RocketMQ(七):高性能探秘之MappedFile

RocketMQ作为消息中间件,经常会被用来和其他消息中间件做比较,比对rabbitmq, kafka… 但个人觉得它一直对标的,都是kafka。因为它们面对的场景往往都是超高并发,超高性能要求的场景。

所以,有必要深挖下其实现高性能,高并发的原因。实际上,这是非常大的话题,我这里也不打算一口吃个大胖子。我会给出个大概答案,然后我们再深入挖掘其中部分实现。如题所述。

1. 高性能高并发系统的底层技能概述

我不打算单讲rocketmq到底是如何实现高性能高并发的,因为实际上的底层原则都是差不多的。rocketmq不过是其中的一个实现者而已。

那么,要想实现高性能高并发,大概需要怎么做的呢?本质上讲,我们的系统服务能利用的东西并不多,CPU、内存、磁盘、网络、硬件特性。。。 当然了,还有一个非常重要的东西,就是我们基本都是在做应用层服务,所以我们的能力往往必须依托于操作系统提供的服务,由这些服务去更好地利用底层硬件的东西。好吧,显得逼格好像有点高了,实际上就是一个系统API调用。

接下来,我们从每个小点出发,来看看我们如何做到高性能高并发:

第一个:CPU。可以说,CPU代表了单机的极限。如果能够做有效利用CPU, 使其随时可保证在80%以上的使用率,那么你这个服务绝对够牛逼了(注意不是导致疯狂GC的那种利用率哦)。那么,我们如何做到高效利用CPU呢?有些应用天然就是CPU型的,比如提供一些做大数的运算服务,天生就需要大量CPU运算。而其他的很多的IO型的应用,则CPU往往不会太高,或者说我们应该往高了的方向优化。

第二个:内存。内存是一个非常宝贵的资源,因为内存的调度速度非常快。如果一个应用的业务处理都是基于内存的,那么这个应用基本上就会超级强悍。大部分情况下,越大的内存往往也能提供越高的性能,比如ES的搜索服务,要想性能好必需有足够内存。当然了,内存除了使用起来非常方便之外,它还有一个重要的工作,就是内存的回收。当然,这部分工作一般都会被编程屏蔽掉,因为它实在太难了。我们一般只需按照语言特性,合理的处理对象即可。另外,我们可以一些可能需要从外部设备读入的数据,加载到内存中长期使用,这将是一件非常重要的优化动作。如何维护好数据一致性与安全性和准确性,是这类工作的重点。

第三个:磁盘。内存虽好,但却不常有。内存往往意味着大小受限。而与之对应的就是磁盘,磁盘则往往意味空间非常大,数据永久存储安全。磁盘基本上就代表了单机的存储极限,但也同时限制了并发能力。

第四个:网络。也许这个名词不太合适,但却是因为网络才发生了变化。如果说前面讲的都是单机的极限性能,那么,网络就会带来分布式系统的极限性能。一个庞大的系统,一定是分布式的,因此必然会使用到网络这个设备。但我们一般不会在这上面节省多少东西,我们能做的,也许就是简单的压缩下文件数据而已。更多的,也许我们只是申请更大的带宽,或者开辟新的布线,以满足系统的需要。在网络这一环境,如何更好地组织网络设备,是重中之重,而这往往又回到了上面三个话题之一了。

最后,排除上面几个硬技能,还有一个也是非常重要的技能:那就是算法,没有好的算法,再多的优化可能也只是杯水车薪。(当然了我们大部分情况下是无需高级算法的,因为大部分时间,我们只是大自然的搬运工)

2. 高性能高并发操作系统api列举

前面说的,更多是理论上讲如何形成牛逼的应用服务。但我们又没那能力去搞操作系统的东西,所以也只能想想而已。那么说到底,我们能做什么呢?所谓工欲善其事,必先利其器。所谓利器,也就是看看操作系统提供什么样的底层API 。

我这里就稍微列几个吧(我也就知道这么些了):

epoll系列: IO多路复用技术,高并发高性能网络应用必备。大致作用就是使极少数的线程,高效地管理大量io事件,通知应用等。大概的接口有: epoll_create(), epoll_ctl(), epoll_wait();

pagecache系列: 操作系统页缓存,高效写文件必备。大致作用就是保留部分磁盘数据在内存中,以便应用想读取或者磁盘数据数据时能够非常快速的响应。相关接口如: read(), write(), readpage(), writepage(), sync(), fsync().

mmap系列: 内存映射。可以将文件映射到内存中,用户写数据时直接向该内存缓冲区写数据,即可达到写磁盘的作用了,从而提高写入性能。接口如: mmap(), munmap();

directio系列: 直接io操作,避免用户态数据到内核态数据的相互copy, 节省cpu和内存占用。

CAS系列: 高效安全锁实现。相关接口: cmpxchg() 。

多线程系列: 大部分网络应用,都io型的,那么如何同时处理多个请求就非常重要了。多线程提供非常便捷的并发编程基础,使得我们可以更简单的处理业务而且提供超高的处理能力。这自然是编程语言直接提供的。

3. rocketmq中的高性能法宝

rocketmq想要实现高并发高性能处理能力,自然要从操作系统层面去寻求方法,自然也就逃不过前面的几点说法了。

首先,它基于netty实现了高性能的网络通信,netty基于事件的io模型,零拷贝的技术,已经提供了非常好的技术前提,rocketmq只需利用一下,就可以将自己变得很厉害了。当然,这只是其厉害的一个点,因为单有了高效网络通信处理能力还不够的。至少,rocketmq得提供高效的数据序列化方式。

其次,有了netty作为通信框架,高效接入请求后,rocketmq自身处理业务的方式非常重要。如果能够直接基于内存保存数据,那必然是最高性能的。但是它不能那样做,因为内存太小,无法容纳下应有的消息。所以,只能基于文件做存储。而文件本身的操作又是代价非常高的,所以,必须要有些稍微的措施,避免重量级的操作文件。所以,文件的多级存储又是非常重要的了,即如索引文件在db中的应用就知道了。

