Skip to main content
Version: 2.5.4

使用说明

Phoenix框架提供了事务模块,用来解决分布式事务问题。目前已支持的事务模式有 SAGA 和 TCC。在定义事务处理模型时,你可以灵活配置这两种事务模式。本篇将介绍事务聚合根的定义规范。

maven依赖

如果需要用到事务模块,需要先引入下面的依赖

<dependency>
<groupId>com.iquantex</groupId>
<artifactId>phoenix-transaction</artifactId>
<version>2.5.3</version>
</dependency>

事务聚合根

事务聚合根需要使用@TransactionAggregateAnnotation来标记类,服务启动后phoenix会校验定义规范和创建事务聚合根类对象。事务聚合根类需要遵循如下规范:

  1. 聚合根类需要使用 @TransactionAggregateAnnotation 注解进行标记。
  2. 聚合根类以及聚合根类中的实体均需实现 Serializable 接口,并定义serialVersionUID。
注意

在聚合根上添加 @TransactionAggregateAnnotation 注解时,需要通过 aggregateRootType 指定一个聚合根的类别。用来区分不同的聚合根类。

示例代码

@TransactionAggregateAnnotation(aggregateRootType = "ShoppingAggregateSagaTcc")
public class ShoppingAggregateSagaTcc implements Serializable {
private static final long serialVersionUID = 7007603076743033374L;
// ... act and on method
}

事务入口

事务聚合根需要使用 @TransactionStart 表示事务的入口,该事务开始方法需要定义事务的处理模型。

事务开始方法需要遵循如下规范:

  • 使用 @TransactionStart 注解
  • 该方法只能有一个入参
  • 如果当前类中存在多个使用 @TransactionStart 注解并且只有一个入参的方法,那么你将收到一个AggregateClassException异常

示例代码

Phoenix事务聚合根可以对实体聚合根提供的TCC和SAGA接口灵活组装,该示例使用的是TCC+SAGA混合模式。

    @TransactionStart
public TransactionReturn on(BuyGoodsCmd request) {
this.request = request;
double frozenAmt = request.getQty() * request.getPrice();
return TransactionReturn
.builder()
.addAction(
TccAction.builder().tryCmd(new AccountTryCmd(request.getAccountCode(), frozenAmt))
.confirmCmd(new AccountConfirmCmd(request.getAccountCode(), frozenAmt))
.cancelCmd(new AccountCancelCmd(request.getAccountCode(), frozenAmt)).targetTopic("")
.subTransId(UUID.randomUUID().toString()).tryMaxRetryNum(2).confirmRetryNum(3).cancelRetryNum(3)
.build())
.addAction(
SagaAction.builder().targetTopic("").tiCmd(new GoodsSellCmd(request.getGoodsCode(), request.getQty()))
.ciCmd(new GoodsSellCompensateCmd(request.getGoodsCode(), request.getQty())).tiMaxRetryNum(2)
.ciMaxRetryNum(2).subTransId(UUID.randomUUID().toString()).build()).build();
}

TransactionReturn

事务的入口方法在处理 Command 命令之后需要返回处理的结果以及一些必要的信息,Phoenix对事务的入口方法的返回值做了一层封装,统一放到了TransactionReturn中。

public class TransactionReturn {
private final List<TransactionAction> actions;
// setter getter ...
}

TransactionAction

TransactionAction类定义了目标Topic。如果实体聚合根与事务聚合根分开部署,那么Topic需要设置成目标实体聚合根的Topic。如果实体聚合根与事务聚合根集成部署,那么Topic需要设置成空串("")

