CAP原则

CAP原则又称CAP定理，指的是在一个分布式系统中，一致性（Consistency）、可用性（Availability）、分区容错性（Partition tolerance）。CAP 原则指的是，这三个要素最多只能同时实现两点，不可能三者兼顾。

分区性：

数据一致性

分布式事务协议——2PC

假设没有错误情况下：

假设其中某一参与者出错：

不管最后结果如何，第二阶段都会结束当前事务

分布式事务协议——3PC

Seata

seata术语

seata有四种模式：AT、TCC、Sage、XA，其中AT模式是最常用的模式

详情参见https://www.pianshen.com/article/34341263271/

AT模式具体实现步骤

实现步骤：

TM端使用@GolableTranscation进行全局事务开启、提交、回滚
TM开始RPC调用远程服务
RM端seata-client通过扩展DataSourceProxy,实现自动生成undo-log与TC上报
TM告知TC提交/回滚全局事务
TC通知RM各自执行commit/rollback操作，同时清除undo-log

win10启动seata，需要64位java8，如遇闪退情况需检查此问题

1.seata 数据源配置

下载seata程序包，此处版本为1.3.0

修改配置文件E:\soft\seata\seata\conf\file.conf


## transaction log store, only used in seata-server
store {## store mode: file、db、redismode = "db"## file store propertyfile {## store location dirdir = "sessionStore"# branch session size , if exceeded first try compress lockkey, still exceeded throws exceptionsmaxBranchSessionSize = 16384# globe session size , if exceeded throws exceptionsmaxGlobalSessionSize = 512# file buffer size , if exceeded allocate new bufferfileWriteBufferCacheSize = 16384# when recover batch read sizesessionReloadReadSize = 100# async, syncflushDiskMode = async}## database store propertydb {## the implement of javax.sql.DataSource, such as DruidDataSource(druid)/BasicDataSource(dbcp)/HikariDataSource(hikari) etc.datasource = "druid"## mysql/oracle/postgresql/h2/oceanbase etc.dbType = "mysql"driverClassName = "com.mysql.cj.jdbc.Driver"url = "jdbc:mysql://host:3306/seata?characterEncoding=UTF-8&useUnicode=true&useSSL=false&tinyInt1isBit=false&allowPublicKeyRetrieval=true&serverTimezone=Asia/Shanghai"user = "root"password = "xxx"minConn = 5maxConn = 30globalTable = "global_table"branchTable = "branch_table"lockTable = "lock_table"queryLimit = 100maxWait = 5000}## redis store propertyredis {host = "47.100.42.118"port = "6379"password = ""database = "0"minConn = 1maxConn = 10queryLimit = 100}}

此处修改默认配置为：seata数据源类型为db，并配置mysql数据源

如果用mysql作为数据源，需要初始化SQL建表，下面贴出：

DROP TABLE IF EXISTS `branch_table`;
CREATE TABLE `branch_table`  (`branch_id` bigint(20) NOT NULL,`xid` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,`transaction_id` bigint(20) NULL DEFAULT NULL,`resource_group_id` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`resource_id` varchar(256) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`branch_type` varchar(8) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`status` tinyint(4) NULL DEFAULT NULL,`client_id` varchar(64) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`application_data` varchar(2000) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`gmt_create` datetime(0) NULL DEFAULT NULL,`gmt_modified` datetime(0) NULL DEFAULT NULL,PRIMARY KEY (`branch_id`) USING BTREE,INDEX `idx_xid`(`xid`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;-- ----------------------------
-- Table structure for global_table
-- ----------------------------
DROP TABLE IF EXISTS `global_table`;
CREATE TABLE `global_table`  (`xid` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,`transaction_id` bigint(20) NULL DEFAULT NULL,`status` tinyint(4) NOT NULL,`application_id` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`transaction_service_group` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`transaction_name` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`timeout` int(11) NULL DEFAULT NULL,`begin_time` bigint(20) NULL DEFAULT NULL,`application_data` varchar(2000) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`gmt_create` datetime(0) NULL DEFAULT NULL,`gmt_modified` datetime(0) NULL DEFAULT NULL,PRIMARY KEY (`xid`) USING BTREE,INDEX `idx_gmt_modified_status`(`gmt_modified`, `status`) USING BTREE,INDEX `idx_transaction_id`(`transaction_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;-- ----------------------------
-- Table structure for lock_table
-- ----------------------------
DROP TABLE IF EXISTS `lock_table`;
CREATE TABLE `lock_table`  (`row_key` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,`xid` varchar(96) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`transaction_id` bigint(20) NULL DEFAULT NULL,`branch_id` bigint(20) NOT NULL,`resource_id` varchar(256) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`table_name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`pk` varchar(36) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`gmt_create` datetime(0) NULL DEFAULT NULL,`gmt_modified` datetime(0) NULL DEFAULT NULL,PRIMARY KEY (`row_key`) USING BTREE,INDEX `idx_branch_id`(`branch_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

