/*
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.striterator;
import java.nio.channels.ClosedByInterruptException;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.FutureTask;
import org.apache.log4j.Logger;
import com.bigdata.relation.accesspath.BlockingBuffer;
import com.bigdata.relation.accesspath.IAsynchronousIterator;
import com.bigdata.util.InnerCause;
import cutthecrap.utils.striterators.ICloseableIterator;
/**
* Wraps an {@link IChunkedIterator} and asynchronously resolves chunks.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
* @version $Id$
*
* @param <E>
* The generic type of the elements visited by the source iterator.
* @param <F>
* The generic type of the elements visited by this iterator (the
* resolved elements).
* @param <S>
* The generic type of the application state object.
*/
abstract public class AbstractChunkedResolverator<E,F,S> implements ICloseableIterator<F> {
final private static Logger log = Logger
.getLogger(AbstractChunkedResolverator.class);
// /**
// * True iff the {@link #log} level is DEBUG or less.
// */
// final protected static boolean DEBUG = log.isDebugEnabled();
/**
* The source iterator.
*/
private final IChunkedOrderedIterator<E> src;
/**
* Application specified state object.
*/
protected final S state;
/**
* The index of the last entry returned in the current {@link #chunk} and
* <code>-1</code> until the first entry is returned.
*/
private int lastIndex = -1;
/**
* The current chunk of resolved elements.
*/
private F[] chunk = null;
private volatile boolean open = true;
// /**
// * Total elapsed time for the iterator instance.
// */
// private long elapsed = 0L;
/**
*
* @param state
* Application specified state (optional).
* @param src
* The source iterator (will be closed or exhausted when this
* iterator is closed).
* @param buffer
* The {@link BlockingBuffer} on which the resolved chunks will
* be written by the {@link ChunkConsumerTask} and from which
* this iterator will read those chunks.
*/
public AbstractChunkedResolverator(final S state,
final IChunkedOrderedIterator<E> src,
final BlockingBuffer<F[]> buffer) {
if (src == null)
throw new IllegalArgumentException();
if (buffer == null)
throw new IllegalArgumentException();
this.state = state;
this.src = src;
this.buffer = buffer;
}
/**
* Creates and runs a task that will consume chunks from the source
* iterator, resolve the elements in each chunk, and place the resolved
* chunks onto the {@link BlockingBuffer}.
* <p>
* <strong>You MUST invoke this before consuming results from the iterator.</strong>
* <p>
* Implementations SHOULD strengthen the return type.
*
* @param service
* The service on which the task will be executed.
*/
// Note: Synchronized for atomic decision making and publication of [resolvedItr].
synchronized
public AbstractChunkedResolverator<E, F, S> start(final ExecutorService service) {
if (resolvedItr != null)
throw new IllegalStateException();
/*
* Create a task which reads chunks from the source iterator and writes
* resolved chunks on the buffer.
*/
final FutureTask<Long> ft = new FutureTask<Long>(
new ChunkConsumerTask());
/*
* Set the future for that task on the buffer.
*/
buffer.setFuture(ft);
/*
* This class will read resolved chunks from the [resolvedItr] and then
* hand out BigdataStatements from the current [chunk].
*/
resolvedItr = buffer.iterator();
// Submit the task for execution.
service.execute(ft);
// /*
// * Create and run a task which reads chunks from the source iterator and
// * writes resolved chunks on the buffer.
// */
// final Future<?> f = service.submit(new ChunkConsumerTask());
//
// /*
// * Set the future for that task on the buffer.
// */
// buffer.setFuture(f);
return this;
}
/**
* Buffer containing chunks of resolved elements.
*/
private final BlockingBuffer<F[]> buffer;
/**
* Iterator draining chunks of resolved elements from the {@link #buffer}.
* This is <code>null</code> until {@link #start(ExecutorService)} is
* invoked.
*/
private IAsynchronousIterator<F[]> resolvedItr;
/**
* Consumes chunks from the source iterator, placing the converted chunks on
* a queue.
*
* @author <a href="mailto:thompsonbry@users.sourceforge.net">Bryan Thompson</a>
*/
private class ChunkConsumerTask implements Callable<Long> {
public ChunkConsumerTask() {
}
/**
* @return The #of elements (not chunks) that were converted.
*
* @throws Exception
*/
@Override
public Long call() throws Exception {
try {
if (log.isDebugEnabled())
log.debug("Start");
final long begin = System.currentTimeMillis();
long nchunks = 0;
long nelements = 0;
// while buffer (aka sink) is open and source has more data.
while (buffer.isOpen() && src.hasNext()) {
// fetch the next chunk (already available).
final E[] chunk = src.nextChunk();
if (!buffer.isOpen()) {
/*
* Asynchronous close of the sink. By checking
* buffer.isOpen() here and in the while() clause, we
* will notice a closed sink more rapidly and close
* the source in a more timely manner.
