    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.io.PrintWriter;
    020import java.time.Clock;
    021import java.time.Duration;
    022import java.time.Instant;
    023import java.util.Deque;
    024
    025import org.apache.commons.pool2.PooledObject;
    026import org.apache.commons.pool2.PooledObjectState;
    027import org.apache.commons.pool2.TrackedUse;
    028
    029/**
    030 * This wrapper is used to track the additional information, such as state, for
    031 * the pooled objects.
    032 * <p>
    033 * This class is intended to be thread-safe.
    034 * </p>
    035 *
    036 * @param <T> the type of object in the pool
    037 *
    038 * @since 2.0
    039 */
    040public class DefaultPooledObject<T> implements PooledObject<T> {
    041
    042    private final T object;
    043    private PooledObjectState state = PooledObjectState.IDLE; // @GuardedBy("this") to ensure transitions are valid
    044    private final Clock systemClock = Clock.systemUTC();
    045    private final Instant createInstant = now();
    046
    047    private volatile Instant lastBorrowInstant = createInstant;
    048    private volatile Instant lastUseInstant = createInstant;
    049    private volatile Instant lastReturnInstant = createInstant;
    050    private volatile boolean logAbandoned;
    051    private volatile CallStack borrowedBy = NoOpCallStack.INSTANCE;
    052    private volatile CallStack usedBy = NoOpCallStack.INSTANCE;
    053    private volatile long borrowedCount;
    054
    055    /**
    056     * Creates a new instance that wraps the provided object so that the pool can
    057     * track the state of the pooled object.
    058     *
    059     * @param object The object to wrap
    060     */
    061    public DefaultPooledObject(final T object) {
    062        this.object = object;
    063    }
    064
    065    /**
    066     * Allocates the object.
    067     *
    068     * @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
    069     */
    070    @Override
    071    public synchronized boolean allocate() {
    072        if (state == PooledObjectState.IDLE) {
    073            state = PooledObjectState.ALLOCATED;
    074            lastBorrowInstant = now();
    075            lastUseInstant = lastBorrowInstant;
    076            borrowedCount++;
    077            if (logAbandoned) {
    078                borrowedBy.fillInStackTrace();
    079            }
    080            return true;
    081        }
    082        if (state == PooledObjectState.EVICTION) {
    083            // TODO Allocate anyway and ignore eviction test
    084            state = PooledObjectState.EVICTION_RETURN_TO_HEAD;
    085        }
    086        // TODO if validating and testOnBorrow == true then pre-allocate for
    087        // performance
    088        return false;
    089    }
    090
    091    @Override
    092    public int compareTo(final PooledObject<T> other) {
    093        final int compareTo = getLastReturnInstant().compareTo(other.getLastReturnInstant());
    094        if (compareTo == 0) {
    095            // Make sure the natural ordering is broadly consistent with equals
    096            // although this will break down if distinct objects have the same
    097            // identity hash code.
    098            // see java.lang.Comparable Javadocs
    099            return System.identityHashCode(this) - System.identityHashCode(other);
    100        }
    101        return compareTo;
    102    }
    103
    104    /**
    105     * Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
    106     * if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}
    107     * or {@link PooledObjectState#RETURNING RETURNING}.
    108     *
    109     * @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
    110     *         or {@link PooledObjectState#RETURNING RETURNING}.
    111     */
    112    @Override
    113    public synchronized boolean deallocate() {
    114        if (state == PooledObjectState.ALLOCATED || state == PooledObjectState.RETURNING) {
    115            state = PooledObjectState.IDLE;
    116            lastReturnInstant = now();
    117            borrowedBy.clear();
    118            return true;
    119        }
    120
    121        return false;
    122    }
    123
    124    @Override
    125    public synchronized boolean endEvictionTest(
    126            final Deque<PooledObject<T>> idleQueue) {
    127        if (state == PooledObjectState.EVICTION) {
    128            state = PooledObjectState.IDLE;
    129            return true;
    130        }
    131        if (state == PooledObjectState.EVICTION_RETURN_TO_HEAD) {
    132            state = PooledObjectState.IDLE;
    133            idleQueue.offerFirst(this);
    134        }
    135
    136        return false;
    137    }
    138
    139    @Override
    140    public long getActiveTimeMillis() {
    141        return getActiveDuration().toMillis();
    142    }
    143
    144    /**
    145     * Gets the number of times this object has been borrowed.
    146     * @return The number of times this object has been borrowed.
