Seata分布式事务原理 1、TM开启分布式事务（TM向TC注册全局事务）2、按业务场景，编排数据库、服务等事务内的资源（RM向TC汇报资源准备状态）3、TM结束分布式事务，事务一阶段结束（TM通知TC提交/回滚）4、TC汇总事务信息，决定最终是提交还是回滚事务5、TC通知所有RM提交/回滚 资源，事务二阶段结束Seata提供了四个模式：AT、TCC、SAGA、XAAT模式两阶段提交协议的演变：一阶段：业务数据和回滚日志记录在同一个本地事务中提交，释放本地锁和连接资源二阶段：提交异步化（能快速完成）；回滚通过一阶段的回滚日志进行反向补偿一阶段:在一阶段，seata会拦截“业务SQL”：1、解析SQL语义，找到“业务SQL”要更新的业务数据，在业务数据被更新前，将其保存为before image2、执行“业务SQL”更新业务数据，更新之后将业务数据保存为after image3、最后生成行锁以上操作全部在一个数据库事务内完成，保证了一阶段操作的原子性二阶段:1、成功提交二阶段正常执行的话，只需将一阶段保存的快照数据和行锁删除，即可完成数据清理，因为“业务SQl”在一阶段已经在提交至数据库2、事务回滚二阶段如果出现异常，需要事务回滚，seata就需要回滚一阶段已经执行的“业务SQL”，还原业务数据；回滚方式使用before image还原业务数据，在还原之前需要做校验脏写，对比数据库当前的业务数据和after image数据快照，如果两份数据完全一致，就说明没有脏写，执行还原操作，如果不一致，就需要转人工处理

Seata seata是一个分布式的解决方案，致力于在微服务架构下提供高性能和简单易用的分布式微服务，官网：http://seata.io/zh-cn/一、三组概念TC 事务协调者：维护全局和分支事务的状态，驱动全局事务提交或回滚TM 事务管理器：定义全局事务的范围：开始、提交、回滚RM 资源管理器：管理分支事务处理的资源，与TC交谈以注册分支事务和报告分支事务的状态，并驱动分支事务提交或回滚二、安装GitHub地址：https://github.com/seata/seata（以Nacos 2.0、Seata 1.4.2为例）修改配置文件1、/conf/file.conf (注意与1.0之前的版本区分，1.0之后可以在yml文件中指定service配置)修改数据库模式（使用数据库存储事务信息）和数据源2、/conf/registry.conf3、mysql建表1、新建seata数据库2、运行mysql.sql注意：建表sql在/conf/REDME.md文件中，点击server出现存放sql的github地址：https://github.com/seata/seata/tree/develop/script/server4、启动先启动Nacos再启动Seata（bin/seata-server.bat）三、业务测试1、业务说明创建三个微服务：订单---库存---账户大致流程：当用户下单时，订单服务创建订单，远程调用库存服务扣减库存，再通过远程调用账户服务来扣减账户余额，最后在订单服务中修改订单状态为已完成。2、数据库建表创建三个数据库seata_order（订单），seata_storage（库存），seata_account（账户）创建对应的表-- t_order DROP TABLE IF EXISTS `t_order`; CREATE TABLE `t_order` ( `id` bigint(11) NOT NULL AUTO_INCREMENT, `user_id` bigint(11) NULL DEFAULT NULL COMMENT '用户id', `product_id` bigint(11) NULL DEFAULT NULL COMMENT '产品id', `count` int(11) NULL DEFAULT NULL COMMENT '数量', `money` decimal(11, 0) NULL DEFAULT NULL COMMENT '金额', `status` int(1) NULL DEFAULT NULL COMMENT '订单状态：0：创建中; 1：已完结', PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 14 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; -- t_storage DROP TABLE IF EXISTS `t_storage`; CREATE TABLE `t_storage` ( `id` bigint(11) NOT NULL AUTO_INCREMENT, `product_id` bigint(11) NULL DEFAULT NULL COMMENT '产品id', `total` int(11) NULL DEFAULT NULL COMMENT '总库存', `used` int(11) NULL DEFAULT NULL COMMENT '已用库存', `residue` int(11) NULL DEFAULT NULL COMMENT '剩余库存', PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 2 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; INSERT INTO `t_storage` VALUES (1, 1, 100, 0, 100); -- t_account DROP TABLE IF EXISTS `t_account`; CREATE TABLE `t_account` ( `id` bigint(11) NOT NULL AUTO_INCREMENT COMMENT 'id', `user_id` bigint(11) NULL DEFAULT NULL COMMENT '用户id', `total` decimal(10, 0) NULL DEFAULT NULL COMMENT '总额度', `used` decimal(10, 0) NULL DEFAULT NULL COMMENT '已用余额', `residue` decimal(10, 0) NULL DEFAULT 0 COMMENT '剩余可用额度', PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 2 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic; INSERT INTO `t_account` VALUES (1, 1, 1000, 0, 1000);undo回滚日志表，三个库每个都需要创建一张回滚表，分别执行三次DROP TABLE IF EXISTS `undo_log`; CREATE TABLE `undo_log` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `branch_id` bigint(20) NOT NULL, `xid` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL, `context` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL, `rollback_info` longblob NOT NULL, `log_status` int(11) NOT NULL, `log_created` datetime(0) NOT NULL, `log_modified` datetime(0) NOT NULL, `ext` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL, PRIMARY KEY (`id`) USING BTREE, UNIQUE INDEX `ux_undo_log`(`xid`, `branch_id`) USING BTREE ) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;3、seata-order-servicepom<dependencies> <!