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LinkedQueuePool.java
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LinkedQueuePool.java
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/*
* Copyright (c) 2002-2018 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.collection.pool;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.LongSupplier;
import org.neo4j.function.Factory;
public class LinkedQueuePool<R> implements Pool<R>
{
public interface Monitor<R>
{
void updatedCurrentPeakSize( int currentPeakSize );
void updatedTargetSize( int targetSize );
void created( R resource );
void acquired( R resource );
void disposed( R resource );
class Adapter<R> implements Monitor<R>
{
@Override
public void updatedCurrentPeakSize( int currentPeakSize )
{
}
@Override
public void updatedTargetSize( int targetSize )
{
}
@Override
public void created( R resource )
{
}
@Override
public void acquired( R resource )
{
}
@Override
public void disposed( R resource )
{
}
}
}
public interface CheckStrategy
{
boolean shouldCheck();
class TimeoutCheckStrategy implements CheckStrategy
{
private final long interval;
private long lastCheckTime;
private final LongSupplier clock;
public TimeoutCheckStrategy( long interval )
{
this( interval, System::currentTimeMillis );
}
public TimeoutCheckStrategy( long interval, LongSupplier clock )
{
this.interval = interval;
this.lastCheckTime = clock.getAsLong();
this.clock = clock;
}
@Override
public boolean shouldCheck()
{
long currentTime = clock.getAsLong();
if ( currentTime > lastCheckTime + interval )
{
lastCheckTime = currentTime;
return true;
}
return false;
}
}
}
public static final int DEFAULT_CHECK_INTERVAL = 60 * 1000;
private final Queue<R> unused = new ConcurrentLinkedQueue<>();
private final Monitor monitor;
private final int minSize;
private final Factory<R> factory;
private final CheckStrategy checkStrategy;
// Guarded by nothing. Those are estimates, losing some values doesn't matter much
private final AtomicInteger allocated = new AtomicInteger( 0 );
private final AtomicInteger queueSize = new AtomicInteger( 0 );
private int currentPeakSize;
private int targetSize;
public LinkedQueuePool( int minSize, Factory<R> factory )
{
this( minSize, factory, new CheckStrategy.TimeoutCheckStrategy( DEFAULT_CHECK_INTERVAL ),
new Monitor.Adapter() );
}
public LinkedQueuePool( int minSize, Factory<R> factory, CheckStrategy strategy, Monitor monitor )
{
this.minSize = minSize;
this.factory = factory;
this.currentPeakSize = 0;
this.targetSize = minSize;
this.checkStrategy = strategy;
this.monitor = monitor;
}
protected R create()
{
return factory.newInstance();
}
protected void dispose( R resource )
{
monitor.disposed( resource );
allocated.decrementAndGet();
}
@Override
public final R acquire()
{
R resource = unused.poll();
if ( resource == null )
{
resource = create();
allocated.incrementAndGet();
monitor.created( resource );
}
else
{
queueSize.decrementAndGet();
}
currentPeakSize = Math.max( currentPeakSize, allocated.get() - queueSize.get() );
if ( checkStrategy.shouldCheck() )
{
targetSize = Math.max( minSize, currentPeakSize );
monitor.updatedCurrentPeakSize( currentPeakSize );
currentPeakSize = 0;
monitor.updatedTargetSize( targetSize );
}
monitor.acquired( resource );
return resource;
}
@Override
public void release( R toRelease )
{
if ( queueSize.get() < targetSize )
{
unused.offer( toRelease );
queueSize.incrementAndGet();
}
else
{
dispose( toRelease );
}
}
/**
* Dispose of all pooled objects.
*/
@Override
public void close()
{
for ( R resource = unused.poll(); resource != null; resource = unused.poll() )
{
dispose( resource );
}
}
}