d43602aceafa8eb1d98e3fc54a19483089b4e0ce
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / ShardDataTree.java
1 /*
2  * Copyright (c) 2015 Cisco 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.util.Timeout;
12 import com.google.common.annotations.VisibleForTesting;
13 import com.google.common.base.Optional;
14 import com.google.common.base.Preconditions;
15 import com.google.common.base.Stopwatch;
16 import com.google.common.base.Verify;
17 import com.google.common.collect.ImmutableList;
18 import com.google.common.collect.ImmutableMap;
19 import com.google.common.collect.ImmutableMap.Builder;
20 import com.google.common.primitives.UnsignedLong;
21 import java.io.IOException;
22 import java.util.AbstractMap.SimpleEntry;
23 import java.util.ArrayDeque;
24 import java.util.ArrayList;
25 import java.util.Collection;
26 import java.util.HashMap;
27 import java.util.Iterator;
28 import java.util.Map;
29 import java.util.Map.Entry;
30 import java.util.Queue;
31 import java.util.concurrent.ExecutionException;
32 import java.util.concurrent.TimeUnit;
33 import java.util.concurrent.TimeoutException;
34 import java.util.function.UnaryOperator;
35 import javax.annotation.Nonnull;
36 import javax.annotation.concurrent.NotThreadSafe;
37 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
38 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
39 import org.opendaylight.controller.cluster.datastore.DataTreeCohortActorRegistry.CohortRegistryCommand;
40 import org.opendaylight.controller.cluster.datastore.ShardDataTreeCohort.State;
41 import org.opendaylight.controller.cluster.datastore.persisted.CommitTransactionPayload;
42 import org.opendaylight.controller.cluster.datastore.persisted.MetadataShardDataTreeSnapshot;
43 import org.opendaylight.controller.cluster.datastore.persisted.ShardDataTreeSnapshot;
44 import org.opendaylight.controller.cluster.datastore.persisted.ShardDataTreeSnapshotMetadata;
45 import org.opendaylight.controller.cluster.datastore.utils.PruningDataTreeModification;
46 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
47 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataBroker.DataChangeScope;
48 import org.opendaylight.controller.md.sal.common.api.data.AsyncDataChangeListener;
49 import org.opendaylight.controller.md.sal.common.api.data.OptimisticLockFailedException;
50 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
51 import org.opendaylight.controller.md.sal.dom.api.DOMDataTreeChangeListener;
52 import org.opendaylight.controller.md.sal.dom.store.impl.DataChangeListenerRegistration;
53 import org.opendaylight.yangtools.concepts.Identifier;
54 import org.opendaylight.yangtools.concepts.ListenerRegistration;
55 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
56 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
57 import org.opendaylight.yangtools.yang.data.api.schema.tree.ConflictingModificationAppliedException;
58 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidate;
59 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidateTip;
60 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeCandidates;
61 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification;
62 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeSnapshot;
63 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
64 import org.opendaylight.yangtools.yang.data.api.schema.tree.ModificationType;
65 import org.opendaylight.yangtools.yang.data.api.schema.tree.TipProducingDataTree;
66 import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
67 import org.opendaylight.yangtools.yang.data.impl.schema.tree.InMemoryDataTreeFactory;
68 import org.opendaylight.yangtools.yang.model.api.SchemaContext;
69 import org.slf4j.Logger;
70 import org.slf4j.LoggerFactory;
71 import scala.concurrent.duration.Duration;
72
73 /**
74  * Internal shard state, similar to a DOMStore, but optimized for use in the actor system,
75  * e.g. it does not expose public interfaces and assumes it is only ever called from a
76  * single thread.
77  *
78  * This class is not part of the API contract and is subject to change at any time.