-- API --> <dependency> <groupId>com.sw</groupId> <artifactId>cloud-api-commons</artifactId> <version>1.0-SNAPSHOT</version> </dependency> <!--nacos--> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId> </dependency> <!--seata--> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-seata</artifactId> <exclusions> <exclusion> <artifactId>seata-all</artifactId> <groupId>io.seata</groupId> </exclusion> </exclusions> </dependency> <dependency> <groupId>io.seata</groupId> <artifactId>seata-spring-boot-starter</artifactId> <version>1.4.0</version> </dependency> <!--feign--> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> </dependency> <!--web-actuator--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> <!--mysql-druid--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.1.16</version> </dependency> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <optional>true</optional> </dependency> </dependencies>ymlserver: port: 2001 spring: application: name: seata-order-service cloud: nacos: discovery: server-addr: localhost:8848 datasource: driver-class-name: com.mysql.jdbc.Driver url: jdbc:mysql://127.0.0.1:3306/seata_order?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf-8 username: root password: 123456 seata: enabled: true application-id: ${spring.application.name} # 自定义事务组名称 tx-service-group: test_tx_group service: vgroup-mapping: test_tx_group: default config: nacos: namespace: server-addr: 127.0.0.1:8848 group: SEATA_GROUP userName: "nacos" password: "nacos" registry: type: nacos nacos: application: seata-server server-addr: 127.0.0.1:8848 namespace: userName: "nacos" password: "nacos" feign: hystrix: enabled: false logging: level: io: seata: info启动类@SpringBootApplication(exclude = DataSourceAutoConfiguration.class) //取消自动创建数据源 @EnableDiscoveryClient @EnableFeignClients @MapperScan("com.sw.mapper") public class SeataOrderMain2001 { public static void main(String[] args) { SpringApplication.run(SeataOrderMain2001.class, args); } }pojo@Data @NoArgsConstructor @AllArgsConstructor public class Order implements Serializable { private Long id; private Long userId; private Long productId; private Integer count; private BigDecimal money; private Integer status; //订单状态：0：创建中；1：已完结 }mapper@Repository public interface OrderMapper { /** * 新建订单 * @param order */ @Insert("insert into t_order(id,user_id,product_id,count,money,status) " + "values(null,#{userId},#{productId},#{count},#{money},0)") void create(Order order); /** * 更新订单 * @param userId * @param status */ @Update("update t_order set status = 1 " + "where user_id=#{userId} and status = #{status}") void update(@Param("userId")Long userId, @Param("status")Integer status); }serviceOrderServicepublic interface OrderService { void create(Order order); }StorageService@FeignClient("seata-storage-service") public interface StorageService { @PostMapping("/storage/decrease") CommonResult decrease(@RequestParam("productId")Long productId, @RequestParam("count")Integer count); }AccountService@FeignClient("seata-account-service") public interface AccountService { @PostMapping("/account/decrease") CommonResult decrease(@RequestParam("userId")Long userId, @RequestParam("money")BigDecimal money); }service实现@Service @Slf4j public class OrderServiceImpl implements OrderService { @Autowired private OrderMapper orderMapper; @Autowired private AccountService accountService; @Autowired private StorageService storageService; @Override public void create(Order order) { //1.新建订单 log.info("===开始新建订单==="); orderMapper.create(order); //2.