Quick Start

Let’s begin with a Microservices example.

Use case

A business logic for user purchasing commodities. The whole business logic is powered by 3 microservices:

• Storage service: deduct storage count on given commodity.
• Order service: create order according to purchase request.
• Account service: debit the balance of user’s account.

Architecture

StorageService

public interface StorageService {
    /**
     * deduct storage count
     */
    void deduct(String commodityCode, int count);
}

OrderService

public interface OrderService {
    /**
     * create order
     */
    Order create(String userId, String commodityCode, int orderCount);
}

AccountService

public interface AccountService {
    /**
     * debit balance of user's account
     */
    void debit(String userId, int money);
}

Main business logic

public class BusinessServiceImpl implements BusinessService {
    private StorageService storageService;
    private OrderService orderService;
    /**
     * purchase
     */
    public void purchase(String userId, String commodityCode, int orderCount) {
        storageService.deduct(commodityCode, orderCount);
        orderService.create(userId, commodityCode, orderCount);
    }
}

public class OrderServiceImpl implements OrderService {
    private OrderDAO orderDAO;
    private AccountService accountService;
    public Order create(String userId, String commodityCode, int orderCount) {
        int orderMoney = calculate(commodityCode, orderCount);
        accountService.debit(userId, orderMoney);
        Order order = new Order();
        order.userId = userId;
        order.commodityCode = commodityCode;
        order.count = orderCount;
        order.money = orderMoney;
        // INSERT INTO orders ...
        return orderDAO.insert(order);
    }
}

Distributed Transaction Solution with SEATA

We just need an annotation @GlobalTransactional on business method:

    @GlobalTransactional
    public void purchase(String userId, String commodityCode, int orderCount) {
        ......
    }

Example powered by Dubbo + SEATA

Step 1: Setup database

• Requirement: MySQL with InnoDB engine.

Note: In fact, there should be 3 database for the 3 services in the example use case. However, we can just create one database and configure 3 data sources for simple.

Modify Spring XML with the database URL/username/password you just created.

dubbo-account-service.xml dubbo-order-service.xml dubbo-storage-service.xml

        <property name="url" value="jdbc:mysql://x.x.x.x:3306/xxx" />
        <property name="username" value="xxx" />
        <property name="password" value="xxx" />

Step 2: Create UNDO_LOG table

UNDO_LOG table is required by SEATA AT mode. You can obtain the specified version of the undo log SQL script from github.

CREATE TABLE IF NOT EXISTS `undo_log`
(
    `branch_id`     BIGINT       NOT NULL COMMENT 'branch transaction id',
    `xid`           VARCHAR(128) NOT NULL COMMENT 'global transaction id',
    `context`       VARCHAR(128) NOT NULL COMMENT 'undo_log context,such as serialization',
    `rollback_info` LONGBLOB     NOT NULL COMMENT 'rollback info',
    `log_status`    INT(11)      NOT NULL COMMENT '0:normal status,1:defense status',
    `log_created`   DATETIME(6)  NOT NULL COMMENT 'create datetime',
    `log_modified`  DATETIME(6)  NOT NULL COMMENT 'modify datetime',
    UNIQUE KEY `ux_undo_log` (`xid`, `branch_id`)
    ) ENGINE = InnoDB AUTO_INCREMENT = 1 DEFAULT CHARSET = utf8mb4 COMMENT ='AT transaction mode undo table';
ALTER TABLE `undo_log` ADD INDEX `ix_log_created` (`log_created`);

Step 3: Create tables for example business

DROP TABLE IF EXISTS `storage_tbl`;
CREATE TABLE `storage_tbl` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `commodity_code` varchar(255) DEFAULT NULL,
  `count` int(11) DEFAULT 0,
  PRIMARY KEY (`id`),
  UNIQUE KEY (`commodity_code`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `order_tbl`;
CREATE TABLE `order_tbl` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` varchar(255) DEFAULT NULL,
  `commodity_code` varchar(255) DEFAULT NULL,
  `count` int(11) DEFAULT 0,
  `money` int(11) DEFAULT 0,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `account_tbl`;
CREATE TABLE `account_tbl` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` varchar(255) DEFAULT NULL,
  `money` int(11) DEFAULT 0,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Step 4: Start Server

• Download server package from https://github.com/apache/incubator-seata/releases, unzip it.

Usage: sh seata-server.sh(for linux and mac) or cmd seata-server.bat(for windows) [options]
  Options:
    --host, -h
      The address is expose to registration center and other service can access seata-server via this ip.
      Default: 0.0.0.0
    --port, -p
      The port to listen.
      Default: 8091
    --storeMode, -m
      log store mode : file、db
      Default: file
    --help
e.g.
sh seata-server.sh -p 8091 -h 127.0.0.1 -m file

Step 5: Run example

Go to samples repo: seata-samples/at-samples, and find a suitable dependency setup. Start Account, Storage, Order, Business services accordingly.