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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; import java.io.IOException; import java.text.NumberFormat; import org.apache.hadoop.classification.InterfaceAudience; import org.apache.hadoop.classification.InterfaceAudience.Private; import org.apache.hadoop.classification.InterfaceStability; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.compress.CompressionCodec; import org.apache.hadoop.mapreduce.security.TokenCache; import org.apache.hadoop.util.Progressable; /** A base class for {@link OutputFormat}. */ @InterfaceAudience.Public @InterfaceStability.Stable public abstract class FileOutputFormat<K, V> implements OutputFormat<K, V> { @Deprecated public enum Counter { BYTES_WRITTEN } /** * Set whether the output of the job is compressed. * @param conf the {@link JobConf} to modify * @param compress should the output of the job be compressed? */ public static void setCompressOutput(JobConf conf, boolean compress) { conf.setBoolean(org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.COMPRESS, compress); } /** * Is the job output compressed? * @param conf the {@link JobConf} to look in * @return <code>true</code> if the job output should be compressed, * <code>false</code> otherwise */ public static boolean getCompressOutput(JobConf conf) { return conf.getBoolean(org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.COMPRESS, false); } /** * Set the {@link CompressionCodec} to be used to compress job outputs. * @param conf the {@link JobConf} to modify * @param codecClass the {@link CompressionCodec} to be used to * compress the job outputs */ public static void setOutputCompressorClass(JobConf conf, Class<? extends CompressionCodec> codecClass) { setCompressOutput(conf, true); conf.setClass(org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.COMPRESS_CODEC, codecClass, CompressionCodec.class); } /** * Get the {@link CompressionCodec} for compressing the job outputs. * @param conf the {@link JobConf} to look in * @param defaultValue the {@link CompressionCodec} to return if not set * @return the {@link CompressionCodec} to be used to compress the * job outputs * @throws IllegalArgumentException if the class was specified, but not found */ public static Class<? extends CompressionCodec> getOutputCompressorClass(JobConf conf, Class<? extends CompressionCodec> defaultValue) { Class<? extends CompressionCodec> codecClass = defaultValue; String name = conf.get(org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.COMPRESS_CODEC); if (name != null) { try { codecClass = conf.getClassByName(name).asSubclass(CompressionCodec.class); } catch (ClassNotFoundException e) { throw new IllegalArgumentException("Compression codec " + name + " was not found.", e); } } return codecClass; } public abstract RecordWriter<K, V> getRecordWriter(FileSystem ignored, JobConf job, String name, Progressable progress) throws IOException; public void checkOutputSpecs(FileSystem ignored, JobConf job) throws FileAlreadyExistsException, InvalidJobConfException, IOException { // Ensure that the output directory is set and not already there Path outDir = getOutputPath(job); if (outDir == null && job.getNumReduceTasks() != 0) { throw new InvalidJobConfException("Output directory not set in JobConf."); } if (outDir != null) { FileSystem fs = outDir.getFileSystem(job); // normalize the output directory outDir = fs.makeQualified(outDir); setOutputPath(job, outDir); // get delegation token for the outDir's file system TokenCache.obtainTokensForNamenodes(job.getCredentials(), new Path[] { outDir }, job); // check its existence if (fs.exists(outDir)) { throw new FileAlreadyExistsException("Output directory " + outDir + " already exists"); } } } /** * Set the {@link Path} of the output directory for the map-reduce job. * * @param conf The configuration of the job. * @param outputDir the {@link Path} of the output directory for * the map-reduce job. */ public static void setOutputPath(JobConf conf, Path outputDir) { outputDir = new Path(conf.getWorkingDirectory(), outputDir); conf.set(org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.OUTDIR, outputDir.toString()); } /** * Set the {@link Path} of the task's temporary output directory * for the map-reduce job. * * <p><i>Note</i>: Task output path is set by the framework. * </p> * @param conf The configuration of the job. * @param outputDir the {@link Path} of the output directory * for the map-reduce job. */ @Private public static void setWorkOutputPath(JobConf conf, Path outputDir) { outputDir = new Path(conf.getWorkingDirectory(), outputDir); conf.set(JobContext.TASK_OUTPUT_DIR, outputDir.toString()); } /** * Get the {@link Path} to the output directory for the map-reduce job. * * @return the {@link Path} to the output directory for the map-reduce job. * @see FileOutputFormat#getWorkOutputPath(JobConf) */ public static Path getOutputPath(JobConf conf) { String name = conf.get(org.apache.hadoop.mapreduce.lib.output.FileOutputFormat.OUTDIR); return name == null ? null : new Path(name); } /** * Get the {@link Path} to the task's temporary output directory * for the map-reduce job * * <b id="SideEffectFiles">Tasks' Side-Effect Files</b> * * <p><i>Note:</i> The following is valid only if the {@link OutputCommitter} * is {@link FileOutputCommitter}. If <code>OutputCommitter</code> is not * a <code>FileOutputCommitter</code>, the task's temporary output * directory is same as {@link #getOutputPath(JobConf)} i.e. * <tt>${mapreduce.output.fileoutputformat.outputdir}$</tt></p> * * <p>Some applications need to create/write-to side-files, which differ from * the actual job-outputs. * * <p>In such cases there could be issues with 2 instances of the same TIP * (running simultaneously e.g. speculative tasks) trying to open/write-to the * same file (path) on HDFS. Hence the application-writer will have to pick * unique names per task-attempt (e.g. using the attemptid, say * <tt>attempt_200709221812_0001_m_000000_0</tt>), not just per TIP.