org.apache.hadoop.mapreduce.filecache.DistributedCache Maven / Gradle / Ivy
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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.mapreduce.filecache;
import java.io.*;
import java.util.*;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.util.*;
import org.apache.hadoop.fs.*;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.MRJobConfig;
import java.net.URI;
/**
* Distribute application-specific large, read-only files efficiently.
*
* DistributedCache is a facility provided by the Map-Reduce
* framework to cache files (text, archives, jars etc.) needed by applications.
*
*
* Applications specify the files, via urls (hdfs:// or http://) to be cached
* via the {@link org.apache.hadoop.mapred.JobConf}. The
* DistributedCache assumes that the files specified via urls are
* already present on the {@link FileSystem} at the path specified by the url
* and are accessible by every machine in the cluster.
*
* The framework will copy the necessary files on to the slave node before
* any tasks for the job are executed on that node. Its efficiency stems from
* the fact that the files are only copied once per job and the ability to
* cache archives which are un-archived on the slaves.
*
* DistributedCache can be used to distribute simple, read-only
* data/text files and/or more complex types such as archives, jars etc.
* Archives (zip, tar and tgz/tar.gz files) are un-archived at the slave nodes.
* Jars may be optionally added to the classpath of the tasks, a rudimentary
* software distribution mechanism. Files have execution permissions.
* In older version of Hadoop Map/Reduce users could optionally ask for symlinks
* to be created in the working directory of the child task. In the current
* version symlinks are always created. If the URL does not have a fragment
* the name of the file or directory will be used. If multiple files or
* directories map to the same link name, the last one added, will be used. All
* others will not even be downloaded.
*
* DistributedCache tracks modification timestamps of the cache
* files. Clearly the cache files should not be modified by the application
* or externally while the job is executing.
*
* Here is an illustrative example on how to use the
* DistributedCache:
*
* // Setting up the cache for the application
*
* 1. Copy the requisite files to the FileSystem:
*
* $ bin/hadoop fs -copyFromLocal lookup.dat /myapp/lookup.dat
* $ bin/hadoop fs -copyFromLocal map.zip /myapp/map.zip
* $ bin/hadoop fs -copyFromLocal mylib.jar /myapp/mylib.jar
* $ bin/hadoop fs -copyFromLocal mytar.tar /myapp/mytar.tar
* $ bin/hadoop fs -copyFromLocal mytgz.tgz /myapp/mytgz.tgz
* $ bin/hadoop fs -copyFromLocal mytargz.tar.gz /myapp/mytargz.tar.gz
*
* 2. Setup the application's JobConf:
*
* JobConf job = new JobConf();
* DistributedCache.addCacheFile(new URI("/myapp/lookup.dat#lookup.dat"),
* job);
* DistributedCache.addCacheArchive(new URI("/myapp/map.zip", job);
* DistributedCache.addFileToClassPath(new Path("/myapp/mylib.jar"), job);
* DistributedCache.addCacheArchive(new URI("/myapp/mytar.tar", job);
* DistributedCache.addCacheArchive(new URI("/myapp/mytgz.tgz", job);
* DistributedCache.addCacheArchive(new URI("/myapp/mytargz.tar.gz", job);
*
* 3. Use the cached files in the {@link org.apache.hadoop.mapred.Mapper}
* or {@link org.apache.hadoop.mapred.Reducer}:
*
* public static class MapClass extends MapReduceBase
* implements Mapper<K, V, K, V> {
*
* private Path[] localArchives;
* private Path[] localFiles;
*
* public void configure(JobConf job) {
* // Get the cached archives/files
* File f = new File("./map.zip/some/file/in/zip.txt");
* }
*
* public void map(K key, V value,
* OutputCollector<K, V> output, Reporter reporter)
* throws IOException {
* // Use data from the cached archives/files here
* // ...
* // ...
* output.collect(k, v);
* }
* }
*
*
*
* It is also very common to use the DistributedCache by using
* {@link org.apache.hadoop.util.GenericOptionsParser}.
