序
本文主要研究一下hikari连接池的leakDetectionThreshold，也就是连接池泄露检测。
leakDetectionThreshold
用来设置连接被占用的超时时间，单位为毫秒，默认为0，表示禁用连接泄露检测。如果大于0且不是单元测试，则进一步判断：(leakDetectionThreshold < SECONDS.toMillis(2) or (leakDetectionThreshold > maxLifetime && maxLifetime > 0)，会被重置为0 .
即如果要生效则必须>0，同时满足：不能小于2秒，而且当maxLifetime > 0时不能大于maxLifetime，该值默认为1800000，即30分钟。
HikariPool.getConnection
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java
/**
* 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();
}
}注意，getConnection返回的时候调用了poolEntry.createProxyConnection(leakTaskFactory.schedule(poolEntry), now)
注意，这里创建代理连接的时候关联了ProxyLeakTask
leakTaskFactory
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);
}
/**
* Create/initialize the Housekeeping service {@link ScheduledExecutorService}. If the user specified an Executor
* to be used in the {@link HikariConfig}, then we use that. If no Executor was specified (typical), then create
* an Executor and configure it.
*
* @return either the user specified {@link ScheduledExecutorService}, or the one we created
*/
private ScheduledExecutorService initializeHouseKeepingExecutorService()
{
if (config.getScheduledExecutor() == null) {
final ThreadFactory threadFactory = Optional.ofNullable(config.getThreadFactory()).orElse(new DefaultThreadFactory(poolName + " housekeeper", true));
final ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(1, threadFactory, new ThreadPoolExecutor.DiscardPolicy());
executor.setExecuteExistingDelayedTasksAfterShutdownPolicy(false);
executor.setRemoveOnCancelPolicy(true);
return executor;
}
else {
return config.getScheduledExecutor();
}
}注意，这里初始化了leakTaskFactory，以及houseKeepingExecutorService
ProxyLeakTaskFactory
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/ProxyLeakTaskFactory.java
/**
* A factory for {@link ProxyLeakTask} Runnables that are scheduled in the future to report leaks.
*
* @author Brett Wooldridge
* @author Andreas Brenk
*/
class ProxyLeakTaskFactory
{
private ScheduledExecutorService executorService;
private long leakDetectionThreshold;
ProxyLeakTaskFactory(final long leakDetectionThreshold, final ScheduledExecutorService executorService)
{
this.executorService = executorService;
this.leakDetectionThreshold = leakDetectionThreshold;
}
ProxyLeakTask schedule(final PoolEntry poolEntry)
{
return (leakDetectionThreshold == 0) ? ProxyLeakTask.NO_LEAK : scheduleNewTask(poolEntry);
}
void updateLeakDetectionThreshold(final long leakDetectionThreshold)
{
this.leakDetectionThreshold = leakDetectionThreshold;
}
private ProxyLeakTask scheduleNewTask(PoolEntry poolEntry) {
ProxyLeakTask task = new ProxyLeakTask(poolEntry);
task.schedule(executorService, leakDetectionThreshold);
return task;
}
}注意，如果leakDetectionThreshold=0，即禁用连接泄露检测，schedule返回的是ProxyLeakTask.NO_LEAK，否则则新建一个ProxyLeakTask，在leakDetectionThreshold时间后触发
ProxyLeakTask
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/ProxyLeakTask.java
/**
* A Runnable that is scheduled in the future to report leaks. The ScheduledFuture is
* cancelled if the connection is closed before the leak time expires.
