maxLifetime参数
-
maxLifetime参数必须小于数据库的time_wait,默认是1800000,即30分钟。如果设置为0,表示存活时间无限大。如果不等于0且小于30秒则会被重置回30分钟。HikariConfig类中有该参数的校验规则。
-
HikariPool类中,当我们初始化连接池的时候,它的构造方法中,实例化了
this.POOL_ENTRY_CREATOR = new HikariPool.PoolEntryCreator();
该类实现了Callable接口,用来初始化连接。
public Boolean call() throws Exception {
for(long sleepBackoff = 250L; HikariPool.this.poolState == 0 && HikariPool.this.totalConnections.get() < HikariPool.this.config.getMaximumPoolSize(); sleepBackoff = Math.min(TimeUnit.SECONDS.toMillis(10L), Math.min(HikariPool.this.connectionTimeout, (long)((double)sleepBackoff * 1.5D)))) {
PoolEntry poolEntry = HikariPool.this.createPoolEntry();
if (poolEntry != null) {
HikariPool.this.totalConnections.incrementAndGet();
HikariPool.this.connectionBag.add(poolEntry);
return Boolean.TRUE;
}
UtilityElf.quietlySleep(sleepBackoff);
}
return Boolean.FALSE;
}
在其中调用createPoolEntry()
生成一个连接。
private PoolEntry createPoolEntry() {
try {
final PoolEntry poolEntry = this.newPoolEntry();
long maxLifetime = this.config.getMaxLifetime();
if (maxLifetime > 0L) {
long variance = maxLifetime > 10000L ? ThreadLocalRandom.current().nextLong(maxLifetime / 40L) : 0L;
long lifetime = maxLifetime - variance;
poolEntry.setFutureEol(this.houseKeepingExecutorService.schedule(new Runnable() {
public void run() {
HikariPool.this.softEvictConnection(poolEntry, "(connection has passed maxLifetime)", false);
}
}, lifetime, TimeUnit.MILLISECONDS));
}
this.LOGGER.debug("{} - Added connection {}", this.poolName, poolEntry.connection);
return poolEntry;
} catch (Exception var8) {
if (this.poolState == 0) {
this.LOGGER.debug("{} - Cannot acquire connection from data source", this.poolName, var8);
}
return null;
}
}
在该方法中,设置了一个延时任务,具体的延时执行时间是根据maxLifetime来计算,触发时间距离maxlifetime的差值是根据 maxLifetime > 10_000 ? ThreadLocalRandom.current().nextLong( maxLifetime / 40 ) : 0; 来计算(up to 2.5% of the maxlifetime
),在连接存活将要到达maxLifetime之前触发evit,用来防止出现大面积的connection因maxLifetime同一时刻失效。
当被触发时,会标记evict
为true,标记为evict只是表示连接池中的该连接不可用,但还在连接池当中,还会被borrow出来,只是getConnection的时候判断了,如果是isMarkedEvicted,则会从连接池中移除该连接,然后close掉。
-
HikariCP中通过独立的线程池closeConnectionExecutor进行物理连接的关闭。出现以下三种情况时会触发连接的自动关闭:
-
连接断开;
-
连接存活时间超出最大生存时间(maxLifeTime)
-
连接空闲时间超出最大空闲时间(idleTimeout)
closeConnectionExecutor关闭连接后,会调用fillPool()方法对连接池进行连接填充
validationTimeout
- validationTimeout用来指定验证连接有效性的超时时间(
默认是5秒,最小不能小于250毫秒
),在HikariPool.getConnection
方法中会调用isConnectionAlive(Connection connection)
对连接进行验证。
如果是jdbc4的话,可以使用isUseJdbc4Validation,是直接利用connection.isValid(validationSeconds)来验证连接的有效性;否则的话则用connectionTestQuery查询语句来查询验证。
leakDetectionThreshold`
-
该参数主要用来开启连接泄漏检测,在通过
getConnection()
获取连接的时候,会继续调用另外一个createProxyConnection()方法获取连接,这里我们关注入参this.leakTask.schedule(poolEntry)
。public final Connection getConnection(long hardTimeout) throws SQLException { this.suspendResumeLock.acquire(); long startTime = clockSource.currentTime(); try { long timeout = hardTimeout; do { PoolEntry poolEntry = (PoolEntry)this.connectionBag.borrow(timeout, TimeUnit.MILLISECONDS); if (poolEntry == null) { break; } long now = clockSource.currentTime(); if (!poolEntry.isMarkedEvicted() && (clockSource.elapsedMillis(poolEntry.lastAccessed, now) <= this.ALIVE_BYPASS_WINDOW_MS || this.isConnectionAlive(poolEntry.connection))) { this.metricsTracker.recordBorrowStats(poolEntry, startTime); //获取连接 Connection var10 = poolEntry.createProxyConnection(this.leakTask.schedule(poolEntry), now); return var10; }
