import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
+import java.util.Collections;
+import java.util.Deque;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Queue;
+import java.util.SortedSet;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.function.Consumer;
this.cohort = Preconditions.checkNotNull(cohort);
lastAccess = now;
}
+
+ @Override
+ public String toString() {
+ return "CommitEntry [tx=" + cohort.getIdentifier() + ", state=" + cohort.getState() + "]";
+ }
}
private static final Timeout COMMIT_STEP_TIMEOUT = new Timeout(Duration.create(5, TimeUnit.SECONDS));
private final Map<LocalHistoryIdentifier, ShardDataTreeTransactionChain> transactionChains = new HashMap<>();
private final DataTreeCohortActorRegistry cohortRegistry = new DataTreeCohortActorRegistry();
- private final Queue<CommitEntry> pendingTransactions = new ArrayDeque<>();
+ private final Deque<CommitEntry> pendingTransactions = new ArrayDeque<>();
private final Queue<CommitEntry> pendingCommits = new ArrayDeque<>();
private final Queue<CommitEntry> pendingFinishCommits = new ArrayDeque<>();
}
@Override
- ShardDataTreeCohort finishTransaction(final ReadWriteShardDataTreeTransaction transaction) {
+ ShardDataTreeCohort finishTransaction(final ReadWriteShardDataTreeTransaction transaction,
+ final java.util.Optional<SortedSet<String>> participatingShardNames) {
final DataTreeModification snapshot = transaction.getSnapshot();
snapshot.ready();
- return createReadyCohort(transaction.getIdentifier(), snapshot);
+ return createReadyCohort(transaction.getIdentifier(), snapshot, participatingShardNames);
}
void purgeTransaction(final TransactionIdentifier id, final Runnable callback) {
return;
}
if (!cohort.equals(head.cohort)) {
- LOG.debug("{}: Transaction {} scheduled for canCommit step", logContext, cohort.getIdentifier());
- return;
+ // The tx isn't at the head of the queue so we can't start canCommit at this point. Here we check if this
+ // tx should be moved ahead of other tx's in the READY state in the pendingTransactions queue. If this tx
+ // has other participating shards, it could deadlock with other tx's accessing the same shards
+ // depending on the order the tx's are readied on each shard
+ // (see https://jira.opendaylight.org/browse/CONTROLLER-1836). Therefore, if the preceding participating
+ // shard names for a preceding pending tx, call it A, in the queue matches that of this tx, then this tx
+ // is allowed to be moved ahead of tx A in the queue so it is processed first to avoid potential deadlock
+ // if tx A is behind this tx in the pendingTransactions queue for a preceding shard. In other words, since
+ // canCommmit for this tx was requested before tx A, honor that request. If this tx is moved to the head of
+ // the queue as a result, then proceed with canCommit.
+
+ Collection<String> precedingShardNames = extractPrecedingShardNames(cohort.getParticipatingShardNames());
+ if (precedingShardNames.isEmpty()) {
+ LOG.debug("{}: Tx {} is scheduled for canCommit step", logContext, cohort.getIdentifier());
+ return;
+ }
+
+ LOG.debug("{}: Evaluating tx {} for canCommit - preceding participating shard names {}",
+ logContext, cohort.getIdentifier(), precedingShardNames);
+ final Iterator<CommitEntry> iter = pendingTransactions.iterator();
+ int index = -1;
+ int moveToIndex = -1;
+ while (iter.hasNext()) {
+ final CommitEntry entry = iter.next();
+ ++index;
+
+ if (cohort.equals(entry.cohort)) {
+ if (moveToIndex < 0) {
+ LOG.debug("{}: Not moving tx {} - cannot proceed with canCommit",
+ logContext, cohort.getIdentifier());
+ return;
+ }
+
+ LOG.debug("{}: Moving {} to index {} in the pendingTransactions queue",
+ logContext, cohort.getIdentifier(), moveToIndex);
+ iter.remove();
+ insertEntry(pendingTransactions, entry, moveToIndex);
+
