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自从前段时间的一个事故让队列里缓存的大量关键数据丢失后，一直琢磨着弄一个能持久化到本地文件的队列，这样即使系统再次发生意外，我也不至于再苦逼的修数据了。选定使用mappedbytebuffer来实现，但做出来的原型不够理想。《高性能队列Fqueue的设计和使用实践》这篇文章给了我莫大的帮助。 当然只是借鉴了大致的文件系统结构，绝大部分还是按自己的想法来的。
上图就是队列的文件系统，index文件记录了队列当前的读写文件号，读写位置和读写计数。队列的size是通过读写计数writeCounter-readCounter的方式记录的，这样做的好处是可以做到读写分离。运行时size用一个AtomicInteger变量记录，系统初始化加载队列时才用到读写计数差。block文件记录了实际的入队数据，每个block必须要有足够的空间写入4(len)+data.length+4(EOF)长度的数据，否则写入一个EOF标记，换一个新的block开始写入数据，而当读取到这个EOF时，表示这个block读取完毕，载入下一个block，如果有的话，释放并准备删除当前block。现在规定的block大小32MB，按我的使用场景，每个block可以写入100W数据（PS：protostuff-runtime挺不错的，我用它做的序列化）。
最后附上代码：
public class MFQueuePool {
private static final Logger LOGGER = LoggerFactory.getLogger(MFQueuePool.class);
private static final BlockingQueue<String> DELETING_QUEUE = new LinkedBlockingQueue<>();
private static MFQueuePool instance = null;
private String fileBackupPath;
private Map<String, MFQueue> fQueueMap;
private ScheduledExecutorService syncService;
private MFQueuePool(String fileBackupPath) {
this.fileBackupPath = fileBackupPath;
File fileBackupDir = new File(fileBackupPath);
if (!fileBackupDir.exists() && !fileBackupDir.mkdir()) {
throw new IllegalArgumentException("can not create directory");
}
this.fQueueMap = scanDir(fileBackupDir);
this.syncService = Executors.newSingleThreadScheduledExecutor();
this.syncService.scheduleWithFixedDelay(new Runnable() {
@Override
public void run() {
for (MFQueue MFQueue : fQueueMap.values()) {
MFQueue.sync();
}
deleteBlockFile();
}
}, 10L, 10L, TimeUnit.SECONDS);
}
private void deleteBlockFile() {
String blockFilePath = DELETING_QUEUE.poll();
if (StringUtils.isNotBlank(blockFilePath)) {
File delFile = new File(blockFilePath);
try {
if (!delFile.delete()) {
LOGGER.warn("block file:{} delete failed", blockFilePath);
}
} catch (SecurityException e) {
LOGGER.error("security manager exists, delete denied");
}
}
}
private static void toClear(String filePath) {
DELETING_QUEUE.add(filePath);
}
private Map<String, MFQueue> scanDir(File fileBackupDir) {
if (!fileBackupDir.isDirectory()) {
throw new IllegalArgumentException("it is not a directory");
}
Map<String, MFQueue> exitsFQueues = new HashMap<>();
File[] indexFiles = fileBackupDir.listFiles(new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return MFQueueIndex.isIndexFile(name);
}
});
if (ArrayUtils.isNotEmpty(indexFiles)) {
for (File indexFile : indexFiles) {
String queueName = MFQueueIndex.parseQueueName(indexFile.getName());
exitsFQueues.put(queueName, new MFQueue(queueName, fileBackupPath));
}
}
return exitsFQueues;
}
public synchronized static void init(String deployPath) {
if (instance == null) {
instance = new MFQueuePool(deployPath);
}
}
private void disposal() {
this.syncService.shutdown();
for (MFQueue MFQueue : fQueueMap.values()) {
MFQueue.close();
}
while (!DELETING_QUEUE.isEmpty()) {
deleteBlockFile();
}
}
public synchronized static void destory() {
if (instance != null) {
instance.disposal();
instance = null;
}
}
private MFQueue getQueueFromPool(String queueName) {
if (fQueueMap.containsKey(queueName)) {
return fQueueMap.get(queueName);
}
MFQueue MFQueue = new MFQueue(queueName, fileBackupPath);
fQueueMap.put(queueName, MFQueue);
return MFQueue;
}
public synchronized static MFQueue getFQueue(String queueName) {
if (StringUtils.isBlank(queueName)) {
throw new IllegalArgumentException("empty queue name");
}
return instance.getQueueFromPool(queueName);
}
public static class MFQueue extends AbstractQueue<byte[]> {
private String queueName;
private String fileBackupDir;
private MFQueueIndex index;
private MFQueueBlock readBlock;
private MFQueueBlock writeBlock;
private ReentrantLock readLock;
private ReentrantLock writeLock;
private AtomicInteger size;
public MFQueue(String queueName, String fileBackupDir) {
this.queueName = queueName;
