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Apache Commons Object Pooling Library
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.pool2.impl;
import org.apache.commons.pool2.DestroyMode;
import org.apache.commons.pool2.ObjectPool;
import org.apache.commons.pool2.PoolUtils;
import org.apache.commons.pool2.PooledObject;
import org.apache.commons.pool2.PooledObjectFactory;
import org.apache.commons.pool2.PooledObjectState;
import org.apache.commons.pool2.SwallowedExceptionListener;
import org.apache.commons.pool2.TrackedUse;
import org.apache.commons.pool2.UsageTracking;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
/**
* A configurable {@link ObjectPool} implementation.
*
* When coupled with the appropriate {@link PooledObjectFactory},
* {@code GenericObjectPool} provides robust pooling functionality for
* arbitrary objects.
*
*
* Optionally, one may configure the pool to examine and possibly evict objects
* as they sit idle in the pool and to ensure that a minimum number of idle
* objects are available. This is performed by an "idle object eviction" thread,
* which runs asynchronously. Caution should be used when configuring this
* optional feature. Eviction runs contend with client threads for access to
* objects in the pool, so if they run too frequently performance issues may
* result.
*
*
* The pool can also be configured to detect and remove "abandoned" objects,
* i.e. objects that have been checked out of the pool but neither used nor
* returned before the configured
* {@link AbandonedConfig#getRemoveAbandonedTimeout() removeAbandonedTimeout}.
* Abandoned object removal can be configured to happen when
* {@code borrowObject} is invoked and the pool is close to starvation, or
* it can be executed by the idle object evictor, or both. If pooled objects
* implement the {@link TrackedUse} interface, their last use will be queried
* using the {@code getLastUsed} method on that interface; otherwise
* abandonment is determined by how long an object has been checked out from
* the pool.
*
*
* Implementation note: To prevent possible deadlocks, care has been taken to
* ensure that no call to a factory method will occur within a synchronization
* block. See POOL-125 and DBCP-44 for more information.
*
*
* This class is intended to be thread-safe.
*
*
* @see GenericKeyedObjectPool
*
* @param Type of element pooled in this pool.
*
* @since 2.0
*/
public class GenericObjectPool extends BaseGenericObjectPool
implements ObjectPool, GenericObjectPoolMXBean, UsageTracking {
/**
* Creates a new {@code GenericObjectPool} using defaults from
* {@link GenericObjectPoolConfig}.
*
* @param factory The object factory to be used to create object instances
* used by this pool
*/
public GenericObjectPool(final PooledObjectFactory factory) {
this(factory, new GenericObjectPoolConfig());
}
/**
* Creates a new {@code GenericObjectPool} using a specific
* configuration.
*
* @param factory The object factory to be used to create object instances
* used by this pool
* @param config The configuration to use for this pool instance. The
* configuration is used by value. Subsequent changes to
* the configuration object will not be reflected in the
* pool.
*/
public GenericObjectPool(final PooledObjectFactory factory,
final GenericObjectPoolConfig config) {
super(config, ONAME_BASE, config.getJmxNamePrefix());
if (factory == null) {
jmxUnregister(); // tidy up
throw new IllegalArgumentException("factory may not be null");
}
this.factory = factory;
idleObjects = new LinkedBlockingDeque<>(config.getFairness());
setConfig(config);
}
/**
* Creates a new {@code GenericObjectPool} that tracks and destroys
* objects that are checked out, but never returned to the pool.
*
* @param factory The object factory to be used to create object instances
* used by this pool
* @param config The base pool configuration to use for this pool instance.
* The configuration is used by value. Subsequent changes to
* the configuration object will not be reflected in the
* pool.
* @param abandonedConfig Configuration for abandoned object identification
* and removal. The configuration is used by value.
*/
public GenericObjectPool(final PooledObjectFactory factory,
final GenericObjectPoolConfig config, final AbandonedConfig abandonedConfig) {
this(factory, config);
setAbandonedConfig(abandonedConfig);
}
/**
* Returns the cap on the number of "idle" instances in the pool. If maxIdle
* is set too low on heavily loaded systems it is possible you will see
* objects being destroyed and almost immediately new objects being created.
* This is a result of the active threads momentarily returning objects
* faster than they are requesting them, causing the number of idle
* objects to rise above maxIdle. The best value for maxIdle for heavily
* loaded system will vary but the default is a good starting point.
