add blog - How to use Fescar to ensure consistency between Dubbo Microservices

blog/en-us/dubbo-fescar.md

@@ -0,0 +1,225 @@
+---
+title: How to use Fescar to ensure consistency between Dubbo Microservices
+keywords: Dubbo,Fescar,Consistency
+description: This article will introduce you how to use Fescar to ensure consistency between Dubbo Microservices.
+---
+# How to use Fescar to ensure consistency between Dubbo Microservices
+
+
+
+## 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
+
+![Architecture](../../img/blog/fescar/fescar-1.png) 
+
+
+### StorageService
+
+```java
+public interface StorageService {
+
+    /**
+     * deduct storage count
+     */
+    void deduct(String commodityCode, int count);
+}
+```
+
+### OrderService
+
+```java
+public interface OrderService {
+
+    /**
+     * create order
+     */
+    Order create(String userId, String commodityCode, int orderCount);
+}
+```
+
+### AccountService
+
+```java
+public interface AccountService {
+
+    /**
+     * debit balance of user's account
+     */
+    void debit(String userId, int money);
+}
+```
+
+### Main business logic
+
+```java
+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);
+    }
+}
+```
+
+```java
+public class StorageServiceImpl implements StorageService {
+
+  private StorageDAO storageDAO;
+
+    @Override
+    public void deduct(String commodityCode, int count) {
+        Storage storage = new Storage();
+        storage.setCount(count);
+        storage.setCommodityCode(commodityCode);
+        storageDAO.update(storage);
+    }
+}
+```
+
+```java
+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;
+
+        return orderDAO.insert(order);
+    }
+}
+```
+
+## Distributed Transaction Solution with Fescar
+
+![undefined](../../img/blog/fescar/fescar-2.png) 
+
+We just need an annotation `@GlobalTransactional` on business method: 
+
+```java
+
+    @GlobalTransactional
+    public void purchase(String userId, String commodityCode, int orderCount) {
+        ......
+    }
+```
+
+## Example powered by Dubbo + Fescar
+
+### 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
+
+```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 for Fescar
+
+`UNDO_LOG` table is required by Fescar AT mode.
+
+```sql
+CREATE TABLE `undo_log` (
+  `id` bigint(20) NOT NULL AUTO_INCREMENT,
+  `branch_id` bigint(20) NOT NULL,
+  `xid` varchar(100) 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`),
+  KEY `idx_unionkey` (`xid`,`branch_id`)
+) ENGINE=InnoDB AUTO_INCREMENT=159 DEFAULT CHARSET=utf8
+```
+
+### Step 3: Create tables for example business
+
+```sql
+
+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 Fescar-Server
+
+- Download server [package](https://github.com/alibaba/fescar/releases), unzip it.
+- Start Fescar-Server
+
+```shell
+sh fescar-server.sh $LISTEN_PORT $PATH_FOR_PERSISTENT_DATA
+
+e.g.
+
+sh fescar-server.sh 8091 /home/admin/fescar/data/
+```
+
+### Step 5: Run example
+
+- Start AccountService
+- Start StorageService
+- Start OrderService
+- Run BusinessService for test
+
+[Related code](https://github.com/alibaba/fescar/tree/develop/examples/src/main/java/com/alibaba/fescar/tm/dubbo)   
+[learn more about Fescar](https://github.com/alibaba/fescar/)

site_config/blog.js

@@ -3,6 +3,13 @@ export default {
     barText: 'Blog',
     postsTitle: 'All posts',
     list: [
+        {
+            title: 'How to use Fescar to ensure consistency between Dubbo Microservices',
+            author: '@slievrly',
+            dateStr: 'Jan 17th, 2019',
+            desc: 'This blog describes details of using Fescar to ensure consistency between Dubbo Microservices',
+            link: '/en-us/blog/dubbo-fescar.html',
+        },
         {
             title: 'Prepare an Apache Release',
             author: 'Jun Liu',