springboot druid数据库连接池连接失败后一直重连的解决方法

springboot druid数据库连接池连接失败后一直重连的解决方法

目录druid 重连原因errorCount 错误次数总结

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：

2022-02-09 11:04:58.896 ERROR 16876 --- [eate-1550991149] com.alibaba.druid.pool.DruidDataSource   : create connection SQLException, url: jdbc:mysql://47.98.67,98:1234/test?useSSL=false&characterEncoding=UTF-8&serverTimezone=UTC, errorCode 1045, state 28000

java.sql.SQLException: Access denied for user 'root'@'113.90.123.76' (using password: YES)    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.mysql.cj.jdbc.ConnectionImpl.(ConnectionImpl.java:455) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199) ~[mysql-connector-java-8.0.16.jar:8.0.16]    at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:156) ~[druid-1.1.10.jar:1.1.10]    at com.alibaba.dhttp://ruid.filter.stat.StatFilter.connection_connect(StatFilter.java:218) ~[druid-1.1.10.jar:1.1.10]    at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150) ~[druid-1.1.10.jar:1.1.10]    at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1560) ~[druid-1.1.10.jar:1.1.10]    at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1623) ~[druid-1.1.10.jar:1.1.10]    at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2468) ~[druid-1.1.10.jar:1.1.10]

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。

druid 重连原因

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：

public class CreateConnectionThread extends Thread {

public CreateConnectionThread(String name){

super(name);

this.setDaemon(true);

}

public void run() {

initedLatch.countDown();

long lastDiscardCount = 0;

int errorCount = 0;

for (;;) {

// addLast

try {

lock.lockInterruptibly();

} catch (InterruptedException e2) {

break;

}

long discardCount = DruidDataSource.this.discardCount;

boolean discardChanged = discardCount - lastDiscardCount > 0;

lastDiscardCount = discardCount;

try {

boolean emptyWait = true;

if (createError != null

&& poolingCount == 0

&& !discardChanged) {

emptyWait = false;

}

if (emptyWait

&& asyncInit && createCount < initialSize) {

emptyWait = false;

}

if (emptyWait) {

// 必须存在线程等待，才创建连接

if (poolingCount >= notEmptyWaitThreadCount //

&& !(keepAlive && activeCount + poolingCount < minIdle)) {

empty.await();

}

// 防止创建超过maxActive数量的连接

if (activeCount + poolingCount >= maxActive) {

empty.await();

continue;

}

}

} catch (InterruptedException e) {

lastCreateError = e;

http:// lastErrorTimeMillis = System.currentTimeMillis();

if (!closing) {

LOG.error("create connection Thread Interrupted, url: " + jdbcUrl, e);

}

break;

} finally {

lock.unlock();

}

PhysicalConnectionInfo connection = null;

try {

connection = createPhysicalConnection();

setFailContinuous(false);

} catch (SQLException e) {

LOG.error("create connection SQLException, url: " + jdbcUrl + ", errorCode " + e.getErrorCode()

+ ", state " + e.getSQLState(), e);

errorCount++;

if (errorCount > connectionErrorRetryAttempts && timeBetweenConnectErrorMillis > 0) {

// fail over retry attempts

setFailContinuous(true);

if (failFast) {

lock.lock();

try {

notEmpty.signalAll();

} finally {

lock.unlock();

}

}

if (breakAfterAcquireFailure) {

break;

}

try {

Thread.sleep(timeBetweenConnectErrorMillis);

} catch (InterruptedException interruptEx) {

break;

}

}

} catch (RuntimeException e) {

LOG.error("create connection RuntimeException", e);

setFailContinuous(true);

continue;

} catch (Error e) {

LOG.eMambxKxrror("create connection Error", e);

setFailContinuous(true);

break;

}

if (connection == null) {

continue;

}

boolean result = put(connection);

if (!result) {

JdbcUtils.close(connection.getPhysicalConnection());

LOG.info("put physical connection to pool failed.");

}

errorCount = 0; // reset errorCount

}

}

}

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:

connection = createPhysicalConnection();

如果符合条件 errorCount > connectionErrorRetryAttempts && timeBetweenConnectErrorMillis > 0 会再次尝试重连，先看一下这几个参数的含义：

errorCount 错误次数

在 run 方法初始化时为零，每次连接失败，会自动加1

connectionErrorRetryAttempts

连接错误重试次数，默认值为 1。

protected int connectionErrorRetryAttempts = 1;

timeBetweenConnectErrorMillis

连接间隔时间，单位毫秒。默认值为 500。

protected volatile long timeBetweenConnectErrorMillis = DEFAULT_TIME_BETWEEN_CONNECT_ERROR_MILLIS;

public static final long DEFAULT_TIME_BETWEEN_CONNECT_ERROR_MILLIS = 500;

我们在连接数据库失败后，要不在里面 break 中断，其中有

if (breakAfterAcquireFailure) {

break;

}

将改 break-after-acquire-failure 设置成 true,在 application.properties 文件如下配置：

spring.datasource.druid.break-after-acquire-failure=true

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：

spring.datasource.druid.connection-error-retry-attempts=3

总结

druid 数据库连接失败，是因为在使用多线程连接数据时使用了无限制循环连接，需要在连接失败中断连接，需要设置 break-after-acquire-failure 为 true。设置之后数据库连接不成功也不会不断的重试。如果要设置重连次数要设置 connection-error-retry-attempts。

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