/*
* Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.controller.cluster.datastore;
import akka.actor.ActorSelection;
import akka.dispatch.Futures;
import akka.dispatch.OnComplete;
import com.google.common.base.Preconditions;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import javax.annotation.Nonnull;
import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
import org.opendaylight.controller.cluster.datastore.messages.PrimaryShardInfo;
import org.opendaylight.controller.md.sal.common.api.data.TransactionChainClosedException;
import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionChain;
import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import scala.concurrent.Future;
import scala.concurrent.Promise;
/**
* A chain of {@link TransactionProxy}s. It allows a single open transaction to be open
* at a time. For remote transactions, it also tracks the outstanding readiness requests
* towards the shard and unblocks operations only after all have completed.
*/
final class TransactionChainProxy extends AbstractTransactionContextFactory<LocalTransactionChain>
implements DOMStoreTransactionChain {
private abstract static class State {
/**
* Check if it is okay to allocate a new transaction.
* @throws IllegalStateException if a transaction may not be allocated.
*/
abstract void checkReady();
/**
* Return the future which needs to be waited for before shard information
* is returned (which unblocks remote transactions).
* @return Future to wait for, or null of no wait is necessary
*/
abstract Future<?> previousFuture();
}
private abstract static class Pending extends State {
private final TransactionIdentifier transaction;
private final Future<?> previousFuture;
Pending(final TransactionIdentifier transaction, final Future<?> previousFuture) {
this.previousFuture = previousFuture;
this.transaction = Preconditions.checkNotNull(transaction);
}
@Override
final Future<?> previousFuture() {
return previousFuture;
}
final TransactionIdentifier getIdentifier() {
return transaction;
}
}
private static final class Allocated extends Pending {
Allocated(final TransactionIdentifier transaction, final Future<?> previousFuture) {
super(transaction, previousFuture);
}
@Override
void checkReady() {
throw new IllegalStateException(String.format("Previous transaction %s is not ready yet", getIdentifier()));
}
}
private static final class Submitted extends Pending {
Submitted(final TransactionIdentifier transaction, final Future<?> previousFuture) {
super(transaction, previousFuture);
}
@Override
void checkReady() {
// Okay to allocate
}
}
private abstract static class DefaultState extends State {
@Override
final Future<?> previousFuture() {
return null;
}
}
private static final State IDLE_STATE = new DefaultState() {
@Override
void checkReady() {
// Okay to allocate
}
};
private static final State CLOSED_STATE = new DefaultState() {
@Override
void checkReady() {
throw new TransactionChainClosedException("Transaction chain has been closed");
}
};
private static final Logger LOG = LoggerFactory.getLogger(TransactionChainProxy.class);
private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "currentState");
private final TransactionContextFactory parent;
private volatile State currentState = IDLE_STATE;
/**
* This map holds Promise instances for each read-only tx. It is used to maintain ordering of tx creates
* wrt to read-only tx's between this class and a LocalTransactionChain since they're bridged by
* asynchronous futures. Otherwise, in the following scenario, eg:
* <p/>
* 1) Create write tx1 on chain
* 2) do write and submit
* 3) Create read-only tx2 on chain and issue read
* 4) Create write tx3 on chain, do write but do not submit
* <p/>
* if the sequence/timing is right, tx3 may create its local tx on the LocalTransactionChain before tx2,
* which results in tx2 failing b/c tx3 isn't ready yet. So maintaining ordering prevents this issue
* (see Bug 4774).
* <p/>
* A Promise is added via newReadOnlyTransaction. When the parent class completes the primary shard
* lookup and creates the TransactionContext (either success or failure), onTransactionContextCreated is
* called which completes the Promise. A write tx that is created prior to completion will wait on the
* Promise's Future via findPrimaryShard.
