    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.pool2.impl;
    018
    019import java.time.Duration;
    020import java.util.ArrayList;
    021import java.util.Deque;
    022import java.util.HashMap;
    023import java.util.Iterator;
    024import java.util.List;
    025import java.util.Map;
    026import java.util.Map.Entry;
    027import java.util.NoSuchElementException;
    028import java.util.Objects;
    029import java.util.TreeMap;
    030import java.util.concurrent.ConcurrentHashMap;
    031import java.util.concurrent.TimeUnit;
    032import java.util.concurrent.atomic.AtomicInteger;
    033import java.util.concurrent.atomic.AtomicLong;
    034import java.util.concurrent.locks.Lock;
    035import java.util.concurrent.locks.ReadWriteLock;
    036import java.util.concurrent.locks.ReentrantReadWriteLock;
    037import java.util.stream.Collectors;
    038
    039import org.apache.commons.pool2.DestroyMode;
    040import org.apache.commons.pool2.KeyedObjectPool;
    041import org.apache.commons.pool2.KeyedPooledObjectFactory;
    042import org.apache.commons.pool2.PoolUtils;
    043import org.apache.commons.pool2.PooledObject;
    044import org.apache.commons.pool2.PooledObjectState;
    045import org.apache.commons.pool2.SwallowedExceptionListener;
    046import org.apache.commons.pool2.UsageTracking;
    047
    048/**
    049 * A configurable {@code KeyedObjectPool} implementation.
    050 * <p>
    051 * When coupled with the appropriate {@link KeyedPooledObjectFactory},
    052 * {@code GenericKeyedObjectPool} provides robust pooling functionality for
    053 * keyed objects. A {@code GenericKeyedObjectPool} can be viewed as a map
    054 * of sub-pools, keyed on the (unique) key values provided to the
    055 * {@link #preparePool preparePool}, {@link #addObject addObject} or
    056 * {@link #borrowObject borrowObject} methods. Each time a new key value is
    057 * provided to one of these methods, a sub-new pool is created under the given
    058 * key to be managed by the containing {@code GenericKeyedObjectPool.}
    059 * </p>
    060 * <p>
    061 * Note that the current implementation uses a ConcurrentHashMap which uses
    062 * equals() to compare keys.
    063 * This means that distinct instance keys must be distinguishable using equals.
    064 * </p>
    065 * <p>
    066 * Optionally, one may configure the pool to examine and possibly evict objects
    067 * as they sit idle in the pool and to ensure that a minimum number of idle
    068 * objects is maintained for each key. This is performed by an "idle object
    069 * eviction" thread, which runs asynchronously. Caution should be used when
    070 * configuring this optional feature. Eviction runs contend with client threads
    071 * for access to objects in the pool, so if they run too frequently performance
    072 * issues may result.
    073 * </p>
    074 * <p>
    075 * Implementation note: To prevent possible deadlocks, care has been taken to
    076 * ensure that no call to a factory method will occur within a synchronization
    077 * block. See POOL-125 and DBCP-44 for more information.
    078 * </p>
    079 * <p>
    080 * This class is intended to be thread-safe.
    081 * </p>
    082 *
    083 * @see GenericObjectPool
    084 *
    085 * @param <K> The type of keys maintained by this pool.
    086 * @param <T> Type of element pooled in this pool.
    087 *
    088 * @since 2.0
    089 */
    090public class GenericKeyedObjectPool<K, T> extends BaseGenericObjectPool<T>
    091        implements KeyedObjectPool<K, T>, GenericKeyedObjectPoolMXBean<K>, UsageTracking<T> {
    092
    093    private static final Integer ZERO = Integer.valueOf(0);
    094
    095    /**
    096     * Maintains information on the per key queue for a given key.
    097     *
    098     * @param <S> type of objects in the pool
    099     */
    100    private class ObjectDeque<S> {
    101
    102        private final LinkedBlockingDeque<PooledObject<S>> idleObjects;
    103
    104        /*
    105         * Number of instances created - number destroyed.
    106         * Invariant: createCount <= maxTotalPerKey
    107         */
    108        private final AtomicInteger createCount = new AtomicInteger(0);
    109
    110        private long makeObjectCount;
    111        private final Object makeObjectCountLock = new Object();
    112
    113        /*
    114         * The map is keyed on pooled instances, wrapped to ensure that
    115         * they work properly as keys.
    116         */
    117        private final Map<IdentityWrapper<S>, PooledObject<S>> allObjects =
    118                new ConcurrentHashMap<>();
    119
    120        /*
    121         * Number of threads with registered interest in this key.
    122         * register(K) increments this counter and deRegister(K) decrements it.
    123         * Invariant: empty keyed pool will not be dropped unless numInterested
    124         *            is 0.
    125         */
    126        private final AtomicLong numInterested = new AtomicLong();
    127
    128        /**
    129         * Constructs a new ObjecDeque with the given fairness policy.
    130         * @param fairness true means client threads waiting to borrow / return instances
    131         * will be served as if waiting in a FIFO queue.
    132         */
    133        public ObjectDeque(final boolean fairness) {
    134            idleObjects = new LinkedBlockingDeque<>(fairness);
    135        }
    136
    137        /**
    138         * Gets all the objects for the current key.
    139         *
    140         * @return All the objects
    141         */
    142        public Map<IdentityWrapper<S>, PooledObject<S>> getAllObjects() {
    143            return allObjects;
    144        }
    145
    146        /**
    147         * Gets the count of the number of objects created for the current
    148         * key.
    149         *
    150         * @return The number of objects created for this key
    151         */
    152        public AtomicInteger getCreateCount() {
    153            return createCount;
    154        }
    155
    156        /**
    157         * Gets the idle objects for the current key.
    158         *
    159         * @return The idle objects
    160         */
    161        public LinkedBlockingDeque<PooledObject<S>> getIdleObjects() {
    162            return idleObjects;
    163        }
    164
    165        /**
    166         * Gets the number of threads with an interest registered in this key.
    167         *
    168         * @return The number of threads with a registered interest in this key
    169         */
    170        public AtomicLong getNumInterested() {
    171            return numInterested;
    172        }
    173
    174        @Override
    175        public String toString() {
    176            final StringBuilder builder = new StringBuilder();
    177            builder.append("ObjectDeque [idleObjects=");
    178            builder.append(idleObjects);
    179            builder.append(", createCount=");
    180            builder.append(createCount);
    181            builder.append(", allObjects=");
    182            builder.append(allObjects);
    183            builder.append(", numInterested=");
    184            builder.append(numInterested);
    185            builder.append("]");
    186            return builder.toString();
    187        }
    188
    189    }
    190
    191    // JMX specific attributes
    192    private static final String ONAME_BASE =
    193            "org.apache.commons.pool2:type=GenericKeyedObjectPool,name=";
    194
    195    //--- configuration attributes ---------------------------------------------
    196    private volatile int maxIdlePerKey =
    197            GenericKeyedObjectPoolConfig.DEFAULT_MAX_IDLE_PER_KEY;
    198
    199    private volatile int minIdlePerKey =
    200            GenericKeyedObjectPoolConfig.DEFAULT_MIN_IDLE_PER_KEY;
    201
    202
    203    private volatile int maxTotalPerKey =
    204            GenericKeyedObjectPoolConfig.DEFAULT_MAX_TOTAL_PER_KEY;
    205
    206    private final KeyedPooledObjectFactory<K, T> factory;
    207
    208    private final boolean fairness;
    209
    210    /*
    211     * My hash of sub-pools (ObjectQueue). The list of keys <b>must</b> be kept
    212     * in step with {@link #poolKeyList} using {@link #keyLock} to ensure any
    213     * changes to the list of current keys is made in a thread-safe manner.
    214     */
    215    private final Map<K, ObjectDeque<T>> poolMap =
    216            new ConcurrentHashMap<>(); // @GuardedBy("keyLock") for write access (and some read access)
    217
    218    /*
    219     * List of pool keys - used to control eviction order. The list of keys
    220     * <b>must</b> be kept in step with {@link #poolMap} using {@link #keyLock}
    221     * to ensure any changes to the list of current keys is made in a
    222     * thread-safe manner.
