nacos只支持mysql的原因分析

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<JdbcTemplate>();
    isHealthList = new ArrayList<Boolean>();
    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<HikariDataSource> build(Environment environment, Callback<HikariDataSource> callback) {
    List<HikariDataSource> 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 < num; index++) {
        int currentSize = index + 1;
        Preconditions.checkArgument(url.size() >= 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<User> getUsers(int pageNo, int pageSize) {

        PaginationHelper<User> helper = persistService.createPaginationHelper();

        String sqlCountRows = "select count(*) from users where ";
        String sqlFetchRows = "select username,password from users where ";

        String where = " 1=1 ";

        try {
            Page<User> pageInfo = helper
                    .fetchPage(sqlCountRows + where, sqlFetchRows + where, new ArrayList<String>().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<String> findUserLikeUsername(String username) {
        String sql = "SELECT username FROM users WHERE username like '%' ? '%'";
        List<String> 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

到此这篇关于为什么nacos只支持mysql的文章就介绍到这了,更多相关nacos只支持mysql内容请搜索我们以前的文章或继续浏览下面的相关文章希望大家以后多多支持我们！