数据库千万级分库分表和读写分离之「SpringBoot实战」

基于user表，根据id进行分库，如果id mod 2为奇数则落在ds0库，偶数则落在ds1库根据age进行分表，如果age mod 2为奇数则落在user_0表，偶数则落在user_1表

读都落在从库，写落在主库

# 可以看到配置四个数据源 分别是 主数据库两个 从数据库两个sharding.jdbc.datasource.names=master0,master1,master0slave0,master1slave0# 主第一个数据库sharding.jdbc.datasource.master0.type=com.zaxxer.hikari.HikariDataSourcesharding.jdbc.datasource.master0.hikari.driver-class-name=com.mysql.jdbc.Driversharding.jdbc.datasource.master0.jdbc-url=jdbc:mysql://192.168.0.4:3306/ds0?characterEncoding=utf-8&serverTimezone=Asia/Shanghaisharding.jdbc.datasource.master0.username=testsharding.jdbc.datasource.master0.password=12root# 主第二个数据库sharding.jdbc.datasource.master1.type=com.zaxxer.hikari.HikariDataSourcesharding.jdbc.datasource.master1.hikari.driver-class-name=com.mysql.jdbc.Driversharding.jdbc.datasource.master1.jdbc-url=jdbc:mysql://192.168.0.4:3306/ds1?characterEncoding=utf-8&serverTimezone=Asia/Shanghaisharding.jdbc.datasource.master1.username=testsharding.jdbc.datasource.master1.password=12root# 从第一个数据库sharding.jdbc.datasource.master0slave0.type=com.zaxxer.hikari.HikariDataSourcesharding.jdbc.datasource.master0slave0.hikari.driver-class-name=com.mysql.jdbc.Driversharding.jdbc.datasource.master0slave0.jdbc-url=jdbc:mysql://192.168.0.3:3306/ds0?characterEncoding=utf-8&serverTimezone=Asia/Shanghaisharding.jdbc.datasource.master0slave0.username=testsharding.jdbc.datasource.master0slave0.password=12root# 从第一个数据库sharding.jdbc.datasource.master1slave0.type=com.zaxxer.hikari.HikariDataSourcesharding.jdbc.datasource.master1slave0.hikari.driver-class-name=com.mysql.jdbc.Driversharding.jdbc.datasource.master1slave0.jdbc-url=jdbc:mysql://192.168.0.3:3306/ds1?characterEncoding=utf-8&serverTimezone=Asia/Shanghaisharding.jdbc.datasource.master1slave0.username=testsharding.jdbc.datasource.master1slave0.password=12root
# 读写分离配置# 从库的读取规则为round_robin（轮询策略），除了轮询策略，还有支持random（随机策略）sharding.jdbc.config.masterslave.load-balance-algorithm-type=round_robin# 逻辑主从库名和实际主从库映射关系# 主数据库0sharding.jdbc.config.sharding.master-slave-rules.ds0.master-data-source-name=master0# 从数据库0sharding.jdbc.config.sharding.master-slave-rules.ds0.slave-data-source-names=master0slave0# 主数据库1sharding.jdbc.config.sharding.master-slave-rules.ds1.master-data-source-name=master1# 从数据库1sharding.jdbc.config.sharding.master-slave-rules.ds1.slave-data-source-names=master1slave0

# 分库分表配置# 水平拆分的数据库（表） 配置分库 + 分表策略 行表达式分片策略# 分库策略sharding.jdbc.config.sharding.default-database-strategy.inline.sharding-column=idsharding.jdbc.config.sharding.default-database-strategy.inline.algorithm-expression=ds$->{id % 2}# 分表策略 其中user为逻辑表 分表主要取决于age行sharding.jdbc.config.sharding.tables.user.actual-data-nodes=ds$->{0..1}.user_$->{0..1}sharding.jdbc.config.sharding.tables.user.table-strategy.inline.sharding-column=age# 分片算法表达式sharding.jdbc.config.sharding.tables.user.table-strategy.inline.algorithm-expression=user_$->{age % 2}
# 主键 UUID 18位数 如果是分布式还要进行一个设置 防止主键重复#sharding.jdbc.config.sharding.tables.user.key-generator-column-name=id
# 打印操作的sql以及库表数据等sharding.jdbc.config.props.sql.show=truespring.main.allow-bean-definition-overriding=true

http://localhost:8080/insert?id=1&name=lhd&age=12http://localhost:8080/insert?id=2&name=lhd&age=13http://localhost:8080/insert?id=3&name=lhd&age=14http://localhost:8080/insert?id=4&name=lhd&age=15