    223     */
    224    private final List<K> poolKeyList = new ArrayList<>(); // @GuardedBy("keyLock")
    225
    226    private final ReadWriteLock keyLock = new ReentrantReadWriteLock(true);
    227
    228    /*
    229     * The combined count of the currently active objects for all keys and those
    230     * in the process of being created. Under load, it may exceed
    231     * {@link #maxTotal} but there will never be more than {@link #maxTotal}
    232     * created at any one time.
    233     */
    234    private final AtomicInteger numTotal = new AtomicInteger(0);
    235
    236    private Iterator<K> evictionKeyIterator; // @GuardedBy("evictionLock")
    237
    238
    239    private K evictionKey; // @GuardedBy("evictionLock")
    240
    241    /**
    242     * Constructs a new {@code GenericKeyedObjectPool} using defaults from
    243     * {@link GenericKeyedObjectPoolConfig}.
    244     * @param factory the factory to be used to create entries
    245     */
    246    public GenericKeyedObjectPool(final KeyedPooledObjectFactory<K, T> factory) {
    247        this(factory, new GenericKeyedObjectPoolConfig<>());
    248    }
    249
    250    /**
    251     * Constructs a new {@code GenericKeyedObjectPool} using a specific
    252     * configuration.
    253     *
    254     * @param factory the factory to be used to create entries
    255     * @param config    The configuration to use for this pool instance. The
    256     *                  configuration is used by value. Subsequent changes to
    257     *                  the configuration object will not be reflected in the
    258     *                  pool.
    259     */
    260    public GenericKeyedObjectPool(final KeyedPooledObjectFactory<K, T> factory,
    261            final GenericKeyedObjectPoolConfig<T> config) {
    262
    263        super(config, ONAME_BASE, config.getJmxNamePrefix());
    264
    265        if (factory == null) {
    266            jmxUnregister(); // tidy up
    267            throw new IllegalArgumentException("Factory may not be null");
    268        }
    269        this.factory = factory;
    270        this.fairness = config.getFairness();
    271
    272        setConfig(config);
    273    }
    274
    275    /**
    276     * Creates a new {@code GenericKeyedObjectPool} that tracks and destroys
    277     * objects that are checked out, but never returned to the pool.
    278     *
    279     * @param factory   The object factory to be used to create object instances
    280     *                  used by this pool
    281     * @param config    The base pool configuration to use for this pool instance.
    282     *                  The configuration is used by value. Subsequent changes to
    283     *                  the configuration object will not be reflected in the
    284     *                  pool.
    285     * @param abandonedConfig  Configuration for abandoned object identification
    286     *                         and removal.  The configuration is used by value.
    287     * @since 2.10.0
    288     */
    289    public GenericKeyedObjectPool(final KeyedPooledObjectFactory<K, T> factory,
    290            final GenericKeyedObjectPoolConfig<T> config, final AbandonedConfig abandonedConfig) {
    291        this(factory, config);
    292        setAbandonedConfig(abandonedConfig);
    293    }
    294
    295    /**
    296     * Add an object to the set of idle objects for a given key.
    297     *
    298     * @param key The key to associate with the idle object
    299     * @param p The wrapped object to add.
    300     *
    301     * @throws Exception If the associated factory fails to passivate the object
    302     */
    303    private void addIdleObject(final K key, final PooledObject<T> p) throws Exception {
    304
    305        if (p != null) {
    306            factory.passivateObject(key, p);
    307            final LinkedBlockingDeque<PooledObject<T>> idleObjects =
    308                    poolMap.get(key).getIdleObjects();
    309            if (getLifo()) {
    310                idleObjects.addFirst(p);
    311            } else {
    312                idleObjects.addLast(p);
    313            }
    314        }
    315    }
    316
    317
    318    /**
    319     * Create an object using the {@link KeyedPooledObjectFactory#makeObject
    320     * factory}, passivate it, and then place it in the idle object pool.
    321     * {@code addObject} is useful for "pre-loading" a pool with idle
    322     * objects.
    323     *
    324     * @param key the key a new instance should be added to
    325     *
    326     * @throws Exception when {@link KeyedPooledObjectFactory#makeObject}
    327     *                   fails.
    328     */
    329    @Override
    330    public void addObject(final K key) throws Exception {
    331        assertOpen();
    332        register(key);
    333        try {
    334            final PooledObject<T> p = create(key);
    335            addIdleObject(key, p);
    336        } finally {
    337            deregister(key);
    338        }
    339    }
    340
    341
    342    /**
    343     * Equivalent to <code>{@link #borrowObject(Object, long) borrowObject}(key,
    344     * {@link #getMaxWaitDuration()})</code>.
    345     *
    346     * {@inheritDoc}
    347     */
    348    @Override
    349    public T borrowObject(final K key) throws Exception {
    350        return borrowObject(key, getMaxWaitDuration().toMillis());
    351    }
    352
    353
    354    /**
    355     * Borrows an object from the sub-pool associated with the given key using
    356     * the specified waiting time which only applies if
    357     * {@link #getBlockWhenExhausted()} is true.
    358     * <p>
    359     * If there is one or more idle instances available in the sub-pool
    360     * associated with the given key, then an idle instance will be selected
    361     * based on the value of {@link #getLifo()}, activated and returned.  If
    362     * activation fails, or {@link #getTestOnBorrow() testOnBorrow} is set to
    363     * {@code true} and validation fails, the instance is destroyed and the
    364     * next available instance is examined.  This continues until either a valid
    365     * instance is returned or there are no more idle instances available.
    366     * </p>
    367     * <p>
    368     * If there are no idle instances available in the sub-pool associated with
    369     * the given key, behavior depends on the {@link #getMaxTotalPerKey()
    370     * maxTotalPerKey}, {@link #getMaxTotal() maxTotal}, and (if applicable)
    371     * {@link #getBlockWhenExhausted()} and the value passed in to the
    372     * {@code borrowMaxWaitMillis} parameter. If the number of instances checked
    373     * out from the sub-pool under the given key is less than
    374     * {@code maxTotalPerKey} and the total number of instances in
    375     * circulation (under all keys) is less than {@code maxTotal}, a new
    376     * instance is created, activated and (if applicable) validated and returned
    377     * to the caller. If validation fails, a {@code NoSuchElementException}
    378     * will be thrown.
    379     * </p>
    380     * <p>
    381     * If the associated sub-pool is exhausted (no available idle instances and
    382     * no capacity to create new ones), this method will either block
    383     * ({@link #getBlockWhenExhausted()} is true) or throw a
    384     * {@code NoSuchElementException}
    385     * ({@link #getBlockWhenExhausted()} is false).
    386     * The length of time that this method will block when
    387     * {@link #getBlockWhenExhausted()} is true is determined by the value
    388     * passed in to the {@code borrowMaxWait} parameter.
    389     * </p>
    390     * <p>
    391     * When {@code maxTotal} is set to a positive value and this method is
    392     * invoked when at the limit with no idle instances available under the requested
    393     * key, an attempt is made to create room by clearing the oldest 15% of the
    394     * elements from the keyed sub-pools.
    395     * </p>
    396     * <p>
    397     * When the pool is exhausted, multiple calling threads may be
    398     * simultaneously blocked waiting for instances to become available. A
    399     * "fairness" algorithm has been implemented to ensure that threads receive
    400     * available instances in request arrival order.
    401     * </p>
    402     *
    403     * @param key pool key
    404     * @param borrowMaxWaitMillis The time to wait in milliseconds for an object
    405     *                            to become available
    406     *
    407     * @return object instance from the keyed pool
    408     *
    409     * @throws NoSuchElementException if a keyed object instance cannot be
    410     *                                returned because the pool is exhausted.
