/**
* 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.util;
import java.io.IOException;
import java.util.Arrays;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.util.Shell.ExitCodeException;
import org.apache.hadoop.util.Shell.ShellCommandExecutor;
/**
* Process tree related operations
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class ProcessTree {
private static final Log LOG = LogFactory.getLog(ProcessTree.class);
public static final long DEFAULT_SLEEPTIME_BEFORE_SIGKILL = 5000L;
private static final int SIGQUIT = 3;
private static final int SIGTERM = 15;
private static final int SIGKILL = 9;
private static final String SIGQUIT_STR = "SIGQUIT";
private static final String SIGTERM_STR = "SIGTERM";
private static final String SIGKILL_STR = "SIGKILL";
public static final boolean isSetsidAvailable = isSetsidSupported();
private static boolean isSetsidSupported() {
ShellCommandExecutor shexec = null;
boolean setsidSupported = true;
try {
String[] args = {"setsid", "bash", "-c", "echo $$"};
shexec = new ShellCommandExecutor(args);
shexec.execute();
} catch (IOException ioe) {
LOG.warn("setsid is not available on this machine. So not using it.");
setsidSupported = false;
} finally { // handle the exit code
LOG.info("setsid exited with exit code " + shexec.getExitCode());
}
return setsidSupported;
}
/**
* Destroy the process-tree.
* @param pid process id of the root process of the subtree of processes
* to be killed
* @param sleeptimeBeforeSigkill The time to wait before sending SIGKILL
* after sending SIGTERM
* @param isProcessGroup pid is a process group leader or not
* @param inBackground Process is to be killed in the back ground with
* a separate thread
*/
public static void destroy(String pid, long sleeptimeBeforeSigkill,
boolean isProcessGroup, boolean inBackground) {
if(isProcessGroup) {
destroyProcessGroup(pid, sleeptimeBeforeSigkill, inBackground);
}
else {
//TODO: Destroy all the processes in the subtree in this case also.
// For the time being, killing only the root process.
destroyProcess(pid, sleeptimeBeforeSigkill, inBackground);
}
}
/** Destroy the process.
* @param pid Process id of to-be-killed-process
* @param sleeptimeBeforeSigkill The time to wait before sending SIGKILL
* after sending SIGTERM
* @param inBackground Process is to be killed in the back ground with
* a separate thread
*/
protected static void destroyProcess(String pid, long sleeptimeBeforeSigkill,
boolean inBackground) {
terminateProcess(pid);
sigKill(pid, false, sleeptimeBeforeSigkill, inBackground);
}
/** Destroy the process group.
* @param pgrpId Process group id of to-be-killed-processes
* @param sleeptimeBeforeSigkill The time to wait before sending SIGKILL
* after sending SIGTERM
* @param inBackground Process group is to be killed in the back ground with
* a separate thread
*/
protected static void destroyProcessGroup(String pgrpId,
long sleeptimeBeforeSigkill, boolean inBackground) {
terminateProcessGroup(pgrpId);
sigKill(pgrpId, true, sleeptimeBeforeSigkill, inBackground);
}
/**
* Send a specified signal to the specified pid
*
* @param pid the pid of the process [group] to signal.
* @param signalNum the signal to send.
* @param signalName the human-readable description of the signal
* (for logging).
*/
private static void sendSignal(String pid, int signalNum, String signalName) {
ShellCommandExecutor shexec = null;
try {
String[] args = { "kill", "-" + signalNum, pid };
shexec = new ShellCommandExecutor(args);
shexec.execute();
} catch (IOException ioe) {
LOG.warn("Error executing shell command " + ioe);
} finally {
if (pid.startsWith("-")) {
LOG.info("Sending signal to all members of process group " + pid
+ ": " + signalName + ". Exit code " + shexec.getExitCode());
} else {
LOG.info("Signaling process " + pid
+ " with " + signalName + ". Exit code " + shexec.getExitCode());
}
}
}
/**
* Send a specified signal to the process, if it is alive.
*
* @param pid the pid of the process to signal.
* @param signalNum the signal to send.
* @param signalName the human-readable description of the signal
* (for logging).
* @param alwaysSignal if true then send signal even if isAlive(pid) is false
*/
private static void maybeSignalProcess(String pid, int signalNum,
String signalName, boolean alwaysSignal) {
// If process tree is not alive then don't signal, unless alwaysSignal
// forces it so.
if (alwaysSignal || ProcessTree.isAlive(pid)) {
sendSignal(pid, signalNum, signalName);
}
}
private static void maybeSignalProcessGroup(String pgrpId, int signalNum,
String signalName, boolean alwaysSignal) {
if (alwaysSignal || ProcessTree.isProcessGroupAlive(pgrpId)) {
// signaling a process group means using a negative pid.
sendSignal("-" + pgrpId, signalNum, signalName);
}
}
/**
* Sends terminate signal to the process, allowing it to gracefully exit.
*
* @param pid pid of the process to be sent SIGTERM
*/
public static void terminateProcess(String pid) {
maybeSignalProcess(pid, SIGTERM, SIGTERM_STR, true);
}
/**
* Sends terminate signal to all the process belonging to the passed process
* group, allowing the group to gracefully exit.
