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                 message.getTransactionID());
 221         final CohortEntry cohortEntry = new CohortEntry(message.getTransactionID(), cohort);
 222         cohortCache.put(message.getTransactionID(), cohortEntry);
 223         cohortEntry.setDoImmediateCommit(message.isDoCommitOnReady());
 224
 225         if(!queueCohortEntry(cohortEntry, sender, shard)) {
 226             return;
 227         }
 228
 229         log.debug("{}: Applying local modifications for Tx {}", name, message.getTransactionID());
 230
 231         if (message.isDoCommitOnReady()) {
 232             cohortEntry.setReplySender(sender);
 233             cohortEntry.setShard(shard);
 234             handleCanCommit(cohortEntry);
 235         } else {
 236             sender.tell(readyTransactionReply(shard), shard.self());
 237         }
 238     }
 239
 240     private void handleCanCommit(CohortEntry cohortEntry) {
 241         String transactionID = cohortEntry.getTransactionID();
 242
 243         cohortEntry.updateLastAccessTime();
 244
 245         if(currentCohortEntry != null) {
 246             // There's already a Tx commit in progress so we can't process this entry yet - but it's in the
 247             // queue and will get processed after all prior entries complete.
 248
 249             if(log.isDebugEnabled()) {
 250                 log.debug("{}: Commit for Tx {} already in progress - skipping canCommit for {} for now",
 251                         name, currentCohortEntry.getTransactionID(), transactionID);
 252             }
 253
 254             return;
 255         }
 256
 257         // No Tx commit currently in progress - check if this entry is the next one in the queue, If so make
 258         // it the current entry and proceed with canCommit.
 259         // Purposely checking reference equality here.
 260         if(queuedCohortEntries.peek() == cohortEntry) {
 261             currentCohortEntry = queuedCohortEntries.poll();
 262             doCanCommit(currentCohortEntry);
 263         } else {
 264             if(log.isDebugEnabled()) {
 265                 log.debug("{}: Tx {} is the next pending canCommit - skipping {} for now",
 266                         name, queuedCohortEntries.peek().getTransactionID(), transactionID);
 267             }
 268         }
 269     }
 270
 271     /**
 272      * This method handles the canCommit phase for a transaction.
 273      *
 274      * @param transactionID the ID of the transaction to canCommit
 275      * @param sender the actor to which to send the response
 276      * @param shard the transaction's shard actor
 277      */
 278     void handleCanCommit(String transactionID, final ActorRef sender, final Shard shard) {
 279         // Lookup the cohort entry that was cached previously (or should have been) by
 280         // transactionReady (via the ForwardedReadyTransaction message).
 281         final CohortEntry cohortEntry = cohortCache.get(transactionID);
 282         if(cohortEntry == null) {
 283             // Either canCommit was invoked before ready(shouldn't happen)  or a long time passed
 284             // between canCommit and ready and the entry was expired from the cache.
 285             IllegalStateException ex = new IllegalStateException(
 286                     String.format("%s: No cohort entry found for transaction %s", name, transactionID));
 287             log.error(ex.getMessage());
 288             sender.tell(new Status.Failure(ex), shard.self());
 289             return;
 290         }
 291
 292         cohortEntry.setReplySender(sender);
 293         cohortEntry.setShard(shard);
 294
 295         handleCanCommit(cohortEntry);
 296     }
 297
 298     private void doCanCommit(final CohortEntry cohortEntry) {
 299         boolean canCommit = false;
 300         try {
 301             // We block on the future here so we don't have to worry about possibly accessing our
 302             // state on a different thread outside of our dispatcher. Also, the data store
 303             // currently uses a same thread executor anyway.
 304             canCommit = cohortEntry.getCohort().canCommit().get();
 305
 306             log.debug("{}: canCommit for {}: {}", name, cohortEntry.getTransactionID(), canCommit);
 307
 308             if(cohortEntry.isDoImmediateCommit()) {
 309                 if(canCommit) {
 310                     doCommit(cohortEntry);
 311                 } else {
 312                     cohortEntry.getReplySender().tell(new Status.Failure(new TransactionCommitFailedException(
 313                                 "Can Commit failed, no detailed cause available.")), cohortEntry.getShard().self());
 314                 }
 315             } else {
 316                 cohortEntry.getReplySender().tell(
 317                         canCommit ? CanCommitTransactionReply.YES.toSerializable() :
 318                             CanCommitTransactionReply.NO.toSerializable(), cohortEntry.getShard().self());
 319             }
 320         } catch (Exception e) {
 321             log.debug("{}: An exception occurred during canCommit", name, e);
 322
 323             Throwable failure = e;
 324             if(e instanceof ExecutionException) {
 325                 failure = e.getCause();
 326             }
 327
 328             cohortEntry.getReplySender().tell(new Status.Failure(failure), cohortEntry.getShard().self());
 329         } finally {
 330             if(!canCommit) {
 331                 // Remove the entry from the cache now.