*
* @author Brett Wooldridge
*/
class ProxyLeakTask implements Runnable
{
private static final Logger LOGGER = LoggerFactory.getLogger(ProxyLeakTask.class);
static final ProxyLeakTask NO_LEAK;
private ScheduledFuture<?> scheduledFuture;
private String connectionName;
private Exception exception;
private String threadName;
private boolean isLeaked;
static
{
NO_LEAK = new ProxyLeakTask() {
@Override
void schedule(ScheduledExecutorService executorService, long leakDetectionThreshold) {}
@Override
public void run() {}
@Override
public void cancel() {}
};
}
ProxyLeakTask(final PoolEntry poolEntry)
{
this.exception = new Exception("Apparent connection leak detected");
this.threadName = Thread.currentThread().getName();
this.connectionName = poolEntry.connection.toString();
}
private ProxyLeakTask()
{
}
void schedule(ScheduledExecutorService executorService, long leakDetectionThreshold)
{
scheduledFuture = executorService.schedule(this, leakDetectionThreshold, TimeUnit.MILLISECONDS);
}
/** {@inheritDoc} */
@Override
public void run()
{
isLeaked = true;
final StackTraceElement[] stackTrace = exception.getStackTrace();
final StackTraceElement[] trace = new StackTraceElement[stackTrace.length - 5];
System.arraycopy(stackTrace, 5, trace, 0, trace.length);
exception.setStackTrace(trace);
LOGGER.warn("Connection leak detection triggered for {} on thread {}, stack trace follows", connectionName, threadName, exception);
}
void cancel()
{
scheduledFuture.cancel(false);
if (isLeaked) {
LOGGER.info("Previously reported leaked connection {} on thread {} was returned to the pool (unleaked)", connectionName, threadName);
}
}
}可以看到NO_LEAK类里头的方法都是空操作
一旦该task被触发，则抛出Exception("Apparent connection leak detected")
ProxyConnection.close
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/ProxyConnection.java
/** {@inheritDoc} */
@Override
public final void close() throws SQLException
{
// Closing statements can cause connection eviction, so this must run before the conditional below
closeStatements();
if (delegate != ClosedConnection.CLOSED_CONNECTION) {
leakTask.cancel();
try {
if (isCommitStateDirty && !isAutoCommit) {
delegate.rollback();
lastAccess = currentTime();
LOGGER.debug("{} - Executed rollback on connection {} due to dirty commit state on close().", poolEntry.getPoolName(), delegate);
}
if (dirtyBits != 0) {
poolEntry.resetConnectionState(this, dirtyBits);
lastAccess = currentTime();
}
delegate.clearWarnings();
}
catch (SQLException e) {
// when connections are aborted, exceptions are often thrown that should not reach the application
if (!poolEntry.isMarkedEvicted()) {
throw checkException(e);
}
}
finally {
delegate = ClosedConnection.CLOSED_CONNECTION;
poolEntry.recycle(lastAccess);
}
}
}
@SuppressWarnings("EmptyTryBlock")
private synchronized void closeStatements()
{
final int size = openStatements.size();
if (size > 0) {
for (int i = 0; i < size && delegate != ClosedConnection.CLOSED_CONNECTION; i++) {
try (Statement ignored = openStatements.get(i)) {
// automatic resource cleanup
}
catch (SQLException e) {
LOGGER.warn("{} - Connection {} marked as broken because of an exception closing open statements during Connection.close()",
poolEntry.getPoolName(), delegate);
leakTask.cancel();
poolEntry.evict("(exception closing Statements during Connection.close())");
delegate = ClosedConnection.CLOSED_CONNECTION;
}
}
openStatements.clear();
}
}
final SQLException checkException(SQLException sqle)
{
SQLException nse = sqle;
for (int depth = 0; delegate != ClosedConnection.CLOSED_CONNECTION && nse != null && depth < 10; depth++) {
final String sqlState = nse.getSQLState();
if (sqlState != null && sqlState.startsWith("08") || ERROR_STATES.contains(sqlState) || ERROR_CODES.contains(nse.getErrorCode())) {
// broken connection
LOGGER.warn("{} - Connection {} marked as broken because of SQLSTATE({}), ErrorCode({})",
poolEntry.getPoolName(), delegate, sqlState, nse.getErrorCode(), nse);
leakTask.cancel();
poolEntry.evict("(connection is broken)");
delegate = ClosedConnection.CLOSED_CONNECTION;
}
else {
nse = nse.getNextException();
}
}
return sqle;
}
连接有借有还，在connection的close的时候，closeStatements，checkException会调用leakTask.cancel();取消检测连接泄露的task。另外在delegate != ClosedConnection.CLOSED_CONNECTION的时候会显示调用leakTask.cancel();
HikariPool.evictConnection
HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java
/**
* Evict a Connection from the pool.
