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seata简介

在传统的单体项目中，我们使用@transactional注解就能实现基本的acid事务了。
但是前提是：
1） 数据库支持事务（如：mysql的innodb引擎）
2） 所有业务都在同一个数据库中执行

随着微服务架构的引入，需要对数据库进行分库分表，每个服务拥有自己的数据库，这样传统的事务就不起作用了，那么我们如何保证多个服务中数据的一致性呢？

这样就出现了分布式事务，而seata就是为微服务架构而生的一种高性能、易于使用的分布式事务解决方案。

seata 中有三个基础组件：

  1. transaction coordinator(tc协调者)：维护全局和分支事务的状态，驱动全局提交或回滚。
  2. transaction manager(tm事务管理)：定义全局事务的范围，开启、提交或回滚一个全局事务。
  3. resource manager(rm资源管理)：管理分支事务资源，与 tc 通讯并报告分支事务状态，管理本地事务的提交与回滚。

可以这么说一个分布式事务就是全局事务globaltransaction，而全局事务是由一个个的分支事务组成的，每个分支事务就是一个本地事务。

seata的生命周期

  1. tm 要求 tc 生成一个全局事务，并由 tc 生成一个全局事务xid 返回。
  2. xid 通过微服务调用链传播。
  3. rm 向 tc 注册本地事务，将其注册到 id 为 xid 的全局事务中。
  4. tm 要求 tc 提交或回滚xid 对应的全局事务。
  5. tc 驱动 xid 对应的全局事务对应的所有的分支事务提交或回滚。

seata安装和配置

安装nacos，本案例使用了nacos作为注册中心
https://github.com/alibaba/nacos/releases
下载nacos，本文使用的是windows版本1.4.0
使用命令行进入bin目录，以单机模式启动nacos

startup -m standalone

安装和配置seata

http://seata.io/zh-cn/blog/download.html
下载seata，这里是windows版本的1.4.0
解压后，进入conf目录，配置file.conf和registry.conf两个文件

file.conf主要是数据库的配置，配置如下

registry.conf 是注册中心的配置

另外conf目录中还需要一个脚本文件：nacos-config.sh 用于对nacos进行初始化配置
在seata1.4.0中是没有的，需要自行创建，内容如下：

#!/usr/bin/env bash
# copyright 1999-2019 seata.io group.
#
# licensed under the apache license, version 2.0 (the "license");
# you may not use this file except in compliance with the license.
# you may obtain a copy of the license at、
#
#      http://www.apache.org/licenses/license-2.0
#
# unless required by applicable law or agreed to in writing, software
# distributed under the license is distributed on an "as is" basis,
# without warranties or conditions of any kind, either express or implied.
# see the license for the specific language governing permissions and
# limitations under the license.

while getopts ":h:p:g:t:u:w:" opt
do
  case $opt in
  h)
    host=$optarg
    ;;
  p)
    port=$optarg
    ;;
  g)
    group=$optarg
    ;;
  t)
    tenant=$optarg
    ;;
  u)
    username=$optarg
    ;;
  w)
    password=$optarg
    ;;
  ?)
    echo " usage option: $0 [-h host] [-p port] [-g group] [-t tenant] [-u username] [-w password] "
    exit 1
    ;;
  esac
done

urlencode() {
  for ((i=0; i < ${#1}; i++))
  do
    char="${1:$i:1}"
    case $char in
    [a-za-z0-9.~_-]) printf $char ;;
    *) printf '%%%02x' "'$char" ;;
    esac
  done
}

if [[ -z ${host} ]]; then
    host=localhost
fi
if [[ -z ${port} ]]; then
    port=8848
fi
if [[ -z ${group} ]]; then
    group="seata_group"
fi
if [[ -z ${tenant} ]]; then
    tenant=""
fi
if [[ -z ${username} ]]; then
    username=""
fi
if [[ -z ${password} ]]; then
    password=""
fi

nacosaddr=$host:$port
contenttype="content-type:application/json;charset=utf-8"

echo "set nacosaddr=$nacosaddr"
echo "set group=$group"

failcount=0
templog=$(mktemp -u)
function addconfig() {
  curl -x post -h "${contenttype}" "http://$nacosaddr/nacos/v1/cs/configs?dataid=$(urlencode $1)&group=$group&content=$(urlencode $2)&tenant=$tenant&username=$username&password=$password" >"${templog}" 2>/dev/null
  if [[ -z $(cat "${templog}") ]]; then
    echo " please check the cluster status. "
    exit 1
  fi
  if [[ $(cat "${templog}") =~ "true" ]]; then
    echo "set $1=$2 successfully "
  else
    echo "set $1=$2 failure "
    (( failcount++ ))
  fi
}

