org.kiji.mapreduce.gather.impl.GatherMapper.java Source code

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Here is the source code for org.kiji.mapreduce.gather.impl.GatherMapper.java

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/**
 * (c) Copyright 2012 WibiData, Inc.
 *
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * 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 org.kiji.mapreduce.gather.impl;

import java.io.IOException;

import com.google.common.base.Preconditions;
import org.apache.avro.Schema;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.util.ReflectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.kiji.annotations.ApiAudience;
import org.kiji.mapreduce.avro.AvroKeyWriter;
import org.kiji.mapreduce.avro.AvroValueWriter;
import org.kiji.mapreduce.framework.JobHistoryCounters;
import org.kiji.mapreduce.framework.KijiConfKeys;
import org.kiji.mapreduce.gather.GathererContext;
import org.kiji.mapreduce.gather.KijiGatherer;
import org.kiji.mapreduce.impl.KijiTableMapper;
import org.kiji.schema.KijiDataRequest;
import org.kiji.schema.KijiRowData;

/**
 * Mapper that executes a gatherer over the rows of a Kiji table.
 *
 * @param <K> The type of the MapReduce output key.
 * @param <V> The type of the MapReduce output value.
 */
@ApiAudience.Private
public final class GatherMapper<K, V> extends KijiTableMapper<K, V> implements AvroKeyWriter, AvroValueWriter {

    private static final Logger LOG = LoggerFactory.getLogger(GatherMapper.class);

    /** The gatherer to execute. */
    private KijiGatherer<K, V> mGatherer;

    /**
     * The context object that allows the gatherer to interact with MapReduce,
     * KVStores, etc.
     */
    private GathererContext<K, V> mGathererContext;

    @Override
    public void setConf(Configuration conf) {
        super.setConf(conf);
        setGatherer(createGatherer(conf));
    }

    /**
     * Return a KijiDataRequest that describes which input columns need to be available.
     *
     * @return A kiji data request.
     */
    public KijiDataRequest getDataRequest() {
        return mGatherer.getDataRequest();
    }

    /** {@inheritDoc} */
    @Override
    public Class<?> getOutputKeyClass() {
        return mGatherer.getOutputKeyClass();
    }

    /** {@inheritDoc} */
    @Override
    public Class<?> getOutputValueClass() {
        return mGatherer.getOutputValueClass();
    }

    /**
     * Initialize the gatherer instance to execute.
     *
     * @param conf the Configuration to use to initialize the gatherer instance.
     * @return a KijiGatherer instance.
     */
    protected KijiGatherer<K, V> createGatherer(Configuration conf) {
        @SuppressWarnings("unchecked")
        Class<? extends KijiGatherer<K, V>> gatherClass = (Class<? extends KijiGatherer<K, V>>) conf
                .getClass(KijiConfKeys.KIJI_GATHERER_CLASS, null, KijiGatherer.class);
        if (null == gatherClass) {
            LOG.error("Null " + KijiConfKeys.KIJI_GATHERER_CLASS + " in createGatherer()?");
            return null;
        }
        return ReflectionUtils.newInstance(gatherClass, conf);
    }

    /**
     * Set the gatherer instance to use for the scan.
     *
     * @param gatherer the gatherer instance to use.
     */
    private void setGatherer(KijiGatherer<K, V> gatherer) {
        mGatherer = gatherer;
    }

    /** {@inheritDoc} */
    @Override
    protected void setup(Context context) throws IOException {
        super.setup(context);

        Preconditions.checkState(null == mGathererContext);
        setConf(context.getConfiguration());

        mGathererContext = InternalGathererContext.create(context);
        mGatherer.setup(mGathererContext);
    }

    /** {@inheritDoc} */
    @Override
    protected void map(KijiRowData input, Context context) throws IOException {
        Preconditions.checkNotNull(mGathererContext);
        mGatherer.gather(input, mGathererContext);
        mGathererContext.incrementCounter(JobHistoryCounters.GATHERER_ROWS_PROCESSED);
    }

    /** {@inheritDoc} */
    @Override
    protected void cleanup(Context context) throws IOException {
        Preconditions.checkNotNull(mGathererContext);
        mGatherer.cleanup(mGathererContext);
        mGathererContext.close();
        mGathererContext = null;

        super.cleanup(context);
    }

    /** {@inheritDoc} */
    @Override
    public Schema getAvroKeyWriterSchema() throws IOException {
        if (mGatherer instanceof AvroKeyWriter) {
            LOG.debug("Gatherer " + mGatherer.getClass().getName()
                    + " implements AvroKeyWriter, querying for writer schema.");
            return ((AvroKeyWriter) mGatherer).getAvroKeyWriterSchema();
        }
        return null;
    }

    /** {@inheritDoc} */
    @Override
    public Schema getAvroValueWriterSchema() throws IOException {
        if (mGatherer instanceof AvroValueWriter) {
            LOG.debug("Gatherer " + mGatherer.getClass().getName()
                    + " implements AvroValueWriter, querying for writer schema.");
            return ((AvroValueWriter) mGatherer).getAvroValueWriterSchema();
        }
        return null;
    }
}