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 <p>在使用个人阿里云测试机，在查询实时输出日志时，看到数据库连接失败后，服务器一直在重连服务器。开始以为是遭受重复攻击，后面把服务重启后，就没有出现一直重连的情况。看以下输出日志：</p><blockquote><p>2022-02-09 11:04:58.896 ERROR 16876 --- [eate-] com.alibaba.druid.pool.DruidDataSource &nbsp; : create connection SQLException, url: jdbc:mysql://47.98.67,98:1234/test?useSSL=false&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC, errorCode 1045, state 28000</p><p>java.sql.SQLException: Access denied for user &#39;root&#39;@&#39;113.90.123.76&#39; (using password: YES)<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.ConnectionImpl.&lt;init&gt;(ConnectionImpl.java:455) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) ~[mysql-connector-java-8.0.16.jar:8.0.16]<br/>&nbsp; &nbsp; at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:156) ~[druid-1.1.10.jar:1.1.10]<br/>&nbsp; &nbsp; at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:218) ~[druid-1.1.10.jar:1.1.10]<br/>&nbsp; &nbsp; at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150) ~[druid-1.1.10.jar:1.1.10]<br/>&nbsp; &nbsp; at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1560) ~[druid-1.1.10.jar:1.1.10]<br/>&nbsp; &nbsp; at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1623) ~[druid-1.1.10.jar:1.1.10]<br/>&nbsp; &nbsp; at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2468) ~[druid-1.1.10.jar:1.1.10]</p></blockquote><p>注意上面一直有 druid 数据库连接池的提示，这里就想到可能是 druid 连接池的问题，然后去掉 druid maven 依赖后在请求接口就不会出现重连的问题。</p><p>在上图源码找到最后一行 DruidDataSource.java:2468 定位到源码上，CreateConnectionThread 创建连接线程，看一下 CreateConnectionThread 源码：</p><p>这是一个多线程的类，而 run 方法里面设置了没有限制的 for 循环 for (;;) {}, 而日志报错定位的信息:</p><p>如果符合条件 errorCount &gt; connectionErrorRetryAttempts &amp;&amp; timeBetweenConnectErrorMillis &gt; 0 会再次尝试重连，先看一下这几个参数的含义：</p><p>在 run 方法初始化时为零，每次连接失败，会自动加1</p><p><strong>connectionErrorRetryAttempts</strong></p><p>连接错误重试次数，默认值为 1。</p><p><strong>timeBetweenConnectErrorMillis</strong></p><p>连接间隔时间，单位毫秒。默认值为 500。</p><p>我们在连接数据库失败后，要不在里面 break 中断，其中有</p><p>将改 break-after-acquire-failure 设置成 true,在 application.properties 文件如下配置：</p><p>如果想多尝试连接几次，需要设置 connection-error-retry-attempts ,当 errorCount 大于 connectionErrorRetryAttempts 才会进入到 条件内，才会中断循环。在 application.properties 文件如下配置：</p>