count=0
for line in $(cat $(dirname "$pwd")/config.txt | sed s/[[:space:]]//g); do
  (( count++ ))
  key=${line%%=*}
    value=${line#*=}
  addconfig "${key}" "${value}"
done

echo "========================================================================="
echo " complete initialization parameters,  total-count:$count ,  failure-count:$failcount "
echo "========================================================================="

if [[ ${failcount} -eq 0 ]]; then
  echo " init nacos config finished, please start seata-server. "
else
  echo " init nacos config fail. "
fi

在seata的根目录，与conf同级的目录下，还需要config.txt 配置文件，默认也是没有的

只需要对mysql的配置进行修改

完整文件：

transport.type=tcp
transport.server=nio
transport.heartbeat=true
transport.enableclientbatchsendrequest=true
transport.threadfactory.bossthreadprefix=nettyboss
transport.threadfactory.workerthreadprefix=nettyservernioworker
transport.threadfactory.serverexecutorthreadprefix=nettyserverbizhandler
transport.threadfactory.sharebossworker=false
transport.threadfactory.clientselectorthreadprefix=nettyclientselector
transport.threadfactory.clientselectorthreadsize=1
transport.threadfactory.clientworkerthreadprefix=nettyclientworkerthread
transport.threadfactory.bossthreadsize=1
transport.threadfactory.workerthreadsize=default
transport.shutdown.wait=3
service.vgroupmapping.my_test_tx_group=default
service.default.grouplist=127.0.0.1:8091
service.enabledegrade=false
service.disableglobaltransaction=false
client.rm.asynccommitbufferlimit=10000
client.rm.lock.retryinterval=10
client.rm.lock.retrytimes=30
client.rm.lock.retrypolicybranchrollbackonconflict=true
client.rm.reportretrycount=5
client.rm.tablemetacheckenable=false
client.rm.tablemetacheckerinterval=60000
client.rm.sqlparsertype=druid
client.rm.reportsuccessenable=false
client.rm.sagabranchregisterenable=false
client.rm.tccactioninterceptororder=-2147482648
client.tm.commitretrycount=5
client.tm.rollbackretrycount=5
client.tm.defaultglobaltransactiontimeout=60000
client.tm.degradecheck=false
client.tm.degradecheckallowtimes=10
client.tm.degradecheckperiod=2000
client.tm.interceptororder=-2147482648
store.mode=file
store.lock.mode=file
store.session.mode=file
store.publickey=xx
store.file.dir=file_store/data
store.file.maxbranchsessionsize=16384
store.file.maxglobalsessionsize=512
store.file.filewritebuffercachesize=16384
store.file.flushdiskmode=async
store.file.sessionreloadreadsize=100
store.db.datasource=druid
store.db.dbtype=mysql
store.db.driverclassname=com.mysql.jdbc.driver
store.db.url=jdbc:mysql://127.0.0.1:3306/seata?useunicode=true&rewritebatchedstatements=true
store.db.user=root
store.db.password=123456
store.db.minconn=5
store.db.maxconn=30
store.db.globaltable=global_table
store.db.branchtable=branch_table
store.db.querylimit=100
store.db.locktable=lock_table
store.db.maxwait=5000
store.redis.mode=single
store.redis.single.host=127.0.0.1
store.redis.single.port=6379
store.redis.sentinel.mastername=xx
store.redis.sentinel.sentinelhosts=xx
store.redis.maxconn=10
store.redis.minconn=1
store.redis.maxtotal=100
store.redis.database=0
store.redis.password=xx
store.redis.querylimit=100
server.recovery.committingretryperiod=1000
server.recovery.asyncommittingretryperiod=1000
server.recovery.rollbackingretryperiod=1000
server.recovery.timeoutretryperiod=1000
server.maxcommitretrytimeout=-1
server.maxrollbackretrytimeout=-1
server.rollbackretrytimeoutunlockenable=false
server.distributedlockexpiretime=10000
client.undo.datavalidation=true
client.undo.logserialization=jackson
client.undo.onlycareupdatecolumns=true
server.undo.logsavedays=7
server.undo.logdeleteperiod=86400000
client.undo.logtable=undo_log
client.undo.compress.enable=true
client.undo.compress.type=zip
client.undo.compress.threshold=64k
log.exceptionrate=100
transport.serialization=seata
transport.compressor=none
metrics.enabled=false
metrics.registrytype=compact
metrics.exporterlist=prometheus
metrics.exporterprometheusport=9898