相信大家也发现了,当读写分离和分库分表集成时虽然我们配置sql.show=true但是控制台最终打印不出所执行的数据源是哪个不知道是从库还是主库

获取主从库配置规则，数据源封装成MasterSlaveDataSource根据ShardingMasterSlaveRouter路由计算，得到sqlRouteResult.getRouteUnits()单元列表，然后将结果addAll添加并返回执行每个RouteUnits的时候需要获取连接，这里根据轮询负载均衡算法RoundRobinMasterSlaveLoadBalanceAlgorithm得到从库数据源拿到连接后就开始执行具体的SQL查询了，这里通过PreparedStatementHandler.execute()得到执行结果结果归并后返回

package io.shardingsphere.shardingjdbc.jdbc.core.datasource;
import io.shardingsphere.api.ConfigMapContext;import io.shardingsphere.api.config.rule.MasterSlaveRuleConfiguration;import io.shardingsphere.core.constant.properties.ShardingProperties;import io.shardingsphere.core.rule.MasterSlaveRule;import io.shardingsphere.shardingjdbc.jdbc.adapter.AbstractDataSourceAdapter;import io.shardingsphere.shardingjdbc.jdbc.core.connection.MasterSlaveConnection;import io.shardingsphere.transaction.api.TransactionTypeHolder;import java.sql.Connection;import java.sql.DatabaseMetaData;import java.sql.SQLException;import java.util.Map;import java.util.Properties;import javax.sql.DataSource;import org.slf4j.Logger;import org.slf4j.LoggerFactory;
public class MasterSlaveDataSource extends AbstractDataSourceAdapter {    private static final Logger log = LoggerFactory.getLogger(MasterSlaveDataSource.class);    private final DatabaseMetaData databaseMetaData;    private final MasterSlaveRule masterSlaveRule;    private final ShardingProperties shardingProperties;
    public MasterSlaveDataSource(Map<String, DataSource> dataSourceMap, MasterSlaveRuleConfiguration masterSlaveRuleConfig, Map<String, Object> configMap, Properties props) throws SQLException {        super(dataSourceMap);        this.databaseMetaData = this.getDatabaseMetaData(dataSourceMap);        if (!configMap.isEmpty()) {            ConfigMapContext.getInstance().getConfigMap().putAll(configMap);        }
        this.masterSlaveRule = new MasterSlaveRule(masterSlaveRuleConfig);        // 从配置文件获取配置的主从数据源        this.shardingProperties = new ShardingProperties(null == props ? new Properties() : props);    }
    // 获取主从配置关系    public MasterSlaveDataSource(Map<String, DataSource> dataSourceMap, MasterSlaveRule masterSlaveRule, Map<String, Object> configMap, Properties props) throws SQLException {        super(dataSourceMap);        this.databaseMetaData = this.getDatabaseMetaData(dataSourceMap);        if (!configMap.isEmpty()) {            ConfigMapContext.getInstance().getConfigMap().putAll(configMap);        }
        this.masterSlaveRule = masterSlaveRule;        this.shardingProperties = new ShardingProperties(null == props ? new Properties() : props);    }
    // 获取数据库元数据    private DatabaseMetaData getDatabaseMetaData(Map<String, DataSource> dataSourceMap) throws SQLException {        Connection connection = ((DataSource)dataSourceMap.values().iterator().next()).getConnection();        Throwable var3 = null;
        DatabaseMetaData var4;        try {            var4 = connection.getMetaData();        } catch (Throwable var13) {            var3 = var13;            throw var13;        } finally {            if (connection != null) {                if (var3 != null) {                    try {                        connection.close();                    } catch (Throwable var12) {                        var3.addSuppressed(var12);                    }                } else {                    connection.close();                }            }
        }
        return var4;    }
    public final MasterSlaveConnection getConnection() {        return new MasterSlaveConnection(this, this.getShardingTransactionalDataSources().getDataSourceMap(), TransactionTypeHolder.get());    }
    public DatabaseMetaData getDatabaseMetaData() {        return this.databaseMetaData;    }
    public MasterSlaveRule getMasterSlaveRule() {        return this.masterSlaveRule;    }
    public ShardingProperties getShardingProperties() {        return this.shardingProperties;    }}

package io.shardingsphere.core.rule;
import com.google.common.base.Preconditions;import io.shardingsphere.api.algorithm.masterslave.MasterSlaveLoadBalanceAlgorithm;import io.shardingsphere.api.algorithm.masterslave.MasterSlaveLoadBalanceAlgorithmType;import io.shardingsphere.api.config.rule.MasterSlaveRuleConfiguration;import java.util.Collection;
public class MasterSlaveRule {    //名称（这里是ds0和ds1）    private final String name;    //主库数据源名称（这里是ds_master_0和ds_master_1）    private final String masterDataSourceName;    //所属从库列表，key为从库数据源名称，value是真实的数据源    private final Collection<String> slaveDataSourceNames;    //主从库负载均衡算法    private final MasterSlaveLoadBalanceAlgorithm loadBalanceAlgorithm;    //主从库路由配置    private final MasterSlaveRuleConfiguration masterSlaveRuleConfiguration;