79  */
80 @NotThreadSafe
81 public class ShardDataTree extends ShardDataTreeTransactionParent {
82     private static final class CommitEntry {
83         final SimpleShardDataTreeCohort cohort;
84         long lastAccess;
85
86         CommitEntry(final SimpleShardDataTreeCohort cohort, final long now) {
87             this.cohort = Preconditions.checkNotNull(cohort);
88             lastAccess = now;
89         }
90     }
91
92     private static final Timeout COMMIT_STEP_TIMEOUT = new Timeout(Duration.create(5, TimeUnit.SECONDS));
93     private static final Logger LOG = LoggerFactory.getLogger(ShardDataTree.class);
94
95     private final Map<LocalHistoryIdentifier, ShardDataTreeTransactionChain> transactionChains = new HashMap<>();
96     private final DataTreeCohortActorRegistry cohortRegistry = new DataTreeCohortActorRegistry();
97     private final Queue<CommitEntry> pendingTransactions = new ArrayDeque<>();
98     private final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher;
99     private final ShardDataChangeListenerPublisher dataChangeListenerPublisher;
100     private final Collection<ShardDataTreeMetadata<?>> metadata;
101     private final TipProducingDataTree dataTree;
102     private final String logContext;
103     private final Shard shard;
104     private Runnable runOnPendingTransactionsComplete;
105
106     private SchemaContext schemaContext;
107
108     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TipProducingDataTree dataTree,
109             final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher,
110             final ShardDataChangeListenerPublisher dataChangeListenerPublisher, final String logContext,
111             final ShardDataTreeMetadata<?>... metadata) {
112         this.dataTree = Preconditions.checkNotNull(dataTree);
113         updateSchemaContext(schemaContext);
114
115         this.shard = Preconditions.checkNotNull(shard);
116         this.treeChangeListenerPublisher = Preconditions.checkNotNull(treeChangeListenerPublisher);
117         this.dataChangeListenerPublisher = Preconditions.checkNotNull(dataChangeListenerPublisher);
118         this.logContext = Preconditions.checkNotNull(logContext);
119         this.metadata = ImmutableList.copyOf(metadata);
120     }
121
122     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TreeType treeType,
123             final ShardDataTreeChangeListenerPublisher treeChangeListenerPublisher,
124             final ShardDataChangeListenerPublisher dataChangeListenerPublisher, final String logContext) {
125         this(shard, schemaContext, InMemoryDataTreeFactory.getInstance().create(treeType),
126                 treeChangeListenerPublisher, dataChangeListenerPublisher, logContext);
127     }
128
129     @VisibleForTesting
130     public ShardDataTree(final Shard shard, final SchemaContext schemaContext, final TreeType treeType) {
131         this(shard, schemaContext, treeType, new DefaultShardDataTreeChangeListenerPublisher(),
132                 new DefaultShardDataChangeListenerPublisher(), "");
133     }
134
135     String logContext() {
136         return logContext;
137     }
138
139     public TipProducingDataTree getDataTree() {
140         return dataTree;
141     }
142
143     SchemaContext getSchemaContext() {
144         return schemaContext;
145     }
146
147     void updateSchemaContext(final SchemaContext schemaContext) {
148         dataTree.setSchemaContext(schemaContext);
149         this.schemaContext = Preconditions.checkNotNull(schemaContext);
150     }
151
152     /**
153      * Take a snapshot of current state for later recovery.
154      *
155      * @return A state snapshot
156      */
157     @Nonnull ShardDataTreeSnapshot takeStateSnapshot() {
158         final NormalizedNode<?, ?> rootNode = dataTree.takeSnapshot().readNode(YangInstanceIdentifier.EMPTY).get();
159         final Builder<Class<? extends ShardDataTreeSnapshotMetadata<?>>, ShardDataTreeSnapshotMetadata<?>> metaBuilder =
160                 ImmutableMap.builder();
161
162         for (ShardDataTreeMetadata<?> m : metadata) {
163             final ShardDataTreeSnapshotMetadata<?> meta = m.toStapshot();
164             if (meta != null) {
165                 metaBuilder.put(meta.getType(), meta);
166             }
167         }
168
169         return new MetadataShardDataTreeSnapshot(rootNode, metaBuilder.build());