*
* This class includes methods that should be used by users
* (specifically those mentioned in the example above, as well
* as {@link DistributedCache#addArchiveToClassPath(Path, Configuration)}),
* as well as methods intended for use by the MapReduce framework
* (e.g., {@link org.apache.hadoop.mapred.JobClient}).
*
* @see org.apache.hadoop.mapred.JobConf
* @see org.apache.hadoop.mapred.JobClient
*/
@Deprecated
@InterfaceAudience.Private
public class DistributedCache {
/**
* Set the configuration with the given set of archives. Intended
* to be used by user code.
* @param archives The list of archives that need to be localized
* @param conf Configuration which will be changed
* @deprecated Use {@link Job#setCacheArchives(URI[])} instead
*/
@Deprecated
public static void setCacheArchives(URI[] archives, Configuration conf) {
String sarchives = StringUtils.uriToString(archives);
conf.set(MRJobConfig.CACHE_ARCHIVES, sarchives);
}
/**
* Set the configuration with the given set of files. Intended to be
* used by user code.
* @param files The list of files that need to be localized
* @param conf Configuration which will be changed
* @deprecated Use {@link Job#setCacheFiles(URI[])} instead
*/
@Deprecated
public static void setCacheFiles(URI[] files, Configuration conf) {
String sfiles = StringUtils.uriToString(files);
conf.set(MRJobConfig.CACHE_FILES, sfiles);
}
/**
* Get cache archives set in the Configuration. Used by
* internal DistributedCache and MapReduce code.
* @param conf The configuration which contains the archives
* @return A URI array of the caches set in the Configuration
* @throws IOException
* @deprecated Use {@link JobContext#getCacheArchives()} instead
*/
@Deprecated
public static URI[] getCacheArchives(Configuration conf) throws IOException {
return StringUtils.stringToURI(conf.getStrings(MRJobConfig.CACHE_ARCHIVES));
}
/**
* Get cache files set in the Configuration. Used by internal
* DistributedCache and MapReduce code.
* @param conf The configuration which contains the files
* @return A URI array of the files set in the Configuration
* @throws IOException
* @deprecated Use {@link JobContext#getCacheFiles()} instead
*/
@Deprecated
public static URI[] getCacheFiles(Configuration conf) throws IOException {
return StringUtils.stringToURI(conf.getStrings(MRJobConfig.CACHE_FILES));
}
/**
* Return the path array of the localized caches. Intended to be used
* by user code.
* @param conf Configuration that contains the localized archives
* @return A path array of localized caches
* @throws IOException
* @deprecated Use {@link JobContext#getLocalCacheArchives()} instead
*/
@Deprecated
public static Path[] getLocalCacheArchives(Configuration conf)
throws IOException {
return StringUtils.stringToPath(conf
.getStrings(MRJobConfig.CACHE_LOCALARCHIVES));
}
/**
* Return the path array of the localized files. Intended to be used
* by user code.
* @param conf Configuration that contains the localized files
* @return A path array of localized files
* @throws IOException
* @deprecated Use {@link JobContext#getLocalCacheFiles()} instead
*/
@Deprecated
public static Path[] getLocalCacheFiles(Configuration conf)
throws IOException {
return StringUtils.stringToPath(conf.getStrings(MRJobConfig.CACHE_LOCALFILES));
}
/**
* Get the timestamps of the archives. Used by internal
* DistributedCache and MapReduce code.
* @param conf The configuration which stored the timestamps
* @return a string array of timestamps
* @throws IOException
* @deprecated Use {@link JobContext#getArchiveTimestamps()} instead
*/
@Deprecated
public static String[] getArchiveTimestamps(Configuration conf) {
return conf.getStrings(MRJobConfig.CACHE_ARCHIVES_TIMESTAMPS);
}
/**
* Get the timestamps of the files. Used by internal
* DistributedCache and MapReduce code.
