nacos只支持mysql的原因分析

本篇文章给大家分享《nacos只支持mysql的原因分析》，覆盖了数据库的常见基础知识，其实一个语言的全部知识点一篇文章是不可能说完的，但希望通过这些问题，让读者对自己的掌握程度有一定的认识(B 数)，从而弥补自己的不足，更好的掌握它。

什么是Nacos

英文全称Dynamic Naming and Configuration Service，Na为naming/nameServer即注册中心,co为configuration即注册中心，service是指该注册/配置中心都是以服务为核心。服务在nacos是一等公民

没看源码之前,觉得很离谱,为啥只能限制数据库为mysql,按道理来说,nacos用了JdbcTemplate,可以适配很多数据库才是

最近看了nacos的源码,发现其中有很多硬编码,才明白原因

nacos的数据源获取都是通过com.alibaba.nacos.config.server.service.datasource.DynamicDataSource来获取的

在获取数据源时,根据配置判断你到底是使用内置的本地数据库还是外部的数据库(mysql)

public synchronized DataSourceService getDataSource() {
    try {

        // Embedded storage is used by default in stand-alone mode
        // In cluster mode, external databases are used by default
        // 根据System.getProperty("nacos.standalone")来判断你到底是不是standalone模式
        // standalone模式,使用内置数据库
        if (PropertyUtil.isEmbeddedStorage()) {
            if (localDataSourceService == null) {
                localDataSourceService = new LocalDataSourceServiceImpl();
                localDataSourceService.init();
            }
            return localDataSourceService;
        } else {
            // 如果不是standalone,直接创建外部的数据源
            if (basicDataSourceService == null) {
                basicDataSourceService = new ExternalDataSourceServiceImpl();
                basicDataSourceService.init();
            }
            return basicDataSourceService;
        }
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}

外部数据源com.alibaba.nacos.config.server.service.datasource.ExternalDataSourceServiceImpl.init()

@Override
public void init() {
    queryTimeout = ConvertUtils.toInt(System.getProperty("QUERYTIMEOUT"), 3);
    jt = new JdbcTemplate();
    // Set the maximum number of records to prevent memory expansion
    jt.setMaxRows(50000);
    jt.setQueryTimeout(queryTimeout);
    testMasterJT = new JdbcTemplate();
    testMasterJT.setQueryTimeout(queryTimeout);
    testMasterWritableJT = new JdbcTemplate();
    // Prevent the login interface from being too long because the main library is not available
    testMasterWritableJT.setQueryTimeout(1);
    //  Database health check
    testJtList = new ArrayList();
    isHealthList = new ArrayList();
    tm = new DataSourceTransactionManager();
    tjt = new TransactionTemplate(tm);
    // Transaction timeout needs to be distinguished from ordinary operations.
    tjt.setTimeout(TRANSACTION_QUERY_TIMEOUT);
    // 判断到底是是不是用外部数据库
    // 这个可以在com.alibaba.nacos.config.server.utils.PropertyUtil#loadSetting中看到
    // setUseExternalDB("mysql".equalsIgnoreCase(getString("spring.datasource.platform", "")));
    // 好家伙,直接判断配置的是不是mysql,是mysql那就是外部数据库,进行reload,不是,那就不管了
    if (PropertyUtil.isUseExternalDB()) {
        try {
            reload();
        } catch (IOException e) {
            e.printStackTrace();
            throw new RuntimeException(DB_LOAD_ERROR_MSG);
        }
        if (this.dataSourceList.size() > DB_MASTER_SELECT_THRESHOLD) {
            ConfigExecutor.scheduleConfigTask(new SelectMasterTask(), 10, 10, TimeUnit.SECONDS);
        }
        ConfigExecutor.scheduleConfigTask(new CheckDbHealthTask(), 10, 10, TimeUnit.SECONDS);
    }
}

在com.alibaba.nacos.config.server.service.datasource.ExternalDataSourceServiceImpl#reload中,我们可以看到

@Override
public synchronized void reload() throws IOException {
    try {
        // 根据配置文件,构建数据源集合
        dataSourceList = new ExternalDataSourceProperties()
            .build(EnvUtil.getEnvironment(), (dataSource) -> {
                JdbcTemplate jdbcTemplate = new JdbcTemplate();
                jdbcTemplate.setQueryTimeout(queryTimeout);
                jdbcTemplate.setDataSource(dataSource);
                testJtList.add(jdbcTemplate);
                isHealthList.add(Boolean.TRUE);
            });
        new SelectMasterTask().run();
        new CheckDbHealthTask().run();
    } catch (RuntimeException e) {
        FATAL_LOG.error(DB_LOAD_ERROR_MSG, e);
        throw new IOException(e);
    }
}

在com.alibaba.nacos.config.server.service.datasource.ExternalDataSourceProperties#build中