在conf目录中，使用git bash进入命令行，输入

sh nacos-config.sh 127.0.0.1

这是对seata进行初始化配置，上图表示所有配置都成功设置了
在nacos中可以看到出现了seata相关的配置

接下来在seata数据库中，新建三个表 

drop table if exists `global_table`;
create table `global_table` (
  `xid` varchar(128)  not null,
  `transaction_id` bigint,
  `status` tinyint not null,
  `application_id` varchar(32),
  `transaction_service_group` varchar(32),
  `transaction_name` varchar(128),
  `timeout` int,
  `begin_time` bigint,
  `application_data` varchar(2000),
  `gmt_create` datetime,
  `gmt_modified` datetime,
  primary key (`xid`),
  key `idx_gmt_modified_status` (`gmt_modified`, `status`),
  key `idx_transaction_id` (`transaction_id`)
);


drop table if exists `branch_table`;
create table `branch_table` (
  `branch_id` bigint not null,
  `xid` varchar(128) not null,
  `transaction_id` bigint ,
  `resource_group_id` varchar(32),
  `resource_id` varchar(256) ,
  `lock_key` varchar(128) ,
  `branch_type` varchar(8) ,
  `status` tinyint,
  `client_id` varchar(64),
  `application_data` varchar(2000),
  `gmt_create` datetime,
  `gmt_modified` datetime,
  primary key (`branch_id`),
  key `idx_xid` (`xid`)
);


drop table if exists `lock_table`;
create table `lock_table` (
  `row_key` varchar(128) not null,
  `xid` varchar(96),
  `transaction_id` long ,
  `branch_id` long,
  `resource_id` varchar(256) ,
  `table_name` varchar(32) ,
  `pk` varchar(36) ,
  `gmt_create` datetime ,
  `gmt_modified` datetime,
  primary key(`row_key`)
);

在项目相关的数据库中，新建表undo_log 用于记录撤销日志

create table `undo_log` (
  `id` bigint(20) not null auto_increment,
  `branch_id` bigint(20) not null,
  `xid` varchar(100) not null,
  `context` varchar(128) not null,
  `rollback_info` longblob not null,
  `log_status` int(11) not null,
  `log_created` datetime not null,
  `log_modified` datetime not null,
  `ext` varchar(100) default null,
  primary key (`id`),
  unique key `ux_undo_log` (`xid`,`branch_id`)
) engine=innodb auto_increment=1 default charset=utf8;

最后在bin目录中，启动命令行，执行seata-server.bat 启动seata服务

项目应用seata

springcloud项目中有两个服务：订单服务和库存服务，基本业务是：

  • 购买商品
  • 插入订单
  • 减少库存

订单详情表

drop table if exists `tb_order_detail`;
create table `tb_order_detail` (
  `id` bigint(20) not null auto_increment comment '订单详情id ',
  `order_id` bigint(20) not null comment '订单id',
  `sku_id` bigint(20) not null comment 'sku商品id',
  `num` int(11) not null comment '购买数量',
  `title` varchar(256) not null comment '商品标题',
  `own_spec` varchar(1024) default '' comment '商品动态属性键值集',
  `price` bigint(20) not null comment '价格,单位：分',
  `image` varchar(128) default '' comment '商品图片',
  primary key (`id`),
  key `key_order_id` (`order_id`) using btree
) engine=myisam auto_increment=131 default charset=utf8 comment='订单详情表';

库存表

drop table if exists `tb_stock`;
create table `tb_stock` (
  `sku_id` bigint(20) not null comment '库存对应的商品sku id',
  `seckill_stock` int(9) default '0' comment '可秒杀库存',
  `seckill_total` int(9) default '0' comment '秒杀总数量',
  `stock` int(9) not null comment '库存数量',
  primary key (`sku_id`)
) engine=myisam default charset=utf8 comment='库存表，代表库存，秒杀库存等信息';

父项目定义了springboot、springcloud、springcloud-alibaba的版本

<parent>
    <groupid>org.springframework.boot</groupid>
    <artifactid>spring-boot-starter-parent</artifactid>
    <version>2.3.10.release</version>
    <relativepath/> <!-- lookup parent from repository -->
</parent>

