分布式消息队列 RocketMQ源码解析:事务消息
2018-01-16 00:00
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摘要: 原创出处 http://www.iocoder.cn/RocketMQ/message-transaction/ 「芋道源码」欢迎转载,保留摘要,谢谢!本文主要基于 RocketMQ 4.0.x 正式版1. 概述
2. 事务消息发送
2.1 Producer 发送事务消息
2.2 Broker 处理结束事务请求
2.3 Broker 生成 ConsumeQueue
3. 事务消息回查
3.1 Broker 发起【事务消息回查】
3.1.1 官方V3.1.4:基于文件系统
3.1.1.1 存储消息到 CommitLog
3.1.1.2 写【事务消息】状态存储(TranStateTable)
3.1.1.3 【事务消息】回查
3.1.1.4 初始化【事务消息】状态存储(TranStateTable)
3.1.1.5 补充
3.1.2 官方V4.0.0:基于数据库
3.2 Producer 接收【事务消息回查】
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实现代码如下:
我们来看看两种情况下是怎么实现的。
TranStateTable :【事务消息】状态存储。基于
简单手绘逻辑图如下?:
核心代码如下:
?处理【Commit / Rollback消息】时,更新 【事务消息】状态存储(
?每次写操作【事务消息】状态存储(
核心代码如下:
实现代码如下:
核心代码如下:
RocketMQ 这种实现事务方式,没有通过 KV 存储做,而是通过 Offset 方式,存在一个显著缺陷,即通过 Offset 更改数据,会令系统的脏页过多,需要特别关注。
另外,数据库本身保证了数据存储的可靠性,无需
核心代码如下:
2. 事务消息发送
2.1 Producer 发送事务消息
2.2 Broker 处理结束事务请求
2.3 Broker 生成 ConsumeQueue
3. 事务消息回查
3.1 Broker 发起【事务消息回查】
3.1.1 官方V3.1.4:基于文件系统
3.1.1.1 存储消息到 CommitLog
3.1.1.2 写【事务消息】状态存储(TranStateTable)
3.1.1.3 【事务消息】回查
3.1.1.4 初始化【事务消息】状态存储(TranStateTable)
3.1.1.5 补充
3.1.2 官方V4.0.0:基于数据库
3.2 Producer 接收【事务消息回查】
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1. 概述
必须必须必须 前置阅读内容:《事务消息(阿里云)》2. 事务消息发送
2.1 Producer 发送事务消息
活动图如下(结合核心代码理解):
实现代码如下:
1: // ⬇️⬇️⬇️【DefaultMQProducerImpl.java】 2: /** 3: * 发送事务消息 4: * 5: * @param msg 消息 6: * @param tranExecuter 【本地事务】执行器 7: * @param arg 【本地事务】执行器参数 8: * @return 事务发送结果 9: * @throws MQClientException 当 Client 发生异常时 10: */ 11: public TransactionSendResult sendMessageInTransaction(final Message msg, final LocalTransactionExecuter tranExecuter, final Object arg) 12: throws MQClientException { 13: if (null == tranExecuter) { 14: throw new MQClientException("tranExecutor is null", null); 15: } 16: Validators.checkMessage(msg, this.defaultMQProducer); 17: 18: // 发送【Half消息】 19: SendResult sendResult; 20: MessageAccessor.putProperty(msg, MessageConst.PROPERTY_TRANSACTION_PREPARED, "true"); 21: MessageAccessor.putProperty(msg, MessageConst.PROPERTY_PRODUCER_GROUP, this.defaultMQProducer.getProducerGroup()); 22: try { 23: sendResult = this.send(msg); 24: } catch (Exception e) { 25: throw new MQClientException("send message Exception", e); 26: } 27: 28: // 处理发送【Half消息】结果 29: LocalTransactionState localTransactionState = LocalTransactionState.UNKNOW; 30: Throwable localException = null; 31: switch (sendResult.getSendStatus()) { 32: // 发送【Half消息】成功,执行【本地事务】逻辑 33: case SEND_OK: { 34: try { 35: if (sendResult.getTransactionId() != null) { // 事务编号。目前开源版本暂时没用到,猜想ONS在使用。 