    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.dbcp2;
    018
    019import java.lang.ref.WeakReference;
    020import java.sql.SQLException;
    021import java.time.Instant;
    022import java.util.ArrayList;
    023import java.util.Collections;
    024import java.util.Iterator;
    025import java.util.List;
    026import java.util.function.Consumer;
    027
    028import org.apache.commons.pool2.TrackedUse;
    029
    030/**
    031 * Tracks connection usage for recovering and reporting abandoned connections.
    032 * <p>
    033 * The JDBC Connection, Statement, and ResultSet classes extend this class.
    034 * </p>
    035 *
    036 * @since 2.0
    037 */
    038public class AbandonedTrace implements TrackedUse, AutoCloseable {
    039
    040    static void add(final AbandonedTrace receiver, final AbandonedTrace trace) {
    041        if (receiver != null) {
    042            receiver.addTrace(trace);
    043        }
    044    }
    045
    046    /** A list of objects created by children of this object. */
    047    private final List<WeakReference<AbandonedTrace>> traceList = new ArrayList<>();
    048
    049    /** Last time this connection was used. */
    050    private volatile Instant lastUsedInstant = Instant.EPOCH;
    051
    052    /**
    053     * Creates a new AbandonedTrace without config and without doing abandoned tracing.
    054     */
    055    public AbandonedTrace() {
    056        init(null);
    057    }
    058
    059    /**
    060     * Constructs a new AbandonedTrace with a parent object.
    061     *
    062     * @param parent
    063     *            AbandonedTrace parent object.
    064     */
    065    public AbandonedTrace(final AbandonedTrace parent) {
    066        init(parent);
    067    }
    068
    069    /**
    070     * Adds an object to the list of objects being traced.
    071     *
    072     * @param trace
    073     *            AbandonedTrace object to add.
    074     */
    075    protected void addTrace(final AbandonedTrace trace) {
    076        synchronized (this.traceList) {
    077            this.traceList.add(new WeakReference<>(trace));
    078        }
    079        setLastUsed();
    080    }
    081
    082    /**
    083     * Clears the list of objects being traced by this object.
    084     */
    085    protected void clearTrace() {
    086        synchronized (this.traceList) {
    087            this.traceList.clear();
    088        }
    089    }
    090
    091    /**
    092     * Subclasses can implement this nop.
    093     *
    094     * @throws SQLException Ignored here, for subclasses.
    095     * @since 2.10.0
    096     */
    097    @Override
    098    public void close() throws SQLException {
    099        // nop
    100    }
    101
    102    /**
    103     * Closes this resource and if an exception is caught, then calls {@code exceptionHandler}.
    104     *
    105     * @param exceptionHandler Consumes exception thrown closing this resource.
    106     * @since 2.10.0
    107     */
    108    protected void close(final Consumer<Exception> exceptionHandler) {
    109        Utils.close(this, exceptionHandler);
    110    }
    111
    112    /**
    113     * Gets the last time this object was used in milliseconds.
    114     *
    115     * @return long time in milliseconds.
    116     */
    117    @Override
    118    @Deprecated
    119    public long getLastUsed() {
    120        return lastUsedInstant.toEpochMilli();
    121    }
    122
    123    @Override
    124    public Instant getLastUsedInstant() {
    125        return lastUsedInstant;
    126    }
    127
    128    /**
    129     * Gets a list of objects being traced by this object.
    130     *
    131     * @return List of objects.
    132     */
    133    protected List<AbandonedTrace> getTrace() {
    134        final int size = traceList.size();
    135        if (size == 0) {
    136            return Collections.emptyList();
    137        }
    138        final ArrayList<AbandonedTrace> result = new ArrayList<>(size);
    139        synchronized (this.traceList) {
    140            final Iterator<WeakReference<AbandonedTrace>> iter = traceList.iterator();
    141            while (iter.hasNext()) {
    142                final AbandonedTrace trace = iter.next().get();
    143                if (trace == null) {
    144                    // Clean-up since we are here anyway
    145                    iter.remove();
    146                } else {
    147                    result.add(trace);
    148                }
    149            }
    150        }
    151        return result;
    152    }
    153
    154    /**
    155     * Initializes abandoned tracing for this object.
    156     *
    157     * @param parent
    158     *            AbandonedTrace parent object.
    159     */
    160    private void init(final AbandonedTrace parent) {
    161        AbandonedTrace.add(parent, this);
    162    }
    163
    164    /**
    165     * Removes this object the source object is tracing.
    166     *
    167     * @param source The object tracing
    168     * @since 2.7.0
    169     */
    170    protected void removeThisTrace(final Object source) {
    171        if (source instanceof AbandonedTrace) {
    172            AbandonedTrace.class.cast(source).removeTrace(this);
    173        }
    174    }
    175
    176    /**
    177     * Removes a child object this object is tracing.
    178     *
    179     * @param trace
    180     *            AbandonedTrace object to remove.
    181     */
    182    protected void removeTrace(final AbandonedTrace trace) {
    183        synchronized (this.traceList) {
    184            final Iterator<WeakReference<AbandonedTrace>> iter = traceList.iterator();
    185            while (iter.hasNext()) {
    186                final AbandonedTrace traceInList = iter.next().get();
    187                if (trace != null && trace.equals(traceInList)) {
    188                    iter.remove();
    189                    break;
    190                }
    191                if (traceInList == null) {
    192                    // Clean-up since we are here anyway
    193                    iter.remove();
    194                }
    195            }
    196        }
    197    }
    198
    199    /**
    200     * Sets the time this object was last used to the current time in milliseconds.
    201     */
    202    protected void setLastUsed() {
    203        lastUsedInstant = Instant.now();
    204    }
    205
    206    /**
    207     * Sets the instant this object was last used.
    208     *
    209     * @param lastUsedInstant
    210     *            instant.
    211     * @since 2.10.0
    212     */
    213    protected void setLastUsed(final Instant lastUsedInstant) {
    214        this.lastUsedInstant = lastUsedInstant;
    215    }
    216
    217    /**
    218     * Sets the time in milliseconds this object was last used.
    219     *
    220     * @param lastUsedMillis
    221     *            time in milliseconds.
    222     * @deprecated Use {@link #setLastUsed(Instant)}
    223     */
    224    @Deprecated
    225    protected void setLastUsed(final long lastUsedMillis) {
    226        this.lastUsedInstant = Instant.ofEpochMilli(lastUsedMillis);
    227    }
    228}