstract class AbstractTransactionContext implements TransactionContext {
 453
 454         protected final TransactionIdentifier identifier;
 455         protected final String shardName;
 456         protected final List<Future<Object>> recordedOperationFutures = Lists.newArrayList();
 457
 458         AbstractTransactionContext(String shardName, TransactionIdentifier identifier) {
 459             this.shardName = shardName;
 460             this.identifier = identifier;
 461         }
 462
 463         @Override
 464         public String getShardName() {
 465             return shardName;
 466         }
 467
 468         @Override
 469         public List<Future<Object>> getRecordedOperationFutures() {
 470             return recordedOperationFutures;
 471         }
 472     }
 473
 474     private static class TransactionContextImpl extends AbstractTransactionContext {
 475         private final Logger LOG = LoggerFactory.getLogger(TransactionContextImpl.class);
 476
 477         private final ActorContext actorContext;
 478         private final SchemaContext schemaContext;
 479         private final String actorPath;
 480         private final ActorSelection actor;
 481
 482         private TransactionContextImpl(String shardName, String actorPath,
 483                 ActorSelection actor, TransactionIdentifier identifier, ActorContext actorContext,
 484                 SchemaContext schemaContext) {
 485             super(shardName, identifier);
 486             this.actorPath = actorPath;
 487             this.actor = actor;
 488             this.actorContext = actorContext;
 489             this.schemaContext = schemaContext;
 490         }
 491
 492         private ActorSelection getActor() {
 493             return actor;
 494         }
 495
 496         private String getResolvedCohortPath(String cohortPath) {
 497             return actorContext.resolvePath(actorPath, cohortPath);
 498         }
 499
 500         @Override
 501         public void closeTransaction() {
 502             if(LOG.isDebugEnabled()) {
 503                 LOG.debug("Tx {} closeTransaction called", identifier);
 504             }
 505             actorContext.sendRemoteOperationAsync(getActor(), new CloseTransaction().toSerializable());
 506         }
 507
 508         @Override
 509         public Future<ActorPath> readyTransaction() {
 510             if(LOG.isDebugEnabled()) {
 511                 LOG.debug("Tx {} readyTransaction called with {} previous recorded operations pending",
 512                     identifier, recordedOperationFutures.size());
 513             }
 514             // Send the ReadyTransaction message to the Tx actor.
 515
 516             final Future<Object> replyFuture = actorContext.executeRemoteOperationAsync(getActor(),
 517                     new ReadyTransaction().toSerializable());
 518
 519             // Combine all the previously recorded put/merge/delete operation reply Futures and the
 520             // ReadyTransactionReply Future into one Future. If any one fails then the combined
 521             // Future will fail. We need all prior operations and the ready operation to succeed
 522             // in order to attempt commit.
 523
 524             List<Future<Object>> futureList =
 525                     Lists.newArrayListWithCapacity(recordedOperationFutures.size() + 1);
 526             futureList.addAll(recordedOperationFutures);
 527             futureList.add(replyFuture);
 528
 529             Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(futureList,
 530                     actorContext.getActorSystem().dispatcher());
 531
 532             // Transform the combined Future into a Future that returns the cohort actor path from
 533             // the ReadyTransactionReply. That's the end result of the ready operation.
 534
 535             return combinedFutures.transform(new AbstractFunction1<Iterable<Object>, ActorPath>() {
 536                 @Override
 537                 public ActorPath apply(Iterable<Object> notUsed) {
 538                     if(LOG.isDebugEnabled()) {
 539                         LOG.debug("Tx {} readyTransaction: pending recorded operations succeeded",
 540                             identifier);
 541                     }
 542                     // At this point all the Futures succeeded and we need to extract the cohort
 543                     // actor path from the ReadyTransactionReply. For the recorded operations, they
 544                     // don't return any data so we're only interested that they completed
 545                     // successfully. We could be paranoid and verify the correct reply types but
 546                     // that really should never happen so it's not worth the overhead of
 547                     // de-serializing each reply.
 548
 549                     // Note the Future get call here won't block as it's complete.