36: msg.putUserProperty("__transactionId__", sendResult.getTransactionId()); 37: } 38: 39: // 执行【本地事务】逻辑 40: localTransactionState = tranExecuter.executeLocalTransactionBranch(msg, arg); 41: if (null == localTransactionState) { 42: localTransactionState = LocalTransactionState.UNKNOW; 43: } 44: 45: if (localTransactionState != LocalTransactionState.COMMIT_MESSAGE) { 46: log.info("executeLocalTransactionBranch return {}", localTransactionState); 47: log.info(msg.toString()); 48: } 49: } catch (Throwable e) { 50: log.info("executeLocalTransactionBranch exception", e); 51: log.info(msg.toString()); 52: localException = e; 53: } 54: } 55: break; 56: // 发送【Half消息】失败,标记【本地事务】状态为回滚 57: case FLUSH_DISK_TIMEOUT: 58: case FLUSH_SLAVE_TIMEOUT: 59: case SLAVE_NOT_AVAILABLE: 60: localTransactionState = LocalTransactionState.ROLLBACK_MESSAGE; 61: break; 62: default: 63: break; 64: } 65: 66: // 结束事务:提交消息 COMMIT / ROLLBACK 67: try { 68: this.endTransaction(sendResult, localTransactionState, localException); 69: } catch (Exception e) { 70: log.warn("local transaction execute " + localTransactionState + ", but end broker transaction failed", e); 71: } 72: 73: // 返回【事务发送结果】 74: TransactionSendResult transactionSendResult = new TransactionSendResult(); 75: transactionSendResult.setSendStatus(sendResult.getSendStatus()); 76: transactionSendResult.setMessageQueue(sendResult.getMessageQueue()); 77: transactionSendResult.setMsgId(sendResult.getMsgId()); 78: transactionSendResult.setQueueOffset(sendResult.getQueueOffset()); 79: transactionSendResult.setTransactionId(sendResult.getTransactionId()); 80: transactionSendResult.setLocalTransactionState(localTransactionState); 81: return transactionSendResult; 82: } 83: 84: /** 85: * 结束事务:提交消息 COMMIT / ROLLBACK 86: * 87: * @param sendResult 发送【Half消息】结果 88: * @param localTransactionState 【本地事务】状态 89: * @param localException 执行【本地事务】逻辑产生的异常 90: * @throws RemotingException 当远程调用发生异常时 91: * @throws MQBrokerException 当 Broker 发生异常时 92: * @throws InterruptedException 当线程中断时 93: * @throws UnknownHostException 当解码消息编号失败是 94: */ 95: public void endTransaction(// 96: final SendResult sendResult, // 97: final LocalTransactionState localTransactionState, // 98: final Throwable localException) throws RemotingException, MQBrokerException, InterruptedException, UnknownHostException { 99: // 解码消息编号 100: final MessageId id; 101: if (sendResult.getOffsetMsgId() != null) { 102: id = MessageDecoder.decodeMessageId(sendResult.getOffsetMsgId()); 103: } else { 104: id = MessageDecoder.decodeMessageId(sendResult.getMsgId()); 105: } 106: 107: // 创建请求 108: String transactionId = sendResult.getTransactionId(); 109: final String brokerAddr = this.mQClientFactory.findBrokerAddressInPublish(sendResult.getMessageQueue().getBrokerName()); 110: EndTransactionRequestHeader requestHeader = new EndTransactionRequestHeader(); 111: requestHeader.setTransactionId(transactionId); 112: requestHeader.setCommitLogOffset(id.getOffset()); 113: switch (localTransactionState) { 114: case COMMIT_MESSAGE: 115: requestHeader.setCommitOrRollback(MessageSysFlag.TRANSACTION_COMMIT_TYPE); 116: break; 117: case ROLLBACK_MESSAGE: 118: requestHeader.setCommitOrRollback(MessageSysFlag.TRANSACTION_ROLLBACK_TYPE); 119: break; 120: case