Example #1
0
  // the method which actually copies the caches locally and unjars/unzips them
  // and does chmod for the files
  private static Path localizeCache(
      Configuration conf, URI cache, long confFileStamp, CacheStatus cacheStatus, boolean isArchive)
      throws IOException {
    FileSystem fs = getFileSystem(cache, conf);
    FileSystem localFs = FileSystem.getLocal(conf);
    Path parchive = null;

    if (isArchive) {
      parchive =
          new Path(
              cacheStatus.localizedLoadPath, new Path(cacheStatus.localizedLoadPath.getName()));
    } else {
      parchive = cacheStatus.localizedLoadPath;
    }
    if (!localFs.mkdirs(parchive.getParent())) {
      throw new IOException(
          "Mkdirs failed to create directory " + cacheStatus.localizedLoadPath.toString());
    }
    String cacheId = cache.getPath();

    fs.copyToLocalFile(new Path(cacheId), parchive);
    if (isArchive) {
      String tmpArchive = parchive.toString().toLowerCase();
      File srcFile = new File(parchive.toString());
      File destDir = new File(parchive.getParent().toString());
      if (tmpArchive.endsWith(".jar")) {
        RunJar.unJar(srcFile, destDir);
      } else if (tmpArchive.endsWith(".zip")) {
        FileUtil.unZip(srcFile, destDir);
      } else if (isTarFile(tmpArchive)) {
        FileUtil.unTar(srcFile, destDir);
      }
      // else will not do anyhting
      // and copy the file into the dir as it is
    }
    long cacheSize = FileUtil.getDU(new File(parchive.getParent().toString()));
    cacheStatus.size = cacheSize;
    addCacheInfoUpdate(cacheStatus);

    // do chmod here
    try {
      // Setting recursive permission to grant everyone read and execute
      Path localDir = new Path(cacheStatus.localizedBaseDir, cacheStatus.uniqueParentDir);
      LOG.info("Doing chmod on localdir :" + localDir);
      FileUtil.chmod(localDir.toString(), "ugo+rx", true);
    } catch (InterruptedException e) {
      LOG.warn("Exception in chmod" + e.toString());
    }

    // update cacheStatus to reflect the newly cached file
    cacheStatus.mtime = getTimestamp(conf, cache);
    return cacheStatus.localizedLoadPath;
  }
Example #2
0
  // Checks if the cache has already been localized and is fresh
  private static boolean ifExistsAndFresh(
      Configuration conf,
      FileSystem fs,
      URI cache,
      long confFileStamp,
      CacheStatus lcacheStatus,
      FileStatus fileStatus)
      throws IOException {
    // check for existence of the cache
    long dfsFileStamp;
    if (fileStatus != null) {
      dfsFileStamp = fileStatus.getModificationTime();
    } else {
      dfsFileStamp = getTimestamp(conf, cache);
    }

    // ensure that the file on hdfs hasn't been modified since the job started
    if (dfsFileStamp != confFileStamp) {
      LOG.fatal("File: " + cache + " has changed on HDFS since job started");
      throw new IOException("File: " + cache + " has changed on HDFS since job started");
    }

    if (dfsFileStamp != lcacheStatus.mtime) {
      // needs refreshing
      return false;
    }

