XA規範
二階段送出協定是一個協定,而XA規範是X/Open 組織針對二階段送出協定的實作做的規範。目前幾乎所有的主流資料庫都對XA規範提供了支援。
這樣做的好處是友善多個資源(如資料庫,應用伺服器,消息隊列等)在同一個事務中通路。你可以類比JDBC
我們這篇文章就以MySQL XA為例示範一下XA怎麼玩?
MySQL XA常用的指令如下
指令 | 解釋 |
---|---|
XA START xid | 開啟一個事務,并将事務置于ACTIVE狀态,此後執行的SQL語句都将置于該事務中 |
XA END xid | 将事務置于IDLE狀态,表示事務内的SQL操作完成 |
XA PREPARE xid | 實作事務送出的準備工作,事務狀态置于PREPARED狀态。事務如果無法完成送出前的準備操作,該語句會執行失敗 |
XA COMMIT xid | 事務最終送出,完成持久化 |
XA ROLLBACK xid | 事務復原終止 |
XA RECOVER | 檢視MySQL中存在的PREPARED狀态的xa事務 |
我們在db_account_1和db_account_2都建一個account_info表并初始化2條記錄
CREATE TABLE `account_info`
(
`id` INT(11) NOT NULL AUTO_INCREMENT COMMENT '自增主鍵',
`user_id` VARCHAR(255) NOT NULL COMMENT '使用者id',
`balance` INT(11) NOT NULL DEFAULT 0 COMMENT '使用者餘額',
PRIMARY KEY (`id`)
) ENGINE = InnoDB
AUTO_INCREMENT = 1
DEFAULT CHARSET = utf8;
INSERT INTO account_info (id, user_id, balance)
VALUES (1, '1001', 10000);
INSERT INTO account_info (id, user_id, balance)
VALUES (2, '1002', 10000);
我們以使用者1001向1002轉賬200元為例
mysql> XA START "transfer_money";
Query OK, 0 rows affected (0.01 sec)
mysql> update account_info set balance = balance - 200 where user_id = '1001';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> XA END "transfer_money";
Query OK, 0 rows affected (0.01 sec)
mysql> XA PREPARE "transfer_money";
Query OK, 0 rows affected (0.01 sec)
mysql> XA COMMIT "transfer_money";
Query OK, 0 rows affected (0.01 sec)
在XA START執行後所有資源将會被鎖定,直到執行了XA PREPARE或者XA COMMIT才會釋放。
如果在這個時間段内另外一個事務執行如下語句則會一直被阻塞
這就是XA規範這種解決方案很少被使用的原因,因為中間過程會鎖定資源,很難支援高并發
我們也可以将一個 IDLE 狀态的 XA 事務可以直接送出或者復原
mysql> XA COMMIT "transfer_money";
1399 - XAER_RMFAIL: The command cannot be executed when global transaction is in the IDLE state
mysql> XA COMMIT "transfer_money" ONE PHASE;
Query OK, 0 rows affected (0.01 sec)
mysql> XA START "transfer_money";
Query OK, 0 rows affected (0.01 sec)
mysql> update account_info set balance = balance - 200 where user_id = '1001';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> XA END "transfer_money";
Query OK, 0 rows affected (0.01 sec)
mysql> XA COMMIT "transfer_money" ONE PHASE;
Query OK, 0 rows affected (0.01 sec)
XA事務變化圖
JTA
JTA(Java Transaction API),是J2EE的程式設計接口規範,它是XA規範的Java實作相關的接口有如下2個
javax.transaction.TransactionManager(事務管理器的接口):定義了有關事務的開始、送出、撤回等操作。
javax.transaction.xa.XAResource(滿足XA規範的資源定義接口):一種資源如果要支援JTA事務,就需要讓它的資源實作該XAResource接口,并實作該接口定義的兩階段送出相關的接口
在Java中有很多架構都對XA規範進行了實作,我就示範一下最常用的實作atomikos和seata
atomikos隻能用在單個應用對多個庫進行操作的場景。而seata所有的分布式事務場景都能用
是什麼造成這種差異呢?看Demo
atomikos
先加依賴
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jta-atomikos</artifactId>
<version>2.1.14.RELEASE</version>
</dependency>
配置2個資料源
spring:
jta:
atomikos:
datasource:
primary:
borrow-connection-timeout: 10000.0
max-lifetime: 20000.0
max-pool-size: 25.0
min-pool-size: 3.0
unique-resource-name: test1
xa-data-source-class-name: com.mysql.jdbc.jdbc2.optional.MysqlXADataSource
xa-properties:
password: test
url: jdbc:mysql://myhost:3306/db_account_1
user: test
secondary:
borrow-connection-timeout: 10000.0
max-lifetime: 20000.0
max-pool-size: 25.0