扣减库存 log.info("===订单微服务调用库存==="); storageService.decrease(order.getProductId(), order.getCount()); log.info("===订单微服务调用库存,库存数量操作结束==="); //3.扣减账户 log.info("===订单微服务调用账户余额==="); accountService.decrease(order.getUserId(), order.getMoney()); log.info("===订单微服务调用账户余额,账户余额操作结束==="); //4.修改订单状态 log.info("===修改订单状态，开始==="); //从 0 到 1，1代表已经完成 orderMapper.update(order.getUserId(), 0); log.info("===修改订单状态，操作结束==="); log.info("订单操作完成(*^_^*)"); } }controller@RestController @RequestMapping("/order") public class OrderController { @Autowired private OrderService orderService; @GetMapping("/create") public CommonResult create(Order order){ orderService.create(order); return new CommonResult(200, "订单创建成功！"); } } config主启动类排除了数据源配置，此处需指定数据源代理@Configuration public class DataSourceProxyConfig { @Bean @ConfigurationProperties(prefix = "spring.datasource") public DataSource druidDataSource(){ return new DruidDataSource(); } @Primary @Bean("dataSource") public DataSourceProxy dataSourceProxy(DataSource dataSource){ return new DataSourceProxy(dataSource); } }4、seata-storage-serviceymlserver: port: 2002 spring: application: name: seata-storage-service cloud: nacos: discovery: server-addr: localhost:8848 datasource: driver-class-name: com.mysql.jdbc.Driver url: jdbc:mysql://127.0.0.1:3306/seata_storage?useSSL=true&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf-8 username: root password: 123456 seata: enabled: true application-id: ${spring.application.name} tx-service-group: test_tx_group service: vgroup-mapping: test_tx_group: default config: nacos: namespace: server-addr: 127.0.0.1:8848 group: SEATA_GROUP userName: "nacos" password: "nacos" registry: type: nacos nacos: application: seata-server server-addr: 127.0.0.1:8848 namespace: userName: "nacos" password: "nacos" feign: hystrix: enabled: false logging: level: io: seata: infomapper@Repository public interface StorageMapper { /** * 扣减库存信息 * @param productId * @param count */ @Update("update t_storage " + "set used = used + #{count}," + "residue = residue - #{count} "+ "where product_id = #{productId}" ) void decrease(@Param("productId")Long productId, @Param("count")Integer count); }servicepublic interface StorageService { void decrease(Long productId, Integer count); }service实现@Slf4j @Service public class StorageServiceImpl implements StorageService { @Autowired private StorageMapper storageMapper; @Override public void decrease(Long productId, Integer count) { log.info("===storage-service 开始扣减库存==="); storageMapper.decrease(productId, count); log.info("===storage-service 扣减库存操作结束==="); } }其他配置同理order微服务模块的5、seata-account-servicemapper@Repository public interface AccountMapper { /** * 扣减账户余额 * @param userId * @param money */ @Update("update t_account set "+ "used = used + #{money},"+ "residue = residue - #{money} "+ "where user_id = #{userId}" ) void decrease(@Param("userId")Long userId, @Param("money") BigDecimal money); }其他配置同理storage微服务模块的创建6、不添加全局事务管理测试seata-account-service模块1、手动模拟超时@Slf4j @Service public class AccountServiceImpl implements AccountService { @Autowired private AccountMapper accountMapper; @Override public void decrease(Long userId, BigDecimal money) { log.info("===account-service 开始扣减账户余额==="); //模拟超时异常 try { TimeUnit.SECONDS.sleep(20); } catch (InterruptedException e) { e.printStackTrace(); } accountMapper.decrease(userId, money); log.info("===account-service 扣减账户余额操作结束==="); } }浏览器输入http://localhost:2001/order/create?userId=1&productId=1&count=10&money=100报错Read TimeOut异常：此时数据库的状态：7、开启全局事务在order模块中添加全局事务注解@GlobalTransactional使用同样的方法测试，发生调用超时异常后，数据库中被修改的数据回滚到了操作之前的状态