    return true;
  }
Example #3
0
  // Mostly for setting up the symlinks. Note that when we setup the distributed
  // cache, we didn't create the symlinks. This is done on a per task basis
  // by the currently executing task.
  public static void setupWorkDir(JobConf conf) throws IOException {
    File workDir = new File(".").getAbsoluteFile();
    FileUtil.fullyDelete(workDir);
    if (DistributedCache.getSymlink(conf)) {
      URI[] archives = DistributedCache.getCacheArchives(conf);
      URI[] files = DistributedCache.getCacheFiles(conf);
      Path[] localArchives = DistributedCache.getLocalCacheArchives(conf);
      Path[] localFiles = DistributedCache.getLocalCacheFiles(conf);
      if (archives != null) {
        for (int i = 0; i < archives.length; i++) {
          String link = archives[i].getFragment();
          if (link != null) {
            link = workDir.toString() + Path.SEPARATOR + link;
            File flink = new File(link);
            if (!flink.exists()) {
              FileUtil.symLink(localArchives[i].toString(), link);
            }
          }
        }
      }
      if (files != null) {
        for (int i = 0; i < files.length; i++) {
          String link = files[i].getFragment();
          if (link != null) {
            link = workDir.toString() + Path.SEPARATOR + link;
            File flink = new File(link);
            if (!flink.exists()) {
              FileUtil.symLink(localFiles[i].toString(), link);
            }
          }
        }
      }
    }
    File jobCacheDir = null;
    if (conf.getJar() != null) {
      jobCacheDir = new File(new Path(conf.getJar()).getParent().toString());
    }

    // create symlinks for all the files in job cache dir in current
    // workingdir for streaming
    try {
      DistributedCache.createAllSymlink(conf, jobCacheDir, workDir);
    } catch (IOException ie) {
      // Do not exit even if symlinks have not been created.
      LOG.warn(StringUtils.stringifyException(ie));
    }
    // add java.io.tmpdir given by mapred.child.tmp
    String tmp = conf.get("mapred.child.tmp", "./tmp");
    Path tmpDir = new Path(tmp);

    // if temp directory path is not absolute
    // prepend it with workDir.
    if (!tmpDir.isAbsolute()) {
      tmpDir = new Path(workDir.toString(), tmp);
      FileSystem localFs = FileSystem.getLocal(conf);
      if (!localFs.mkdirs(tmpDir) && !localFs.getFileStatus(tmpDir).isDir()) {
        throw new IOException("Mkdirs failed to create " + tmpDir.toString());
      }
    }
  }
Example #4
0
 @Override
 public void run() {
   for (CacheStatus lcacheStatus : toBeDeletedCache) {
     synchronized (lcacheStatus) {
       Path fullUniqueParentDir =
           new Path(lcacheStatus.localizedBaseDir, lcacheStatus.uniqueParentDir);
       try {
         LOG.info("Deleting local cached path: " + fullUniqueParentDir.toString());
         deleteLocalPath(asyncDiskService, fs, fullUniqueParentDir);
         // decrement the size of the cache from baseDirSize
         deleteCacheInfoUpdate(lcacheStatus);
         LOG.info("Removed cache " + lcacheStatus.localizedLoadPath);
       } catch (IOException e) {
         LOG.warn("Error when deleting " + fullUniqueParentDir, e);
       }
     }
   }
 }
    /**
     * This method gets called everytime before any read/write to make sure that any change to
     * localDirs is reflected immediately.
     */
    private synchronized void confChanged(Configuration conf) throws IOException {
      String newLocalDirs = conf.get(contextCfgItemName);
      if (!newLocalDirs.equals(savedLocalDirs)) {
        String[] localDirs = conf.getStrings(contextCfgItemName);
        localFS = FileSystem.getLocal(conf);
        int numDirs = localDirs.length;
        ArrayList<String> dirs = new ArrayList<String>(numDirs);
        ArrayList<DF> dfList = new ArrayList<DF>(numDirs);
        for (int i = 0; i < numDirs; i++) {
          try {
            // filter problematic directories
            Path tmpDir = new Path(localDirs[i]);
            if (localFS.mkdirs(tmpDir) || localFS.exists(tmpDir)) {
              try {
                DiskChecker.checkDir(new File(localDirs[i]));
                dirs.add(localDirs[i]);
                dfList.add(new DF(new File(localDirs[i]), 30000));
              } catch (DiskErrorException de) {
                LOG.warn(localDirs[i] + "is not writable\n" + StringUtils.stringifyException(de));
              }
            } else {
              LOG.warn("Failed to create " + localDirs[i]);
            }
          } catch (IOException ie) {
            LOG.warn(
                "Failed to create "
                    + localDirs[i]
                    + ": "
                    + ie.getMessage()
                    + "\n"
                    + StringUtils.stringifyException(ie));
          } // ignore
        }
        localDirsPath = new Path[dirs.size()];
        for (int i = 0; i < localDirsPath.length; i++) {
          localDirsPath[i] = new Path(dirs.get(i));
        }
        dirDF = dfList.toArray(new DF[dirs.size()]);
        savedLocalDirs = newLocalDirs;

