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SharedMessageBuffer.java
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SharedMessageBuffer.java
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/**
* Copyright (c) 2011 Yahoo! Inc. 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. See accompanying LICENSE file.
*/
package com.yahoo.omid.replication;
import java.util.Set;
import java.util.TreeSet;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelFuture;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.Channels;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class SharedMessageBuffer {
private static final Logger LOG = LoggerFactory.getLogger(SharedMessageBuffer.class);
private static final int MAX_MESSAGE_SIZE = 30;
ReadersAwareBuffer pastBuffer = new ReadersAwareBuffer();
ReadersAwareBuffer currentBuffer = new ReadersAwareBuffer();
ChannelBuffer writeBuffer = currentBuffer.buffer;
BlockingQueue<ReadersAwareBuffer> bufferPool = new LinkedBlockingQueue<ReadersAwareBuffer>();
Zipper zipper = new Zipper();
Set<ReadingBuffer> readingBuffers = new TreeSet<SharedMessageBuffer.ReadingBuffer>();
public class ReadingBuffer implements Comparable<ReadingBuffer> {
private ChannelBuffer readBuffer;
private int readerIndex = 0;
private ReadersAwareBuffer readingBuffer;
private ChannelHandlerContext ctx;
private Channel channel;
private ReadingBuffer(ChannelHandlerContext ctx) {
this.channel = ctx.getChannel();
this.ctx = ctx;
}
public void initializeIndexes() {
this.readingBuffer = currentBuffer;
this.readBuffer = readingBuffer.buffer;
this.readerIndex = readBuffer.writerIndex();
}
/**
* Computes and returns the deltaSO for the associated client.
*
* This function registers some callbacks in the future passed for cleanup purposes, so the ChannelFuture object
* must be notified after the communication is finished.
*
* @param future
* It registers some callbacks on it
* @return the deltaSO for the associated client
*/
public ChannelBuffer flush(ChannelFuture future) {
int readable = readBuffer.readableBytes() - readerIndex;
if (readable == 0 && readingBuffer != pastBuffer) {
return ChannelBuffers.EMPTY_BUFFER;
}
ChannelBuffer deltaSO = readBuffer.slice(readerIndex, readable);
addFinishedWriteListener(future, readingBuffer);
readingBuffer.increaseReaders();
readerIndex += readable;
if (readingBuffer == pastBuffer) {
readingBuffer = currentBuffer;
readBuffer = readingBuffer.buffer;
readerIndex = 0;
readable = readBuffer.readableBytes();
deltaSO = readBuffer.slice(readerIndex, readable);
addFinishedWriteListener(future, readingBuffer);
readingBuffer.increaseReaders();
readerIndex += readable;
}
return deltaSO;
}
private void addFinishedWriteListener(ChannelFuture future, final ReadersAwareBuffer buffer) {
future.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
buffer.decreaseReaders();
if (buffer.isReadyForPool()) {
bufferPool.add(buffer);
}
}
});
}
public ZipperState getZipperState() {
return zipper.getZipperState();
}
@Override
public int compareTo(ReadingBuffer o) {
return this.channel.compareTo(o.channel);
}
@Override
public boolean equals(Object obj) {
if (!(obj instanceof ReadingBuffer))
return false;
ReadingBuffer buf = (ReadingBuffer) obj;
return this.channel.equals(buf.channel);
}
}
public ReadingBuffer getReadingBuffer(ChannelHandlerContext ctx) {
ReadingBuffer rb = new ReadingBuffer(ctx);
readingBuffers.add(rb);
return rb;
}
public void removeReadingBuffer(ChannelHandlerContext ctx) {
readingBuffers.remove(new ReadingBuffer(ctx));
}
public void writeCommit(long startTimestamp, long commitTimestamp) {
checkBufferSpace();
zipper.encodeCommit(writeBuffer, startTimestamp, commitTimestamp);
}
public void writeHalfAbort(long startTimestamp) {
checkBufferSpace();
zipper.encodeHalfAbort(writeBuffer, startTimestamp);
}
public void writeFullAbort(long startTimestamp) {
checkBufferSpace();
zipper.encodeFullAbort(writeBuffer, startTimestamp);
}
public void writeLargestIncrease(long largestTimestamp) {
checkBufferSpace();
zipper.encodeLargestIncrease(writeBuffer, largestTimestamp);
}
private void checkBufferSpace() {
if (writeBuffer.writableBytes() < MAX_MESSAGE_SIZE) {
nextBuffer();
}
}
private void nextBuffer() {
LOG.debug("Switching buffers");
// mark past buffer as scheduled for pool when all pending operations finish
pastBuffer.scheduleForPool();
for (final ReadingBuffer rb : readingBuffers) {
if (rb.readingBuffer == pastBuffer) {
ChannelFuture future = Channels.future(rb.channel);
ChannelBuffer cb = rb.flush(future);
Channels.write(rb.ctx, future, cb);
}
}
pastBuffer = currentBuffer;
currentBuffer = bufferPool.poll();
if (currentBuffer == null) {
currentBuffer = new ReadersAwareBuffer();
}
writeBuffer = currentBuffer.buffer;
}
}