org.apache.hadoop.mapred.lib.LazyOutputFormat.java Source code

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Here is the source code for org.apache.hadoop.mapred.lib.LazyOutputFormat.java

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/**
 * 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.hadoop.mapred.lib;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.OutputFormat;
import org.apache.hadoop.mapred.RecordWriter;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.util.Progressable;
import org.apache.hadoop.util.ReflectionUtils;

/**
 * A Convenience class that creates output lazily. 
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class LazyOutputFormat<K, V> extends FilterOutputFormat<K, V> {
    /**
     * Set the underlying output format for LazyOutputFormat.
     * @param job the {@link JobConf} to modify
     * @param theClass the underlying class
     */
    @SuppressWarnings("unchecked")
    public static void setOutputFormatClass(JobConf job, Class<? extends OutputFormat> theClass) {
        job.setOutputFormat(LazyOutputFormat.class);
        job.setClass("mapreduce.output.lazyoutputformat.outputformat", theClass, OutputFormat.class);
    }

    @Override
    public RecordWriter<K, V> getRecordWriter(FileSystem ignored, JobConf job, String name, Progressable progress)
            throws IOException {
        if (baseOut == null) {
            getBaseOutputFormat(job);
        }
        return new LazyRecordWriter<K, V>(job, baseOut, name, progress);
    }

    @Override
    public void checkOutputSpecs(FileSystem ignored, JobConf job) throws IOException {
        if (baseOut == null) {
            getBaseOutputFormat(job);
        }
        super.checkOutputSpecs(ignored, job);
    }

    @SuppressWarnings("unchecked")
    private void getBaseOutputFormat(JobConf job) throws IOException {
        baseOut = ReflectionUtils.newInstance(
                job.getClass("mapreduce.output.lazyoutputformat.outputformat", null, OutputFormat.class), job);
        if (baseOut == null) {
            throw new IOException("Ouput format not set for LazyOutputFormat");
        }
    }

    /**
     * <code>LazyRecordWriter</code> is a convenience 
     * class that works with LazyOutputFormat.
     */

    private static class LazyRecordWriter<K, V> extends FilterRecordWriter<K, V> {

        final OutputFormat of;
        final String name;
        final Progressable progress;
        final JobConf job;

        public LazyRecordWriter(JobConf job, OutputFormat of, String name, Progressable progress)
                throws IOException {
            this.of = of;
            this.job = job;
            this.name = name;
            this.progress = progress;
        }

        @Override
        public void close(Reporter reporter) throws IOException {
            if (rawWriter != null) {
                rawWriter.close(reporter);
            }
        }

        @Override
        public void write(K key, V value) throws IOException {
            if (rawWriter == null) {
                createRecordWriter();
            }
            super.write(key, value);
        }

        @SuppressWarnings("unchecked")
        private void createRecordWriter() throws IOException {
            FileSystem fs = FileSystem.get(job);
            rawWriter = of.getRecordWriter(fs, job, name, progress);
        }
    }
}