        // randomize the first disk picked in the round-robin selection
        dirNumLastAccessed = dirIndexRandomizer.nextInt(dirs.size());
      }
    }
Example #6
0
 /**
  * Delete a local path with asyncDiskService if available, or otherwise synchronously with local
  * file system.
  */
 private static void deleteLocalPath(
     MRAsyncDiskService asyncDiskService, LocalFileSystem fs, Path path) throws IOException {
   boolean deleted = false;
   if (asyncDiskService != null) {
     // Try to delete using asyncDiskService
     String localPathToDelete = path.toUri().getPath();
     deleted = asyncDiskService.moveAndDeleteAbsolutePath(localPathToDelete);
     if (!deleted) {
       LOG.warn(
           "Cannot find DistributedCache path "
               + localPathToDelete
               + " on any of the asyncDiskService volumes!");
     }
   }
   if (!deleted) {
     // If no asyncDiskService, we will delete the files synchronously
     fs.delete(path, true);
   }
   LOG.info("Deleted path " + path);
 }
Example #7
0
 /**
  * Clear the entire contents of the cache and delete the backing files. This should only be used
  * when the server is reinitializing, because the users are going to lose their files.
  */
 public static void purgeCache(Configuration conf, MRAsyncDiskService service) throws IOException {
   synchronized (cachedArchives) {
     LocalFileSystem localFs = FileSystem.getLocal(conf);
     for (Map.Entry<String, CacheStatus> f : cachedArchives.entrySet()) {
       try {
         deleteLocalPath(service, localFs, f.getValue().localizedLoadPath);
       } catch (IOException ie) {
         LOG.debug("Error cleaning up cache", ie);
       }
     }
     cachedArchives.clear();
   }
 }
Example #8
0
  /**
   * This is the opposite of getlocalcache. When you are done with using the cache, you need to
   * release the cache
   *
   * @param cache The cache URI to be released
   * @param conf configuration which contains the filesystem the cache is contained in.
   * @throws IOException
   */
  public static void releaseCache(URI cache, Configuration conf, long timeStamp)
      throws IOException {
    String cacheId = getKey(cache, conf, timeStamp);

    synchronized (cachedArchives) {
      CacheStatus lcacheStatus = cachedArchives.get(cacheId);
      if (lcacheStatus == null) {
        LOG.warn(
            "Cannot find localized cache: " + cache + " (key: " + cacheId + ") in releaseCache!");
        return;
      }
      lcacheStatus.refcount--;
    }
  }
    private Path createPath(Path path, boolean checkWrite) throws IOException {
      Path file = new Path(localDirsPath[dirNumLastAccessed], path);