UNKNOW: 121: requestHeader.setCommitOrRollback(MessageSysFlag.TRANSACTION_NOT_TYPE); 122: break; 123: default: 124: break; 125: } 126: requestHeader.setProducerGroup(this.defaultMQProducer.getProducerGroup()); 127: requestHeader.setTranStateTableOffset(sendResult.getQueueOffset()); 128: requestHeader.setMsgId(sendResult.getMsgId()); 129: String remark = localException != null ? ("executeLocalTransactionBranch exception: " + localException.toString()) : null; 130: 131: // 提交消息 COMMIT / ROLLBACK。!!!通信方式为:Oneway!!! 132: this.mQClientFactory.getMQClientAPIImpl().endTransactionOneway(brokerAddr, requestHeader, remark, this.defaultMQProducer.getSendMsgTimeout()); 133: }
2.2 Broker 处理结束事务请求
? 查询请求的消息,进行提交 / 回滚。实现代码如下:1: // ⬇️⬇️⬇️【EndTransactionProcessor.java】 2: public RemotingCommand processRequest(ChannelHandlerContext ctx, RemotingCommand request) throws RemotingCommandException { 3: final RemotingCommand response = RemotingCommand.createResponseCommand(null); 4: final EndTransactionRequestHeader requestHeader = (EndTransactionRequestHeader) request.decodeCommandCustomHeader(EndTransactionRequestHeader.class); 5: 6: // 省略代码 =》打印日志(只处理 COMMIT / ROLLBACK) 7: 8: // 查询提交的消息 9: final MessageExt msgExt = this.brokerController.getMessageStore().lookMessageByOffset(requestHeader.getCommitLogOffset()); 10: if (msgExt != null) { 11: // 省略代码 =》校验消息 12: 13: // 生成消息 14: MessageExtBrokerInner msgInner = this.endMessageTransaction(msgExt); 15: msgInner.setSysFlag(MessageSysFlag.resetTransactionValue(msgInner.getSysFlag(), requestHeader.getCommitOrRollback())); 16: msgInner.setQueueOffset(requestHeader.getTranStateTableOffset()); 17: msgInner.setPreparedTransactionOffset(requestHeader.getCommitLogOffset()); 18: msgInner.setStoreTimestamp(msgExt.getStoreTimestamp()); 19: if (MessageSysFlag.TRANSACTION_ROLLBACK_TYPE == requestHeader.getCommitOrRollback()) { 20: msgInner.setBody(null); 21: } 22: 23: // 存储生成消息 24: final MessageStore messageStore = this.brokerController.getMessageStore(); 25: final PutMessageResult putMessageResult = messageStore.putMessage(msgInner); 26: 27: // 处理存储结果 28: if (putMessageResult != null) { 29: switch (putMessageResult.getPutMessageStatus()) { 30: // Success 31: case PUT_OK: 32: case FLUSH_DISK_TIMEOUT: 33: case FLUSH_SLAVE_TIMEOUT: 34: case SLAVE_NOT_AVAILABLE: 35: response.setCode(ResponseCode.SUCCESS); 36: response.setRemark(null); 37: break; 38: // Failed 39: case CREATE_MAPEDFILE_FAILED: 40: response.setCode(ResponseCode.SYSTEM_ERROR); 41: response.setRemark("create maped file failed."); 42: break; 43: case MESSAGE_ILLEGAL: 44: case PROPERTIES_SIZE_EXCEEDED: 45: response.setCode(ResponseCode.MESSAGE_ILLEGAL); 46: response.setRemark("the message is illegal, maybe msg body or properties length not matched. msg body length limit 128k, msg properties length limit 32k."); 47: break; 48: case SERVICE_NOT_AVAILABLE: 49: response.setCode(ResponseCode.SERVICE_NOT_AVAILABLE); 