* @param conf The configuration which stored the timestamps
* @return a string array of timestamps
* @throws IOException
* @deprecated Use {@link JobContext#getFileTimestamps()} instead
*/
@Deprecated
public static String[] getFileTimestamps(Configuration conf) {
return conf.getStrings(MRJobConfig.CACHE_FILE_TIMESTAMPS);
}
/**
* Add a archives to be localized to the conf. Intended to
* be used by user code.
* @param uri The uri of the cache to be localized
* @param conf Configuration to add the cache to
* @deprecated Use {@link Job#addCacheArchive(URI)} instead
*/
@Deprecated
public static void addCacheArchive(URI uri, Configuration conf) {
String archives = conf.get(MRJobConfig.CACHE_ARCHIVES);
conf.set(MRJobConfig.CACHE_ARCHIVES, archives == null ? uri.toString()
: archives + "," + uri.toString());
}
/**
* Add a file to be localized to the conf. Intended
* to be used by user code.
* @param uri The uri of the cache to be localized
* @param conf Configuration to add the cache to
* @deprecated Use {@link Job#addCacheFile(URI)} instead
*/
@Deprecated
public static void addCacheFile(URI uri, Configuration conf) {
String files = conf.get(MRJobConfig.CACHE_FILES);
conf.set(MRJobConfig.CACHE_FILES, files == null ? uri.toString() : files + ","
+ uri.toString());
}
/**
* Add an file path to the current set of classpath entries It adds the file
* to cache as well. Intended to be used by user code.
*
* @param file Path of the file to be added
* @param conf Configuration that contains the classpath setting
* @deprecated Use {@link Job#addFileToClassPath(Path)} instead
*/
@Deprecated
public static void addFileToClassPath(Path file, Configuration conf)
throws IOException {
addFileToClassPath(file, conf, file.getFileSystem(conf));
}
/**
* Add a file path to the current set of classpath entries. It adds the file
* to cache as well. Intended to be used by user code.
*
* @param file Path of the file to be added
* @param conf Configuration that contains the classpath setting
* @param fs FileSystem with respect to which {@code archivefile} should
* be interpreted.
*/
public static void addFileToClassPath
(Path file, Configuration conf, FileSystem fs)
throws IOException {
String classpath = conf.get(MRJobConfig.CLASSPATH_FILES);
conf.set(MRJobConfig.CLASSPATH_FILES, classpath == null ? file.toString()
: classpath + "," + file.toString());
URI uri = fs.makeQualified(file).toUri();
addCacheFile(uri, conf);
}
/**
* Get the file entries in classpath as an array of Path.
* Used by internal DistributedCache code.
*
* @param conf Configuration that contains the classpath setting
* @deprecated Use {@link JobContext#getFileClassPaths()} instead
*/
@Deprecated
public static Path[] getFileClassPaths(Configuration conf) {
ArrayList list = (ArrayList)conf.getStringCollection(
MRJobConfig.CLASSPATH_FILES);
if (list.size() == 0) {
return null;
}
Path[] paths = new Path[list.size()];
for (int i = 0; i < list.size(); i++) {
paths[i] = new Path(list.get(i));
}
return paths;
}
/**
* Add an archive path to the current set of classpath entries. It adds the
* archive to cache as well. Intended to be used by user code.
*
* @param archive Path of the archive to be added
* @param conf Configuration that contains the classpath setting
* @deprecated Use {@link Job#addArchiveToClassPath(Path)} instead
*/
@Deprecated
public static void addArchiveToClassPath(Path archive, Configuration conf)
throws IOException {
addArchiveToClassPath(archive, conf, archive.getFileSystem(conf));
}
/**
* Add an archive path to the current set of classpath entries. It adds the
* archive to cache as well. Intended to be used by user code.
*
* @param archive Path of the archive to be added
* @param conf Configuration that contains the classpath setting
* @param fs FileSystem with respect to which {@code archive} should be interpreted.
