tcc分布式事務(wù)框架體系解析
前言碎語
樓主之前推薦過2pc的分布式事務(wù)框架LCN。今天來詳細(xì)聊聊TCC事務(wù)協(xié)議。
首先我們了解下什么是tcc,如下圖
tcc分布式事務(wù)協(xié)議控制整體業(yè)務(wù)事務(wù)分為三個階段。
try
:執(zhí)行業(yè)務(wù)邏輯
confirm
:確定業(yè)務(wù)邏輯執(zhí)行無誤后,確定業(yè)務(wù)邏輯執(zhí)行完成
cancel
:假如try階段有問題,執(zhí)行cancel階段邏輯,取消try階段的數(shù)據(jù)
這就需要我們在設(shè)計業(yè)務(wù)時,在try階段多想想業(yè)務(wù)處理的折中狀態(tài),比如,處理中,支付中,進(jìn)行中等,在confirm階段變更為處理完成,或者在cancel階段變更為處理失敗。
以電商下單為例
假設(shè)我們有一個電商下單的業(yè)務(wù),有三個服務(wù)組成,訂單服務(wù)處理下單邏輯,庫存服務(wù)處理減庫存邏輯,支付服務(wù)處理減賬戶余額邏輯。在下單服務(wù)里先后調(diào)用減庫存和減余額的方法。如果使用tcc分布式事務(wù)來協(xié)調(diào)事務(wù),我們服務(wù)就要做如下設(shè)計:
訂單服務(wù):
- try:支付狀態(tài)設(shè)置為支付中
- confirm:設(shè)置為支付完成
- cancel:設(shè)置為支付失敗
庫存服務(wù):
多加一個鎖定庫存的字段記錄,用于記錄業(yè)務(wù)處理中狀態(tài)
- try:總庫存-1,鎖定庫存+1
- confirm:鎖定庫存-1
- cancel:總庫存+1,鎖定庫存-1
支付服務(wù):
多加一個凍結(jié)金額的字段記錄,用于記錄業(yè)務(wù)處理中狀態(tài)
- try:余額-1,凍結(jié)金額+1
- confirm:凍結(jié)金額-1
- cancel:余額+1,凍結(jié)金額-1
tcc分布式事務(wù)在這里起到了一個事務(wù)協(xié)調(diào)者的角色。真實業(yè)務(wù)只需要調(diào)用try階段的方法。confirm和cancel階段的額方法由tcc框架來幫我們調(diào)用完成最終業(yè)務(wù)邏輯。下面我們假設(shè)如下三個場景的業(yè)務(wù)情況,看tcc如何協(xié)調(diào)業(yè)務(wù)最終一致的。
- 服務(wù)一切正常:所有服務(wù)的try方法執(zhí)行后都沒有問題,庫存足夠,余額足夠。tcc事務(wù)協(xié)調(diào)器會觸發(fā)訂單服務(wù)的confirm方法,將訂單更新為支付完成,觸發(fā)庫存服務(wù)的confirm方法鎖定庫存-1,觸發(fā)支付服務(wù)的confirm方法凍結(jié)金額-1
- 庫存服務(wù)故障,無法調(diào)通:這個時候訂單已經(jīng)生成,狀態(tài)為待支付。當(dāng)調(diào)用庫存超時拋異常后,tcc事務(wù)協(xié)調(diào)器會觸發(fā)訂單服務(wù)的cancel方法將訂單狀態(tài)更新為支付失敗。
- 支付服務(wù)故障,無法調(diào)通:這個時候訂單已經(jīng)生成,狀態(tài)為待支付,總庫存-1,鎖定庫存+1了。當(dāng)調(diào)用支付服務(wù)超時拋異常時,tcc事務(wù)協(xié)調(diào)器會觸發(fā)訂單服務(wù)的cancel方法將訂單狀態(tài)更新為支付失敗,觸發(fā)庫存服務(wù)的cancel方法將庫存+1,鎖定庫存-1。
hmily事務(wù)框架怎么做的?