 550                     Object serializedReadyReply = replyFuture.value().get().get();
 551                     if(serializedReadyReply.getClass().equals(
 552                                                      ReadyTransactionReply.SERIALIZABLE_CLASS)) {
 553                         ReadyTransactionReply reply = ReadyTransactionReply.fromSerializable(
 554                                 actorContext.getActorSystem(), serializedReadyReply);
 555
 556                         String resolvedCohortPath = getResolvedCohortPath(
 557                                 reply.getCohortPath().toString());
 558
 559                         if(LOG.isDebugEnabled()) {
 560                             LOG.debug("Tx {} readyTransaction: resolved cohort path {}",
 561                                 identifier, resolvedCohortPath);
 562                         }
 563                         return actorContext.actorFor(resolvedCohortPath);
 564                     } else {
 565                         // Throwing an exception here will fail the Future.
 566
 567                         throw new IllegalArgumentException(String.format("Invalid reply type {}",
 568                                 serializedReadyReply.getClass()));
 569                     }
 570                 }
 571             }, SAME_FAILURE_TRANSFORMER, actorContext.getActorSystem().dispatcher());
 572         }
 573
 574         @Override
 575         public void deleteData(YangInstanceIdentifier path) {
 576             if(LOG.isDebugEnabled()) {
 577                 LOG.debug("Tx {} deleteData called path = {}", identifier, path);
 578             }
 579             recordedOperationFutures.add(actorContext.executeRemoteOperationAsync(getActor(),
 580                     new DeleteData(path).toSerializable() ));
 581         }
 582
 583         @Override
 584         public void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 585             if(LOG.isDebugEnabled()) {
 586                 LOG.debug("Tx {} mergeData called path = {}", identifier, path);
 587             }
 588             recordedOperationFutures.add(actorContext.executeRemoteOperationAsync(getActor(),
 589                     new MergeData(path, data, schemaContext).toSerializable()));
 590         }
 591
 592         @Override
 593         public void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 594             if(LOG.isDebugEnabled()) {
 595                 LOG.debug("Tx {} writeData called path = {}", identifier, path);
 596             }
 597             recordedOperationFutures.add(actorContext.executeRemoteOperationAsync(getActor(),
 598                     new WriteData(path, data, schemaContext).toSerializable()));
 599         }
 600
 601         @Override
 602         public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
 603                 final YangInstanceIdentifier path) {
 604
 605             if(LOG.isDebugEnabled()) {
 606                 LOG.debug("Tx {} readData called path = {}", identifier, path);
 607             }
 608             final SettableFuture<Optional<NormalizedNode<?, ?>>> returnFuture = SettableFuture.create();
 609
 610             // If there were any previous recorded put/merge/delete operation reply Futures then we
 611             // must wait for them to successfully complete. This is necessary to honor the read
 612             // uncommitted semantics of the public API contract. If any one fails then fail the read.
 613
 614             if(recordedOperationFutures.isEmpty()) {
 615                 finishReadData(path, returnFuture);
 616             } else {
 617                 if(LOG.isDebugEnabled()) {
 618                     LOG.debug("Tx {} readData: verifying {} previous recorded operations",
 619                         identifier, recordedOperationFutures.size());
 620                 }
 621                 // Note: we make a copy of recordedOperationFutures to be on the safe side in case
 622                 // Futures#sequence accesses the passed List on a different thread, as
 623                 // recordedOperationFutures is not synchronized.
