Read-write splitting

Concept

In order to share reading/writing pressure , we need to classify data sources into different roles. The data source classified as Master is to provide writing operations, and classified as Slaves are to provide reading operations. A single Master can connect with multiple Slaves.

Done List

1. To configure Read-write splitting on single master and multiple slaves. You can use this function independently or along with sharding.
2. Provide SQL passthrough when the Read-write splitting is used independently .
3. In order to ensure data consistency, if there is a write operation, the later read operations in the same thread and the same connection are executed in the Master.
4. Sprint Namespace
5. Mandatory Master rounting strategy based in SQL Hint.

TO DO List

1. Data synchronization between Master and Slaves.
2. Inconsistency of data between Master and Slaves due to transmission delay.
3. Multiple Masters to provied writing operations.

Configuration Examples

Read-write splitting

// Create Read-write splitting DataSource which implements the DataSource interface and can be used as regular DataSource. masterDataSource, slaveDataSource0, slaveDataSource1 are all actual data sources.
Map<String, DataSource> dataSourceMap = new HashMap<>();
dataSourceMap.put("masterDataSource", masterDataSource);
dataSourceMap.put("slaveDataSource0", slaveDataSource0);
dataSourceMap.put("slaveDataSource1", slaveDataSource1);

// Generate Read-write splitting Configuration
MasterSlaveRuleConfiguration masterSlaveRuleConfig = new MasterSlaveRuleConfiguration();
masterSlaveRuleConfig.setName("ms_ds");
masterSlaveRuleConfig.setMasterDataSourceName("masterDataSource");
masterSlaveRuleConfig.getSlaveDataSourceNames().add("slaveDataSource0");
masterSlaveRuleConfig.getSlaveDataSourceNames().add("slaveDataSource1");

DataSource dataSource = MasterSlaveDataSourceFactory.createDataSource(dataSourceMap, masterSlaveRuleConfig);

Sharding + Read-write splitting

// Configure Read-write splitting DataSource which implements the DataSource interface and can be used as regular DataSource. masterDataSource, slaveDataSource0, slaveDataSource1 are all actual data sources.
Map<String, DataSource> dataSourceMap = new HashMap<>();
dataSourceMap.put("masterDataSource0", masterDataSource0);
dataSourceMap.put("slaveDataSource00", slaveDataSource00);
dataSourceMap.put("slaveDataSource01", slaveDataSource01);

dataSourceMap.put("masterDataSource1", masterDataSource1);
dataSourceMap.put("slaveDataSource10", slaveDataSource10);
dataSourceMap.put("slaveDataSource11", slaveDataSource11);

// Generate Read-write splitting Configuration
MasterSlaveRuleConfiguration masterSlaveRuleConfig0 = new MasterSlaveRuleConfiguration();
masterSlaveRuleConfig0.setName("ds_0");
masterSlaveRuleConfig0.setMasterDataSourceName("masterDataSource0");
masterSlaveRuleConfig0.getSlaveDataSourceNames().add("slaveDataSource00");
masterSlaveRuleConfig0.getSlaveDataSourceNames().add("slaveDataSource01");

MasterSlaveRuleConfiguration masterSlaveRuleConfig1 = new MasterSlaveRuleConfiguration();
masterSlaveRuleConfig1.setName("ds_1");
masterSlaveRuleConfig1.setMasterDataSourceName("masterDataSource1");
masterSlaveRuleConfig1.getSlaveDataSourceNames().add("slaveDataSource10");
masterSlaveRuleConfig1.getSlaveDataSourceNames().add("slaveDataSource11");

// Sequentially configure ShardingDataSource by using ShardingSlaveDataSourceFactory
ShardingRuleConfiguration shardingRuleConfig = new ShardingRuleConfiguration();
shardingRuleConfig.getMasterSlaveRuleConfigs().add(masterSlaveRuleConfig0);
shardingRuleConfig.getMasterSlaveRuleConfigs().add(masterSlaveRuleConfig1);

DataSource dataSource = ShardingDataSourceFactory.createDataSource(dataSourceMap, shardingRuleConfig);

The configuration example for Spring namespace

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:sharding="http://shardingsphere.io/schema/shardingjdbc/sharding"
    xmlns:masterslave="http://shardingsphere.io/schema/shardingjdbc/masterslave"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
                        http://www.springframework.org/schema/beans/spring-beans.xsd
                        http://www.springframework.org/schema/context
                        http://www.springframework.org/schema/context/spring-context.xsd
                        http://shardingsphere.io/schema/shardingjdbc/sharding
                        http://shardingsphere.io/schema/shardingjdbc/sharding/sharding.xsd
                        http://shardingsphere.io/schema/shardingjdbc/masterslave
                        http://shardingsphere.io/schema/shardingjdbc/masterslave/master-slave.xsd
                        ">
    <!-- Actual source data Configuration -->
    <bean id="dbtbl_0_master" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/dbtbl_0_master"/>
        <property name="username" value="root"/>
        <property name="password" value=""/>
    </bean>
    
    <bean id="dbtbl_0_slave_0" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/dbtbl_0_slave_0"/>
        <property name="username" value="root"/>
        <property name="password" value=""/>
    </bean>
    
    <bean id="dbtbl_0_slave_1" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/dbtbl_0_slave_1"/>
        <property name="username" value="root"/>
        <property name="password" value=""/>
    </bean>
    
    <bean id="dbtbl_1_master" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/dbtbl_1_master"/>
        <property name="username" value="root"/>
        <property name="password" value=""/>
    </bean>
    
    <bean id="dbtbl_1_slave_0" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/dbtbl_1_slave_0"/>
        <property name="username" value="root"/>
        <property name="password" value=""/>
    </bean>
    
    <bean id="dbtbl_1_slave_1" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/dbtbl_1_slave_1"/>
        <property name="username" value="root"/>
        <property name="password" value=""/>
    </bean>
    
    <!-- Read-write splitting DataSource Configuration -->
    <master-slave:data-source id="dbtbl_0" master-data-source-name="dbtbl_0_master" slave-data-source-names="dbtbl_0_slave_0, dbtbl_0_slave_1" strategy-type="ROUND_ROBIN" />
    <master-slave:data-source id="dbtbl_1" master-data-source-name="dbtbl_1_master" slave-data-source-names="dbtbl_1_slave_0, dbtbl_1_slave_1" strategy-type="ROUND_ROBIN" />
    
    <sharding:inline-strategy id="databaseStrategy" sharding-column="user_id" algorithm-expression="dbtbl_${user_id % 2}" />
    <sharding:inline-strategy id="orderTableStrategy" sharding-column="order_id" algorithm-expression="t_order_${order_id % 4}" />
    
    <sharding:data-source id="shardingDataSource">
        <sharding:sharding-rule data-source-names="dbtbl_0, dbtbl_1">
            <sharding:table-rules>
                <sharding:table-rule logic-table="t_order" actual-data-nodes="dbtbl_${0..1}.t_order_${0..3}" database-strategy-ref="databaseStrategy" table-strategy-ref="orderTableStrategy"/>
            </sharding:table-rules>
        </sharding:sharding-rule>
    </sharding:data-source>
</beans>

The example for mandatory Master routing strategy based in SQL Hint

HintManager hintManager = HintManager.getInstance();
hintManager.setMasterRouteOnly();
// Other JDBC Configuration