通過上面對tcc事務(wù)協(xié)議說明大家應(yīng)該都了解了tcc的處理協(xié)調(diào)機(jī)制,下面我們來看看hmily是怎么做到的,我們以接入支持dubbo服務(wù)為例。
概要:首先最基礎(chǔ)兩個應(yīng)用點是aop和dubbo的filter機(jī)制,其次針對一組事務(wù),定義了啟動事務(wù)處理器,參與事務(wù)處理器去協(xié)調(diào)處理不同的事務(wù)單元。外加一個disruptor+ScheduledService處理事務(wù)日志,補(bǔ)償處理失敗的事務(wù)。
hmily框架以@Hmily注解為切入點,定義了一個環(huán)繞織入的切面,注解必填兩個參數(shù)confirmMethod和cancelMethod,也就是tcc協(xié)調(diào)的兩個階段方法。在需要tcc事務(wù)的方法上面加上這個注解,也就托管了tcc三個階段的處理流程。下面是aspect切面的抽象類,不同的RPC框架支持會有不同的實現(xiàn) 。其中真正處理業(yè)務(wù)邏輯需要實現(xiàn)HmilyTransactionInterceptor接口。
實現(xiàn)HmilyTransactionInterceptor接口
@Aspect public abstract class AbstractHmilyTransactionAspect { private HmilyTransactionInterceptor hmilyTransactionInterceptor; protected void setHmilyTransactionInterceptor(final HmilyTransactionInterceptor hmilyTransactionInterceptor) { this.hmilyTransactionInterceptor = hmilyTransactionInterceptor; } /** * this is point cut with {@linkplain Hmily }. */ @Pointcut("@annotation(org.dromara.hmily.annotation.Hmily)") public void hmilyInterceptor() { } /** * this is around in {@linkplain Hmily }. * @param proceedingJoinPoint proceedingJoinPoint * @return Object * @throws Throwable Throwable */ @Around("hmilyInterceptor()") public Object interceptTccMethod(final ProceedingJoinPoint proceedingJoinPoint) throws Throwable { return hmilyTransactionInterceptor.interceptor(proceedingJoinPoint); } /** * spring Order. * * @return int */ public abstract int getOrder(); }
dubbo的aspect抽象實現(xiàn)
@Aspect @Component public class DubboHmilyTransactionAspect extends AbstractHmilyTransactionAspect implements Ordered { @Autowired public DubboHmilyTransactionAspect(final DubboHmilyTransactionInterceptor dubboHmilyTransactionInterceptor) { super.setHmilyTransactionInterceptor(dubboHmilyTransactionInterceptor); } @Override public int getOrder() { return Ordered.HIGHEST_PRECEDENCE; } }
dubbo的HmilyTransactionInterceptor實現(xiàn)
@Component public class DubboHmilyTransactionInterceptor implements HmilyTransactionInterceptor { private final HmilyTransactionAspectService hmilyTransactionAspectService; @Autowired public DubboHmilyTransactionInterceptor(final HmilyTransactionAspectService hmilyTransactionAspectService) { this.hmilyTransactionAspectService = hmilyTransactionAspectService; } @Override public Object interceptor(final ProceedingJoinPoint pjp) throws Throwable { final String context = RpcContext.getContext().getAttachment(CommonConstant.HMILY_TRANSACTION_CONTEXT); HmilyTransactionContext hmilyTransactionContext; //判斷dubbo上下文中是否攜帶了tcc事務(wù),如果有就取出反序列化為事務(wù)上下文對象 if (StringUtils.isNoneBlank(context)) { hmilyTransactionContext = GsonUtils.getInstance().fromJson(context, HmilyTransactionContext.class); RpcContext.getContext().getAttachments().remove(CommonConstant.HMILY_TRANSACTION_CONTEXT); } else { //如果dubbo上下文中沒有,就從當(dāng)前上下文中獲取。如果是事務(wù)發(fā)起者,這里其實也獲取不到事務(wù) hmilyTransactionContext = HmilyTransactionContextLocal.getInstance().get(); } return hmilyTransactionAspectService.invoke(hmilyTransactionContext, pjp); } }
