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Ultimate JDBC Connection Pool
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/*
* Copyright (C) 2013,2014 Brett Wooldridge
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.zaxxer.hikari.pool;
import static com.zaxxer.hikari.pool.PoolEntry.LASTACCESS_REVERSE_COMPARABLE;
import static com.zaxxer.hikari.util.ClockSource.currentTime;
import static com.zaxxer.hikari.util.ClockSource.elapsedDisplayString;
import static com.zaxxer.hikari.util.ClockSource.elapsedMillis;
import static com.zaxxer.hikari.util.ClockSource.plusMillis;
import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_IN_USE;
import static com.zaxxer.hikari.util.ConcurrentBag.IConcurrentBagEntry.STATE_NOT_IN_USE;
import static com.zaxxer.hikari.util.UtilityElf.createThreadPoolExecutor;
import static com.zaxxer.hikari.util.UtilityElf.quietlySleep;
import static java.util.Collections.unmodifiableCollection;
import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.SECONDS;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.SQLTransientConnectionException;
import java.util.Collection;
import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.ThreadPoolExecutor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.health.HealthCheckRegistry;
import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariPoolMXBean;
import com.zaxxer.hikari.metrics.MetricsTrackerFactory;
import com.zaxxer.hikari.metrics.PoolStats;
import com.zaxxer.hikari.metrics.dropwizard.CodahaleHealthChecker;
import com.zaxxer.hikari.metrics.dropwizard.CodahaleMetricsTrackerFactory;
import com.zaxxer.hikari.util.ConcurrentBag;
import com.zaxxer.hikari.util.ConcurrentBag.IBagStateListener;
import com.zaxxer.hikari.util.SuspendResumeLock;
import com.zaxxer.hikari.util.UtilityElf.DefaultThreadFactory;
/**
* This is the primary connection pool class that provides the basic
* pooling behavior for HikariCP.
*
* @author Brett Wooldridge
*/
public final class HikariPool extends PoolBase implements HikariPoolMXBean, IBagStateListener
{
private final Logger LOGGER = LoggerFactory.getLogger(HikariPool.class);
private static final int POOL_NORMAL = 0;
private static final int POOL_SUSPENDED = 1;
private static final int POOL_SHUTDOWN = 2;
private volatile int poolState;
private final long ALIVE_BYPASS_WINDOW_MS = Long.getLong("com.zaxxer.hikari.aliveBypassWindowMs", MILLISECONDS.toMillis(500));
private final long HOUSEKEEPING_PERIOD_MS = Long.getLong("com.zaxxer.hikari.housekeeping.periodMs", SECONDS.toMillis(30));
private final PoolEntryCreator POOL_ENTRY_CREATOR = new PoolEntryCreator(null);
private final PoolEntryCreator POST_FILL_POOL_ENTRY_CREATOR = new PoolEntryCreator("After adding ");
private final Collection addConnectionQueue;
private final ThreadPoolExecutor addConnectionExecutor;
private final ThreadPoolExecutor closeConnectionExecutor;
private final ConcurrentBag connectionBag;
private final ProxyLeakTask leakTask;
private final SuspendResumeLock suspendResumeLock;
private ScheduledExecutorService houseKeepingExecutorService;
private ScheduledFuture houseKeeperTask;
/**
* 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 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.leakTask = new ProxyLeakTask(config.getLeakDetectionThreshold(), houseKeepingExecutorService);
this.houseKeeperTask = houseKeepingExecutorService.scheduleWithFixedDelay(new HouseKeeper(), 100L, HOUSEKEEPING_PERIOD_MS, MILLISECONDS);
}
/**
* 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;
PoolEntry poolEntry = null;
try {
do {
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, "(connection is evicted or dead)"); // Throw away the dead connection (passed max age or failed alive test)
timeout = hardTimeout - elapsedMillis(startTime);
}
else {
metricsTracker.recordBorrowStats(poolEntry, startTime);
return poolEntry.createProxyConnection(leakTask.schedule(poolEntry), now);
}
} while (timeout > 0L);
metricsTracker.recordBorrowTimeoutStats(startTime);
}
catch (InterruptedException e) {
if (poolEntry != null) {
poolEntry.recycle(startTime);
}
Thread.currentThread().interrupt();
throw new SQLException(poolName + " - Interrupted during connection acquisition", e);
}
}
finally {
suspendResumeLock.release();
}
throw createTimeoutException(startTime);
}
/**
* Shutdown the pool, closing all idle connections and aborting or closing
* active connections.