    411     *
    412     * @throws Exception if a keyed object instance cannot be returned due to an
    413     *                   error
    414     */
    415    public T borrowObject(final K key, final long borrowMaxWaitMillis) throws Exception {
    416        assertOpen();
    417
    418        final AbandonedConfig ac = this.abandonedConfig;
    419        if (ac != null && ac.getRemoveAbandonedOnBorrow() && (getNumIdle() < 2) &&
    420                (getNumActive() > getMaxTotal() - 3)) {
    421            removeAbandoned(ac);
    422        }
    423
    424        PooledObject<T> p = null;
    425
    426        // Get local copy of current config so it is consistent for entire
    427        // method execution
    428        final boolean blockWhenExhausted = getBlockWhenExhausted();
    429
    430        boolean create;
    431        final long waitTimeMillis = System.currentTimeMillis();
    432        final ObjectDeque<T> objectDeque = register(key);
    433
    434        try {
    435            while (p == null) {
    436                create = false;
    437                p = objectDeque.getIdleObjects().pollFirst();
    438                if (p == null) {
    439                    p = create(key);
    440                    if (p != null) {
    441                        create = true;
    442                    }
    443                }
    444                if (blockWhenExhausted) {
    445                    if (p == null) {
    446                        if (borrowMaxWaitMillis < 0) {
    447                            p = objectDeque.getIdleObjects().takeFirst();
    448                        } else {
    449                            p = objectDeque.getIdleObjects().pollFirst(borrowMaxWaitMillis, TimeUnit.MILLISECONDS);
    450                        }
    451                    }
    452                    if (p == null) {
    453                        throw new NoSuchElementException(appendStats(
    454                                "Timeout waiting for idle object, borrowMaxWaitMillis=" + borrowMaxWaitMillis));
    455                    }
    456                } else if (p == null) {
    457                    throw new NoSuchElementException(appendStats("Pool exhausted"));
    458                }
    459                if (!p.allocate()) {
    460                    p = null;
    461                }
    462
    463                if (p != null) {
    464                    try {
    465                        factory.activateObject(key, p);
    466                    } catch (final Exception e) {
    467                        try {
    468                            destroy(key, p, true, DestroyMode.NORMAL);
    469                        } catch (final Exception e1) {
    470                            // Ignore - activation failure is more important
    471                        }
    472                        p = null;
    473                        if (create) {
    474                            final NoSuchElementException nsee = new NoSuchElementException(appendStats("Unable to activate object"));
    475                            nsee.initCause(e);
    476                            throw nsee;
    477                        }
    478                    }
    479                    if (p != null && getTestOnBorrow()) {
    480                        boolean validate = false;
    481                        Throwable validationThrowable = null;
    482                        try {
    483                            validate = factory.validateObject(key, p);
    484                        } catch (final Throwable t) {
    485                            PoolUtils.checkRethrow(t);
    486                            validationThrowable = t;
    487                        }
    488                        if (!validate) {
    489                            try {
    490                                destroy(key, p, true, DestroyMode.NORMAL);
    491                                destroyedByBorrowValidationCount.incrementAndGet();
    492                            } catch (final Exception e) {
    493                                // Ignore - validation failure is more important
    494                            }
    495                            p = null;
    496                            if (create) {
    497                                final NoSuchElementException nsee = new NoSuchElementException(
    498                                        appendStats("Unable to validate object"));
    499                                nsee.initCause(validationThrowable);
    500                                throw nsee;
    501                            }
    502                        }
    503                    }
    504                }
    505            }
    506        } finally {
    507            deregister(key);
    508        }
    509
    510        updateStatsBorrow(p, Duration.ofMillis(System.currentTimeMillis() - waitTimeMillis));
    511
    512        return p.getObject();
    513    }
    514
    515    @Override
    516    String getStatsString() {
    517        // Simply listed in AB order.
    518        return super.getStatsString() +
    519                String.format(", fairness=%s, maxIdlePerKey%,d, maxTotalPerKey=%,d, minIdlePerKey=%,d, numTotal=%,d",
    520                        fairness, maxIdlePerKey, maxTotalPerKey, minIdlePerKey, numTotal.get());
    521    }
    522
    523    /**
    524     * Calculate the number of objects that need to be created to attempt to
    525     * maintain the minimum number of idle objects while not exceeded the limits
    526     * on the maximum number of objects either per key or totally.
    527     *
    528     * @param objectDeque   The set of objects to check
    529     *
    530     * @return The number of new objects to create
    531     */
    532    private int calculateDeficit(final ObjectDeque<T> objectDeque) {
    533
    534        if (objectDeque == null) {
    535            return getMinIdlePerKey();
    536        }
    537
    538        // Used more than once so keep a local copy so the value is consistent
    539        final int maxTotal = getMaxTotal();
    540        final int maxTotalPerKeySave = getMaxTotalPerKey();
    541
    542        // Calculate no of objects needed to be created, in order to have
    543        // the number of pooled objects < maxTotalPerKey();
    544        int objectDefecit = getMinIdlePerKey() - objectDeque.getIdleObjects().size();
    545        if (maxTotalPerKeySave > 0) {
    546            final int growLimit = Math.max(0,
    547                    maxTotalPerKeySave - objectDeque.getIdleObjects().size());
    548            objectDefecit = Math.min(objectDefecit, growLimit);
    549        }
    550
    551        // Take the maxTotal limit into account
    552        if (maxTotal > 0) {
    553            final int growLimit = Math.max(0, maxTotal - getNumActive() - getNumIdle());
    554            objectDefecit = Math.min(objectDefecit, growLimit);
    555        }
    556
    557        return objectDefecit;
    558    }
    559
    560
    561    /**
    562     * Clears any objects sitting idle in the pool by removing them from the
    563     * idle instance sub-pools and then invoking the configured
    564     * PoolableObjectFactory's
    565     * {@link KeyedPooledObjectFactory#destroyObject(Object, PooledObject)}
    566     * method on each idle instance.
    567     * <p>
    568     * Implementation notes:
    569     * </p>
    570     * <ul>
    571     * <li>This method does not destroy or effect in any way instances that are
    572     * checked out when it is invoked.</li>
    573     * <li>Invoking this method does not prevent objects being returned to the
    574     * idle instance pool, even during its execution. Additional instances may
    575     * be returned while removed items are being destroyed.</li>
    576     * <li>Exceptions encountered destroying idle instances are swallowed
    577     * but notified via a {@link SwallowedExceptionListener}.</li>
    578     * </ul>
    579     */
    580    @Override
    581    public void clear() {
    582        poolMap.keySet().forEach(this::clear);
    583    }
    584
    585
    586    /**
    587     * Clears the specified sub-pool, removing all pooled instances
    588     * corresponding to the given {@code key}. Exceptions encountered
    589     * destroying idle instances are swallowed but notified via a
    590     * {@link SwallowedExceptionListener}.
    591     *
    592     * @param key the key to clear
    593     */
    594    @Override
    595    public void clear(final K key) {
    596
    597        final ObjectDeque<T> objectDeque = register(key);
    598
    599        try {
    600            final LinkedBlockingDeque<PooledObject<T>> idleObjects =
    601                    objectDeque.getIdleObjects();
    602
    603            PooledObject<T> p = idleObjects.poll();
    604
    605            while (p != null) {
    606                try {
    607                    destroy(key, p, true, DestroyMode.NORMAL);
    608                } catch (final Exception e) {
    609                    swallowException(e);
    610                }
    611                p = idleObjects.poll();
    612            }
    613        } finally {
    614            deregister(key);
    615        }
    616    }
    617
    618
    619    /**
    620     * Clears oldest 15% of objects in pool.  The method sorts the objects into
    621     * a TreeMap and then iterates the first 15% for removal.
    622     */
    623    public void clearOldest() {
    624
    625        // build sorted map of idle objects
    626        final Map<PooledObject<T>, K> map = new TreeMap<>();
    627
    628        poolMap.forEach((key, value) -> {
    629            // Protect against possible NPE if key has been removed in another
    630            // thread. Not worth locking the keys while this loop completes.
    631            if (value != null) {
    632                // Each item into the map using the PooledObject object as the
    633                // key. It then gets sorted based on the idle time
    634                value.getIdleObjects().forEach(p -> map.put(p, key));
    635            }
    636        });
    637
    638        // Now iterate created map and kill the first 15% plus one to account
    639        // for zero
    640        int itemsToRemove = ((int) (map.size() * 0.15)) + 1;
    641        final Iterator<Entry<PooledObject<T>, K>> iter = map.entrySet().iterator();
    642
    643        while (iter.hasNext() && itemsToRemove > 0) {
    644            final Entry<PooledObject<T>, K> entry = iter.next();
    645            // kind of backwards on naming.  In the map, each key is the
    646            // PooledObject because it has the ordering with the timestamp
    647            // value.  Each value that the key references is the key of the
    648            // list it belongs to.
