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

   1 /*
   2  * Copyright (c) 2014 Brocade Communications Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.controller.cluster.datastore;
   9
  10 import akka.actor.ActorRef;
  11 import akka.actor.Status;
  12 import akka.serialization.Serialization;
  13 import com.google.common.annotations.VisibleForTesting;
  14 import com.google.common.base.Preconditions;
  15 import com.google.common.cache.Cache;
  16 import com.google.common.cache.CacheBuilder;
  17 import com.google.common.cache.RemovalCause;
  18 import com.google.common.cache.RemovalListener;
  19 import com.google.common.cache.RemovalNotification;
  20 import java.util.LinkedList;
  21 import java.util.Queue;
  22 import java.util.concurrent.ExecutionException;
  23 import java.util.concurrent.TimeUnit;
  24 import org.opendaylight.controller.cluster.datastore.compat.BackwardsCompatibleThreePhaseCommitCohort;
  25 import org.opendaylight.controller.cluster.datastore.messages.BatchedModifications;
  26 import org.opendaylight.controller.cluster.datastore.messages.BatchedModificationsReply;
  27 import org.opendaylight.controller.cluster.datastore.messages.CanCommitTransactionReply;
  28 import org.opendaylight.controller.cluster.datastore.messages.ForwardedReadyTransaction;
  29 import org.opendaylight.controller.cluster.datastore.messages.ReadyTransactionReply;
  30 import org.opendaylight.controller.cluster.datastore.modification.Modification;
  31 import org.opendaylight.controller.cluster.datastore.modification.MutableCompositeModification;
  32 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
  33 import org.opendaylight.controller.sal.core.spi.data.DOMStoreThreePhaseCommitCohort;
  34 import org.slf4j.Logger;
  35
  36 /**
  37  * Coordinates commits for a shard ensuring only one concurrent 3-phase commit.
  38  *
  39  * @author Thomas Pantelis
  40  */
  41 public class ShardCommitCoordinator {
  42
  43     // Interface hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
  44     public interface CohortDecorator {
  45         DOMStoreThreePhaseCommitCohort decorate(String transactionID, DOMStoreThreePhaseCommitCohort actual);
  46     }
  47
  48     private final Cache<String, CohortEntry> cohortCache;
  49
  50     private CohortEntry currentCohortEntry;
  51
  52     private final ShardDataTree dataTree;
  53
  54     private final Queue<CohortEntry> queuedCohortEntries;
  55
  56     private int queueCapacity;
  57
  58     private final Logger log;
  59
  60     private final String name;
  61
  62     private final RemovalListener<String, CohortEntry> cacheRemovalListener =
  63             new RemovalListener<String, CohortEntry>() {
  64                 @Override
  65                 public void onRemoval(RemovalNotification<String, CohortEntry> notification) {
  66                     if(notification.getCause() == RemovalCause.EXPIRED) {
  67                         log.warn("{}: Transaction {} was timed out of the cache", name, notification.getKey());
  68                     }
  69                 }
  70             };
  71
  72     // This is a hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
  73     private CohortDecorator cohortDecorator;
  74
  75     private ReadyTransactionReply readyTransactionReply;
  76
  77     public ShardCommitCoordinator(ShardDataTree dataTree,
  78             long cacheExpiryTimeoutInSec, int queueCapacity, ActorRef shardActor, Logger log, String name) {
  79
  80         this.queueCapacity = queueCapacity;
  81         this.log = log;
  82         this.name = name;
  83         this.dataTree = Preconditions.checkNotNull(dataTree);
  84
  85         cohortCache = CacheBuilder.newBuilder().expireAfterAccess(cacheExpiryTimeoutInSec, TimeUnit.SECONDS).
  86                 removalListener(cacheRemovalListener).build();
  87
  88         // We use a LinkedList here to avoid synchronization overhead with concurrent queue impls
  89         // since this should only be accessed on the shard's dispatcher.
