读写分离
一主多从：可以将查询请求均匀的分散到多个数据副本，能够进一步的提升系统的处理能力。
多主多从：不但能够提升系统的吞吐量，还能够提升系统的可用性，可以达到在任何一个数据库宕机，甚至磁盘物理损坏的情况下仍然不影响系统的正常运行。
水平分片：根据某种规则将数据分散至多个库或表中，每个分片仅包含数据的一部分。
读写分离：根据 SQL 语义的分析，将读操作和写操作分别路由至主库与从库。
支持项
不支持项
读写分离原理：
sharding-jdbc-spring-boot-starter.java 启动时， 加载 spring.shardingsphere.masterslave 配置。
SpringBootConfiguration.java 实现 EnvironmentAware.java 接口
public class SpringBootConfiguration implements EnvironmentAware{... ...}
复制代码
EnvironmentAware.java
/** * Interface to be implemented by any bean that wishes to be notified * of the {@link Environment} that it runs in. * * @author Chris Beams * @since 3.1 * @see org.springframework.core.env.EnvironmentCapable */public interface EnvironmentAware extends Aware {
/** * Set the {@code Environment} that this component runs in. */ void setEnvironment(Environment environment);
}
复制代码
Aware.java
/** * A marker superinterface indicating that a bean is eligible to be notified by the * Spring container of a particular framework object through a callback-style method. * The actual method signature is determined by individual subinterfaces but should * typically consist of just one void-returning method that accepts a single argument. * * <p>Note that merely implementing {@link Aware} provides no default functionality. * Rather, processing must be done explicitly, for example in a * {@link org.springframework.beans.factory.config.BeanPostProcessor}. * Refer to {@link org.springframework.context.support.ApplicationContextAwareProcessor} * for an example of processing specific {@code *Aware} interface callbacks. * * @author Chris Beams * @author Juergen Hoeller * @since 3.1 */public interface Aware {
}
复制代码
Bean 加载完成后执行 setEnvironment()方法，将数据源保存到 dataSourceMap。
/** * Get master-slave data source bean. * * @return data source bean * @throws SQLException SQL exception */ @Bean @Conditional(MasterSlaveRuleCondition.class) public DataSource masterSlaveDataSource() throws SQLException { return MasterSlaveDataSourceFactory.createDataSource(dataSourceMap, new MasterSlaveRuleConfigurationYamlSwapper().swap(masterSlaveRule), props.getProps()); }
... ... //将数据源保存到dataSourceMap @Override public final void setEnvironment(final Environment environment) { String prefix = "spring.shardingsphere.datasource."; for (String each : getDataSourceNames(environment, prefix)) { try { dataSourceMap.put(each, getDataSource(environment, prefix, each)); } catch (final ReflectiveOperationException ex) { throw new ShardingSphereException("Can't find datasource type!", ex); } catch (final NamingException namingEx) { throw new ShardingSphereException("Can't find JNDI datasource!", namingEx); } } }
复制代码
评论