*
* @return the maximum number of "idle" instances that can be held in the
* pool or a negative value if there is no limit
*
* @see #setMaxIdle
*/
@Override
public int getMaxIdle() {
return maxIdle;
}
/**
* Returns the cap on the number of "idle" instances in the pool. If maxIdle
* is set too low on heavily loaded systems it is possible you will see
* objects being destroyed and almost immediately new objects being created.
* This is a result of the active threads momentarily returning objects
* faster than they are requesting them, causing the number of idle
* objects to rise above maxIdle. The best value for maxIdle for heavily
* loaded system will vary but the default is a good starting point.
*
* @param maxIdle
* The cap on the number of "idle" instances in the pool. Use a
* negative value to indicate an unlimited number of idle
* instances
*
* @see #getMaxIdle
*/
public void setMaxIdle(final int maxIdle) {
this.maxIdle = maxIdle;
}
/**
* Sets the target for the minimum number of idle objects to maintain in
* the pool. This setting only has an effect if it is positive and
* {@link #getTimeBetweenEvictionRunsMillis()} is greater than zero. If this
* is the case, an attempt is made to ensure that the pool has the required
* minimum number of instances during idle object eviction runs.
*
* If the configured value of minIdle is greater than the configured value
* for maxIdle then the value of maxIdle will be used instead.
*
*
* @param minIdle
* The minimum number of objects.
*
* @see #getMinIdle()
* @see #getMaxIdle()
* @see #getTimeBetweenEvictionRunsMillis()
*/
public void setMinIdle(final int minIdle) {
this.minIdle = minIdle;
}
/**
* Returns the target for the minimum number of idle objects to maintain in
* the pool. This setting only has an effect if it is positive and
* {@link #getTimeBetweenEvictionRunsMillis()} is greater than zero. If this
* is the case, an attempt is made to ensure that the pool has the required
* minimum number of instances during idle object eviction runs.
*
* If the configured value of minIdle is greater than the configured value
* for maxIdle then the value of maxIdle will be used instead.
*
*
* @return The minimum number of objects.
*
* @see #setMinIdle(int)
* @see #setMaxIdle(int)
* @see #setTimeBetweenEvictionRunsMillis(long)
*/
@Override
public int getMinIdle() {
final int maxIdleSave = getMaxIdle();
if (this.minIdle > maxIdleSave) {
return maxIdleSave;
}
return minIdle;
}
/**
* Gets whether or not abandoned object removal is configured for this pool.
*
* @return true if this pool is configured to detect and remove
* abandoned objects
*/
@Override
public boolean isAbandonedConfig() {
return abandonedConfig != null;
}
/**
* Gets whether this pool identifies and logs any abandoned objects.
*
* @return {@code true} if abandoned object removal is configured for this
* pool and removal events are to be logged otherwise {@code false}
*
* @see AbandonedConfig#getLogAbandoned()
*/
@Override
public boolean getLogAbandoned() {
final AbandonedConfig ac = this.abandonedConfig;
return ac != null && ac.getLogAbandoned();
}
/**
* Gets whether a check is made for abandoned objects when an object is borrowed
* from this pool.
*
* @return {@code true} if abandoned object removal is configured to be
* activated by borrowObject otherwise {@code false}
*
* @see AbandonedConfig#getRemoveAbandonedOnBorrow()
*/
@Override
public boolean getRemoveAbandonedOnBorrow() {
final AbandonedConfig ac = this.abandonedConfig;
return ac != null && ac.getRemoveAbandonedOnBorrow();
}
/**
* Gets whether a check is made for abandoned objects when the evictor runs.
*
* @return {@code true} if abandoned object removal is configured to be
* activated when the evictor runs otherwise {@code false}
*
* @see AbandonedConfig#getRemoveAbandonedOnMaintenance()
*/
@Override
public boolean getRemoveAbandonedOnMaintenance() {
final AbandonedConfig ac = this.abandonedConfig;
return ac != null && ac.getRemoveAbandonedOnMaintenance();
}
/**
* Obtains the timeout before which an object will be considered to be
* abandoned by this pool.
*
* @return The abandoned object timeout in seconds if abandoned object
* removal is configured for this pool; Integer.MAX_VALUE otherwise.
*
* @see AbandonedConfig#getRemoveAbandonedTimeout()
*/
@Override
public int getRemoveAbandonedTimeout() {
final AbandonedConfig ac = this.abandonedConfig;
return ac != null ? ac.getRemoveAbandonedTimeout() : Integer.MAX_VALUE;
}
/**
* Sets the base pool configuration.
