Spring Cloud Alibaba--seata微服务详解之分布式事务（三）

上篇讲述gateway的部署和使用，gateway统一管理和转发了HTTP请求，在互联网中大型项目一定存在复杂的业务关系，尤其在商城类软件中如淘宝、PDD等商城，尤其在秒杀场景中，并发量可以到达千万级别，此时数据库就会显得很无力。

以Mysql为例，熟悉数据库的童鞋都知道数据库有原子性、隔离性、一致性、持久性四大特性，隔离级别分为脏读、幻读、可重复读、序列化四种。Mysql默认的隔离级别在可重复读，在高并发中显然会出现大量可重复度数据，分布式数据库显然是最适合的解决方案。

1、Seata介绍

Seata是一款开源的分布式事务解决方案，致力于提供高性能和简单易用的分布式事务服务。Seata 将为用户提供了 AT、TCC、SAGA 和 XA 事务模式，为用户打造一站式的分布式解决方案。

模式
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	RM (Resource Manager) - 资源管理器
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。

2、Seata服务部署

官网链接：http://seata.io/zh-cn/

seata数据库脚本：https://github.com/seata/seata/blob/1.5.2/script/server/db/mysql.sql

seata配置文件：https://github.com/seata/seata/blob/1.5.2/script/config-center/config.txt

下载seata的压缩包，并且解压，在seata/script/server/db/下找到sql脚本

在mysql中创建名为seata的数据库，并执行脚本：

-- -------------------------------- The script used when storeMode is 'db' --------------------------------
-- the table to store GlobalSession data
CREATE TABLE IF NOT EXISTS `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_status_gmt_modified` (`status` , `gmt_modified`),
    KEY `idx_transaction_id` (`transaction_id`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8mb4;

-- the table to store BranchSession data
CREATE TABLE IF NOT EXISTS `branch_table`
(
    `branch_id`         BIGINT       NOT NULL,
    `xid`               VARCHAR(128) NOT NULL,
    `transaction_id`    BIGINT,
    `resource_group_id` VARCHAR(32),
    `resource_id`       VARCHAR(256),
    `branch_type`       VARCHAR(8),
    `status`            TINYINT,
    `client_id`         VARCHAR(64),
    `application_data`  VARCHAR(2000),
    `gmt_create`        DATETIME(6),
    `gmt_modified`      DATETIME(6),
    PRIMARY KEY (`branch_id`),
    KEY `idx_xid` (`xid`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8mb4;

-- the table to store lock data
CREATE TABLE IF NOT EXISTS `lock_table`
(
    `row_key`        VARCHAR(128) NOT NULL,
    `xid`            VARCHAR(128),
    `transaction_id` BIGINT,
    `branch_id`      BIGINT       NOT NULL,
    `resource_id`    VARCHAR(256),
    `table_name`     VARCHAR(32),
    `pk`             VARCHAR(36),
    `status`         TINYINT      NOT NULL DEFAULT '0' COMMENT '0:locked ,1:rollbacking',
    `gmt_create`     DATETIME,
    `gmt_modified`   DATETIME,
    PRIMARY KEY (`row_key`),
    KEY `idx_status` (`status`),
    KEY `idx_branch_id` (`branch_id`),
    KEY `idx_xid_and_branch_id` (`xid` , `branch_id`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8mb4;

CREATE TABLE IF NOT EXISTS `distributed_lock`
(
    `lock_key`       CHAR(20) NOT NULL,
    `lock_value`     VARCHAR(20) NOT NULL,
    `expire`         BIGINT,
    primary key (`lock_key`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8mb4;

INSERT INTO `distributed_lock` (lock_key, lock_value, expire) VALUES ('AsyncCommitting', ' ', 0);
INSERT INTO `distributed_lock` (lock_key, lock_value, expire) VALUES ('RetryCommitting', ' ', 0);
INSERT INTO `distributed_lock` (lock_key, lock_value, expire) VALUES ('RetryRollbacking', ' ', 0);
INSERT INTO `distributed_lock` (lock_key, lock_value, expire) VALUES ('TxTimeoutCheck', ' ', 0);