      if (checkWrite) {
        // check whether we are able to create a directory here. If the disk
        // happens to be RDONLY we will fail
        try {
          DiskChecker.checkDir(new File(file.getParent().toUri().getPath()));
        } catch (DiskErrorException d) {
          LOG.warn(StringUtils.stringifyException(d));
          return null;
        }
      }
      return file;
    }
Example #10
0
 private static Path checkCacheStatusValidity(
     Configuration conf,
     URI cache,
     long confFileStamp,
     CacheStatus cacheStatus,
     FileStatus fileStatus,
     boolean isArchive)
     throws IOException {
   FileSystem fs = FileSystem.get(cache, conf);
   // Has to be
   if (!ifExistsAndFresh(conf, fs, cache, confFileStamp, cacheStatus, fileStatus)) {
     throw new IOException(
         "Stale cache file: " + cacheStatus.localizedLoadPath + " for cache-file: " + cache);
   }
   LOG.info(
       String.format(
           "Using existing cache of %s->%s", cache.toString(), cacheStatus.localizedLoadPath));
   return cacheStatus.localizedLoadPath;
 }
Example #11
0
  /**
   * Get the locally cached file or archive; it could either be previously cached (and valid) or
   * copy it from the {@link FileSystem} now.
   *
   * @param cache the cache to be localized, this should be specified as new
   *     URI(hdfs://hostname:port/absolute_path_to_file#LINKNAME). If no schema or hostname:port is
   *     provided the file is assumed to be in the filesystem being used in the Configuration
   * @param conf The Confguration file which contains the filesystem
   * @param subDir The sub cache Dir where you want to localize the files/archives
   * @param fileStatus The file status on the dfs.
   * @param isArchive if the cache is an archive or a file. In case it is an archive with a .zip or
   *     .jar or .tar or .tgz or .tar.gz extension it will be unzipped/unjarred/untarred
   *     automatically and the directory where the archive is unzipped/unjarred/untarred is returned
   *     as the Path. In case of a file, the path to the file is returned
   * @param confFileStamp this is the hdfs file modification timestamp to verify that the file to be
   *     cached hasn't changed since the job started
   * @param fileLength this is the length of the cache file
   * @param currentWorkDir this is the directory where you would want to create symlinks for the
   *     locally cached files/archives
   * @param honorSymLinkConf if this is false, then the symlinks are not created even if conf says
   *     so (this is required for an optimization in task launches
   * @param lDirAllocator LocalDirAllocator of the tracker
   * @return the path to directory where the archives are unjarred in case of archives, the path to
   *     the file where the file is copied locally
   * @throws IOException
   */
  private static Path getLocalCache(
      URI cache,
      Configuration conf,
      Path subDir,
      FileStatus fileStatus,
      boolean isArchive,
      long confFileStamp,
      long fileLength,
      Path currentWorkDir,
      boolean honorSymLinkConf,
      MRAsyncDiskService asyncDiskService,
      LocalDirAllocator lDirAllocator)
      throws IOException {
    String key = getKey(cache, conf, confFileStamp);

    CacheStatus lcacheStatus;
    Path localizedPath;
    synchronized (cachedArchives) {
      lcacheStatus = cachedArchives.get(key);
      if (lcacheStatus == null) {
        // was never localized
        Path uniqueParentDir = new Path(subDir, String.valueOf(random.nextLong()));
        String cachePath = new Path(uniqueParentDir, makeRelative(cache, conf)).toString();
        Path localPath = lDirAllocator.getLocalPathForWrite(cachePath, fileLength, conf);
        lcacheStatus =
            new CacheStatus(
                new Path(localPath.toString().replace(cachePath, "")), localPath, uniqueParentDir);
        cachedArchives.put(key, lcacheStatus);
      }
      lcacheStatus.refcount++;
    }
    boolean initSuccessful = false;
    try {
      synchronized (lcacheStatus) {
        if (!lcacheStatus.isInited()) {
          localizedPath = localizeCache(conf, cache, confFileStamp, lcacheStatus, isArchive);
          lcacheStatus.initComplete();
        } else {
          if (fileStatus != null) {
            localizedPath =
                checkCacheStatusValidity(
                    conf, cache, confFileStamp, lcacheStatus, fileStatus, isArchive);
          } else {
            // if fileStatus is null, then the md5 must be correct
            // so there is no need to check for cache validity
            localizedPath = lcacheStatus.localizedLoadPath;
          }
        }
        createSymlink(conf, cache, lcacheStatus, isArchive, currentWorkDir, honorSymLinkConf);
      }