*
* @param conf the new configuration to use. This is used by value.
*
* @see GenericObjectPoolConfig
*/
public void setConfig(final GenericObjectPoolConfig conf) {
super.setConfig(conf);
setMaxIdle(conf.getMaxIdle());
setMinIdle(conf.getMinIdle());
setMaxTotal(conf.getMaxTotal());
}
/**
* Sets the abandoned object removal configuration.
*
* @param abandonedConfig the new configuration to use. This is used by value.
*
* @see AbandonedConfig
*/
@SuppressWarnings("resource") // PrintWriter is managed elsewhere
public void setAbandonedConfig(final AbandonedConfig abandonedConfig) {
if (abandonedConfig == null) {
this.abandonedConfig = null;
} else {
this.abandonedConfig = new AbandonedConfig();
this.abandonedConfig.setLogAbandoned(abandonedConfig.getLogAbandoned());
this.abandonedConfig.setLogWriter(abandonedConfig.getLogWriter());
this.abandonedConfig.setRemoveAbandonedOnBorrow(abandonedConfig.getRemoveAbandonedOnBorrow());
this.abandonedConfig.setRemoveAbandonedOnMaintenance(abandonedConfig.getRemoveAbandonedOnMaintenance());
this.abandonedConfig.setRemoveAbandonedTimeout(abandonedConfig.getRemoveAbandonedTimeout());
this.abandonedConfig.setUseUsageTracking(abandonedConfig.getUseUsageTracking());
this.abandonedConfig.setRequireFullStackTrace(abandonedConfig.getRequireFullStackTrace());
}
}
/**
* Obtains a reference to the factory used to create, destroy and validate
* the objects used by this pool.
*
* @return the factory
*/
public PooledObjectFactory getFactory() {
return factory;
}
/**
* Equivalent to {@link #borrowObject(long)
* borrowObject}({@link #getMaxWaitMillis()}).
*
* {@inheritDoc}
*
*/
@Override
public T borrowObject() throws Exception {
return borrowObject(getMaxWaitMillis());
}
/**
* Borrows an object from the pool using the specific waiting time which only
* applies if {@link #getBlockWhenExhausted()} is true.
*
* If there is one or more idle instance available in the pool, then an
* idle instance will be selected based on the value of {@link #getLifo()},
* activated and returned. If activation fails, or {@link #getTestOnBorrow()
* testOnBorrow} is set to {@code true} and validation fails, the
* instance is destroyed and the next available instance is examined. This
* continues until either a valid instance is returned or there are no more
* idle instances available.
*
*
* If there are no idle instances available in the pool, behavior depends on
* the {@link #getMaxTotal() maxTotal}, (if applicable)
* {@link #getBlockWhenExhausted()} and the value passed in to the
* {@code borrowMaxWaitMillis} parameter. If the number of instances
* checked out from the pool is less than {@code maxTotal,} a new
* instance is created, activated and (if applicable) validated and returned
* to the caller. If validation fails, a {@code NoSuchElementException}
* is thrown.
*
*
* If the pool is exhausted (no available idle instances and no capacity to
* create new ones), this method will either block (if
* {@link #getBlockWhenExhausted()} is true) or throw a
* {@code NoSuchElementException} (if
* {@link #getBlockWhenExhausted()} is false). The length of time that this
* method will block when {@link #getBlockWhenExhausted()} is true is
* determined by the value passed in to the {@code borrowMaxWaitMillis}
* parameter.
*
*
* When the pool is exhausted, multiple calling threads may be
* simultaneously blocked waiting for instances to become available. A
* "fairness" algorithm has been implemented to ensure that threads receive
* available instances in request arrival order.
