高版本 MySQL 驱动的 DNS 陷阱-洪萨配资

背景

项目使用 OceanBase 数据库，并通过 ShardingSphere JDBC 实现分表。由于 ShardingSphere 当前不支持jdbc:oceanbase:协议，我们在代码中将连接串替换为jdbc:mysql并引入 MySQL 驱动

<dependency> <groupId>com.oceanbase</groupId> <artifactId>oceanbase-client</artifactId> <version>2.4.8</version> </dependency> <dependency> <groupId>org.apache.shardingsphere</groupId> <artifactId>shardingsphere-jdbc</artifactId> <version>5.5.2</version> </dependency> <dependency> <groupId>com.mysql</groupId> <artifactId>mysql-connector-j</artifactId>  <version>8.4.0</version> </dependency>

数据源配置如下（关键部分）

spring: datasource: driver-class-name: com.oceanbase.jdbc.Driver url: jdbc:oceanbase:loadbalance://IP:PORT/test?... druid: initial-size: 8 max-active: 30 min-idle: 8

@Configuration public class ShardingDataSourceConfiguration { @Value("${spring.datasource.url}") private String url; @Value("${spring.datasource.username}") private String username; @Value("${spring.datasource.password}") private String password; private Map<String, DataSource> createDataSourceMap() { Map<String, DataSource> dataSourceMap = new HashMap<>(); DruidDataSource dataSource1 = new DruidDataSource(); dataSource1.setDriverClassName("com.mysql.cj.jdbc.Driver"); url = url.replace("jdbc:oceanbase", "jdbc:mysql"); dataSource1.setUrl(url); dataSource1.setUsername(username); dataSource1.setPassword(password); dataSource1.setInitialSize(8); dataSource1.setMaxActive(30); dataSource1.setMinIdle(8); dataSourceMap.put("ds_0", dataSource1); return dataSourceMap; } @Bean("shardingDataSource") public DataSource dataSource() throws SQLException { Properties props = new Properties(); props.put("sql-show", false); return ShardingSphereDataSourceFactory.createDataSource( createDataSourceMap(), Collections.singletonList(createShardingRuleConfiguration()), props ); } }

同时，项目中还有一个未经过 ShardingSphere 的原生 OceanBase 数据源

@Configuration public class DataSourceConfiguration { @Bean(name = "logAnalysisDataSource") public DataSource logAnalysisDataSource() { // com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder // 使用 spring.datasource 配置来创建数据库连接池 DruidDataSource druidDataSource = DruidDataSourceBuilder.create().build(); druidDataSource.setSocketTimeout(180000); druidDataSource.setConnectTimeout(180000); return druidDataSource; } }

问题现象

启动项目时，发现@Bean("shardingDataSource")所对应的 DruidDataSource 初始化时间特别长，但@Bean(name = "logAnalysisDataSource")所对应的 DruidDataSource 初始化却很快

[2026-02-07 17:47:32.417] [INFO ] [com.zaxxer.hikari.HikariDataSource] [80] - [HikariPool-1 - Starting...] [2026-02-07 17:47:32.739] [INFO ] [com.zaxxer.hikari.HikariDataSource] [82] - [HikariPool-1 - Start completed.] [2026-02-07 17:50:22.107] [INFO ] [com.alibaba.druid.pool.DruidDataSource] [1007] - [{dataSource-1} inited] [2026-02-07 17:50:34.454] [INFO ] [com.alibaba.druid.pool.DruidDataSource] [1007] - [{dataSource-2} inited] [2026-02-07 17:50:35.840] [INFO ] [com.xxx.WebApplication] [61] - [Started WebApplication in 188.327 seconds (JVM running for 189.054)]

日志中的 HikariDataSource 是 ShardingSphere JDBC 用于操作元数据的内部连接池，其初始化完成至 DruidDataSource#init 执行前的耗时可忽略不计

启动日志中，{dataSource-1}对应@Bean("shardingDataSource")，{dataSource-2}对应@Bean(name = "logAnalysisDataSource")

从日志可以看出，@Bean("shardingDataSource")这个 DruidDataSource 对象的初始化时间为 2 分 50 秒，而@Bean(name = "logAnalysisDataSource")这个 DruidDataSource 对象的初始化时间为 12 秒，而两者唯一的区别在于底层 JDBC 驱动

备注：因项目开发环境位于内网，且数据库部署于不同地域，网络延迟较高，数据库连接池初始化耗时 12 秒属正常范围

跟踪 Druid 源码发现，耗时主要集中在createPhysicalConnection()方法执行过程中，该方法负责建立底层物理数据库连接

public class DruidDataSource extends DruidAbstractDataSource implements DruidDataSourceMBean, ManagedDataSource, Referenceable, Closeable, Cloneable, ConnectionPoolDataSource, MBeanRegistration { public void init() throws SQLException { try { if (createScheduler != null && asyncInit) { for (int i = 0; i < initialSize; ++i) { submitCreateTask(true); } } else if (!asyncInit) { // init connections while (poolingCount < initialSize) { try { // 慢在这里 PhysicalConnectionInfo pyConnectInfo = createPhysicalConnection(); DruidConnectionHolder holder = new DruidConnectionHolder(this, pyConnectInfo); connections[poolingCount++] = holder; } catch (SQLException ex) { } } } } finally { inited = true; lock.unlock(); if (init && LOG.isInfoEnabled()) { String msg = "{dataSource-" + this.getID(); if (this.name != null && !this.name.isEmpty()) { msg += ","; msg += this.name; } msg += "} inited"; // 打印日志 LOG.info(msg); } } } }

继续跟踪源码，最终定位到问题源于 MySQL 驱动在创建连接时调用InetSocketAddress.getHostName()进行反向 DNS 解析，耗时显著，导致连接初始化缓慢

