CommitLog 加载文件
CommitLog 加载文件
public boolean load() {
//①调用mappedFileQueue.load()加载
boolean result = this.mappedFileQueue.load();
log.info("load commit log " + (result ? "OK" : "Failed"));
return result;
}
①调用mappedFileQueue.load()加载commitlog文件
MappedFileQueue
构造函数
public MappedFileQueue(final String storePath, int mappedFileSize,
AllocateMappedFileService allocateMappedFileService) {
①
this.storePath = storePath;
②
this.mappedFileSize = mappedFileSize;
③
this.allocateMappedFileService = allocateMappedFileService;
}
① storePath 文件夹目录 默认路径:System.getProperty("user.home")/store/commitlog"
② mappedFileSize 单个文件大小，默认1个G
③ allocateMappedFileService 创建文件服务
load加载文件
public boolean load() {
File dir = new File(this.storePath);
File[] files = dir.listFiles();
if (files != null) {
// ascending order
Arrays.sort(files);
for (File file : files) {
//只加载mappedFileSize大小的文件 默认1g 也就是只加载已写满的文件
if (file.length() != this.mappedFileSize) {
log.warn(file + "\t" + file.length()
+ " length not matched message store config value, ignore it");
return true;
}
try {
//加载文件
MappedFile mappedFile = new MappedFile(file.getPath(), mappedFileSize);
//文件已写满 设置对应的指针为mappedFileSize
mappedFile.setWrotePosition(this.mappedFileSize);
mappedFile.setFlushedPosition(this.mappedFileSize);
mappedFile.setCommittedPosition(this.mappedFileSize);
this.mappedFiles.add(mappedFile);
log.info("load " + file.getPath() + " OK");
} catch (IOException e) {
log.error("load file " + file + " error", e);
return false;
}
}
}
return true;
}
MappedFile
init
public MappedFile(final String fileName, final int fileSize) throws IOException {
init(fileName, fileSize);
}
private void init(final String fileName, final int fileSize) throws IOException {
this.fileName = fileName;
this.fileSize = fileSize;
this.file = new File(fileName);
//文件名就是全局偏移量
this.fileFromOffset = Long.parseLong(this.file.getName());
boolean ok = false;
ensureDirOK(this.file.getParent());
try {
//文件通道
this.fileChannel = new RandomAccessFile(this.file, "rw").getChannel();
//mmap操作 文件和内存的映射
this.mappedByteBuffer = this.fileChannel.map(MapMode.READ_WRITE, 0, fileSize);
TOTAL_MAPPED_VIRTUAL_MEMORY.addAndGet(fileSize);
TOTAL_MAPPED_FILES.incrementAndGet();
ok = true;
} catch (FileNotFoundException e) {
log.error("create file channel " + this.fileName + " Failed. ", e);
throw e;
} catch (IOException e) {
log.error("map file " + this.fileName + " Failed. ", e);
throw e;
} finally {
if (!ok && this.fileChannel != null) {
this.fileChannel.close();
}
}
}
fileChannel.map使用mmap来使虚拟内存和文件直接映射，从而使文件的读写不用经过内核态
可以看到mappedByteBuffer这里被初始化了，是对于文件的映射内存区域。这个init方法中没有对writeBuffer设置的操作。那么writeBuffer什么时候会被设置呢？
MappedFileQueue load的时候不会加载未写满的文件，那未写满或者未创建的文件是什么时候被加载或创建的？
以下是commitLog#putMessage时的代码片段
//①获取文件队列里最后一个文件
MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile();
putMessageLock.lock(); //spin or ReentrantLock ,depending on store config
try {
long beginLockTimestamp = this.defaultMessageStore.getSystemClock().now();
this.beginTimeInLock = beginLockTimestamp;
// Here settings are stored timestamp, in order to ensure an orderly
// global
msg.setStoreTimestamp(beginLockTimestamp);
//②获取的文件为null或者文件已经写满
if (null == mappedFile || mappedFile.isFull()) {
//创建或者加载最后一个文件
mappedFile = this.mappedFileQueue.getLastMappedFile(0); // Mark: NewFile may be cause noise
}
① 获取文件队列里最后一个文件
② 如果获取的文件为null或者文件已经写满，创建或者加载最后一个文件
分析MappedFileQueue#getLastMappedFile(0)方法
public MappedFile getLastMappedFile(final long startOffset) {
return getLastMappedFile(startOffset, true);
}
public MappedFile getLastMappedFile(final long startOffset, boolean needCreate) {
long createOffset = -1;
//① 获取最后一个文件
MappedFile mappedFileLast = getLastMappedFile();
//② 文件是空的 createOffset = 0 - 0 = 0
if (mappedFileLast == null) {
createOffset = startOffset - (startOffset % this.mappedFileSize);
}
//③ 文件不是空的并且已经写满 createOffset = 最后一个文件的开始偏移量加上单个文件的大小默认1g