170     }
171
172     private void applySnapshot(final @Nonnull ShardDataTreeSnapshot snapshot,
173             final UnaryOperator<DataTreeModification> wrapper) throws DataValidationFailedException {
174         final Stopwatch elapsed = Stopwatch.createStarted();
175
176         if (!pendingTransactions.isEmpty()) {
177             LOG.warn("{}: applying state snapshot with pending transactions", logContext);
178         }
179
180         final Map<Class<? extends ShardDataTreeSnapshotMetadata<?>>, ShardDataTreeSnapshotMetadata<?>> snapshotMeta;
181         if (snapshot instanceof MetadataShardDataTreeSnapshot) {
182             snapshotMeta = ((MetadataShardDataTreeSnapshot) snapshot).getMetadata();
183         } else {
184             snapshotMeta = ImmutableMap.of();
185         }
186
187         for (ShardDataTreeMetadata<?> m : metadata) {
188             final ShardDataTreeSnapshotMetadata<?> s = snapshotMeta.get(m.getSupportedType());
189             if (s != null) {
190                 m.applySnapshot(s);
191             } else {
192                 m.reset();
193             }
194         }
195
196         final DataTreeModification mod = wrapper.apply(dataTree.takeSnapshot().newModification());
197         // delete everything first
198         mod.delete(YangInstanceIdentifier.EMPTY);
199
200         final java.util.Optional<NormalizedNode<?, ?>> maybeNode = snapshot.getRootNode();
201         if (maybeNode.isPresent()) {
202             // Add everything from the remote node back
203             mod.write(YangInstanceIdentifier.EMPTY, maybeNode.get());
204         }
205         mod.ready();
206
207         final DataTreeModification unwrapped = unwrap(mod);
208         dataTree.validate(unwrapped);
209         dataTree.commit(dataTree.prepare(unwrapped));
210         LOG.debug("{}: state snapshot applied in %s", logContext, elapsed);
211     }
212
213     private PruningDataTreeModification wrapWithPruning(final DataTreeModification delegate) {
214         return new PruningDataTreeModification(delegate, dataTree, schemaContext);
215     }
216
217     private static DataTreeModification unwrap(final DataTreeModification modification) {
218         if (modification instanceof PruningDataTreeModification) {
219             return ((PruningDataTreeModification)modification).delegate();
220         }
221         return modification;
222     }
223
224     /**
225      * Apply a snapshot coming from recovery. This method does not assume the SchemaContexts match and performs data
226      * pruning in an attempt to adjust the state to our current SchemaContext.
227      *
228      * @param snapshot Snapshot that needs to be applied
229      * @throws DataValidationFailedException when the snapshot fails to apply
230      */
231     void applyRecoverySnapshot(final @Nonnull ShardDataTreeSnapshot snapshot) throws DataValidationFailedException {
232         applySnapshot(snapshot, this::wrapWithPruning);
233     }
234
235
236     /**
237      * Apply a snapshot coming from the leader. This method assumes the leader and follower SchemaContexts match and
238      * does not perform any pruning.
239      *
240      * @param snapshot Snapshot that needs to be applied
241      * @throws DataValidationFailedException when the snapshot fails to apply
242      */
243     void applySnapshot(final @Nonnull ShardDataTreeSnapshot snapshot) throws DataValidationFailedException {
244         applySnapshot(snapshot, UnaryOperator.identity());
245     }
246
247     private void applyRecoveryCandidate(final DataTreeCandidate candidate) throws DataValidationFailedException {
248         final PruningDataTreeModification mod = wrapWithPruning(dataTree.takeSnapshot().newModification());
249         DataTreeCandidates.applyToModification(mod, candidate);
250         mod.ready();
251
252         final DataTreeModification unwrapped = mod.delegate();
253         LOG.trace("{}: Applying recovery modification {}", logContext, unwrapped);
254
255         dataTree.validate(unwrapped);
256         dataTree.commit(dataTree.prepare(unwrapped));
257     }
258
259     /**
260      * Apply a payload coming from recovery. This method does not assume the SchemaContexts match and performs data
261      * pruning in an attempt to adjust the state to our current SchemaContext.