*
* @throws InterruptedException thrown if the thread is interrupted during shutdown
*/
public synchronized void shutdown() throws InterruptedException
{
try {
poolState = POOL_SHUTDOWN;
if (addConnectionExecutor == null) {
return;
}
logPoolState("Before shutdown ");
if (houseKeeperTask != null) {
houseKeeperTask.cancel(false);
houseKeeperTask = null;
}
softEvictConnections();
addConnectionExecutor.shutdown();
addConnectionExecutor.awaitTermination(5L, SECONDS);
destroyHouseKeepingExecutorService();
connectionBag.close();
final ExecutorService assassinExecutor = createThreadPoolExecutor(config.getMaximumPoolSize(), poolName + " connection assassinator",
config.getThreadFactory(), new ThreadPoolExecutor.CallerRunsPolicy());
try {
final long start = currentTime();
do {
abortActiveConnections(assassinExecutor);
softEvictConnections();
} while (getTotalConnections() > 0 && elapsedMillis(start) < SECONDS.toMillis(5));
}
finally {
assassinExecutor.shutdown();
assassinExecutor.awaitTermination(5L, SECONDS);
}
shutdownNetworkTimeoutExecutor();
closeConnectionExecutor.shutdown();
closeConnectionExecutor.awaitTermination(5L, SECONDS);
}
finally {
logPoolState("After shutdown ");
unregisterMBeans();
metricsTracker.close();
}
}
/**
* Evict a connection from the pool.
*
* @param connection the connection to evict
*/
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
}
}
public void setMetricRegistry(Object metricRegistry)
{
if (metricRegistry != null) {
setMetricsTrackerFactory(new CodahaleMetricsTrackerFactory((MetricRegistry) metricRegistry));
}
else {
setMetricsTrackerFactory(null);
}
}
public void setMetricsTrackerFactory(MetricsTrackerFactory metricsTrackerFactory)
{
if (metricsTrackerFactory != null) {
this.metricsTracker = new MetricsTrackerDelegate(metricsTrackerFactory.create(config.getPoolName(), getPoolStats()));
}
else {
this.metricsTracker = new NopMetricsTrackerDelegate();
}
}
public void setHealthCheckRegistry(Object healthCheckRegistry)
{
if (healthCheckRegistry != null) {
CodahaleHealthChecker.registerHealthChecks(this, config, (HealthCheckRegistry) healthCheckRegistry);
}
}
// ***********************************************************************
// IBagStateListener callback
// ***********************************************************************
/** {@inheritDoc} */
@Override
public Future addBagItem(final int waiting)
{
final boolean shouldAdd = waiting - addConnectionQueue.size() >= 0; // Yes, >= is intentional.
if (shouldAdd) {
return addConnectionExecutor.submit(POOL_ENTRY_CREATOR);
}
return CompletableFuture.completedFuture(Boolean.TRUE);
}
// ***********************************************************************
// HikariPoolMBean methods
// ***********************************************************************
/** {@inheritDoc} */
@Override
public int getActiveConnections()
{
return connectionBag.getCount(STATE_IN_USE);
}
/** {@inheritDoc} */
@Override
public int getIdleConnections()
{
return connectionBag.getCount(STATE_NOT_IN_USE);
}
/** {@inheritDoc} */
@Override
public int getTotalConnections()
{
return connectionBag.size();
}
/** {@inheritDoc} */
@Override
public int getThreadsAwaitingConnection()
{
return connectionBag.getWaitingThreadCount();
}
/** {@inheritDoc} */
@Override
public void softEvictConnections()
{
connectionBag.values().forEach(poolEntry -> softEvictConnection(poolEntry, "(connection evicted)", false /* not owner */));
}
/** {@inheritDoc} */
@Override
public synchronized void suspendPool()
{
if (suspendResumeLock == SuspendResumeLock.FAUX_LOCK) {
throw new IllegalStateException(poolName + " - is not suspendable");
}
else if (poolState != POOL_SUSPENDED) {
suspendResumeLock.suspend();
poolState = POOL_SUSPENDED;
}
}
/** {@inheritDoc} */
@Override
public synchronized void resumePool()
{
if (poolState == POOL_SUSPENDED) {
poolState = POOL_NORMAL;
fillPool();
suspendResumeLock.resume();
}
}
// ***********************************************************************
// Package methods
// ***********************************************************************
/**
* Log the current pool state at debug level.
*
* @param prefix an optional prefix to prepend the log message
*/
void logPoolState(String... prefix)
{
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("{} - {}stats (total={}, active={}, idle={}, waiting={})",
poolName, (prefix.length > 0 ? prefix[0] : ""),
getTotalConnections(), getActiveConnections(), getIdleConnections(), getThreadsAwaitingConnection());
}
}
/**
* Recycle PoolEntry (add back to the pool)
*
* @param poolEntry the PoolEntry to recycle
*/
@Override
void recycle(final PoolEntry poolEntry)
{
metricsTracker.recordConnectionUsage(poolEntry);
connectionBag.requite(poolEntry);
}
/**
* Permanently close the real (underlying) connection (eat any exception).
