/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package com.bigdata.concurrent;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
import org.apache.log4j.Logger;
/**
* This is a flyweight utility class to be used as a direct replacement for
* FutureTask in code where we may need to be able to discover the root cancel
* request causing an interrupt.
*
* @author Martyn Cutcher
*/
public class FutureTaskMon<T> extends FutureTask<T> {
static private final transient Logger log = Logger
.getLogger(FutureTaskMon.class);
private volatile boolean didStart = false;
public FutureTaskMon(final Callable<T> callable) {
super(callable);
}
public FutureTaskMon(final Runnable runnable, final T result) {
super(runnable, result);
}
/**
* {@inheritDoc}
* <p>
* Hooked to notice when the task has been started.
*/
@Override
public void run() {
didStart = true;
super.run();
}
/**
* {@inheritDoc}
* <p>
* Overridden to conditionally log @ DEBUG if the caller caused the task to
* be interrupted. This can be used to search for sources of interrupts.
*/
@Override
public boolean cancel(final boolean mayInterruptIfRunning) {
final boolean didStart = this.didStart;
final boolean ret = super.cancel(mayInterruptIfRunning);
if (didStart && mayInterruptIfRunning && ret && log.isDebugEnabled()) {
log.debug("May have interrupted running task",
new RuntimeException("Stack trace of cancel() invocation"));
}
return ret;
}
}