/***********************************************************************************************************************
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* 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 eu.stratosphere.pact.runtime.iterative.io;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.LinkedBlockingQueue;
import eu.stratosphere.core.memory.MemorySegment;
import eu.stratosphere.nephele.services.iomanager.BlockChannelReader;
import eu.stratosphere.nephele.services.iomanager.BlockChannelWriter;
import eu.stratosphere.nephele.services.iomanager.Channel;
import eu.stratosphere.nephele.services.iomanager.IOManager;
import eu.stratosphere.nephele.services.memorymanager.AbstractPagedInputView;
import eu.stratosphere.nephele.services.memorymanager.AbstractPagedOutputView;
public class SerializedUpdateBuffer extends AbstractPagedOutputView {
private static final int HEADER_LENGTH = 4;
private static final float SPILL_THRESHOLD = 0.95f;
private final LinkedBlockingQueue<MemorySegment> emptyBuffers;
private ArrayDeque<MemorySegment> fullBuffers;
private BlockChannelWriter currentWriter;
private final IOManager ioManager;
private final Channel.Enumerator channelEnumerator;
private final int numSegmentsSpillingThreshold;
private int numBuffersSpilled;
private final int minBuffersForWriteEnd;
private final int minBuffersForSpilledReadEnd;
private final List<ReadEnd> readEnds;
private final int totalNumBuffers;
public SerializedUpdateBuffer() {
super(-1, HEADER_LENGTH);
emptyBuffers = null;
fullBuffers = null;
ioManager = null;
channelEnumerator = null;
numSegmentsSpillingThreshold = -1;
minBuffersForWriteEnd = -1;
minBuffersForSpilledReadEnd = -1;
totalNumBuffers = -1;
readEnds = Collections.emptyList();
}
public SerializedUpdateBuffer(List<MemorySegment> memSegments, int segmentSize, IOManager ioManager) {
super(memSegments.remove(memSegments.size() - 1), segmentSize, HEADER_LENGTH);
totalNumBuffers = memSegments.size() + 1;
if (totalNumBuffers < 3) {
throw new IllegalArgumentException("SerializedUpdateBuffer needs at least 3 memory segments.");
}
emptyBuffers = new LinkedBlockingQueue<MemorySegment>(totalNumBuffers);
fullBuffers = new ArrayDeque<MemorySegment>(64);
emptyBuffers.addAll(memSegments);
int threshold = (int) ((1 - SPILL_THRESHOLD) * totalNumBuffers);
numSegmentsSpillingThreshold = threshold > 0 ? threshold : 0;
minBuffersForWriteEnd = Math.max(2, Math.min(16, totalNumBuffers / 2));
minBuffersForSpilledReadEnd = Math.max(1, Math.min(16, totalNumBuffers / 4));
if (minBuffersForSpilledReadEnd + minBuffersForWriteEnd > totalNumBuffers) {
throw new IllegalArgumentException("BUG: Unfulfillable memory assignment.");
}
this.ioManager = ioManager;
channelEnumerator = ioManager.createChannelEnumerator();
readEnds = new ArrayList<ReadEnd>();
}
@Override
protected MemorySegment nextSegment(MemorySegment current, int positionInCurrent) throws IOException {
current.putInt(0, positionInCurrent);
// check if we keep the segment in memory, or if we spill it
if (emptyBuffers.size() > numSegmentsSpillingThreshold) {
// keep buffer in memory
fullBuffers.addLast(current);
} else {
// spill all buffers up to now
// check, whether we have a channel already
if (currentWriter == null) {
currentWriter = ioManager.createBlockChannelWriter(channelEnumerator.next(), emptyBuffers);
}
// spill all elements gathered up to now
numBuffersSpilled += fullBuffers.size();
while (fullBuffers.size() > 0) {
currentWriter.writeBlock(fullBuffers.removeFirst());
}
currentWriter.writeBlock(current);
numBuffersSpilled++;
}
try {
return emptyBuffers.take();
} catch (InterruptedException iex) {
throw new RuntimeException("Spilling Fifo Queue was interrupted while waiting for next buffer.");
}
}
public void flush() throws IOException {
advance();
}
public ReadEnd switchBuffers() throws IOException {
// remove exhausted read ends
for (int i = readEnds.size() - 1; i >= 0; --i) {
final ReadEnd re = readEnds.get(i);
if (re.disposeIfDone()) {
readEnds.remove(i);
}
}
// add the current memorySegment and reset this writer
final MemorySegment current = getCurrentSegment();
current.putInt(0, getCurrentPositionInSegment());
fullBuffers.addLast(current);
// create the reader
final ReadEnd readEnd;
if (numBuffersSpilled == 0 && emptyBuffers.size() >= minBuffersForWriteEnd) {
// read completely from in-memory segments
readEnd = new ReadEnd(fullBuffers.removeFirst(), emptyBuffers, fullBuffers, null, null, segmentSize, 0);
} else {
int toSpill = Math.min(minBuffersForSpilledReadEnd + minBuffersForWriteEnd - emptyBuffers.size(),
fullBuffers.size());
// reader reads also segments on disk
// grab some empty buffers to re-read the first segment
if (toSpill > 0) {
// need to spill to make a buffers available
if (currentWriter == null) {
currentWriter = ioManager.createBlockChannelWriter(channelEnumerator.next(), emptyBuffers);
}
for (int i = 0; i < toSpill; i++) {
currentWriter.writeBlock(fullBuffers.removeFirst());
}
numBuffersSpilled += toSpill;
}
// now close the writer and create the reader
currentWriter.close();