2.seata 注册配置

编辑E:\soft\seata\seata\conf\registory.conf

registry {# file 、nacos 、eureka、redis、zk、consul、etcd3、sofatype = "nacos"nacos {application = "seata-server"serverAddr = "127.0.0.1:8848"# group = "test"namespace = "fcf48d9c-1b25-413a-b365-2fa20ad3568d"cluster = "default"username = ""password = ""}eureka {serviceUrl = "http://localhost:8761/eureka"application = "default"weight = "1"}redis {serverAddr = "localhost:6379"db = 0password = ""cluster = "default"timeout = 0}zk {cluster = "default"serverAddr = "127.0.0.1:2181"sessionTimeout = 6000connectTimeout = 2000username = ""password = ""}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、etcd3type = "nacos"nacos {serverAddr = "localhost"namespace = "fcf48d9c-1b25-413a-b365-2fa20ad3568d"group = "SEATA_GROUP"username = "nacos"password = "nacos"}consul {serverAddr = "127.0.0.1:8500"}apollo {appId = "seata-server"apolloMeta = "http://192.168.1.204:8801"namespace = "application"}zk {serverAddr = "127.0.0.1:2181"sessionTimeout = 6000connectTimeout = 2000username = ""password = ""}etcd3 {serverAddr = "http://localhost:2379"}file {name = "file.conf"}
}

3.推送详细配置到nacos

进入nacos项目地址，下载配置文件，或复制粘贴到本地

https://github.com/seata/seata/tree/1.3.0/script/config-center

在seata/script/config-center/中找到config.txt文件
在seata/script/config-center/nacos/中找到nacos-config.sh脚本

下载完成后config.txt放在bin同级目录下，bin同级目录下新建script文件夹，将sh脚本放入其中

进入script目录，cmd：启动脚本

sh nacos-config.sh -h localhost -p 8848 -t fcf48d9c-1b25-413a-b365-2fa20ad3568d -g  STATE_GROUP -u nacos -w nacos

-h: nacos地址

-p: nacos端口

-t: 命名空间id

-g: 组名

-u -w: nacos账户名密码

在nacos上对应命名空间查看配置文件是否上传成功

4.启动seata

进入目录 E:\soft\seata\seata\bin 启动seata-server.bat，如遇闪退，可以在cmd命令行中执行bat启动程序，这种方式可以查看错误日志

创建一个ＲＭ

引入依赖

<dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-seata</artifactId>
</dependency>

seata配置

seata:application-id: seata-servertx-service-group: my_test_tx_groupconfig:type: nacosnacos:namespace: fcf48d9c-1b25-413a-b365-2fa20ad3568dserver-addr: localhost:8848group: STATE_GROUPusername: "nacos"password: "nacos"registry:type: nacosnacos:application: seata-serverserver-addr: localhost:8848# group:namespace: fcf48d9c-1b25-413a-b365-2fa20ad3568dusername: "nacos"password: "nacos"

RM的业务代码与其他普通项目并无区别…

创建一个TC

同样引入pom依赖、做好seata配置，与RM无异

@GlobalTransactional
public String deleteUser(){//微服务1userService.selectUser();//微服务2userService.delUser();int i = userMapper.deleteById("1");return i==1?"删除成功":"删除失败";
}

通过@GlobalTransactional注解进行全局事务管理，微服务一方失败都会导致全局回滚

password: "nacos"


RM的业务代码与其他普通项目并无区别......## 创建一个TC同样引入pom依赖、做好seata配置，与RM无异```java
@GlobalTransactional
public String deleteUser(){//微服务1userService.selectUser();//微服务2userService.delUser();int i = userMapper.deleteById("1");return i==1?"删除成功":"删除失败";
}