/*
* Copyright © 2014 Cask Data, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package co.cask.cdap.data2.transaction.queue.inmemory;
import co.cask.cdap.common.queue.QueueName;
import co.cask.cdap.common.utils.ImmutablePair;
import co.cask.cdap.data2.queue.ConsumerConfig;
import co.cask.cdap.data2.queue.DequeueResult;
import co.cask.cdap.data2.queue.DequeueStrategy;
import co.cask.cdap.data2.queue.QueueConsumer;
import co.cask.tephra.Transaction;
import co.cask.tephra.TransactionAware;
import com.google.common.collect.ImmutableList;
import java.io.IOException;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
/**
* Consumer for an in-memory queue.
*/
public class InMemoryQueueConsumer implements QueueConsumer, TransactionAware {
private static final DequeueResult<byte[]> EMPTY_RESULT = DequeueResult.Empty.result();
private final QueueName queueName;
private Transaction currentTx;
private boolean committed = false;
private final ConsumerConfig config;
private final int numGroups;
private List<InMemoryQueue.Key> dequeuedKeys;
private final InMemoryQueue.ConsumerState state = new InMemoryQueue.ConsumerState();
private final InMemoryQueueService queueService;
public InMemoryQueueConsumer(QueueName queueName, ConsumerConfig config,
int numGroups, InMemoryQueueService queueService) {
this.queueName = queueName;
this.queueService = queueService;
this.config = config;
this.numGroups = numGroups;
}
private InMemoryQueue getQueue() {
return queueService.getQueue(queueName);
}
@Override
public String getTransactionAwareName() {
return getClass().getSimpleName() + "(queue = " + queueName + ")";
}
@Override
public QueueName getQueueName() {
return queueName;
}
@Override
public ConsumerConfig getConfig() {
return config;
}
@Override
public DequeueResult dequeue() throws IOException {
return dequeue(1);
}
@Override
public DequeueResult dequeue(int maxBatchSize) throws IOException {
ImmutablePair<List<InMemoryQueue.Key>, List<byte[]>> result =
getQueue().dequeue(currentTx, config, state, maxBatchSize);
if (result == null) {
return EMPTY_RESULT;
} else {
dequeuedKeys = result.getFirst();
return new InMemoryDequeueResult(result);
}
}
@Override
public void startTx(Transaction tx) {
currentTx = tx;
dequeuedKeys = null;
committed = false;
}
@Override
public void updateTx(Transaction transaction) {
currentTx = transaction;
}
@Override
public Collection<byte[]> getTxChanges() {
return ImmutableList.of(); // no conflicts generated by queues
}
@Override
public boolean commitTx() throws Exception {
getQueue().ack(dequeuedKeys, config);
committed = true;
return true;
}
@Override
public void postTxCommit() {
getQueue().evict(dequeuedKeys, numGroups);
}
@Override
public boolean rollbackTx() throws Exception {
if (committed || DequeueStrategy.FIFO.equals(config.getDequeueStrategy())) {
if (dequeuedKeys != null) {
getQueue().undoDequeue(dequeuedKeys, config);
}
}
dequeuedKeys = null;
return true;
}
@Override
public void close() throws IOException {
// No-op
}
private final class InMemoryDequeueResult implements DequeueResult<byte[]> {
private final List<InMemoryQueue.Key> keys;
private final List<byte[]> data;
InMemoryDequeueResult(ImmutablePair<List<InMemoryQueue.Key>, List<byte[]>> result) {
this.keys = ImmutableList.copyOf(result.getFirst());
this.data = ImmutableList.copyOf(result.getSecond());
}
@Override
public boolean isEmpty() {
return data.isEmpty();
}
@Override
public void reclaim() {
if (dequeuedKeys != null) {
dequeuedKeys.addAll(keys);
} else {
dequeuedKeys = keys;
}
}
@Override
public int size() {
return keys.size();
}
@Override
public Iterator<byte[]> iterator() {
return data.iterator();
}
}
}