| /** |
| * 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.mapreduce.lib.output; |
| |
| import java.io.IOException; |
| import java.text.NumberFormat; |
| |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.fs.FileSystem; |
| import org.apache.hadoop.fs.Path; |
| import org.apache.hadoop.io.compress.CompressionCodec; |
| import org.apache.hadoop.fs.FileAlreadyExistsException; |
| import org.apache.hadoop.mapred.InvalidJobConfException; |
| import org.apache.hadoop.mapreduce.Job; |
| import org.apache.hadoop.mapreduce.JobContext; |
| import org.apache.hadoop.mapreduce.OutputCommitter; |
| import org.apache.hadoop.mapreduce.OutputFormat; |
| import org.apache.hadoop.mapreduce.RecordWriter; |
| import org.apache.hadoop.mapreduce.TaskAttemptContext; |
| import org.apache.hadoop.mapreduce.TaskID; |
| import org.apache.hadoop.mapreduce.TaskInputOutputContext; |
| |
| /** A base class for {@link OutputFormat}s that read from {@link FileSystem}s.*/ |
| public abstract class FileOutputFormat<K, V> extends OutputFormat<K, V> { |
| |
| /** Construct output file names so that, when an output directory listing is |
| * sorted lexicographically, positions correspond to output partitions.*/ |
| private static final NumberFormat NUMBER_FORMAT = NumberFormat.getInstance(); |
| protected static final String BASE_OUTPUT_NAME = "mapreduce.output.basename"; |
| protected static final String PART = "part"; |
| static { |
| NUMBER_FORMAT.setMinimumIntegerDigits(5); |
| NUMBER_FORMAT.setGroupingUsed(false); |
| } |
| private FileOutputCommitter committer = null; |
| public static final String COMPRESS ="mapreduce.output.fileoutputformat.compress"; |
| public static final String COMPRESS_CODEC = |
| "mapreduce.output.fileoutputformat.compress.codec"; |
| public static final String COMPRESS_TYPE = "mapreduce.output.fileoutputformat.compress.type"; |
| public static final String OUTDIR = "mapreduce.output.fileoutputformat.outputdir"; |
| |
| /** |
| * Set whether the output of the job is compressed. |
| * @param job the job to modify |
| * @param compress should the output of the job be compressed? |
| */ |
| public static void setCompressOutput(Job job, boolean compress) { |
| job.getConfiguration().setBoolean(FileOutputFormat.COMPRESS, compress); |
| } |
| |
| /** |
| * Is the job output compressed? |
| * @param job the Job to look in |
| * @return <code>true</code> if the job output should be compressed, |
| * <code>false</code> otherwise |
| */ |
| public static boolean getCompressOutput(JobContext job) { |
| return job.getConfiguration().getBoolean( |
| FileOutputFormat.COMPRESS, false); |
| } |
| |
| /** |
| * Set the {@link CompressionCodec} to be used to compress job outputs. |
| * @param job the job to modify |
| * @param codecClass the {@link CompressionCodec} to be used to |
| * compress the job outputs |
| */ |
| public static void |
| setOutputCompressorClass(Job job, |
| Class<? extends CompressionCodec> codecClass) { |
| setCompressOutput(job, true); |
| job.getConfiguration().setClass(FileOutputFormat.COMPRESS_CODEC, |
| codecClass, |
| CompressionCodec.class); |
| } |
| |
| /** |
| * Get the {@link CompressionCodec} for compressing the job outputs. |
| * @param job the {@link Job} 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(JobContext job, |
| Class<? extends CompressionCodec> defaultValue) { |
| Class<? extends CompressionCodec> codecClass = defaultValue; |
| Configuration conf = job.getConfiguration(); |
| String name = conf.get(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(TaskAttemptContext job |
| ) throws IOException, InterruptedException; |
| |
| public void checkOutputSpecs(JobContext job |
| ) throws FileAlreadyExistsException, IOException{ |
| // Ensure that the output directory is set and not already there |
| Path outDir = getOutputPath(job); |
| if (outDir == null) { |
| throw new InvalidJobConfException("Output directory not set."); |
| } |
| if (outDir.getFileSystem(job.getConfiguration()).exists(outDir)) { |
| throw new FileAlreadyExistsException("Output directory " + outDir + |