50: response.setRemark("service not available now."); 51: break; 52: case OS_PAGECACHE_BUSY: 53: response.setCode(ResponseCode.SYSTEM_ERROR); 54: response.setRemark("OS page cache busy, please try another machine"); 55: break; 56: case UNKNOWN_ERROR: 57: response.setCode(ResponseCode.SYSTEM_ERROR); 58: response.setRemark("UNKNOWN_ERROR"); 59: break; 60: default: 61: response.setCode(ResponseCode.SYSTEM_ERROR); 62: response.setRemark("UNKNOWN_ERROR DEFAULT"); 63: break; 64: } 65: 66: return response; 67: } else { 68: response.setCode(ResponseCode.SYSTEM_ERROR); 69: response.setRemark("store putMessage return null"); 70: } 71: } else { 72: response.setCode(ResponseCode.SYSTEM_ERROR); 73: response.setRemark("find prepared transaction message failed"); 74: return response; 75: } 76: 77: return response; 78: }
2.3 Broker 生成 ConsumeQueue
? 事务消息,提交(COMMIT)后才生成
ConsumeQueue。
1: // ⬇️⬇️⬇️【DefaultMessageStore.java】 2: public void doDispatch(DispatchRequest req) { 3: // 非事务消息 或 事务提交消息 建立 消息位置信息 到 ConsumeQueue 4: final int tranType = MessageSysFlag.getTransactionValue(req.getSysFlag()); 5: switch (tranType) { 6: case MessageSysFlag.TRANSACTION_NOT_TYPE: // 非事务消息 7: case MessageSysFlag.TRANSACTION_COMMIT_TYPE: // 事务消息COMMIT 8: DefaultMessageStore.this.putMessagePositionInfo(req.getTopic(), req.getQueueId(), req.getCommitLogOffset(), req.getMsgSize(), 9: req.getTagsCode(), req.getStoreTimestamp(), req.getConsumeQueueOffset()); 10: break; 11: case MessageSysFlag.TRANSACTION_PREPARED_TYPE: // 事务消息PREPARED 12: case MessageSysFlag.TRANSACTION_ROLLBACK_TYPE: // 事务消息ROLLBACK 13: break; 14: } 15: // 省略代码 =》 建立 索引信息 到 IndexFile 16: }
3. 事务消息回查
【事务消息回查】功能曾经开源过,目前(V4.0.0)暂未开源。如下是该功能的开源情况:版本 | 【事务消息回查】 | |
---|---|---|
官方V3.0.4 ~ V3.1.4 | 基于 文件系统 实现 | 已开源 |
官方V3.1.5 ~ V4.0.0 | 基于 数据库 实现 | 未完全开源 |
3.1 Broker 发起【事务消息回查】
3.1.1 官方V3.1.4:基于文件系统
仓库地址:https://github.com/YunaiV/rocketmq-3.1.9/tree/release_3.1.4相较于普通消息,【事务消息】多依赖如下三个组件:TransactionStateService :事务状态服务,负责对【事务消息】进行管理,包括存储与更新事务消息状态、回查事务消息状态等等。TranStateTable :【事务消息】状态存储。基于
MappedFileQueue实现,默认存储路径为
~/store/transaction/statetable,每条【事务消息】状态存储结构如下:
第几位 | 字段 | 说明 | 数据类型 | 字节数 |
---|---|---|---|---|
1 | offset | CommitLog 物理存储位置 | Long | 8 |
2 | size | 消息长度 | Int | 4 |
3 | timestamp | 消息存储时间,单位:秒 | Int | 4 |
4 | producerGroupHash | producerGroup 求 HashCode | Int | 4 |
5 | state | 事务状态 | Int | 4 |
TranRedoLog :TranStateTable重放日志,每次写操作 TranStateTable记录重放日志。当 Broker异常关闭时,使用 TranRedoLog恢复 TranStateTable。基于 ConsumeQueue实现, Topic为 TRANSACTION_REDOLOG_TOPIC_XXXX,默认存储路径为 ~/store/transaction/redolog。 | ||||
3.1.1.1 存储消息到 CommitLog
?存储【half消息】到CommitLog时,消息队列位置(
queueOffset)使用
TranStateTable最大物理位置(可写入物理位置)。这样,消息可以索引到自己对应的
TranStateTable的位置和记录。
核心代码如下:
1: // ⬇️⬇️⬇️【DefaultAppendMessageCallback.java】 2: class DefaultAppendMessageCallback implements AppendMessageCallback { 3: public AppendMessageResult doAppend(final long fileFromOffset, final ByteBuffer byteBuffer, final int maxBlank, final Object msg) { 4: // ...省略代码 5: 6: // 事务消息需要特殊处理 7: final int tranType = MessageSysFlag.getTransactionValue(msgInner.getSysFlag()); 8: switch (tranType) { 9: case MessageSysFlag.TransactionPreparedType: // 消息队列位置(queueOffset)使用 TranStateTable 最大物理位置(可写入物理位置) 10: queueOffset = CommitLog.this.defaultMessageStore.getTransactionStateService().getTranStateTableOffset().get(); 11: break; 12: case MessageSysFlag.TransactionRollbackType: 13: queueOffset = msgInner.getQueueOffset(); 14: break; 15: case MessageSysFlag.TransactionNotType: 16: case MessageSysFlag.TransactionCommitType: 17: default: 18: break; 19: } 20: 21: // ...省略代码 22: 23: switch (tranType) { 24: case MessageSysFlag.TransactionPreparedType: 25: // 更新 TranStateTable 最大物理位置(可写入物理位置) 26: CommitLog.this.defaultMessageStore.getTransactionStateService().getTranStateTableOffset().incrementAndGet(); 27: break; 28: case MessageSysFlag.TransactionRollbackType: 29: break; 30: case MessageSysFlag.TransactionNotType: 31: case MessageSysFlag.TransactionCommitType: 32: // 更新下一次的ConsumeQueue信息 33: CommitLog.this.topicQueueTable.put(key, ++queueOffset); 34: break; 35: default: 36: break; 37: } 38: 39: // 返回结果 40: return result; 41: } 42: }
3.1.1.2 写【事务消息】状态存储(TranStateTable)
?处理【Half消息】时,新增【事务消息】状态存储(TranStateTable)。
?处理【Commit / Rollback消息】时,更新 【事务消息】状态存储(
TranStateTable) COMMIT / ROLLBACK。
?每次写操作【事务消息】状态存储(
TranStateTable),记录重放日志(
TranRedoLog)。
核心代码如下:
1: // ⬇️⬇️⬇️【DispatchMessageService.java】 2: private void doDispatch() { 3: if (!this.requestsRead.isEmpty()) { 4: for (DispatchRequest req : this.requestsRead) { 5: 6: // ...省略代码 7: 8: // 2、写【事务消息】状态存储(TranStateTable) 9: if (req.getProducerGroup() != null) { 10: switch (tranType) { 11: case MessageSysFlag.TransactionNotType: 12: break; 13: case MessageSysFlag.TransactionPreparedType: 14: // 新增 【事务消息】状态存储(TranStateTable) 15: DefaultMessageStore.this.getTransactionStateService().appendPreparedTransaction( 16: req.getCommitLogOffset(), req.getMsgSize(), (int) (req.getStoreTimestamp() / 1000), req.getProducerGroup().hashCode()); 17: break; 18: case MessageSysFlag.TransactionCommitType: 19: case MessageSysFlag.TransactionRollbackType: 20: // 更新 【事务消息】状态存储(TranStateTable) COMMIT / ROLLBACK 21: DefaultMessageStore.this.getTransactionStateService().updateTransactionState( 22: req.getTranStateTableOffset(), req.getPreparedTransactionOffset(), req.getProducerGroup().hashCode(), tranType); 23: break; 24: } 25: } 26: // 3、记录 TranRedoLog 27: switch (tranType) { 28: case MessageSysFlag.TransactionNotType: 29: break; 30: case MessageSysFlag.TransactionPreparedType: 31: // 记录 TranRedoLog 32: DefaultMessageStore.this.getTransactionStateService().getTranRedoLog().putMessagePostionInfoWrapper( 33: req.getCommitLogOffset(), req.getMsgSize(), TransactionStateService.PreparedMessageTagsCode, 34: req.getStoreTimestamp(), 0L); 35: break; 36: case MessageSysFlag.TransactionCommitType: 37: case MessageSysFlag.TransactionRollbackType: 38: // 记录 TranRedoLog 39: DefaultMessageStore.this.getTransactionStateService().getTranRedoLog().putMessagePostionInfoWrapper( 40: req.getCommitLogOffset(), req.getMsgSize(), req.getPreparedTransactionOffset(), 41: req.getStoreTimestamp(), 0L); 42: break; 43: } 44: } 45: 46: // ...