public abstract class TransactionAction {
protected String targetTopic;
}

目前支持TCC与SAGA两种事务模式,详细的两种模式的说明请参考 事务模式

TccAction中的tryCmd、confirmCmd和cancelCmd均需要定义,否则事务执行过程中会出现事务回滚/提交异常(无法保证状态一致性)。

public class TccAction extends TransactionAction {
// try 默认最大重试次数
public static final int TRY_MAX_RETRY_NUM_DEFAULT = 5;
// confirm 默认最大重试次数
public static final int CONFIRM_MAX_RETRY_NUM_DEFAULT = 10;
// cancel 默认最大重试次数
public static final int CANCEL_MAX_RETRY_NUM_DEFAULT = 10;
private final Object tryCmd;
private final Object confirmCmd;
private final Object cancelCmd;
private final Integer tryMaxRetryNum;
private final Integer cancelMaxRetryNum;
private final Integer confirmMaxRetryNum;
private final String subTransId;
// getter setter ...
}

正常事务模型中SagaAction中的tiCmd和ciCmd均需要定义,否则事务执行过程中会出现事务回滚异常(无法保证状态一致性)。

public class SagaAction extends TransactionAction {
// ti 默认最大重试次数
public static final int TI_MAX_RETRY_NUM_DEFAULT = 5;
// ci 默认最大重试次数
public static final int CI_MAX_RETRY_NUM_DEFAULT = 10;
private final Object tiCmd;
private final Object ciCmd;
private final Integer tiMaxRetryNum;
private final Integer ciMaxRetryNum;
private final String subTransId;
// getter setter ...
}

针对一些特殊场景,比如只需要Saga发出一个TiCmd,不需要回滚的场景,可以设置SagaAction中的ciCmd为PhoenixServer.TransactionSagaMockCiCmd,参考实例代码

public TransactionReturn on(BuyGoodsCmd buyGoodsCmd) {
this.buyGoodsCmd = buyGoodsCmd;
return TransactionReturn.builder()
.addAction(
SagaAction.builder()
.tiCmd(new AccountQueryCmd(buyGoodsCmd.getAccountCode()))
.ciCmd(SagaAction.genMockCiCmd())
.build())
.build();
}

事件处理

经过实体聚合根处理后产生的Event事件会发送到事务聚合根,可以根据需要定义on方法来处理Event事件。

on() 方法需要遵循如下规范:

  • on方法中不能有IO操作,例如:调用DB操作,调用外部接口
  • on方法中不能有随机函数,例如:获取系统当前时间,获取随机数
  • on方法可以重载定义,并且至少有一个入参。

示例代码

    public TransactionReturn on(AccountTryFailEvent event) {
log.info("商品<{}> 成功售出", event.getGoodsCode());
return null;
}

事务完成

事务完成后,会调用事务聚合根的onFinish方法

onFinish() 方法需要遵循如下规范:

  • onFinish方法是唯一的,不可重载定义,否则你会收到一个AggregateClassException异常

实例代码

public Object onFinish() {
return new BuyGoodsEvent("购买商品成功");
}

完整案例

购买商品是很常见的业务场景,一般涉及购买方账户扣减,以及商家库存扣减,和订单生成。该案例为了简化实现,不生成订单。

整个业务逻辑由2个聚合根(微服务)构成:

  1. 仓储服务: 对给定的商品扣除仓储数量。
  2. 账户服务: 从用户账户中扣除余额。

show

该案例使用的是TCC+Saga模式。

更多的事务模式请参见:PhoenixIQ/phoenix-samples/shopping

command/event定义

Phoenix支持 protostuffjavaBean 协议进行序列化,可以通过以下配置进行指定,设定值分别为:proto_stuffjava

quantex.phoenix.server.default-serializer: java

这里使用javaBean序列化协议进行示范。

事务服务相关事件

@Getter
@AllArgsConstructor
public class BuyGoodsCmd implements Serializable {
private static final long serialVersionUID = -8667685124103764667L;
private String accountCode;
private String goodsCode;
private long qty;
private double price;
}

账户服务相关事件

@Getter
@AllArgsConstructor
public class AccountTryCmd implements Serializable {
private static final long serialVersionUID = 4778468915465985552L;
private String accountCode;
private double frozenAmt;
}