min-pool-size: 3.0
unique-resource-name: test2
xa-data-source-class-name: com.mysql.jdbc.jdbc2.optional.MysqlXADataSource
xa-properties:
password: test
url: jdbc:mysql://myhost:3306/db_account_2
user: test
enabled: true
@Configuration
public class DataSourceConfig {
@Bean
@ConfigurationProperties(prefix = "spring.jta.atomikos.datasource.primary")
public DataSource primaryDataSource() {
return new AtomikosDataSourceBean();
}
@Bean
@ConfigurationProperties(prefix = "spring.jta.atomikos.datasource.secondary")
public DataSource secondaryDataSource() {
AtomikosDataSourceBean ds = new AtomikosDataSourceBean();
return ds;
}
@Bean
public JdbcTemplate primaryJdbcTemplate(
@Qualifier("primaryDataSource") DataSource dataSource) {
return new JdbcTemplate(dataSource);
}
@Bean
public JdbcTemplate secondaryJdbcTemplate(
@Qualifier("secondaryDataSource") DataSource dataSource) {
return new JdbcTemplate(dataSource);
}
}
@Service
public class AccountService {
@Resource
@Qualifier("primaryJdbcTemplate")
private JdbcTemplate primaryJdbcTemplate;
@Resource
@Qualifier("secondaryJdbcTemplate")
private JdbcTemplate secondaryJdbcTemplate;
@Transactional(rollbackFor = Exception.class)
public void tx1() {
Integer money = 100;
String sql = "update account_info set balance = balance + ? where user_id = ?";
primaryJdbcTemplate.update(sql, new Object[]{-money, 1001});
secondaryJdbcTemplate.update(sql, new Object[]{money, 1002});
}
@Transactional(rollbackFor = Exception.class)
public void tx2() {
Integer money = 100;
String sql = "update account_info set balance = balance + ? where user_id = ?";
primaryJdbcTemplate.update(sql, new Object[]{-money, 1001});
secondaryJdbcTemplate.update(sql, new Object[]{money, 1002});
throw new RuntimeException();
}
}
@RunWith(SpringRunner.class)
@SpringBootTest
public class AtomikosAtApplicationTests {
@Resource
private AccountService accountService;
// 正常執行
@Test
public void test1() {
accountService.tx1();
}
// 異常復原
@Test
public void test2() {
accountService.tx2();
}
}
seata
我們需要開發2個應用,就不貼pom依賴了,從github看依賴吧
https://github.com/erlieStar/spring-cloud-distributed-transaction
seata-xa-tm
我們隻需要配置一下application.yaml即可。你可能看到很多文章還需要配置file.conf和registry.conf,用了spring starter後直接在application.yaml配置即可
application.yaml
server:
port: 30002
spring:
application:
name: seata-xa-tm
datasource:
driver-class-name: com.mysql.jdbc.Driver
url : jdbc:mysql://myhost:3306/db_account_1?useUnicode=true&characterEncoding=utf8
username: test
password: test
seata:
data-source-proxy-mode: XA
enabled: true
application-id: ${spring.application.name}
tx-service-group: my_test_tx_group
service:
vgroup-mapping:
my_test_tx_group: default
grouplist:
default: myhost:18091
disable-global-transaction: false
config:
type: file
file:
name: file.conf
registry:
type: file
file:
name: file.conf
用@EnableAutoDataSourceProxy注解開啟資料源代理,隻需指定為XA模式,因為預設是AT模式
@EnableFeignClients
@SpringBootApplication
@EnableAutoDataSourceProxy(dataSourceProxyMode = "XA")
public class SeataXATm {
public static void main(String[] args) {
