1.主从库配置

1.1 主库配置binary log

vim /etc/my.cnf
在[mysqld]中添加

server-id=1
log-bin=master-bin
log-bin-index=master-bin.index

重启：

service mysqld restart

登录输入库查看：

mysql> show master status;
+-------------------+----------+--------------+------------------+-------------------+
| File              | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------+----------+--------------+------------------+-------------------+
| master-bin.000001 |      155 |              |                  |                   |
+-------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

主库创建用户repl：

create user 'repl'@'从库ip' identified by '密码';

授权

grant replication slave on *.* to 'repl'@'从库ip';
flush privileges;

1.2 从库配置relay log

vim /etc/my.cnf
在[mysqld]中添加

server-id=2
relay-log=slave-relay-bin
relay-log-index=slave-relay-bin.index

重启mysql

从库配置：

change master to master_host='主库ip',master_port=3306,master_user='repl',master_password='密码',master_log_file='master-bin.000001',master_log_pos=0;

start slave;

mysql> show slave status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 119.3.135.196
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: master-bin.000001
          Read_Master_Log_Pos: 877
               Relay_Log_File: slave-relay-bin.000003
                Relay_Log_Pos: 323
        Relay_Master_Log_File: master-bin.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 877
              Relay_Log_Space: 1469
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 1
                  Master_UUID: abecae31-0dc2-11ea-b31e-fa163eea918c
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind: 
      Last_IO_Error_Timestamp: 
     Last_SQL_Error_Timestamp: 
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
           Retrieved_Gtid_Set: 
            Executed_Gtid_Set: 
                Auto_Position: 0
         Replicate_Rewrite_DB: 
                 Channel_Name: 
           Master_TLS_Version: 
       Master_public_key_path: 
        Get_master_public_key: 0
            Network_Namespace: 
1 row in set (0.00 sec)

ERROR: 
No query specified

1.3 同步测试

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| o2o                |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> create database test;
Query OK, 1 row affected (0.01 sec)

mysql> drop database test;
Query OK, 0 rows affected (0.01 sec)

mysql> show master status;
+-------------------+----------+--------------+------------------+-------------------+
| File              | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+-------------------+----------+--------------+------------------+-------------------+
| master-bin.000001 |     1243 |              |                  |                   |
+-------------------+----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

mysql> show slave status \G;
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: 119.3.135.196
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: master-bin.000001
          Read_Master_Log_Pos: 1243
               Relay_Log_File: slave-relay-bin.000003
                Relay_Log_Pos: 689
        Relay_Master_Log_File: master-bin.000001
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB: 
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table: 
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 1243
              Relay_Log_Space: 1835
              Until_Condition: None

可以看到从库： Read_Master_Log_Pos: 1243，表明已经跟上了主库的步伐。

1.4 几个注意事项

• 1）position主从库一致表明同步好了
• 2）不要向从库写数据
• 3）从库的版本 >= 主库的版本 （向后兼容）

2.读写分离

2.1 核心配置

    <!-- 2.数据库连接池 -->
    <bean id="abstractDataSource" abstract="true"
          class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
        <!-- c3p0连接池的私有属性 -->
        <property name="maxPoolSize" value="30"/>
        <property name="minPoolSize" value="10"/>

        <!-- 关闭连接后不自动commit -->
        <property name="autoCommitOnClose" value="false"/>
        <!-- 获取连接超时时间 -->
        <property name="checkoutTimeout" value="10000"/>
        <!-- 当获取连接失败重试次数 -->
        <property name="acquireRetryAttempts" value="2"/>
    </bean>

    <bean id="master" parent="abstractDataSource">
        <!-- 配置连接池属性 -->
        <property name="driverClass" value="${jdbc.driver}" />
        <property name="jdbcUrl" value="${jdbc.master.url}" />
        <property name="user" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
    </bean>

    <bean id="slave" parent="abstractDataSource">
        <!-- 配置连接池属性 -->
        <property name="driverClass" value="${jdbc.driver}" />
        <property name="jdbcUrl" value="${jdbc.slave.url}" />
        <property name="user" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
    </bean>