List build(Environment environment, Callback callback) {
    List dataSources = new ArrayList();
    // 把胚子信息绑定到当前的ExternalDataSourceProperties对象,赋值操作
    // 因为外面是直接new出来的,需要对属性根据文件进行赋值
    Binder.get(environment).bind("db", Bindable.ofInstance(this));
    Preconditions.checkArgument(Objects.nonNull(num), "db.num is null");
    Preconditions.checkArgument(CollectionUtils.isNotEmpty(user), "db.user or db.user.[index] is null");
    Preconditions.checkArgument(CollectionUtils.isNotEmpty(password), "db.password or db.password.[index] is null");
    // 可以配置多个数据库
    for (int index = 0; index = currentSize, "db.url.%s is null", index);
        // 拿到spring.datasource.xxx一堆,这个针对所有的数据源都适用
        DataSourcePoolProperties poolProperties = DataSourcePoolProperties.build(environment);
        // 为每一个数据源进行单独的url,user,password进行替换
        poolProperties.setDriverClassName(JDBC_DRIVER_NAME);
        poolProperties.setJdbcUrl(url.get(index).trim());
        poolProperties.setUsername(getOrDefault(user, index, user.get(0)).trim());
        poolProperties.setPassword(getOrDefault(password, index, password.get(0)).trim());
        HikariDataSource ds = poolProperties.getDataSource();
        ds.setConnectionTestQuery(TEST_QUERY);
        dataSources.add(ds);
        callback.accept(ds);
    }
    Preconditions.checkArgument(CollectionUtils.isNotEmpty(dataSources), "no datasource available");
    return dataSources;
}

这个整体还行,但是为啥JDBC_DRIVER_NAME是硬编码呢,代码中清晰看到

private static final String JDBC_DRIVER_NAME = "com.mysql.cj.jdbc.Driver";

到这已经一目了然,代码中硬编码了mysql,driver也没法改,所以根本没法更换数据库驱动,有点骚,而且com.mysql.cj.jdbc.Driver是mysql8的驱动,对mysql版本是有要求的

再看其他部分,也可以发现大量的硬编码,例如com.alibaba.nacos.config.server.auth.ExternalUserPersistServiceImpl

public class ExternalUserPersistServiceImpl implements UserPersistService {
    
    @Autowired
    private ExternalStoragePersistServiceImpl persistService;
    
    private JdbcTemplate jt;
    
    @PostConstruct
    protected void init() {
        jt = persistService.getJdbcTemplate();
    }
    
    /**
     * Execute create user operation.
     *
     * @param username username string value.
     * @param password password string value.
     */
    public void createUser(String username, String password) {
        String sql = "INSERT into users (username, password, enabled) VALUES (?, ?, ?)";
        
        try {
            jt.update(sql, username, password, true);
        } catch (CannotGetJdbcConnectionException e) {
            LogUtil.FATAL_LOG.error("[db-error] " + e.toString(), e);
            throw e;
        }
    }
    
    /**
     * Execute delete user operation.
     *
     * @param username username string value.
     */
    public void deleteUser(String username) {
        String sql = "DELETE from users WHERE username=?";
        try {
            jt.update(sql, username);
        } catch (CannotGetJdbcConnectionException e) {
            LogUtil.FATAL_LOG.error("[db-error] " + e.toString(), e);
            throw e;
        }
    }
    
    /**
     * Execute update user password operation.
     *
     * @param username username string value.
     * @param password password string value.
     */
    public void updateUserPassword(String username, String password) {
        try {
            jt.update("UPDATE users SET password = ? WHERE username=?", password, username);
        } catch (CannotGetJdbcConnectionException e) {
            LogUtil.FATAL_LOG.error("[db-error] " + e.toString(), e);
            throw e;
        }
    }
    
    /**
     * Execute find user by username operation.
     *
     * @param username username string value.
     * @return User model.
     */
    public User findUserByUsername(String username) {
        String sql = "SELECT username,password FROM users WHERE username=? ";
        try {
            return this.jt.queryForObject(sql, new Object[] {username}, USER_ROW_MAPPER);
        } catch (CannotGetJdbcConnectionException e) {
            LogUtil.FATAL_LOG.error("[db-error] " + e.toString(), e);
            throw e;
        } catch (EmptyResultDataAccessException e) {
            return null;
        } catch (Exception e) {
            LogUtil.FATAL_LOG.error("[db-other-error]" + e.getMessage(), e);
            throw new RuntimeException(e);
        }
    }
    
    public Page getUsers(int pageNo, int pageSize) {
        
        PaginationHelper helper = persistService.createPaginationHelper();
        
        String sqlCountRows = "select count(*) from users where ";
        String sqlFetchRows = "select username,password from users where ";
        
        String where = " 1=1 ";
        
        try {
            Page pageInfo = helper
                    .fetchPage(sqlCountRows + where, sqlFetchRows + where, new ArrayList().toArray(), pageNo,
                            pageSize, USER_ROW_MAPPER);
            if (pageInfo == null) {
                pageInfo = new Page();
                pageInfo.setTotalCount(0);
                pageInfo.setPageItems(new ArrayList());
            }
            return pageInfo;
        } catch (CannotGetJdbcConnectionException e) {
            LogUtil.FATAL_LOG.error("[db-error] " + e.toString(), e);
            throw e;
        }
    }
    @Override
    public List findUserLikeUsername(String username) {
        String sql = "SELECT username FROM users WHERE username like '%' ? '%'";
        List users = this.jt.queryForList(sql, new String[]{username}, String.class);
        return users;
    }
}

几乎所有的sql都是硬编码....所以要改造成其他数据库工作量还是非常大的

本篇关于《nacos只支持mysql的原因分析》的介绍就到此结束啦，但是学无止境，想要了解学习更多关于数据库的相关知识，请关注golang学习网公众号！