*
*
* @param borrowMaxWaitMillis The time to wait in milliseconds for an object
* to become available
*
* @return object instance from the pool
*
* @throws NoSuchElementException if an instance cannot be returned
*
* @throws Exception if an object instance cannot be returned due to an
* error
*/
public T borrowObject(final long borrowMaxWaitMillis) throws Exception {
assertOpen();
final AbandonedConfig ac = this.abandonedConfig;
if (ac != null && ac.getRemoveAbandonedOnBorrow() &&
(getNumIdle() < 2) &&
(getNumActive() > getMaxTotal() - 3) ) {
removeAbandoned(ac);
}
PooledObject p = null;
// Get local copy of current config so it is consistent for entire
// method execution
final boolean blockWhenExhausted = getBlockWhenExhausted();
boolean create;
final long waitTime = System.currentTimeMillis();
while (p == null) {
create = false;
p = idleObjects.pollFirst();
if (p == null) {
p = create();
if (p != null) {
create = true;
}
}
if (blockWhenExhausted) {
if (p == null) {
if (borrowMaxWaitMillis < 0) {
p = idleObjects.takeFirst();
} else {
p = idleObjects.pollFirst(borrowMaxWaitMillis,
TimeUnit.MILLISECONDS);
}
}
if (p == null) {
throw new NoSuchElementException(
"Timeout waiting for idle object");
}
} else {
if (p == null) {
throw new NoSuchElementException("Pool exhausted");
}
}
if (!p.allocate()) {
p = null;
}
if (p != null) {
try {
factory.activateObject(p);
} catch (final Exception e) {
try {
destroy(p, DestroyMode.NORMAL);
} catch (final Exception e1) {
// Ignore - activation failure is more important
}
p = null;
if (create) {
final NoSuchElementException nsee = new NoSuchElementException(
"Unable to activate object");
nsee.initCause(e);
throw nsee;
}
}
if (p != null && getTestOnBorrow()) {
boolean validate = false;
Throwable validationThrowable = null;
try {
validate = factory.validateObject(p);
} catch (final Throwable t) {
PoolUtils.checkRethrow(t);
validationThrowable = t;
}
if (!validate) {
try {
destroy(p, DestroyMode.NORMAL);
destroyedByBorrowValidationCount.incrementAndGet();
} catch (final Exception e) {
// Ignore - validation failure is more important
}
p = null;
if (create) {
final NoSuchElementException nsee = new NoSuchElementException(
"Unable to validate object");
nsee.initCause(validationThrowable);
throw nsee;
}
}
}
}
}
updateStatsBorrow(p, System.currentTimeMillis() - waitTime);
return p.getObject();
}
/**
* {@inheritDoc}
*
* If {@link #getMaxIdle() maxIdle} is set to a positive value and the
* number of idle instances has reached this value, the returning instance
* is destroyed.
*
*
* If {@link #getTestOnReturn() testOnReturn} == true, the returning
* instance is validated before being returned to the idle instance pool. In
* this case, if validation fails, the instance is destroyed.
*
*
* Exceptions encountered destroying objects for any reason are swallowed
* but notified via a {@link SwallowedExceptionListener}.
*
*/
@Override
public void returnObject(final T obj) {
final PooledObject p = allObjects.get(new IdentityWrapper<>(obj));
if (p == null) {
if (!isAbandonedConfig()) {
throw new IllegalStateException(
"Returned object not currently part of this pool");
}
return; // Object was abandoned and removed
}
markReturningState(p);
final long activeTime = p.getActiveTimeMillis();
if (getTestOnReturn() && !factory.validateObject(p)) {
try {
destroy(p, DestroyMode.NORMAL);
} catch (final Exception e) {
swallowException(e);
}
try {
ensureIdle(1, false);
} catch (final Exception e) {
swallowException(e);
}
updateStatsReturn(activeTime);
return;
}
try {
factory.passivateObject(p);
} catch (final Exception e1) {
swallowException(e1);
try {
destroy(p, DestroyMode.NORMAL);
} catch (final Exception e) {
swallowException(e);
}
try {
ensureIdle(1, false);
} catch (final Exception e) {
swallowException(e);
}
updateStatsReturn(activeTime);
return;
}
if (!p.deallocate()) {
throw new IllegalStateException(
"Object has already been returned to this pool or is invalid");
}
final int maxIdleSave = getMaxIdle();
if (isClosed() || maxIdleSave > -1 && maxIdleSave <= idleObjects.size()) {
try {
destroy(p, DestroyMode.NORMAL);
} catch (final Exception e) {
swallowException(e);
}
try {
ensureIdle(1, false);
} catch (final Exception e) {
swallowException(e);
}
} else {
if (getLifo()) {
idleObjects.addFirst(p);
} else {
idleObjects.addLast(p);
}
if (isClosed()) {
// Pool closed while object was being added to idle objects.
