co.cask.cdap.metrics.process.KafkaConsumerMetaTable.java Source code

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Here is the source code for co.cask.cdap.metrics.process.KafkaConsumerMetaTable.java

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/*
 * 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.metrics.process;

import co.cask.cdap.api.common.Bytes;
import co.cask.cdap.data2.dataset2.lib.table.MetricsTable;
import com.google.common.collect.Maps;
import org.apache.twill.kafka.client.TopicPartition;

import java.util.Map;
import java.util.NavigableMap;

/**
 * An abstraction on persistent storage of kafka consumer information.
 */
public final class KafkaConsumerMetaTable {

    private static final byte[] OFFSET_COLUMN = Bytes.toBytes("o");

    private final MetricsTable metaTable;

    public KafkaConsumerMetaTable(MetricsTable metaTable) {
        this.metaTable = metaTable;
    }

    public synchronized void save(Map<TopicPartition, Long> offsets) throws Exception {

        NavigableMap<byte[], NavigableMap<byte[], Long>> updates = Maps.newTreeMap(Bytes.BYTES_COMPARATOR);
        for (Map.Entry<TopicPartition, Long> entry : offsets.entrySet()) {
            updates.put(getKey(entry.getKey()), Bytes.immutableSortedMapOf(OFFSET_COLUMN, entry.getValue()));
        }
        metaTable.put(updates);
    }

    /**
     * Gets the offset of a given topic partition.
     * @param topicPartition The topic and partition to fetch offset.
     * @return The offset or {@code -1} if the offset is not found.
     * @throws Exception If there is an error when fetching.
     */
    public synchronized long get(TopicPartition topicPartition) throws Exception {
        byte[] result = metaTable.get(getKey(topicPartition), OFFSET_COLUMN);
        if (result == null) {
            return -1;
        }
        return Bytes.toLong(result);
    }

    private byte[] getKey(TopicPartition topicPartition) {
        return Bytes.toBytes(String.format("%s.%02d", topicPartition.getTopic(), topicPartition.getPartition()));
    }
}