*
* @param pgrpId process group id
*/
public static void terminateProcessGroup(String pgrpId) {
maybeSignalProcessGroup(pgrpId, SIGTERM, SIGTERM_STR, true);
}
/**
* Kills the process(OR process group) by sending the signal SIGKILL
* in the current thread
* @param pid Process id(OR process group id) of to-be-deleted-process
* @param isProcessGroup Is pid a process group id of to-be-deleted-processes
* @param sleepTimeBeforeSigKill wait time before sending SIGKILL after
* sending SIGTERM
*/
private static void sigKillInCurrentThread(String pid, boolean isProcessGroup,
long sleepTimeBeforeSigKill) {
// Kill the subprocesses of root process(even if the root process is not
// alive) if process group is to be killed.
if (isProcessGroup || ProcessTree.isAlive(pid)) {
try {
// Sleep for some time before sending SIGKILL
Thread.sleep(sleepTimeBeforeSigKill);
} catch (InterruptedException i) {
LOG.warn("Thread sleep is interrupted.");
}
if(isProcessGroup) {
killProcessGroup(pid);
} else {
killProcess(pid);
}
}
}
/** Kills the process(OR process group) by sending the signal SIGKILL
* @param pid Process id(OR process group id) of to-be-deleted-process
* @param isProcessGroup Is pid a process group id of to-be-deleted-processes
* @param sleeptimeBeforeSigkill The time to wait before sending SIGKILL
* after sending SIGTERM
* @param inBackground Process is to be killed in the back ground with
* a separate thread
*/
private static void sigKill(String pid, boolean isProcessGroup,
long sleeptimeBeforeSigkill, boolean inBackground) {
if(inBackground) { // use a separate thread for killing
SigKillThread sigKillThread = new SigKillThread(pid, isProcessGroup,
sleeptimeBeforeSigkill);
sigKillThread.setDaemon(true);
sigKillThread.start();
}
else {
sigKillInCurrentThread(pid, isProcessGroup, sleeptimeBeforeSigkill);
}
}
/**
* Sends kill signal to process, forcefully terminating the process.
*
* @param pid process id
*/
public static void killProcess(String pid) {
maybeSignalProcess(pid, SIGKILL, SIGKILL_STR, false);
}
/**
* Sends SIGQUIT to process; Java programs will dump their stack to
* stdout.
*
* @param pid process id
*/
public static void sigQuitProcess(String pid) {
maybeSignalProcess(pid, SIGQUIT, SIGQUIT_STR, false);
}
/**
* Sends kill signal to all process belonging to same process group,
* forcefully terminating the process group.
*
* @param pgrpId process group id
*/
public static void killProcessGroup(String pgrpId) {
maybeSignalProcessGroup(pgrpId, SIGKILL, SIGKILL_STR, false);
}
/**
* Sends SIGQUIT to all processes belonging to the same process group,
* ordering all processes in the group to send their stack dump to
* stdout.
*
* @param pgrpId process group id
*/
public static void sigQuitProcessGroup(String pgrpId) {
maybeSignalProcessGroup(pgrpId, SIGQUIT, SIGQUIT_STR, false);
}
/**
* Is the process with PID pid still alive?
* This method assumes that isAlive is called on a pid that was alive not
* too long ago, and hence assumes no chance of pid-wrapping-around.
*
* @param pid pid of the process to check.
* @return true if process is alive.
*/
public static boolean isAlive(String pid) {
ShellCommandExecutor shexec = null;
try {
String[] args = { "kill", "-0", pid };
shexec = new ShellCommandExecutor(args);
shexec.execute();
} catch (ExitCodeException ee) {
return false;
} catch (IOException ioe) {
LOG.warn("Error executing shell command "
+ Arrays.toString(shexec.getExecString()) + ioe);
return false;
}
return (shexec.getExitCode() == 0 ? true : false);
}
/**
* Is the process group with still alive?
*
* This method assumes that isAlive is called on a pid that was alive not
* too long ago, and hence assumes no chance of pid-wrapping-around.
*
* @param pgrpId process group id
* @return true if any of process in group is alive.
*/
public static boolean isProcessGroupAlive(String pgrpId) {
ShellCommandExecutor shexec = null;
try {
String[] args = { "kill", "-0", "-"+pgrpId };
shexec = new ShellCommandExecutor(args);
shexec.execute();
} catch (ExitCodeException ee) {
return false;
} catch (IOException ioe) {
LOG.warn("Error executing shell command "
+ Arrays.toString(shexec.getExecString()) + ioe);
return false;
}
return (shexec.getExitCode() == 0 ? true : false);
}
/**
* Helper thread class that kills process-tree with SIGKILL in background
*/
static class SigKillThread extends Thread {
private String pid = null;
private boolean isProcessGroup = false;
private long sleepTimeBeforeSigKill = DEFAULT_SLEEPTIME_BEFORE_SIGKILL;
private SigKillThread(String pid, boolean isProcessGroup, long interval) {
this.pid = pid;
this.isProcessGroup = isProcessGroup;
this.setName(this.getClass().getName() + "-" + pid);
sleepTimeBeforeSigKill = interval;
}
public void run() {
sigKillInCurrentThread(pid, isProcessGroup, sleepTimeBeforeSigKill);
}
}
}