    649            final K key = entry.getValue();
    650            final PooledObject<T> p = entry.getKey();
    651            // Assume the destruction succeeds
    652            boolean destroyed = true;
    653            try {
    654                destroyed = destroy(key, p, false, DestroyMode.NORMAL);
    655            } catch (final Exception e) {
    656                swallowException(e);
    657            }
    658            if (destroyed) {
    659                itemsToRemove--;
    660            }
    661        }
    662    }
    663
    664
    665    /**
    666     * Closes the keyed object pool. Once the pool is closed,
    667     * {@link #borrowObject(Object)} will fail with IllegalStateException, but
    668     * {@link #returnObject(Object, Object)} and
    669     * {@link #invalidateObject(Object, Object)} will continue to work, with
    670     * returned objects destroyed on return.
    671     * <p>
    672     * Destroys idle instances in the pool by invoking {@link #clear()}.
    673     * </p>
    674     */
    675    @Override
    676    public void close() {
    677        if (isClosed()) {
    678            return;
    679        }
    680
    681        synchronized (closeLock) {
    682            if (isClosed()) {
    683                return;
    684            }
    685
    686            // Stop the evictor before the pool is closed since evict() calls
    687            // assertOpen()
    688            stopEvictor();
    689
    690            closed = true;
    691            // This clear removes any idle objects
    692            clear();
    693
    694            jmxUnregister();
    695
    696            // Release any threads that were waiting for an object
    697            poolMap.values().forEach(e -> e.getIdleObjects().interuptTakeWaiters());
    698            // This clear cleans up the keys now any waiting threads have been
    699            // interrupted
    700            clear();
    701        }
    702    }
    703
    704    /**
    705     * Creates a new pooled object.
    706     *
    707     * @param key Key associated with new pooled object
    708     *
    709     * @return The new, wrapped pooled object
    710     *
    711     * @throws Exception If the objection creation fails
    712     */
    713    private PooledObject<T> create(final K key) throws Exception {
    714        int maxTotalPerKeySave = getMaxTotalPerKey(); // Per key
    715        if (maxTotalPerKeySave < 0) {
    716            maxTotalPerKeySave = Integer.MAX_VALUE;
    717        }
    718        final int maxTotal = getMaxTotal();   // All keys
    719
    720        final ObjectDeque<T> objectDeque = poolMap.get(key);
    721
    722        // Check against the overall limit
    723        boolean loop = true;
    724
    725        while (loop) {
    726            final int newNumTotal = numTotal.incrementAndGet();
    727            if (maxTotal > -1 && newNumTotal > maxTotal) {
    728                numTotal.decrementAndGet();
    729                if (getNumIdle() == 0) {
    730                    return null;
    731                }
    732                clearOldest();
    733            } else {
    734                loop = false;
    735            }
    736        }
    737
    738        // Flag that indicates if create should:
    739        // - TRUE:  call the factory to create an object
    740        // - FALSE: return null
    741        // - null:  loop and re-test the condition that determines whether to
    742        //          call the factory
    743        Boolean create = null;
    744        while (create == null) {
    745            synchronized (objectDeque.makeObjectCountLock) {
    746                final long newCreateCount = objectDeque.getCreateCount().incrementAndGet();
    747                // Check against the per key limit
    748                if (newCreateCount > maxTotalPerKeySave) {
    749                    // The key is currently at capacity or in the process of
    750                    // making enough new objects to take it to capacity.
    751                    objectDeque.getCreateCount().decrementAndGet();
    752                    if (objectDeque.makeObjectCount == 0) {
    753                        // There are no makeObject() calls in progress for this
    754                        // key so the key is at capacity. Do not attempt to
    755                        // create a new object. Return and wait for an object to
    756                        // be returned.
    757                        create = Boolean.FALSE;
    758                    } else {
    759                        // There are makeObject() calls in progress that might
    760                        // bring the pool to capacity. Those calls might also
    761                        // fail so wait until they complete and then re-test if
    762                        // the pool is at capacity or not.
    763                        objectDeque.makeObjectCountLock.wait();
    764                    }
    765                } else {
    766                    // The pool is not at capacity. Create a new object.
    767                    objectDeque.makeObjectCount++;
    768                    create = Boolean.TRUE;
    769                }
    770            }
    771        }
    772
    773        if (!create.booleanValue()) {
    774            numTotal.decrementAndGet();
    775            return null;
    776        }
    777
    778        PooledObject<T> p = null;
    779        try {
    780            p = factory.makeObject(key);
    781            if (getTestOnCreate() && !factory.validateObject(key, p)) {
    782                numTotal.decrementAndGet();
    783                objectDeque.getCreateCount().decrementAndGet();
    784                return null;
    785            }
    786        } catch (final Exception e) {
    787            numTotal.decrementAndGet();
    788            objectDeque.getCreateCount().decrementAndGet();
    789            throw e;
    790        } finally {
    791            synchronized (objectDeque.makeObjectCountLock) {
    792                objectDeque.makeObjectCount--;
    793                objectDeque.makeObjectCountLock.notifyAll();
    794            }
    795        }
    796
    797        final AbandonedConfig ac = this.abandonedConfig;
    798        if (ac != null && ac.getLogAbandoned()) {
    799            p.setLogAbandoned(true);
    800            p.setRequireFullStackTrace(ac.getRequireFullStackTrace());
    801        }
    802
    803        createdCount.incrementAndGet();
    804        objectDeque.getAllObjects().put(new IdentityWrapper<>(p.getObject()), p);
    805        return p;
    806    }
    807
    808    /**
    809     * De-register the use of a key by an object.
    810     * <p>
    811     * {@link #register(Object)} and {@link #deregister(Object)} must always be used as a pair.
    812     * </p>
    813     *
    814     * @param k The key to de-register
    815     */
    816    private void deregister(final K k) {
    817        Lock lock = keyLock.readLock();
    818        try {
    819            lock.lock();
    820            final ObjectDeque<T> objectDeque = poolMap.get(k);
    821            final long numInterested = objectDeque.getNumInterested().decrementAndGet();
    822            if (numInterested == 0 && objectDeque.getCreateCount().get() == 0) {
    823                // Potential to remove key
    824                // Upgrade to write lock
    825                lock.unlock();
    826                lock = keyLock.writeLock();
    827                lock.lock();
    828                if (objectDeque.getCreateCount().get() == 0 && objectDeque.getNumInterested().get() == 0) {
    829                    // NOTE: Keys must always be removed from both poolMap and
    830                    //       poolKeyList at the same time while protected by
    831                    //       keyLock.writeLock()
    832                    poolMap.remove(k);
    833                    poolKeyList.remove(k);
    834                }
    835            }
    836        } finally {
    837            lock.unlock();
    838        }
    839    }
    840
    841
    842    /**
    843     * Destroy the wrapped, pooled object.
    844     *
    845     * @param key The key associated with the object to destroy.
    846     * @param toDestroy The wrapped object to be destroyed
    847     * @param always Should the object be destroyed even if it is not currently
    848     *               in the set of idle objects for the given key
    849     * @param destroyMode DestroyMode context provided to the factory
    850     *
    851     * @return {@code true} if the object was destroyed, otherwise {@code false}
    852     * @throws Exception If the object destruction failed
    853     */
    854    private boolean destroy(final K key, final PooledObject<T> toDestroy, final boolean always, final DestroyMode destroyMode)
    855            throws Exception {
    856
    857        final ObjectDeque<T> objectDeque = register(key);
    858
    859        try {
    860            boolean isIdle;
    861            synchronized(toDestroy) {
    862                // Check idle state directly
    863                isIdle = toDestroy.getState().equals(PooledObjectState.IDLE);
    864                // If idle, not under eviction test, or always is true, remove instance,
    865                // updating isIdle if instance is found in idle objects
    866                if (isIdle || always) {
    867                    isIdle = objectDeque.getIdleObjects().remove(toDestroy);
    868                }
    869            }
    870            if (isIdle || always) {
    871                objectDeque.getAllObjects().remove(new IdentityWrapper<>(toDestroy.getObject()));
    872                toDestroy.invalidate();
    873
    874                try {
    875                    factory.destroyObject(key, toDestroy, destroyMode);
    876                } finally {
    877                    objectDeque.getCreateCount().decrementAndGet();
    878                    destroyedCount.incrementAndGet();
    879                    numTotal.decrementAndGet();
    880                }
    881                return true;
    882            }
    883            return false;
    884        } finally {
    885            deregister(key);
    886        }
    887    }
    888
    889    @Override
    890    void ensureMinIdle() throws Exception {
    891        final int minIdlePerKeySave = getMinIdlePerKey();
    892        if (minIdlePerKeySave < 1) {
    893            return;
    894        }
    895
    896        for (final K k : poolMap.keySet()) {
    897            ensureMinIdle(k);
    898        }
    899    }
    900
    901    /**
    902     * Ensure that the configured number of minimum idle objects is available in
    903     * the pool for the given key.