262      *
263      * @param payload Payload
264      * @throws IOException when the snapshot fails to deserialize
265      * @throws DataValidationFailedException when the snapshot fails to apply
266      */
267     void applyRecoveryPayload(final @Nonnull Payload payload) throws IOException, DataValidationFailedException {
268         if (payload instanceof CommitTransactionPayload) {
269             final Entry<TransactionIdentifier, DataTreeCandidate> e = ((CommitTransactionPayload) payload).getCandidate();
270             applyRecoveryCandidate(e.getValue());
271             allMetadataCommittedTransaction(e.getKey());
272         } else if (payload instanceof DataTreeCandidatePayload) {
273             applyRecoveryCandidate(((DataTreeCandidatePayload) payload).getCandidate());
274         } else {
275             LOG.warn("{}: ignoring unhandled payload {}", logContext, payload);
276         }
277     }
278
279     private void applyReplicatedCandidate(final Identifier identifier, final DataTreeCandidate foreign)
280             throws DataValidationFailedException {
281         LOG.debug("{}: Applying foreign transaction {}", logContext, identifier);
282
283         final DataTreeModification mod = dataTree.takeSnapshot().newModification();
284         DataTreeCandidates.applyToModification(mod, foreign);
285         mod.ready();
286
287         LOG.trace("{}: Applying foreign modification {}", logContext, mod);
288         dataTree.validate(mod);
289         final DataTreeCandidate candidate = dataTree.prepare(mod);
290         dataTree.commit(candidate);
291
292         notifyListeners(candidate);
293     }
294
295     /**
296      * Apply a payload coming from the leader, which could actually be us. This method assumes the leader and follower
297      * SchemaContexts match and does not perform any pruning.
298      *
299      * @param identifier Payload identifier as returned from RaftActor
300      * @param payload Payload
301      * @throws IOException when the snapshot fails to deserialize
302      * @throws DataValidationFailedException when the snapshot fails to apply
303      */
304     void applyReplicatedPayload(final Identifier identifier, final Payload payload) throws IOException,
305             DataValidationFailedException {
306         /*
307          * This is a bit more involved than it needs to be due to to the fact we do not want to be touching the payload
308          * if we are the leader and it has originated with us.
309          *
310          * The identifier will only ever be non-null when we were the leader which achieved consensus. Unfortunately,
311          * though, this may not be the case anymore, as we are being called some time afterwards and we may not be
312          * acting in that capacity anymore.
313          *
314          * In any case, we know that this is an entry coming from replication, hence we can be sure we will not observe
315          * pre-Boron state -- which limits the number of options here.
316          */
317         if (payload instanceof CommitTransactionPayload) {
318             if (identifier == null) {
319                 final Entry<TransactionIdentifier, DataTreeCandidate> e = ((CommitTransactionPayload) payload).getCandidate();
320                 applyReplicatedCandidate(e.getKey(), e.getValue());
321                 allMetadataCommittedTransaction(e.getKey());
322             } else {
323                 Verify.verify(identifier instanceof TransactionIdentifier);
324                 payloadReplicationComplete((TransactionIdentifier) identifier);
325             }
326         } else {
327             LOG.warn("{}: ignoring unhandled identifier {} payload {}", logContext, identifier, payload);
328         }
329     }
330
331     private void payloadReplicationComplete(final TransactionIdentifier txId) {
332         final CommitEntry current = pendingTransactions.peek();
333         if (current == null) {
334             LOG.warn("{}: No outstanding transactions, ignoring consensus on transaction {}", logContext, txId);
335             return;
336         }
337
338         if (!current.cohort.getIdentifier().equals(txId)) {
339             LOG.warn("{}: Head of queue is {}, ignoring consensus on transaction {}", logContext,
340                 current.cohort.getIdentifier(), txId);
341             return;
342         }
343
344         finishCommit(current.cohort);
345     }
346
347     private void allMetadataCommittedTransaction(final TransactionIdentifier txId) {
348         for (ShardDataTreeMetadata<?> m : metadata) {
349             m.onTransactionCommitted(txId);
350         }
351     }
352
353     private ShardDataTreeTransactionChain ensureTransactionChain(final LocalHistoryIdentifier localHistoryIdentifier) {
354         ShardDataTreeTransactionChain chain = transactionChains.get(localHistoryIdentifier);
355         if (chain == null) {
356             chain = new ShardDataTreeTransactionChain(localHistoryIdentifier, this);
357             transactionChains.put(localHistoryIdentifier, chain);
358         }
359
360         return chain;
361     }
362
363     ReadOnlyShardDataTreeTransaction newReadOnlyTransaction(final TransactionIdentifier txId) {
364         if (txId.getHistoryId().getHistoryId() == 0) {
