org.apache.commons.exec.ExecuteWatchdog Maven / Gradle / Ivy
/*
* 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.commons.exec;
import org.apache.commons.exec.util.DebugUtils;
/**
* Destroys a process running for too long. For example:
*
*
* ExecuteWatchdog watchdog = new ExecuteWatchdog(30000);
* Executer exec = new Executer(myloghandler, watchdog);
* exec.setCommandLine(mycmdline);
* int exitvalue = exec.execute();
* if (Execute.isFailure(exitvalue) && watchdog.killedProcess()) {
* // it was killed on purpose by the watchdog
* }
*
*
* When starting an asynchronous process than 'ExecuteWatchdog' is the
* keeper of the process handle. In some cases it is useful not to define
* a timeout (and pass 'INFINITE_TIMEOUT') and to kill the process explicitly
* using 'destroyProcess()'.
*
* Please note that ExecuteWatchdog is processed asynchronously, e.g. it might
* be still attached to a process even after the DefaultExecutor.execute
* has returned.
*
* @see org.apache.commons.exec.Executor
* @see org.apache.commons.exec.Watchdog
*/
public class ExecuteWatchdog implements TimeoutObserver {
/** The marker for an infinite timeout */
public static final long INFINITE_TIMEOUT = -1;
/** The process to execute and watch for duration. */
private Process process;
/** Is a user-supplied timeout in use */
private final boolean hasWatchdog;
/** Say whether or not the watchdog is currently monitoring a process. */
private boolean watch;
/** Exception that might be thrown during the process execution. */
private Exception caught;
/** Say whether or not the process was killed due to running overtime. */
private boolean killedProcess;
/** Will tell us whether timeout has occurred. */
private final Watchdog watchdog;
/**
* Creates a new watchdog with a given timeout.
*
* @param timeout
* the timeout for the process in milliseconds. It must be
* greater than 0 or 'INFINITE_TIMEOUT'
*/
public ExecuteWatchdog(final long timeout) {
this.killedProcess = false;
this.watch = false;
this.hasWatchdog = (timeout != INFINITE_TIMEOUT);
if(this.hasWatchdog) {
this.watchdog = new Watchdog(timeout);
this.watchdog.addTimeoutObserver(this);
}
else {
this.watchdog = null;
}
}
/**
* Watches the given process and terminates it, if it runs for too long. All
* information from the previous run are reset.
*
* @param process
* the process to monitor. It cannot be null
* @throws IllegalStateException
* if a process is still being monitored.
*/
public synchronized void start(final Process process) {
if (process == null) {
throw new NullPointerException("process is null.");
}
if (this.process != null) {
throw new IllegalStateException("Already running.");
}
this.caught = null;
this.killedProcess = false;
this.watch = true;
this.process = process;
if(this.hasWatchdog) {
watchdog.start();
}
}
/**
* Stops the watcher. It will notify all threads possibly waiting on this
* object.
*/
public synchronized void stop() {
if(hasWatchdog) {
watchdog.stop();
}
watch = false;
process = null;
}
/**
* Destroys the running process manually.
*/
public synchronized void destroyProcess() {
this.timeoutOccured(null);
this.stop();
}
/**
* Called after watchdog has finished.
*/
public synchronized void timeoutOccured(final Watchdog w) {
try {
try {
// We must check if the process was not stopped
// before being here
if(process != null) {
process.exitValue();
}
} catch (IllegalThreadStateException itse) {
// the process is not terminated, if this is really
// a timeout and not a manual stop then destroy it.
if (watch) {
killedProcess = true;
process.destroy();
}
}
} catch (Exception e) {
caught = e;
DebugUtils.handleException("Getting the exit value of the process failed", e);
} finally {
cleanUp();
}
}
/**
* This method will rethrow the exception that was possibly caught during
* the run of the process. It will only remains valid once the process has
* been terminated either by 'error', timeout or manual intervention.
* Information will be discarded once a new process is ran.
*
* @throws Exception
* a wrapped exception over the one that was silently swallowed
* and stored during the process run.
*/
public synchronized void checkException() throws Exception {
if (caught != null) {
throw caught;
}
}
/**
* Indicates whether or not the watchdog is still monitoring the process.
*
* @return true if the process is still running, otherwise
* false.
*/
public synchronized boolean isWatching() {
return watch;
}
/**
* Indicates whether the last process run was killed.
*
* @return true if the process was killed
* false.
*/
public synchronized boolean killedProcess() {
return killedProcess;
}
/**
* reset the monitor flag and the process.
*/
protected synchronized void cleanUp() {
watch = false;
process = null;
}
}