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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// Licensed 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 com.google.devtools.build.lib.shell;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* <p>{@link KillableObserver} implementation which will kill its observed
* {@link Killable} if it is still being observed after a given amount
* of time has elapsed.</p>
*
* <p>Note that this class can only observe one {@link Killable} at a time;
* multiple instances should be used for concurrent calls to
* {@link Command#execute(byte[], KillableObserver, boolean)}.</p>
*/
public final class TimeoutKillableObserver implements KillableObserver {
private static final Logger log =
Logger.getLogger(TimeoutKillableObserver.class.getCanonicalName());
private final long timeoutMS;
private Killable killable;
private SleeperThread sleeperThread;
private boolean timedOut;
// TODO(bazel-team): I'd like to use ThreadPool2, but it doesn't currently
// provide a way to interrupt a thread
public TimeoutKillableObserver(final long timeoutMS) {
this.timeoutMS = timeoutMS;
}
/**
* Starts a new {@link Thread} to wait for the timeout period. This is
* interrupted by the {@link #stopObserving(Killable)} method.
*
* @param killable killable to kill when the timeout period expires
*/
@Override
public synchronized void startObserving(final Killable killable) {
this.timedOut = false;
this.killable = killable;
this.sleeperThread = new SleeperThread();
this.sleeperThread.start();
}
@Override
public synchronized void stopObserving(final Killable killable) {
if (!this.killable.equals(killable)) {
throw new IllegalStateException("start/stopObservering called with " +
"different Killables");
}
if (sleeperThread.isAlive()) {
sleeperThread.interrupt();
}
this.killable = null;
sleeperThread = null;
}
private final class SleeperThread extends Thread {
@Override public void run() {
try {
if (log.isLoggable(Level.FINE)) {
log.fine("Waiting for " + timeoutMS + "ms to kill process");
}
Thread.sleep(timeoutMS);
// timeout expired; kill it
synchronized (TimeoutKillableObserver.this) {
if (killable != null) {
log.fine("Killing process");
killable.kill();
timedOut = true;
}
}
} catch (InterruptedException ie) {
// continue -- process finished before timeout
log.fine("Wait interrupted since process finished; continuing...");
}
}
}
/**
* Returns true if the observed process was killed by this observer.
*/
public synchronized boolean hasTimedOut() {
// synchronized needed for memory model visibility.
return timedOut;
}
}
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