365             return new ReadOnlyShardDataTreeTransaction(txId, dataTree.takeSnapshot());
366         }
367
368         return ensureTransactionChain(txId.getHistoryId()).newReadOnlyTransaction(txId);
369     }
370
371     ReadWriteShardDataTreeTransaction newReadWriteTransaction(final TransactionIdentifier txId) {
372         if (txId.getHistoryId().getHistoryId() == 0) {
373             return new ReadWriteShardDataTreeTransaction(ShardDataTree.this, txId, dataTree.takeSnapshot()
374                     .newModification());
375         }
376
377         return ensureTransactionChain(txId.getHistoryId()).newReadWriteTransaction(txId);
378     }
379
380     public void notifyListeners(final DataTreeCandidate candidate) {
381         treeChangeListenerPublisher.publishChanges(candidate, logContext);
382         dataChangeListenerPublisher.publishChanges(candidate, logContext);
383     }
384
385     void notifyOfInitialData(final DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier,
386             NormalizedNode<?, ?>>> listenerReg, final Optional<DataTreeCandidate> currentState) {
387         if (currentState.isPresent()) {
388             ShardDataChangeListenerPublisher localPublisher = dataChangeListenerPublisher.newInstance();
389             localPublisher.registerDataChangeListener(listenerReg.getPath(), listenerReg.getInstance(),
390                     listenerReg.getScope());
391             localPublisher.publishChanges(currentState.get(), logContext);
392         }
393     }
394
395     void notifyOfInitialData(final YangInstanceIdentifier path, final DOMDataTreeChangeListener listener,
396             final Optional<DataTreeCandidate> currentState) {
397         if (currentState.isPresent()) {
398             ShardDataTreeChangeListenerPublisher localPublisher = treeChangeListenerPublisher.newInstance();
399             localPublisher.registerTreeChangeListener(path, listener);
400             localPublisher.publishChanges(currentState.get(), logContext);
401         }
402     }
403
404     void closeAllTransactionChains() {
405         for (ShardDataTreeTransactionChain chain : transactionChains.values()) {
406             chain.close();
407         }
408
409         transactionChains.clear();
410     }
411
412     void closeTransactionChain(final LocalHistoryIdentifier transactionChainId) {
413         final ShardDataTreeTransactionChain chain = transactionChains.remove(transactionChainId);
414         if (chain != null) {
415             chain.close();
416         } else {
417             LOG.debug("{}: Closing non-existent transaction chain {}", logContext, transactionChainId);
418         }
419     }
420
421     Entry<DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>>,
422             Optional<DataTreeCandidate>> registerChangeListener(final YangInstanceIdentifier path,
423                     final AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>> listener,
424                     final DataChangeScope scope) {
425         final DataChangeListenerRegistration<AsyncDataChangeListener<YangInstanceIdentifier, NormalizedNode<?, ?>>> reg =
426                 dataChangeListenerPublisher.registerDataChangeListener(path, listener, scope);
427
428         return new SimpleEntry<>(reg, readCurrentData());
429     }
430
431     private Optional<DataTreeCandidate> readCurrentData() {
432         final Optional<NormalizedNode<?, ?>> currentState = dataTree.takeSnapshot().readNode(YangInstanceIdentifier.EMPTY);
433         return currentState.isPresent() ? Optional.of(DataTreeCandidates.fromNormalizedNode(
434             YangInstanceIdentifier.EMPTY, currentState.get())) : Optional.<DataTreeCandidate>absent();
435     }
436
437     public Entry<ListenerRegistration<DOMDataTreeChangeListener>, Optional<DataTreeCandidate>> registerTreeChangeListener(
438             final YangInstanceIdentifier path, final DOMDataTreeChangeListener listener) {
439         final ListenerRegistration<DOMDataTreeChangeListener> reg = treeChangeListenerPublisher.registerTreeChangeListener(
440                 path, listener);
441
442         return new SimpleEntry<>(reg, readCurrentData());
443     }
444
445     int getQueueSize() {
446         return pendingTransactions.size();
447     }
448
449     @Override
450     void abortTransaction(final AbstractShardDataTreeTransaction<?> transaction) {
451         // Intentional no-op
452     }
453
454     @Override
455     ShardDataTreeCohort finishTransaction(final ReadWriteShardDataTreeTransaction transaction) {
456         final DataTreeModification snapshot = transaction.getSnapshot();
457         snapshot.ready();
458
459         return createReadyCohort(transaction.getId(), snapshot);
460     }
461
462     public Optional<NormalizedNode<?, ?>> readNode(final YangInstanceIdentifier path) {
463         return dataTree.takeSnapshot().readNode(path);
464     }
465
466     public DataTreeSnapshot takeSnapshot() {
467         return dataTree.takeSnapshot();
468     }
469
470     public DataTreeModification newModification() {
471         return dataTree.takeSnapshot().newModification();
472     }
473
474     /**
475      * @deprecated This method violates DataTree containment and will be removed.