 624
 625                 Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(
 626                         Lists.newArrayList(recordedOperationFutures),
 627                         actorContext.getActorSystem().dispatcher());
 628                 OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 629                     @Override
 630                     public void onComplete(Throwable failure, Iterable<Object> notUsed)
 631                             throws Throwable {
 632                         if(failure != null) {
 633                             if(LOG.isDebugEnabled()) {
 634                                 LOG.debug("Tx {} readData: a recorded operation failed: {}",
 635                                     identifier, failure);
 636                             }
 637                             returnFuture.setException(new ReadFailedException(
 638                                     "The read could not be performed because a previous put, merge,"
 639                                     + "or delete operation failed", failure));
 640                         } else {
 641                             finishReadData(path, returnFuture);
 642                         }
 643                     }
 644                 };
 645
 646                 combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 647             }
 648
 649             return MappingCheckedFuture.create(returnFuture, ReadFailedException.MAPPER);
 650         }
 651
 652         private void finishReadData(final YangInstanceIdentifier path,
 653                 final SettableFuture<Optional<NormalizedNode<?, ?>>> returnFuture) {
 654
 655             if(LOG.isDebugEnabled()) {
 656                 LOG.debug("Tx {} finishReadData called path = {}", identifier, path);
 657             }
 658             OnComplete<Object> onComplete = new OnComplete<Object>() {
 659                 @Override
 660                 public void onComplete(Throwable failure, Object readResponse) throws Throwable {
 661                     if(failure != null) {
 662                         if(LOG.isDebugEnabled()) {
 663                             LOG.debug("Tx {} read operation failed: {}", identifier, failure);
 664                         }
 665                         returnFuture.setException(new ReadFailedException(
 666                                 "Error reading data for path " + path, failure));
 667
 668                     } else {
 669                         if(LOG.isDebugEnabled()) {
 670                             LOG.debug("Tx {} read operation succeeded", identifier, failure);
 671                         }
 672                         if (readResponse.getClass().equals(ReadDataReply.SERIALIZABLE_CLASS)) {
 673                             ReadDataReply reply = ReadDataReply.fromSerializable(schemaContext,
 674                                     path, readResponse);
 675                             if (reply.getNormalizedNode() == null) {
 676                                 returnFuture.set(Optional.<NormalizedNode<?, ?>>absent());
 677                             } else {
 678                                 returnFuture.set(Optional.<NormalizedNode<?, ?>>of(
 679                                         reply.getNormalizedNode()));
 680                             }
 681                         } else {
 682                             returnFuture.setException(new ReadFailedException(
 683                                     "Invalid response reading data for path " + path));
 684                         }
 685                     }
 686                 }
 687             };
 688
 689             Future<Object> readFuture = actorContext.executeRemoteOperationAsync(getActor(),
 690                     new ReadData(path).toSerializable());
 691             readFuture.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 692         }
 693
 694         @Override
 695         public CheckedFuture<Boolean, ReadFailedException> dataExists(
 696                 final YangInstanceIdentifier path) {
 697
 698             if(LOG.isDebugEnabled()) {
 699                 LOG.debug("Tx {} dataExists called path = {}", identifier, path);
 700             }
 701             final SettableFuture<Boolean> returnFuture = SettableFuture.create();
 702
 703             // If there were any previous recorded put/merge/delete operation reply Futures then we
 704             // must wait for them to successfully complete. This is necessary to honor the read
 705             // uncommitted semantics of the public API contract. If any one fails then fail this
 706             // request.
 707
 708             if(recordedOperationFutures.isEmpty()) {
 709                 finishDataExists(path, returnFuture);
 710             } else {
 711                 if(LOG.isDebugEnabled()) {
 712                     LOG.debug("Tx {} dataExists: verifying {} previous recorded operations",
 713                         identifier, recordedOperationFutures.size());
 714                 }
 715                 // Note: we make a copy of recordedOperationFutures to be on the safe side in case
 716                 // Futures#sequence accesses the passed List on a different thread, as
 717                 // recordedOperationFutures is not synchronized.