 332                 currentTransactionComplete(cohortEntry.getTransactionID(), true);
 333             }
 334         }
 335     }
 336
 337     private boolean doCommit(CohortEntry cohortEntry) {
 338         log.debug("{}: Committing transaction {}", name, cohortEntry.getTransactionID());
 339
 340         boolean success = false;
 341
 342         // We perform the preCommit phase here atomically with the commit phase. This is an
 343         // optimization to eliminate the overhead of an extra preCommit message. We lose front-end
 344         // coordination of preCommit across shards in case of failure but preCommit should not
 345         // normally fail since we ensure only one concurrent 3-phase commit.
 346
 347         try {
 348             // We block on the future here so we don't have to worry about possibly accessing our
 349             // state on a different thread outside of our dispatcher. Also, the data store
 350             // currently uses a same thread executor anyway.
 351             cohortEntry.getCohort().preCommit().get();
 352
 353             cohortEntry.getShard().continueCommit(cohortEntry);
 354
 355             cohortEntry.updateLastAccessTime();
 356
 357             success = true;
 358         } catch (Exception e) {
 359             log.error("{} An exception occurred while preCommitting transaction {}",
 360                     name, cohortEntry.getTransactionID(), e);
 361             cohortEntry.getReplySender().tell(new akka.actor.Status.Failure(e), cohortEntry.getShard().self());
 362
 363             currentTransactionComplete(cohortEntry.getTransactionID(), true);
 364         }
 365
 366         return success;
 367     }
 368
 369     /**
 370      * This method handles the preCommit and commit phases for a transaction.
 371      *
 372      * @param transactionID the ID of the transaction to commit
 373      * @param sender the actor to which to send the response
 374      * @param shard the transaction's shard actor
 375      * @return true if the transaction was successfully prepared, false otherwise.
 376      */
 377     boolean handleCommit(final String transactionID, final ActorRef sender, final Shard shard) {
 378         // Get the current in-progress cohort entry in the commitCoordinator if it corresponds to
 379         // this transaction.
 380         final CohortEntry cohortEntry = getCohortEntryIfCurrent(transactionID);
 381         if(cohortEntry == null) {
 382             // We're not the current Tx - the Tx was likely expired b/c it took too long in
 383             // between the canCommit and commit messages.
 384             IllegalStateException ex = new IllegalStateException(
 385                     String.format("%s: Cannot commit transaction %s - it is not the current transaction",
 386                             name, transactionID));
 387             log.error(ex.getMessage());
 388             sender.tell(new akka.actor.Status.Failure(ex), shard.self());
 389             return false;
 390         }
 391
 392         cohortEntry.setReplySender(sender);
 393         return doCommit(cohortEntry);
 394     }
 395
 396     /**
 397      * Returns the cohort entry for the Tx commit currently in progress if the given transaction ID
 398      * matches the current entry.
 399      *
 400      * @param transactionID the ID of the transaction
 401      * @return the current CohortEntry or null if the given transaction ID does not match the
 402      *         current entry.
 403      */
 404     public CohortEntry getCohortEntryIfCurrent(String transactionID) {
 405         if(isCurrentTransaction(transactionID)) {
 406             return currentCohortEntry;
 407         }
 408
 409         return null;
 410     }
 411
 412     public CohortEntry getCurrentCohortEntry() {
 413         return currentCohortEntry;
 414     }
 415
 416     public CohortEntry getAndRemoveCohortEntry(String transactionID) {
 417         return cohortCache.remove(transactionID);
 418     }
 419
 420     public boolean isCurrentTransaction(String transactionID) {
 421         return currentCohortEntry != null &&
 422                 currentCohortEntry.getTransactionID().equals(transactionID);
 423     }
 424
 425     /**
 426      * This method is called when a transaction is complete, successful or not. If the given
 427      * given transaction ID matches the current in-progress transaction, the next cohort entry,
 428      * if any, is dequeued and processed.
 429      *
 430      * @param transactionID the ID of the completed transaction
 431      * @param removeCohortEntry if true the CohortEntry for the transaction is also removed from
 432      *        the cache.
 433      */
 434     public void currentTransactionComplete(String transactionID, boolean removeCohortEntry) {
 435         if(removeCohortEntry) {
 436             cohortCache.remove(transactionID);
 437         }
 438
 439         if(isCurrentTransaction(transactionID)) {
 440             currentCohortEntry = null;
 441
 442             log.debug("{}: currentTransactionComplete: {}", name, transactionID);
 443
 444             maybeProcessNextCohortEntry();
 445         }
 446     }
 447
 448     private void maybeProcessNextCohortEntry() {
 449         // Check if there's a next cohort entry waiting in the queue and if it is ready to commit. Also
 450         // clean out expired entries.