476      */
477     @VisibleForTesting
478     @Deprecated
479     public DataTreeCandidate commit(final DataTreeModification modification) throws DataValidationFailedException {
480         modification.ready();
481         dataTree.validate(modification);
482         DataTreeCandidate candidate = dataTree.prepare(modification);
483         dataTree.commit(candidate);
484         return candidate;
485     }
486
487     public Collection<ShardDataTreeCohort> getAndClearPendingTransactions() {
488         Collection<ShardDataTreeCohort> ret = new ArrayList<>(pendingTransactions.size());
489         for(CommitEntry entry: pendingTransactions) {
490             ret.add(entry.cohort);
491         }
492
493         pendingTransactions.clear();
494         return ret;
495     }
496
497     private void processNextTransaction() {
498         while (!pendingTransactions.isEmpty()) {
499             final CommitEntry entry = pendingTransactions.peek();
500             final SimpleShardDataTreeCohort cohort = entry.cohort;
501             final DataTreeModification modification = cohort.getDataTreeModification();
502
503             if(cohort.getState() != State.CAN_COMMIT_PENDING) {
504                 break;
505             }
506
507             LOG.debug("{}: Validating transaction {}", logContext, cohort.getIdentifier());
508             Exception cause;
509             try {
510                 dataTree.validate(modification);
511                 LOG.debug("{}: Transaction {} validated", logContext, cohort.getIdentifier());
512                 cohort.successfulCanCommit();
513                 entry.lastAccess = shard.ticker().read();
514                 return;
515             } catch (ConflictingModificationAppliedException e) {
516                 LOG.warn("{}: Store Tx {}: Conflicting modification for path {}.", logContext, cohort.getIdentifier(),
517                     e.getPath());
518                 cause = new OptimisticLockFailedException("Optimistic lock failed.", e);
519             } catch (DataValidationFailedException e) {
520                 LOG.warn("{}: Store Tx {}: Data validation failed for path {}.", logContext, cohort.getIdentifier(),
521                     e.getPath(), e);
522
523                 // For debugging purposes, allow dumping of the modification. Coupled with the above
524                 // precondition log, it should allow us to understand what went on.
525                 LOG.debug("{}: Store Tx {}: modifications: {} tree: {}", cohort.getIdentifier(), modification, dataTree);
526                 cause = new TransactionCommitFailedException("Data did not pass validation.", e);
527             } catch (Exception e) {
528                 LOG.warn("{}: Unexpected failure in validation phase", logContext, e);
529                 cause = e;
530             }
531
532             // Failure path: propagate the failure, remove the transaction from the queue and loop to the next one
533             pendingTransactions.poll().cohort.failedCanCommit(cause);
534         }
535
536         maybeRunOperationOnPendingTransactionsComplete();
537     }
538
539     void startCanCommit(final SimpleShardDataTreeCohort cohort) {
540         final SimpleShardDataTreeCohort current = pendingTransactions.peek().cohort;
541         if (!cohort.equals(current)) {
542             LOG.debug("{}: Transaction {} scheduled for canCommit step", logContext, cohort.getIdentifier());
543             return;
544         }
545
546         processNextTransaction();
547     }
548
549     private void failPreCommit(final Exception cause) {
550         shard.getShardMBean().incrementFailedTransactionsCount();
551         pendingTransactions.poll().cohort.failedPreCommit(cause);
552         processNextTransaction();
553     }
554
555     void startPreCommit(final SimpleShardDataTreeCohort cohort) {
556         final CommitEntry entry = pendingTransactions.peek();
557         Preconditions.checkState(entry != null, "Attempted to pre-commit of %s when no transactions pending", cohort);
558
559         final SimpleShardDataTreeCohort current = entry.cohort;
560         Verify.verify(cohort.equals(current), "Attempted to pre-commit %s while %s is pending", cohort, current);
561         final DataTreeCandidateTip candidate;
562         try {
563             candidate = dataTree.prepare(cohort.getDataTreeModification());
564         } catch (Exception e) {
565             failPreCommit(e);
566             return;
567         }
568
569         try {
570             cohort.userPreCommit(candidate);
571         } catch (ExecutionException | TimeoutException e) {
572             failPreCommit(e);
573             return;
574         }
575
576         entry.lastAccess = shard.ticker().read();
577         cohort.successfulPreCommit(candidate);
578     }
579
580     private void failCommit(final Exception cause) {
581         shard.getShardMBean().incrementFailedTransactionsCount();
582         pendingTransactions.poll().cohort.failedCommit(cause);
583         processNextTransaction();
584     }
585
586     private void finishCommit(final SimpleShardDataTreeCohort cohort) {