final BlockChannelReader reader = ioManager.createBlockChannelReader(currentWriter.getChannelID());
// gather some memory segments to circulate while reading back the data
final ArrayList<MemorySegment> readSegments = new ArrayList<MemorySegment>();
try {
while (readSegments.size() < minBuffersForSpilledReadEnd) {
readSegments.add(emptyBuffers.take());
}
// read the first segment
MemorySegment firstSeg = readSegments.remove(readSegments.size() - 1);
reader.readBlock(firstSeg);
firstSeg = reader.getReturnQueue().take();
// create the read end reading one less buffer, because the first buffer is already read back
readEnd = new ReadEnd(firstSeg, emptyBuffers, fullBuffers, reader, readSegments, segmentSize,
numBuffersSpilled - 1);
} catch (InterruptedException e) {
throw new RuntimeException(
"SerializedUpdateBuffer was interrupted while reclaiming memory by spilling.", e);
}
}
// reset the writer
fullBuffers = new ArrayDeque<MemorySegment>(64);
currentWriter = null;
numBuffersSpilled = 0;
try {
seekOutput(emptyBuffers.take(), HEADER_LENGTH);
} catch (InterruptedException e) {
throw new RuntimeException("SerializedUpdateBuffer was interrupted while reclaiming memory by spilling.", e);
}
// register this read end
readEnds.add(readEnd);
return readEnd;
}
public List<MemorySegment> close() {
if (currentWriter != null) {
try {
currentWriter.closeAndDelete();
} catch (Throwable t) {
}
}
ArrayList<MemorySegment> freeMem = new ArrayList<MemorySegment>(64);
// add all memory allocated to the write end
freeMem.add(getCurrentSegment());
clear();
freeMem.addAll(fullBuffers);
fullBuffers = null;
// add memory from non-exhausted read ends
try {
for (int i = readEnds.size() - 1; i >= 0; --i) {
final ReadEnd re = readEnds.remove(i);
re.forceDispose(freeMem);
}
// release all empty segments
while (freeMem.size() < totalNumBuffers) {
freeMem.add(emptyBuffers.take());
}
} catch (InterruptedException e) {
throw new RuntimeException("Retrieving memory back from asynchronous I/O was interrupted.", e);
}
return freeMem;
}
// ============================================================================================
private static final class ReadEnd extends AbstractPagedInputView {
private final LinkedBlockingQueue<MemorySegment> emptyBufferTarget;
private final ArrayDeque<MemorySegment> fullBufferSource;
private final BlockChannelReader spilledBufferSource;
private int spilledBuffersRemaining;
private int requestsRemaining;
private ReadEnd(MemorySegment firstMemSegment, LinkedBlockingQueue<MemorySegment> emptyBufferTarget,
ArrayDeque<MemorySegment> fullBufferSource, BlockChannelReader spilledBufferSource,
ArrayList<MemorySegment> emptyBuffers, int segmentSize, int numBuffersSpilled)
throws IOException {
super(firstMemSegment, firstMemSegment.getInt(0), HEADER_LENGTH);
this.emptyBufferTarget = emptyBufferTarget;
this.fullBufferSource = fullBufferSource;
this.spilledBufferSource = spilledBufferSource;
requestsRemaining = numBuffersSpilled;
this.spilledBuffersRemaining = numBuffersSpilled;
// send the first requests
while (requestsRemaining > 0 && emptyBuffers.size() > 0) {
this.spilledBufferSource.readBlock(emptyBuffers.remove(emptyBuffers.size() - 1));
requestsRemaining--;
}
}
@Override
protected MemorySegment nextSegment(MemorySegment current) throws IOException {
// use the buffer to send the next request
if (requestsRemaining > 0) {
requestsRemaining--;
spilledBufferSource.readBlock(current);
} else {
emptyBufferTarget.add(current);
}
// get the next buffer either from the return queue, or the full buffer source
if (spilledBuffersRemaining > 0) {
spilledBuffersRemaining--;
try {
return spilledBufferSource.getReturnQueue().take();
} catch (InterruptedException e) {
throw new RuntimeException("Read End was interrupted while waiting for spilled buffer.", e);
}
} else if (fullBufferSource.size() > 0) {
return fullBufferSource.removeFirst();
} else {
clear();
// delete the channel, if we had one
if (spilledBufferSource != null) {
spilledBufferSource.closeAndDelete();
}
throw new EOFException();
}
}
@Override
protected int getLimitForSegment(MemorySegment segment) {
return segment.getInt(0);
}
private boolean disposeIfDone() {
if (fullBufferSource.isEmpty() && spilledBuffersRemaining == 0) {
if (getCurrentSegment() == null || getCurrentPositionInSegment() >= getCurrentSegmentLimit()) {
if (getCurrentSegment() != null) {
emptyBufferTarget.add(getCurrentSegment());
clear();
}
if (spilledBufferSource != null) {
try {
spilledBufferSource.closeAndDelete();
} catch (Throwable t) {
}
}
return true;
}
}
return false;
}
private void forceDispose(List<MemorySegment> freeMemTarget) throws InterruptedException {
// add the current segment
final MemorySegment current = getCurrentSegment();
clear();
if (current != null) {
freeMemTarget.add(current);
}
// add all remaining memory
freeMemTarget.addAll(fullBufferSource);
// add the segments with the requests issued but not returned
for (int i = spilledBuffersRemaining - requestsRemaining; i > 0; --i) {
freeMemTarget.add(emptyBufferTarget.take());
}
if (spilledBufferSource != null) {
try {
spilledBufferSource.closeAndDelete();
} catch (Throwable t) {
}
}
}
}
}