    904     *
    905     * @param key The key to check for idle objects
    906     *
    907     * @throws Exception If a new object is required and cannot be created
    908     */
    909    private void ensureMinIdle(final K key) throws Exception {
    910        // Calculate current pool objects
    911        ObjectDeque<T> objectDeque = poolMap.get(key);
    912
    913        // objectDeque == null is OK here. It is handled correctly by both
    914        // methods called below.
    915
    916        // this method isn't synchronized so the
    917        // calculateDeficit is done at the beginning
    918        // as a loop limit and a second time inside the loop
    919        // to stop when another thread already returned the
    920        // needed objects
    921        final int deficit = calculateDeficit(objectDeque);
    922
    923        for (int i = 0; i < deficit && calculateDeficit(objectDeque) > 0; i++) {
    924            addObject(key);
    925            // If objectDeque was null, it won't be any more. Obtain a reference
    926            // to it so the deficit can be correctly calculated. It needs to
    927            // take account of objects created in other threads.
    928            if (objectDeque == null) {
    929                objectDeque = poolMap.get(key);
    930            }
    931        }
    932    }
    933
    934
    935    /**
    936     * {@inheritDoc}
    937     * <p>
    938     * Successive activations of this method examine objects in keyed sub-pools
    939     * in sequence, cycling through the keys and examining objects in
    940     * oldest-to-youngest order within the keyed sub-pools.
    941     * </p>
    942     */
    943    @Override
    944    public void evict() throws Exception {
    945        assertOpen();
    946
    947        if (getNumIdle() > 0) {
    948
    949            PooledObject<T> underTest = null;
    950            final EvictionPolicy<T> evictionPolicy = getEvictionPolicy();
    951
    952            synchronized (evictionLock) {
    953                final EvictionConfig evictionConfig = new EvictionConfig(
    954                        getMinEvictableIdleDuration(),
    955                        getSoftMinEvictableIdleDuration(),
    956                        getMinIdlePerKey());
    957
    958                final boolean testWhileIdle = getTestWhileIdle();
    959
    960                for (int i = 0, m = getNumTests(); i < m; i++) {
    961                    if (evictionIterator == null || !evictionIterator.hasNext()) {
    962                        if (evictionKeyIterator == null ||
    963                                !evictionKeyIterator.hasNext()) {
    964                            final List<K> keyCopy = new ArrayList<>();
    965                            final Lock readLock = keyLock.readLock();
    966                            readLock.lock();
    967                            try {
    968                                keyCopy.addAll(poolKeyList);
    969                            } finally {
    970                                readLock.unlock();
    971                            }
    972                            evictionKeyIterator = keyCopy.iterator();
    973                        }
    974                        while (evictionKeyIterator.hasNext()) {
    975                            evictionKey = evictionKeyIterator.next();
    976                            final ObjectDeque<T> objectDeque = poolMap.get(evictionKey);
    977                            if (objectDeque == null) {
    978                                continue;
    979                            }
    980
    981                            final Deque<PooledObject<T>> idleObjects = objectDeque.getIdleObjects();
    982                            evictionIterator = new EvictionIterator(idleObjects);
    983                            if (evictionIterator.hasNext()) {
    984                                break;
    985                            }
    986                            evictionIterator = null;
    987                        }
    988                    }
    989                    if (evictionIterator == null) {
    990                        // Pools exhausted
    991                        return;
    992                    }
    993                    final Deque<PooledObject<T>> idleObjects;
    994                    try {
    995                        underTest = evictionIterator.next();
    996                        idleObjects = evictionIterator.getIdleObjects();
    997                    } catch (final NoSuchElementException nsee) {
    998                        // Object was borrowed in another thread
    999                        // Don't count this as an eviction test so reduce i;
    1000                        i--;
    1001                        evictionIterator = null;
    1002                        continue;
    1003                    }
    1004
    1005                    if (!underTest.startEvictionTest()) {
    1006                        // Object was borrowed in another thread
    1007                        // Don't count this as an eviction test so reduce i;
    1008                        i--;
    1009                        continue;
    1010                    }
    1011
    1012                    // User provided eviction policy could throw all sorts of
    1013                    // crazy exceptions. Protect against such an exception
    1014                    // killing the eviction thread.
    1015                    boolean evict;
    1016                    try {
    1017                        evict = evictionPolicy.evict(evictionConfig, underTest,
    1018                                poolMap.get(evictionKey).getIdleObjects().size());
    1019                    } catch (final Throwable t) {
    1020                        // Slightly convoluted as SwallowedExceptionListener
    1021                        // uses Exception rather than Throwable
    1022                        PoolUtils.checkRethrow(t);
    1023                        swallowException(new Exception(t));
    1024                        // Don't evict on error conditions
    1025                        evict = false;
    1026                    }
    1027
    1028                    if (evict) {
    1029                        destroy(evictionKey, underTest, true, DestroyMode.NORMAL);
    1030                        destroyedByEvictorCount.incrementAndGet();
    1031                    } else {
    1032                        if (testWhileIdle) {
    1033                            boolean active = false;
    1034                            try {
    1035                                factory.activateObject(evictionKey, underTest);
    1036                                active = true;
    1037                            } catch (final Exception e) {
    1038                                destroy(evictionKey, underTest, true, DestroyMode.NORMAL);
    1039                                destroyedByEvictorCount.incrementAndGet();
    1040                            }
    1041                            if (active) {
    1042                                boolean validate = false;
    1043                                Throwable validationThrowable = null;
    1044                                try {
    1045                                    validate = factory.validateObject(evictionKey, underTest);
    1046                                } catch (final Throwable t) {
    1047                                    PoolUtils.checkRethrow(t);
    1048                                    validationThrowable = t;
    1049                                }
    1050                                if (!validate) {
    1051                                    destroy(evictionKey, underTest, true, DestroyMode.NORMAL);
    1052                                    destroyedByEvictorCount.incrementAndGet();
    1053                                    if (validationThrowable != null) {
    1054                                        if (validationThrowable instanceof RuntimeException) {
    1055                                            throw (RuntimeException) validationThrowable;
    1056                                        }
    1057                                        throw (Error) validationThrowable;
    1058                                    }
    1059                                } else {
    1060                                    try {
    1061                                        factory.passivateObject(evictionKey, underTest);
    1062                                    } catch (final Exception e) {
    1063                                        destroy(evictionKey, underTest, true, DestroyMode.NORMAL);
    1064                                        destroyedByEvictorCount.incrementAndGet();
    1065                                    }
    1066                                }
    1067                            }
    1068                        }
    1069                        if (!underTest.endEvictionTest(idleObjects)) {
    1070                            // TODO - May need to add code here once additional
    1071                            // states are used
    1072                        }
    1073                    }
    1074                }
    1075            }
    1076        }
    1077        final AbandonedConfig ac = this.abandonedConfig;
    1078        if (ac != null && ac.getRemoveAbandonedOnMaintenance()) {
    1079            removeAbandoned(ac);
    1080        }
    1081    }
    1082
    1083    /**
    1084     * Gets a reference to the factory used to create, destroy and validate
    1085     * the objects used by this pool.
    1086     *
    1087     * @return the factory
    1088     */
    1089    public KeyedPooledObjectFactory<K, T> getFactory() {
    1090        return factory;
    1091    }
    1092
    1093    /**
    1094     * Gets the cap on the number of "idle" instances per key in the pool.