*/
public static void addArchiveToClassPath
(Path archive, Configuration conf, FileSystem fs)
throws IOException {
String classpath = conf.get(MRJobConfig.CLASSPATH_ARCHIVES);
conf.set(MRJobConfig.CLASSPATH_ARCHIVES, classpath == null ? archive
.toString() : classpath + "," + archive.toString());
URI uri = fs.makeQualified(archive).toUri();
addCacheArchive(uri, conf);
}
/**
* Get the archive entries in classpath as an array of Path.
* Used by internal DistributedCache code.
*
* @param conf Configuration that contains the classpath setting
* @deprecated Use {@link JobContext#getArchiveClassPaths()} instead
*/
@Deprecated
public static Path[] getArchiveClassPaths(Configuration conf) {
ArrayList list = (ArrayList)conf.getStringCollection(
MRJobConfig.CLASSPATH_ARCHIVES);
if (list.size() == 0) {
return null;
}
Path[] paths = new Path[list.size()];
for (int i = 0; i < list.size(); i++) {
paths[i] = new Path(list.get(i));
}
return paths;
}
/**
* Originally intended to enable symlinks, but currently symlinks cannot be
* disabled. This is a NO-OP.
* @param conf the jobconf
* @deprecated This is a NO-OP.
*/
@Deprecated
public static void createSymlink(Configuration conf){
//NOOP
}
/**
* Originally intended to check if symlinks should be used, but currently
* symlinks cannot be disabled.
* @param conf the jobconf
* @return true
* @deprecated symlinks are always created.
*/
@Deprecated
public static boolean getSymlink(Configuration conf){
return true;
}
private static boolean[] parseBooleans(String[] strs) {
if (null == strs) {
return null;
}
boolean[] result = new boolean[strs.length];
for(int i=0; i < strs.length; ++i) {
result[i] = Boolean.parseBoolean(strs[i]);
}
return result;
}
/**
* Get the booleans on whether the files are public or not. Used by
* internal DistributedCache and MapReduce code.
* @param conf The configuration which stored the timestamps
* @return a string array of booleans
* @throws IOException
*/
public static boolean[] getFileVisibilities(Configuration conf) {
return parseBooleans(conf.getStrings(MRJobConfig.CACHE_FILE_VISIBILITIES));
}
/**
* Get the booleans on whether the archives are public or not. Used by
* internal DistributedCache and MapReduce code.
* @param conf The configuration which stored the timestamps
* @return a string array of booleans
*/
public static boolean[] getArchiveVisibilities(Configuration conf) {
return parseBooleans(conf.getStrings(MRJobConfig.CACHE_ARCHIVES_VISIBILITIES));
}
/**
* This method checks if there is a conflict in the fragment names
* of the uris. Also makes sure that each uri has a fragment. It
* is only to be called if you want to create symlinks for
* the various archives and files. May be used by user code.
* @param uriFiles The uri array of urifiles
* @param uriArchives the uri array of uri archives
*/
public static boolean checkURIs(URI[] uriFiles, URI[] uriArchives) {
if ((uriFiles == null) && (uriArchives == null)) {
return true;
}
// check if fragment is null for any uri
// also check if there are any conflicts in fragment names
Set fragments = new HashSet();
// iterate over file uris
if (uriFiles != null) {
for (int i = 0; i < uriFiles.length; i++) {
String fragment = uriFiles[i].getFragment();
if (fragment == null) {
return false;
}
String lowerCaseFragment = fragment.toLowerCase();
if (fragments.contains(lowerCaseFragment)) {
return false;
}
fragments.add(lowerCaseFragment);
}
}
// iterate over archive uris
if (uriArchives != null) {
for (int i = 0; i < uriArchives.length; i++) {
String fragment = uriArchives[i].getFragment();
if (fragment == null) {
return false;
}
String lowerCaseFragment = fragment.toLowerCase();
if (fragments.contains(lowerCaseFragment)) {
return false;
}
fragments.add(lowerCaseFragment);
}
}
return true;
}
}