在seata/script/config-center/下找到config.txt 配置文件。

seata需要集成到微服务中去，所以配置文件我们依然使用nacos管理。

#For details about configuration items, see https://seata.io/zh-cn/docs/user/configurations.html
#Transport configuration, for client and server
transport.type=TCP
transport.server=NIO
transport.heartbeat=true
transport.enableTmClientBatchSendRequest=false
transport.enableRmClientBatchSendRequest=true
transport.enableTcServerBatchSendResponse=false
transport.rpcRmRequestTimeout=30000
transport.rpcTmRequestTimeout=30000
transport.rpcTcRequestTimeout=30000
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
transport.serialization=seata
transport.compressor=none

#Transaction routing rules configuration, only for the client
service.vgroupMapping.default_tx_group=default
#If you use a registry, you can ignore it
service.default.grouplist=127.0.0.1:8091
service.enableDegrade=false
service.disableGlobalTransaction=false

#Transaction rule configuration, only for the client
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=true
client.rm.tableMetaCheckerInterval=60000
client.rm.sqlParserType=druid
client.rm.reportSuccessEnable=false
client.rm.sagaBranchRegisterEnable=false
client.rm.sagaJsonParser=fastjson
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
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
#For TCC transaction mode
tcc.fence.logTableName=tcc_fence_log
tcc.fence.cleanPeriod=1h

#Log rule configuration, for client and server
log.exceptionRate=100

#Transaction storage configuration, only for the server. The file, DB, and redis configuration values are optional.
store.mode=file
store.lock.mode=file
store.session.mode=file
#Used for password encryption
store.publicKey=

#If `store.mode,store.lock.mode,store.session.mode` are not equal to `file`, you can remove the configuration block.
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

#These configurations are required if the `store mode` is `db`. If `store.mode,store.lock.mode,store.session.mode` are not equal to `db`, you can remove the configuration block.
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=username
store.db.password=password
store.db.minConn=5
store.db.maxConn=30
store.db.globalTable=global_table
store.db.branchTable=branch_table
store.db.distributedLockTable=distributed_lock
store.db.queryLimit=100
store.db.lockTable=lock_table
store.db.maxWait=5000

#These configurations are required if the `store mode` is `redis`. If `store.mode,store.lock.mode,store.session.mode` are not equal to `redis`, you can remove the configuration block.
store.redis.mode=single
store.redis.single.host=127.0.0.1
store.redis.single.port=6379
store.redis.sentinel.masterName=
store.redis.sentinel.sentinelHosts=
store.redis.maxConn=10
store.redis.minConn=1
store.redis.maxTotal=100
store.redis.database=0
store.redis.password=
store.redis.queryLimit=100

#Transaction rule configuration, only for the server
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
server.xaerNotaRetryTimeout=60000
server.session.branchAsyncQueueSize=5000
server.session.enableBranchAsyncRemove=false
server.enableParallelRequestHandle=false

#Metrics configuration, only for the server
metrics.enabled=false
metrics.registryType=compact
metrics.exporterList=prometheus
metrics.exporterPrometheusPort=9898

将上面seata的t配置文件config.tx导入到nacos：

修改seata的配置文件内容：

# 修改store.mode为db，配置数据库连接
store.mode=db
store.db.dbType=mysql
store.db.driverClassName=com.mysql.cj.jdbc.Driver
store.db.url=jdbc:mysql://localhost:3306/seata?useUnicode=true&rewriteBatchedStatements=true
store.db.user=数据库用户名
store.db.password=数据库密码

在seata/config/application.yml 修改seata配置信息：

seata:
  config:
    type: nacos
    nacos:
      server-addr: 127.0.0.1:8848
      namespace:
      group: SEATA_GROUP
      data-id: seataServer.properties
  registry:
    type: nacos
    preferred-networks: 30.240.*
    nacos:
      application: seata-server
      server-addr: 127.0.0.1:8848
      namespace:
      group: SEATA_GROUP
      cluster: default
  #store:
  	#mode: file

最后到seata/bin目录下运行seata-server.bat即可启动seata服务。在nacos服务列表里可以看到seata已经被注册到nacos中：

3、项目集成

在父级工程下创建seata子级工，添加seata依赖：

<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>1.5.2</version>
</dependency>

在需要使用全局事务管理的服务中添加seata子级工程依赖，在处理数据库业务的时候添加@GlobalTransactional注解代替@Transactional注解就可以了。