  90         queuedCohortEntries = new LinkedList<>();
  91     }
  92
  93     public void setQueueCapacity(int queueCapacity) {
  94         this.queueCapacity = queueCapacity;
  95     }
  96
  97     private ReadyTransactionReply readyTransactionReply(Shard shard) {
  98         if(readyTransactionReply == null) {
  99             readyTransactionReply = new ReadyTransactionReply(Serialization.serializedActorPath(shard.self()));
 100         }
 101
 102         return readyTransactionReply;
 103     }
 104
 105     /**
 106      * This method is called to ready a transaction that was prepared by ShardTransaction actor. It caches
 107      * the prepared cohort entry for the given transactions ID in preparation for the subsequent 3-phase commit.
 108      */
 109     public void handleForwardedReadyTransaction(ForwardedReadyTransaction ready, ActorRef sender, Shard shard) {
 110         log.debug("{}: Readying transaction {}, client version {}", name,
 111                 ready.getTransactionID(), ready.getTxnClientVersion());
 112
 113         CohortEntry cohortEntry = new CohortEntry(ready.getTransactionID(), ready.getCohort(),
 114                 (MutableCompositeModification) ready.getModification());
 115         cohortCache.put(ready.getTransactionID(), cohortEntry);
 116
 117         if(ready.getTxnClientVersion() < DataStoreVersions.LITHIUM_VERSION) {
 118             // Return our actor path as we'll handle the three phase commit except if the Tx client
 119             // version < Helium-1 version which means the Tx was initiated by a base Helium version node.
 120             // In that case, the subsequent 3-phase commit messages won't contain the transactionId so to
 121             // maintain backwards compatibility, we create a separate cohort actor to provide the compatible behavior.
 122             ActorRef replyActorPath = shard.self();
 123             if(ready.getTxnClientVersion() < DataStoreVersions.HELIUM_1_VERSION) {
 124                 log.debug("{}: Creating BackwardsCompatibleThreePhaseCommitCohort", name);
 125                 replyActorPath = shard.getContext().actorOf(BackwardsCompatibleThreePhaseCommitCohort.props(
 126                         ready.getTransactionID()));
 127             }
 128
 129             ReadyTransactionReply readyTransactionReply =
 130                     new ReadyTransactionReply(Serialization.serializedActorPath(replyActorPath),
 131                             ready.getTxnClientVersion());
 132             sender.tell(ready.isReturnSerialized() ? readyTransactionReply.toSerializable() :
 133                 readyTransactionReply, shard.self());
 134         } else {
 135             if(ready.isDoImmediateCommit()) {
 136                 cohortEntry.setDoImmediateCommit(true);
 137                 cohortEntry.setReplySender(sender);
 138                 cohortEntry.setShard(shard);
 139                 handleCanCommit(cohortEntry);
 140             } else {
 141                 // The caller does not want immediate commit - the 3-phase commit will be coordinated by the
 142                 // front-end so send back a ReadyTransactionReply with our actor path.
 143                 sender.tell(readyTransactionReply(shard), shard.self());
 144             }
 145         }
 146     }
 147
 148     /**
 149      * This method handles a BatchedModifications message for a transaction being prepared directly on the
 150      * Shard actor instead of via a ShardTransaction actor. If there's no currently cached
 151      * DOMStoreWriteTransaction, one is created. The batched modifications are applied to the write Tx. If
 152      * the BatchedModifications is ready to commit then a DOMStoreThreePhaseCommitCohort is created.