SpringApplication.run(SeataXATm.class, args);
}
}
開發轉賬接口
@RestController
@RequestMapping("account")
public class AccountController {
@Resource
private JdbcTemplate jdbcTemplate;
@Resource
private RmAccountClient rmAccountClient;
@GlobalTransactional
@RequestMapping("transfer")
public String transfer(@RequestParam("fromUserId") String fromUserId,
@RequestParam("toUserId") String toUserId,
@RequestParam("money") Integer money,
@RequestParam(value = "flag", required = false) Boolean flag) {
String sql = "update account_info set balance = balance + ? where user_id = ?";
jdbcTemplate.update(sql, new Object[]{-money, fromUserId});
String result = rmAccountClient.transfer(fromUserId, toUserId, money);
if ("fail".equals(result)) {
throw new RuntimeException("轉賬失敗");
}
if (flag != null && flag) {
throw new RuntimeException("測試同時復原");
}
return "success";
}
}
調用另外一個賬戶服務,為了友善我就不用注冊中心了,直接指定了服務的位址
@FeignClient(value = "seata-xa-rm", url = "http://127.0.0.1:30001")
public interface RmAccountClient {
@RequestMapping("account/transfer")
String transfer(@RequestParam("fromUserId") String fromUserId,
@RequestParam("toUserId") String toUserId,
@RequestParam("money") Integer money);
}
seata-xa-rm
這是我們開發的另一個賬戶服務
application.yaml
server:
port: 30001
spring:
application:
name: seata-xa-rm
datasource:
driver-class-name: com.mysql.jdbc.Driver
url : jdbc:mysql://myhost:3306/db_account_2?useUnicode=true&characterEncoding=utf8
username: test
password: test
seata:
data-source-proxy-mode: XA
enabled: true
application-id: ${spring.application.name}
tx-service-group: my_test_tx_group
service:
vgroup-mapping:
my_test_tx_group: default
grouplist:
default: myhost:18091
disable-global-transaction: false
config:
type: file
file:
name: file.conf
registry:
type: file
file:
name: file.conf
啟動類
@SpringBootApplication
@EnableAutoDataSourceProxy(dataSourceProxyMode = "XA")
public class SeataXARm {
public static void main(String[] args) {
SpringApplication.run(SeataXARm.class, args);
}
}
轉賬接口
@RestController
@RequestMapping("account")
public class AccountController {
@Resource
private JdbcTemplate jdbcTemplate;
@RequestMapping("transfer")
public String transfer(@RequestParam("fromUserId") String fromUserId,
@RequestParam("toUserId") String toUserId,
@RequestParam("money") Integer money) {
String sql = "update account_info set balance = balance + ? where user_id = ?";
int result = jdbcTemplate.update(sql, new Object[]{money, toUserId});
if (result == 0) {
return "fail";
}
return "success";
}
}
測試
啟動這2個服務
測試正常轉賬
測試seata-xa-tm項目失敗復原
curl http:127.0.0.1:30002/account?fromUserId=1001&toUserId=1002&money=100&flag=truee
用flag=true來讓seata-xa-tm項目失敗復原
測試seata-xa-rm項目失敗復原
curl http:127.0.0.1:30002/account?fromUserId=1001&toUserId=1003&money=100&flag=truee
toUserId=1003,使用者不存在,seata-xa-rm傳回fail復原
參考部落格
彙總
[1]https://segmentfault.com/a/1190000040321750
[2]https://zhuanlan.zhihu.com/p/183753774
xa事務
[3]https://www.jianshu.com/p/a59c79186b6d
[4]https://www.jianshu.com/p/7003d58ea182
jta
[5]https://www.jianshu.com/p/86b4ab4f2d18