      // try deleting stuff if you can
      long size = 0;
      int numberSubDir = 0;
      synchronized (lcacheStatus) {
        synchronized (baseDirSize) {
          Long get = baseDirSize.get(lcacheStatus.getBaseDir());
          if (get != null) {
            size = get.longValue();
          } else {
            LOG.warn("Cannot find size of baseDir: " + lcacheStatus.getBaseDir());
          }
        }
        synchronized (baseDirNumberSubDir) {
          Integer get = baseDirNumberSubDir.get(lcacheStatus.getBaseDir());
          if (get != null) {
            numberSubDir = get.intValue();
          } else {
            LOG.warn("Cannot find subdirectories limit of baseDir: " + lcacheStatus.getBaseDir());
          }
        }
      }
      // setting the cache size to a default of 10GB
      long allowedSize = conf.getLong("local.cache.size", DEFAULT_CACHE_SIZE);
      long allowedNumberSubDir =
          conf.getLong("local.cache.numbersubdir", DEFAULT_CACHE_SUBDIR_LIMIT);
      if (allowedSize < size || allowedNumberSubDir < numberSubDir) {
        // try some cache deletions
        LOG.debug(
            "Start deleting released cache because"
                + " [size, allowedSize, numberSubDir, allowedNumberSubDir] ="
                + " ["
                + size
                + ", "
                + allowedSize
                + ", "
                + numberSubDir
                + ", "
                + allowedNumberSubDir
                + "]");
        deleteCache(conf, asyncDiskService);
      }
      initSuccessful = true;
      return localizedPath;
    } finally {
      if (!initSuccessful) {
        synchronized (cachedArchives) {
          lcacheStatus.refcount--;
        }
      }
    }
  }
Example #12
0
  @Override
  public final void run() {
    try {

      // before preparing the job localize
      // all the archives
      TaskAttemptID taskid = t.getTaskID();
      LocalDirAllocator lDirAlloc = new LocalDirAllocator("mapred.local.dir");
      File jobCacheDir = null;
      if (conf.getJar() != null) {
        jobCacheDir = new File(new Path(conf.getJar()).getParent().toString());
      }
      File workDir =
          new File(
              lDirAlloc
                  .getLocalPathToRead(
                      TaskTracker.getJobCacheSubdir()
                          + Path.SEPARATOR
                          + t.getJobID()
                          + Path.SEPARATOR
                          + t.getTaskID()
                          + Path.SEPARATOR
                          + MRConstants.WORKDIR,
                      conf)
                  .toString());

      URI[] archives = DistributedCache.getCacheArchives(conf);
      URI[] files = DistributedCache.getCacheFiles(conf);
      FileStatus fileStatus;
      FileSystem fileSystem;
      Path localPath;
      String baseDir;