*
* @param poolEntry poolEntry having the connection to close
* @param closureReason reason to close
*/
void closeConnection(final PoolEntry poolEntry, final String closureReason)
{
if (connectionBag.remove(poolEntry)) {
final Connection connection = poolEntry.close();
closeConnectionExecutor.execute(() -> {
quietlyCloseConnection(connection, closureReason);
if (poolState == POOL_NORMAL) {
fillPool();
}
});
}
}
@SuppressWarnings("unused")
int[] getPoolStateCounts()
{
return connectionBag.getStateCounts();
}
// ***********************************************************************
// Private methods
// ***********************************************************************
/**
* Creating new poolEntry.
*/
private PoolEntry createPoolEntry()
{
try {
final PoolEntry poolEntry = newPoolEntry();
final long maxLifetime = config.getMaxLifetime();
if (maxLifetime > 0) {
// variance up to 2.5% of the maxlifetime
final long variance = maxLifetime > 10_000 ? ThreadLocalRandom.current().nextLong( maxLifetime / 40 ) : 0;
final long lifetime = maxLifetime - variance;
poolEntry.setFutureEol(houseKeepingExecutorService.schedule(
() -> {
if (softEvictConnection(poolEntry, "(connection has passed maxLifetime)", false /* not owner */)) {
addBagItem(connectionBag.getWaitingThreadCount());
}
},
lifetime, MILLISECONDS));
}
return poolEntry;
}
catch (Exception e) {
if (poolState == POOL_NORMAL) {
LOGGER.debug("{} - Cannot acquire connection from data source", poolName, (e instanceof ConnectionSetupException ? e.getCause() : e));
}
return null;
}
}
/**
* Fill pool up from current idle connections (as they are perceived at the point of execution) to minimumIdle connections.
*/
private synchronized void fillPool()
{
final int connectionsToAdd = Math.min(config.getMaximumPoolSize() - getTotalConnections(), config.getMinimumIdle() - getIdleConnections())
- addConnectionQueue.size();
for (int i = 0; i < connectionsToAdd; i++) {
addConnectionExecutor.submit((i < connectionsToAdd - 1) ? POOL_ENTRY_CREATOR : POST_FILL_POOL_ENTRY_CREATOR);
}
}
/**
* Attempt to abort or close active connections.
*/
private void abortActiveConnections(final ExecutorService assassinExecutor)
{
for (PoolEntry poolEntry : connectionBag.values(STATE_IN_USE)) {
Connection connection = poolEntry.close();
try {
connection.abort(assassinExecutor);
}
catch (Throwable e) {
quietlyCloseConnection(connection, "(connection aborted during shutdown)");
}
finally {
connectionBag.remove(poolEntry);
}
}
}
/**
* If initializationFailFast is configured, check that we have DB connectivity.
*
* @throws PoolInitializationException if fails to create or validate connection
*/
private void checkFailFast()
{
final long initializationTimeout = config.getInitializationFailTimeout();
if (initializationTimeout < 0) {
return;
}
final long startTime = currentTime();
do {
final PoolEntry poolEntry = createPoolEntry();
if (poolEntry != null) {
if (config.getMinimumIdle() > 0) {
connectionBag.add(poolEntry);
LOGGER.debug("{} - Added connection {}", poolName, poolEntry.connection);
}
else {
quietlyCloseConnection(poolEntry.close(), "(initialization check complete and minimumIdle is zero)");
}
return;
}
if (getLastConnectionFailure() instanceof ConnectionSetupException) {
throwPoolInitializationException(getLastConnectionFailure().getCause());
}
quietlySleep(1000L);
} while (elapsedMillis(startTime) < initializationTimeout);
if (initializationTimeout > 0) {
throwPoolInitializationException(getLastConnectionFailure());
}
}
private void throwPoolInitializationException(Throwable t)
{
LOGGER.error("{} - Exception during pool initialization.", poolName, t);
destroyHouseKeepingExecutorService();
throw new PoolInitializationException(t);
}
private boolean softEvictConnection(final PoolEntry poolEntry, final String reason, final boolean owner)
{
poolEntry.markEvicted();
if (owner || connectionBag.reserve(poolEntry)) {
closeConnection(poolEntry, reason);
return true;
}
return false;
}
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();
}
}
private void destroyHouseKeepingExecutorService()
{
if (config.getScheduledExecutor() == null) {
houseKeepingExecutorService.shutdownNow();
}
}
private PoolStats getPoolStats()
{
return new PoolStats(SECONDS.toMillis(1)) {
@Override
protected void update() {
this.pendingThreads = HikariPool.this.getThreadsAwaitingConnection();
this.idleConnections = HikariPool.this.getIdleConnections();
this.totalConnections = HikariPool.this.getTotalConnections();
this.activeConnections = HikariPool.this.getActiveConnections();
}
};
}
private SQLException createTimeoutException(long startTime)
{
logPoolState("Timeout failure ");
metricsTracker.recordConnectionTimeout();
String sqlState = null;
final Throwable originalException = getLastConnectionFailure();
if (originalException instanceof SQLException) {
sqlState = ((SQLException) originalException).getSQLState();
}
final SQLException connectionException = new SQLTransientConnectionException(poolName + " - Connection is not available, request timed out after " + elapsedMillis(startTime) + "ms.", sqlState, originalException);
if (originalException instanceof SQLException) {
connectionException.setNextException((SQLException) originalException);
}
return connectionException;
}
// ***********************************************************************
// Non-anonymous Inner-classes
// ***********************************************************************
/**
* Creating and adding poolEntries (connections) to the pool.
