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 message.getTransactionID());
221 final CohortEntry cohortEntry = new CohortEntry(message.getTransactionID(), cohort);
222 cohortCache.put(message.getTransactionID(), cohortEntry);
223 cohortEntry.setDoImmediateCommit(message.isDoCommitOnReady());
225 if(!queueCohortEntry(cohortEntry, sender, shard)) {
229 log.debug("{}: Applying local modifications for Tx {}", name, message.getTransactionID());
231 if (message.isDoCommitOnReady()) {
232 cohortEntry.setReplySender(sender);
233 cohortEntry.setShard(shard);
234 handleCanCommit(cohortEntry);
236 sender.tell(readyTransactionReply(shard), shard.self());
240 private void handleCanCommit(CohortEntry cohortEntry) {
241 String transactionID = cohortEntry.getTransactionID();
243 cohortEntry.updateLastAccessTime();
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.
249 if(log.isDebugEnabled()) {
250 log.debug("{}: Commit for Tx {} already in progress - skipping canCommit for {} for now",
251 name, currentCohortEntry.getTransactionID(), transactionID);
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);
264 if(log.isDebugEnabled()) {
265 log.debug("{}: Tx {} is the next pending canCommit - skipping {} for now",
266 name, queuedCohortEntries.peek().getTransactionID(), transactionID);
272 * This method handles the canCommit phase for a transaction.
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
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());
292 cohortEntry.setReplySender(sender);
293 cohortEntry.setShard(shard);
295 handleCanCommit(cohortEntry);
298 private void doCanCommit(final CohortEntry cohortEntry) {
299 boolean canCommit = false;
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();
306 log.debug("{}: canCommit for {}: {}", name, cohortEntry.getTransactionID(), canCommit);
308 if(cohortEntry.isDoImmediateCommit()) {
310 doCommit(cohortEntry);
312 cohortEntry.getReplySender().tell(new Status.Failure(new TransactionCommitFailedException(
313 "Can Commit failed, no detailed cause available.")), cohortEntry.getShard().self());
316 cohortEntry.getReplySender().tell(
317 canCommit ? CanCommitTransactionReply.YES.toSerializable() :
318 CanCommitTransactionReply.NO.toSerializable(), cohortEntry.getShard().self());
320 } catch (Exception e) {
321 log.debug("{}: An exception occurred during canCommit", name, e);
323 Throwable failure = e;
324 if(e instanceof ExecutionException) {
325 failure = e.getCause();
328 cohortEntry.getReplySender().tell(new Status.Failure(failure), cohortEntry.getShard().self());
331 // Remove the entry from the cache now.
332 currentTransactionComplete(cohortEntry.getTransactionID(), true);
337 private boolean doCommit(CohortEntry cohortEntry) {
338 log.debug("{}: Committing transaction {}", name, cohortEntry.getTransactionID());
340 boolean success = false;
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.
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();
353 cohortEntry.getShard().continueCommit(cohortEntry);
355 cohortEntry.updateLastAccessTime();
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());
363 currentTransactionComplete(cohortEntry.getTransactionID(), true);
370 * This method handles the preCommit and commit phases for a transaction.
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.
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
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());
392 cohortEntry.setReplySender(sender);
393 return doCommit(cohortEntry);
397 * Returns the cohort entry for the Tx commit currently in progress if the given transaction ID
398 * matches the current entry.
400 * @param transactionID the ID of the transaction
401 * @return the current CohortEntry or null if the given transaction ID does not match the
404 public CohortEntry getCohortEntryIfCurrent(String transactionID) {
405 if(isCurrentTransaction(transactionID)) {
406 return currentCohortEntry;
412 public CohortEntry getCurrentCohortEntry() {
413 return currentCohortEntry;
416 public CohortEntry getAndRemoveCohortEntry(String transactionID) {
417 return cohortCache.remove(transactionID);
420 public boolean isCurrentTransaction(String transactionID) {
421 return currentCohortEntry != null &&
422 currentCohortEntry.getTransactionID().equals(transactionID);
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.
430 * @param transactionID the ID of the completed transaction
431 * @param removeCohortEntry if true the CohortEntry for the transaction is also removed from
434 public void currentTransactionComplete(String transactionID, boolean removeCohortEntry) {
435 if(removeCohortEntry) {
436 cohortCache.remove(transactionID);
439 if(isCurrentTransaction(transactionID)) {
440 currentCohortEntry = null;
442 log.debug("{}: currentTransactionComplete: {}", name, transactionID);
444 maybeProcessNextCohortEntry();
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);
461 currentCohortEntry = next;
462 currentCohortEntry.updateLastAccessTime();
463 doCanCommit(currentCohortEntry);
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);
472 cohortCache.remove(next.getTransactionID());
479 void cleanupExpiredCohortEntries() {
480 maybeProcessNextCohortEntry();
484 void setCohortDecorator(CohortDecorator cohortDecorator) {
485 this.cohortDecorator = cohortDecorator;
488 static class CohortEntry {
489 private final String transactionID;
490 private ShardDataTreeCohort cohort;
491 private final ReadWriteShardDataTreeTransaction transaction;
492 private ActorRef replySender;
494 private boolean doImmediateCommit;
495 private final Stopwatch lastAccessTimer = Stopwatch.createStarted();
497 CohortEntry(String transactionID, ReadWriteShardDataTreeTransaction transaction) {
498 this.transaction = Preconditions.checkNotNull(transaction);
499 this.transactionID = transactionID;
502 CohortEntry(String transactionID, ShardDataTreeCohort cohort,
503 MutableCompositeModification compositeModification) {
504 this.transactionID = transactionID;
505 this.cohort = cohort;
506 this.transaction = null;
509 CohortEntry(String transactionID, ShardDataTreeCohort cohort) {
510 this.transactionID = transactionID;
511 this.cohort = cohort;
512 this.transaction = null;
515 void updateLastAccessTime() {
516 lastAccessTimer.reset();
517 lastAccessTimer.start();
520 String getTransactionID() {
521 return transactionID;
524 ShardDataTreeCohort getCohort() {
528 void applyModifications(Iterable<Modification> modifications) {
529 for (Modification modification : modifications) {
530 modification.apply(transaction.getSnapshot());
534 void ready(CohortDecorator cohortDecorator, boolean doImmediateCommit) {
535 Preconditions.checkState(cohort == null, "cohort was already set");
537 setDoImmediateCommit(doImmediateCommit);
539 cohort = transaction.ready();
541 if(cohortDecorator != null) {
542 // Call the hook for unit tests.
543 cohort = cohortDecorator.decorate(transactionID, cohort);
547 boolean isReadyToCommit() {
548 return replySender != null;
551 boolean isExpired(long expireTimeInMillis) {
552 return lastAccessTimer.elapsed(TimeUnit.MILLISECONDS) >= expireTimeInMillis;
555 boolean isDoImmediateCommit() {
556 return doImmediateCommit;
559 void setDoImmediateCommit(boolean doImmediateCommit) {
560 this.doImmediateCommit = doImmediateCommit;
563 ActorRef getReplySender() {
567 void setReplySender(ActorRef replySender) {
568 this.replySender = replySender;
575 void setShard(Shard shard) {
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();