该
schedule
方法返回一个ProxyLeakTask
对象//返回 ProxyLeakTask ProxyLeakTask schedule(PoolEntry bagEntry) { return this.leakDetectionThreshold == 0L ? NO_LEAK : new ProxyLeakTask(this, bagEntry); }
这里判断
leakDetectionThreshold
参数是否为0,默认是0,不开启检测。否则,就会开启一个延时执行任务,时间正好为设置的leakDetectionThreshold
值,该任务的作用就是用来抛出Apparent connection leak detected
异常。private ProxyLeakTask(ProxyLeakTask parent, PoolEntry poolEntry) { this.exception = new Exception("Apparent connection leak detected"); this.connectionName = poolEntry.connection.toString(); //延时执行 this.scheduledFuture = parent.executorService.schedule(this, parent.leakDetectionThreshold, TimeUnit.MILLISECONDS); }
截取一部分异常,如下
22:14:49.096 volte-cmd-service-test [HikariPool-1 housekeeper] WARN com.zaxxer.hikari.pool.ProxyLeakTask - Connection leak detection triggered for com.mysql.jdbc.JDBC4Connection@429fe922, stack trace follows java.lang.Exception: Apparent connection leak detected at org.hibernate.engine.jdbc.connections.internal.DatasourceConnectionProviderImpl.getConnection(DatasourceConnectionProviderImpl.java:122) at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:386) at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.acquireConnectionIfNeeded(LogicalConnectionManagedImpl.java:87) at org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.getPhysicalConnection(LogicalConnectionManagedImpl.java:112) at org.hibernate.internal.SessionImpl.connection(SessionImpl.java:489) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:215) at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:200) at org.springframework.orm.jpa.vendor.HibernateJpaDialect$HibernateConnectionHandle.doGetConnection(HibernateJpaDialect.java:414) at org.springframework.orm.jpa.vendor.HibernateJpaDialect.beginTransaction(HibernateJpaDialect.java:177)
也就是从我们获取这个连接开始,到归还连接之前的这一段时间,如果超过了
leakDetectionThreshold
,则会抛出上面的异常。
HouseKeeper
它是HikariPool
中的一个内部类,实现了Runnable
接口,主要就是对连接进行管理。在初始化HikariPool
的时候,会创建一个scheduleWithFixedDelay
任务(已固定延迟时间执行,就是说两个任务之间的时间间隔是固定的,但每个任务的执行时长可能是不定的,与scheduleFixedRate
的区别就是,不管任务是否执行完,到点就执行下一次任务),默认30s执行一次,刷新配置,进行判断。
public HikariPool(HikariConfig config) {
super(config);
this.ALIVE_BYPASS_WINDOW_MS = Long.getLong("com.zaxxer.hikari.aliveBypassWindowMs", TimeUnit.MILLISECONDS.toMillis(500L));
this.HOUSEKEEPING_PERIOD_MS = Long.getLong("com.zaxxer.hikari.housekeeping.periodMs", TimeUnit.SECONDS.toMillis(30L));
this.POOL_ENTRY_CREATOR = new HikariPool.PoolEntryCreator();
this.connectionBag = new ConcurrentBag(this);
this.totalConnections = new AtomicInteger();
this.suspendResumeLock = config.isAllowPoolSuspension() ? new SuspendResumeLock() : SuspendResumeLock.FAUX_LOCK;
this.checkFailFast();
if (config.getMetricsTrackerFactory() != null) {
this.setMetricsTrackerFactory(config.getMetricsTrackerFactory());
} else {
this.setMetricRegistry(config.getMetricRegistry());
}
this.setHealthCheckRegistry(config.getHealthCheckRegistry());
this.registerMBeans(this);
ThreadFactory threadFactory = config.getThreadFactory();
this.addConnectionExecutor = UtilityElf.createThreadPoolExecutor(config.getMaximumPoolSize(), this.poolName + " connection adder", threadFactory, new DiscardPolicy());