*
* @see https://sourceforge.net/apps/trac/bigdata/ticket/361
*/
break;
}
final F[] converted;
try {
converted = resolveChunk(chunk);
} catch (Throwable t) {
/*
* If the root cause of the throwable was an interrupt,
* then close the buffer (aka the sink) and break out of
* the loop (we will not read anything more from the
* source).
*
* @see
* https://sourceforge.net/apps/trac/bigdata/ticket/460
*/
if (InnerCause.isInnerCause(t,
InterruptedException.class)
|| InnerCause.isInnerCause(t,
ClosedByInterruptException.class)) {
// buffer.abort(t);
buffer.close();
break;
}
throw new RuntimeException(t);
}
/**
* Note: This is no longer true. Some conversions can now
* expand or reduce the size of the chunk.
*
* @see <a href="http://trac.blazegraph.com/ticket/866" >
* Efficient batch remove of a collection of triple
* patterns </a>
*/
// assert converted.length == chunk.length;
// Note: Throws BufferClosedException if closed.
buffer.add(converted);
nchunks++;
nelements += chunk.length;
if (log.isDebugEnabled())
log.debug("nchunks=" + nchunks + ", chunkSize="
+ chunk.length);
}
final long elapsed = (System.currentTimeMillis() - begin);
if (log.isInfoEnabled())
log.info("Finished: nchunks=" + nchunks + ", nelements="
+ nelements + ", elapsed=" + elapsed
+ "ms, sink.open=" + buffer.isOpen());
return nelements;
} finally {
try {
src.close();
} finally {
/*
* Note: Close the buffer since nothing more will be written
* on it, but DO NOT close the iterator draining the buffer
* (aka [resolvedItr]) since the consumer will use that to
* drain the buffer.
*
* Note: Failure to close the buffer here will cause a
* severe performance penalty.
*
* Note: Closing the [resolvedItr] here will cause data to
* be lost.
*/
buffer.close();
}
}
}
}
/**
* Resolves the elements in a source chunk, returning a chunk of resolved
* elements.
* <p>
* Note: This method is invoked by the {@link ChunkConsumerTask} which runs
* asynchronously.
*
* @param chunk
* The next chunk from the source iterator.
*
* @return The resolved chunk.
*/
abstract protected F[] resolveChunk(final E[] chunk);
/**
* @throws IllegalStateException
* unless {@link #start(ExecutorService)} has been invoked.
*/
@Override
public boolean hasNext() {
if(open && _hasNext())
return true;
close();
return false;
}
private boolean _hasNext() {
if (resolvedItr == null) {
throw new IllegalStateException();
}
if (lastIndex != -1 && chunk != null && lastIndex + 1 < chunk.length) {
return true;
}
// read a resolved chunk from the buffer's async iterator.
return resolvedItr.hasNext();
}
@Override
public F next() {
// final long begin = System.currentTimeMillis();
if (!hasNext())
throw new NoSuchElementException();
if (lastIndex == -1 || chunk != null && lastIndex + 1 == chunk.length) {
// get the next chunk of resolved BigdataStatements.
chunk = resolvedItr.next();
// reset the index.
lastIndex = -1;
// final long now = System.currentTimeMillis();
// elapsed += (now - begin);
if (log.isDebugEnabled())
log.debug("nextChunk ready: size=" + chunk.length + ", chunk="
+ Arrays.toString(chunk));
}
// the next resolved element.
final F f = chunk[++lastIndex];
if (log.isDebugEnabled())
log.debug("lastIndex=" + lastIndex + ", chunk.length="
+ chunk.length + ", visting=" + f);
return f;
}
/**
* @throws UnsupportedOperationException
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public void close() {
if (open) {
open = false;
if (log.isInfoEnabled())
log.info("lastIndex=" + lastIndex + ", chunkSize="
+ (chunk != null ? "" + chunk.length : "N/A"));
/*
* Explicitly close the source since we will not be reading anything
* more from it.
*
* @see https://sourceforge.net/apps/trac/bigdata/ticket/361
*/
src.close();
/*
* Close the sink since nothing more will be written on it.
*/
buffer.close();
/*
* Since the outer iterator is being closed, nothing more will be
* read from the buffer so we also close the iterator draining the
* buffer.
*/
resolvedItr.close();
chunk = null;
}
}
}