if (mappedFileLast != null && mappedFileLast.isFull()) {
createOffset = mappedFileLast.getFileFromOffset() + this.mappedFileSize;
}
if (createOffset != -1 && needCreate) {
//当前要创建或者加载的文件的文件名
String nextFilePath = this.storePath + File.separator + UtilAll.offset2FileName(createOffset);
//下一个要被创建的文件名
String nextNextFilePath = this.storePath + File.separator
+ UtilAll.offset2FileName(createOffset + this.mappedFileSize);
MappedFile mappedFile = null;
//如果allocateMappedFileService不为空 如果是commitlog文件allocateMappedFileService是不为空的
if (this.allocateMappedFileService != null) {
//allocateMappedFileService创建一个创建文件的异步请求
mappedFile = this.allocateMappedFileService.putRequestAndReturnMappedFile(nextFilePath,
nextNextFilePath, this.mappedFileSize);
} else {
try {
mappedFile = new MappedFile(nextFilePath, this.mappedFileSize);
} catch (IOException e) {
log.error("create mappedFile exception", e);
}
}
if (mappedFile != null) {
if (this.mappedFiles.isEmpty()) {
mappedFile.setFirstCreateInQueue(true);
}
this.mappedFiles.add(mappedFile);
}
return mappedFile;
}
return mappedFileLast;
}
AllocateMappedFileService
putRequestAndReturnMappedFile
public MappedFile putRequestAndReturnMappedFile(String nextFilePath, String nextNextFilePath, int fileSize) {
int canSubmitRequests = 2;
if (this.messageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
if (this.messageStore.getMessageStoreConfig().isFastFailIfNoBufferInStorePool()
&& BrokerRole.SLAVE != this.messageStore.getMessageStoreConfig().getBrokerRole()) { //if broker is slave, don't fast fail even no buffer in pool
//可以提交的请求数量 TransientStorePool剩余buffer数量 - requestQueue请求队列数
canSubmitRequests = this.messageStore.getTransientStorePool().remainBufferNumbs() - this.requestQueue.size();
}
}
//创建请求
AllocateRequest nextReq = new AllocateRequest(nextFilePath, fileSize);
boolean nextPutOK = this.requestTable.putIfAbsent(nextFilePath, nextReq) == null;
if (nextPutOK) {
//没有可用的buffer了 快速失败
if (canSubmitRequests <= 0) {
log.warn("[NOTIFYME]TransientStorePool is not enough, so create mapped file error, " +
"RequestQueueSize : {}, StorePoolSize: {}", this.requestQueue.size(), this.messageStore.getTransientStorePool().remainBufferNumbs());
this.requestTable.remove(nextFilePath);
return null;
}
//提交请求到队列
boolean offerOK = this.requestQueue.offer(nextReq);
if (!offerOK) {
log.warn("never expected here, add a request to preallocate queue failed");
}
//可提交请求数量-1
canSubmitRequests--;
}
//预先创建下一个文件 减少创建文件阻塞的时间
AllocateRequest nextNextReq = new AllocateRequest(nextNextFilePath, fileSize);
boolean nextNextPutOK = this.requestTable.putIfAbsent(nextNextFilePath, nextNextReq) == null;
if (nextNextPutOK) {
if (canSubmitRequests <= 0) {
log.warn("[NOTIFYME]TransientStorePool is not enough, so skip preallocate mapped file, " +
"RequestQueueSize : {}, StorePoolSize: {}", this.requestQueue.size(), this.messageStore.getTransientStorePool().remainBufferNumbs());
this.requestTable.remove(nextNextFilePath);
} else {
//提交请求
boolean offerOK = this.requestQueue.offer(nextNextReq);
if (!offerOK) {
log.warn("never expected here, add a request to preallocate queue failed");
}
}
}
if (hasException) {
log.warn(this.getServiceName() + " service has exception. so return null");
return null;
}
AllocateRequest result = this.requestTable.get(nextFilePath);
try {
if (result != null) {
//同步获取创建的mappedFile，超时时间5秒
boolean waitOK = result.getCountDownLatch().await(waitTimeOut, TimeUnit.MILLISECONDS);
if (!waitOK) {
log.warn("create mmap timeout " + result.getFilePath() + " " + result.getFileSize());
return null;
} else {
//删除requestTable里的请求 返回创建完成的mappedFile
this.requestTable.remove(nextFilePath);
return result.getMappedFile();
}
} else {
log.error("find preallocate mmap failed, this never happen");
}
} catch (InterruptedException e) {
log.warn(this.getServiceName() + " service has exception. ", e);
}
return null;
}
AllocateMappedFileService后台运行的代码