this.fileBackupDir = fileBackupDir;
this.readLock = new ReentrantLock();
this.writeLock = new ReentrantLock();
this.index = new MFQueueIndex(MFQueueIndex.formatIndexFilePath(queueName, fileBackupDir));
this.size = new AtomicInteger(index.getWriteCounter() - index.getReadCounter());
this.writeBlock = new MFQueueBlock(index, MFQueueBlock.formatBlockFilePath(queueName,
index.getWriteNum(), fileBackupDir));
if (index.getReadNum() == index.getWriteNum()) {
this.readBlock = this.writeBlock.duplicate();
} else {
this.readBlock = new MFQueueBlock(index, MFQueueBlock.formatBlockFilePath(queueName,
index.getReadNum(), fileBackupDir));
}
}
@Override
public Iterator<byte[]> iterator() {
throw new UnsupportedOperationException();
}
@Override
public int size() {
return this.size.get();
}
private void rotateNextWriteBlock() {
int nextWriteBlockNum = index.getWriteNum() + 1;
nextWriteBlockNum = (nextWriteBlockNum < 0) ? 0 : nextWriteBlockNum;
writeBlock.putEOF();
if (index.getReadNum() == index.getWriteNum()) {
writeBlock.sync();
} else {
writeBlock.close();
}
writeBlock = new MFQueueBlock(index, MFQueueBlock.formatBlockFilePath(queueName,
nextWriteBlockNum, fileBackupDir));
index.putWriteNum(nextWriteBlockNum);
index.putWritePosition(0);
}
@Override
public boolean offer(byte[] bytes) {
if (ArrayUtils.isEmpty(bytes)) {
return true;
}
writeLock.lock();
try {
if (!writeBlock.isSpaceAvailable(bytes.length)) {
rotateNextWriteBlock();
}
writeBlock.write(bytes);
size.incrementAndGet();
return true;
} finally {
writeLock.unlock();
}
}
private void rotateNextReadBlock() {
if (index.getReadNum() == index.getWriteNum()) {
// 读缓存块的滑动必须发生在写缓存块滑动之后
return;
}
int nextReadBlockNum = index.getReadNum() + 1;
nextReadBlockNum = (nextReadBlockNum < 0) ? 0 : nextReadBlockNum;
readBlock.close();
String blockPath = readBlock.getBlockFilePath();
if (nextReadBlockNum == index.getWriteNum()) {
readBlock = writeBlock.duplicate();
} else {
readBlock = new MFQueueBlock(index, MFQueueBlock.formatBlockFilePath(queueName,
nextReadBlockNum, fileBackupDir));
}
index.putReadNum(nextReadBlockNum);
index.putReadPosition(0);
MFQueuePool.toClear(blockPath);
}
@Override
public byte[] poll() {
readLock.lock();
try {
if (readBlock.eof()) {
rotateNextReadBlock();
}
byte[] bytes = readBlock.read();
if (bytes != null) {
size.decrementAndGet();
}
return bytes;
} finally {
readLock.unlock();
}
}
@Override
public byte[] peek() {
throw new UnsupportedOperationException();
}
public void sync() {
index.sync();
// read block只读，不用同步
writeBlock.sync();
}
public void close() {
writeBlock.close();
if (index.getReadNum() != index.getWriteNum()) {
readBlock.close();
}
index.reset();
index.close();
}
}
@SuppressWarnings("UnusedDeclaration")
private static class MFQueueIndex {
private static final String MAGIC = "v.1.0000";
private static final String INDEX_FILE_SUFFIX = ".idx";
private static final int INDEX_SIZE = 32;
private static final int READ_NUM_OFFSET = 8;
private static final int READ_POS_OFFSET = 12;
private static final int READ_CNT_OFFSET = 16;
private static final int WRITE_NUM_OFFSET = 20;
private static final int WRITE_POS_OFFSET = 24;
private static final int WRITE_CNT_OFFSET = 28;
private int p11, p12, p13, p14, p15, p16, p17, p18; // 缓存行填充 32B
private volatile int readPosition; // 12 读索引位置
private volatile int readNum; // 8 读索引文件号
private volatile int readCounter; // 16 总读取数量
private int p21, p22, p23, p24, p25, p26, p27, p28; // 缓存行填充 32B
private volatile int writePosition; // 24 写索引位置
private volatile int writeNum; // 20 写索引文件号
private volatile int writeCounter; // 28 总写入数量
private int p31, p32, p33, p34, p35, p36, p37, p38; // 缓存行填充 32B
private RandomAccessFile indexFile;
private FileChannel fileChannel;
// 读写分离
private MappedByteBuffer writeIndex;
private MappedByteBuffer readIndex;
public MFQueueIndex(String indexFilePath) {