 153      *
 154      * @param batched the BatchedModifications
 155      * @param shardActor the transaction's shard actor
 156      *
 157      * @throws ExecutionException if an error occurs loading the cache
 158      */
 159     boolean handleBatchedModifications(BatchedModifications batched, ActorRef sender, Shard shard)
 160             throws ExecutionException {
 161         CohortEntry cohortEntry = cohortCache.getIfPresent(batched.getTransactionID());
 162         if(cohortEntry == null) {
 163             cohortEntry = new CohortEntry(batched.getTransactionID(),
 164                     dataTree.newReadWriteTransaction(batched.getTransactionID(),
 165                         batched.getTransactionChainID()));
 166             cohortCache.put(batched.getTransactionID(), cohortEntry);
 167         }
 168
 169         if(log.isDebugEnabled()) {
 170             log.debug("{}: Applying {} batched modifications for Tx {}", name,
 171                     batched.getModifications().size(), batched.getTransactionID());
 172         }
 173
 174         cohortEntry.applyModifications(batched.getModifications());
 175
 176         if(batched.isReady()) {
 177             if(log.isDebugEnabled()) {
 178                 log.debug("{}: Readying Tx {}, client version {}", name,
 179                         batched.getTransactionID(), batched.getVersion());
 180             }
 181
 182             cohortEntry.ready(cohortDecorator, batched.isDoCommitOnReady());
 183
 184             if(batched.isDoCommitOnReady()) {
 185                 cohortEntry.setReplySender(sender);
 186                 cohortEntry.setShard(shard);
 187                 handleCanCommit(cohortEntry);
 188             } else {
 189                 sender.tell(readyTransactionReply(shard), shard.self());
 190             }
 191         } else {
 192             sender.tell(new BatchedModificationsReply(batched.getModifications().size()), shard.self());
 193         }
 194
 195         return batched.isReady();
 196     }
 197
 198     private void handleCanCommit(CohortEntry cohortEntry) {
 199         String transactionID = cohortEntry.getTransactionID();
 200
 201         if(log.isDebugEnabled()) {
 202             log.debug("{}: Processing canCommit for transaction {} for shard {}",
 203                     name, transactionID, cohortEntry.getShard().self().path());
 204         }
 205
 206         if(currentCohortEntry != null) {
 207             // There's already a Tx commit in progress - attempt to queue this entry to be
 208             // committed after the current Tx completes.
 209             log.debug("{}: Transaction {} is already in progress - queueing transaction {}",
 210                     name, currentCohortEntry.getTransactionID(), transactionID);
 211
 212             if(queuedCohortEntries.size() < queueCapacity) {
 213                 queuedCohortEntries.offer(cohortEntry);
 214             } else {
 215                 removeCohortEntry(transactionID);
 216
 217                 RuntimeException ex = new RuntimeException(
 218                         String.format("%s: Could not enqueue transaction %s - the maximum commit queue"+
 219                                       " capacity %d has been reached.",
 220                                       name, transactionID, queueCapacity));
 221                 log.error(ex.getMessage());
 222                 cohortEntry.getReplySender().tell(new Status.Failure(ex), cohortEntry.getShard().self());
 223             }
 224         } else {
 225             // No Tx commit currently in progress - make this the current entry and proceed with
 226             // canCommit.
 227             cohortEntry.updateLastAccessTime();
 228             currentCohortEntry = cohortEntry;
 229
 230             doCanCommit(cohortEntry);
 231         }
 232     }
 233
 234     /**
 235      * This method handles the canCommit phase for a transaction.
 236      *
 237      * @param canCommit the CanCommitTransaction message
 238      * @param sender the actor that sent the message
 239      * @param shard the transaction's shard actor
 240      */
 241     public void handleCanCommit(String transactionID, final ActorRef sender, final Shard shard) {
 242         // Lookup the cohort entry that was cached previously (or should have been) by
 243         // transactionReady (via the ForwardedReadyTransaction message).
 244         final CohortEntry cohortEntry = cohortCache.getIfPresent(transactionID);
 245         if(cohortEntry == null) {
 246             // Either canCommit was invoked before ready(shouldn't happen)  or a long time passed
 247             // between canCommit and ready and the entry was expired from the cache.
 248             IllegalStateException ex = new IllegalStateException(
 249                     String.format("%s: No cohort entry found for transaction %s", name, transactionID));
 250             log.error(ex.getMessage());
 251             sender.tell(new Status.Failure(ex), shard.self());
 252             return;
 253         }
 254
 255         cohortEntry.setReplySender(sender);
 256         cohortEntry.setShard(shard);
 257
 258         handleCanCommit(cohortEntry);
 259     }
 260
 261     private void doCanCommit(final CohortEntry cohortEntry) {
 262
 263         boolean canCommit = false;
 264         try {
 265             // We block on the future here so we don't have to worry about possibly accessing our
 266             // state on a different thread outside of our dispatcher. Also, the data store
 267             // currently uses a same thread executor anyway.