</p> * * <p>To get around this the Map-Reduce framework helps the application-writer * out by maintaining a special * <tt>${mapreduce.output.fileoutputformat.outputdir}/_temporary/_${taskid}</tt> * sub-directory for each task-attempt on HDFS where the output of the * task-attempt goes. On successful completion of the task-attempt the files * in the <tt>${mapreduce.output.fileoutputformat.outputdir}/_temporary/_${taskid}</tt> (only) * are <i>promoted</i> to <tt>${mapreduce.output.fileoutputformat.outputdir}</tt>. Of course, the * framework discards the sub-directory of unsuccessful task-attempts. This * is completely transparent to the application.</p> * * <p>The application-writer can take advantage of this by creating any * side-files required in <tt>${mapreduce.task.output.dir}</tt> during execution * of his reduce-task i.e. via {@link #getWorkOutputPath(JobConf)}, and the * framework will move them out similarly - thus she doesn't have to pick * unique paths per task-attempt.</p> * * <p><i>Note</i>: the value of <tt>${mapreduce.task.output.dir}</tt> during * execution of a particular task-attempt is actually * <tt>${mapreduce.output.fileoutputformat.outputdir}/_temporary/_{$taskid}</tt>, and this value is * set by the map-reduce framework. So, just create any side-files in the * path returned by {@link #getWorkOutputPath(JobConf)} from map/reduce * task to take advantage of this feature.</p> * * <p>The entire discussion holds true for maps of jobs with * reducer=NONE (i.e. 0 reduces) since output of the map, in that case, * goes directly to HDFS.</p> * * @return the {@link Path} to the task's temporary output directory * for the map-reduce job. */ public static Path getWorkOutputPath(JobConf conf) { String name = conf.get(JobContext.TASK_OUTPUT_DIR); return name == null ? null : new Path(name); } /** * Helper function to create the task's temporary output directory and * return the path to the task's output file. * * @param conf job-configuration * @param name temporary task-output filename * @return path to the task's temporary output file * @throws IOException */ public static Path getTaskOutputPath(JobConf conf, String name) throws IOException { // ${mapred.out.dir} Path outputPath = getOutputPath(conf); if (outputPath == null) { throw new IOException("Undefined job output-path"); } OutputCommitter committer = conf.getOutputCommitter(); Path workPath = outputPath; TaskAttemptContext context = new TaskAttemptContextImpl(conf, TaskAttemptID.forName(conf.get(JobContext.TASK_ATTEMPT_ID))); if (committer instanceof FileOutputCommitter) { workPath = ((FileOutputCommitter) committer).getWorkPath(context, outputPath); } // ${mapred.out.dir}/_temporary/_${taskid}/${name} return new Path(workPath, name); } /** * Helper function to generate a name that is unique for the task. * * <p>The generated name can be used to create custom files from within the * different tasks for the job, the names for different tasks will not collide * with each other.</p> * * <p>The given name is postfixed with the task type, 'm' for maps, 'r' for * reduces and the task partition number. For example, give a name 'test' * running on the first map o the job the generated name will be * 'test-m-00000'.</p> * * @param conf the configuration for the job. * @param name the name to make unique. * @return a unique name accross all tasks of the job. */ public static String getUniqueName(JobConf conf, String name) { int partition = conf.getInt(JobContext.TASK_PARTITION, -1); if (partition == -1) { throw new IllegalArgumentException("This method can only be called from within a Job"); } String taskType = conf.getBoolean(JobContext.TASK_ISMAP, JobContext.DEFAULT_TASK_ISMAP) ? "m" : "r"; NumberFormat numberFormat = NumberFormat.getInstance(); numberFormat.setMinimumIntegerDigits(5); numberFormat.setGroupingUsed(false); return name + "-" + taskType + "-" + numberFormat.format(partition); } /** * Helper function to generate a {@link Path} for a file that is unique for * the task within the job output directory. * * <p>The path can be used to create custom files from within the map and * reduce tasks. The path name will be unique for each task. The path parent * will be the job output directory.</p>ls * * <p>This method uses the {@link #getUniqueName} method to make the file name * unique for the task.</p> * * @param conf the configuration for the job. * @param name the name for the file. * @return a unique path accross all tasks of the job. */ public static Path getPathForCustomFile(JobConf conf, String name) { return new Path(getWorkOutputPath(conf), getUniqueName(conf, name)); } }