// Make sure the returned object is destroyed rather than left
// in the idle object pool (which would effectively be a leak)
clear();
}
}
updateStatsReturn(activeTime);
}
/**
* {@inheritDoc}
*
* Activation of this method decrements the active count and attempts to
* destroy the instance, using the default (NORMAL) {@link DestroyMode}.
*
*
* @throws Exception if an exception occurs destroying the
* object
* @throws IllegalStateException if obj does not belong to this pool
*/
@Override
public void invalidateObject(final T obj) throws Exception {
invalidateObject(obj, DestroyMode.NORMAL);
}
/**
* {@inheritDoc}
*
* Activation of this method decrements the active count and attempts to
* destroy the instance, using the provided {@link DestroyMode}.
*
*
* @throws Exception if an exception occurs destroying the
* object
* @throws IllegalStateException if obj does not belong to this pool
* @since 2.9.0
*/
@Override
public void invalidateObject(final T obj, final DestroyMode mode) throws Exception {
final PooledObject p = allObjects.get(new IdentityWrapper<>(obj));
if (p == null) {
if (isAbandonedConfig()) {
return;
}
throw new IllegalStateException(
"Invalidated object not currently part of this pool");
}
synchronized (p) {
if (p.getState() != PooledObjectState.INVALID) {
destroy(p, mode);
}
}
ensureIdle(1, false);
}
/**
* Clears any objects sitting idle in the pool by removing them from the
* idle instance pool and then invoking the configured
* {@link PooledObjectFactory#destroyObject(PooledObject)} method on each
* idle instance.
*
* Implementation notes:
*
*
* - This method does not destroy or effect in any way instances that are
* checked out of the pool when it is invoked.
* - Invoking this method does not prevent objects being returned to the
* idle instance pool, even during its execution. Additional instances may
* be returned while removed items are being destroyed.
* - Exceptions encountered destroying idle instances are swallowed
* but notified via a {@link SwallowedExceptionListener}.
*
*/
@Override
public void clear() {
PooledObject p = idleObjects.poll();
while (p != null) {
try {
destroy(p, DestroyMode.NORMAL);
} catch (final Exception e) {
swallowException(e);
}
p = idleObjects.poll();
}
}
@Override
public int getNumActive() {
return allObjects.size() - idleObjects.size();
}
@Override
public int getNumIdle() {
return idleObjects.size();
}
/**
* Closes the pool. Once the pool is closed, {@link #borrowObject()} will
* fail with IllegalStateException, but {@link #returnObject(Object)} and
* {@link #invalidateObject(Object)} will continue to work, with returned
* objects destroyed on return.
*
* Destroys idle instances in the pool by invoking {@link #clear()}.
*
*/
@Override
public void close() {
if (isClosed()) {
return;
}
synchronized (closeLock) {
if (isClosed()) {
return;
}
// Stop the evictor before the pool is closed since evict() calls
// assertOpen()
stopEvictor();
closed = true;
// This clear removes any idle objects
clear();
jmxUnregister();
// Release any threads that were waiting for an object
idleObjects.interuptTakeWaiters();
}
}
/**
* {@inheritDoc}
*
* Successive activations of this method examine objects in sequence,
* cycling through objects in oldest-to-youngest order.
*
*/
@Override
public void evict() throws Exception {
assertOpen();
if (idleObjects.size() > 0) {
PooledObject underTest = null;
final EvictionPolicy evictionPolicy = getEvictionPolicy();
synchronized (evictionLock) {
final EvictionConfig evictionConfig = new EvictionConfig(
getMinEvictableIdleTimeMillis(),
getSoftMinEvictableIdleTimeMillis(),
getMinIdle());
final boolean testWhileIdle = getTestWhileIdle();
for (int i = 0, m = getNumTests(); i < m; i++) {
if (evictionIterator == null || !evictionIterator.hasNext()) {
evictionIterator = new EvictionIterator(idleObjects);
}
if (!evictionIterator.hasNext()) {
// Pool exhausted, nothing to do here
return;
}
try {
underTest = evictionIterator.next();
} catch (final NoSuchElementException nsee) {
// Object was borrowed in another thread
// Don't count this as an eviction test so reduce i;
i--;
evictionIterator = null;
continue;
}
if (!underTest.startEvictionTest()) {
// Object was borrowed in another thread
// Don't count this as an eviction test so reduce i;
i--;
continue;
}
// User provided eviction policy could throw all sorts of
// crazy exceptions. Protect against such an exception
// killing the eviction thread.