 268             canCommit = cohortEntry.getCohort().canCommit().get();
 269
 270             if(cohortEntry.isDoImmediateCommit()) {
 271                 if(canCommit) {
 272                     doCommit(cohortEntry);
 273                 } else {
 274                     cohortEntry.getReplySender().tell(new Status.Failure(new TransactionCommitFailedException(
 275                                 "Can Commit failed, no detailed cause available.")), cohortEntry.getShard().self());
 276                 }
 277             } else {
 278                 cohortEntry.getReplySender().tell(
 279                         canCommit ? CanCommitTransactionReply.YES.toSerializable() :
 280                             CanCommitTransactionReply.NO.toSerializable(), cohortEntry.getShard().self());
 281             }
 282         } catch (Exception e) {
 283             log.debug("{}: An exception occurred during canCommit: {}", name, e);
 284
 285             Throwable failure = e;
 286             if(e instanceof ExecutionException) {
 287                 failure = e.getCause();
 288             }
 289
 290             cohortEntry.getReplySender().tell(new Status.Failure(failure), cohortEntry.getShard().self());
 291         } finally {
 292             if(!canCommit) {
 293                 // Remove the entry from the cache now.
 294                 currentTransactionComplete(cohortEntry.getTransactionID(), true);
 295             }
 296         }
 297     }
 298
 299     private boolean doCommit(CohortEntry cohortEntry) {
 300         log.debug("{}: Committing transaction {}", name, cohortEntry.getTransactionID());
 301
 302         boolean success = false;
 303
 304         // We perform the preCommit phase here atomically with the commit phase. This is an
 305         // optimization to eliminate the overhead of an extra preCommit message. We lose front-end
 306         // coordination of preCommit across shards in case of failure but preCommit should not
 307         // normally fail since we ensure only one concurrent 3-phase commit.
 308
 309         try {
 310             // We block on the future here so we don't have to worry about possibly accessing our
 311             // state on a different thread outside of our dispatcher. Also, the data store
 312             // currently uses a same thread executor anyway.
 313             cohortEntry.getCohort().preCommit().get();
 314
 315             cohortEntry.getShard().continueCommit(cohortEntry);
 316
 317             cohortEntry.updateLastAccessTime();
 318
 319             success = true;
 320         } catch (Exception e) {
 321             log.error("{} An exception occurred while preCommitting transaction {}",
 322                     name, cohortEntry.getTransactionID(), e);
 323             cohortEntry.getReplySender().tell(new akka.actor.Status.Failure(e), cohortEntry.getShard().self());
 324
 325             currentTransactionComplete(cohortEntry.getTransactionID(), true);
 326         }
 327
 328         return success;
 329     }
 330
 331     boolean handleCommit(final String transactionID, final ActorRef sender, final Shard shard) {
 332         // Get the current in-progress cohort entry in the commitCoordinator if it corresponds to
 333         // this transaction.
 334         final CohortEntry cohortEntry = getCohortEntryIfCurrent(transactionID);
 335         if(cohortEntry == null) {
 336             // We're not the current Tx - the Tx was likely expired b/c it took too long in
 337             // between the canCommit and commit messages.
 338             IllegalStateException ex = new IllegalStateException(
 339                     String.format("%s: Cannot commit transaction %s - it is not the current transaction",
 340                             name, transactionID));
 341             log.error(ex.getMessage());
 342             sender.tell(new akka.actor.Status.Failure(ex), shard.self());
 343             return false;
 344         }
 345
 346         return doCommit(cohortEntry);
 347     }
 348
 349     /**
 350      * Returns the cohort entry for the Tx commit currently in progress if the given transaction ID
 351      * matches the current entry.
 352      *
 353      * @param transactionID the ID of the transaction
 354      * @return the current CohortEntry or null if the given transaction ID does not match the
 355      *         current entry.
 356      */
 357     public CohortEntry getCohortEntryIfCurrent(String transactionID) {
 358         if(isCurrentTransaction(transactionID)) {
 359             return currentCohortEntry;
 360         }
 361
 362         return null;
 363     }
 364
 365     public CohortEntry getCurrentCohortEntry() {
 366         return currentCohortEntry;
 367     }
 368
 369     public CohortEntry getAndRemoveCohortEntry(String transactionID) {
 370         CohortEntry cohortEntry = cohortCache.getIfPresent(transactionID);
 371         cohortCache.invalidate(transactionID);
 372         return cohortEntry;
 373     }
 374
 375     public void removeCohortEntry(String transactionID) {
 376         cohortCache.invalidate(transactionID);
 377     }
 378
 379     public boolean isCurrentTransaction(String transactionID) {
 380         return currentCohortEntry != null &&
 381                 currentCohortEntry.getTransactionID().equals(transactionID);
 382     }
 383
 384     /**
 385      * This method is called when a transaction is complete, successful or not. If the given
 386      * given transaction ID matches the current in-progress transaction, the next cohort entry,
 387      * if any, is dequeued and processed.