File file = new File(indexFilePath);
try {
if (file.exists()) {
this.indexFile = new RandomAccessFile(file, "rw");
byte[] bytes = new byte[8];
this.indexFile.read(bytes, 0, 8);
if (!MAGIC.equals(new String(bytes))) {
throw new IllegalArgumentException("version mismatch");
}
this.readNum = indexFile.readInt();
this.readPosition = indexFile.readInt();
this.readCounter = indexFile.readInt();
this.writeNum = indexFile.readInt();
this.writePosition = indexFile.readInt();
this.writeCounter = indexFile.readInt();
this.fileChannel = indexFile.getChannel();
this.writeIndex = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, INDEX_SIZE);
this.writeIndex = writeIndex.load();
this.readIndex = (MappedByteBuffer) writeIndex.duplicate();
} else {
this.indexFile = new RandomAccessFile(file, "rw");
this.fileChannel = indexFile.getChannel();
this.writeIndex = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, INDEX_SIZE);
this.readIndex = (MappedByteBuffer) writeIndex.duplicate();
putMagic();
putReadNum(0);
putReadPosition(0);
putReadCounter(0);
putWriteNum(0);
putWritePosition(0);
putWriteCounter(0);
}
} catch (Exception e) {
throw new IllegalArgumentException(e);
}
}
public static boolean isIndexFile(String fileName) {
return fileName.endsWith(INDEX_FILE_SUFFIX);
}
public static String parseQueueName(String indexFileName) {
String fileName = indexFileName.substring(0, indexFileName.lastIndexOf(‘.‘));
return fileName.split("_")[1];
}
public static String formatIndexFilePath(String queueName, String fileBackupDir) {
return fileBackupDir + File.separator + String.format("findex_%s%s", queueName, INDEX_FILE_SUFFIX);
}
public int getReadNum() {
return this.readNum;
}
public int getReadPosition() {
return this.readPosition;
}
public int getReadCounter() {
return this.readCounter;
}
public int getWriteNum() {
return this.writeNum;
}
public int getWritePosition() {
return this.writePosition;
}
public int getWriteCounter() {
return this.writeCounter;
}
public void putMagic() {
this.writeIndex.position(0);
this.writeIndex.put(MAGIC.getBytes());
}
public void putWritePosition(int writePosition) {
this.writeIndex.position(WRITE_POS_OFFSET);
this.writeIndex.putInt(writePosition);
this.writePosition = writePosition;
}
public void putWriteNum(int writeNum) {
this.writeIndex.position(WRITE_NUM_OFFSET);
this.writeIndex.putInt(writeNum);
this.writeNum = writeNum;
}
public void putWriteCounter(int writeCounter) {
this.writeIndex.position(WRITE_CNT_OFFSET);
this.writeIndex.putInt(writeCounter);
this.writeCounter = writeCounter;
}
public void putReadNum(int readNum) {
this.readIndex.position(READ_NUM_OFFSET);
this.readIndex.putInt(readNum);
this.readNum = readNum;
}
public void putReadPosition(int readPosition) {
this.readIndex.position(READ_POS_OFFSET);
this.readIndex.putInt(readPosition);
this.readPosition = readPosition;
}
public void putReadCounter(int readCounter) {
this.readIndex.position(READ_CNT_OFFSET);
this.readIndex.putInt(readCounter);
this.readCounter = readCounter;
}
public void reset() {
int size = writeCounter - readCounter;
putReadCounter(0);
putWriteCounter(size);
if (size == 0 && readNum == writeNum) {
putReadPosition(0);
putWritePosition(0);
}
}
public void sync() {
if (writeIndex != null) {
writeIndex.force();
}
}
public void close() {
try {
if (writeIndex == null) {
return;
}
sync();
AccessController.doPrivileged(new PrivilegedAction<Object>() {
public Object run() {
try {
Method getCleanerMethod = writeIndex.getClass().getMethod("cleaner");
getCleanerMethod.setAccessible(true);
sun.misc.Cleaner cleaner = (sun.misc.Cleaner) getCleanerMethod.invoke(writeIndex);
cleaner.clean();
} catch (Exception e) {
LOGGER.error("close fqueue index file failed", e);
}
return null;
}
});
writeIndex = null;
readIndex = null;
fileChannel.close();
indexFile.close();