*/
private final ConcurrentMap<TransactionIdentifier, Promise<Object>> priorReadOnlyTxPromises =
new ConcurrentHashMap<>();
TransactionChainProxy(final TransactionContextFactory parent, final LocalHistoryIdentifier historyId) {
super(parent.getActorContext(), historyId);
this.parent = parent;
}
@Override
public DOMStoreReadTransaction newReadOnlyTransaction() {
currentState.checkReady();
TransactionProxy transactionProxy = new TransactionProxy(this, TransactionType.READ_ONLY);
priorReadOnlyTxPromises.put(transactionProxy.getIdentifier(), Futures.<Object>promise());
return transactionProxy;
}
@Override
public DOMStoreReadWriteTransaction newReadWriteTransaction() {
getActorContext().acquireTxCreationPermit();
return allocateWriteTransaction(TransactionType.READ_WRITE);
}
@Override
public DOMStoreWriteTransaction newWriteOnlyTransaction() {
getActorContext().acquireTxCreationPermit();
return allocateWriteTransaction(TransactionType.WRITE_ONLY);
}
@Override
public void close() {
currentState = CLOSED_STATE;
// Send a close transaction chain request to each and every shard
getActorContext().broadcast(version -> new CloseTransactionChain(getHistoryId(), version).toSerializable(),
CloseTransactionChain.class);
}
private TransactionProxy allocateWriteTransaction(final TransactionType type) {
State localState = currentState;
localState.checkReady();
final TransactionProxy ret = new TransactionProxy(this, type);
currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
return ret;
}
@Override
protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader,
final DataTree dataTree) {
final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
return ret;
}
/**
* This method is overridden to ensure the previous Tx's ready operations complete
* before we initiate the next Tx in the chain to avoid creation failures if the
* previous Tx's ready operations haven't completed yet.
*/
@SuppressWarnings({ "unchecked", "rawtypes" })
@Override
protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
// Read current state atomically
final State localState = currentState;
// There are no outstanding futures, shortcut
Future<?> previous = localState.previousFuture();
if (previous == null) {
return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
}
final String previousTransactionId;
if (localState instanceof Pending) {
previousTransactionId = ((Pending) localState).getIdentifier().toString();
LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
} else {
previousTransactionId = "";
LOG.debug("Waiting for ready futures on chain {}", getHistoryId());
}
previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
// Add a callback for completion of the combined Futures.
final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
final OnComplete onComplete = new OnComplete() {
@Override
public void onComplete(final Throwable failure, final Object notUsed) {
if (failure != null) {
// A Ready Future failed so fail the returned Promise.
LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
returnPromise.failure(failure);
} else {
LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
txId, previousTransactionId);
// Send the FindPrimaryShard message and use the resulting Future to complete the
// returned Promise.
returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
}
}
};
previous.onComplete(onComplete, getActorContext().getClientDispatcher());
return returnPromise.future();
}
private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
final TransactionIdentifier txId) {
if (!priorReadOnlyTxPromises.containsKey(txId) && !priorReadOnlyTxPromises.isEmpty()) {
Collection<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
new ArrayList<>(priorReadOnlyTxPromises.entrySet());
if (priorReadOnlyTxPromiseEntries.isEmpty()) {
return future;
}
List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
for (Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
priorReadOnlyTxFutures.add(entry.getValue().future());
}
Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
getActorContext().getClientDispatcher());
final Promise<T> returnPromise = Futures.promise();
final OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
@Override
public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
// Complete the returned Promise with the original Future.
returnPromise.completeWith(future);
}
};
combinedFutures.onComplete(onComplete, getActorContext().getClientDispatcher());
return returnPromise.future();
} else {
return future;
}
}
@Override
protected <T> void onTransactionReady(final TransactionIdentifier transaction,
final Collection<Future<T>> cohortFutures) {
final State localState = currentState;
Preconditions.checkState(localState instanceof Allocated, "Readying transaction %s while state is %s",
transaction, localState);
final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
Preconditions.checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated",
transaction, currentTx);
// Transaction ready and we are not waiting for futures -- go to idle
if (cohortFutures.isEmpty()) {
currentState = IDLE_STATE;
return;
}
// Combine the ready Futures into 1
final Future<Iterable<T>> combined = Futures.sequence(cohortFutures, getActorContext().getClientDispatcher());
// Record the we have outstanding futures
final State newState = new Submitted(transaction, combined);
currentState = newState;
// Attach a completion reset, but only if we do not allocate a transaction
// in-between
combined.onComplete(new OnComplete<Iterable<T>>() {
@Override
public void onComplete(final Throwable arg0, final Iterable<T> arg1) {
STATE_UPDATER.compareAndSet(TransactionChainProxy.this, newState, IDLE_STATE);
}
}, getActorContext().getClientDispatcher());
}
@Override
protected void onTransactionContextCreated(@Nonnull TransactionIdentifier transactionId) {
Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
if (promise != null) {
promise.success(null);
}
}
}