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

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