/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.tomcat.dbcp.pool2.impl;
import java.io.PrintWriter;
import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.util.Deque;
import org.apache.tomcat.dbcp.pool2.PooledObject;
import org.apache.tomcat.dbcp.pool2.PooledObjectState;
import org.apache.tomcat.dbcp.pool2.TrackedUse;
/**
* This wrapper is used to track the additional information, such as state, for
* the pooled objects.
* <p>
* This class is intended to be thread-safe.
* </p>
*
* @param <T> the type of object in the pool
* @since 2.0
*/
public class DefaultPooledObject<T> implements PooledObject<T> {
private final T object;
private PooledObjectState state = PooledObjectState.IDLE; // @GuardedBy("this") to ensure transitions are valid
private final Clock systemClock = Clock.systemUTC();
private final Instant createInstant = now();
private volatile Instant lastBorrowInstant = createInstant;
private volatile Instant lastUseInstant = createInstant;
private volatile Instant lastReturnInstant = createInstant;
private volatile boolean logAbandoned;
private volatile CallStack borrowedBy = NoOpCallStack.INSTANCE;
private volatile CallStack usedBy = NoOpCallStack.INSTANCE;
private volatile long borrowedCount;
/**
* Creates a new instance that wraps the provided object so that the pool can
* track the state of the pooled object.
*
* @param object The object to wrap
*/
public DefaultPooledObject(final T object) {
this.object = object;
}
/**
* Allocates the object.
*
* @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
*/
@Override
public synchronized boolean allocate() {
if (state == PooledObjectState.IDLE) {
state = PooledObjectState.ALLOCATED;
lastBorrowInstant = now();
lastUseInstant = lastBorrowInstant;
borrowedCount++;
if (logAbandoned) {
borrowedBy.fillInStackTrace();
}
return true;
}
if (state == PooledObjectState.EVICTION) {
// TODO Allocate anyway and ignore eviction test
state = PooledObjectState.EVICTION_RETURN_TO_HEAD;
}
// TODO if validating and testOnBorrow == true then pre-allocate for
// performance
return false;
}
@Override
public int compareTo(final PooledObject<T> other) {
final int compareTo = getLastReturnInstant().compareTo(other.getLastReturnInstant());
if (compareTo == 0) {
// Make sure the natural ordering is broadly consistent with equals
// although this will break down if distinct objects have the same
// identity hash code.
// see java.lang.Comparable Javadocs
return System.identityHashCode(this) - System.identityHashCode(other);
}
return compareTo;
}
/**
* Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
* if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}
* or {@link PooledObjectState#RETURNING RETURNING}.
*
* @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
* or {@link PooledObjectState#RETURNING RETURNING}.
*/
@Override
public synchronized boolean deallocate() {
if (state == PooledObjectState.ALLOCATED || state == PooledObjectState.RETURNING) {
state = PooledObjectState.IDLE;
lastReturnInstant = now();
borrowedBy.clear();
return true;
}
return false;
}
@Override
public synchronized boolean endEvictionTest(
final Deque<PooledObject<T>> idleQueue) {
if (state == PooledObjectState.EVICTION) {
state = PooledObjectState.IDLE;
return true;
}
if (state == PooledObjectState.EVICTION_RETURN_TO_HEAD) {
state = PooledObjectState.IDLE;
idleQueue.offerFirst(this);
}
return false;
}
@Override
public long getActiveTimeMillis() {
return getActiveDuration().toMillis();
}
/**
* Gets the number of times this object has been borrowed.
* @return The number of times this object has been borrowed.
