2 * Copyright (c) 2014 Brocade Communications Systems, Inc. and others. All rights reserved.
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
8 package org.opendaylight.controller.cluster.datastore;
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;
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;
36 * Coordinates commits for a shard ensuring only one concurrent 3-phase commit.
38 * @author Thomas Pantelis
40 class ShardCommitCoordinator {
42 // Interface hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
43 public interface CohortDecorator {
44 ShardDataTreeCohort decorate(String transactionID, ShardDataTreeCohort actual);
47 private final Map<String, CohortEntry> cohortCache = new HashMap<>();
49 private CohortEntry currentCohortEntry;
51 private final ShardDataTree dataTree;
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<>();
57 private int queueCapacity;
59 private final Logger log;
61 private final String name;
63 private final long cacheExpiryTimeoutInMillis;
65 // This is a hook for unit tests to replace or decorate the DOMStoreThreePhaseCommitCohorts.
66 private CohortDecorator cohortDecorator;
68 private ReadyTransactionReply readyTransactionReply;
70 ShardCommitCoordinator(ShardDataTree dataTree,
71 long cacheExpiryTimeoutInMillis, int queueCapacity, ActorRef shardActor, Logger log, String name) {
73 this.queueCapacity = queueCapacity;
76 this.dataTree = Preconditions.checkNotNull(dataTree);
77 this.cacheExpiryTimeoutInMillis = cacheExpiryTimeoutInMillis;
80 void setQueueCapacity(int queueCapacity) {
81 this.queueCapacity = queueCapacity;
84 private ReadyTransactionReply readyTransactionReply(Shard shard) {
85 if(readyTransactionReply == null) {
86 readyTransactionReply = new ReadyTransactionReply(Serialization.serializedActorPath(shard.self()));
89 return readyTransactionReply;
92 private boolean queueCohortEntry(CohortEntry cohortEntry, ActorRef sender, Shard shard) {
93 if(queuedCohortEntries.size() < queueCapacity) {
94 queuedCohortEntries.offer(cohortEntry);
97 cohortCache.remove(cohortEntry.getTransactionID());
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());
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.
113 * @param ready the ForwardedReadyTransaction message to process
114 * @param sender the sender of the message
115 * @param shard the transaction's shard actor
117 void handleForwardedReadyTransaction(ForwardedReadyTransaction ready, ActorRef sender, Shard shard) {
118 log.debug("{}: Readying transaction {}, client version {}", name,
119 ready.getTransactionID(), ready.getTxnClientVersion());
121 CohortEntry cohortEntry = new CohortEntry(ready.getTransactionID(), ready.getCohort(),
122 (MutableCompositeModification) ready.getModification());
123 cohortCache.put(ready.getTransactionID(), cohortEntry);
125 if(!queueCohortEntry(cohortEntry, sender, shard)) {
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()));
141 ReadyTransactionReply readyTransactionReply =
142 new ReadyTransactionReply(Serialization.serializedActorPath(replyActorPath),
143 ready.getTxnClientVersion());
144 sender.tell(ready.isReturnSerialized() ? readyTransactionReply.toSerializable() :
145 readyTransactionReply, shard.self());
147 if(ready.isDoImmediateCommit()) {
148 cohortEntry.setDoImmediateCommit(true);
149 cohortEntry.setReplySender(sender);
150 cohortEntry.setShard(shard);
151 handleCanCommit(cohortEntry);
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());
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.