    <!--配置动态数据源，targetDataSources就是路由数据源所对应的名称-->
    <bean id="dynamicDataSource" class="com.imooc.o2o.dao.split.DynamicDataSource">
        <property name="targetDataSources">
            <map>
                <entry value-ref="master" key="master"></entry>
                <entry value-ref="slave" key="slave"></entry>
            </map>
        </property>
    </bean>

    <!--将dynamicDataSource放入懒加载中（程序执行时才决定使用哪个dataSource）-->
    <bean id="dataSource"
          class="org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy">
        <property name="targetDataSource">
            <ref bean="dynamicDataSource"/>
        </property>
    </bean>

jdbc.properties：

jdbc.master.url=
jdbc.slave.url=

2.2 DynamicDataSource

public class DynamicDataSource extends AbstractRoutingDataSource {
    @Override
    protected Object determineCurrentLookupKey() {
        return DynamicDataSourceHolder.getDBType();
    }
}

public class DynamicDataSourceHolder {
    private static Logger logger = LoggerFactory.getLogger(DynamicDataSourceHolder.class);
    private static ThreadLocal<String> contextHolder = new ThreadLocal<>();
    public static final String DB_MASTER = "master";
    public static final String DB_SLAVE = "slave";

    public static String getDBType() {
        String db = contextHolder.get();
        if (db == null) {
            db = DB_MASTER;
        }
        return db;
    }

    public static void setDBType(String str) {
        logger.debug("所使用的数据源为：" + str);
        contextHolder.set(str);
    }

    /**
     * 清理连接类型
     */
    public static void clearDBType() {
        contextHolder.remove();
    }
}

2.3 拦截器

@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class}),
@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class,
        RowBounds.class, ResultHandler.class})})
public class DynamicDataSourceInterceptor implements Interceptor {
    private static Logger logger = LoggerFactory.getLogger(DynamicDataSourceInterceptor.class);
    private static final String REGEX = ".*insert\\u0020.*|.*delete\\u0020.*|.*update\\u0020.*";

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 当前是不是事务管理的
        boolean synchronizationActive = TransactionSynchronizationManager.isActualTransactionActive();
        // 获取sql的参数
        Object[] objects = invocation.getArgs();
        // 表明是哪种类型的语句
        MappedStatement ms = (MappedStatement) objects[0];
        String lookupKey;

        if (!synchronizationActive) {
            // 读方法
            if (ms.getSqlCommandType().equals(SqlCommandType.SELECT)) {
                // selectkey为自增id查询主键(SELECT LAST_INSERT_ID())方法，使用主库
                if (ms.getId().contains(SelectKeyGenerator.SELECT_KEY_SUFFIX)) {
                    lookupKey = DynamicDataSourceHolder.DB_MASTER;
                } else {
                    BoundSql boundSql = ms.getSqlSource().getBoundSql(objects[1]);
                    String sql = boundSql.getSql().toLowerCase(Locale.CHINA).replace("[\\t\\n\\r]", " ");
                    if (sql.matches(REGEX)) {
                        lookupKey = DynamicDataSourceHolder.DB_MASTER;
                    } else {
                        lookupKey = DynamicDataSourceHolder.DB_SLAVE;
                    }
                }
            } else {
                lookupKey = DynamicDataSourceHolder.DB_MASTER;
            }
        } else {
            lookupKey = DynamicDataSourceHolder.DB_MASTER;
        }
        logger.debug("设置方法[{}] use [{}] Strategy, SqlCommanType [{}]..", ms.getId(), lookupKey,
                ms.getSqlCommandType().name());
        DynamicDataSourceHolder.setDBType(lookupKey);
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        // Executor代表增删改查操作
        if (target instanceof Executor) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }

    @Override
    public void setProperties(Properties properties) {

    }
}

在mybatis-config.xml中添加拦截器：

    </settings>
    <plugins>
        <plugin interceptor="com.imooc.o2o.dao.split.DynamicDataSourceInterceptor"></plugin>
    </plugins>
</configuration>