再其次,java提供了非常好的多线程编程环境,不加以利用就对不起观众了。良好的线程模型,为其高性能呐喊助威。

最后,基于pagecache和mmap的高效文件读写,才是其制胜法宝。这也是我们接下来想要重点说明的。

4. rocketmq中对mmap和pagecache的应用

上一点中提到的每个点,都是rocketmq出众的原因,但我们今天只会来说一点:rocketmq的高效文件存储。

实际上,根据我之前的几篇文章,我们很容易找到rocketmq是如何对文件进行读写的。我们就以producer写消息数据为例,来回顾看看rmq是如何进行高效文件存储的。

// 处理器入口
// org.apache.rocketmq.broker.processor.SendMessageProcessor#processRequest
@Override
public RemotingCommand processRequest(ChannelHandlerContext ctx,
RemotingCommand request) throws RemotingCommandException {
RemotingCommand response = null;
try {
response = asyncProcessRequest(ctx, request).get();
} catch (InterruptedException | ExecutionException e) {
log.error("process SendMessage error, request : " + request.toString(), e);
}
return response;
}
// 接收转发,异步处理
public CompletableFuture<RemotingCommand> asyncProcessRequest(ChannelHandlerContext ctx,
RemotingCommand request) throws RemotingCommandException {
final SendMessageContext mqtraceContext;
switch (request.getCode()) {
case RequestCode.CONSUMER_SEND_MSG_BACK:
return this.asyncConsumerSendMsgBack(ctx, request);
default:
// 写入数据
SendMessageRequestHeader requestHeader = parseRequestHeader(request);
if (requestHeader == null) {
return CompletableFuture.completedFuture(null);
}
mqtraceContext = buildMsgContext(ctx, requestHeader);
this.executeSendMessageHookBefore(ctx, request, mqtraceContext);
if (requestHeader.isBatch()) {
return this.asyncSendBatchMessage(ctx, request, mqtraceContext, requestHeader);
} else {
return this.asyncSendMessage(ctx, request, mqtraceContext, requestHeader);
}
}
}
// org.apache.rocketmq.store.CommitLog#putMessage
public PutMessageResult putMessage(final MessageExtBrokerInner msg) {
// Set the storage time
msg.setStoreTimestamp(System.currentTimeMillis());
// Set the message body BODY CRC (consider the most appropriate setting
// on the client)
msg.setBodyCRC(UtilAll.crc32(msg.getBody()));
// Back to Results
AppendMessageResult result = null;
StoreStatsService storeStatsService = this.defaultMessageStore.getStoreStatsService();
String topic = msg.getTopic();
int queueId = msg.getQueueId();
final int tranType = MessageSysFlag.getTransactionValue(msg.getSysFlag());
if (tranType == MessageSysFlag.TRANSACTION_NOT_TYPE
|| tranType == MessageSysFlag.TRANSACTION_COMMIT_TYPE) {
// Delay Delivery
if (msg.getDelayTimeLevel() > 0) {
if (msg.getDelayTimeLevel() > this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel()) {
msg.setDelayTimeLevel(this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel());
}
topic = TopicValidator.RMQ_SYS_SCHEDULE_TOPIC;
queueId = ScheduleMessageService.delayLevel2QueueId(msg.getDelayTimeLevel());
// Backup real topic, queueId
MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_TOPIC, msg.getTopic());
MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_QUEUE_ID, String.valueOf(msg.getQueueId()));
msg.setPropertiesString(MessageDecoder.messageProperties2String(msg.getProperties()));
msg.setTopic(topic);
msg.setQueueId(queueId);
}
}
InetSocketAddress bornSocketAddress = (InetSocketAddress) msg.getBornHost();
if (bornSocketAddress.getAddress() instanceof Inet6Address) {
msg.setBornHostV6Flag();
}
InetSocketAddress storeSocketAddress = (InetSocketAddress) msg.getStoreHost();
if (storeSocketAddress.getAddress() instanceof Inet6Address) {
msg.setStoreHostAddressV6Flag();
}
long elapsedTimeInLock = 0;
MappedFile unlockMappedFile = null;
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);
if (null == mappedFile || mappedFile.isFull()) {
mappedFile = this.mappedFileQueue.getLastMappedFile(0); // Mark: NewFile may be cause noise
}
if (null == mappedFile) {
log.error("create mapped file1 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, null);
}
result = mappedFile.appendMessage(msg, this.appendMessageCallback);
switch (result.getStatus()) {
case PUT_OK:
break;
case END_OF_FILE:
unlockMappedFile = mappedFile;
// Create a new file, re-write the message
mappedFile = this.mappedFileQueue.getLastMappedFile(0);
if (null == mappedFile) {
// XXX: warn and notify me
log.error("create mapped file2 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, result);
}
result = mappedFile.appendMessage(msg, this.appendMessageCallback);
break;
case MESSAGE_SIZE_EXCEEDED:
case PROPERTIES_SIZE_EXCEEDED:
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, result);
case UNKNOWN_ERROR:
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result);
default:
beginTimeInLock = 0;
return new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result);
}
elapsedTimeInLock = this.defaultMessageStore.getSystemClock().now() - beginLockTimestamp;