      if ((archives != null) || (files != null)) {
        if (archives != null) {
          String[] archivesTimestamps = DistributedCache.getArchiveTimestamps(conf);
          Path[] p = new Path[archives.length];
          for (int i = 0; i < archives.length; i++) {
            fileSystem = FileSystem.get(archives[i], conf);
            fileStatus = fileSystem.getFileStatus(new Path(archives[i].getPath()));
            String cacheId = DistributedCache.makeRelative(archives[i], conf);
            String cachePath = TaskTracker.getCacheSubdir() + Path.SEPARATOR + cacheId;
            if (lDirAlloc.ifExists(cachePath, conf)) {
              localPath = lDirAlloc.getLocalPathToRead(cachePath, conf);
            } else {
              localPath = lDirAlloc.getLocalPathForWrite(cachePath, fileStatus.getLen(), conf);
            }
            baseDir = localPath.toString().replace(cacheId, "");
            p[i] =
                DistributedCache.getLocalCache(
                    archives[i],
                    conf,
                    new Path(baseDir),
                    fileStatus,
                    true,
                    Long.parseLong(archivesTimestamps[i]),
                    new Path(workDir.getAbsolutePath()),
                    false);
          }
          DistributedCache.setLocalArchives(conf, stringifyPathArray(p));
        }
        if ((files != null)) {
          String[] fileTimestamps = DistributedCache.getFileTimestamps(conf);
          Path[] p = new Path[files.length];
          for (int i = 0; i < files.length; i++) {
            fileSystem = FileSystem.get(files[i], conf);
            fileStatus = fileSystem.getFileStatus(new Path(files[i].getPath()));
            String cacheId = DistributedCache.makeRelative(files[i], conf);
            String cachePath = TaskTracker.getCacheSubdir() + Path.SEPARATOR + cacheId;
            if (lDirAlloc.ifExists(cachePath, conf)) {
              localPath = lDirAlloc.getLocalPathToRead(cachePath, conf);
            } else {
              localPath = lDirAlloc.getLocalPathForWrite(cachePath, fileStatus.getLen(), conf);
            }
            baseDir = localPath.toString().replace(cacheId, "");
            p[i] =
                DistributedCache.getLocalCache(
                    files[i],
                    conf,
                    new Path(baseDir),
                    fileStatus,
                    false,
                    Long.parseLong(fileTimestamps[i]),
                    new Path(workDir.getAbsolutePath()),
                    false);
          }
          DistributedCache.setLocalFiles(conf, stringifyPathArray(p));
        }
        Path localTaskFile = new Path(t.getJobFile());
        FileSystem localFs = FileSystem.getLocal(conf);
        localFs.delete(localTaskFile, true);
        OutputStream out = localFs.create(localTaskFile);
        try {
          conf.writeXml(out);
        } finally {
          out.close();
        }
      }

      if (!prepare()) {
        return;
      }

      String sep = System.getProperty("path.separator");
      StringBuffer classPath = new StringBuffer();
      // start with same classpath as parent process
      classPath.append(System.getProperty("java.class.path"));
      classPath.append(sep);
      if (!workDir.mkdirs()) {
        if (!workDir.isDirectory()) {
          LOG.fatal("Mkdirs failed to create " + workDir.toString());
        }
      }

      String jar = conf.getJar();
      if (jar != null) {
        // if jar exists, it into workDir
        File[] libs = new File(jobCacheDir, "lib").listFiles();
        if (libs != null) {
          for (int i = 0; i < libs.length; i++) {
            classPath.append(sep); // add libs from jar to classpath
            classPath.append(libs[i]);
          }
        }
        classPath.append(sep);
        classPath.append(new File(jobCacheDir, "classes"));
        classPath.append(sep);
        classPath.append(jobCacheDir);
      }

      // include the user specified classpath

      // archive paths
      Path[] archiveClasspaths = DistributedCache.getArchiveClassPaths(conf);
      if (archiveClasspaths != null && archives != null) {
        Path[] localArchives = DistributedCache.getLocalCacheArchives(conf);
        if (localArchives != null) {
          for (int i = 0; i < archives.length; i++) {
            for (int j = 0; j < archiveClasspaths.length; j++) {
              if (archives[i].getPath().equals(archiveClasspaths[j].toString())) {
                classPath.append(sep);
                classPath.append(localArchives[i].toString());
              }
            }
          }
        }
      }
      // file paths
      Path[] fileClasspaths = DistributedCache.getFileClassPaths(conf);
      if (fileClasspaths != null && files != null) {
        Path[] localFiles = DistributedCache.getLocalCacheFiles(conf);
        if (localFiles != null) {
          for (int i = 0; i < files.length; i++) {
            for (int j = 0; j < fileClasspaths.length; j++) {
              if (files[i].getPath().equals(fileClasspaths[j].toString())) {
                classPath.append(sep);
                classPath.append(localFiles[i].toString());
              }
            }
          }
        }
      }

      classPath.append(sep);
      classPath.append(workDir);
      //  Build exec child jmv args.
      Vector<String> vargs = new Vector<String>(8);
      File jvm = // use same jvm as parent
          new File(new File(System.getProperty("java.home"), "bin"), "java");

      vargs.add(jvm.toString());