<dependencymanagement>
    <dependencies>
        <dependency>
            <groupid>org.springframework.cloud</groupid>
            <artifactid>spring-cloud-alibaba-dependencies</artifactid>
            <version>0.9.0.release</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupid>com.alibaba.cloud</groupid>
            <artifactid>spring-cloud-alibaba-dependencies</artifactid>
            <version>2.2.1.release</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupid>org.springframework.cloud</groupid>
            <artifactid>spring-cloud-dependencies</artifactid>
            <version>hoxton.sr8</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencymanagement>

子项目的依赖定义了nacos和seata客户端

<dependency>
   <groupid>mysql</groupid>
   <artifactid>mysql-connector-java</artifactid>
   <scope>runtime</scope>
</dependency>

<dependency>
   <groupid>com.baomidou</groupid>
   <artifactid>mybatis-plus-boot-starter</artifactid>
   <version>3.3.2</version>
</dependency>

<dependency>
   <groupid>org.springframework.boot</groupid>
   <artifactid>spring-boot-starter-web</artifactid>
</dependency>

<dependency>
   <groupid>org.springframework.cloud</groupid>
   <artifactid>spring-cloud-starter-alibaba-nacos-discovery</artifactid>
</dependency>

<dependency>
   <groupid>com.alibaba.cloud</groupid>
   <artifactid>spring-cloud-starter-alibaba-seata</artifactid>
   <exclusions>
       <exclusion>
           <groupid>io.seata</groupid>
           <artifactid>seata-spring-boot-starter</artifactid>
       </exclusion>
   </exclusions>
</dependency>
<dependency>
   <groupid>io.seata</groupid>
   <artifactid>seata-spring-boot-starter</artifactid>
   <version>1.2.0</version>
</dependency>

子项目配置文件

完整配置

server:
  port: 8001
spring:
  application:
    name: stock-service
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
    alibaba:
      seata:
        enabled: true
        enable-auto-data-source-proxy: true
        tx-service-group: my_test_tx_group
        registry:
          type: nacos
          nacos:
            application: seata-server
            server-addr: 127.0.0.1:8848
            username: nacos
            password: nacos
        config:
          type: nacos
          nacos:
            server-addr: 127.0.0.1:8848
            group: seata_group
            username: nacos
            password: nacos
        service:
          vgroup-mapping:
            my_test_tx_group: default
          disable-global-transaction: false
        client:
          rm:
            report-success-enable: false
  datasource:
    driver-class-name: com.mysql.cj.jdbc.driver
    url: jdbc:mysql://localhost:3306/eshop?servertimezone=utc&useunicode=true&usessl=false&characterencoding=utf8
    username: root
    password: 123456

库存服务定义了减库存的方法

@restcontroller
public class stockcontroller {

    @autowired
    private istockservice stockservice;

    @putmapping("/stock")
    public responseentity<stock> reduceskustock(@requestparam("skuid")long skuid,
                                                @requestparam("number")integer number){
        stock stock = stockservice.getbyid(skuid);
        if(stock.getstock() < number){
            throw new runtimeexception("库存不足,skuid:" + skuid);
        }
        stock.setstock(stock.getstock() - number);
        stockservice.updatebyid(stock);
        return responseentity.ok(stock);
    }
}

订单服务在插入订单后，使用feign调用了减库存的服务

@service
public class orderdetailserviceimpl extends serviceimpl<orderdetailmapper, orderdetail> implements iorderdetailservice {

    //库存服务feign
    @autowired
    private stockfeignclient stockfeignclient;

//    @transactional
    @globaltransactional(rollbackfor = {exception.class})
    @override
    public void makeorder(orderdetail orderdetail) {
        this.save(orderdetail); //保存订单
        int x = 11 / 0; //抛出异常
        //减库存
        stockfeignclient.reduceskustock(orderdetail.getskuid(),orderdetail.getnum()); 
    }
}

插订单和减库存属于两个服务，传统的@transactional已经不能保证它们的原子性了
这里使用了seata提供的@globaltransactional全局事务注解，出现任何异常后都能实现业务回滚。
测试用例：

@runwith(springrunner.class)
@springboottest
public class orderserviceapplicationtests {

    @autowired
    private iorderdetailservice orderdetailservice;

    @test
    public void testorder() {
        orderdetail orderdetail = new orderdetail();
        orderdetail.setnum(100);
        orderdetail.setorderid(9999l);
        orderdetail.setprice(9999l);
        orderdetail.setskuid(27359021728l);
        orderdetail.settitle(uuid.randomuuid().tostring());
        orderdetailservice.makeorder(orderdetail);
    }

}

运行后看到启动了全局事务，发生异常后，两个服务也都能成功回滚。

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