一、刷新服务
image.png
二、GroupCommitService
(一) GroupCommitService核心属性
List
requestsWrite：请求写入队列 List
requestsRead：请求读队列
上面两个队列会进行交换，每次刷盘请求是写到requestsWrite队列中，GroupCommitService处理刷盘请求之前，会执行队列交换
(二) 添加刷盘请求
当消息写到缓冲池以后，会调用下面方面进行磁盘刷新和主从复制
handleDiskFlush(result, putMessageResult, msg);
handleHA(result, putMessageResult, msg);
如果刷盘方式是同步，那么就构造一个GroupCommitRequest请求，GroupCommitService服务异步刷新数据，如果是异步刷盘，就唤醒异步刷盘服务
public void handleDiskFlush(AppendMessageResult result, PutMessageResult putMessageResult, MessageExt messageExt) {
// 同步刷盘
if (FlushDiskType.SYNC_FLUSH == this.defaultMessageStore.getMessageStoreConfig().getFlushDiskType()) {
final GroupCommitService service = (GroupCommitService) this.flushCommitLogService;
if (messageExt.isWaitStoreMsgOK()) {
GroupCommitRequest request = new GroupCommitRequest(result.getWroteOffset() + result.getWroteBytes());
// 将刷盘请求放到队列中
service.putRequest(request);
// 使用了CountDownLatch机制，等待刷盘成功
boolean flushOK = request.waitForFlush(this.defaultMessageStore.getMessageStoreConfig().getSyncFlushTimeout());
if (!flushOK) {
log.error("do groupcommit, wait for flush failed, topic: " + messageExt.getTopic() + " tags: " + messageExt.getTags()
+ " client address: " + messageExt.getBornHostString());
putMessageResult.setPutMessageStatus(PutMessageStatus.FLUSH_DISK_TIMEOUT);
}
} else {
service.wakeup();
}
}
// 异步刷盘
else {
if (!this.defaultMessageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
flushCommitLogService.wakeup();
} else {
commitLogService.wakeup();
}
}
}
(三) 刷盘请求处理
GroupCommitService从队列中取出刷盘请求，并执行刷盘操作
public void run() {
CommitLog.log.info(this.getServiceName() + " service started");
while (!this.isStopped()) {
try {
// 每隔10ms，交换读写队列
this.waitForRunning(10);
// 真正的刷盘
this.doCommit();
} catch (Exception e) {
CommitLog.log.warn(this.getServiceName() + " service has exception. ", e);
}
}
// Under normal circumstances shutdown, wait for the arrival of the
// request, and then flush
try {
Thread.sleep(10);
} catch (InterruptedException e) {
CommitLog.log.warn("GroupCommitService Exception, ", e);
}
synchronized (this) {
this.swapRequests();
}
this.doCommit();
CommitLog.log.info(this.getServiceName() + " service end");
}
每隔10ms，会进行一次读写队列的交换，并调用doCommit()方法，执行真正的磁盘刷新操作。
private void doCommit() {
synchronized (this.requestsRead) {
// 读队列不为空，遍历所有刷盘请求，执行数据刷盘操作
if (!this.requestsRead.isEmpty()) {
for (GroupCommitRequest req : this.requestsRead) {
// There may be a message in the next file, so a maximum of
// two times the flush
boolean flushOK = false;
for (int i = 0; i < 2 && !flushOK; i++) {
flushOK = CommitLog.this.mappedFileQueue.getFlushedWhere() >= req.getNextOffset();
if (!flushOK) {
CommitLog.this.mappedFileQueue.flush(0);
}
}
req.wakeupCustomer(flushOK);
}
// 设置检查点
long storeTimestamp = CommitLog.this.mappedFileQueue.getStoreTimestamp();
if (storeTimestamp > 0) {
CommitLog.this.defaultMessageStore.getStoreCheckpoint().setPhysicMsgTimestamp(storeTimestamp);
}
// 处理完刷盘请求以后，执行队列清空操作
this.requestsRead.clear();
} else {
// Because of individual messages is set to not sync flush, it
// will come to this process
CommitLog.this.mappedFileQueue.flush(0);
}
}
}
三、FlushRealTimeService
(一) 核心属性
long lastFlushTimestamp：最后一次刷盘时间戳
long printTimes = 0：
(二) 异步刷盘流程
public void run() {
while (!this.isStopped()) {
// 刷新策略(默认是实时刷盘)
boolean flushCommitLogTimed = CommitLog.this.defaultMessageStore.getMessageStoreConfig().isFlushCommitLogTimed();
// 刷盘间隔
int interval = CommitLog.this.defaultMessageStore.getMessageStoreConfig().getFlushIntervalCommitLog();
// 每次刷盘至少需要多少个page(默认是4个)
int flushPhysicQueueLeastPages = CommitLog.this.defaultMessageStore.getMessageStoreConfig().getFlushCommitLogLeastPages();