省略代码 47: } 48: } 49: // ⬇️⬇️⬇️【TransactionStateService.java】 50: /** 51: * 新增事务状态 52: * 53: * @param clOffset commitLog 物理位置 54: * @param size 消息长度 55: * @param timestamp 消息存储时间 56: * @param groupHashCode groupHashCode 57: * @return 是否成功 58: */ 59: public boolean appendPreparedTransaction(// 60: final long clOffset,// 61: final int size,// 62: final int timestamp,// 63: final int groupHashCode// 64: ) { 65: MapedFile mapedFile = this.tranStateTable.getLastMapedFile(); 66: if (null == mapedFile) { 67: log.error("appendPreparedTransaction: create mapedfile error."); 68: return false; 69: } 70: 71: // 首次创建,加入定时任务中 72: if (0 == mapedFile.getWrotePostion()) { 73: this.addTimerTask(mapedFile); 74: } 75: 76: this.byteBufferAppend.position(0); 77: this.byteBufferAppend.limit(TSStoreUnitSize); 78: 79: // Commit Log Offset 80: this.byteBufferAppend.putLong(clOffset); 81: // Message Size 82: this.byteBufferAppend.putInt(size); 83: // Timestamp 84: this.byteBufferAppend.putInt(timestamp); 85: // Producer Group Hashcode 86: this.byteBufferAppend.putInt(groupHashCode); 87: // Transaction State 88: this.byteBufferAppend.putInt(MessageSysFlag.TransactionPreparedType); 89: 90: return mapedFile.appendMessage(this.byteBufferAppend.array()); 91: } 92: 93: /** 94: * 更新事务状态 95: * 96: * @param tsOffset tranStateTable 物理位置 97: * @param clOffset commitLog 物理位置 98: * @param groupHashCode groupHashCode 99: * @param state 事务状态 100: * @return 是否成功 101: */ 102: public boolean updateTransactionState( 103: final long tsOffset, 104: final long clOffset, 105: final int groupHashCode, 106: final int state) { 107: SelectMapedBufferResult selectMapedBufferResult = this.findTransactionBuffer(tsOffset); 108: if (selectMapedBufferResult != null) { 109: try { 110: 111: // ....省略代码:校验是否能够更新 112: 113: // 更新事务状态 114: selectMapedBufferResult.getByteBuffer().putInt(TS_STATE_POS, state); 115: } 116: catch (Exception e) { 117: log.error("updateTransactionState exception", e); 118: } 119: finally { 120: selectMapedBufferResult.release(); 121: } 122: } 123: 124: return false; 125: }
3.1.1.3 【事务消息】回查
?TranStateTable每个
MappedFile都对应一个
Timer。
Timer固定周期(默认:60s)遍历
MappedFile,查找【half消息】,向
Producer发起【事务消息】回查请求。【事务消息】回查结果的逻辑不在此处进行,在 CommitLog dispatch时执行。
实现代码如下:
1: // ⬇️⬇️⬇️【TransactionStateService.java】 2: /** 3: * 初始化定时任务 4: */ 5: private void initTimerTask() { 6: // 7: final List<MapedFile> mapedFiles = this.tranStateTable.getMapedFiles(); 8: for (MapedFile mf : mapedFiles) { 9: this.addTimerTask(mf); 10: } 11: } 12: 13: /** 14: * 每个文件初始化定时任务 15: * @param mf 文件 16: */ 17: private void addTimerTask(final MapedFile mf) { 18: this.timer.scheduleAtFixedRate(new TimerTask() { 19: private final MapedFile mapedFile = mf; 20: private final TransactionCheckExecuter transactionCheckExecuter = TransactionStateService.this.defaultMessageStore.getTransactionCheckExecuter(); 21: private final long checkTransactionMessageAtleastInterval = TransactionStateService.this.defaultMessageStore.getMessageStoreConfig() 22: .getCheckTransactionMessageAtleastInterval(); 23: private final boolean slave = TransactionStateService.this.defaultMessageStore.getMessageStoreConfig().getBrokerRole() == BrokerRole.SLAVE; 24: 25: @Override 26: public void run() { 27: // Slave不需要回查事务状态 28: if (slave) { 29: return; 30: } 31: // Check功能是否开启 32: if (!TransactionStateService.this.defaultMessageStore.getMessageStoreConfig() 33: .isCheckTransactionMessageEnable()) { 34: return; 35: } 36: 37: try { 38: SelectMapedBufferResult selectMapedBufferResult = mapedFile.selectMapedBuffer(0); 39: if (selectMapedBufferResult != null) { 40: long preparedMessageCountInThisMapedFile = 0; // 回查的【half消息】数量 41: int i = 0; 42: try { 43: // 循环每条【事务消息】状态,对【half消息】进行回查 44: for (; i < selectMapedBufferResult.getSize(); i += TSStoreUnitSize) { 45: selectMapedBufferResult.getByteBuffer().position(i); 46: 47: // Commit Log Offset 48: long clOffset = selectMapedBufferResult.getByteBuffer().getLong(); 49: // Message Size 50: int msgSize = selectMapedBufferResult.getByteBuffer().getInt(); 51: // Timestamp 52: int timestamp = selectMapedBufferResult.getByteBuffer().getInt(); 53: // Producer Group Hashcode 54: int groupHashCode = selectMapedBufferResult.getByteBuffer().getInt(); 55: // Transaction State 56: int tranType = selectMapedBufferResult.getByteBuffer().getInt(); 57: 58: // 已经提交或者回滚的消息跳过 59: if (tranType != MessageSysFlag.TransactionPreparedType) { 60: continue; 61: } 62: 63: // 遇到时间不符合最小轮询间隔,终止 64: long timestampLong = timestamp * 1000; 65: long diff = System.currentTimeMillis() - timestampLong; 66: if (diff < checkTransactionMessageAtleastInterval) { 67: break; 68: } 69: 70: preparedMessageCountInThisMapedFile++; 71: 72: // 回查Producer 73: try { 74: this.transactionCheckExecuter.gotoCheck(groupHashCode, getTranStateOffset(i), clOffset, msgSize); 75: } catch (Exception e) { 76: tranlog.warn("gotoCheck Exception", e); 77: } 78: } 79: 80: // 无回查的【half消息】数量,且遍历完,则终止定时任务 81: if (0 == preparedMessageCountInThisMapedFile // 82: && i == mapedFile.getFileSize()) { 83: tranlog.info("remove the transaction timer task, because no prepared message in this mapedfile[{}]", mapedFile.getFileName()); 84: this.cancel(); 85: } 86: } finally { 87: selectMapedBufferResult.release(); 88: } 89: 90: tranlog.info("the transaction timer task execute over in this period, {} Prepared Message: {} Check Progress: {}/{}", mapedFile.getFileName(),// 91: preparedMessageCountInThisMapedFile, i / TSStoreUnitSize, mapedFile.getFileSize() / TSStoreUnitSize); 92: } else if (mapedFile.isFull()) { 93: tranlog.info("the mapedfile[{}] maybe deleted, cancel check transaction timer task", mapedFile.getFileName()); 94: this.cancel(); 95: return; 96: } 97: } catch (Exception e) { 98: log.error("check transaction timer task Exception", e); 99: } 100: } 101: 102: 103: private long getTranStateOffset(final long currentIndex) { 104: long offset = (this.mapedFile.getFileFromOffset() + currentIndex) / TransactionStateService.TSStoreUnitSize; 105: return offset; 106: } 107: }, 1000 * 60, this.defaultMessageStore.getMessageStoreConfig().getCheckTransactionMessageTimerInterval()); 108: } 109: 110: // 【DefaultTransactionCheckExecuter.java】 111: @Override 112: public void gotoCheck(int producerGroupHashCode, long tranStateTableOffset, long commitLogOffset, 113: int msgSize) { 114: // 第一步、查询Producer 115: final ClientChannelInfo clientChannelInfo = this.brokerController.getProducerManager().pickProducerChannelRandomly(producerGroupHashCode); 116: if (null == clientChannelInfo) { 117: log.warn("check a producer transaction state, but not find any channel of this group[{}]", producerGroupHashCode); 118: return; 119: } 120: 121: // 第二步、查询消息 122: SelectMapedBufferResult selectMapedBufferResult = this.brokerController.getMessageStore().selectOneMessageByOffset(commitLogOffset, msgSize); 123: if (null == selectMapedBufferResult) { 124: log.warn("check a producer transaction state, but not find message by commitLogOffset: {}, msgSize: ", commitLogOffset, msgSize); 125: return; 126: } 127: 128: // 第三步、向Producer发起请求 129: final CheckTransactionStateRequestHeader requestHeader = new CheckTransactionStateRequestHeader(); 130: requestHeader.setCommitLogOffset(commitLogOffset); 131: requestHeader.setTranStateTableOffset(tranStateTableOffset); 132: this.brokerController.getBroker2Client().checkProducerTransactionState(clientChannelInfo.getChannel(), requestHeader, selectMapedBufferResult); 133: }
3.1.1.4 初始化【事务消息】状态存储(TranStateTable)
?根据最后 Broker 关闭是否正常,会有不同的初始化方式。核心代码如下:
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3.1.1.5 补充
为什么 V3.1.5 开始,使用 数据库 实现【事务状态】的存储?如下是来自官方文档的说明,可能是一部分原因:RocketMQ 这种实现事务方式,没有通过 KV 存储做,而是通过 Offset 方式,存在一个显著缺陷,即通过 Offset 更改数据,会令系统的脏页过多,需要特别关注。
3.1.2 官方V4.0.0:基于数据库
仓库地址:https://github.com/apache/incubator-rocketmq官方V4.0.0 暂时未完全开源【事务消息回查】功能,So 我们需要进行一些猜想,可能不一定正确?。?我们来对比【官方V3.1.4:基于文件】的实现。TransactionRecord :记录每条【事务消息】。类似TranStateTable。
TranStateTable | TransactionRecord | |
---|---|---|
offset | offset | |
producerGroupHash | producerGroup | |
size | 无 | 非必须字段:【事务消息】回查时,使用 offset 读取 CommitLog 获得。 |
timestamp | 无 | 非必须字段:【事务消息】回查时,使用 offset 读取 CommitLog 获得。 |
state | 无 | 非必须字段: 事务开始,增加记录;事务结束,删除记录。 |
TranRedoLog。简单手绘逻辑图如下?:
3.2 Producer 接收【事务消息回查】
顺序图如下:核心代码如下:
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