    147     * @since 2.1
    148     */
    149    @Override
    150    public long getBorrowedCount() {
    151        return borrowedCount;
    152    }
    153
    154    @Override
    155    public Instant getCreateInstant() {
    156        return createInstant;
    157    }
    158
    159    @Override
    160    public long getCreateTime() {
    161        return createInstant.toEpochMilli();
    162    }
    163
    164    @Override
    165    public Duration getIdleDuration() {
    166        // elapsed may be negative if:
    167        // - another thread updates lastReturnInstant during the calculation window
    168        // - System.currentTimeMillis() is not monotonic (e.g. system time is set back)
    169        final Duration elapsed = Duration.between(lastReturnInstant, now());
    170        return elapsed.isNegative() ? Duration.ZERO : elapsed;
    171    }
    172
    173    @Override
    174    public Duration getIdleTime() {
    175        return getIdleDuration();
    176    }
    177
    178    @Override
    179    public long getIdleTimeMillis() {
    180        return getIdleDuration().toMillis();
    181    }
    182
    183    @Override
    184    public Instant getLastBorrowInstant() {
    185        return lastBorrowInstant;
    186    }
    187
    188    @Override
    189    public long getLastBorrowTime() {
    190        return lastBorrowInstant.toEpochMilli();
    191    }
    192
    193    @Override
    194    public Instant getLastReturnInstant() {
    195        return lastReturnInstant;
    196    }
    197
    198    @Override
    199    public long getLastReturnTime() {
    200        return lastReturnInstant.toEpochMilli();
    201    }
    202
    203    /**
    204     * Gets an estimate of the last time this object was used.  If the class
    205     * of the pooled object implements {@link TrackedUse}, what is returned is
    206     * the maximum of {@link TrackedUse#getLastUsedInstant()} and
    207     * {@link #getLastBorrowTime()}; otherwise this method gives the same
    208     * value as {@link #getLastBorrowTime()}.
    209     *
    210     * @return the last Instant this object was used.
    211     */
    212    @Override
    213    public Instant getLastUsedInstant() {
    214        if (object instanceof TrackedUse) {
    215            return PoolImplUtils.max(((TrackedUse) object).getLastUsedInstant(), lastUseInstant);
    216        }
    217        return lastUseInstant;
    218    }
    219
    220    /**
    221     * Gets an estimate of the last time this object was used.  If the class
    222     * of the pooled object implements {@link TrackedUse}, what is returned is
    223     * the maximum of {@link TrackedUse#getLastUsedInstant()} and
    224     * {@link #getLastBorrowTime()}; otherwise this method gives the same
    225     * value as {@link #getLastBorrowTime()}.
    226     *
    227     * @return the last time this object was used
    228     */
    229    @Override
    230    public long getLastUsedTime() {
    231        return getLastUsedInstant().toEpochMilli();
    232    }
    233
    234    @Override
    235    public T getObject() {
    236        return object;
    237    }
    238
    239    /**
    240     * Gets the state of this object.
    241     * @return state
    242     */
    243    @Override
    244    public synchronized PooledObjectState getState() {
    245        return state;
    246    }
    247
    248    /**
    249     * Sets the state to {@link PooledObjectState#INVALID INVALID}.
    250     */
    251    @Override
    252    public synchronized void invalidate() {
    253        state = PooledObjectState.INVALID;
    254    }
    255
    256    /**
    257     * Marks the pooled object as {@link PooledObjectState#ABANDONED ABANDONED}.
    258     */
    259    @Override
    260    public synchronized void markAbandoned() {
    261        state = PooledObjectState.ABANDONED;
    262    }
    263
    264    /**
    265     * Marks the pooled object as {@link PooledObjectState#RETURNING RETURNING}.
    266     */
    267    @Override
    268    public synchronized void markReturning() {
    269        state = PooledObjectState.RETURNING;
    270    }
    271
    272    /**
    273     * Gets the current instant of the clock.
    274     *
    275     * @return the current instant of the clock.
    276     */
    277    private Instant now() {
    278        return systemClock.instant();
    279    }
    280
    281    @Override
    282    public void printStackTrace(final PrintWriter writer) {
    283        boolean written = borrowedBy.printStackTrace(writer);
    284        written |= usedBy.printStackTrace(writer);
    285        if (written) {
    286            writer.flush();
    287        }
    288    }
    289
    290    @Override
    291    public void setLogAbandoned(final boolean logAbandoned) {
    292        this.logAbandoned = logAbandoned;
    293    }
    294
    295    /**
    296     * Configures the stack trace generation strategy based on whether or not fully
    297     * detailed stack traces are required. When set to false, abandoned logs may
    298     * only include caller class information rather than method names, line numbers,
    299     * and other normal metadata available in a full stack trace.
    300     *
    301     * @param requireFullStackTrace the new configuration setting for abandoned object
    302     *                              logging
    303     * @since 2.5
    304     */
    305    @Override
    306    public void setRequireFullStackTrace(final boolean requireFullStackTrace) {
    307        borrowedBy = CallStackUtils.newCallStack("'Pooled object created' " +
    308            "yyyy-MM-dd HH:mm:ss Z 'by the following code has not been returned to the pool:'",
    309            true, requireFullStackTrace);
    310        usedBy = CallStackUtils.newCallStack("The last code to use this object was:",
    311            false, requireFullStackTrace);
    312    }
    313
    314    @Override
    315    public synchronized boolean startEvictionTest() {
    316        if (state == PooledObjectState.IDLE) {
    317            state = PooledObjectState.EVICTION;
    318            return true;
    319        }
    320        return false;
    321    }
    322
    323    @Override
    324    public String toString() {
    325        final StringBuilder result = new StringBuilder();
    326        result.append("Object: ");
    327        result.append(object.toString());
    328        result.append(", State: ");
    329        synchronized (this) {
    330            result.append(state.toString());
    331        }
    332        return result.toString();
    333        // TODO add other attributes
    334    }
    335
    336    @Override
    337    public void use() {
    338        lastUseInstant = now();
    339        usedBy.fillInStackTrace();
    340    }
    341
    342
    343}