// 彻底刷盘间隔时间（默认10s）
int flushPhysicQueueThoroughInterval =
CommitLog.this.defaultMessageStore.getMessageStoreConfig().getFlushCommitLogThoroughInterval();
boolean printFlushProgress = false;
// Print flush progress
long currentTimeMillis = System.currentTimeMillis();
// 当前时间 >（最后一次刷盘时间 + 彻底刷盘间隔时间（10s）），则将最新一次刷盘时间更新为当前时间
if (currentTimeMillis >= (this.lastFlushTimestamp + flushPhysicQueueThoroughInterval)) {
this.lastFlushTimestamp = currentTimeMillis;
flushPhysicQueueLeastPages = 0;
printFlushProgress = (printTimes++ % 10) == 0;
}
try {
if (flushCommitLogTimed) {
Thread.sleep(interval);
} else {
this.waitForRunning(interval);
}
if (printFlushProgress) {
this.printFlushProgress();
}
long begin = System.currentTimeMillis();
CommitLog.this.org.apache.rocketmq.store.MappedFileQueue#flush;
long storeTimestamp = CommitLog.this.mappedFileQueue.getStoreTimestamp();
if (storeTimestamp > 0) {
CommitLog.this.defaultMessageStore.getStoreCheckpoint().setPhysicMsgTimestamp(storeTimestamp);
}
long past = System.currentTimeMillis() - begin;
if (past > 500) {
log.info("Flush data to disk costs {} ms", past);
}
} catch (Throwable e) {
CommitLog.log.warn(this.getServiceName() + " service has exception. ", e);
this.printFlushProgress();
}
}
// Normal shutdown, to ensure that all the flush before exit
boolean result = false;
for (int i = 0; i < RETRY_TIMES_OVER && !result; i++) {
result = CommitLog.this.mappedFileQueue.flush(0);
CommitLog.log.info(this.getServiceName() + " service shutdown, retry " + (i + 1) + " times " + (result ? "OK" : "Not OK"));
}
this.printFlushProgress();
CommitLog.log.info(this.getServiceName() + " service end");
}
如果是实时刷盘，每隔一定时间间隔，该线程休眠500毫秒，如果不是实时刷盘，则调用waitForRunning，即每隔500毫秒或该刷盘服务线程调用了wakeup（）方法之后结束阻塞。最后调用 CommitLog.this.mappedFileQueue.flush(flushPhysicQueueLeastPages)进行刷盘 。
数据刷盘调用了MappedFileQueue.flush(int flushLeastPages)方法，进行刷盘
public boolean flush(final int flushLeastPages) {
boolean result = true;
// 根据offset,找到对应的MappedFile
MappedFile mappedFile = this.findMappedFileByOffset(this.flushedWhere, this.flushedWhere == 0);
if (mappedFile != null) {
long tmpTimeStamp = mappedFile.getStoreTimestamp();
// 调用MappedFile的刷盘方法
int offset = mappedFile.flush(flushLeastPages);
long where = mappedFile.getFileFromOffset() + offset;
result = where == this.flushedWhere;
this.flushedWhere = where;
if (0 == flushLeastPages) {
this.storeTimestamp = tmpTimeStamp;
}
}
return result;
}
数据刷盘，最终是调用 了MappedFile.flush(int flushLeastPages)方法实现数据持久化，具体实现如下：
/**
* @return The current flushed position
*/
public int flush(final int flushLeastPages) {
// 判断是否可以刷盘
if (this.isAbleToFlush(flushLeastPages)) {
if (this.hold()) {
int value = getReadPosition();
try {
//We only append data to fileChannel or mappedByteBuffer, never both.
if (writeBuffer != null || this.fileChannel.position() != 0) {
this.fileChannel.force(false);
} else {
this.mappedByteBuffer.force();
}
} catch (Throwable e) {
log.error("Error occurred when force data to disk.", e);
}
this.flushedPosition.set(value);
this.release();
} else {
log.warn("in flush, hold failed, flush offset = " + this.flushedPosition.get());
this.flushedPosition.set(getReadPosition());
}
}
return this.getFlushedPosition();
}
调用isAbleToFlush方法判断是否可以刷盘，判断逻辑如下：
private boolean isAbleToFlush(final int flushLeastPages) {
int flush = this.flushedPosition.get();
int write = getReadPosition();
// 如果文件已满
if (this.isFull()) {
return true;
}
// 需要刷盘页数 > 最少刷盘页数
if (flushLeastPages > 0) {
return ((write / OS_PAGE_SIZE) - (flush / OS_PAGE_SIZE)) >= flushLeastPages;
}
return write > flush;
}