beginTimeInLock = 0;
} finally {
putMessageLock.unlock();
}
if (elapsedTimeInLock > 500) {
log.warn("[NOTIFYME]putMessage in lock cost time(ms)={}, bodyLength={} AppendMessageResult={}", elapsedTimeInLock, msg.getBody().length, result);
}
if (null != unlockMappedFile && this.defaultMessageStore.getMessageStoreConfig().isWarmMapedFileEnable()) {
this.defaultMessageStore.unlockMappedFile(unlockMappedFile);
}
PutMessageResult putMessageResult = new PutMessageResult(PutMessageStatus.PUT_OK, result);
// Statistics
storeStatsService.getSinglePutMessageTopicTimesTotal(msg.getTopic()).incrementAndGet();
storeStatsService.getSinglePutMessageTopicSizeTotal(topic).addAndGet(result.getWroteBytes());
handleDiskFlush(result, putMessageResult, msg);
handleHA(result, putMessageResult, msg);
return putMessageResult;
}
// org.apache.rocketmq.broker.processor.SendMessageProcessor#asyncSendMessage
private CompletableFuture<RemotingCommand> asyncSendMessage(ChannelHandlerContext ctx, RemotingCommand request,
SendMessageContext mqtraceContext,
SendMessageRequestHeader requestHeader) {
final RemotingCommand response = preSend(ctx, request, requestHeader);
final SendMessageResponseHeader responseHeader = (SendMessageResponseHeader)response.readCustomHeader();
if (response.getCode() != -1) {
return CompletableFuture.completedFuture(response);
}
final byte[] body = request.getBody();
int queueIdInt = requestHeader.getQueueId();
TopicConfig topicConfig = this.brokerController.getTopicConfigManager().selectTopicConfig(requestHeader.getTopic());
if (queueIdInt < 0) {
queueIdInt = randomQueueId(topicConfig.getWriteQueueNums());
}
MessageExtBrokerInner msgInner = new MessageExtBrokerInner();
msgInner.setTopic(requestHeader.getTopic());
msgInner.setQueueId(queueIdInt);
if (!handleRetryAndDLQ(requestHeader, response, request, msgInner, topicConfig)) {
return CompletableFuture.completedFuture(response);
}
msgInner.setBody(body);
msgInner.setFlag(requestHeader.getFlag());
MessageAccessor.setProperties(msgInner, MessageDecoder.string2messageProperties(requestHeader.getProperties()));
msgInner.setPropertiesString(requestHeader.getProperties());
msgInner.setBornTimestamp(requestHeader.getBornTimestamp());
msgInner.setBornHost(ctx.channel().remoteAddress());
msgInner.setStoreHost(this.getStoreHost());
msgInner.setReconsumeTimes(requestHeader.getReconsumeTimes() == null ? 0 : requestHeader.getReconsumeTimes());
String clusterName = this.brokerController.getBrokerConfig().getBrokerClusterName();
MessageAccessor.putProperty(msgInner, MessageConst.PROPERTY_CLUSTER, clusterName);
msgInner.setPropertiesString(MessageDecoder.messageProperties2String(msgInner.getProperties()));
CompletableFuture<PutMessageResult> putMessageResult = null;
Map<String, String> origProps = MessageDecoder.string2messageProperties(requestHeader.getProperties());
String transFlag = origProps.get(MessageConst.PROPERTY_TRANSACTION_PREPARED);
if (transFlag != null && Boolean.parseBoolean(transFlag)) {
if (this.brokerController.getBrokerConfig().isRejectTransactionMessage()) {
response.setCode(ResponseCode.NO_PERMISSION);
response.setRemark(
"the broker[" + this.brokerController.getBrokerConfig().getBrokerIP1()
+ "] sending transaction message is forbidden");
return CompletableFuture.completedFuture(response);
}
putMessageResult = this.brokerController.getTransactionalMessageService().asyncPrepareMessage(msgInner);
} else {
// 简单起见,我们只看非事务的消息写入
putMessageResult = this.brokerController.getMessageStore().asyncPutMessage(msgInner);
}
return handlePutMessageResultFuture(putMessageResult, response, request, msgInner, responseHeader, mqtraceContext, ctx, queueIdInt);
}
// org.apache.rocketmq.store.DefaultMessageStore#asyncPutMessage
@Override
public CompletableFuture<PutMessageResult> asyncPutMessage(MessageExtBrokerInner msg) {
PutMessageStatus checkStoreStatus = this.checkStoreStatus();
if (checkStoreStatus != PutMessageStatus.PUT_OK) {
return CompletableFuture.completedFuture(new PutMessageResult(checkStoreStatus, null));
}
PutMessageStatus msgCheckStatus = this.checkMessage(msg);
if (msgCheckStatus == PutMessageStatus.MESSAGE_ILLEGAL) {
return CompletableFuture.completedFuture(new PutMessageResult(msgCheckStatus, null));
}
// 写入消息数据到commitLog中
long beginTime = this.getSystemClock().now();
CompletableFuture<PutMessageResult> putResultFuture = this.commitLog.asyncPutMessage(msg);
putResultFuture.thenAccept((result) -> {
long elapsedTime = this.getSystemClock().now() - beginTime;
if (elapsedTime > 500) {
log.warn("putMessage not in lock elapsed time(ms)={}, bodyLength={}", elapsedTime, msg.getBody().length);
