/**
* 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.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.PrintStream;
import java.net.InetSocketAddress;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.FSError;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.ipc.RPC;
import org.apache.hadoop.mapred.JvmTask;
import org.apache.hadoop.metrics.MetricsContext;
import org.apache.hadoop.metrics.MetricsUtil;
import org.apache.hadoop.metrics.jvm.JvmMetrics;
import org.apache.log4j.LogManager;
import org.apache.hadoop.util.StringUtils;
/**
* The main() for child processes.
*/
class Child {
public static final Log LOG =
LogFactory.getLog(TaskTracker.class);
static volatile TaskAttemptID taskid = null;
static volatile boolean isCleanup;
public static void main(String[] args) throws Throwable {
LOG.debug("Child starting");
JobConf defaultConf = new JobConf();
String host = args[0];
int port = Integer.parseInt(args[1]);
InetSocketAddress address = new InetSocketAddress(host, port);
final TaskAttemptID firstTaskid = TaskAttemptID.forName(args[2]);
final int SLEEP_LONGER_COUNT = 5;
int jvmIdInt = Integer.parseInt(args[3]);
JVMId jvmId = new JVMId(firstTaskid.getJobID(),firstTaskid.isMap(),jvmIdInt);
TaskUmbilicalProtocol umbilical =
(TaskUmbilicalProtocol)RPC.getProxy(TaskUmbilicalProtocol.class,
TaskUmbilicalProtocol.versionID,
address,
defaultConf);
int numTasksToExecute = -1; //-1 signifies "no limit"
int numTasksExecuted = 0;
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
try {
if (taskid != null) {
TaskLog.syncLogs(firstTaskid, taskid, isCleanup);
}
} catch (Throwable throwable) {
}
}
});
Thread t = new Thread() {
public void run() {
//every so often wake up and syncLogs so that we can track
//logs of the currently running task
while (true) {
try {
Thread.sleep(5000);
if (taskid != null) {
TaskLog.syncLogs(firstTaskid, taskid, isCleanup);
}
} catch (InterruptedException ie) {
} catch (IOException iee) {
LOG.error("Error in syncLogs: " + iee);
System.exit(-1);
}
}
}
};
t.setName("Thread for syncLogs");
t.setDaemon(true);
t.start();
//for the memory management, a PID file is written and the PID file
//is written once per JVM. We simply symlink the file on a per task
//basis later (see below). Long term, we should change the Memory
//manager to use JVMId instead of TaskAttemptId
Path srcPidPath = null;
Path dstPidPath = null;
int idleLoopCount = 0;
Task task = null;
try {
while (true) {
taskid = null;
JvmTask myTask = umbilical.getTask(jvmId);
if (myTask.shouldDie()) {
break;
} else {
if (myTask.getTask() == null) {
taskid = null;
if (++idleLoopCount >= SLEEP_LONGER_COUNT) {
//we sleep for a bigger interval when we don't receive
//tasks for a while
Thread.sleep(1500);
} else {
Thread.sleep(500);
}
continue;
}
}
idleLoopCount = 0;
task = myTask.getTask();
taskid = task.getTaskID();
isCleanup = task.isTaskCleanupTask();
// reset the statistics for the task
FileSystem.clearStatistics();
//create the index file so that the log files
//are viewable immediately
TaskLog.syncLogs(firstTaskid, taskid, isCleanup);
JobConf job = new JobConf(task.getJobFile());
if (job.getBoolean("task.memory.mgmt.enabled", false)) {
if (srcPidPath == null) {
srcPidPath = new Path(task.getPidFile());
}
//since the JVM is running multiple tasks potentially, we need
//to do symlink stuff only for the subsequent tasks
if (!taskid.equals(firstTaskid)) {
dstPidPath = new Path(task.getPidFile());
FileUtil.symLink(srcPidPath.toUri().getPath(),
dstPidPath.toUri().getPath());
}
}
//setupWorkDir actually sets up the symlinks for the distributed
//cache. After a task exits we wipe the workdir clean, and hence
//the symlinks have to be rebuilt.
TaskRunner.setupWorkDir(job);
numTasksToExecute = job.getNumTasksToExecutePerJvm();
assert(numTasksToExecute != 0);
TaskLog.cleanup(job.getInt("mapred.userlog.retain.hours", 24));
task.setConf(job);
defaultConf.addResource(new Path(task.getJobFile()));
// Initiate Java VM metrics
JvmMetrics.init(task.getPhase().toString(), job.getSessionId());
// use job-specified working directory
FileSystem.get(job).setWorkingDirectory(job.getWorkingDirectory());
try {
task.run(job, umbilical); // run the task
} finally {
TaskLog.syncLogs(firstTaskid, taskid, isCleanup);
if (!taskid.equals(firstTaskid) &&
job.getBoolean("task.memory.mgmt.enabled", false)) {
// delete the pid-file's symlink
new File(dstPidPath.toUri().getPath()).delete();
}
}
if (numTasksToExecute > 0 && ++numTasksExecuted == numTasksToExecute) {
break;
}
}
} catch (FSError e) {
LOG.fatal("FSError from child", e);
umbilical.fsError(taskid, e.getMessage());
} catch (Exception exception) {
LOG.warn("Error running child", exception);
try {
if (task != null) {
// do cleanup for the task
task.taskCleanup(umbilical);
}
} catch (Exception e) {
LOG.info("Error cleaning up" + e);
}
// Report back any failures, for diagnostic purposes
ByteArrayOutputStream baos = new ByteArrayOutputStream();
exception.printStackTrace(new PrintStream(baos));
if (taskid != null) {
umbilical.reportDiagnosticInfo(taskid, baos.toString());
}
} catch (Throwable throwable) {
LOG.fatal("Error running child : "
+ StringUtils.stringifyException(throwable));
if (taskid != null) {
Throwable tCause = throwable.getCause();
String cause = tCause == null
? throwable.getMessage()
: StringUtils.stringifyException(tCause);
umbilical.fatalError(taskid, cause);
}
} finally {
RPC.stopProxy(umbilical);
MetricsContext metricsContext = MetricsUtil.getContext("mapred");
metricsContext.close();
// Shutting down log4j of the child-vm...
// This assumes that on return from Task.run()
// there is no more logging done.
LogManager.shutdown();
}
}
}