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