這里主要判斷了dubbo上下文中是否攜帶了tcc事務(wù)。如果沒有就從當(dāng)前線程上下文中獲取,如果是事務(wù)的發(fā)起者,這里其實獲取不到事務(wù)上下文對象的。在invoke里有個獲取事務(wù)處理器的邏輯,如果事務(wù)上下文入?yún)?為null,那么獲取到的就是啟動事務(wù)處理器。
啟動事務(wù)處理器處理邏輯如下
public Object handler(final ProceedingJoinPoint point, final HmilyTransactionContext context) throws Throwable { System.err.println("StarterHmilyTransactionHandler"); Object returnValue; try { HmilyTransaction hmilyTransaction = hmilyTransactionExecutor.begin(point); try { //execute try returnValue = point.proceed(); hmilyTransaction.setStatus(HmilyActionEnum.TRYING.getCode()); hmilyTransactionExecutor.updateStatus(hmilyTransaction); } catch (Throwable throwable) { //if exception ,execute cancel final HmilyTransaction currentTransaction = hmilyTransactionExecutor.getCurrentTransaction(); executor.execute(() -> hmilyTransactionExecutor .cancel(currentTransaction)); throw throwable; } //execute confirm final HmilyTransaction currentTransaction = hmilyTransactionExecutor.getCurrentTransaction(); executor.execute(() -> hmilyTransactionExecutor.confirm(currentTransaction)); } finally { HmilyTransactionContextLocal.getInstance().remove(); hmilyTransactionExecutor.remove(); } return returnValue; }
真正業(yè)務(wù)處理方法,point.proceed();被try,catch包起來了,如果try里面的方法出現(xiàn)異常,就會走h(yuǎn)milyTransactionExecutor.cancel(currentTransaction)的邏輯,如果成功,就走h(yuǎn)milyTransactionExecutor.confirm(currentTransaction)邏輯。其中cancel和confirm里都有協(xié)調(diào)參與者事務(wù)的處理邏輯,以confirm邏輯為例。
public void confirm(final HmilyTransaction currentTransaction) throws HmilyRuntimeException { LogUtil.debug(LOGGER, () -> "tcc confirm .......!start"); if (Objects.isNull(currentTransaction) || CollectionUtils.isEmpty(currentTransaction.getHmilyParticipants())) { return; } currentTransaction.setStatus(HmilyActionEnum.CONFIRMING.getCode()); updateStatus(currentTransaction); final ListhmilyParticipants = currentTransaction.getHmilyParticipants(); ListfailList = Lists.newArrayListWithCapacity(hmilyParticipants.size()); boolean success = true; if (CollectionUtils.isNotEmpty(hmilyParticipants)) { for (HmilyParticipant hmilyParticipant : hmilyParticipants) { try { HmilyTransactionContext context = new HmilyTransactionContext(); context.setAction(HmilyActionEnum.CONFIRMING.getCode()); context.setRole(HmilyRoleEnum.START.getCode()); context.setTransId(hmilyParticipant.getTransId()); HmilyTransactionContextLocal.getInstance().set(context); executeParticipantMethod(hmilyParticipant.getConfirmHmilyInvocation()); } catch (Exception e) { LogUtil.error(LOGGER, "execute confirm :{}", () -> e); success = false; failList.add(hmilyParticipant); } finally { HmilyTransactionContextLocal.getInstance().remove(); } } executeHandler(success, currentTransaction, failList); } }
可以看到executeParticipantMethod(hmilyParticipant.getConfirmHmilyInvocation()),這里執(zhí)行了事務(wù)參與者的confirm方法。同理cancel里面也有類似代碼,執(zhí)行事務(wù)參與者的cancel方法。那么事務(wù)參與者的信息是怎么獲取到的呢?我們需要回到一開始提到的dubbo的filter機(jī)制。