* @since 2.1
*/
@Override
public long getBorrowedCount() {
return borrowedCount;
}
@Override
public Instant getCreateInstant() {
return createInstant;
}
@Override
public long getCreateTime() {
return createInstant.toEpochMilli();
}
@Override
public Duration getIdleDuration() {
// elapsed may be negative if:
// - another thread updates lastReturnInstant during the calculation window
// - System.currentTimeMillis() is not monotonic (e.g. system time is set back)
final Duration elapsed = Duration.between(lastReturnInstant, now());
return elapsed.isNegative() ? Duration.ZERO : elapsed;
}
@Override
public Duration getIdleTime() {
return getIdleDuration();
}
@Override
public long getIdleTimeMillis() {
return getIdleDuration().toMillis();
}
@Override
public Instant getLastBorrowInstant() {
return lastBorrowInstant;
}
@Override
public long getLastBorrowTime() {
return lastBorrowInstant.toEpochMilli();
}
@Override
public Instant getLastReturnInstant() {
return lastReturnInstant;
}
@Override
public long getLastReturnTime() {
return lastReturnInstant.toEpochMilli();
}
/**
* Gets an estimate of the last time this object was used. If the class
* of the pooled object implements {@link TrackedUse}, what is returned is
* the maximum of {@link TrackedUse#getLastUsedInstant()} and
* {@link #getLastBorrowTime()}; otherwise this method gives the same
* value as {@link #getLastBorrowTime()}.
*
* @return the last Instant this object was used.
*/
@Override
public Instant getLastUsedInstant() {
if (object instanceof TrackedUse) {
return PoolImplUtils.max(((TrackedUse) object).getLastUsedInstant(), lastUseInstant);
}
return lastUseInstant;
}
/**
* Gets an estimate of the last time this object was used. If the class
* of the pooled object implements {@link TrackedUse}, what is returned is
* the maximum of {@link TrackedUse#getLastUsedInstant()} and
* {@link #getLastBorrowTime()}; otherwise this method gives the same
* value as {@link #getLastBorrowTime()}.
*
* @return the last time this object was used
*/
@Override
public long getLastUsedTime() {
return getLastUsedInstant().toEpochMilli();
}
@Override
public T getObject() {
return object;
}
/**
* Gets the state of this object.
* @return state
*/
@Override
public synchronized PooledObjectState getState() {
return state;
}
/**
* Sets the state to {@link PooledObjectState#INVALID INVALID}.
*/
@Override
public synchronized void invalidate() {
state = PooledObjectState.INVALID;
}
/**
* Marks the pooled object as {@link PooledObjectState#ABANDONED ABANDONED}.
*/
@Override
public synchronized void markAbandoned() {
state = PooledObjectState.ABANDONED;
}
/**
* Marks the pooled object as {@link PooledObjectState#RETURNING RETURNING}.
*/
@Override
public synchronized void markReturning() {
state = PooledObjectState.RETURNING;
}
/**
* Gets the current instant of the clock.
*
* @return the current instant of the clock.
*/
private Instant now() {
return systemClock.instant();
}
@Override
public void printStackTrace(final PrintWriter writer) {
boolean written = borrowedBy.printStackTrace(writer);
written |= usedBy.printStackTrace(writer);
if (written) {
writer.flush();
}
}
@Override
public void setLogAbandoned(final boolean logAbandoned) {
this.logAbandoned = logAbandoned;
}
/**
* Configures the stack trace generation strategy based on whether or not fully
* detailed stack traces are required. When set to false, abandoned logs may
* only include caller class information rather than method names, line numbers,
* and other normal metadata available in a full stack trace.
*
* @param requireFullStackTrace the new configuration setting for abandoned object
* logging
* @since 2.5
*/
@Override
public void setRequireFullStackTrace(final boolean requireFullStackTrace) {
borrowedBy = new ThrowableCallStack("'Pooled object created' " +
"yyyy-MM-dd HH:mm:ss Z 'by the following code has not been returned to the pool:'", true);
usedBy = new ThrowableCallStack("The last code to use this object was:", false);
}
@Override
public synchronized boolean startEvictionTest() {
if (state == PooledObjectState.IDLE) {
state = PooledObjectState.EVICTION;
return true;
}
return false;
}
@Override
public String toString() {
final StringBuilder result = new StringBuilder();
result.append("Object: ");
result.append(object.toString());
result.append(", State: ");
synchronized (this) {
result.append(state.toString());
}
return result.toString();
// TODO add other attributes
}
@Override
public void use() {
lastUseInstant = now();
usedBy.fillInStackTrace();
}
}