@Getter
@AllArgsConstructor
public class AccountConfirmCmd implements Serializable {
private static final long serialVersionUID = 6915539313674995272L;
private String accountCode;
private double frozenAmt;
}

@Getter
@AllArgsConstructor
public class AccountCancelCmd implements Serializable {
private static final long serialVersionUID = 3086192070311956483L;
private String accountCode;
private double frozenAmt;
}

@Getter
@Setter
@AllArgsConstructor
public class AccountTryOkEvent implements Serializable {
private static final long serialVersionUID = 1525408241428571363L;
private String accountCode;
private double frozenAmt;
}

@Getter
@Setter
@AllArgsConstructor
public class AccountTryFailEvent implements Serializable {
private static final long serialVersionUID = -8352616962272592136L;
private String accountCode;
private double frozenAmt;
private String remark;
}

@Getter
@Setter
@AllArgsConstructor
public class AccountConfirmOkEvent implements Serializable {
private static final long serialVersionUID = -6789245872360028227L;
private String accountCode;
private double frozenAmt;
}

@Getter
@Setter
@AllArgsConstructor
public class AccountCancelOkEvent implements Serializable {
private static final long serialVersionUID = -1017410771260579937L;
private String accountCode;
private double frozenAmt;
}

仓储服务相关事件


@Getter
@AllArgsConstructor
public class GoodsSellCmd implements Serializable {
private static final long serialVersionUID = -4615713736312293797L;
private String goodsCode;
private long qty;
}

@Getter
@AllArgsConstructor
public class GoodsSellCompensateCmd implements Serializable {
private static final long serialVersionUID = -1797830080849363235L;
private String goodsCode;
private long qty;
}

@Getter
@Setter
@AllArgsConstructor
public class GoodsSellOkEvent implements Serializable {
private static final long serialVersionUID = 873406977804359197L;
private String goodsCode;
private long qty;
}

@Getter
@Setter
@AllArgsConstructor
public class GoodsSellFailEvent implements Serializable {
private static final long serialVersionUID = 4825942818190006297L;
private String goodsCode;
private long qty;
private String remark;
}

@Getter
@Setter
@AllArgsConstructor
public class GoodsSellCompensateOkEvent implements Serializable {
private static final long serialVersionUID = 3256345453720913064L;
private String goodsCode;
private long qty;
}

定义事务聚合根

事务聚合根在接收到购买命令时,分别返回账户服务TCC仓储服务Saga的命令给到事务状态机,事务状态机会发送并协调驱动达到最终状态。

事务聚合根可以独立运行,也可以和实体聚合根一起运行。独立运行的情况下,设置targetTopic为实体聚合根的Topic,这里为了方便就设置为空串""代表和实体聚合根集成运行。

事务聚合根的具体定义规则请参考上文 事务聚合根定义

@TransactionAggregateAnnotation(aggregateRootType = "ShoppingAggregateSagaTcc")
public class ShoppingAggregateSagaTcc implements Serializable {
private static final long serialVersionUID = 7007603076743033374L;
private BuyGoodsCmd request;
private String remark = "";

@TransactionStart
public TransactionReturn on(BuyGoodsCmd request) {
this.request = request;
double frozenAmt = request.getQty() * request.getPrice();
return TransactionReturn
.builder()
.addAction(
TccAction.builder().tryCmd(new AccountTryCmd(request.getAccountCode(), frozenAmt))
.confirmCmd(new AccountConfirmCmd(request.getAccountCode(), frozenAmt))
.cancelCmd(new AccountCancelCmd(request.getAccountCode(), frozenAmt)).targetTopic("")
.subTransId(UUID.randomUUID().toString()).tryMaxRetryNum(2).confirmRetryNum(3).cancelRetryNum(3)
.build())
.addAction(
SagaAction.builder().targetTopic("").tiCmd(new GoodsSellCmd(request.getGoodsCode(), request.getQty()))
.ciCmd(new GoodsSellCompensateCmd(request.getGoodsCode(), request.getQty())).tiMaxRetryNum(2)
.ciMaxRetryNum(2).subTransId(UUID.randomUUID().toString()).build()).build();
}