}
this.storeStatsService.setPutMessageEntireTimeMax(elapsedTime);
if (null == result || !result.isOk()) {
this.storeStatsService.getPutMessageFailedTimes().incrementAndGet();
}
});
return putResultFuture;
}
// 写入消息数据到commitLog中
// org.apache.rocketmq.store.CommitLog#asyncPutMessage
public CompletableFuture<PutMessageResult> asyncPutMessage(final MessageExtBrokerInner msg) {
// Set the storage time
msg.setStoreTimestamp(System.currentTimeMillis());
// Set the message body BODY CRC (consider the most appropriate setting
// on the client)
msg.setBodyCRC(UtilAll.crc32(msg.getBody()));
// Back to Results
AppendMessageResult result = null;
StoreStatsService storeStatsService = this.defaultMessageStore.getStoreStatsService();
String topic = msg.getTopic();
int queueId = msg.getQueueId();
final int tranType = MessageSysFlag.getTransactionValue(msg.getSysFlag());
if (tranType == MessageSysFlag.TRANSACTION_NOT_TYPE
|| tranType == MessageSysFlag.TRANSACTION_COMMIT_TYPE) {
// Delay Delivery
if (msg.getDelayTimeLevel() > 0) {
if (msg.getDelayTimeLevel() > this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel()) {
msg.setDelayTimeLevel(this.defaultMessageStore.getScheduleMessageService().getMaxDelayLevel());
}
topic = TopicValidator.RMQ_SYS_SCHEDULE_TOPIC;
queueId = ScheduleMessageService.delayLevel2QueueId(msg.getDelayTimeLevel());
// Backup real topic, queueId
MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_TOPIC, msg.getTopic());
MessageAccessor.putProperty(msg, MessageConst.PROPERTY_REAL_QUEUE_ID, String.valueOf(msg.getQueueId()));
msg.setPropertiesString(MessageDecoder.messageProperties2String(msg.getProperties()));
msg.setTopic(topic);
msg.setQueueId(queueId);
}
}
long elapsedTimeInLock = 0;
// 获取mappedFile实例,后续将向其写入数据
MappedFile unlockMappedFile = null;
MappedFile mappedFile = this.mappedFileQueue.getLastMappedFile();
// 上锁写数据,保证数据写入安全准确
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);
// 确保mappedFile有效
if (null == mappedFile || mappedFile.isFull()) {
mappedFile = this.mappedFileQueue.getLastMappedFile(0); // Mark: NewFile may be cause noise
}
if (null == mappedFile) {
log.error("create mapped file1 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
beginTimeInLock = 0;
return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, null));
}
// 向mappedFile中追加数据,完成写入动作
result = mappedFile.appendMessage(msg, this.appendMessageCallback);
switch (result.getStatus()) {
case PUT_OK:
break;
case END_OF_FILE:
unlockMappedFile = mappedFile;
// Create a new file, re-write the message
mappedFile = this.mappedFileQueue.getLastMappedFile(0);
if (null == mappedFile) {
// XXX: warn and notify me
log.error("create mapped file2 error, topic: " + msg.getTopic() + " clientAddr: " + msg.getBornHostString());
beginTimeInLock = 0;
return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.CREATE_MAPEDFILE_FAILED, result));
}
result = mappedFile.appendMessage(msg, this.appendMessageCallback);
break;
case MESSAGE_SIZE_EXCEEDED:
case PROPERTIES_SIZE_EXCEEDED:
beginTimeInLock = 0;
return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.MESSAGE_ILLEGAL, result));
case UNKNOWN_ERROR:
beginTimeInLock = 0;
return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result));
default:
beginTimeInLock = 0;
return CompletableFuture.completedFuture(new PutMessageResult(PutMessageStatus.UNKNOWN_ERROR, result));
}
elapsedTimeInLock = this.defaultMessageStore.getSystemClock().now() - beginLockTimestamp;
beginTimeInLock = 0;
} finally {
putMessageLock.unlock();
}
if (elapsedTimeInLock > 500) {
log.warn("[NOTIFYME]putMessage in lock cost time(ms)={}, bodyLength={} AppendMessageResult={}", elapsedTimeInLock, msg.getBody().length, result);
}
if (null != unlockMappedFile && this.defaultMessageStore.getMessageStoreConfig().isWarmMapedFileEnable()) {
this.defaultMessageStore.unlockMappedFile(unlockMappedFile);
}
PutMessageResult putMessageResult = new PutMessageResult(PutMessageStatus.PUT_OK, result);
// Statistics
storeStatsService.getSinglePutMessageTopicTimesTotal(msg.getTopic()).incrementAndGet();
storeStatsService.getSinglePutMessageTopicSizeTotal(topic).addAndGet(result.getWroteBytes());
CompletableFuture<PutMessageStatus> flushResultFuture = submitFlushRequest(result, putMessageResult, msg);
CompletableFuture<PutMessageStatus> replicaResultFuture = submitReplicaRequest(result, putMessageResult, msg);
return flushResultFuture.thenCombine(replicaResultFuture, (flushStatus, replicaStatus) -> {
if (flushStatus != PutMessageStatus.PUT_OK) {
putMessageResult.setPutMessageStatus(PutMessageStatus.FLUSH_DISK_TIMEOUT);
}
