ExecuteWatchdog.java
/*
* 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
*
* https://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 java.time.Duration;
import java.util.Objects;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.function.Supplier;
import org.apache.commons.exec.util.DebugUtils;
/**
* Destroys a process running for too long. For example:
*
* <pre>
* ExecuteWatchdog watchdog = ExecuteWatchdog.builder().setTimeout(Duration.ofSeconds(30)).get();
* Executor executor = DefaultExecutor.builder().setExecuteStreamHandler(new PumpStreamHandler()).get();
* executor.setWatchdog(watchdog);
* int exitValue = executor.execute(myCommandLine);
* if (executor.isFailure(exitValue) && watchdog.killedProcess()) {
* // it was killed on purpose by the watchdog
* }
* </pre>
* <p>
* 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 {@link #INFINITE_TIMEOUT_DURATION}) and to kill the process explicitly using {@link #destroyProcess()}.
* </p>
* <p>
* Please note that ExecuteWatchdog is processed asynchronously, e.g. it might be still attached to a process even after the
* {@link DefaultExecutor#execute(CommandLine)} or a variation has returned.
* </p>
*
* @see Executor
* @see Watchdog
*/
public class ExecuteWatchdog implements TimeoutObserver {
/**
* Builds ExecuteWatchdog instances.
*
* @since 1.4.0
*/
public static final class Builder implements Supplier<ExecuteWatchdog> {
/** Thread factory. */
private ThreadFactory threadFactory = Executors.defaultThreadFactory();
/** Timeout duration. */
private Duration timeout = INFINITE_TIMEOUT_DURATION;
/**
* Constructs a new instance.
*/
public Builder() {
// empty
}
/**
* Creates a new configured ExecuteWatchdog.
*
* @return a new configured ExecuteWatchdog.
*/
@Override
public ExecuteWatchdog get() {
return new ExecuteWatchdog(this);
}
/**
* Sets the thread factory.
*
* @param threadFactory the thread factory, null resets to the default {@link Executors#defaultThreadFactory()}.
* @return {@code this} instance.
*/
public Builder setThreadFactory(final ThreadFactory threadFactory) {
this.threadFactory = threadFactory != null ? threadFactory : Executors.defaultThreadFactory();
return this;
}
/**
* Sets the timeout duration.
*
* @param timeout the timeout duration, null resets to default {@link #INFINITE_TIMEOUT_DURATION}.
* @return {@code this} instance.
*/
public Builder setTimeout(final Duration timeout) {
this.timeout = timeout != null ? timeout : INFINITE_TIMEOUT_DURATION;
return this;
}
}
/** The marker for an infinite timeout. */
public static final long INFINITE_TIMEOUT = -1;
/** The marker for an infinite timeout. */
public static final Duration INFINITE_TIMEOUT_DURATION = Duration.ofMillis(INFINITE_TIMEOUT);
/**
* Creates a new builder.
*
* @return a new builder.
* @since 1.4.0
*/
public static Builder builder() {
return new Builder();
}
/** Exception that might be thrown during the process execution. */
private Exception caught;
/** Is a user-supplied timeout in use. */
private final boolean hasWatchdog;
/** Say whether the process was killed due to running overtime. */
private boolean killedProcess;
/** The process to execute and watch for duration. */
private Process process;
/** Indicates that the process is verified as started */
private volatile boolean processStarted;
/**
* The thread factory.
*/
private final ThreadFactory threadFactory;
/** Say whether the watchdog is currently monitoring a process. */
private boolean watch;
/** Will tell us whether timeout has occurred. */
private final Watchdog watchdog;
/**
* Creates a new watchdog with a given timeout.
*
* @param threadFactory the thread factory.
* @param timeout the timeout Duration for the process. It must be greater than 0 or {@code INFINITE_TIMEOUT_DURATION}.
*/
private ExecuteWatchdog(final Builder builder) {
this.killedProcess = false;
this.watch = false;
this.hasWatchdog = !INFINITE_TIMEOUT_DURATION.equals(builder.timeout);
this.processStarted = false;
this.threadFactory = builder.threadFactory;
if (this.hasWatchdog) {
this.watchdog = Watchdog.builder().setThreadFactory(threadFactory).setTimeout(builder.timeout).get();
this.watchdog.addTimeoutObserver(this);
} else {
this.watchdog = null;
}
}
/**
* Creates a new watchdog with a given timeout.
*
* @param timeoutMillis the timeout for the process in milliseconds. It must be greater than 0 or {@code INFINITE_TIMEOUT}.
* @deprecated Use {@link Builder#get()}.
*/
@Deprecated
public ExecuteWatchdog(final long timeoutMillis) {
this(builder().setTimeout(Duration.ofMillis(timeoutMillis)));
}
/**
* This method will rethrow the exception that was possibly caught during the run of the process. It will only remain valid once the process has been
* terminated either by 'error', timeout or manual intervention. Information will be discarded once a new process is run.
*
* @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;
}
}
/**
* Resets the monitor flag and the process.
*/
protected synchronized void cleanUp() {
watch = false;
process = null;
}
/**
* Destroys the running process manually.
*/
public synchronized void destroyProcess() {
ensureStarted();
timeoutOccured(null);
stop();
}
/**
* Ensures that the process is started or not already terminated so we do not race with asynch executionor hang forever. The caller of this method must be
* holding the lock on this.
*/
private void ensureStarted() {
while (!processStarted && caught == null) {
try {
wait();
} catch (final InterruptedException e) {
throw new IllegalStateException(e.getMessage(), e);
}
}
}
/**
* Notification that starting the process failed.
*
* @param e the offending exception.
*/
public synchronized void failedToStart(final Exception e) {
processStarted = true;
caught = e;
notifyAll();
}
/**
* Gets the watchdog.
*
* @return the watchdog.
*/
Watchdog getWatchdog() {
return watchdog;
}
/**
* Tests whether the watchdog is still monitoring the process.
*
* @return {@code true} if the process is still running, otherwise {@code false}.
*/
public synchronized boolean isWatching() {
ensureStarted();
return watch;
}
/**
* Tests whether the last process run was killed.
*
* @return {@code true} if the process was killed {@code false}.
*/
public synchronized boolean killedProcess() {
return killedProcess;
}
void setProcessNotStarted() {
processStarted = false;
}
/**
* Watches the given process and terminates it, if it runs for too long. All information from the previous run are reset.
*
* @param processToMonitor the process to monitor. It cannot be {@code null}.
* @throws IllegalStateException if a process is still being monitored.
*/
public synchronized void start(final Process processToMonitor) {
Objects.requireNonNull(processToMonitor, "processToMonitor");
if (process != null) {
throw new IllegalStateException("Already running.");
}
caught = null;
killedProcess = false;
watch = true;
process = processToMonitor;
processStarted = true;
notifyAll();
if (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;
}
/**
* Called after watchdog has finished.
*/
@Override
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 (final 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 (final Exception e) {
caught = e;
DebugUtils.handleException("Getting the exit value of the process failed", e);
} finally {
cleanUp();
}
}
}