 451         Iterator<CohortEntry> iter = queuedCohortEntries.iterator();
 452         while(iter.hasNext()) {
 453             CohortEntry next = iter.next();
 454             if(next.isReadyToCommit()) {
 455                 if(currentCohortEntry == null) {
 456                     if(log.isDebugEnabled()) {
 457                         log.debug("{}: Next entry to canCommit {}", name, next);
 458                     }
 459
 460                     iter.remove();
 461                     currentCohortEntry = next;
 462                     currentCohortEntry.updateLastAccessTime();
 463                     doCanCommit(currentCohortEntry);
 464                 }
 465
 466                 break;
 467             } else if(next.isExpired(cacheExpiryTimeoutInMillis)) {
 468                 log.warn("{}: canCommit for transaction {} was not received within {} ms - entry removed from cache",
 469                         name, next.getTransactionID(), cacheExpiryTimeoutInMillis);
 470
 471                 iter.remove();
 472                 cohortCache.remove(next.getTransactionID());
 473             } else {
 474                 break;
 475             }
 476         }
 477     }
 478
 479     void cleanupExpiredCohortEntries() {
 480         maybeProcessNextCohortEntry();
 481     }
 482
 483     @VisibleForTesting
 484     void setCohortDecorator(CohortDecorator cohortDecorator) {
 485         this.cohortDecorator = cohortDecorator;
 486     }
 487
 488     static class CohortEntry {
 489         private final String transactionID;
 490         private ShardDataTreeCohort cohort;
 491         private final ReadWriteShardDataTreeTransaction transaction;
 492         private ActorRef replySender;
 493         private Shard shard;
 494         private boolean doImmediateCommit;
 495         private final Stopwatch lastAccessTimer = Stopwatch.createStarted();
 496
 497         CohortEntry(String transactionID, ReadWriteShardDataTreeTransaction transaction) {
 498             this.transaction = Preconditions.checkNotNull(transaction);
 499             this.transactionID = transactionID;
 500         }
 501
 502         CohortEntry(String transactionID, ShardDataTreeCohort cohort,
 503                 MutableCompositeModification compositeModification) {
 504             this.transactionID = transactionID;
 505             this.cohort = cohort;
 506             this.transaction = null;
 507         }
 508
 509         CohortEntry(String transactionID, ShardDataTreeCohort cohort) {
 510             this.transactionID = transactionID;
 511             this.cohort = cohort;
 512             this.transaction = null;
 513         }
 514
 515         void updateLastAccessTime() {
 516             lastAccessTimer.reset();
 517             lastAccessTimer.start();
 518         }
 519
 520         String getTransactionID() {
 521             return transactionID;
 522         }
 523
 524         ShardDataTreeCohort getCohort() {
 525             return cohort;
 526         }
 527
 528         void applyModifications(Iterable<Modification> modifications) {
 529             for (Modification modification : modifications) {
 530                 modification.apply(transaction.getSnapshot());
 531             }
 532         }
 533
 534         void ready(CohortDecorator cohortDecorator, boolean doImmediateCommit) {
 535             Preconditions.checkState(cohort == null, "cohort was already set");
 536
 537             setDoImmediateCommit(doImmediateCommit);
 538
 539             cohort = transaction.ready();
 540
 541             if(cohortDecorator != null) {
 542                 // Call the hook for unit tests.
 543                 cohort = cohortDecorator.decorate(transactionID, cohort);
 544             }
 545         }
 546
 547         boolean isReadyToCommit() {
 548             return replySender != null;
 549         }
 550
 551         boolean isExpired(long expireTimeInMillis) {
 552             return lastAccessTimer.elapsed(TimeUnit.MILLISECONDS) >= expireTimeInMillis;
 553         }
 554
 555         boolean isDoImmediateCommit() {
 556             return doImmediateCommit;
 557         }
 558
 559         void setDoImmediateCommit(boolean doImmediateCommit) {
 560             this.doImmediateCommit = doImmediateCommit;
 561         }
 562
 563         ActorRef getReplySender() {
 564             return replySender;
 565         }
 566
 567         void setReplySender(ActorRef replySender) {
 568             this.replySender = replySender;
 569         }
 570
 571         Shard getShard() {
 572             return shard;
 573         }
 574
 575         void setShard(Shard shard) {
 576             this.shard = shard;
 577         }
 578
 579         @Override
 580         public String toString() {
 581             StringBuilder builder = new StringBuilder();
 582             builder.append("CohortEntry [transactionID=").append(transactionID).append(", doImmediateCommit=")
 583                     .append(doImmediateCommit).append("]");
 584             return builder.toString();
 585         }
 586     }
 587 }