    1095     * If maxIdlePerKey is set too low on heavily loaded systems it is possible
    1096     * you will see objects being destroyed and almost immediately new objects
    1097     * being created. This is a result of the active threads momentarily
    1098     * returning objects faster than they are requesting them, causing the
    1099     * number of idle objects to rise above maxIdlePerKey. The best value for
    1100     * maxIdlePerKey for heavily loaded system will vary but the default is a
    1101     * good starting point.
    1102     *
    1103     * @return the maximum number of "idle" instances that can be held in a
    1104     *         given keyed sub-pool or a negative value if there is no limit
    1105     *
    1106     * @see #setMaxIdlePerKey
    1107     */
    1108    @Override
    1109    public int getMaxIdlePerKey() {
    1110        return maxIdlePerKey;
    1111    }
    1112
    1113    /**
    1114     * Gets the limit on the number of object instances allocated by the pool
    1115     * (checked out or idle), per key. When the limit is reached, the sub-pool
    1116     * is said to be exhausted. A negative value indicates no limit.
    1117     *
    1118     * @return the limit on the number of active instances per key
    1119     *
    1120     * @see #setMaxTotalPerKey
    1121     */
    1122    @Override
    1123    public int getMaxTotalPerKey() {
    1124        return maxTotalPerKey;
    1125    }
    1126
    1127    /**
    1128     * Gets the target for the minimum number of idle objects to maintain in
    1129     * each of the keyed sub-pools. This setting only has an effect if it is
    1130     * positive and {@link #getDurationBetweenEvictionRuns()} is greater than
    1131     * zero. If this is the case, an attempt is made to ensure that each
    1132     * sub-pool has the required minimum number of instances during idle object
    1133     * eviction runs.
    1134     * <p>
    1135     * If the configured value of minIdlePerKey is greater than the configured
    1136     * value for maxIdlePerKey then the value of maxIdlePerKey will be used
    1137     * instead.
    1138     * </p>
    1139     *
    1140     * @return minimum size of the each keyed pool
    1141     *
    1142     * @see #setTimeBetweenEvictionRunsMillis
    1143     */
    1144    @Override
    1145    public int getMinIdlePerKey() {
    1146        final int maxIdlePerKeySave = getMaxIdlePerKey();
    1147        return this.minIdlePerKey > maxIdlePerKeySave ? maxIdlePerKeySave : minIdlePerKey;
    1148    }
    1149
    1150    @Override
    1151    public int getNumActive() {
    1152        return numTotal.get() - getNumIdle();
    1153    }
    1154
    1155    @Override
    1156    public int getNumActive(final K key) {
    1157        final ObjectDeque<T> objectDeque = poolMap.get(key);
    1158        if (objectDeque != null) {
    1159            return objectDeque.getAllObjects().size() -
    1160                    objectDeque.getIdleObjects().size();
    1161        }
    1162        return 0;
    1163    }
    1164
    1165    @Override
    1166    public Map<String, Integer> getNumActivePerKey() {
    1167        final HashMap<String, Integer> result = new HashMap<>();
    1168
    1169        poolMap.entrySet().forEach(entry -> {
    1170            if (entry != null) {
    1171                final K key = entry.getKey();
    1172                final ObjectDeque<T> objectDequeue = entry.getValue();
    1173                if (key != null && objectDequeue != null) {
    1174                    result.put(key.toString(), Integer.valueOf(
    1175                            objectDequeue.getAllObjects().size() -
    1176                            objectDequeue.getIdleObjects().size()));
    1177                }
    1178            }
    1179        });
    1180        return result;
    1181    }
    1182
    1183    @Override
    1184    public int getNumIdle() {
    1185        return poolMap.values().stream().mapToInt(e -> e.getIdleObjects().size()).sum();
    1186    }
    1187
    1188
    1189    //--- JMX support ----------------------------------------------------------
    1190
    1191    @Override
    1192    public int getNumIdle(final K key) {
    1193        final ObjectDeque<T> objectDeque = poolMap.get(key);
    1194        return objectDeque != null ? objectDeque.getIdleObjects().size() : 0;
    1195    }
    1196
    1197    /**
    1198     * Calculate the number of objects to test in a run of the idle object
    1199     * evictor.
    1200     *
    1201     * @return The number of objects to test for validity
    1202     */
    1203    private int getNumTests() {
    1204        final int totalIdle = getNumIdle();
    1205        final int numTests = getNumTestsPerEvictionRun();
    1206        if (numTests >= 0) {
    1207            return Math.min(numTests, totalIdle);
    1208        }
    1209        return (int) (Math.ceil(totalIdle / Math.abs((double) numTests)));
    1210    }
    1211
    1212    /**
    1213     * Return an estimate of the number of threads currently blocked waiting for
    1214     * an object from the pool. This is intended for monitoring only, not for
    1215     * synchronization control.
    1216     *
    1217     * @return The estimate of the number of threads currently blocked waiting
    1218     *         for an object from the pool
    1219     */
    1220    @Override
    1221    public int getNumWaiters() {
    1222        if (getBlockWhenExhausted()) {
    1223            // Assume no overflow
    1224            return poolMap.values().stream().mapToInt(e -> e.getIdleObjects().getTakeQueueLength()).sum();
    1225        }
    1226        return 0;
    1227    }
    1228
    1229    /**
    1230     * Return an estimate of the number of threads currently blocked waiting for
    1231     * an object from the pool for each key. This is intended for
    1232     * monitoring only, not for synchronization control.
    1233     *
    1234     * @return The estimate of the number of threads currently blocked waiting
    1235     *         for an object from the pool for each key
    1236     */
    1237    @Override
    1238    public Map<String, Integer> getNumWaitersByKey() {
    1239        final Map<String, Integer> result = new HashMap<>();
    1240
    1241        for (final Entry<K, ObjectDeque<T>> entry : poolMap.entrySet()) {
    1242            final K k = entry.getKey();
    1243            final ObjectDeque<T> deque = entry.getValue();
    1244            if (deque != null) {
    1245                result.put(k.toString(), getBlockWhenExhausted() ? Integer.valueOf(deque.getIdleObjects().getTakeQueueLength()) : ZERO);
    1246            }
    1247        }
    1248        return result;
    1249    }
    1250
    1251    /**
    1252     * Checks to see if there are any threads currently waiting to borrow
    1253     * objects but are blocked waiting for more objects to become available.
    1254     *
    1255     * @return {@code true} if there is at least one thread waiting otherwise
    1256     *         {@code false}
    1257     */
    1258    private boolean hasBorrowWaiters() {
    1259        return poolMap.values().stream().anyMatch(deque -> deque != null && deque.getIdleObjects().hasTakeWaiters());
    1260    }
    1261
    1262    /**
    1263     * {@inheritDoc}
    1264     * <p>
    1265     * Activation of this method decrements the active count associated with
    1266     * the given keyed pool and attempts to destroy {@code obj.}
    1267     * </p>
    1268     *
    1269     * @param key pool key
    1270     * @param obj instance to invalidate
    1271     *
    1272     * @throws Exception             if an exception occurs destroying the
    1273     *                               object
    1274     * @throws IllegalStateException if obj does not belong to the pool
    1275     *                               under the given key
    1276     */
    1277    @Override
    1278    public void invalidateObject(final K key, final T obj) throws Exception {
    1279        invalidateObject(key, obj, DestroyMode.NORMAL);
    1280    }
    1281
    1282    /**
    1283     * {@inheritDoc}
    1284     * <p>
    1285     * Activation of this method decrements the active count associated with
    1286     * the given keyed pool and attempts to destroy {@code obj.}
    1287     * </p>
    1288     *
    1289     * @param key pool key
    1290     * @param obj instance to invalidate
    1291     * @param destroyMode DestroyMode context provided to factory
    1292     *
    1293     * @throws Exception             if an exception occurs destroying the
    1294     *                               object
    1295     * @throws IllegalStateException if obj does not belong to the pool
    1296     *                               under the given key
    1297     * @since 2.9.0
    1298     */
    1299    @Override
    1300    public void invalidateObject(final K key, final T obj, final DestroyMode destroyMode) throws Exception {
    1301        final ObjectDeque<T> objectDeque = poolMap.get(key);
    1302        final PooledObject<T> p = objectDeque.getAllObjects().get(new IdentityWrapper<>(obj));
    1303        if (p == null) {
    1304            throw new IllegalStateException(appendStats("Object not currently part of this pool"));
    1305        }
    1306        synchronized (p) {
    1307            if (p.getState() != PooledObjectState.INVALID) {
    1308                destroy(key, p, true, destroyMode);
    1309            }
    1310        }
    1311        if (objectDeque.idleObjects.hasTakeWaiters()) {
    1312            addObject(key);
    1313        }
    1314    }
    1315
    1316    /**
    1317     * Provides information on all the objects in the pool, both idle (waiting
    1318     * to be borrowed) and active (currently borrowed).