} catch (IOException e) {
LOGGER.error("close fqueue index file failed", e);
}
}
}
private static class MFQueueBlock {
private static final String BLOCK_FILE_SUFFIX = ".blk"; // 数据文件
private static final int BLOCK_SIZE = 32 * 1024 * 1024; // 32MB
private final int EOF = -1;
private String blockFilePath;
private MFQueueIndex index;
private RandomAccessFile blockFile;
private FileChannel fileChannel;
private ByteBuffer byteBuffer;
private MappedByteBuffer mappedBlock;
public MFQueueBlock(String blockFilePath, MFQueueIndex index, RandomAccessFile blockFile, FileChannel fileChannel,
ByteBuffer byteBuffer, MappedByteBuffer mappedBlock) {
this.blockFilePath = blockFilePath;
this.index = index;
this.blockFile = blockFile;
this.fileChannel = fileChannel;
this.byteBuffer = byteBuffer;
this.mappedBlock = mappedBlock;
}
public MFQueueBlock(MFQueueIndex index, String blockFilePath) {
this.index = index;
this.blockFilePath = blockFilePath;
try {
File file = new File(blockFilePath);
this.blockFile = new RandomAccessFile(file, "rw");
this.fileChannel = blockFile.getChannel();
this.mappedBlock = fileChannel.map(FileChannel.MapMode.READ_WRITE, 0, BLOCK_SIZE);
this.byteBuffer = mappedBlock.load();
} catch (Exception e) {
throw new IllegalArgumentException(e);
}
}
public MFQueueBlock duplicate() {
return new MFQueueBlock(this.blockFilePath, this.index, this.blockFile, this.fileChannel,
this.byteBuffer.duplicate(), this.mappedBlock);
}
public static String formatBlockFilePath(String queueName, int fileNum, String fileBackupDir) {
return fileBackupDir + File.separator + String.format("fblock_%s_%d%s", queueName, fileNum, BLOCK_FILE_SUFFIX);
}
public String getBlockFilePath() {
return blockFilePath;
}
public void putEOF() {
this.byteBuffer.position(index.getWritePosition());
this.byteBuffer.putInt(EOF);
}
public boolean isSpaceAvailable(int len) {
int increment = len + 4;
int writePosition = index.getWritePosition();
return BLOCK_SIZE >= increment + writePosition + 4; // 保证最后有4字节的空间可以写入EOF
}
public boolean eof() {
int readPosition = index.getReadPosition();
return readPosition > 0 && byteBuffer.getInt(readPosition) == EOF;
}
public int write(byte[] bytes) {
int len = bytes.length;
int increment = len + 4;
int writePosition = index.getWritePosition();
byteBuffer.position(writePosition);
byteBuffer.putInt(len);
byteBuffer.put(bytes);
index.putWritePosition(increment + writePosition);
index.putWriteCounter(index.getWriteCounter() + 1);
return increment;
}
public byte[] read() {
byte[] bytes;
int readNum = index.getReadNum();
int readPosition = index.getReadPosition();
int writeNum = index.getWriteNum();
int writePosition = index.getWritePosition();
if (readNum == writeNum && readPosition >= writePosition) {
return null;
}
byteBuffer.position(readPosition);
int dataLength = byteBuffer.getInt();
if (dataLength <= 0) {
return null;
}
bytes = new byte[dataLength];
byteBuffer.get(bytes);
index.putReadPosition(readPosition + bytes.length + 4);
index.putReadCounter(index.getReadCounter() + 1);
return bytes;
}
public void sync() {
if (mappedBlock != null) {
mappedBlock.force();
}
}
public void close() {
try {
if (mappedBlock == null) {
return;
}
sync();
AccessController.doPrivileged(new PrivilegedAction<Object>() {
public Object run() {
try {
Method getCleanerMethod = mappedBlock.getClass().getMethod("cleaner");
getCleanerMethod.setAccessible(true);
sun.misc.Cleaner cleaner = (sun.misc.Cleaner) getCleanerMethod.invoke(mappedBlock);
cleaner.clean();
} catch (Exception e) {
LOGGER.error("close fqueue block file failed", e);
}
return null;
}
});
mappedBlock = null;
byteBuffer = null;
fileChannel.close();
blockFile.close();
} catch (IOException e) {
LOGGER.error("close fqueue block file failed", e);
}
}
}
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原文地址：http://my.oschina.net/xnkl/blog/477690