+ if (!cohort.equals(pendingTransactions.peek().cohort)) {
+ LOG.debug("{}: Tx {} is not at the head of the queue - cannot proceed with canCommit",
+ logContext, cohort.getIdentifier());
+ return;
+ }
+
+ LOG.debug("{}: Tx {} is now at the head of the queue - proceeding with canCommit",
+ logContext, cohort.getIdentifier());
+ break;
+ }
+
+ if (entry.cohort.getState() != State.READY) {
+ LOG.debug("{}: Skipping pending transaction {} in state {}",
+ logContext, entry.cohort.getIdentifier(), entry.cohort.getState());
+ continue;
+ }
+
+ final Collection<String> pendingPrecedingShardNames = extractPrecedingShardNames(
+ entry.cohort.getParticipatingShardNames());
+
+ if (precedingShardNames.equals(pendingPrecedingShardNames)) {
+ if (moveToIndex < 0) {
+ LOG.debug("{}: Preceding shard names {} for pending tx {} match - saving moveToIndex {}",
+ logContext, pendingPrecedingShardNames, entry.cohort.getIdentifier(), index);
+ moveToIndex = index;
+ } else {
+ LOG.debug(
+ "{}: Preceding shard names {} for pending tx {} match but moveToIndex already set to {}",
+ logContext, pendingPrecedingShardNames, entry.cohort.getIdentifier(), moveToIndex);
+ }
+ } else {
+ LOG.debug("{}: Preceding shard names {} for pending tx {} differ - skipping",
+ logContext, pendingPrecedingShardNames, entry.cohort.getIdentifier());
+ }
+ }
}
processNextPendingTransaction();
}
+ private void insertEntry(Deque<CommitEntry> queue, CommitEntry entry, int atIndex) {
+ if (atIndex == 0) {
+ queue.addFirst(entry);
+ return;
+ }
+
+ LOG.trace("Inserting into Deque at index {}", atIndex);
+
+ Deque<CommitEntry> tempStack = new ArrayDeque<>(atIndex);
+ for (int i = 0; i < atIndex; i++) {
+ tempStack.push(queue.poll());
+ }
+
+ queue.addFirst(entry);
+
+ tempStack.forEach(queue::addFirst);
+ }
+
+ private Collection<String> extractPrecedingShardNames(
+ java.util.Optional<SortedSet<String>> participatingShardNames) {
+ return participatingShardNames.map((Function<SortedSet<String>, Collection<String>>)
+ set -> set.headSet(shard.getShardName())).orElse(Collections.<String>emptyList());
+ }
+
private void failPreCommit(final Throwable cause) {
shard.getShardMBean().incrementFailedTransactionsCount();
pendingTransactions.poll().cohort.failedPreCommit(cause);
}
@Override
- ShardDataTreeCohort createReadyCohort(final TransactionIdentifier txId, final DataTreeModification mod) {
+ ShardDataTreeCohort createReadyCohort(final TransactionIdentifier txId, final DataTreeModification mod,
+ final java.util.Optional<SortedSet<String>> participatingShardNames) {
SimpleShardDataTreeCohort cohort = new SimpleShardDataTreeCohort(this, mod, txId,
cohortRegistry.createCohort(schemaContext, txId, runnable -> shard.executeInSelf(runnable),
- COMMIT_STEP_TIMEOUT));
+ COMMIT_STEP_TIMEOUT), participatingShardNames);
pendingTransactions.add(new CommitEntry(cohort, readTime()));
return cohort;
}
// Exposed for ShardCommitCoordinator so it does not have deal with local histories (it does not care), this mimics
// the newReadWriteTransaction()
- ShardDataTreeCohort newReadyCohort(final TransactionIdentifier txId, final DataTreeModification mod) {
+ ShardDataTreeCohort newReadyCohort(final TransactionIdentifier txId, final DataTreeModification mod,
+ final java.util.Optional<SortedSet<String>> participatingShardNames) {
if (txId.getHistoryId().getHistoryId() == 0) {
- return createReadyCohort(txId, mod);
+ return createReadyCohort(txId, mod, participatingShardNames);
}
- return ensureTransactionChain(txId.getHistoryId(), null).createReadyCohort(txId, mod);
+ return ensureTransactionChain(txId.getHistoryId(), null).createReadyCohort(txId, mod, participatingShardNames);
}
@SuppressFBWarnings(value = "DB_DUPLICATE_SWITCH_CLAUSES", justification = "See inline comments below.")
Code Review / controller.git / blobdiff