166 * @param batched the BatchedModifications message to process
167 * @param sender the sender of the message
168 * @param shard the transaction's shard actor
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);
179 if(log.isDebugEnabled()) {
180 log.debug("{}: Applying {} batched modifications for Tx {}", name,
181 batched.getModifications().size(), batched.getTransactionID());
184 cohortEntry.applyModifications(batched.getModifications());
186 if(batched.isReady()) {
187 if(!queueCohortEntry(cohortEntry, sender, shard)) {
191 if(log.isDebugEnabled()) {
192 log.debug("{}: Readying Tx {}, client version {}", name,
193 batched.getTransactionID(), batched.getVersion());
196 cohortEntry.ready(cohortDecorator, batched.isDoCommitOnReady());
198 if(batched.isDoCommitOnReady()) {
199 cohortEntry.setReplySender(sender);
200 cohortEntry.setShard(shard);
201 handleCanCommit(cohortEntry);
203 sender.tell(readyTransactionReply(shard), shard.self());
206 sender.tell(new BatchedModificationsReply(batched.getModifications().size()), shard.self());
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.
214 * @param message the ReadyLocalTransaction message to process
215 * @param sender the sender of the message
216 * @param shard the transaction's shard actor
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());
224 if(!queueCohortEntry(cohortEntry, sender, shard)) {
228 log.debug("{}: Applying local modifications for Tx {}", name, message.getTransactionID());
230 if (message.isDoCommitOnReady()) {
231 cohortEntry.setReplySender(sender);
232 cohortEntry.setShard(shard);
233 handleCanCommit(cohortEntry);
235 sender.tell(readyTransactionReply(shard), shard.self());
239 private void handleCanCommit(CohortEntry cohortEntry) {
240 String transactionID = cohortEntry.getTransactionID();
242 cohortEntry.updateLastAccessTime();
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.
248 if(log.isDebugEnabled()) {
249 log.debug("{}: Commit for Tx {} already in progress - skipping canCommit for {} for now",
250 name, currentCohortEntry.getTransactionID(), transactionID);
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);
263 if(log.isDebugEnabled()) {
264 log.debug("{}: Tx {} is the next pending canCommit - skipping {} for now",
265 name, queuedCohortEntries.peek().getTransactionID(), transactionID);
271 * This method handles the canCommit phase for a transaction.
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
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());
291 cohortEntry.setReplySender(sender);
292 cohortEntry.setShard(shard);
294 handleCanCommit(cohortEntry);
297 private void doCanCommit(final CohortEntry cohortEntry) {
298 boolean canCommit = false;
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();
305 log.debug("{}: canCommit for {}: {}", name, cohortEntry.getTransactionID(), canCommit);
307 if(cohortEntry.isDoImmediateCommit()) {
309 doCommit(cohortEntry);
311 cohortEntry.getReplySender().tell(new Status.Failure(new TransactionCommitFailedException(
312 "Can Commit failed, no detailed cause available.")), cohortEntry.getShard().self());
315 cohortEntry.getReplySender().tell(
316 canCommit ? CanCommitTransactionReply.YES.toSerializable() :
317 CanCommitTransactionReply.NO.toSerializable(), cohortEntry.getShard().self());
319 } catch (Exception e) {
320 log.debug("{}: An exception occurred during canCommit", name, e);
322 Throwable failure = e;
323 if(e instanceof ExecutionException) {
324 failure = e.getCause();
327 cohortEntry.getReplySender().tell(new Status.Failure(failure), cohortEntry.getShard().self());
330 // Remove the entry from the cache now.
331 currentTransactionComplete(cohortEntry.getTransactionID(), true);
336 private boolean doCommit(CohortEntry cohortEntry) {
337 log.debug("{}: Committing transaction {}", name, cohortEntry.getTransactionID());
339 boolean success = false;
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.
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();
352 cohortEntry.getShard().continueCommit(cohortEntry);
354 cohortEntry.updateLastAccessTime();
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());
362 currentTransactionComplete(cohortEntry.getTransactionID(), true);
369 * This method handles the preCommit and commit phases for a transaction.
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.
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
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());
391 cohortEntry.setReplySender(sender);
392 return doCommit(cohortEntry);
396 * Returns the cohort entry for the Tx commit currently in progress if the given transaction ID
397 * matches the current entry.