      // Add child (task) java-vm options.
      //
      // The following symbols if present in mapred.child.java.opts value are
      // replaced:
      // + @taskid@ is interpolated with value of TaskID.
      // Other occurrences of @ will not be altered.
      //
      // Example with multiple arguments and substitutions, showing
      // jvm GC logging, and start of a passwordless JVM JMX agent so can
      // connect with jconsole and the likes to watch child memory, threads
      // and get thread dumps.
      //
      //  <property>
      //    <name>mapred.child.java.opts</name>
      //    <value>-verbose:gc -Xloggc:/tmp/@[email protected] \
      //           -Dcom.sun.management.jmxremote.authenticate=false \
      //           -Dcom.sun.management.jmxremote.ssl=false \
      //    </value>
      //  </property>
      //
      String javaOpts = conf.get("mapred.child.java.opts", "-Xmx200m");
      javaOpts = javaOpts.replace("@taskid@", taskid.toString());
      String[] javaOptsSplit = javaOpts.split(" ");

      // Add java.library.path; necessary for loading native libraries.
      //
      // 1. To support native-hadoop library i.e. libhadoop.so, we add the
      //    parent processes' java.library.path to the child.
      // 2. We also add the 'cwd' of the task to it's java.library.path to help
      //    users distribute native libraries via the DistributedCache.
      // 3. The user can also specify extra paths to be added to the
      //    java.library.path via mapred.child.java.opts.
      //
      String libraryPath = System.getProperty("java.library.path");
      if (libraryPath == null) {
        libraryPath = workDir.getAbsolutePath();
      } else {
        libraryPath += sep + workDir;
      }
      boolean hasUserLDPath = false;
      for (int i = 0; i < javaOptsSplit.length; i++) {
        if (javaOptsSplit[i].startsWith("-Djava.library.path=")) {
          javaOptsSplit[i] += sep + libraryPath;
          hasUserLDPath = true;
          break;
        }
      }
      if (!hasUserLDPath) {
        vargs.add("-Djava.library.path=" + libraryPath);
      }
      for (int i = 0; i < javaOptsSplit.length; i++) {
        vargs.add(javaOptsSplit[i]);
      }

      // add java.io.tmpdir given by mapred.child.tmp
      String tmp = conf.get("mapred.child.tmp", "./tmp");
      Path tmpDir = new Path(tmp);

      // if temp directory path is not absolute
      // prepend it with workDir.
      if (!tmpDir.isAbsolute()) {
        tmpDir = new Path(workDir.toString(), tmp);
      }
      FileSystem localFs = FileSystem.getLocal(conf);
      if (!localFs.mkdirs(tmpDir) && !localFs.getFileStatus(tmpDir).isDir()) {
        throw new IOException("Mkdirs failed to create " + tmpDir.toString());
      }
      vargs.add("-Djava.io.tmpdir=" + tmpDir.toString());

      // Add classpath.
      vargs.add("-classpath");
      vargs.add(classPath.toString());

      // Setup the log4j prop
      long logSize = TaskLog.getTaskLogLength(conf);
      vargs.add(
          "-Dhadoop.log.dir=" + new File(System.getProperty("hadoop.log.dir")).getAbsolutePath());
      vargs.add("-Dhadoop.root.logger=INFO,TLA");
      vargs.add("-Dhadoop.tasklog.taskid=" + taskid);
      vargs.add("-Dhadoop.tasklog.totalLogFileSize=" + logSize);

      if (conf.getProfileEnabled()) {
        if (conf.getProfileTaskRange(t.isMapTask()).isIncluded(t.getPartition())) {
          File prof = TaskLog.getTaskLogFile(taskid, TaskLog.LogName.PROFILE);
          vargs.add(String.format(conf.getProfileParams(), prof.toString()));
        }
      }

