SpringCloud Alibaba Seata (收藏版)
作者：Java老猿
Seata是一款开源的分布式事务解决方案，致力于在微服务架构在提供高性能和简单一样的分布式事务服务。这篇文章主要介绍了SpringCloud Alibaba Seata 的相关知识,需要的朋友可以参考下
一、简介
官网地址: http://seata.io/zh-cn/
1，概念
Seata是一款开源的分布式事务解决方案，致力于在微服务架构在提供高性能和简单一样的分布式事务服务。
2，处理过程
Transaction ID XID:全局唯一的事务ID
Transaction Coordinator(TC) :维护全局和分支事务的状态，驱动全局事务提交或回滚。
Transaction Manager™ :定义全局事务的范围：开始全局事务、提交或回滚全局事务。
Resource Manager(RM) :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。
- TM向TC申请开启一个全局事务，全局事务创建成功并生成一个全局唯一的XID
- XID在微服务调用链路的上下文中传播
- RM向TC注册分支事务，将其纳入XID对应全局事务的管辖
- TM向TC发起针对XID的全局提交或回滚决议
- TC调度XID下管辖的全部分支事务完成提交或回滚请求
二、Seata-Server的安装
1，下载
http://seata.io/zh-cn/blog/download.html 选择指定版本下载(我这里用的是0.9.0)
2，修改配置文件
修改seata/conf/file.conf
#将service中修改group
vgroup_mapping.my_test_tx_group = "my_group"
#将store模块修改为db并修改数据连接，将conf目录下的db_store.sql文件导入到数据库中
mode = "db"
db {
datasource = "dbcp"
db-type = "mysql"
driver-class-name = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://127.0.0.1:3306/seata"
user = "root"
password = "123456"
}
修改seata/conf/registry.conf
registry {
type = "nacos"
nacos {
serverAddr = "localhost:8848"
namespace = ""
cluster = "default"
}
三、Seata的应用
1，订单服务
源码: seata-order-service2001
a，配置pom
<!--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-all</artifactId>
<version>0.9.0</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>
<version>5.1.37</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid-spring-boot-starter</artifactId>
<version>1.1.10</version>
</dependency>
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.0.0</version>
</dependency>
b，配置yaml
server:
port: 2001
spring:
application:
name: seata-order-service
cloud:
alibaba:
seata:
#自定义事务组名称需要与seata-server中的对应
tx-service-group: my_group
nacos:
discovery:
server-addr: localhost:8848
datasource:
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/seata_order
username: root
password: 123456
feign:
hystrix:
enabled: false
logging:
level:
io:
seata: info
mybatis:
mapperLocations: classpath:mapper/*.xml
c，添加file.conf(与seata-server配置相同)
transport {
# tcp udt unix-domain-socket
type = "TCP"
#NIO NATIVE
server = "NIO"
#enable heartbeat
heartbeat = true
#thread factory for netty
thread-factory {
boss-thread-prefix = "NettyBoss"
worker-thread-prefix = "NettyServerNIOWorker"
server-executor-thread-prefix = "NettyServerBizHandler"
share-boss-worker = false
client-selector-thread-prefix = "NettyClientSelector"
client-selector-thread-size = 1
client-worker-thread-prefix = "NettyClientWorkerThread"
# netty boss thread size,will not be used for UDT
boss-thread-size = 1
#auto default pin or 8
worker-thread-size = 8
}
shutdown {
# when destroy server, wait seconds
wait = 3
}
serialization = "seata"
compressor = "none"
}
service {
vgroup_mapping.my_group = "default"
default.grouplist = "127.0.0.1:8091"
enableDegrade = false
disable = false
max.commit.retry.timeout = "-1"
max.rollback.retry.timeout = "-1"
disableGlobalTransaction = false
}
client {
async.commit.buffer.limit = 10000
lock {
retry.internal = 10
retry.times = 30
}
report.retry.count = 5
tm.commit.retry.count = 1
tm.rollback.retry.count = 1
}
## transaction log store
store {
## store mode: file、db
mode = "db"
## file store
file {
dir = "sessionStore"
# branch session size , if exceeded first try compress lockkey, still exceeded throws exceptions
max-branch-session-size = 16384
# globe session size , if exceeded throws exceptions
max-global-session-size = 512
# file buffer size , if exceeded allocate new buffer
file-write-buffer-cache-size = 16384
# when recover batch read size
session.reload.read_size = 100
# async, sync
flush-disk-mode = async
}
## database store
db {
## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp) etc.