@Activate(group = {Constants.SERVER_KEY, Constants.CONSUMER}) public class DubboHmilyTransactionFilter implements Filter { private HmilyTransactionExecutor hmilyTransactionExecutor; /** * this is init by dubbo spi * set hmilyTransactionExecutor. * * @param hmilyTransactionExecutor {@linkplain HmilyTransactionExecutor } */ public void setHmilyTransactionExecutor(final HmilyTransactionExecutor hmilyTransactionExecutor) { this.hmilyTransactionExecutor = hmilyTransactionExecutor; } @Override @SuppressWarnings("unchecked") public Result invoke(final Invoker invoker, final Invocation invocation) throws RpcException { String methodName = invocation.getMethodName(); Class clazz = invoker.getInterface(); Class[] args = invocation.getParameterTypes(); final Object[] arguments = invocation.getArguments(); converterParamsClass(args, arguments); Method method = null; Hmily hmily = null; try { method = clazz.getMethod(methodName, args); hmily = method.getAnnotation(Hmily.class); } catch (NoSuchMethodException e) { e.printStackTrace(); } if (Objects.nonNull(hmily)) { try { final HmilyTransactionContext hmilyTransactionContext = HmilyTransactionContextLocal.getInstance().get(); if (Objects.nonNull(hmilyTransactionContext)) { if (hmilyTransactionContext.getRole() == HmilyRoleEnum.LOCAL.getCode()) { hmilyTransactionContext.setRole(HmilyRoleEnum.INLINE.getCode()); } RpcContext.getContext().setAttachment(CommonConstant.HMILY_TRANSACTION_CONTEXT, GsonUtils.getInstance().toJson(hmilyTransactionContext)); } final Result result = invoker.invoke(invocation); //if result has not exception if (!result.hasException()) { final HmilyParticipant hmilyParticipant = buildParticipant(hmilyTransactionContext, hmily, method, clazz, arguments, args); if (hmilyTransactionContext.getRole() == HmilyRoleEnum.INLINE.getCode()) { hmilyTransactionExecutor.registerByNested(hmilyTransactionContext.getTransId(), hmilyParticipant); } else { hmilyTransactionExecutor.enlistParticipant(hmilyParticipant); } } else { throw new HmilyRuntimeException("rpc invoke exception{}", result.getException()); } return result; } catch (RpcException e) { e.printStackTrace(); throw e; } } else { return invoker.invoke(invocation); } } @SuppressWarnings("unchecked") private HmilyParticipant buildParticipant(final HmilyTransactionContext hmilyTransactionContext, final Hmily hmily, final Method method, final Class clazz, final Object[] arguments, final Class... args) throws HmilyRuntimeException { if (Objects.isNull(hmilyTransactionContext) || (HmilyActionEnum.TRYING.getCode() != hmilyTransactionContext.getAction())) { return null; } //獲取協(xié)調(diào)方法 String confirmMethodName = hmily.confirmMethod(); if (StringUtils.isBlank(confirmMethodName)) { confirmMethodName = method.getName(); } String cancelMethodName = hmily.cancelMethod(); if (StringUtils.isBlank(cancelMethodName)) { cancelMethodName = method.getName(); } HmilyInvocation confirmInvocation = new HmilyInvocation(clazz, confirmMethodName, args, arguments); HmilyInvocation cancelInvocation = new HmilyInvocation(clazz, cancelMethodName, args, arguments); //封裝調(diào)用點 return new HmilyParticipant(hmilyTransactionContext.getTransId(), confirmInvocation, cancelInvocation); } private void converterParamsClass(final Class[] args, final Object[] arguments) { if (arguments == null || arguments.length < 1) { return; } for (int i = 0; i < arguments.length; i++) { args[i] = arguments[i].getClass(); } } }