| " already exists"); |
| } |
| } |
| |
| /** |
| * Set the {@link Path} of the output directory for the map-reduce job. |
| * |
| * @param job The job to modify |
| * @param outputDir the {@link Path} of the output directory for |
| * the map-reduce job. |
| */ |
| public static void setOutputPath(Job job, Path outputDir) { |
| job.getConfiguration().set(FileOutputFormat.OUTDIR, 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(TaskInputOutputContext) |
| */ |
| public static Path getOutputPath(JobContext job) { |
| String name = job.getConfiguration().get(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 |
| * |
| * <h4 id="SideEffectFiles">Tasks' Side-Effect Files</h4> |
| * |
| * <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 a work directory during execution |
| * of his task i.e. via |
| * {@link #getWorkOutputPath(TaskInputOutputContext)}, and |
| * the framework will move them out similarly - thus she doesn't have to pick |
| * unique paths per task-attempt.</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(TaskInputOutputContext<?,?,?,?> context |
| ) throws IOException, |
| InterruptedException { |
| FileOutputCommitter committer = (FileOutputCommitter) |
| context.getOutputCommitter(); |
| return committer.getWorkPath(); |
| } |
| |
| /** |
| * 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 #getUniqueFile} method to make the file name |
| * unique for the task.</p> |
| * |
| * @param context the context for the task. |
| * @param name the name for the file. |
| * @param extension the extension for the file |
| * @return a unique path accross all tasks of the job. |
| */ |
| public |
| static Path getPathForWorkFile(TaskInputOutputContext<?,?,?,?> context, |
| String name, |
| String extension |
| ) throws IOException, InterruptedException { |
| return new Path(getWorkOutputPath(context), |
| getUniqueFile(context, name, extension)); |
| } |
| |
| /** |
| * Generate a unique filename, based on the task id, name, and extension |
| * @param context the task that is calling this |
| * @param name the base filename |
| * @param extension the filename extension |
| * @return a string like $name-[mrsct]-$id$extension |
| */ |
| public synchronized static String getUniqueFile(TaskAttemptContext context, |
| String name, |
| String extension) { |
| TaskID taskId = context.getTaskAttemptID().getTaskID(); |
| int partition = taskId.getId(); |
| StringBuilder result = new StringBuilder(); |
| result.append(name); |
| result.append('-'); |
| result.append( |
| TaskID.getRepresentingCharacter(taskId.getTaskType())); |
| result.append('-'); |
| result.append(NUMBER_FORMAT.format(partition)); |
| result.append(extension); |
| return result.toString(); |
| } |
| |
| /** |
| * Get the default path and filename for the output format. |
| * @param context the task context |
| * @param extension an extension to add to the filename |
| * @return a full path $output/_temporary/$taskid/part-[mr]-$id |
| * @throws IOException |
| */ |
| public Path getDefaultWorkFile(TaskAttemptContext context, |
| String extension) throws IOException{ |
| FileOutputCommitter committer = |
| (FileOutputCommitter) getOutputCommitter(context); |
| return new Path(committer.getWorkPath(), getUniqueFile(context, |
| getOutputName(context), extension)); |
| } |
| |
| /** |
| * Get the base output name for the output file. |
| */ |
| protected static String getOutputName(JobContext job) { |
| return job.getConfiguration().get(BASE_OUTPUT_NAME, PART); |
| } |
| |
| /** |
| * Set the base output name for output file to be created. |
| */ |
| protected static void setOutputName(JobContext job, String name) { |
| job.getConfiguration().set(BASE_OUTPUT_NAME, name); |
| } |
| |
| public synchronized |
| OutputCommitter getOutputCommitter(TaskAttemptContext context |
| ) throws IOException { |
| if (committer == null) { |
| Path output = getOutputPath(context); |
| committer = new FileOutputCommitter(output, context); |
| } |
| return committer; |
| } |
| } |
| |