if (replicaStatus != PutMessageStatus.PUT_OK) {
putMessageResult.setPutMessageStatus(replicaStatus);
}
return putMessageResult;
});
}
// 获取有效的mappedFile实例
// org.apache.rocketmq.store.MappedFileQueue#getLastMappedFile()
public MappedFile getLastMappedFile() {
MappedFile mappedFileLast = null;
while (!this.mappedFiles.isEmpty()) {
try {
mappedFileLast = this.mappedFiles.get(this.mappedFiles.size() - 1);
break;
} catch (IndexOutOfBoundsException e) {
//continue;
} catch (Exception e) {
log.error("getLastMappedFile has exception.", e);
break;
}
}
return mappedFileLast;
}
// 再次尝试获取 mappedFile, 没有则创建一个新的
// org.apache.rocketmq.store.MappedFileQueue#getLastMappedFile(long)
public MappedFile getLastMappedFile(final long startOffset) {
return getLastMappedFile(startOffset, true);
}
public MappedFile getLastMappedFile(final long startOffset, boolean needCreate) {
long createOffset = -1;
MappedFile mappedFileLast = getLastMappedFile();
if (mappedFileLast == null) {
createOffset = startOffset - (startOffset % this.mappedFileSize);
}
if (mappedFileLast != null && mappedFileLast.isFull()) {
createOffset = mappedFileLast.getFileFromOffset() + this.mappedFileSize;
}
if (createOffset != -1 && needCreate) {
String nextFilePath = this.storePath + File.separator + UtilAll.offset2FileName(createOffset);
String nextNextFilePath = this.storePath + File.separator
+ UtilAll.offset2FileName(createOffset + this.mappedFileSize);
MappedFile mappedFile = null;
// 分配创建一个新的commitLog文件
if (this.allocateMappedFileService != null) {
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;
}
// 向commitLog中得到的mappedFile顺序写入数据
public AppendMessageResult appendMessage(final MessageExtBrokerInner msg, final AppendMessageCallback cb) {
return appendMessagesInner(msg, cb);
}
public AppendMessageResult appendMessagesInner(final MessageExt messageExt, final AppendMessageCallback cb) {
assert messageExt != null;
assert cb != null;
int currentPos = this.wrotePosition.get();
if (currentPos < this.fileSize) {
ByteBuffer byteBuffer = writeBuffer != null ? writeBuffer.slice() : this.mappedByteBuffer.slice();
byteBuffer.position(currentPos);
AppendMessageResult result;
if (messageExt instanceof MessageExtBrokerInner) {
// 回调,写入数据到 commitLog 中
// 将数据写入 byteBuffer, 即将数据写入了pagecache, 也就写入了磁盘文件中了
result = cb.doAppend(this.getFileFromOffset(), byteBuffer, this.fileSize - currentPos, (MessageExtBrokerInner) messageExt);
} else if (messageExt instanceof MessageExtBatch) {
result = cb.doAppend(this.getFileFromOffset(), byteBuffer, this.fileSize - currentPos, (MessageExtBatch) messageExt);
} else {
return new AppendMessageResult(AppendMessageStatus.UNKNOWN_ERROR);
}
this.wrotePosition.addAndGet(result.getWroteBytes());
this.storeTimestamp = result.getStoreTimestamp();
return result;
}
log.error("MappedFile.appendMessage return null, wrotePosition: {} fileSize: {}", currentPos, this.fileSize);
return new AppendMessageResult(AppendMessageStatus.UNKNOWN_ERROR);
}
// org.apache.rocketmq.store.CommitLog.DefaultAppendMessageCallback#doAppend(long, java.nio.ByteBuffer, int, org.apache.rocketmq.store.MessageExtBrokerInner)
public AppendMessageResult doAppend(final long fileFromOffset, final ByteBuffer byteBuffer, final int maxBlank,
final MessageExtBrokerInner msgInner) {
// STORETIMESTAMP + STOREHOSTADDRESS + OFFSET <br>
// PHY OFFSET
long wroteOffset = fileFromOffset + byteBuffer.position();
int sysflag = msgInner.getSysFlag();
int bornHostLength = (sysflag & MessageSysFlag.BORNHOST_V6_FLAG) == 0 ? 4 + 4 : 16 + 4;
int storeHostLength = (sysflag & MessageSysFlag.STOREHOSTADDRESS_V6_FLAG) == 0 ? 4 + 4 : 16 + 4;
ByteBuffer bornHostHolder = ByteBuffer.allocate(bornHostLength);
ByteBuffer storeHostHolder = ByteBuffer.allocate(storeHostLength);
this.resetByteBuffer(storeHostHolder, storeHostLength);
String msgId;
if ((sysflag & MessageSysFlag.STOREHOSTADDRESS_V6_FLAG) == 0) {
msgId = MessageDecoder.createMessageId(this.msgIdMemory, msgInner.getStoreHostBytes(storeHostHolder), wroteOffset);
} else {
msgId = MessageDecoder.createMessageId(this.msgIdV6Memory, msgInner.getStoreHostBytes(storeHostHolder), wroteOffset);
}
// Record ConsumeQueue information
keyBuilder.setLength(0);
keyBuilder.append(msgInner.getTopic());
keyBuilder.append('-');
keyBuilder.append(msgInner.getQueueId());
String key = keyBuilder.toString();
Long queueOffset = CommitLog.this.topicQueueTable.get(key);
// 初始化queueId信息
if (null == queueOffset) {
queueOffset = 0L;
CommitLog.this.topicQueueTable.put(key, queueOffset);
}
// Transaction messages that require special handling
final int tranType = MessageSysFlag.getTransactionValue(msgInner.getSysFlag());
