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 org.apache.hadoop.mapred; import java.io.DataInputStream; import java.io.File; import java.io.IOException; import java.net.URL; import java.net.URLClassLoader; import java.util.ArrayList; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.security.UserGroupInformation; import org.apache.hadoop.util.DiskChecker.DiskErrorException; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.LocalDirAllocator; import org.apache.hadoop.fs.Path; import org.apache.hadoop.mapred.JvmTask; import org.apache.hadoop.mapreduce.split.JobSplit.TaskSplitIndex; /** * IsolationRunner is intended to facilitate debugging by re-running a specific * task, given left-over task files for a (typically failed) past job. * Currently, it is limited to re-running map tasks. * * Users may coerce MapReduce to keep task files around by setting * keep.failed.task.files. See mapred_tutorial.xml for more documentation. */ public class IsolationRunner { private static final Log LOG = LogFactory.getLog(IsolationRunner.class.getName()); private static class FakeUmbilical implements TaskUmbilicalProtocol { public long getProtocolVersion(String protocol, long clientVersion) { return TaskUmbilicalProtocol.versionID; } public void done(TaskAttemptID taskid, JvmContext jvmContext) throws IOException { LOG.info("Task " + taskid + " reporting done."); } public void fsError(TaskAttemptID taskId, String message, JvmContext jvmContext) throws IOException { LOG.info("Task " + taskId + " reporting file system error: " + message); } public void shuffleError(TaskAttemptID taskId, String message, JvmContext jvmContext) throws IOException { LOG.info("Task " + taskId + " reporting shuffle error: " + message); } public void fatalError(TaskAttemptID taskId, String msg, JvmContext jvmContext) throws IOException { LOG.info("Task " + taskId + " reporting fatal error: " + msg); } public JvmTask getTask(JvmContext context) throws IOException { return null; } public boolean ping(TaskAttemptID taskid, JvmContext jvmContext) throws IOException { return true; } public void commitPending(TaskAttemptID taskId, TaskStatus taskStatus, JvmContext jvmContext) throws IOException, InterruptedException { statusUpdate(taskId, taskStatus, jvmContext); } public boolean canCommit(TaskAttemptID taskid, JvmContext jvmContext) throws IOException { return true; } public boolean statusUpdate(TaskAttemptID taskId, TaskStatus taskStatus, JvmContext context) throws IOException, InterruptedException { StringBuffer buf = new StringBuffer("Task "); buf.append(taskId); buf.append(" making progress to "); buf.append(taskStatus.getProgress()); String state = taskStatus.getStateString(); if (state != null) { buf.append(" and state of "); buf.append(state); } LOG.info(buf.toString()); // ignore phase // ignore counters return true; } public void reportDiagnosticInfo(TaskAttemptID taskid, String trace, JvmContext jvmContext) throws IOException { LOG.info("Task " + taskid + " has problem " + trace); } public MapTaskCompletionEventsUpdate getMapCompletionEvents(JobID jobId, int fromEventId, int maxLocs, TaskAttemptID id, JvmContext jvmContext) throws IOException { return new MapTaskCompletionEventsUpdate(TaskCompletionEvent.EMPTY_ARRAY, false); } public void reportNextRecordRange(TaskAttemptID taskid, SortedRanges.Range range, JvmContext jvmContext) throws IOException { LOG.info("Task " + taskid + " reportedNextRecordRange " + range); } @Override public void updatePrivateDistributedCacheSizes(org.apache.hadoop.mapreduce.JobID jobId, long[] sizes) { // NOTHING } } private ClassLoader makeClassLoader(JobConf conf, File workDir) throws IOException { List<String> classPaths = new ArrayList<String>(); // Add jar clas files (includes lib/* and classes/*) String jar = conf.getJar(); if (jar != null) { TaskRunner.appendJobJarClasspaths(conf.getJar(), classPaths); } // Add the workdir, too. classPaths.add(workDir.toString()); // Note: TaskRunner.run() does more, including DistributedCache files. // Convert to URLs URL[] urls = new URL[classPaths.size()]; for (int i = 0; i < classPaths.size(); ++i) { urls[i] = new File(classPaths.get(i)).toURL(); } return new URLClassLoader(urls); } /** * Main method. */ boolean run(String[] args) throws ClassNotFoundException, IOException, InterruptedException { if (args.length < 1) { System.out.println("Usage: IsolationRunner <path>/job.xml " + "<optional-user-name>"); return false; } File jobFilename = new File(args[0]); if (!jobFilename.exists() || !jobFilename.isFile()) { System.out.println(jobFilename + " is not a valid job file."); return false; } String user; if (args.length > 1) { user = args[1]; } else { user = UserGroupInformation.getCurrentUser().getShortUserName(); } JobConf conf = new JobConf(new Path(jobFilename.toString())); conf.setUser(user); TaskAttemptID taskId = TaskAttemptID.forName(conf.get("mapred.task.id")); if (taskId == null) { System.out.println("mapred.task.id not found in configuration;" + " job.xml is not a task config"); } boolean isMap = conf.getBoolean("mapred.task.is.map", true); if (!isMap) { System.out.println("Only map tasks are supported."); return false; } int partition = conf.getInt("mapred.task.partition", 0); // setup the local and user working directories FileSystem local = FileSystem.getLocal(conf); LocalDirAllocator lDirAlloc = new LocalDirAllocator("mapred.local.dir"); Path workDirName; boolean workDirExists = lDirAlloc.ifExists(MRConstants.WORKDIR, conf); if (workDirExists) { workDirName = TaskRunner.formWorkDir(lDirAlloc, conf); } else { workDirName = lDirAlloc.getLocalPathForWrite(MRConstants.WORKDIR, conf); } local.setWorkingDirectory(new Path(workDirName.toString())); FileSystem.get(conf).setWorkingDirectory(conf.getWorkingDirectory()); // set up a classloader with the right classpath ClassLoader classLoader = makeClassLoader(conf, new File(workDirName.toString())); Thread.currentThread().setContextClassLoader(classLoader); conf.setClassLoader(classLoader); // split.dta file is used only by IsolationRunner. The file can now be in // any of the configured local disks, so use LocalDirAllocator to find out // where it is. Path localMetaSplit = new LocalDirAllocator("mapred.local.dir").getLocalPathToRead( TaskTracker.getLocalSplitFile(conf.getUser(), taskId.getJobID().toString(), taskId.toString()), conf); DataInputStream splitFile = FileSystem.getLocal(conf).open(localMetaSplit); TaskSplitIndex splitIndex = new TaskSplitIndex(); splitIndex.readFields(splitFile); splitFile.close(); Task task = new MapTask(jobFilename.toString(), taskId, partition, splitIndex, 1); task.setConf(conf); task.run(conf, new FakeUmbilical()); return true; } /** * Run a single task. * * @param args the first argument is the task directory */ public static void main(String[] args) throws ClassNotFoundException, IOException, InterruptedException { if (!new IsolationRunner().run(args)) { System.exit(1); } } }