Java tutorial
/** * 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 com.dinglicom.clouder.mapreduce.input; import java.io.IOException; import java.util.ArrayList; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.BlockLocation; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.fs.PathFilter; import org.apache.hadoop.mapreduce.InputFormat; import org.apache.hadoop.mapreduce.InputSplit; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.JobContext; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.lib.input.InvalidInputException; import org.apache.hadoop.mapreduce.security.TokenCache; import org.apache.hadoop.util.ReflectionUtils; import org.apache.hadoop.util.StringUtils; /** * A base class for file-based {@link InputFormat}s. * * <p><code>FileInputFormat</code> is the base class for all file-based * <code>InputFormat</code>s. This provides a generic implementation of * {@link #getSplits(JobContext)}. * Subclasses of <code>FileInputFormat</code> can also override the * {@link #isSplitable(JobContext, Path)} method to ensure input-files are * not split-up and are processed as a whole by {@link Mapper}s. */ //@InterfaceAudience.Public //@InterfaceStability.Stable public abstract class FileInputFormat<K, V> extends InputFormat<K, V> { public static final String INPUT_DIR = "mapreduce.input.fileinputformat.inputdir"; public static final String SPLIT_MAXSIZE = "mapreduce.input.fileinputformat.split.maxsize"; public static final String SPLIT_MINSIZE = "mapreduce.input.fileinputformat.split.minsize"; public static final String PATHFILTER_CLASS = "mapreduce.input.pathFilter.class"; public static final String NUM_INPUT_FILES = "mapreduce.input.fileinputformat.numinputfiles"; private static final Log LOG = LogFactory.getLog(FileInputFormat.class); private static final double SPLIT_SLOP = 1.1; // 10% slop private static final PathFilter hiddenFileFilter = new PathFilter() { public boolean accept(Path p) { String name = p.getName(); return !name.startsWith("_") && !name.startsWith("."); } }; /** * Proxy PathFilter that accepts a path only if all filters given in the * constructor do. Used by the listPaths() to apply the built-in * hiddenFileFilter together with a user provided one (if any). */ private static class MultiPathFilter implements PathFilter { private List<PathFilter> filters; public MultiPathFilter(List<PathFilter> filters) { this.filters = filters; } public boolean accept(Path path) { for (PathFilter filter : filters) { if (!filter.accept(path)) { return false; } } return true; } } /** * Get the lower bound on split size imposed by the format. * @return the number of bytes of the minimal split for this format */ protected long getFormatMinSplitSize() { return 1; } /** * Is the given filename splitable? Usually, true, but if the file is * stream compressed, it will not be. * * <code>FileInputFormat</code> implementations can override this and return * <code>false</code> to ensure that individual input files are never split-up * so that {@link Mapper}s process entire files. * * @param context the job context * @param filename the file name to check * @return is this file splitable? */ protected boolean isSplitable(JobContext context, Path filename) { return true; } /** * Set a PathFilter to be applied to the input paths for the map-reduce job. * @param job the job to modify * @param filter the PathFilter class use for filtering the input paths. */ public static void setInputPathFilter(Job job, Class<? extends PathFilter> filter) { job.getConfiguration().setClass(PATHFILTER_CLASS, filter, PathFilter.class); } /** * Set the minimum input split size * @param job the job to modify * @param size the minimum size */ public static void setMinInputSplitSize(Job job, long size) { job.getConfiguration().setLong(SPLIT_MINSIZE, size); } /** * Get the minimum split size * @param job the job * @return the minimum number of bytes that can be in a split */ public static long getMinSplitSize(JobContext job) { return job.getConfiguration().getLong(SPLIT_MINSIZE, 1L); } /** * Set the maximum split size * @param job the job to modify * @param size the maximum split size */ public static void setMaxInputSplitSize(Job job, long size) { job.getConfiguration().setLong(SPLIT_MAXSIZE, size); } /** * Get the maximum split size. * @param context the job to look at. * @return the maximum number of bytes a split can include */ public static long getMaxSplitSize(JobContext context) { return context.getConfiguration().getLong(SPLIT_MAXSIZE, Long.MAX_VALUE); } /** * Get a PathFilter instance of the filter set for the input paths. * * @return the PathFilter instance set for the job, NULL if none has been set. */ public static PathFilter getInputPathFilter(JobContext context) { Configuration conf = context.getConfiguration(); Class<?