    1319     * <p>
    1320     * Note: This is named listAllObjects so it is presented as an operation via
    1321     * JMX. That means it won't be invoked unless the explicitly requested
    1322     * whereas all attributes will be automatically requested when viewing the
    1323     * attributes for an object in a tool like JConsole.
    1324     * </p>
    1325     *
    1326     * @return Information grouped by key on all the objects in the pool
    1327     */
    1328    @Override
    1329    public Map<String, List<DefaultPooledObjectInfo>> listAllObjects() {
    1330        final Map<String, List<DefaultPooledObjectInfo>> result = new HashMap<>();
    1331
    1332        poolMap.forEach((k, value) -> {
    1333            if (value != null) {
    1334                result.put(k.toString(), value.getAllObjects().values().stream().map(DefaultPooledObjectInfo::new).collect(Collectors.toList()));
    1335            }
    1336        });
    1337        return result;
    1338    }
    1339
    1340    /**
    1341     * Registers a key for pool control and ensures that
    1342     * {@link #getMinIdlePerKey()} idle instances are created.
    1343     *
    1344     * @param key - The key to register for pool control.
    1345     *
    1346     * @throws Exception If the associated factory throws an exception
    1347     */
    1348    public void preparePool(final K key) throws Exception {
    1349        final int minIdlePerKeySave = getMinIdlePerKey();
    1350        if (minIdlePerKeySave < 1) {
    1351            return;
    1352        }
    1353        ensureMinIdle(key);
    1354    }
    1355
    1356    /**
    1357     * Register the use of a key by an object.
    1358     * <p>
    1359     * {@link #register(Object)} and {@link #deregister(Object)} must always be used as a pair.
    1360     * </p>
    1361     *
    1362     * @param k The key to register
    1363     *
    1364     * @return The objects currently associated with the given key. If this
    1365     *         method returns without throwing an exception then it will never
    1366     *         return null.
    1367     */
    1368    private ObjectDeque<T> register(final K k) {
    1369        Lock lock = keyLock.readLock();
    1370        ObjectDeque<T> objectDeque = null;
    1371        try {
    1372            lock.lock();
    1373            objectDeque = poolMap.get(k);
    1374            if (objectDeque == null) {
    1375                // Upgrade to write lock
    1376                lock.unlock();
    1377                lock = keyLock.writeLock();
    1378                lock.lock();
    1379                objectDeque = poolMap.get(k);
    1380                if (objectDeque == null) {
    1381                    objectDeque = new ObjectDeque<>(fairness);
    1382                    objectDeque.getNumInterested().incrementAndGet();
    1383                    // NOTE: Keys must always be added to both poolMap and
    1384                    //       poolKeyList at the same time while protected by
    1385                    //       keyLock.writeLock()
    1386                    poolMap.put(k, objectDeque);
    1387                    poolKeyList.add(k);
    1388                } else {
    1389                    objectDeque.getNumInterested().incrementAndGet();
    1390                }
    1391            } else {
    1392                objectDeque.getNumInterested().incrementAndGet();
    1393            }
    1394        } finally {
    1395            lock.unlock();
    1396        }
    1397        return objectDeque;
    1398    }
    1399
    1400    /**
    1401     * Recovers abandoned objects which have been checked out but
    1402     * not used since longer than the removeAbandonedTimeout.
    1403     *
    1404     * @param abandonedConfig The configuration to use to identify abandoned objects
    1405     */
    1406    @SuppressWarnings("resource") // The PrintWriter is managed elsewhere
    1407    private void removeAbandoned(final AbandonedConfig abandonedConfig) {
    1408        poolMap.forEach((key, value) -> {
    1409            // Generate a list of abandoned objects to remove
    1410            final ArrayList<PooledObject<T>> remove = createRemoveList(abandonedConfig, value.getAllObjects());
    1411            // Now remove the abandoned objects
    1412            remove.forEach(pooledObject -> {
    1413                if (abandonedConfig.getLogAbandoned()) {
    1414                    pooledObject.printStackTrace(abandonedConfig.getLogWriter());
    1415                }
    1416                try {
    1417                    invalidateObject(key, pooledObject.getObject(), DestroyMode.ABANDONED);
    1418                } catch (final Exception e) {
    1419                    swallowException(e);
    1420                }
    1421            });
    1422        });
    1423    }
    1424
    1425    /**
    1426     * Returns an object to a keyed sub-pool.
    1427     * <p>
    1428     * If {@link #getMaxIdlePerKey() maxIdle} is set to a positive value and the
    1429     * number of idle instances under the given key has reached this value, the
    1430     * returning instance is destroyed.
    1431     * </p>
    1432     * <p>
    1433     * If {@link #getTestOnReturn() testOnReturn} == true, the returning
    1434     * instance is validated before being returned to the idle instance sub-pool
    1435     * under the given key. In this case, if validation fails, the instance is
    1436     * destroyed.
    1437     * </p>
    1438     * <p>
    1439     * Exceptions encountered destroying objects for any reason are swallowed
    1440     * but notified via a {@link SwallowedExceptionListener}.
    1441     * </p>
    1442     *
    1443     * @param key pool key
    1444     * @param obj instance to return to the keyed pool
    1445     *
    1446     * @throws IllegalStateException if an object is returned to the pool that
    1447     *                               was not borrowed from it or if an object is
    1448     *                               returned to the pool multiple times
    1449     */
    1450    @Override
    1451    public void returnObject(final K key, final T obj) {
    1452
    1453        final ObjectDeque<T> objectDeque = poolMap.get(key);
    1454
    1455        if (objectDeque == null) {
    1456            throw new IllegalStateException("No keyed pool found under the given key.");
    1457        }
    1458
    1459        final PooledObject<T> p = objectDeque.getAllObjects().get(new IdentityWrapper<>(obj));
    1460
    1461        if (p == null) {
    1462            throw new IllegalStateException("Returned object not currently part of this pool");
    1463        }
    1464
    1465        markReturningState(p);
    1466
    1467        final Duration activeTime = p.getActiveDuration();
    1468
    1469        try {
    1470            if (getTestOnReturn() && !factory.validateObject(key, p)) {
    1471                try {
    1472                    destroy(key, p, true, DestroyMode.NORMAL);
    1473                } catch (final Exception e) {
    1474                    swallowException(e);
    1475                }
    1476                whenWaitersAddObject(key, objectDeque.idleObjects);
    1477                return;
    1478            }
    1479
    1480            try {
    1481                factory.passivateObject(key, p);
    1482            } catch (final Exception e1) {
    1483                swallowException(e1);
    1484                try {
    1485                    destroy(key, p, true, DestroyMode.NORMAL);
    1486                } catch (final Exception e) {
    1487                    swallowException(e);
    1488                }
    1489                whenWaitersAddObject(key, objectDeque.idleObjects);
    1490                return;
    1491            }
    1492
    1493            if (!p.deallocate()) {
    1494                throw new IllegalStateException("Object has already been returned to this pool");
    1495            }
    1496
    1497            final int maxIdle = getMaxIdlePerKey();
    1498            final LinkedBlockingDeque<PooledObject<T>> idleObjects =
    1499                    objectDeque.getIdleObjects();
    1500
    1501            if (isClosed() || maxIdle > -1 && maxIdle <= idleObjects.size()) {
    1502                try {
    1503                    destroy(key, p, true, DestroyMode.NORMAL);
    1504                } catch (final Exception e) {
    1505                    swallowException(e);
    1506                }
    1507            } else {
    1508                if (getLifo()) {
    1509                    idleObjects.addFirst(p);
    1510                } else {
    1511                    idleObjects.addLast(p);
    1512                }
    1513                if (isClosed()) {
    1514                    // Pool closed while object was being added to idle objects.