完整的链路：DruidAbstractDataSource#createPhysicalConnection=> ... =>com.mysql.cj.jdbc.ConnectionImpl#getInstance(HostInfo hostInfo)=>ConnectionImpl构造方法

package com.mysql.cj.jdbc; public class ConnectionImpl implements JdbcConnection, SessionEventListener, Serializable { public ConnectionImpl(HostInfo hostInfo) throws SQLException { try { SocketAddress socketAddress = this.session.getRemoteSocketAddress(); if (InetSocketAddress.class.isInstance(socketAddress)) { InetSocketAddress inetSocketAddress = (InetSocketAddress) socketAddress; // 关键 this.connectionSpan.setAttribute( TelemetryAttribute.NETWORK_PEER_ADDRESS, // 获取 hostname 字段值 inetSocketAddress.getHostName() ); } } } }

package java.net; public class InetSocketAddress extends SocketAddress { private final transient InetSocketAddressHolder holder; // Private implementation class pointed to by all public methods. private static class InetSocketAddressHolder { // The hostname of the Socket Address private String hostname; // The IP address of the Socket Address private InetAddress addr; // The port number of the Socket Address private int port; private InetSocketAddressHolder(String hostname, InetAddress addr, int port) { this.hostname = hostname; this.addr = addr; this.port = port; } private int getPort() { return port; } private InetAddress getAddress() { return addr; } private String getHostName() { if (hostname != null) return hostname; if (addr != null) // ⚠️ 触发反向 DNS 解析！内网无 DNS 服务 → 阻塞超时 return addr.getHostName(); return null; } } /** * Gets the {@code hostname}. * Note: This method may trigger a name service reverse lookup if the * address was created with a literal IP address. * * @return the hostname part of the address. */ public final String getHostName() { return holder.getHostName(); } }

在网上搜了下，有如下的文章片段

# 解决 Linux 上 Java 获取 hostname 很慢的问题在 Linux 环境中运行 Java 应用时，有时会遇到 `InetAddress.getLocalHost().getHostName()` 方法执行缓慢的问题，严重影响应用启动速度 ## 问题原因 Java 在调用 `getHostName()` 时，会尝试对本机 IP 地址进行**反向 DNS 解析（PTR 查询）**，以获取主机名，若 DNS 服务器不可达、无 PTR 记录或网络延迟高，该操作将长时间阻塞 ## 常见场景 - Docker / K8S 容器中未配置 DNS - 内部网络无反向解析支持 - 使用纯 IP 地址连接数据库（如 MySQL）

真相大白！我的项目开发环境位于公司内网，完全无法访问外网，更无外部 DNS 服务支持，以下为尝试 ping 外网的输出结果

$ ping www.baidu.com Ping 请求找不到主机 www.baidu.com。请检查该名称，然后重试。

那怎么解释@Bean(name = "logAnalysisDataSource")这个 DruidDataSource 对象的初始化时间仅 12 秒呢？这是因为它使用的是jdbc:oceanbase协议与oceanbase-client驱动，这个驱动在连接建立过程中不会调用InetSocketAddress.getHostName()方法（没看源码，仅为猜测，但八九不离十）

如何解决这个问题呢？有如下两种方法（网上说添加几个 JVM 参数就能解决，实测无效）

上述问题在 SpringBoot 3 Druid 启动慢排查，SpringBoot 启动慢、服务偶发接口慢查询，MySQL Connector-j 9.0.0 版本问题，getHostName() 请求慢这篇文章中也提到了

解决办法一：修改 hosts 文件

修改 hosts 文件，添加域名映射

10.xxx.xxx.146 www.define.com

从启动日志可以看出，问题完美解决

[2026-02-07 18:44:04.258] [INFO ] [com.zaxxer.hikari.HikariDataSource] [80] - [HikariPool-1 - Starting...] [2026-02-07 18:44:04.582] [INFO ] [com.zaxxer.hikari.HikariDataSource] [82] - [HikariPool-1 - Start completed.] [2026-02-07 18:44:09.426] [INFO ] [com.alibaba.druid.pool.DruidDataSource] [1007] - [{dataSource-1} inited] [2026-02-07 18:44:22.180] [INFO ] [com.alibaba.druid.pool.DruidDataSource] [1007] - [{dataSource-2} inited] [2026-02-07 18:44:23.552] [INFO ] [com.xxx.WebApplication] [61] - [Started WebApplication in 24.191 seconds (JVM running for 24.92)]

原理：因InetAddress.getHostName()在本地 hosts 有映射时会跳过网络 DNS 查询，从而避免阻塞

解决办法二：降低 MySQL 驱动版本

降低至 8.0.33 版本，实测有效

<dependency> <groupId>com.mysql</groupId> <artifactId>mysql-connector-j</artifactId> <version>8.0.33</version> </dependency>

从启动日志可以看出，问题完美解决

[2026-02-07 18:51:19.582] [INFO ] [com.zaxxer.hikari.HikariDataSource] [80] - [HikariPool-1 - Starting...] [2026-02-07 18:51:19.899] [INFO ] [com.zaxxer.hikari.HikariDataSource] [82] - [HikariPool-1 - Start completed.] [2026-02-07 18:51:24.718] [INFO ] [com.alibaba.druid.pool.DruidDataSource] [1007] - [{dataSource-1} inited] [2026-02-07 18:51:37.035] [INFO ] [com.alibaba.druid.pool.DruidDataSource] [1007] - [{dataSource-2} inited] [2026-02-07 18:51:38.433] [INFO ] [com.xxx.WebApplication] [61] - [Started WebApplication in 23.6 seconds (JVM running for 24.33)]