switch (tranType) {
// Prepared and Rollback message is not consumed, will not enter the
// consumer queuec
case MessageSysFlag.TRANSACTION_PREPARED_TYPE:
case MessageSysFlag.TRANSACTION_ROLLBACK_TYPE:
queueOffset = 0L;
break;
case MessageSysFlag.TRANSACTION_NOT_TYPE:
case MessageSysFlag.TRANSACTION_COMMIT_TYPE:
default:
break;
}
/**
* Serialize message
*/
final byte[] propertiesData =
msgInner.getPropertiesString() == null ? null : msgInner.getPropertiesString().getBytes(MessageDecoder.CHARSET_UTF8);
final int propertiesLength = propertiesData == null ? 0 : propertiesData.length;
if (propertiesLength > Short.MAX_VALUE) {
log.warn("putMessage message properties length too long. length={}", propertiesData.length);
return new AppendMessageResult(AppendMessageStatus.PROPERTIES_SIZE_EXCEEDED);
}
final byte[] topicData = msgInner.getTopic().getBytes(MessageDecoder.CHARSET_UTF8);
final int topicLength = topicData.length;
final int bodyLength = msgInner.getBody() == null ? 0 : msgInner.getBody().length;
final int msgLen = calMsgLength(msgInner.getSysFlag(), bodyLength, topicLength, propertiesLength);
// Exceeds the maximum message
if (msgLen > this.maxMessageSize) {
CommitLog.log.warn("message size exceeded, msg total size: " + msgLen + ", msg body size: " + bodyLength
+ ", maxMessageSize: " + this.maxMessageSize);
return new AppendMessageResult(AppendMessageStatus.MESSAGE_SIZE_EXCEEDED);
}
// Determines whether there is sufficient free space
if ((msgLen + END_FILE_MIN_BLANK_LENGTH) > maxBlank) {
this.resetByteBuffer(this.msgStoreItemMemory, maxBlank);
// 1 TOTALSIZE
this.msgStoreItemMemory.putInt(maxBlank);
// 2 MAGICCODE
this.msgStoreItemMemory.putInt(CommitLog.BLANK_MAGIC_CODE);
// 3 The remaining space may be any value
// Here the length of the specially set maxBlank
final long beginTimeMills = CommitLog.this.defaultMessageStore.now();
byteBuffer.put(this.msgStoreItemMemory.array(), 0, maxBlank);
return new AppendMessageResult(AppendMessageStatus.END_OF_FILE, wroteOffset, maxBlank, msgId, msgInner.getStoreTimestamp(),
queueOffset, CommitLog.this.defaultMessageStore.now() - beginTimeMills);
}
// 序列化写入数据,写header... body...
// Initialization of storage space
this.resetByteBuffer(msgStoreItemMemory, msgLen);
// 1 TOTALSIZE
this.msgStoreItemMemory.putInt(msgLen);
// 2 MAGICCODE
this.msgStoreItemMemory.putInt(CommitLog.MESSAGE_MAGIC_CODE);
// 3 BODYCRC
this.msgStoreItemMemory.putInt(msgInner.getBodyCRC());
// 4 QUEUEID
this.msgStoreItemMemory.putInt(msgInner.getQueueId());
// 5 FLAG
this.msgStoreItemMemory.putInt(msgInner.getFlag());
// 6 QUEUEOFFSET
this.msgStoreItemMemory.putLong(queueOffset);
// 7 PHYSICALOFFSET
this.msgStoreItemMemory.putLong(fileFromOffset + byteBuffer.position());
// 8 SYSFLAG
this.msgStoreItemMemory.putInt(msgInner.getSysFlag());
// 9 BORNTIMESTAMP
this.msgStoreItemMemory.putLong(msgInner.getBornTimestamp());
// 10 BORNHOST
this.resetByteBuffer(bornHostHolder, bornHostLength);
this.msgStoreItemMemory.put(msgInner.getBornHostBytes(bornHostHolder));
// 11 STORETIMESTAMP
this.msgStoreItemMemory.putLong(msgInner.getStoreTimestamp());
// 12 STOREHOSTADDRESS
this.resetByteBuffer(storeHostHolder, storeHostLength);
this.msgStoreItemMemory.put(msgInner.getStoreHostBytes(storeHostHolder));
// 13 RECONSUMETIMES
this.msgStoreItemMemory.putInt(msgInner.getReconsumeTimes());
// 14 Prepared Transaction Offset
this.msgStoreItemMemory.putLong(msgInner.getPreparedTransactionOffset());
// 15 BODY
this.msgStoreItemMemory.putInt(bodyLength);
if (bodyLength > 0)
this.msgStoreItemMemory.put(msgInner.getBody());
// 16 TOPIC
this.msgStoreItemMemory.put((byte) topicLength);
this.msgStoreItemMemory.put(topicData);
// 17 PROPERTIES
this.msgStoreItemMemory.putShort((short) propertiesLength);
if (propertiesLength > 0)
this.msgStoreItemMemory.put(propertiesData);
final long beginTimeMills = CommitLog.this.defaultMessageStore.now();
// Write messages to the queue buffer
// 将数据写入 ByteBuffer 中,
byteBuffer.put(this.msgStoreItemMemory.array(), 0, msgLen);
AppendMessageResult result = new AppendMessageResult(AppendMessageStatus.PUT_OK, wroteOffset, msgLen, msgId,
msgInner.getStoreTimestamp(), queueOffset, CommitLog.this.defaultMessageStore.now() - beginTimeMills);
switch (tranType) {
case MessageSysFlag.TRANSACTION_PREPARED_TYPE:
case MessageSysFlag.TRANSACTION_ROLLBACK_TYPE:
break;
case MessageSysFlag.TRANSACTION_NOT_TYPE:
case MessageSysFlag.TRANSACTION_COMMIT_TYPE:
// The next update ConsumeQueue information
CommitLog.this.topicQueueTable.put(key, ++queueOffset);
break;
default:
break;
}
return result;
}