> filterClass = conf.getClass(PATHFILTER_CLASS, null, PathFilter.class); return (filterClass != null) ? (PathFilter) ReflectionUtils.newInstance(filterClass, conf) : null; } /** List input directories. * Subclasses may override to, e.g., select only files matching a regular * expression. * * @param job the job to list input paths for * @return array of FileStatus objects * @throws IOException if zero items. */ protected List<FileStatus> listStatus(JobContext job) throws IOException { List<FileStatus> result = new ArrayList<FileStatus>(); Path[] dirs = getInputPaths(job); if (dirs.length == 0) { throw new IOException("No input paths specified in job"); } // get tokens for all the required FileSystems.. TokenCache.obtainTokensForNamenodes(job.getCredentials(), dirs, job.getConfiguration()); List<IOException> errors = new ArrayList<IOException>(); // creates a MultiPathFilter with the hiddenFileFilter and the // user provided one (if any). List<PathFilter> filters = new ArrayList<PathFilter>(); filters.add(hiddenFileFilter); PathFilter jobFilter = getInputPathFilter(job); if (jobFilter != null) { filters.add(jobFilter); } PathFilter inputFilter = new MultiPathFilter(filters); for (int i = 0; i < dirs.length; ++i) { Path p = dirs[i]; FileSystem fs = p.getFileSystem(job.getConfiguration()); FileStatus[] matches = fs.globStatus(p, inputFilter); if (matches == null) { errors.add(new IOException("Input path does not exist: " + p)); } else if (matches.length == 0) { errors.add(new IOException("Input Pattern " + p + " matches 0 files")); } else { for (FileStatus globStat : matches) { if (globStat.isDirectory()) { for (FileStatus stat : fs.listStatus(globStat.getPath(), inputFilter)) { result.add(stat); } } else { result.add(globStat); } } } } if (!errors.isEmpty()) { throw new InvalidInputException(errors); } LOG.info("Total input paths to process : " + result.size()); return result; } /** * A factory that makes the split for this class. It can be overridden * by sub-classes to make sub-types */ protected FileSplit makeSplit(Path file, long start, long length, String[] hosts) { return new FileSplit(file, start, length, hosts); } /** * Generate the list of files and make them into FileSplits. * @param job the job context * @throws IOException */ public List<InputSplit> getSplits(JobContext job) throws IOException { long minSize = Math.max(getFormatMinSplitSize(), getMinSplitSize(job)); long maxSize = getMaxSplitSize(job); // generate splits List<InputSplit> splits = new ArrayList<InputSplit>(); List<FileStatus> files = listStatus(job); for (FileStatus file : files) { Path path = file.getPath(); long length = file.getLen(); if (length != 0) { FileSystem fs = path.getFileSystem(job.getConfiguration()); BlockLocation[] blkLocations = fs.getFileBlockLocations(file, 0, length); if (isSplitable(job, path)) { long blockSize = file.getBlockSize(); long splitSize = computeSplitSize(blockSize, minSize, maxSize); long bytesRemaining = length; while (((double) bytesRemaining) / splitSize > SPLIT_SLOP) { int blkIndex = getBlockIndex(blkLocations, length - bytesRemaining); splits.add(makeSplit(path, length - bytesRemaining, splitSize, blkLocations[blkIndex].getHosts())); bytesRemaining -= splitSize; } if (bytesRemaining != 0) { int blkIndex = getBlockIndex(blkLocations, length - bytesRemaining); splits.add(makeSplit(path, length - bytesRemaining, bytesRemaining, blkLocations[blkIndex].getHosts())); } } else { // not splitable splits.add(makeSplit(path, 0, length, blkLocations[0].getHosts())); } } else { //Create empty hosts array for zero length files splits.add(makeSplit(path, 0, length, new String[0])); } } // Save the number of input files for