399 * @param transactionID the ID of the transaction
400 * @return the current CohortEntry or null if the given transaction ID does not match the
403 public CohortEntry getCohortEntryIfCurrent(String transactionID) {
404 if(isCurrentTransaction(transactionID)) {
405 return currentCohortEntry;
411 public CohortEntry getCurrentCohortEntry() {
412 return currentCohortEntry;
415 public CohortEntry getAndRemoveCohortEntry(String transactionID) {
416 return cohortCache.remove(transactionID);
419 public boolean isCurrentTransaction(String transactionID) {
420 return currentCohortEntry != null &&
421 currentCohortEntry.getTransactionID().equals(transactionID);
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.
429 * @param transactionID the ID of the completed transaction
430 * @param removeCohortEntry if true the CohortEntry for the transaction is also removed from
433 public void currentTransactionComplete(String transactionID, boolean removeCohortEntry) {
434 if(removeCohortEntry) {
435 cohortCache.remove(transactionID);
438 if(isCurrentTransaction(transactionID)) {
439 currentCohortEntry = null;
441 log.debug("{}: currentTransactionComplete: {}", name, transactionID);
443 maybeProcessNextCohortEntry();
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);
460 currentCohortEntry = next;
461 currentCohortEntry.updateLastAccessTime();
462 doCanCommit(currentCohortEntry);
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);
471 cohortCache.remove(next.getTransactionID());
478 void cleanupExpiredCohortEntries() {
479 maybeProcessNextCohortEntry();
483 void setCohortDecorator(CohortDecorator cohortDecorator) {
484 this.cohortDecorator = cohortDecorator;
487 static class CohortEntry {
488 private final String transactionID;
489 private ShardDataTreeCohort cohort;
490 private final ReadWriteShardDataTreeTransaction transaction;
491 private ActorRef replySender;
493 private boolean doImmediateCommit;
494 private final Stopwatch lastAccessTimer = Stopwatch.createStarted();
496 CohortEntry(String transactionID, ReadWriteShardDataTreeTransaction transaction) {
497 this.transaction = Preconditions.checkNotNull(transaction);
498 this.transactionID = transactionID;
501 CohortEntry(String transactionID, ShardDataTreeCohort cohort,
502 MutableCompositeModification compositeModification) {
503 this.transactionID = transactionID;
504 this.cohort = cohort;
505 this.transaction = null;
508 CohortEntry(String transactionID, ShardDataTreeCohort cohort) {
509 this.transactionID = transactionID;
510 this.cohort = cohort;
511 this.transaction = null;
514 void updateLastAccessTime() {
515 lastAccessTimer.reset();
516 lastAccessTimer.start();
519 String getTransactionID() {
520 return transactionID;
523 ShardDataTreeCohort getCohort() {
527 void applyModifications(Iterable<Modification> modifications) {
528 for (Modification modification : modifications) {
529 modification.apply(transaction.getSnapshot());
533 void ready(CohortDecorator cohortDecorator, boolean doImmediateCommit) {
534 Preconditions.checkState(cohort == null, "cohort was already set");
536 setDoImmediateCommit(doImmediateCommit);
538 cohort = transaction.ready();
540 if(cohortDecorator != null) {
541 // Call the hook for unit tests.
542 cohort = cohortDecorator.decorate(transactionID, cohort);
546 boolean isReadyToCommit() {
547 return replySender != null;
550 boolean isExpired(long expireTimeInMillis) {
551 return lastAccessTimer.elapsed(TimeUnit.MILLISECONDS) >= expireTimeInMillis;
554 boolean isDoImmediateCommit() {
555 return doImmediateCommit;
558 void setDoImmediateCommit(boolean doImmediateCommit) {
559 this.doImmediateCommit = doImmediateCommit;
562 ActorRef getReplySender() {
566 void setReplySender(ActorRef replySender) {
567 this.replySender = replySender;
574 void setShard(Shard shard) {
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();