this.closeConnectionExecutor = UtilityElf.createThreadPoolExecutor(config.getMaximumPoolSize(), this.poolName + " connection closer", threadFactory, new CallerRunsPolicy());
//创建定时任务类
if (config.getScheduledExecutorService() == null) {
ThreadFactory threadFactory = threadFactory != null ? threadFactory : new DefaultThreadFactory(this.poolName + " housekeeper", true);
this.houseKeepingExecutorService = new ScheduledThreadPoolExecutor(1, (ThreadFactory)threadFactory, new DiscardPolicy());
//传递false参数给这个方法,执行shutdown()方法之后,待处理的任务将不会被执行。
this.houseKeepingExecutorService.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
//取消任务后,判断是否需要从阻塞队列中移除任务
this.houseKeepingExecutorService.setRemoveOnCancelPolicy(true);
} else {
this.houseKeepingExecutorService = config.getScheduledExecutorService();
}
this.leakTask = new ProxyLeakTask(config.getLeakDetectionThreshold(), this.houseKeepingExecutorService);
//初始化HouseKeeper
this.houseKeepingExecutorService.scheduleWithFixedDelay(new HikariPool.HouseKeeper(), 100L, this.HOUSEKEEPING_PERIOD_MS, TimeUnit.MILLISECONDS);
}
时间回拨处理
在HouseKeeper
的run
方法中,会先对时间进行判断。
这里主要就是通过一个时间差来判断这个时间差返回内是否有时间回拨,在初始化的时候会通过下面构造方法生成一个时间戳
// previous=当前时间-30s(默认的定时任务间隔时间)
private HouseKeeper() {
this.previous = HikariPool.clockSource.plusMillis(HikariPool.clockSource.currentTime(), -HikariPool.this.HOUSEKEEPING_PERIOD_MS);
}
当初始化完成的第一次30s后或者上次任务执行完的30s后,再执行该任务,如果当前的时间戳+128ms还要小于previous(上次执行后减去30s的时间戳)+30s,则表示有时间回拨
//检测逆行时间,根据NTP规范允许+128ms
if (HikariPool.clockSource.plusMillis(now, 128L) < HikariPool.clockSource.plusMillis(this.previous, HikariPool.this.HOUSEKEEPING_PERIOD_MS)) {
HikariPool.this.LOGGER.warn("{} - Retrograde clock change detected (housekeeper delta={}), soft-evicting connections from pool.", HikariPool.this.poolName, HikariPool.clockSource.elapsedDisplayString(this.previous, now));
this.previous = now;
HikariPool.this.softEvictConnections();
HikariPool.this.fillPool();
return;
}
此时,会打印日志,并重置previous为当前时间,设置连接为不可用,再重新生成连接。
保持最小连接
-
如果时间没有错误,则会判断
idleTimeout
,如果大于0,取出当前空闲连接 -
判断是否大于最小连接数
minimumIdle
,如果大于,则继续对当前的空闲连接基于lastAccessed
(最后一次访问时间)进行排序,再遍历 -
如果取出的每个连接的空闲时间已经超过了
idleTimeout
,并且成功将连接从NOT_IN_USE
(闲置中)更改为RESERVED
(标记为保留中) -
则关闭该连接
-
最后再新创建连接
public void run() { try { //刷新connectionTimeout、validationTimeout HikariPool.this.connectionTimeout = HikariPool.this.config.getConnectionTimeout(); HikariPool.this.validationTimeout = HikariPool.this.config.getValidationTimeout(); HikariPool.this.leakTask.updateLeakDetectionThreshold(HikariPool.this.config.getLeakDetectionThreshold()); long idleTimeout = HikariPool.this.config.getIdleTimeout(); long now = HikariPool.clockSource.currentTime(); //时钟回拨判断 if (HikariPool.clockSource.plusMillis(now, 128L) < HikariPool.clockSource.plusMillis(this.previous, HikariPool.this.HOUSEKEEPING_PERIOD_MS)) { HikariPool.this.LOGGER.warn("{} - Retrograde clock change detected (housekeeper delta={}), soft-evicting connections from pool.", HikariPool.this.poolName, HikariPool.clockSource.elapsedDisplayString(this.previous, now)); this.previous = now; HikariPool.this.softEvictConnections(); HikariPool.this.fillPool(); return; } if (now > HikariPool.clockSource.plusMillis(this.previous, 3L * HikariPool.this.HOUSEKEEPING_PERIOD_MS / 2L)) { HikariPool.this.LOGGER.warn("{} - Thread starvation or clock leap detected (housekeeper delta={}).", HikariPool.this.poolName, HikariPool.clockSource.elapsedDisplayString(this.previous, now)); } this.previous = now; String afterPrefix = "Pool "; if (idleTimeout > 0L) { //取出空闲连接 连接状态,IN_USE(1:使用中)、NOT_IN_USE(0:闲置中)、REMOVED(-1:已移除)、RESERVED(-1:标记为保留中) List<PoolEntry> idleList = HikariPool.this.connectionBag.values(0); int removable = idleList.size() - HikariPool.this.config.getMinimumIdle(); if (removable > 0) { HikariPool.this.logPoolState("Before cleanup "); afterPrefix = "After cleanup "; //排序 idleList.sort(PoolEntry.LASTACCESS_COMPARABLE); Iterator var8 = idleList.iterator(); while(var8.hasNext()) { PoolEntry poolEntry = (PoolEntry)var8.next(); //idleTimeout判断,连接状态修改 if (HikariPool.clockSource.elapsedMillis(poolEntry.lastAccessed, now) > idleTimeout && HikariPool.this.connectionBag.reserve(poolEntry)) { HikariPool.this.closeConnection(poolEntry, "(connection has passed idleTimeout)"); --removable; if (removable == 0) { break;//keep min idle cons } } } } } HikariPool.this.logPoolState(afterPrefix); HikariPool.this.fillPool(); } catch (Exception var10) { HikariPool.this.LOGGER.error("Unexpected exception in housekeeping task", var10); } } }
问题
minimumIdle不一致问题
当前版本在应用初始化的时候,连接池也会进行初始化,但是当我们配置的数据源属性minimumIdle<maximumPoolSize时,比如minimumIdle=4,maximumPoolSize=10,但是当应用初始化完成后,minimumIdle=5。大概就是应用启动时,SpringManagedTransaction
会去获取一个连接,这个时候会去初始化连接池,而这个连接并没有被连接池初始化时判断到,最后多生成了一个连接。把版本升级到最新的3.4.5后,该bug消失(哪个版本修改的不确定)。
//HikariCP-3.4.5.jar
private synchronized void fillPool()
{
final int connectionsToAdd = Math.min(config.getMaximumPoolSize() - getTotalConnections(), config.getMinimumIdle() - getIdleConnections())
- addConnectionQueueReadOnlyView.size();
if (connectionsToAdd <= 0) logger.debug("{} - Fill pool skipped, pool is at sufficient level.", poolName);
//生成的个数减去了1
for (int i = 0; i < connectionsToAdd; i++) {
addConnectionExecutor.submit((i < connectionsToAdd - 1) ? poolEntryCreator : postFillPoolEntryCreator);
}
}
//HikariCP-2.5.1.jar 的该方法
for (int i = 0; i < connectionsToAdd; i++) {
addBagItem();
}
超时问题
错误日志如下:
java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30000ms.
-
首先检查配置是否有问题,
maxLifetime
不能大于数据库的time_wait
,查询mysql配置show variables like ‘%timeout%’,默认为8小时。 -
配置没有问题,则有可能与HikariCP无关。这个错误的产生原因就是请求向池中
borrow
时,没有可用连接超时导致。第一点,此时我们要思考我们的连接池数量设置是否合理,与业务量相关;第二点,看我们代码是否存在慢sql;第三点,与使用的持久层框架有关,分析我们的连接到底是被谁所持有,它的连接管理方法是怎么样的,什么情况下才会归还连接。这篇文章就是因为我遇到这个错而无法定位才决定好好研究下的,我的这个错误产生的原因就是上面的第三点,我的项目采用的是jpa做数据库交互,且是一个非常简单的单表查询,连接应该很快归还池中才对,但是经过我的测试,当经过数据库查询以后,连接并没有被释放,反而是在我的整个会话结束后,才会归还连接。
jpa的核心是hibernate-core,在网上查询了hibernate的连接释放策略,知道了原因。hibernate 中连接释放的策略hibernate. connection. release_ mode有以下四种属性:
- on_close,当Session被显式关闭或被断开连接时,才会释放JDBC连接
- after_transaction,每次事务结束都会释放链接
- after_statement,在每次JDBC调用后,都会主动的释放连接
- auto,为JTA和CMT事务策略选择after_statement, 为JDBC事务策略选择after_transaction
我的springboot项目版本为1.x,即便将hibernate-core升级到较高版本,并开启事物,也还是基于on_close方式去释放连接;我测试了2.x版本的,不开启事物时也是on_close,开启事物后,就成了after_transaction,具体1.x版本为何开启事物也不生效还不清楚。
参考资料
-
流程图的方式讲解,很清晰易懂,版本也比较高
今天的文章hikari连接池解析(版本:HikariCP-2.5.1.jar)分享到此就结束了,感谢您的阅读。
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