【开发进阶】——MySQL配置主从同步，代码层实现读写分离

深碍√TFBOYSˉ_ 2022-05-18 03:23 108阅读 0赞

\#前提  
1、服务器环境 centos7  
2、MySQL5.7  
3、在两台机器完成MySQL的安装相关内容  
4、框架ssm+数据连接池druid+p6spy

\#配置主从同步

主服务相关配置  
1、在my.cnf中设置如下内容

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

2、创建用户，并授权

create user repl;
    grant replication slave on *.* to 'repl'@'从服务器的ip地址' identified by 'mysql';
    flush privileges;

3、查看主服务相关状态

show master status;

查询内容结果如下，牢记标注位置，下文需要用到  
![这里写图片描述][70]

从服务相关配置  
1、在my.cnf中设置如下内容

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

2、与主服务器绑定，并开启主从同步

//master_log_file配置就是主服务器中标注的内容，偏移值，按照自己的实际情况填写
    change master to master_host='主服务器ip地址',master_port=3306,master_user='repl',master_password='mysql',master_log_file='master-bin.000001',master_log_pos=0;
    //开启主从同步
    start slave;

3、查看主从同步状态

show slave status;

查看下图中标注处是否有错误，如图，则证明主从同步已经配置好了  
![这里写图片描述][70 1]

--------------------

\#代码层实现读写分离  
1、获取数据库类型

public class DynamicDataSourceHolder {
        private static final Logger log = 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;
        }
    
        /**
         * 设置线程的dbType
         * @param str
         */
        public static void setDbType(String str) {
            log.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、编写拦截器

@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 final Logger log = LoggerFactory.getLogger(DynamicDataSourceInterceptor.class);
        private static final String REGEX = ".*insert\\u0020.*|.*delete\\u0020.*|.*update\\u0020.*";
    
        @Override
        public Object intercept(Invocation invocation) throws Throwable {
            boolean synchronizationActive = TransactionSynchronizationManager.isActualTransactionActive();
            Object[] objects = invocation.getArgs();
            MappedStatement ms = (MappedStatement) objects[0];
            String lookupKey = DynamicDataSourceHolder.DB_MASTER;
            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).replaceAll("\\t\\n\\r", " ");
                        if (sql.matches(REGEX)) {
                            lookupKey = DynamicDataSourceHolder.DB_MASTER;
                        } else {
                            lookupKey = DynamicDataSourceHolder.DB_SLAVE;
                        }
                    }
                } else {
                    lookupKey = DynamicDataSourceHolder.DB_MASTER;
                }
            }
            log.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) {
            if (target instanceof Executor) {
                return Plugin.wrap(target, this);
            } else {
                return target;
            }
        }
        @Override
        public void setProperties(Properties properties) {
    
        }
    }

3、数据源

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

4、配置多数据源

<context:property-placeholder location="classpath:db.properties"/>
        
        <bean id="abstractDataSourceDefault" abstract="true" class="com.alibaba.druid.pool.DruidDataSource" destroy-method="close">
            
            <property name="initialSize" value="**"/>
            <property name="maxActive" value="**" />
            <property name="minIdle" value="**" />
            
            <property name="maxWait" value="**" />
            
            <property name="validationQuery" value="select 'x'"/>
            
            <property name="validationQueryTimeout" value="**"/>
            
            <property name="timeBetweenEvictionRunsMillis" value="**"/>
            
            <property name="testOnBorrow" value="true"/>
            
            <property name="testOnReturn" value="true"/>
            
            <property name="testWhileIdle" value="true"/>
            
            <property name="minEvictableIdleTimeMillis" value="**"/>
            
            <property name="poolPreparedStatements" value="false"/>
            
            <property name="maxPoolPreparedStatementPerConnectionSize" value="-1"/>
            
            <property name="filters" value="stat" />
            
            
            
            
            
            
            
        </bean>
        
        <bean id="master" parent="abstractDataSourceDefault">
            <property name="url" value="${jdbc.master.url}" />
            <property name="username" value="${jdbc.username}" />
            <property name="password" value="${jdbc.password}" />
        </bean>
    	
        <bean id="slave" parent="abstractDataSourceDefault">
            <property name="url" value="${jdbc.slave.url}" />
            <property name="username" value="${jdbc.username}" />
            <property name="password" value="${jdbc.password}" />
        </bean>
    
        <bean id="dymicDataSources" class="com.***.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>
    
        <bean id="dataSourceDefault" class="org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy">
            <property name="targetDataSource">
                <ref bean="dymicDataSources"/>
            </property>
        </bean>
        
        <bean id="dataSource" class="com.p6spy.engine.spy.P6DataSource">
            <constructor-arg>
                <ref bean="dataSourceDefault"/>
            </constructor-arg>
        </bean>

\#总结  
    到这为止，实现主从同步以及代码层的读写分离，其实比较简单，遇到问题不要害怕，解决就行了

[70]: /images/20220518/e8faf2272e3e42b1ab04bfaf7b6c5adc.png
[70 1]: /images/20220518/b8dfe45b382b4632a441512965d78855.png