/**
* (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;
}
}