package io.shardingsphere.api.algorithm.masterslave;
import java.util.List;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.atomic.AtomicInteger;
//轮询负载均衡策略，按照每个从节点访问次数均衡public final class RoundRobinMasterSlaveLoadBalanceAlgorithm implements MasterSlaveLoadBalanceAlgorithm {    private static final ConcurrentHashMap<String, AtomicInteger> COUNT_MAP = new ConcurrentHashMap();
    public RoundRobinMasterSlaveLoadBalanceAlgorithm() {    }
    public String getDataSource(String name, String masterDataSourceName, List<String> slaveDataSourceNames) {        AtomicInteger count = COUNT_MAP.containsKey(name) ? (AtomicInteger)COUNT_MAP.get(name) : new AtomicInteger(0);        COUNT_MAP.putIfAbsent(name, count);        count.compareAndSet(slaveDataSourceNames.size(), 0);        return (String)slaveDataSourceNames.get(Math.abs(count.getAndIncrement()) % slaveDataSourceNames.size());    }}

//// Source code recreated from a .class file by IntelliJ IDEA// (powered by Fernflower decompiler)//
package io.shardingsphere.core.routing.router.masterslave;
import io.shardingsphere.core.constant.SQLType;import io.shardingsphere.core.hint.HintManagerHolder;import io.shardingsphere.core.routing.RouteUnit;import io.shardingsphere.core.routing.SQLRouteResult;import io.shardingsphere.core.rule.MasterSlaveRule;import java.beans.ConstructorProperties;import java.util.ArrayList;import java.util.Collection;import java.util.Iterator;import java.util.LinkedList;
public final class ShardingMasterSlaveRouter {    private final Collection<MasterSlaveRule> masterSlaveRules;
    // 得到最终的sql路由    public SQLRouteResult route(SQLRouteResult sqlRouteResult) {        Iterator var2 = this.masterSlaveRules.iterator();
        while(var2.hasNext()) {            MasterSlaveRule each = (MasterSlaveRule)var2.next();            this.route(each, sqlRouteResult);        }
        return sqlRouteResult;    }
    //进行计算筛选得到最终sql路由    private void route(MasterSlaveRule masterSlaveRule, SQLRouteResult sqlRouteResult) {        Collection<RouteUnit> toBeRemoved = new LinkedList();        Collection<RouteUnit> toBeAdded = new LinkedList();        Iterator var5 = sqlRouteResult.getRouteUnits().iterator();
        while(var5.hasNext()) {            RouteUnit each = (RouteUnit)var5.next();            if (masterSlaveRule.getName().equalsIgnoreCase(each.getDataSourceName())) {                toBeRemoved.add(each);                if (this.isMasterRoute(sqlRouteResult.getSqlStatement().getType())) {                    MasterVisitedManager.setMasterVisited();                    toBeAdded.add(new RouteUnit(masterSlaveRule.getMasterDataSourceName(), each.getSqlUnit()));                } else {                    toBeAdded.add(new RouteUnit(masterSlaveRule.getLoadBalanceAlgorithm().getDataSource(masterSlaveRule.getName(), masterSlaveRule.getMasterDataSourceName(), new ArrayList(masterSlaveRule.getSlaveDataSourceNames())), each.getSqlUnit()));                }            }        }        //路由移除(查询时 移除所有主库)        sqlRouteResult.getRouteUnits().removeAll(toBeRemoved);        //添加从库/主库 具体事件定        sqlRouteResult.getRouteUnits().addAll(toBeAdded);    }
    // 判断是不是主库    private boolean isMasterRoute(SQLType sqlType) {        return SQLType.DQL != sqlType || MasterVisitedManager.isMasterVisited() || HintManagerHolder.isMasterRouteOnly();    }
    @ConstructorProperties({"masterSlaveRules"})    public ShardingMasterSlaveRouter(Collection<MasterSlaveRule> masterSlaveRules) {        this.masterSlaveRules = masterSlaveRules;    }}

private boolean isMasterRoute(SQLType sqlType) {        return SQLType.DQL != sqlType || MasterVisitedManager.isMasterVisited() || HintManagerHolder.isMasterRouteOnly();    }

SQL语言共分为四大类：数据查询语言DQL，数据操纵语言DML，数据定义语言DDL，数据控制语言DCL。