 718
 719                 Future<Iterable<Object>> combinedFutures = akka.dispatch.Futures.sequence(
 720                         Lists.newArrayList(recordedOperationFutures),
 721                         actorContext.getActorSystem().dispatcher());
 722                 OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 723                     @Override
 724                     public void onComplete(Throwable failure, Iterable<Object> notUsed)
 725                             throws Throwable {
 726                         if(failure != null) {
 727                             if(LOG.isDebugEnabled()) {
 728                                 LOG.debug("Tx {} dataExists: a recorded operation failed: {}",
 729                                     identifier, failure);
 730                             }
 731                             returnFuture.setException(new ReadFailedException(
 732                                     "The data exists could not be performed because a previous "
 733                                     + "put, merge, or delete operation failed", failure));
 734                         } else {
 735                             finishDataExists(path, returnFuture);
 736                         }
 737                     }
 738                 };
 739
 740                 combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 741             }
 742
 743             return MappingCheckedFuture.create(returnFuture, ReadFailedException.MAPPER);
 744         }
 745
 746         private void finishDataExists(final YangInstanceIdentifier path,
 747                 final SettableFuture<Boolean> returnFuture) {
 748
 749             if(LOG.isDebugEnabled()) {
 750                 LOG.debug("Tx {} finishDataExists called path = {}", identifier, path);
 751             }
 752             OnComplete<Object> onComplete = new OnComplete<Object>() {
 753                 @Override
 754                 public void onComplete(Throwable failure, Object response) throws Throwable {
 755                     if(failure != null) {
 756                         if(LOG.isDebugEnabled()) {
 757                             LOG.debug("Tx {} dataExists operation failed: {}", identifier, failure);
 758                         }
 759                         returnFuture.setException(new ReadFailedException(
 760                                 "Error checking data exists for path " + path, failure));
 761                     } else {
 762                         if(LOG.isDebugEnabled()) {
 763                             LOG.debug("Tx {} dataExists operation succeeded", identifier, failure);
 764                         }
 765                         if (response.getClass().equals(DataExistsReply.SERIALIZABLE_CLASS)) {
 766                             returnFuture.set(Boolean.valueOf(DataExistsReply.
 767                                         fromSerializable(response).exists()));
 768                         } else {
 769                             returnFuture.setException(new ReadFailedException(
 770                                     "Invalid response checking exists for path " + path));
 771                         }
 772                     }
 773                 }
 774             };
 775
 776             Future<Object> future = actorContext.executeRemoteOperationAsync(getActor(),
 777                     new DataExists(path).toSerializable());
 778             future.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 779         }
 780     }
 781
 782     private static class NoOpTransactionContext extends AbstractTransactionContext {
 783
 784         private final Logger LOG = LoggerFactory.getLogger(NoOpTransactionContext.class);
 785
 786         private final Exception failure;
 787
 788         public NoOpTransactionContext(String shardName, Exception failure,
 789                 TransactionIdentifier identifier){
 790             super(shardName, identifier);
 791             this.failure = failure;
 792         }
 793
 794         @Override
 795         public void closeTransaction() {
 796             if(LOG.isDebugEnabled()) {
 797                 LOG.debug("NoOpTransactionContext {} closeTransaction called", identifier);
 798             }
 799         }
 800
 801         @Override
 802         public Future<ActorPath> readyTransaction() {
 803             if(LOG.isDebugEnabled()) {
 804                 LOG.debug("Tx {} readyTransaction called", identifier);
 805             }
 806             return akka.dispatch.Futures.failed(failure);
 807         }
 808
 809         @Override
 810         public void deleteData(YangInstanceIdentifier path) {
 811             if(LOG.isDebugEnabled()) {
 812                 LOG.debug("Tx {} deleteData called path = {}", identifier, path);
 813             }
 814         }
 815
 816         @Override
 817         public void mergeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 818             if(LOG.isDebugEnabled()) {
 819                 LOG.debug("Tx {} mergeData called path = {}", identifier, path);
 820             }
 821         }
 822
 823         @Override
 824         public void writeData(YangInstanceIdentifier path, NormalizedNode<?, ?> data) {
 825             if(LOG.isDebugEnabled()) {
 826                 LOG.debug("Tx {} writeData called path = {}", identifier, path);
 827             }
 828         }
 829
 830         @Override
 831         public CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> readData(
 832             YangInstanceIdentifier path) {
 833             if(LOG.isDebugEnabled()) {
 834                 LOG.debug("Tx {} readData called path = {}", identifier, path);
 835             }
 836             return Futures.immediateFailedCheckedFuture(new ReadFailedException(
 837                     "Error reading data for path " + path, failure));
 838         }
 839
 840         @Override
 841         public CheckedFuture<Boolean, ReadFailedException> dataExists(
 842             YangInstanceIdentifier path) {
 843             if(LOG.isDebugEnabled()) {
 844                 LOG.debug("Tx {} dataExists called path = {}", identifier, path);
 845             }
 846             return Futures.immediateFailedCheckedFuture(new ReadFailedException(
 847                     "Error checking exists for path " + path, failure));
 848         }
 849     }
 850 }