public void run() {
log.info(this.getServiceName() + " service started");
while (!this.isStopped() && this.mmapOperation()) {
}
log.info(this.getServiceName() + " service end");
}
mmapOperation 创建或加载文件的底层逻辑
private boolean mmapOperation() {
boolean isSuccess = false;
AllocateRequest req = null;
try {
//从请求队列中取出请求
req = this.requestQueue.take();
AllocateRequest expectedRequest = this.requestTable.get(req.getFilePath());
if (null == expectedRequest) {
log.warn("this mmap request expired, maybe cause timeout " + req.getFilePath() + " "
+ req.getFileSize());
return true;
}
if (expectedRequest != req) {
log.warn("never expected here, maybe cause timeout " + req.getFilePath() + " "
+ req.getFileSize() + ", req:" + req + ", expectedRequest:" + expectedRequest);
return true;
}
if (req.getMappedFile() == null) {
long beginTime = System.currentTimeMillis();
MappedFile mappedFile;
//有无开启TransientStorePoolEnable(默认是关闭的) 且要满足异步刷盘以及角色是主
if (messageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
try {
mappedFile = ServiceLoader.load(MappedFile.class).iterator().next();
//初始化mappedFile
mappedFile.init(req.getFilePath(), req.getFileSize(), messageStore.getTransientStorePool());
} catch (RuntimeException e) {
log.warn("Use default implementation.");
mappedFile = new MappedFile(req.getFilePath(), req.getFileSize(), messageStore.getTransientStorePool());
}
} else {
//初始化mappedFile
mappedFile = new MappedFile(req.getFilePath(), req.getFileSize());
}
long eclipseTime = UtilAll.computeEclipseTimeMilliseconds(beginTime);
if (eclipseTime > 10) {
int queueSize = this.requestQueue.size();
log.warn("create mappedFile spent time(ms) " + eclipseTime + " queue size " + queueSize
+ " " + req.getFilePath() + " " + req.getFileSize());
}
// pre write mappedFile 是否需要预热文件 (默认是关闭的 生产环境也不建议开启)
if (mappedFile.getFileSize() >= this.messageStore.getMessageStoreConfig()
.getMapedFileSizeCommitLog()
&&
this.messageStore.getMessageStoreConfig().isWarmMapedFileEnable()) {
mappedFile.warmMappedFile(this.messageStore.getMessageStoreConfig().getFlushDiskType(),
this.messageStore.getMessageStoreConfig().getFlushLeastPagesWhenWarmMapedFile());
}
req.setMappedFile(mappedFile);
this.hasException = false;
isSuccess = true;
}
} catch (InterruptedException e) {
log.warn(this.getServiceName() + " interrupted, possibly by shutdown.");
this.hasException = true;
return false;
} catch (IOException e) {
log.warn(this.getServiceName() + " service has exception. ", e);
this.hasException = true;
if (null != req) {
requestQueue.offer(req);
try {
Thread.sleep(1);
} catch (InterruptedException ignored) {
}
}
} finally {
if (req != null && isSuccess)
req.getCountDownLatch().countDown();
}
return true;
这里如果开启了TransientStorePoolEnable加载文件会调用以下代码
mappedFile.init(req.getFilePath(), req.getFileSize(), messageStore.getTransientStorePool());
public void init(final String fileName, final int fileSize,
final TransientStorePool transientStorePool) throws IOException {
init(fileName, fileSize);
this.writeBuffer = transientStorePool.borrowBuffer();
this.transientStorePool = transientStorePool;
}
这里和MappedFileQueue加载文件时候的区别就是多了一个TransientStorePool参数，可以看到
writeBuffer这里被赋值了transientStorePool.borrowBuffer()
public ByteBuffer borrowBuffer() {
//从availableBuffers获取第一个
ByteBuffer buffer = availableBuffers.pollFirst();
if (availableBuffers.size() < poolSize * 0.4) {
log.warn("TransientStorePool only remain {} sheets.", availableBuffers.size());
}
return buffer;
}
那么availableBuffers是从哪里来的呢？
public void init() {
for (int i = 0; i < poolSize; i++) {
ByteBuffer byteBuffer = ByteBuffer.allocateDirect(fileSize);
final long address = ((DirectBuffer) byteBuffer).address();
Pointer pointer = new Pointer(address);
LibC.INSTANCE.mlock(pointer, new NativeLong(fileSize));
availableBuffers.offer(byteBuffer);
}
}
在init方法中申请了poolSize（默认5）个堆外内存区DirectBuffer，并且使用LibC.INSTANCE.mlock内存锁定了这块内存区域，防止页缓存被硬盘交换。