      // Add main class and its arguments
      vargs.add(Child.class.getName()); // main of Child
      // pass umbilical address
      InetSocketAddress address = tracker.getTaskTrackerReportAddress();
      vargs.add(address.getAddress().getHostAddress());
      vargs.add(Integer.toString(address.getPort()));
      vargs.add(taskid.toString()); // pass task identifier

      String pidFile = null;
      if (tracker.isTaskMemoryManagerEnabled()) {
        pidFile =
            lDirAlloc
                .getLocalPathForWrite(
                    (TaskTracker.getPidFilesSubdir() + Path.SEPARATOR + taskid), this.conf)
                .toString();
      }

      // set memory limit using ulimit if feasible and necessary ...
      String[] ulimitCmd = Shell.getUlimitMemoryCommand(conf);
      List<String> setup = null;
      if (ulimitCmd != null) {
        setup = new ArrayList<String>();
        for (String arg : ulimitCmd) {
          setup.add(arg);
        }
      }

      // Set up the redirection of the task's stdout and stderr streams
      File stdout = TaskLog.getTaskLogFile(taskid, TaskLog.LogName.STDOUT);
      File stderr = TaskLog.getTaskLogFile(taskid, TaskLog.LogName.STDERR);
      stdout.getParentFile().mkdirs();
      tracker.getTaskTrackerInstrumentation().reportTaskLaunch(taskid, stdout, stderr);

      Map<String, String> env = new HashMap<String, String>();
      StringBuffer ldLibraryPath = new StringBuffer();
      ldLibraryPath.append(workDir.toString());
      String oldLdLibraryPath = null;
      oldLdLibraryPath = System.getenv("LD_LIBRARY_PATH");
      if (oldLdLibraryPath != null) {
        ldLibraryPath.append(sep);
        ldLibraryPath.append(oldLdLibraryPath);
      }
      env.put("LD_LIBRARY_PATH", ldLibraryPath.toString());
      jvmManager.launchJvm(
          this,
          jvmManager.constructJvmEnv(
              setup, vargs, stdout, stderr, logSize, workDir, env, pidFile, conf));
      synchronized (lock) {
        while (!done) {
          lock.wait();
        }
      }
      tracker.getTaskTrackerInstrumentation().reportTaskEnd(t.getTaskID());
      if (exitCodeSet) {
        if (!killed && exitCode != 0) {
          if (exitCode == 65) {
            tracker.getTaskTrackerInstrumentation().taskFailedPing(t.getTaskID());
          }
          throw new IOException("Task process exit with nonzero status of " + exitCode + ".");
        }
      }
    } catch (FSError e) {
      LOG.fatal("FSError", e);
      try {
        tracker.fsError(t.getTaskID(), e.getMessage());
      } catch (IOException ie) {
        LOG.fatal(t.getTaskID() + " reporting FSError", ie);
      }
    } catch (Throwable throwable) {
      LOG.warn(t.getTaskID() + " Child Error", throwable);
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      throwable.printStackTrace(new PrintStream(baos));
      try {
        tracker.reportDiagnosticInfo(t.getTaskID(), baos.toString());
      } catch (IOException e) {
        LOG.warn(t.getTaskID() + " Reporting Diagnostics", e);
      }
    } finally {
      try {
        URI[] archives = DistributedCache.getCacheArchives(conf);
        URI[] files = DistributedCache.getCacheFiles(conf);
        if (archives != null) {
          for (int i = 0; i < archives.length; i++) {
            DistributedCache.releaseCache(archives[i], conf);
          }
        }
        if (files != null) {
          for (int i = 0; i < files.length; i++) {
            DistributedCache.releaseCache(files[i], conf);
          }
        }
      } catch (IOException ie) {
        LOG.warn("Error releasing caches : Cache files might not have been cleaned up");
      }
      tracker.reportTaskFinished(t.getTaskID(), false);
      if (t.isMapTask()) {
        tracker.addFreeMapSlot();
      } else {
        tracker.addFreeReduceSlot();
      }
    }
  }