metrics/loadgen job.getConfiguration().setLong(NUM_INPUT_FILES, files.size()); LOG.debug("Total # of splits: " + splits.size()); return splits; } protected long computeSplitSize(long blockSize, long minSize, long maxSize) { return Math.max(minSize, Math.min(maxSize, blockSize)); } protected int getBlockIndex(BlockLocation[] blkLocations, long offset) { for (int i = 0; i < blkLocations.length; i++) { // is the offset inside this block? if ((blkLocations[i].getOffset() <= offset) && (offset < blkLocations[i].getOffset() + blkLocations[i].getLength())) { return i; } } BlockLocation last = blkLocations[blkLocations.length - 1]; long fileLength = last.getOffset() + last.getLength() - 1; throw new IllegalArgumentException("Offset " + offset + " is outside of file (0.." + fileLength + ")"); } /** * Sets the given comma separated paths as the list of inputs * for the map-reduce job. * * @param job the job * @param commaSeparatedPaths Comma separated paths to be set as * the list of inputs for the map-reduce job. */ public static void setInputPaths(Job job, String commaSeparatedPaths) throws IOException { setInputPaths(job, StringUtils.stringToPath(getPathStrings(commaSeparatedPaths))); } /** * Add the given comma separated paths to the list of inputs for * the map-reduce job. * * @param job The job to modify * @param commaSeparatedPaths Comma separated paths to be added to * the list of inputs for the map-reduce job. */ public static void addInputPaths(Job job, String commaSeparatedPaths) throws IOException { for (String str : getPathStrings(commaSeparatedPaths)) { addInputPath(job, new Path(str)); } } /** * Set the array of {@link Path}s as the list of inputs * for the map-reduce job. * * @param job The job to modify * @param inputPaths the {@link Path}s of the input directories/files * for the map-reduce job. */ public static void setInputPaths(Job job, Path... inputPaths) throws IOException { Configuration conf = job.getConfiguration(); Path path = inputPaths[0].getFileSystem(conf).makeQualified(inputPaths[0]); StringBuffer str = new StringBuffer(StringUtils.escapeString(path.toString())); for (int i = 1; i < inputPaths.length; i++) { str.append(StringUtils.COMMA_STR); path = inputPaths[i].getFileSystem(conf).makeQualified(inputPaths[i]); str.append(StringUtils.escapeString(path.toString())); } conf.set(INPUT_DIR, str.toString()); } /** * Add a {@link Path} to the list of inputs for the map-reduce job. * * @param job The {@link Job} to modify * @param path {@link Path} to be added to the list of inputs for * the map-reduce job. */ public static void addInputPath(Job job, Path path) throws IOException { Configuration conf = job.getConfiguration(); path = path.getFileSystem(conf).makeQualified(path); String dirStr = StringUtils.escapeString(path.toString()); String dirs = conf.get(INPUT_DIR); conf.set(INPUT_DIR, dirs == null ? dirStr : dirs + "," + dirStr); } // This method escapes commas in the glob pattern of the given paths. private static String[] getPathStrings(String commaSeparatedPaths) { int length = commaSeparatedPaths.length(); int curlyOpen = 0; int pathStart = 0; boolean globPattern = false; List<String> pathStrings = new ArrayList<String>(); for (int i = 0; i < length; i++) { char ch = commaSeparatedPaths.charAt(i); switch (ch) { case '{': { curlyOpen++; if (!globPattern) { globPattern = true; } break; } case '}': { curlyOpen--; if (curlyOpen == 0 && globPattern) { globPattern = false; } break; } case ',': { if (!globPattern) { pathStrings.add(commaSeparatedPaths.substring(pathStart, i)); pathStart = i + 1; } break; } default: continue; // nothing special to do for this character } } pathStrings.add(commaSeparatedPaths.substring(pathStart, length)); return pathStrings.toArray(new String[0]); } /** * Get the list of input {@link Path}s for the map-reduce job. * * @param context The job * @return the list of input {@link Path}s for the map-reduce job. */ public static Path[] getInputPaths(JobContext context) { String dirs = context.getConfiguration().get(INPUT_DIR, ""); String[] list = StringUtils.split(dirs); Path[] result = new Path[list.length]; for (int i = 0; i < list.length; i++) { result[i] = new Path(StringUtils.unEscapeString(list[i])); } return result; } }