需要注意三個地方
- 一個是filter的group定義@Activate(group = {Constants.SERVER_KEY, Constants.CONSUMER}),這里這樣定義后,就只有服務(wù)的消費者會生效,也就是事務(wù)的發(fā)起者,服務(wù)的調(diào)用方會進(jìn)filter的invoke邏輯。
- 只有加@Hmily注解的方法或進(jìn)事務(wù)處理邏輯,其他的方法直接跳過處理
- 最關(guān)鍵的是buildParticipant(hmilyTransactionContext, hmily, method, clazz, arguments, args)方法。dubbo的filter唯一的作用就是收集事務(wù)參與者信息并更新當(dāng)前事務(wù)上線文信息。那么在事務(wù)協(xié)調(diào)時就能夠從當(dāng)前事務(wù)上線文里面獲取到需要協(xié)調(diào)的事務(wù)參與者信息了。
參數(shù)者事務(wù)處理器
public Object handler(final ProceedingJoinPoint point, final HmilyTransactionContext context) throws Throwable { HmilyTransaction hmilyTransaction = null; HmilyTransaction currentTransaction; switch (HmilyActionEnum.acquireByCode(context.getAction())) { case TRYING: try { hmilyTransaction = hmilyTransactionExecutor.beginParticipant(context, point); final Object proceed = point.proceed(); hmilyTransaction.setStatus(HmilyActionEnum.TRYING.getCode()); //update log status to try hmilyTransactionExecutor.updateStatus(hmilyTransaction); return proceed; } catch (Throwable throwable) { //if exception ,delete log. hmilyTransactionExecutor.deleteTransaction(hmilyTransaction); throw throwable; } finally { HmilyTransactionContextLocal.getInstance().remove(); } case CONFIRMING: currentTransaction = HmilyTransactionCacheManager.getInstance().getTccTransaction(context.getTransId()); hmilyTransactionExecutor.confirm(currentTransaction); break; case CANCELING: currentTransaction = HmilyTransactionCacheManager.getInstance().getTccTransaction(context.getTransId()); hmilyTransactionExecutor.cancel(currentTransaction); break; default: break; } Method method = ((MethodSignature) (point.getSignature())).getMethod(); logger.error(HmilyActionEnum.acquireByCode(context.getAction()).getDesc()); return DefaultValueUtils.getDefaultValue(method.getReturnType()); }
參與者事務(wù)處理器的邏輯比啟動事務(wù)處理器要簡單很多,try階段記錄事務(wù)日志用于事務(wù)補(bǔ)償?shù)臅r候使用。其他的confirm和cancel都是由啟動事務(wù)管理器來觸發(fā)調(diào)用執(zhí)行的。這個地方之前糾結(jié)了樓主幾個小時,怎么一個環(huán)繞織入的切面會被觸發(fā)執(zhí)行兩次,其實是啟動事務(wù)處理器里的confirm或cancel觸發(fā)的。
disruptor+ScheduledService處理事務(wù)日志,補(bǔ)償處理失敗的事務(wù)
這個不細(xì)聊了,簡述下。disruptor是一個高性能的隊列。對事務(wù)日志落地的所有操作都是通過disruptor來異步完成的。ScheduledService默認(rèn)128秒執(zhí)行一次,來檢查是否有處理失敗的事務(wù)日志,用于補(bǔ)償事務(wù)協(xié)調(diào)失敗的事務(wù)
文末結(jié)語
相比較2pc的LCN而言,tcc分布式事務(wù)對業(yè)務(wù)侵入性更高。也因2pc的長時間占用事務(wù)資源,tcc的性能肯定比2pc要好。兩者之間本身不存在誰優(yōu)誰劣的問題。所以在做分布式事務(wù)選型時,選一個對的適合自身業(yè)務(wù)的分布式事務(wù)框架就比較重要了。
以上就是tcc分布式事務(wù)框架體系解析的詳細(xì)內(nèi)容,更多關(guān)于tcc分布式事務(wù)框架的資料請關(guān)注腳本之家其它相關(guān)文章!
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