src/java/org/apache/cassandra/hadoop/ColumnFamilyOutputFormat.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.cassandra.hadoop;


import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.List;
import org.apache.cassandra.thrift.*;
import org.apache.hadoop.mapreduce.*;

/**
 * The <code>ColumnFamilyOutputFormat</code> acts as a Hadoop-specific
 * OutputFormat that allows reduce tasks to store keys (and corresponding
 * values) as Cassandra rows (and respective columns) in a given
 * ColumnFamily.
 *
 * <p>
 * As is the case with the {@link ColumnFamilyInputFormat}, you need to set the
 * Keyspace and ColumnFamily in your
 * Hadoop job Configuration. The {@link ConfigHelper} class, through its
 * {@link ConfigHelper#setOutputColumnFamily} method, is provided to make this
 * simple.
 * </p>
 *
 * <p>
 * For the sake of performance, this class employs a lazy write-back caching
 * mechanism, where its record writer batches mutations created based on the
 * reduce's inputs (in a task-specific map), and periodically makes the changes
 * official by sending a batch mutate request to Cassandra.
 * </p>
 */
public class ColumnFamilyOutputFormat extends AbstractColumnFamilyOutputFormat<ByteBuffer,List<Mutation>>
{
    /** Fills the deprecated OutputFormat interface for streaming. */
    @Deprecated
    public ColumnFamilyRecordWriter getRecordWriter(org.apache.hadoop.fs.FileSystem filesystem, org.apache.hadoop.mapred.JobConf job, String name, org.apache.hadoop.util.Progressable progress)
    {
        return new ColumnFamilyRecordWriter(job, progress);
    }

    /**
     * Get the {@link RecordWriter} for the given task.
     *
     * @param context
     *            the information about the current task.
     * @return a {@link RecordWriter} to write the output for the job.
     * @throws IOException
     */
    public ColumnFamilyRecordWriter getRecordWriter(final TaskAttemptContext context) throws InterruptedException
    {
        return new ColumnFamilyRecordWriter(context);
    }
}