boolean evict;
try {
evict = evictionPolicy.evict(evictionConfig, underTest,
idleObjects.size());
} catch (final Throwable t) {
// Slightly convoluted as SwallowedExceptionListener
// uses Exception rather than Throwable
PoolUtils.checkRethrow(t);
swallowException(new Exception(t));
// Don't evict on error conditions
evict = false;
}
if (evict) {
destroy(underTest, DestroyMode.NORMAL);
destroyedByEvictorCount.incrementAndGet();
} else {
if (testWhileIdle) {
boolean active = false;
try {
factory.activateObject(underTest);
active = true;
} catch (final Exception e) {
destroy(underTest, DestroyMode.NORMAL);
destroyedByEvictorCount.incrementAndGet();
}
if (active) {
if (!factory.validateObject(underTest)) {
destroy(underTest, DestroyMode.NORMAL);
destroyedByEvictorCount.incrementAndGet();
} else {
try {
factory.passivateObject(underTest);
} catch (final Exception e) {
destroy(underTest, DestroyMode.NORMAL);
destroyedByEvictorCount.incrementAndGet();
}
}
}
}
if (!underTest.endEvictionTest(idleObjects)) {
// TODO - May need to add code here once additional
// states are used
}
}
}
}
}
final AbandonedConfig ac = this.abandonedConfig;
if (ac != null && ac.getRemoveAbandonedOnMaintenance()) {
removeAbandoned(ac);
}
}
/**
* Tries to ensure that {@link #getMinIdle()} idle instances are available
* in the pool.
*
* @throws Exception If the associated factory throws an exception
* @since 2.4
*/
public void preparePool() throws Exception {
if (getMinIdle() < 1) {
return;
}
ensureMinIdle();
}
/**
* Attempts to create a new wrapped pooled object.
*
* If there are {@link #getMaxTotal()} objects already in circulation
* or in process of being created, this method returns null.
*
*
* @return The new wrapped pooled object
*
* @throws Exception if the object factory's {@code makeObject} fails
*/
private PooledObject create() throws Exception {
int localMaxTotal = getMaxTotal();
// This simplifies the code later in this method
if (localMaxTotal < 0) {
localMaxTotal = Integer.MAX_VALUE;
}
final long localStartTimeMillis = System.currentTimeMillis();
final long localMaxWaitTimeMillis = Math.max(getMaxWaitMillis(), 0);
// Flag that indicates if create should:
// - TRUE: call the factory to create an object
// - FALSE: return null
// - null: loop and re-test the condition that determines whether to
// call the factory
Boolean create = null;
while (create == null) {
synchronized (makeObjectCountLock) {
final long newCreateCount = createCount.incrementAndGet();
if (newCreateCount > localMaxTotal) {
// The pool is currently at capacity or in the process of
// making enough new objects to take it to capacity.
createCount.decrementAndGet();
if (makeObjectCount == 0) {
// There are no makeObject() calls in progress so the
// pool is at capacity. Do not attempt to create a new
// object. Return and wait for an object to be returned
create = Boolean.FALSE;
} else {
// There are makeObject() calls in progress that might
// bring the pool to capacity. Those calls might also
// fail so wait until they complete and then re-test if
// the pool is at capacity or not.
makeObjectCountLock.wait(localMaxWaitTimeMillis);
}
} else {
// The pool is not at capacity. Create a new object.
makeObjectCount++;
create = Boolean.TRUE;
}
}
// Do not block more if maxWaitTimeMillis is set.
if (create == null &&
(localMaxWaitTimeMillis > 0 &&
System.currentTimeMillis() - localStartTimeMillis >= localMaxWaitTimeMillis)) {
create = Boolean.FALSE;
}
}
if (!create.booleanValue()) {
return null;
}
final PooledObject p;
try {
p = factory.makeObject();
if (getTestOnCreate() && !factory.validateObject(p)) {
createCount.decrementAndGet();
return null;
}
} catch (final Throwable e) {
createCount.decrementAndGet();
throw e;
} finally {
synchronized (makeObjectCountLock) {
makeObjectCount--;
makeObjectCountLock.notifyAll();
}
}
final AbandonedConfig ac = this.abandonedConfig;
if (ac != null && ac.getLogAbandoned()) {
p.setLogAbandoned(true);
p.setRequireFullStackTrace(ac.getRequireFullStackTrace());
}
createdCount.incrementAndGet();
allObjects.put(new IdentityWrapper<>(p.getObject()), p);
return p;
}
/**
* Destroys a wrapped pooled object.