以上过程看似复杂,实则只有最后一个bytebuffer.putXxx() 是真正的和mappedFile 是相关的。当然了,还有MappedFile的初始过程,它会先尝试从现有打开的mappFiles中获取最后一个实例,如果mappedFile满了之后,就会尝试创建一个新的mappedFile,  这个过程一般伴随着新的commitLog文件的创建。

mappedFile 的刷盘动作,主要分为同步刷盘和异步刷,底层都是一样的,即调用 flush(),MappedFileChannel.force(),  将pagecache强制刷入到磁盘上。一般地,将数据写入pagecache,基本就能保证不丢失了。但还是有例外情况,比如机器掉电,或者系统bug这种极端情况,还是会导致丢数据哟。

下面大致来看看 mappedFile 同步刷盘过程:

// org.apache.rocketmq.store.CommitLog#handleDiskFlush
public void handleDiskFlush(AppendMessageResult result, PutMessageResult putMessageResult, MessageExt messageExt) {
// Synchronization flush
// 同步刷盘
if (FlushDiskType.SYNC_FLUSH == this.defaultMessageStore.getMessageStoreConfig().getFlushDiskType()) {
final GroupCommitService service = (GroupCommitService) this.flushCommitLogService;
if (messageExt.isWaitStoreMsgOK()) {
// 提交一个刷盘任务到 GroupCommitService, 同步等待结果响应
GroupCommitRequest request = new GroupCommitRequest(result.getWroteOffset() + result.getWroteBytes());
service.putRequest(request);
CompletableFuture<PutMessageStatus> flushOkFuture = request.future();
PutMessageStatus flushStatus = null;
try {
flushStatus = flushOkFuture.get(this.defaultMessageStore.getMessageStoreConfig().getSyncFlushTimeout(),
TimeUnit.MILLISECONDS);
} catch (InterruptedException | ExecutionException | TimeoutException e) {
//flushOK=false;
}
if (flushStatus != PutMessageStatus.PUT_OK) {
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();
}
}
// Asynchronous flush
// 异步刷盘
else {
// 异步刷盘则直接唤醒一个刷盘线程即可
if (!this.defaultMessageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
flushCommitLogService.wakeup();
} else {
commitLogService.wakeup();
}
}
}
// org.apache.rocketmq.store.CommitLog.GroupCommitService#putRequest
// 添加刷盘请求
public synchronized void putRequest(final GroupCommitRequest request) {
synchronized (this.requestsWrite) {
this.requestsWrite.add(request);
}
this.wakeup();
}
// 刷盘线程一直运行
public void run() {
CommitLog.log.info(this.getServiceName() + " service started");
while (!this.isStopped()) {
try {
this.waitForRunning(10);
// 运行真正的刷动作
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");
}
private void doCommit() {
synchronized (this.requestsRead) {
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) {
// 刷盘实现
CommitLog.this.mappedFileQueue.flush(0);
}
}
req.wakeupCustomer(flushOK ? PutMessageStatus.PUT_OK : PutMessageStatus.FLUSH_DISK_TIMEOUT);
}
long storeTimestamp = CommitLog.this.mappedFileQueue.getStoreTimestamp();
if (storeTimestamp > 0) {
CommitLog.this.defaultMessageStore.getStoreCheckpoint().setPhysicMsgTimestamp(storeTimestamp);
}
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);
}
}
}
// org.apache.rocketmq.store.MappedFileQueue#flush
public boolean flush(final int flushLeastPages) {
boolean result = true;
MappedFile mappedFile = this.findMappedFileByOffset(this.flushedWhere, this.flushedWhere == 0);
if (mappedFile != null) {
long tmpTimeStamp = mappedFile.getStoreTimestamp();
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;
}
// org.apache.rocketmq.store.MappedFile#flush
/**
* @return The current flushed position
*/
public int flush(final int flushLeastPages) {
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();
}

最后,来看看mappedFile 的创建和预热过程如何:

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
canSubmitRequests = this.messageStore.getTransientStorePool().availableBufferNums() - this.requestQueue.size();
}
}
AllocateRequest nextReq = new AllocateRequest(nextFilePath, fileSize);
boolean nextPutOK = this.requestTable.putIfAbsent(nextFilePath, nextReq) == null;
if (nextPutOK) {
if (canSubmitRequests <= 0) {
log.warn("[NOTIFYME]TransientStorePool is not enough, so create mapped file error, " +
"RequestQueueSize : {}, StorePoolSize: {}", this.requestQueue.size(), this.messageStore.getTransientStorePool().availableBufferNums());
this.requestTable.remove(nextFilePath);
return null;
}
boolean offerOK = this.requestQueue.offer(nextReq);
if (!offerOK) {
log.warn("never expected here, add a request to preallocate queue failed");
}
canSubmitRequests--;
}
AllocateRequest nextNextReq = new AllocateRequest(nextNextFilePath, fileSize);
// 放入请求表中,会有任务处理
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().availableBufferNums());
this.requestTable.remove(nextNextFilePath);
} else {
// 放入mmap处理队列,后台任务开始处理
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) {
// 同步等待mmap请求处理完成
boolean waitOK = result.getCountDownLatch().await(waitTimeOut, TimeUnit.MILLISECONDS);
if (!waitOK) {
log.warn("create mmap timeout " + result.getFilePath() + " " + result.getFileSize());
return null;
} else {
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;
}
// 任务只干一件事,处理调用mmapOperation
public void run() {
log.info(this.getServiceName() + " service started");
while (!this.isStopped() && this.mmapOperation()) {
}
log.info(this.getServiceName() + " service end");
}
/**
* Only interrupted by the external thread, will return false
*/
private boolean mmapOperation() {
boolean isSuccess = false;
AllocateRequest req = null;
try {
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;
if (messageStore.getMessageStoreConfig().isTransientStorePoolEnable()) {
try {
mappedFile = ServiceLoader.load(MappedFile.class).iterator().next();
// 初始化 mappedFile,实际就是创建commitLog文件
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 {
mappedFile = new MappedFile(req.getFilePath(), req.getFileSize());
}
long elapsedTime = UtilAll.computeElapsedTimeMilliseconds(beginTime);
if (elapsedTime > 10) {
int queueSize = this.requestQueue.size();
log.warn("create mappedFile spent time(ms) " + elapsedTime + " queue size " + queueSize
+ " " + req.getFilePath() + " " + req.getFileSize());
}
// pre write mappedFile
if (mappedFile.getFileSize() >= this.messageStore.getMessageStoreConfig()
.getMappedFileSizeCommitLog()
&&
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;
}
// store.MappedFile.init()
public void init(final String fileName, final int fileSize,
final TransientStorePool transientStorePool) throws IOException {
init(fileName, fileSize);
this.writeBuffer = transientStorePool.borrowBuffer();
this.transientStorePool = transientStorePool;
}
private void init(final String fileName, final int fileSize) throws IOException {
this.fileName = fileName;
this.fileSize = fileSize;
this.file = new File(fileName);
this.fileFromOffset = Long.parseLong(this.file.getName());
boolean ok = false;
ensureDirOK(this.file.getParent());
try {
// 最核心的创建mmap的地方
// 创建 fileChannel
// 创建 mappedByteBuffer, 后续直接使用
this.fileChannel = new RandomAccessFile(this.file, "rw").getChannel();
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("Failed to create file " + this.fileName, e);
throw e;
} catch (IOException e) {
log.error("Failed to map file " + this.fileName, e);
throw e;
} finally {
if (!ok && this.fileChannel != null) {
this.fileChannel.close();
}
}
}

预热:

// org.apache.rocketmq.store.MappedFile#warmMappedFile
public void warmMappedFile(FlushDiskType type, int pages) {
long beginTime = System.currentTimeMillis();
ByteBuffer byteBuffer = this.mappedByteBuffer.slice();
int flush = 0;
long time = System.currentTimeMillis();
for (int i = 0, j = 0; i < this.fileSize; i += MappedFile.OS_PAGE_SIZE, j++) {
byteBuffer.put(i, (byte) 0);
// force flush when flush disk type is sync
if (type == FlushDiskType.SYNC_FLUSH) {
if ((i / OS_PAGE_SIZE) - (flush / OS_PAGE_SIZE) >= pages) {
flush = i;
mappedByteBuffer.force();
}
}
// prevent gc
if (j % 1000 == 0) {
log.info("j={}, costTime={}", j, System.currentTimeMillis() - time);
time = System.currentTimeMillis();
try {
Thread.sleep(0);
} catch (InterruptedException e) {
log.error("Interrupted", e);
}
}
}
// force flush when prepare load finished
if (type == FlushDiskType.SYNC_FLUSH) {
log.info("mapped file warm-up done, force to disk, mappedFile={}, costTime={}",
this.getFileName(), System.currentTimeMillis() - beginTime);
mappedByteBuffer.force();
}
log.info("mapped file warm-up done. mappedFile={}, costTime={}", this.getFileName(),
System.currentTimeMillis() - beginTime);
this.mlock();
}

如此,整个rocketmq对mappedfile的使用过程就厘清了。

5. mappedFile 压测性能几何

使用jmh 压测下。

@State(Scope.Benchmark)
public class MmapFileBenchmarkTest {
public static void main(String[] args) throws RunnerException {
Options opt = new OptionsBuilder()
.include(MmapFileBenchmarkTest.class.getSimpleName())
//                .include(BenchMarkUsage.class.getSimpleName()+".*measureThroughput*")
// 预热3轮
.warmupIterations(3)
// 度量5轮
.measurementIterations(5)
.forks(1)
.build();
new Runner(opt).run();
}
private FileChannel fileChannel;
private MappedByteBuffer mappedByteBuffer;
private OutputStream outputStream;
private int maxWriteLines = 100_0000;
private int fileSize = 102400000;
@Setup
@Before
public void setup() throws IOException {
File file1 = new File("/tmp/t_mappedFileTest.txt");
this.fileChannel = new RandomAccessFile(file1, "rw").getChannel();
this.mappedByteBuffer = this.fileChannel.map(FileChannel.MapMode.READ_WRITE,
0, 1024000000);
// 忽略预热
//        warmMappedFile();
outputStream = FileUtils.openOutputStream(new File("/tmp/t_normalFileTest.txt"));
}
private void warmMappedFile() {
long beginTime = System.currentTimeMillis();
ByteBuffer byteBuffer = this.mappedByteBuffer.slice();
int flush = 0;
long time = System.currentTimeMillis();
for (int i = 0, j = 0; i < this.fileSize; i += 4096, j++) {
byteBuffer.put(i, (byte) 0);
// prevent gc
if (j % 1000 == 0) {
logInfo("j=%s, costTime=%d", j, System.currentTimeMillis() - time);
time = System.currentTimeMillis();
try {
Thread.sleep(0);
} catch (InterruptedException e) {
logInfo("Interrupted, %s", e);
}
}
}
// force flush when prepare load finished
mappedByteBuffer.force();
//        this.mlock();
}
private void logInfo(String message, Object... args) {
System.out.println(String.format(message, args));
}
@Benchmark
@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.SECONDS)
@Test
public void testAppendMappedFile() throws IOException {
for (int i = 0; i < maxWriteLines; i++ ) {
mappedByteBuffer.put("abc1234567\n".getBytes());
}
mappedByteBuffer.flip();
}
@Benchmark
@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.SECONDS)
@Test
public void testAppendNormalFile() throws IOException {
for (int i = 0; i < maxWriteLines; i++ ) {
outputStream.write("abc1234567\n".getBytes());
}
outputStream.flush();
}
}

测试结果如下:

# Run progress: 0.00% complete, ETA 00:00:16
# Fork: 1 of 1
# Warmup Iteration   1: 14.808 ops/s
# Warmup Iteration   2: 16.170 ops/s
# Warmup Iteration   3: 18.633 ops/s
Iteration   1: 15.692 ops/s
Iteration   2: 17.273 ops/s
Iteration   3: 18.145 ops/s
Iteration   4: 18.356 ops/s
Iteration   5: 18.868 ops/s
Result "MmapFileBenchmarkTest.testAppendMappedFile":
17.667 ±(99.9%) 4.795 ops/s [Average]
(min, avg, max) = (15.692, 17.667, 18.868), stdev = 1.245
CI (99.9%): [12.871, 22.462] (assumes normal distribution)
# JMH version: 1.19
# VM version: JDK 1.8.0_121, VM 25.121-b13
# Warmup: 3 iterations, 1 s each
# Measurement: 5 iterations, 1 s each
# Timeout: 10 min per iteration
# Threads: 1 thread, will synchronize iterations
# Benchmark mode: Throughput, ops/time
# Benchmark: MmapFileBenchmarkTest.testAppendNormalFile
# Run progress: 50.00% complete, ETA 00:00:09
# Fork: 1 of 1
# Warmup Iteration   1: 0.443 ops/s
# Warmup Iteration   2: 0.456 ops/s
# Warmup Iteration   3: 0.438 ops/s
Iteration   1: 0.406 ops/s
Iteration   2: 0.430 ops/s
Iteration   3: 0.408 ops/s
Iteration   4: 0.399 ops/s
Iteration   5: 0.410 ops/s
Result "MmapFileBenchmarkTest.testAppendNormalFile":
0.411 ±(99.9%) 0.044 ops/s [Average]
(min, avg, max) = (0.399, 0.411, 0.430), stdev = 0.011
CI (99.9%): [0.367, 0.454] (assumes normal distribution)
# Run complete. Total time: 00:00:29
Benchmark                                    Mode  Cnt   Score   Error  Units
MmapFileBenchmarkTest.testAppendMappedFile  thrpt    5  17.667 ± 4.795  ops/s
MmapFileBenchmarkTest.testAppendNormalFile  thrpt    5   0.411 ± 0.044  ops/s

结论粗糙,仅供参考!

等你归去来
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