*/
private final class PoolEntryCreator implements Callable
{
private final String loggingPrefix;
PoolEntryCreator(String loggingPrefix)
{
this.loggingPrefix = loggingPrefix;
}
@Override
public Boolean call() throws Exception
{
long sleepBackoff = 250L;
while (poolState == POOL_NORMAL && shouldCreateAnotherConnection()) {
final PoolEntry poolEntry = createPoolEntry();
if (poolEntry != null) {
connectionBag.add(poolEntry);
LOGGER.debug("{} - Added connection {}", poolName, poolEntry.connection);
if (loggingPrefix != null) {
logPoolState(loggingPrefix);
}
return Boolean.TRUE;
}
// failed to get connection from db, sleep and retry
quietlySleep(sleepBackoff);
sleepBackoff = Math.min(SECONDS.toMillis(10), Math.min(connectionTimeout, (long) (sleepBackoff * 1.5)));
}
// Pool is suspended or shutdown or at max size
return Boolean.FALSE;
}
private boolean shouldCreateAnotherConnection() {
// only create connections if we need another idle connection or have threads still waiting
// for a new connection, otherwise bail
return getTotalConnections() < config.getMaximumPoolSize() &&
(connectionBag.getWaitingThreadCount() > 0 || getIdleConnections() < config.getMinimumIdle());
}
}
/**
* The house keeping task to retire and maintain minimum idle connections.
*/
private final class HouseKeeper implements Runnable
{
private volatile long previous = plusMillis(currentTime(), -HOUSEKEEPING_PERIOD_MS);
@Override
public void run()
{
try {
// refresh timeouts in case they changed via MBean
connectionTimeout = config.getConnectionTimeout();
validationTimeout = config.getValidationTimeout();
leakTask.updateLeakDetectionThreshold(config.getLeakDetectionThreshold());
final long idleTimeout = config.getIdleTimeout();
final long now = currentTime();
// Detect retrograde time, allowing +128ms as per NTP spec.
if (plusMillis(now, 128) < plusMillis(previous, HOUSEKEEPING_PERIOD_MS)) {
LOGGER.warn("{} - Retrograde clock change detected (housekeeper delta={}), soft-evicting connections from pool.",
poolName, elapsedDisplayString(previous, now));
previous = now;
softEvictConnections();
fillPool();
return;
}
else if (now > plusMillis(previous, (3 * HOUSEKEEPING_PERIOD_MS) / 2)) {
// No point evicting for forward clock motion, this merely accelerates connection retirement anyway
LOGGER.warn("{} - Thread starvation or clock leap detected (housekeeper delta={}).", poolName, elapsedDisplayString(previous, now));
}
previous = now;
String afterPrefix = "Pool ";
if (idleTimeout > 0L && config.getMinimumIdle() < config.getMaximumPoolSize()) {
logPoolState("Before cleanup ");
afterPrefix = "After cleanup ";
connectionBag
.values(STATE_NOT_IN_USE)
.stream()
.sorted(LASTACCESS_REVERSE_COMPARABLE)
.skip(config.getMinimumIdle())
.filter(p -> elapsedMillis(p.lastAccessed, now) > idleTimeout)
.filter(connectionBag::reserve)
.forEachOrdered(p -> closeConnection(p, "(connection has passed idleTimeout)"));
}
logPoolState(afterPrefix);
fillPool(); // Try to maintain minimum connections
}
catch (Exception e) {
LOGGER.error("Unexpected exception in housekeeping task", e);
}
}
}
public static class PoolInitializationException extends RuntimeException
{
private static final long serialVersionUID = 929872118275916520L;
/**
* Construct an exception, possibly wrapping the provided Throwable as the cause.
* @param t the Throwable to wrap
*/
public PoolInitializationException(Throwable t)
{
super("Failed to initialize pool: " + t.getMessage(), t);
}
}
}
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