co.cask.cdap.data2.transaction.queue.leveldb.LevelDBQueueProducer.java Source code

Introduction

Here is the source code for co.cask.cdap.data2.transaction.queue.leveldb.LevelDBQueueProducer.java

Source

/*
 * 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.leveldb;

import co.cask.cdap.api.common.Bytes;
import co.cask.cdap.common.queue.QueueName;
import co.cask.cdap.data2.dataset2.lib.table.leveldb.KeyValue;
import co.cask.cdap.data2.dataset2.lib.table.leveldb.LevelDBTableCore;
import co.cask.cdap.data2.queue.QueueEntry;
import co.cask.cdap.data2.transaction.queue.AbstractQueueProducer;
import co.cask.cdap.data2.transaction.queue.QueueEntryRow;
import co.cask.cdap.data2.transaction.queue.QueueMetrics;
import co.cask.tephra.Transaction;
import com.google.common.collect.Maps;

import java.util.NavigableMap;

/**
 * A queue producer for levelDB.
 */
public final class LevelDBQueueProducer extends AbstractQueueProducer {

    private final LevelDBTableCore core;
    private final byte[] queueRowPrefix;
    private final NavigableMap<byte[], NavigableMap<byte[], byte[]>> changes;

    public LevelDBQueueProducer(LevelDBTableCore tableCore, QueueName queueName, QueueMetrics queueMetrics) {
        super(queueMetrics, queueName);
        core = tableCore;
        changes = Maps.newTreeMap(Bytes.BYTES_COMPARATOR);
        queueRowPrefix = QueueEntryRow.getQueueRowPrefix(queueName);
    }

    @Override
    public void startTx(Transaction tx) {
        super.startTx(tx);
        changes.clear();
    }

    @Override
    protected int persist(Iterable<QueueEntry> entries, Transaction transaction) throws Exception {
        long writePointer = transaction.getWritePointer();
        byte[] rowKeyPrefix = Bytes.add(queueRowPrefix, Bytes.toBytes(writePointer));
        int count = 0;
        int bytes = 0;

        for (QueueEntry entry : entries) {
            // Row key = queue_name + writePointer + counter
            byte[] rowKey = Bytes.add(rowKeyPrefix, Bytes.toBytes(count++));
            NavigableMap<byte[], byte[]> row = Maps.newTreeMap(Bytes.BYTES_COMPARATOR);
            row.put(QueueEntryRow.DATA_COLUMN, entry.getData());
            row.put(QueueEntryRow.META_COLUMN, QueueEntry.serializeHashKeys(entry.getHashKeys()));
            changes.put(rowKey, row);
            bytes += entry.getData().length;
        }
        // TODO introduce a constant in the OcTableCore for the latest timestamp
        core.persist(changes, KeyValue.LATEST_TIMESTAMP);

        return bytes;
    }

    @Override
    protected void doRollback() throws Exception {
        core.undo(changes, KeyValue.LATEST_TIMESTAMP);
    }
}