 388      *
 389      * @param transactionID the ID of the completed transaction
 390      * @param removeCohortEntry if true the CohortEntry for the transaction is also removed from
 391      *        the cache.
 392      */
 393     public void currentTransactionComplete(String transactionID, boolean removeCohortEntry) {
 394         if(removeCohortEntry) {
 395             removeCohortEntry(transactionID);
 396         }
 397
 398         if(isCurrentTransaction(transactionID)) {
 399             // Dequeue the next cohort entry waiting in the queue.
 400             currentCohortEntry = queuedCohortEntries.poll();
 401             if(currentCohortEntry != null) {
 402                 currentCohortEntry.updateLastAccessTime();
 403                 doCanCommit(currentCohortEntry);
 404             }
 405         }
 406     }
 407
 408     @VisibleForTesting
 409     void setCohortDecorator(CohortDecorator cohortDecorator) {
 410         this.cohortDecorator = cohortDecorator;
 411     }
 412
 413
 414     static class CohortEntry {
 415         private final String transactionID;
 416         private DOMStoreThreePhaseCommitCohort cohort;
 417         private final MutableCompositeModification compositeModification;
 418         private final ReadWriteShardDataTreeTransaction transaction;
 419         private ActorRef replySender;
 420         private Shard shard;
 421         private long lastAccessTime;
 422         private boolean doImmediateCommit;
 423
 424         CohortEntry(String transactionID, ReadWriteShardDataTreeTransaction transaction) {
 425             this.compositeModification = new MutableCompositeModification();
 426             this.transaction = Preconditions.checkNotNull(transaction);
 427             this.transactionID = transactionID;
 428         }
 429
 430         CohortEntry(String transactionID, DOMStoreThreePhaseCommitCohort cohort,
 431                 MutableCompositeModification compositeModification) {
 432             this.transactionID = transactionID;
 433             this.cohort = cohort;
 434             this.compositeModification = compositeModification;
 435             this.transaction = null;
 436         }
 437
 438         void updateLastAccessTime() {
 439             lastAccessTime = System.currentTimeMillis();
 440         }
 441
 442         long getLastAccessTime() {
 443             return lastAccessTime;
 444         }
 445
 446         String getTransactionID() {
 447             return transactionID;
 448         }
 449
 450         DOMStoreThreePhaseCommitCohort getCohort() {
 451             return cohort;
 452         }
 453
 454         MutableCompositeModification getModification() {
 455             return compositeModification;
 456         }
 457
 458         void applyModifications(Iterable<Modification> modifications) {
 459             for(Modification modification: modifications) {
 460                 compositeModification.addModification(modification);
 461                 modification.apply(transaction.getSnapshot());
 462             }
 463         }
 464
 465         void ready(CohortDecorator cohortDecorator, boolean doImmediateCommit) {
 466             Preconditions.checkState(cohort == null, "cohort was already set");
 467
 468             setDoImmediateCommit(doImmediateCommit);
 469
 470             cohort = transaction.ready();
 471
 472             if(cohortDecorator != null) {
 473                 // Call the hook for unit tests.
 474                 cohort = cohortDecorator.decorate(transactionID, cohort);
 475             }
 476         }
 477
 478         boolean isDoImmediateCommit() {
 479             return doImmediateCommit;
 480         }
 481
 482         void setDoImmediateCommit(boolean doImmediateCommit) {
 483             this.doImmediateCommit = doImmediateCommit;
 484         }
 485
 486         ActorRef getReplySender() {
 487             return replySender;
 488         }
 489
 490         void setReplySender(ActorRef replySender) {
 491             this.replySender = replySender;
 492         }
 493
 494         Shard getShard() {
 495             return shard;
 496         }
 497
 498         void setShard(Shard shard) {
 499             this.shard = shard;
 500         }
 501
 502         boolean hasModifications(){
 503             return compositeModification.getModifications().size() > 0;
 504         }
 505     }
 506 }