587         final TransactionIdentifier txId = cohort.getIdentifier();
588         final DataTreeCandidate candidate = cohort.getCandidate();
589
590         LOG.debug("{}: Resuming commit of transaction {}", logContext, txId);
591
592         try {
593             dataTree.commit(candidate);
594         } catch (Exception e) {
595             LOG.error("{}: Failed to commit transaction {}", logContext, txId, e);
596             failCommit(e);
597             return;
598         }
599
600         shard.getShardMBean().incrementCommittedTransactionCount();
601         shard.getShardMBean().setLastCommittedTransactionTime(System.currentTimeMillis());
602
603         // FIXME: propagate journal index
604         pendingTransactions.poll().cohort.successfulCommit(UnsignedLong.ZERO);
605
606         LOG.trace("{}: Transaction {} committed, proceeding to notify", logContext, txId);
607         notifyListeners(candidate);
608
609         processNextTransaction();
610     }
611
612     void startCommit(final SimpleShardDataTreeCohort cohort, final DataTreeCandidate candidate) {
613         final CommitEntry entry = pendingTransactions.peek();
614         Preconditions.checkState(entry != null, "Attempted to start commit of %s when no transactions pending", cohort);
615
616         final SimpleShardDataTreeCohort current = entry.cohort;
617         Verify.verify(cohort.equals(current), "Attempted to commit %s while %s is pending", cohort, current);
618
619         if (shard.canSkipPayload() || candidate.getRootNode().getModificationType() == ModificationType.UNMODIFIED) {
620             LOG.debug("{}: No replication required, proceeding to finish commit", logContext);
621             finishCommit(cohort);
622             return;
623         }
624
625         final TransactionIdentifier txId = cohort.getIdentifier();
626         final Payload payload;
627         try {
628             payload = CommitTransactionPayload.create(txId, candidate);
629         } catch (IOException e) {
630             LOG.error("{}: Failed to encode transaction {} candidate {}", logContext, txId, candidate, e);
631             pendingTransactions.poll().cohort.failedCommit(e);
632             return;
633         }
634
635         // Once completed, we will continue via payloadReplicationComplete
636         entry.lastAccess = shard.ticker().read();
637         shard.persistPayload(txId, payload);
638         LOG.debug("{}: Transaction {} submitted to persistence", logContext, txId);
639     }
640
641     void processCohortRegistryCommand(final ActorRef sender, final CohortRegistryCommand message) {
642         cohortRegistry.process(sender, message);
643     }
644
645     ShardDataTreeCohort createReadyCohort(final TransactionIdentifier txId,
646             final DataTreeModification modification) {
647         SimpleShardDataTreeCohort cohort = new SimpleShardDataTreeCohort(this, modification, txId,
648                 cohortRegistry.createCohort(schemaContext, txId, COMMIT_STEP_TIMEOUT));
649         pendingTransactions.add(new CommitEntry(cohort, shard.ticker().read()));
650         return cohort;
651     }
652
653     void checkForExpiredTransactions(final long transactionCommitTimeoutMillis) {
654         final long timeout = TimeUnit.MILLISECONDS.toNanos(transactionCommitTimeoutMillis);
655         final long now = shard.ticker().read();
656         final CommitEntry currentTx = pendingTransactions.peek();
657         if (currentTx != null && currentTx.lastAccess + timeout < now) {
658             LOG.warn("{}: Current transaction {} has timed out after {} ms in state {}", logContext,
659                     currentTx.cohort.getIdentifier(), transactionCommitTimeoutMillis, currentTx.cohort.getState());
660             boolean processNext = true;
661             switch (currentTx.cohort.getState()) {
662                 case CAN_COMMIT_PENDING:
663                     pendingTransactions.poll().cohort.failedCanCommit(new TimeoutException());
664                     break;
665                 case CAN_COMMIT_COMPLETE:
666                     pendingTransactions.poll().cohort.reportFailure(new TimeoutException());
667                     break;
668                 case PRE_COMMIT_PENDING:
669                     pendingTransactions.poll().cohort.failedPreCommit(new TimeoutException());
670                     break;
671                 case PRE_COMMIT_COMPLETE:
672                     // FIXME: this is a legacy behavior problem. Three-phase commit protocol specifies that after we
673                     //        are ready we should commit the transaction, not abort it. Our current software stack does
674                     //        not allow us to do that consistently, because we persist at the time of commit, hence
675                     //        we can end up in a state where we have pre-committed a transaction, then a leader failover
676                     //        occurred ... the new leader does not see the pre-committed transaction and does not have
677                     //        a running timer. To fix this we really need two persistence events.