datasource = "dbcp"
## mysql/oracle/h2/oceanbase etc.
db-type = "mysql"
driver-class-name = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://127.0.0.1:3306/seata"
user = "root"
password = "123456"
min-conn = 1
max-conn = 3
global.table = "global_table"
branch.table = "branch_table"
lock-table = "lock_table"
query-limit = 100
}
}
lock {
## the lock store mode: local、remote
mode = "remote"
local {
## store locks in user's database
}
remote {
## store locks in the seata's server
}
}
recovery {
#schedule committing retry period in milliseconds
committing-retry-period = 1000
#schedule asyn committing retry period in milliseconds
asyn-committing-retry-period = 1000
#schedule rollbacking retry period in milliseconds
rollbacking-retry-period = 1000
#schedule timeout retry period in milliseconds
timeout-retry-period = 1000
}
transaction {
undo.data.validation = true
undo.log.serialization = "jackson"
undo.log.save.days = 7
#schedule delete expired undo_log in milliseconds
undo.log.delete.period = 86400000
undo.log.table = "undo_log"
}
## metrics settings
metrics {
enabled = false
registry-type = "compact"
# multi exporters use comma divided
exporter-list = "prometheus"
exporter-prometheus-port = 9898
}
support {
## spring
spring {
# auto proxy the DataSource bean
datasource.autoproxy = false
}
}
d，添加registry.conf(与seata-server的配置相同)
registry {
# file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
type = "nacos"
nacos {
serverAddr = "localhost:8848"
namespace = ""
cluster = "default"
}
eureka {
serviceUrl = "http://localhost:8761/eureka"
application = "default"
weight = "1"
}
redis {
serverAddr = "localhost:6379"
db = "0"
}
zk {
cluster = "default"
serverAddr = "127.0.0.1:2181"
session.timeout = 6000
connect.timeout = 2000
}
consul {
cluster = "default"
serverAddr = "127.0.0.1:8500"
}
etcd3 {
cluster = "default"
serverAddr = "http://localhost:2379"
}
sofa {
serverAddr = "127.0.0.1:9603"
application = "default"
region = "DEFAULT_ZONE"
datacenter = "DefaultDataCenter"
cluster = "default"
group = "SEATA_GROUP"
addressWaitTime = "3000"
}
file {
name = "file.conf"
}
}
config {
# file、nacos 、apollo、zk、consul、etcd3
type = "file"
nacos {
serverAddr = "localhost"
namespace = ""
}
consul {
serverAddr = "127.0.0.1:8500"
}
apollo {
app.id = "seata-server"
apollo.meta = "http://192.168.1.204:8801"
}
zk {
serverAddr = "127.0.0.1:2181"
session.timeout = 6000
connect.timeout = 2000
}
etcd3 {
serverAddr = "http://localhost:2379"
}
file {
name = "file.conf"
}
}
e，fegin调用(这里以其中一个account为例)
@FeignClient(value = "seata-account-service")
public interface AccountService {
@RequestMapping("/account/decrease")
public CommonResult decrease(@RequestParam("userId") Long userId, @RequestParam("money") BigDecimal money);
}
f，事务service
@Slf4j
@Service
public class OrderServiceImpl implements OrderService {
@Autowired
OrderDao orderDao;
@Autowired
AccountService accountService;
@Autowired
StorageService storageService;
@Override
@GlobalTransactional(name = "my-order-test",rollbackFor = Exception.class) //加注解使用全局的事务，name 为事务名称不重复就行
public Long create(Order order) {
log.info("=========================下订单，开始");
orderDao.create(order);
log.info("=========================下订单，完成");
log.info("=========================减库存，开始");
storageService.decrease(order.getProductId(), order.getCount());
log.info("=========================减库存，完成");
log.info("=========================减积分，开始");
accountService.decrease(order.getUserId(), order.getMoney());
log.info("=========================减积分，完成");
log.info("=========================订单状态修改，开始");
orderDao.update(order.getId(),1);
log.info("=========================订单状态修改，完成");
return order.getId();
}
}
g，启动类
2，库存服务
源码： seata-storage-service2002
与订单服务中的a，b，c，d，g配置步骤相同
3，账户服务
源码: seata-account-service2003
与库存服务的配置步骤相同
四、Seata的原理解析
参考文档： http://seata.io/zh-cn/docs/overview/what-is-seata.html
1，AT模式 一阶段
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，将其保存成"before image"
2，执行"业务SQL"更新业务数据，在业务数更新之后
3，将其保存成"after image"，最后生成行锁。
以上操作全部在一个数据库事务内完成，这样保证了一阶段操作的原子性。
二阶段提交
因为"业务SQL"在一阶段已经提交至数据库，所以seata框架只需 将一阶段保存的快照数据和行锁删掉 ，完成数据清理即可。
二阶段回滚
二阶段如果是回滚的话，seata就需要回滚一阶段已经执行的"业务SQL"，还原业务数据。
回滚的方式便是用"before image"还原业务数据；但在还原前要首先校验脏写，对比"数据库当前业务数据"和"after image"
如果两份数据完全一致就说明没有脏写，可以还原业务数据，如果不一致就说明有脏写，出现脏写就需要转人工处理。
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