// ... on method
}

定义实体聚合根

实体聚合根中对 Command 的处理需要遵循 SAGA 或 TCC 规范,具体的定义规则可以参考 实体聚合根定义

@EntityAggregateAnnotation(aggregateRootType = "AccountAggregate")
public class AccountAggregate implements Serializable {
private static final long serialVersionUID = 1989248847513267951L;
private double amt;
private double frozenAmt;

@CommandHandler(aggregateRootId = "accountCode")
public ActReturn act(AccountTryCmd cmd) {
if (amt - frozenAmt > cmd.getFrozenAmt()) {
return ActReturn.builder().retCode(RetCode.SUCCESS)
.event(new AccountTryOkEvent(cmd.getAccountCode(), cmd.getFrozenAmt())).build();
} else {
String retMessage = String.format("资金可用不足,剩余:%f, 当前需要冻结:%f", amt - frozenAmt, cmd.getFrozenAmt());
return ActReturn.builder().retCode(RetCode.FAIL).retMessage(retMessage)
.event(new AccountTryFailEvent(cmd.getAccountCode(), cmd.getFrozenAmt(), retMessage)).build();
}
}

public void on(AccountTryOkEvent event) {
frozenAmt += event.getFrozenAmt();
}

public void on(AccountTryFailEvent event) { }

@CommandHandler(aggregateRootId = "accountCode")
public ActReturn act(AccountConfirmCmd cmd) {
return ActReturn.builder().retCode(RetCode.SUCCESS)
.event(new AccountConfirmOkEvent(cmd.getAccountCode(), cmd.getFrozenAmt())).build();
}

public void on(AccountConfirmOkEvent event) {
amt -= event.getFrozenAmt();
frozenAmt -= event.getFrozenAmt();
}

@CommandHandler(aggregateRootId = "accountCode")
public ActReturn act(AccountCancelCmd cmd) {
return ActReturn.builder().retCode(RetCode.SUCCESS)
.event(new AccountCancelOkEvent(cmd.getAccountCode(), cmd.getFrozenAmt())).build();
}

public void on(AccountCancelOkEvent event) {
frozenAmt -= event.getFrozenAmt();
}
}

@EntityAggregateAnnotation(aggregateRootType = "GoodsTcc")
public class GoodsAggregate implements Serializable {
private static final long serialVersionUID = -6111851668488622895L;
private long qty;
private long frozenQty;

@CommandHandler(aggregateRootId = "goodsCode")
public ActReturn act(GoodsSellCmd cmd) {
if (cmd.getQty() < 0) {
throw new RuntimeException("数不能小于0");
}
if (qty > cmd.getQty()) {
return ActReturn.builder().retCode(RetCode.SUCCESS)
.event(new GoodsSellOkEvent(cmd.getGoodsCode(), cmd.getQty())).build();
} else {
String ret = String.format("余额不足,剩余:%d, 当前需要:%d", qty, cmd.getQty());
return ActReturn.builder().retCode(RetCode.FAIL).retMessage(ret)
.event(new GoodsSellFailEvent(cmd.getGoodsCode(), cmd.getQty(), ret)).build();
}
}

public void on(GoodsSellOkEvent event) {
qty -= event.getQty();
}

public void on(GoodsSellFailEvent event) { }

@CommandHandler(aggregateRootId = "goodsCode")
public ActReturn act(GoodsSellCompensateCmd cmd) {
return ActReturn.builder().retCode(RetCode.SUCCESS)
.event(new GoodsSellCompensateOkEvent(cmd.getGoodsCode(), cmd.getQty())).build();
}

public void on(GoodsSellCompensateOkEvent event) {
qty += event.getQty();
}
}

完整的案例请参考:PhoenixIQ/phoenix-samples/shopping