*
* @param toDestroy The wrapped pooled object to destroy
* @param mode DestroyMode context provided to the factory
*
* @throws Exception If the factory fails to destroy the pooled object
* cleanly
*/
private void destroy(final PooledObject toDestroy, final DestroyMode mode) throws Exception {
toDestroy.invalidate();
idleObjects.remove(toDestroy);
allObjects.remove(new IdentityWrapper<>(toDestroy.getObject()));
try {
factory.destroyObject(toDestroy, mode);
} finally {
destroyedCount.incrementAndGet();
createCount.decrementAndGet();
}
}
@Override
void ensureMinIdle() throws Exception {
ensureIdle(getMinIdle(), true);
}
/**
* Tries to ensure that {@code idleCount} idle instances exist in the pool.
*
* Creates and adds idle instances until either {@link #getNumIdle()} reaches {@code idleCount}
* or the total number of objects (idle, checked out, or being created) reaches
* {@link #getMaxTotal()}. If {@code always} is false, no instances are created unless
* there are threads waiting to check out instances from the pool.
*
*
* @param idleCount the number of idle instances desired
* @param always true means create instances even if the pool has no threads waiting
* @throws Exception if the factory's makeObject throws
*/
private void ensureIdle(final int idleCount, final boolean always) throws Exception {
if (idleCount < 1 || isClosed() || (!always && !idleObjects.hasTakeWaiters())) {
return;
}
while (idleObjects.size() < idleCount) {
final PooledObject p = create();
if (p == null) {
// Can't create objects, no reason to think another call to
// create will work. Give up.
break;
}
if (getLifo()) {
idleObjects.addFirst(p);
} else {
idleObjects.addLast(p);
}
}
if (isClosed()) {
// Pool closed while object was being added to idle objects.
// Make sure the returned object is destroyed rather than left
// in the idle object pool (which would effectively be a leak)
clear();
}
}
/**
* Creates an object, and place it into the pool. addObject() is useful for
* "pre-loading" a pool with idle objects.
*
* If there is no capacity available to add to the pool, this is a no-op
* (no exception, no impact to the pool).
*/
@Override
public void addObject() throws Exception {
assertOpen();
if (factory == null) {
throw new IllegalStateException(
"Cannot add objects without a factory.");
}
final PooledObject p = create();
addIdleObject(p);
}
/**
* Adds the provided wrapped pooled object to the set of idle objects for
* this pool. The object must already be part of the pool. If {@code p}
* is null, this is a no-op (no exception, but no impact on the pool).
*
* @param p The object to make idle
*
* @throws Exception If the factory fails to passivate the object
*/
private void addIdleObject(final PooledObject p) throws Exception {
if (p != null) {
factory.passivateObject(p);
if (getLifo()) {
idleObjects.addFirst(p);
} else {
idleObjects.addLast(p);
}
}
}
/**
* Calculates the number of objects to test in a run of the idle object
* evictor.
*
* @return The number of objects to test for validity
*/
private int getNumTests() {
final int numTestsPerEvictionRun = getNumTestsPerEvictionRun();
if (numTestsPerEvictionRun >= 0) {
return Math.min(numTestsPerEvictionRun, idleObjects.size());
}
return (int) (Math.ceil(idleObjects.size() /
Math.abs((double) numTestsPerEvictionRun)));
}
/**
* Recovers abandoned objects which have been checked out but
* not used since longer than the removeAbandonedTimeout.
