/*
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
*/
/*
* Created on Apr 15, 2009
*/
package com.bigdata.util.concurrent;
import java.nio.channels.ClosedByInterruptException;
import java.util.concurrent.CancellationException;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.atomic.AtomicReference;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import com.bigdata.relation.accesspath.BufferClosedException;
import com.bigdata.util.InnerCause;
/**
* Abstract base class for tasks whose processing may be halted asynchronously.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*/
public abstract class AbstractHaltableProcess {
protected final transient static Logger log = Logger
.getLogger(AbstractHaltableProcess.class);
/**
* Volatile flag is set <code>true</code> if the process should halt.
*/
volatile transient private boolean halt = false;
/**
* The first cause as set by {@link #halt(Throwable)}.
* <p>
* Note: {@link #halt} uses
* {@link AtomicReference#compareAndSet(Object, Object)} and specifies
* <code>null</code> as the expected value to ensure that only the first
* cause is recorded by this field.
*/
final transient private AtomicReference<Throwable> firstCause = new AtomicReference<Throwable>(
null);
/**
* Return unless processing has been halted.
*
* @throws RuntimeException
* wrapping the {@link #firstCause} iff processing has been
* halted.
*
* @see #halt(Throwable)
*/
final public void halted() {
if (halt) {
throw new RuntimeException(firstCause.get());
}
}
/**
* Indicate that processing should halt. This method is written defensively
* and will not throw anything.
*
* <strong>The caller is responsible for throwing the cause out of their own
* context.</strong>
*
* @param cause
* The cause.
*
* @return The argument.
*/
final public <T extends Throwable> T halt(final T cause) {
halt = true;
final boolean isFirstCause = firstCause.compareAndSet(
null/* expect */, cause);
if (log.isEnabledFor(Level.WARN))
try {
if (!InnerCause.isInnerCause(cause, InterruptedException.class)
&& !InnerCause.isInnerCause(cause,
CancellationException.class)
&& !InnerCause.isInnerCause(cause,
ClosedByInterruptException.class)
&& !InnerCause.isInnerCause(cause,
RejectedExecutionException.class)
&& !InnerCause.isInnerCause(cause,
BufferClosedException.class)) {
/*
* This logs all unexpected causes, not just the first one
* to be reported for this join task.
*
* Note: The master will log the firstCause that it receives
* as an error.
*/
log.warn(this + " : isFirstCause=" + isFirstCause + " : "
+ cause, cause);
}
} catch (Throwable ex) {
// error in logging system - ignore.
}
return cause;
}
}