关于Druid重试机制的问题及解决方案
在昨天项目开发中，使用了Druid作为数据库连接池，当数据源密码错误时，报出了以下错误：
2019-04-09 10:09:36 [Druid-ConnectionPool-Create-2053591126] [ com.alibaba.druid.pool.DruidDataSource ] [ 53 ] [ ERROR ] create connection SQLException, url: jdbc:mysql://*.*.*.*:3306/*?characterEncoding=utf-8&useSSL=false, errorCode 1045, state 28000
java.sql.SQLException: Access denied for user 'malluser'@'*.*.*.*' (using password: YES)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:545) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:513) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:115) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:1606) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.mysql.cj.jdbc.ConnectionImpl.(ConnectionImpl.java:633) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:347) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:219) ~[mysql-connector-java-6.0.6.jar:6.0.6]
at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:149) ~[druid-1.1.6%20.jar:1.1.6]
at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:218) ~[druid-1.1.6%20.jar:1.1.6]
at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:143) ~[druid-1.1.6%20.jar:1.1.6]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1512) ~[druid-1.1.6%20.jar:1.1.6]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1575) ~[druid-1.1.6%20.jar:1.1.6]
at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2450) [druid-1.1.6%20.jar:1.1.6] 对于错误相信大家一看都明白是怎么回事，但是问题是Druid会一直不停的对数据源进行重试连接，这样的话我们的日志很快就爆了，为什么Druid会一直进行重试呢？首先让我们看一下源码：
public class CreateConnectionTask implements Runnable {
private int errorCount = 0;
@Override
public void run() {
runInternal();
}
private void runInternal() {
for (;;) {
// addLast
lock.lock();
try {
if (closed || closing) {
createTaskCount--;
return;
}
boolean emptyWait = true;
if (createError != null && poolingCount == 0) {
emptyWait = false;
}
if (emptyWait) {
// 必须存在线程等待，才创建连接
if (poolingCount >= notEmptyWaitThreadCount //
&& !(keepAlive && activeCount + poolingCount < minIdle)) {
createTaskCount--;
return;
}
// 防止创建超过maxActive数量的连接
if (activeCount + poolingCount >= maxActive) {
createTaskCount--;
return;
}
}
} finally {
lock.unlock();
}
PhysicalConnectionInfo physicalConnection = null;
try {
physicalConnection = createPhysicalConnection();
setFailContinuous(false);
} catch (OutOfMemoryError e) {
LOG.error("create connection OutOfMemoryError, out memory. ", 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) {
lock.lock();
try {
createTaskCount--;
} finally {
lock.unlock();
}
return;
}
this.errorCount = 0; // reset errorCount
if (closing || closed) {
createTaskCount--;
return;
}
createSchedulerFuture = createScheduler.schedule(this, timeBetweenConnectErrorMillis, TimeUnit.MILLISECONDS);
return;
}
} catch (SQLException e) {
LOG.error("create connection SQLException, url: " + jdbcUrl, 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) {
lock.lock();
try {
createTaskCount--;
} finally {
lock.unlock();
}
return;
}
this.errorCount = 0; // reset errorCount
if (closing || closed) {
createTaskCount--;
return;
}
createSchedulerFuture = createScheduler.schedule(this, timeBetweenConnectErrorMillis, TimeUnit.MILLISECONDS);
return;
}
} catch (RuntimeException e) {
LOG.error("create connection RuntimeException", e);
// unknow fatal exception
setFailContinuous(true);
continue;
} catch (Error e) {
lock.lock();
try {
createTaskCount--;
} finally {
lock.unlock();
}
LOG.error("create connection Error", e);
// unknow fatal exception
setFailContinuous(true);
break;
} catch (Throwable e) {
LOG.error("create connection unexecpted error.", e);
break;
}
if (physicalConnection == null) {
continue;
}
boolean result = put(physicalConnection);
if (!result) {
JdbcUtils.close(physicalConnection.getPhysicalConnection());
LOG.info("put physical connection to pool failed.");
}
break;
}
}
}
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.get() < 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;
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.error("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
}
}
}从源码中我们可以看到，线程中使用了无参for循环再一直尝试进行数据源连接，代码中【errorCount > connectionErrorRetryAttempts && timeBetweenConnectErrorMillis > 0】当满足该判断条件时就会进行重试连接，接下来我们看一下源码中这两个属性值设置的是什么呢？（源码过长，只展示我们需要的代码，其他属性信息可自行扒源码~）
private static final long serialVersionUID = 1L;
public final static int DEFAULT_INITIAL_SIZE = 0;
public final static int DEFAULT_MAX_ACTIVE_SIZE = 8;
public final static int DEFAULT_MAX_IDLE = 8;
public final static int DEFAULT_MIN_IDLE = 0;
public final static int DEFAULT_MAX_WAIT = -1;
public final static String DEFAULT_VALIDATION_QUERY = null; //
public final static boolean DEFAULT_TEST_ON_BORROW = false;
public final static boolean DEFAULT_TEST_ON_RETURN = false;
public final static boolean DEFAULT_WHILE_IDLE = true;
public static final long DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS = 60 * 1000L;
public static final long DEFAULT_TIME_BETWEEN_CONNECT_ERROR_MILLIS = 500;
public static final int DEFAULT_NUM_TESTS_PER_EVICTION_RUN = 3;
/*****************************华丽的分割线中间省略代码若干行*********************************/
protected volatile long timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
protected int connectionErrorRetryAttempts = 1;
protected boolean breakAfterAcquireFailure = false;从中这段代码中我们可以看到connectionErrorRetryAttempts值为1，timeBetweenConnectErrorMillis值为60000，而breakAfterAcquireFailure值为false，因此当我们数据源连接失败后，就会不断的进行重试连接，因此我对于对于该如何解决这样的问题我们就有了答案:
1.若不想让重试，我们可以设置breakAfterAcquireFailure(true);connectionErrorRetryAttempts(0);
2.若想要设置多久重试，我们只需要设置timeBetweenConnectErrorMillis(time）；
action：经过亲测，直接在配置文件中配置属性并不能读取到（Druid设计时就这样，大神的思维暂时还不能参悟~），我们可直接将值写入程序当中，如下：
private static void Init() {
try {
Properties properties = loadPropertiesFile("db.properties");
druidDataSource = (DruidDataSource) DruidDataSourceFactory.createDataSource(properties); // DruidDataSrouce工厂模式
// TODO 调试配置，用完删除
druidDataSource.setRemoveAbandoned(true);
druidDataSource.setRemoveAbandonedTimeout(600);
druidDataSource.setLogAbandoned(true);
// druidDataSource.setBreakAfterAcquireFailure(true);
druidDataSource.setTimeBetweenConnectErrorMillis(60000);
// druidDataSource.setConnectionErrorRetryAttempts(0);
} catch (Exception e) {
logger.error(DbPoolConnection.class, e);
}
}当然若是想要方便以后修改，我们可以在properties文件中设置该值，读取出来配置文件的值再赋值给druidDataSource。
到这里，本文就结束了，如有不当之处，欢迎指正！
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