*
* @param abandonedConfig The configuration to use to identify abandoned objects
*/
@SuppressWarnings("resource") // PrintWriter is managed elsewhere
private void removeAbandoned(final AbandonedConfig abandonedConfig) {
// Generate a list of abandoned objects to remove
final long now = System.currentTimeMillis();
final long timeout =
now - (abandonedConfig.getRemoveAbandonedTimeout() * 1000L);
final ArrayList> remove = new ArrayList<>();
final Iterator> it = allObjects.values().iterator();
while (it.hasNext()) {
final PooledObject pooledObject = it.next();
synchronized (pooledObject) {
if (pooledObject.getState() == PooledObjectState.ALLOCATED &&
pooledObject.getLastUsedTime() <= timeout) {
pooledObject.markAbandoned();
remove.add(pooledObject);
}
}
}
// Now remove the abandoned objects
final Iterator> itr = remove.iterator();
while (itr.hasNext()) {
final PooledObject pooledObject = itr.next();
if (abandonedConfig.getLogAbandoned()) {
pooledObject.printStackTrace(abandonedConfig.getLogWriter());
}
try {
invalidateObject(pooledObject.getObject(), DestroyMode.ABANDONED);
} catch (final Exception e) {
e.printStackTrace();
}
}
}
//--- Usage tracking support -----------------------------------------------
@Override
public void use(final T pooledObject) {
final AbandonedConfig abandonedCfg = this.abandonedConfig;
if (abandonedCfg != null && abandonedCfg.getUseUsageTracking()) {
final PooledObject wrapper = allObjects.get(new IdentityWrapper<>(pooledObject));
wrapper.use();
}
}
//--- JMX support ----------------------------------------------------------
private volatile String factoryType = null;
/**
* Returns an estimate of the number of threads currently blocked waiting for
* an object from the pool. This is intended for monitoring only, not for
* synchronization control.
*
* @return The estimate of the number of threads currently blocked waiting
* for an object from the pool
*/
@Override
public int getNumWaiters() {
if (getBlockWhenExhausted()) {
return idleObjects.getTakeQueueLength();
}
return 0;
}
/**
* Returns the type - including the specific type rather than the generic -
* of the factory.
*
* @return A string representation of the factory type
*/
@Override
public String getFactoryType() {
// Not thread safe. Accept that there may be multiple evaluations.
if (factoryType == null) {
final StringBuilder result = new StringBuilder();
result.append(factory.getClass().getName());
result.append('<');
final Class pooledObjectType =
PoolImplUtils.getFactoryType(factory.getClass());
result.append(pooledObjectType.getName());
result.append('>');
factoryType = result.toString();
}
return factoryType;
}
/**
* Provides information on all the objects in the pool, both idle (waiting
* to be borrowed) and active (currently borrowed).
*
* Note: This is named listAllObjects so it is presented as an operation via
* JMX. That means it won't be invoked unless the explicitly requested
* whereas all attributes will be automatically requested when viewing the
* attributes for an object in a tool like JConsole.
*
*
* @return Information grouped on all the objects in the pool
*/
@Override
public Set listAllObjects() {
final Set result =
new HashSet<>(allObjects.size());
for (final PooledObject p : allObjects.values()) {
result.add(new DefaultPooledObjectInfo(p));
}
return result;
}
// --- configuration attributes --------------------------------------------
private volatile int maxIdle = GenericObjectPoolConfig.DEFAULT_MAX_IDLE;
private volatile int minIdle = GenericObjectPoolConfig.DEFAULT_MIN_IDLE;
private final PooledObjectFactory factory;
// --- internal attributes -------------------------------------------------
/*
* All of the objects currently associated with this pool in any state. It
* excludes objects that have been destroyed. The size of
* {@link #allObjects} will always be less than or equal to {@link
* #_maxActive}. Map keys are pooled objects, values are the PooledObject
* wrappers used internally by the pool.
*/
private final Map, PooledObject> allObjects =
new ConcurrentHashMap<>();
/*
* The combined count of the currently created objects and those in the
* process of being created. Under load, it may exceed {@link #_maxActive}
* if multiple threads try and create a new object at the same time but
* {@link #create()} will ensure that there are never more than
* {@link #_maxActive} objects created at any one time.
*/
private final AtomicLong createCount = new AtomicLong(0);
private long makeObjectCount = 0;
private final Object makeObjectCountLock = new Object();
private final LinkedBlockingDeque> idleObjects;
// JMX specific attributes
private static final String ONAME_BASE =
"org.apache.commons.pool2:type=GenericObjectPool,name=";
// Additional configuration properties for abandoned object tracking
private volatile AbandonedConfig abandonedConfig = null;
@Override
protected void toStringAppendFields(final StringBuilder builder) {
super.toStringAppendFields(builder);
builder.append(", factoryType=");
builder.append(factoryType);
builder.append(", maxIdle=");
builder.append(maxIdle);
builder.append(", minIdle=");
builder.append(minIdle);
builder.append(", factory=");
builder.append(factory);
builder.append(", allObjects=");
builder.append(allObjects);
builder.append(", createCount=");
builder.append(createCount);
builder.append(", idleObjects=");
builder.append(idleObjects);
builder.append(", abandonedConfig=");
builder.append(abandonedConfig);
}
}