678                     //
679                     //        The first one, done at pre-commit time will hold the transaction payload. When consensus
680                     //        is reached, we exit the pre-commit phase and start the pre-commit timer. Followers do not
681                     //        apply the state in this event.
682                     //
683                     //        The second one, done at commit (or abort) time holds only the transaction identifier and
684                     //        signals to followers that the state should (or should not) be applied.
685                     //
686                     //        In order to make the pre-commit timer working across failovers, though, we need
687                     //        a per-shard cluster-wide monotonic time, so a follower becoming the leader can accurately
688                     //        restart the timer.
689                     pendingTransactions.poll().cohort.reportFailure(new TimeoutException());
690                     break;
691                 case COMMIT_PENDING:
692                     LOG.warn("{}: Transaction {} is still committing, cannot abort", logContext,
693                         currentTx.cohort.getIdentifier());
694                     currentTx.lastAccess = now;
695                     processNext = false;
696                     return;
697                 case ABORTED:
698                 case COMMITTED:
699                 case FAILED:
700                 case READY:
701                 default:
702                     pendingTransactions.poll();
703             }
704
705             if (processNext) {
706                 processNextTransaction();
707             }
708         }
709     }
710
711     void startAbort(final SimpleShardDataTreeCohort cohort) {
712         final Iterator<CommitEntry> it = pendingTransactions.iterator();
713         if (!it.hasNext()) {
714             LOG.debug("{}: no open transaction while attempting to abort {}", logContext, cohort.getIdentifier());
715             return;
716         }
717
718         // First entry is special, as it may already be committing
719         final CommitEntry first = it.next();
720         if (cohort.equals(first.cohort)) {
721             if (cohort.getState() != State.COMMIT_PENDING) {
722                 LOG.debug("{}: aborted head of queue {} in state {}", logContext, cohort.getIdentifier(),
723                     cohort.getIdentifier());
724                 pendingTransactions.poll();
725                 processNextTransaction();
726             } else {
727                 LOG.warn("{}: transaction {} is committing, skipping abort", logContext, cohort.getIdentifier());
728             }
729
730             return;
731         }
732
733         while (it.hasNext()) {
734             final CommitEntry e = it.next();
735             if (cohort.equals(e.cohort)) {
736                 LOG.debug("{}: aborting queued transaction {}", logContext, cohort.getIdentifier());
737                 it.remove();
738                 return;
739             }
740         }
741
742         LOG.debug("{}: aborted transaction {} not found in the queue", logContext, cohort.getIdentifier());
743     }
744
745     void setRunOnPendingTransactionsComplete(final Runnable operation) {
746         runOnPendingTransactionsComplete = operation;
747         maybeRunOperationOnPendingTransactionsComplete();
748     }
749
750     private void maybeRunOperationOnPendingTransactionsComplete() {
751       if (runOnPendingTransactionsComplete != null && pendingTransactions.isEmpty()) {
752           LOG.debug("{}: Pending transactions complete - running operation {}", logContext,
753                   runOnPendingTransactionsComplete);
754
755           runOnPendingTransactionsComplete.run();
756           runOnPendingTransactionsComplete = null;
757       }
758   }
759 }

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