    1515                    // Make sure the returned object is destroyed rather than left
    1516                    // in the idle object pool (which would effectively be a leak)
    1517                    clear(key);
    1518                }
    1519            }
    1520        } finally {
    1521            if (hasBorrowWaiters()) {
    1522                reuseCapacity();
    1523            }
    1524            updateStatsReturn(activeTime);
    1525        }
    1526    }
    1527
    1528    /**
    1529     * Attempt to create one new instance to serve from the most heavily
    1530     * loaded pool that can add a new instance.
    1531     *
    1532     * This method exists to ensure liveness in the pool when threads are
    1533     * parked waiting and capacity to create instances under the requested keys
    1534     * subsequently becomes available.
    1535     *
    1536     * This method is not guaranteed to create an instance and its selection
    1537     * of the most loaded pool that can create an instance may not always be
    1538     * correct, since it does not lock the pool and instances may be created,
    1539     * borrowed, returned or destroyed by other threads while it is executing.
    1540     */
    1541    private void reuseCapacity() {
    1542        final int maxTotalPerKeySave = getMaxTotalPerKey();
    1543
    1544        // Find the most loaded pool that could take a new instance
    1545        int maxQueueLength = 0;
    1546        LinkedBlockingDeque<PooledObject<T>> mostLoaded = null;
    1547        K loadedKey = null;
    1548        for (final Entry<K, GenericKeyedObjectPool<K, T>.ObjectDeque<T>> entry : poolMap.entrySet()) {
    1549            final K k = entry.getKey();
    1550            final ObjectDeque<T> deque = entry.getValue();
    1551            if (deque != null) {
    1552                final LinkedBlockingDeque<PooledObject<T>> pool = deque.getIdleObjects();
    1553                final int queueLength = pool.getTakeQueueLength();
    1554                if (getNumActive(k) < maxTotalPerKeySave && queueLength > maxQueueLength) {
    1555                    maxQueueLength = queueLength;
    1556                    mostLoaded = pool;
    1557                    loadedKey = k;
    1558                }
    1559            }
    1560        }
    1561
    1562        // Attempt to add an instance to the most loaded pool
    1563        if (mostLoaded != null) {
    1564            register(loadedKey);
    1565            try {
    1566                final PooledObject<T> p = create(loadedKey);
    1567                if (p != null) {
    1568                    addIdleObject(loadedKey, p);
    1569                }
    1570            } catch (final Exception e) {
    1571                swallowException(e);
    1572            } finally {
    1573                deregister(loadedKey);
    1574            }
    1575        }
    1576    }
    1577
    1578    /**
    1579     * Sets the configuration.
    1580     *
    1581     * @param conf the new configuration to use. This is used by value.
    1582     *
    1583     * @see GenericKeyedObjectPoolConfig
    1584     */
    1585    public void setConfig(final GenericKeyedObjectPoolConfig<T> conf) {
    1586        super.setConfig(conf);
    1587        setMaxIdlePerKey(conf.getMaxIdlePerKey());
    1588        setMaxTotalPerKey(conf.getMaxTotalPerKey());
    1589        setMaxTotal(conf.getMaxTotal());
    1590        setMinIdlePerKey(conf.getMinIdlePerKey());
    1591    }
    1592
    1593    /**
    1594     * Sets the cap on the number of "idle" instances per key in the pool.
    1595     * If maxIdlePerKey is set too low on heavily loaded systems it is possible
    1596     * you will see objects being destroyed and almost immediately new objects
    1597     * being created. This is a result of the active threads momentarily
    1598     * returning objects faster than they are requesting them, causing the
    1599     * number of idle objects to rise above maxIdlePerKey. The best value for
    1600     * maxIdlePerKey for heavily loaded system will vary but the default is a
    1601     * good starting point.
    1602     *
    1603     * @param maxIdlePerKey the maximum number of "idle" instances that can be
    1604     *                      held in a given keyed sub-pool. Use a negative value
    1605     *                      for no limit
    1606     *
    1607     * @see #getMaxIdlePerKey
    1608     */
    1609    public void setMaxIdlePerKey(final int maxIdlePerKey) {
    1610        this.maxIdlePerKey = maxIdlePerKey;
    1611    }
    1612
    1613    /**
    1614     * Sets the limit on the number of object instances allocated by the pool
    1615     * (checked out or idle), per key. When the limit is reached, the sub-pool
    1616     * is said to be exhausted. A negative value indicates no limit.
    1617     *
    1618     * @param maxTotalPerKey the limit on the number of active instances per key
    1619     *
    1620     * @see #getMaxTotalPerKey
    1621     */
    1622    public void setMaxTotalPerKey(final int maxTotalPerKey) {
    1623        this.maxTotalPerKey = maxTotalPerKey;
    1624    }
    1625
    1626    /**
    1627     * Sets the target for the minimum number of idle objects to maintain in
    1628     * each of the keyed sub-pools. This setting only has an effect if it is
    1629     * positive and {@link #getDurationBetweenEvictionRuns()} is greater than
    1630     * zero. If this is the case, an attempt is made to ensure that each
    1631     * sub-pool has the required minimum number of instances during idle object
    1632     * eviction runs.
    1633     * <p>
    1634     * If the configured value of minIdlePerKey is greater than the configured
    1635     * value for maxIdlePerKey then the value of maxIdlePerKey will be used
    1636     * instead.
    1637     * </p>
    1638     *
    1639     * @param minIdlePerKey The minimum size of the each keyed pool
    1640     *
    1641     * @see #getMinIdlePerKey()
    1642     * @see #getMaxIdlePerKey()
    1643     * @see #setTimeBetweenEvictionRuns(Duration)
    1644     */
    1645    public void setMinIdlePerKey(final int minIdlePerKey) {
    1646        this.minIdlePerKey = minIdlePerKey;
    1647    }
    1648
    1649    @Override
    1650    protected void toStringAppendFields(final StringBuilder builder) {
    1651        super.toStringAppendFields(builder);
    1652        builder.append(", maxIdlePerKey=");
    1653        builder.append(maxIdlePerKey);
    1654        builder.append(", minIdlePerKey=");
    1655        builder.append(minIdlePerKey);
    1656        builder.append(", maxTotalPerKey=");
    1657        builder.append(maxTotalPerKey);
    1658        builder.append(", factory=");
    1659        builder.append(factory);
    1660        builder.append(", fairness=");
    1661        builder.append(fairness);
    1662        builder.append(", poolMap=");
    1663        builder.append(poolMap);
    1664        builder.append(", poolKeyList=");
    1665        builder.append(poolKeyList);
    1666        builder.append(", keyLock=");
    1667        builder.append(keyLock);
    1668        builder.append(", numTotal=");
    1669        builder.append(numTotal);
    1670        builder.append(", evictionKeyIterator=");
    1671        builder.append(evictionKeyIterator);
    1672        builder.append(", evictionKey=");
    1673        builder.append(evictionKey);
    1674        builder.append(", abandonedConfig=");
    1675        builder.append(abandonedConfig);
    1676    }
    1677
    1678    /**
    1679     * Whether there is at least one thread waiting on this deque, add an pool object.
    1680     * @param key pool key.
    1681     * @param idleObjects list of idle pool objects.
    1682     */
    1683    private void whenWaitersAddObject(final K key, final LinkedBlockingDeque<PooledObject<T>> idleObjects) {
    1684        if (idleObjects.hasTakeWaiters()) {
    1685            try {
    1686                addObject(key);
    1687            } catch (final Exception e) {
    1688                swallowException(e);
    1689            }
    1690        }
    1691    }
    1692
    1693    /**
    1694     * @since 2.10.0
    1695     */
    1696    @Override
    1697    public void use(final T pooledObject) {
    1698        final AbandonedConfig abandonedCfg = this.abandonedConfig;
    1699        if (abandonedCfg != null && abandonedCfg.getUseUsageTracking()) {
    1700            poolMap.values().stream()
    1701                .map(pool -> pool.getAllObjects().get(new IdentityWrapper<>(pooledObject)))
    1702                .filter(Objects::nonNull)
    1703                .findFirst()
    1704                .ifPresent(PooledObject::use);
    1705        }
    1706    }
    1707
    1708}