序
本文主要研究一下hikari连接池的isAllowPoolSuspension属性
实例代码
@Test
public void testPoolSuspend() throws SQLException {
Connection conn = dataSource.getConnection();
System.out.println("begin to suspend pool");
((HikariDataSource)dataSource).suspendPool();
Connection conn2 = dataSource.getConnection();
System.out.println("finish");
}
suspend
begin to suspend pool
java.lang.IllegalStateException: HikariPool-1 - is not suspendable
at com.zaxxer.hikari.pool.HikariPool.suspendPool(HikariPool.java:372)
at com.zaxxer.hikari.HikariDataSource.suspendPool(HikariDataSource.java:326)
at com.example.demo.HikariDemoApplicationTests.testPoolSuspend(HikariDemoApplicationTests.java:37)
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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)
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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
当没有设置的allow-pool-suspension=true时候，抛出java.lang.IllegalStateException: HikariPool-1 - is not suspendable
allow-pool-suspension=true
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java
/**
* Construct a HikariPool with the specified configuration.
*
* @param config a HikariConfig instance
*/
public HikariPool(final HikariConfig config)
{
super(config);
this.connectionBag = new ConcurrentBag<>(this);
this.suspendResumeLock = config.isAllowPoolSuspension() ? new SuspendResumeLock() : SuspendResumeLock.FAUX_LOCK;
this.houseKeepingExecutorService = initializeHouseKeepingExecutorService();
checkFailFast();
if (config.getMetricsTrackerFactory() != null) {
setMetricsTrackerFactory(config.getMetricsTrackerFactory());
}
else {
setMetricRegistry(config.getMetricRegistry());
}
setHealthCheckRegistry(config.getHealthCheckRegistry());
registerMBeans(this);
ThreadFactory threadFactory = config.getThreadFactory();
LinkedBlockingQueue<Runnable> addConnectionQueue = new LinkedBlockingQueue<>(config.getMaximumPoolSize());
this.addConnectionQueue = unmodifiableCollection(addConnectionQueue);
this.addConnectionExecutor = createThreadPoolExecutor(addConnectionQueue, poolName + " connection adder", threadFactory, new ThreadPoolExecutor.DiscardPolicy());
this.closeConnectionExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection closer", threadFactory, new ThreadPoolExecutor.CallerRunsPolicy());
this.leakTaskFactory = new ProxyLeakTaskFactory(config.getLeakDetectionThreshold(), houseKeepingExecutorService);
this.houseKeeperTask = houseKeepingExecutorService.scheduleWithFixedDelay(new HouseKeeper(), 100L, HOUSEKEEPING_PERIOD_MS, MILLISECONDS);
}
如果isAllowPoolSuspension为ture，则suspendResumeLock是一个真实的SuspendResumeLock，否则是SuspendResumeLock.FAUX_LOCK
SuspendResumeLock
/**
* This class implements a lock that can be used to suspend and resume the pool. It
* also provides a faux implementation that is used when the feature is disabled that
* hopefully gets fully "optimized away" by the JIT.
*
* @author Brett Wooldridge
*/
public class SuspendResumeLock
{
public static final SuspendResumeLock FAUX_LOCK = new SuspendResumeLock(false) {
@Override
public void acquire() {}
@Override
public void release() {}
@Override
public void suspend() {}
@Override
public void resume() {}
};
private static final int MAX_PERMITS = 10000;
private final Semaphore acquisitionSemaphore;
/**
* Default constructor
*/
public SuspendResumeLock()
{
this(true);
}
private SuspendResumeLock(final boolean createSemaphore)
{
acquisitionSemaphore = (createSemaphore ? new Semaphore(MAX_PERMITS, true) : null);
}
public void acquire()
{
acquisitionSemaphore.acquireUninterruptibly();
}
public void release()
{
acquisitionSemaphore.release();
}
public void suspend()
{
acquisitionSemaphore.acquireUninterruptibly(MAX_PERMITS);
}
public void resume()
{
acquisitionSemaphore.release(MAX_PERMITS);
}
}
FAUX_LOCK是一个空方法，false表示不创建信号量
suspend方法一次性消耗了MAX_PERMITS信号量，这个方法被调用之后，之后getConnection方法都获取不到连接，永远阻塞在suspendResumeLock.acquire();
resume方法一次性释放MAX_PERMITS信号量
HikariPool.getConnection
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java
/**
* Get a connection from the pool, or timeout after connectionTimeout milliseconds.
*
* @return a java.sql.Connection instance
* @throws SQLException thrown if a timeout occurs trying to obtain a connection
*/
public Connection getConnection() throws SQLException
{
return getConnection(connectionTimeout);
}
/**
* Get a connection from the pool, or timeout after the specified number of milliseconds.
*
* @param hardTimeout the maximum time to wait for a connection from the pool
* @return a java.sql.Connection instance
* @throws SQLException thrown if a timeout occurs trying to obtain a connection
*/
public Connection getConnection(final long hardTimeout) throws SQLException
{
suspendResumeLock.acquire();
final long startTime = currentTime();
try {
long timeout = hardTimeout;
do {
PoolEntry poolEntry = connectionBag.borrow(timeout, MILLISECONDS);
if (poolEntry == null) {
break; // We timed out... break and throw exception
}
final long now = currentTime();
if (poolEntry.isMarkedEvicted() || (elapsedMillis(poolEntry.lastAccessed, now) > ALIVE_BYPASS_WINDOW_MS && !isConnectionAlive(poolEntry.connection))) {
closeConnection(poolEntry, poolEntry.isMarkedEvicted() ? EVICTED_CONNECTION_MESSAGE : DEAD_CONNECTION_MESSAGE);
timeout = hardTimeout - elapsedMillis(startTime);
}
else {
metricsTracker.recordBorrowStats(poolEntry, startTime);
return poolEntry.createProxyConnection(leakTaskFactory.schedule(poolEntry), now);
}
} while (timeout > 0L);
metricsTracker.recordBorrowTimeoutStats(startTime);
throw createTimeoutException(startTime);
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
throw new SQLException(poolName + " - Interrupted during connection acquisition", e);
}
finally {
suspendResumeLock.release();
}
}
可以看到getConnection是先获取信号量，最后不管获取成功还是超时，finally里头去释放这个信号量
这里的hardTimeout就是从连接池借用connection的超时时间
小结
isAllowPoolSuspension用来标记释放允许暂停连接池，一旦被暂停，所有的getConnection方法都会被阻塞。可能的用处就是用来实现chaosmonkey，模拟数据库连接故障。作者在github上的解释是可以用来做些配置修改：暂停连接池，修改连接池配置或dns配置，soft-evit既有连接，然后恢复连接池。
