Distributed Transaction Access

Last Updated：2020-07-20

Preparation

Download Maven in the development environment and configure the environment.
Install JDK1.8 in the development environment and complete the environment configuration (currently only supports version 1.8)
Currently, only the combination with the Tianhe microservice platform is supported. Please refer to the "Spring-Cloud-Application Access" document for access
Install the distributed transaction-related jar package into Maven in the development environment: Download transaction dependency package and install it based on README in the compressed package

Introduce Dependencies

Modify the pom.xml file and introduce the required maven dependencies according to the usage scenarios.

<!--Access between services via rest --> 
<dependency>
    <groupId>com.baidu.btcc</groupId>
    <artifactId>btcc-rest-template</artifactId>
    <version>2.3.0-SNAPSHOT</version>
</dependency>
<!--Access between services via feign--> 
<dependency>
    <groupId>com.baidu.btcc</groupId>
    <artifactId>btcc-spring-cloud</artifactId>
    <version>2.3.0-SNAPSHOT</version>
</dependency>

Add Configuration Items

Add the following configuration to application.properties to upload transaction data.

# Name of the module to which the transaction belongs 
btcc.moduleName=xxxx
# User authentication information, which can be viewed and updated through the console 
btcc.token=xxxx
# Transaction grouping, which needs to be managed through the console 
btcc.transGroup=xxxx
# Upload address of transaction data 
btcc.serverAddress=list://100.64.253.71:8024
# Perform operations of confirm and cancel synchronously/asynchronously; true indicates synchronization, and false indicates asynchronous 
btcc.isSync=false
# Timeout for connecting btcc-server 
btcc.connectTimeoutMillis=200
# Read timeout for accessing btcc-server 
btcc.readTimeoutMillis=1000
# Write timeout for accessing btcc-server 
btcc.writeTimeoutMillis=200
# Maximum number of connections to btcc-server 
btcc.maxTotalConnections=1000
# Minimum number of idle connections to btcc-server 
btcc.minIdleConnections=10
# Maximum number of retries to access btcc-server 
btcc.maxTryTimes=3
# Number of worker threads accessing btcc-server 
btcc.workThreadNum=10

Enable Transactions

To enable the distributed transaction function, additional configuration needs to be added to the code:

Turn on scanning of com.baidu.btcc
Parse btcc configuration to ensure that BtccConfig objects are available
Set interceptors for RestTemplate and AsyncRestTemplate

The modified code example is shown below.

@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
@ComponentScan(basePackages = "com.baidu.btcc")
public class OrderApplication {
    @Bean
    @ConfigurationProperties("btcc")
    public BtccConfig btccConfig() {
        return new BtccConfig();
    }
 
    @LoadBalanced
    @Bean
    public RestTemplate restTemplate() {
        RestTemplate restTemplate = new RestTemplate();
        restTemplate.setInterceptors(Lists.newArrayList(new BtccRestTemplateInterceptor()));
        return restTemplate;
    }
 
    @LoadBalanced
    @Bean
    public AsyncRestTemplate asyncRestTemplate(){
        AsyncRestTemplate asyncRestTemplate = new AsyncRestTemplate();
        asyncRestTemplate.setInterceptors(Lists.newArrayList(new BtccRestTemplateAsyncInterceptor()));
        return asyncRestTemplate;
    }
 
    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }
}

Service Transformation

Add annotations to the try methods of the transaction initiator and transaction participant to create a transaction message:

@BtccTransactional(confirmMethod = "", cancelMethod = "", mode="")

Among them,

confirmMethod represents the transaction confirmation function, which is empty by default.
cancelMethod represents the transaction cancellation function, which is empty by default.
mode indicates the transaction mode. It is optional. The default is MT (MT means manual rollback, AT means automatic rollback).

Note:

@BtccTransactional can guarantee local transactions, so there is no need to explicitly add spring's @Transactional annotation.
For the transaction initiator, there is generally no need to set confirmMethod or cancelMethod.
For the transaction participant, cancelMethod must be provided in MT mode to ensure that a rollback can be performed when a transaction fails.
The try/confirm/cancel methods must be defined in the interface, and @BtccTransactional is added to the implementation method.
The same try/confirm/cancel methods must have the same input parameters.

AT mode

1.Configure the data source proxy

Use the com.baidu.btcc.client.datasource.DataSourceProxy provided by btcc. The code example is as follows.

@Configuration
@PropertySource("classpath:application.properties")
public class DatabaseConfig {
    @Value("${spring.datasource.url}")
    private String jdbcUrl;
    @Value("${spring.datasource.username}")
    private String username;
    @Value("${spring.datasource.password}")
    private String password;
    // Other configuration items 
 
    @Bean
    public DataSource dataSource() throws SQLException {
        HikariDataSource dataSource = new HikariDataSource();
        dataSource.setJdbcUrl(jdbcUrl);
        dataSource.setUsername(username);
        dataSource.setPassword(password);
        // Set other configuration items 
        return new DataSourceProxy(dataSource);
    }
}

2.Create database table

Create undo_log and btcc_global_lock tables in the database. For the SQL statements required to create the tables, please refer to Transaction Dependency Package .

3.Service use

Add annotation @BtccTransactional (mode="AT") to the transaction initiator and participant.

Note:

Currently AT mode only supports mysql database 
AT mode is suitable for relatively simple SQL. If the cancel scenario is complicated, MT mode is recommended.

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