*
* @param connection the Connection to evict (actually a {@link ProxyConnection})
*/
public void evictConnection(Connection connection)
{
ProxyConnection proxyConnection = (ProxyConnection) connection;
proxyConnection.cancelLeakTask();
try {
softEvictConnection(proxyConnection.getPoolEntry(), "(connection evicted by user)", !connection.isClosed() /* owner */);
}
catch (SQLException e) {
// unreachable in HikariCP, but we're still forced to catch it
}
}如果用户手工调用evictConnection的话，也会cancelLeakTask
实例
/**
* leak-detection-threshold: 5000
* @throws SQLException
* @throws InterruptedException
*/
@Test
public void testConnLeak() throws SQLException, InterruptedException {
Connection conn = dataSource.getConnection();
TimeUnit.SECONDS.sleep(10);
String sql = "select 1";
PreparedStatement pstmt = null;
try {
pstmt = (PreparedStatement)conn.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();
int col = rs.getMetaData().getColumnCount();
while (rs.next()) {
for (int i = 1; i <= col; i++) {
System.out.print(rs.getObject(i));
}
System.out.println("");
}
System.out.println("============================");
} catch (Exception e) {
e.printStackTrace();
} finally {
//close resources
DbUtils.closeQuietly(pstmt);
DbUtils.closeQuietly(conn);
}
}输出
2018-01-29 22:46:31.028 WARN 1454 --- [l-1 housekeeper] com.zaxxer.hikari.pool.ProxyLeakTask : Connection leak detection triggered for org.postgresql.jdbc.PgConnection@3abd581e on thread main, stack trace follows
java.lang.Exception: Apparent connection leak detected
at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:123) ~[HikariCP-2.7.6.jar:na]
at com.example.demo.HikariDemoApplicationTests.testConnLeak(HikariDemoApplicationTests.java:48) ~[test-classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) ~[junit-4.12.jar:4.12]
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) ~[junit-4.12.jar:4.12]
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) ~[junit-4.12.jar:4.12]
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) ~[junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) ~[junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) ~[junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) ~[junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) ~[junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) ~[junit-4.12.jar:4.12]
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) ~[junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.junit.runners.ParentRunner.run(ParentRunner.java:363) ~[junit-4.12.jar:4.12]
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) ~[spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]
at org.junit.runner.JUnitCore.run(JUnitCore.java:137) ~[junit-4.12.jar:4.12]
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) ~[junit-rt.jar:na]
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234) ~[junit-rt.jar:na]
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74) ~[junit-rt.jar:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) ~[idea_rt.jar:na]
1可以看到ProxyLeakTask抛出java.lang.Exception: Apparent connection leak detected，但是这个是在Runnable中抛出的，并不影响主线程，主线程在超时过后，仍旧继续执行，最后输出结果。
小结
hikari连接池的leakDetectionThreshold用来设置连接被占用的超时时间，单位毫秒，默认为0，即禁用连接泄露检测。这个功能相当于tomcat jdbc pool的poolCleaner里头的checkAbandoned。
不同的如下：
- tomcat jdbc pool是采用一个timerTask，间隔timeBetweenEvictionRunsMillis时间允许一次；而hikari是每借用一个connection则会创建一个延时的定时任务，在归还或者出异常的时候cancel掉这个task
- tomcat jdbc pool是直接abandon连接即close掉，然后该connection在后续的收发数据时会抛出异常；而hikari则是在ProxyLeakTask中主动抛出Exception("Apparent connection leak detected")。因此前者是暴力的，后者只是在Runnable抛出异常，并不影响连接的后续操作。
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