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/*
* 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
*
* http://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.commons.pool2.impl;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.TimerTask;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
/**
* Provides a shared idle object eviction timer for all pools. This class is
* currently implemented using {@link ScheduledThreadPoolExecutor}. This
* implementation may change in any future release. This class keeps track of
* how many pools are using it. If no pools are using the timer, it is cancelled.
* This prevents a thread being left running which, in application server
* environments, can lead to memory leads and/or prevent applications from
* shutting down or reloading cleanly.
*
* This class has package scope to prevent its inclusion in the pool public API.
* The class declaration below should *not* be changed to public.
*
* This class is intended to be thread-safe.
*
* @since 2.0
*/
class EvictionTimer {
/** Executor instance */
private static ScheduledThreadPoolExecutor executor; //@GuardedBy("EvictionTimer.class")
/** Static usage count tracker */
private static int usageCount; //@GuardedBy("EvictionTimer.class")
/** Prevent instantiation */
private EvictionTimer() {
// Hide the default constructor
}
/**
* @since 2.4.3
*/
@Override
public String toString() {
final StringBuilder builder = new StringBuilder();
builder.append("EvictionTimer []");
return builder.toString();
}
/**
* Add the specified eviction task to the timer. Tasks that are added with a
* call to this method *must* call {@link #cancel(TimerTask)} to cancel the
* task to prevent memory and/or thread leaks in application server
* environments.
* @param task Task to be scheduled
* @param delay Delay in milliseconds before task is executed
* @param period Time in milliseconds between executions
*/
static synchronized void schedule(final Runnable task, final long delay, final long period) {
if (null == executor) {
executor = new ScheduledThreadPoolExecutor(1, new EvictorThreadFactory());
}
usageCount++;
executor.scheduleWithFixedDelay(task, delay, period, TimeUnit.MILLISECONDS);
}
/**
* Remove the specified eviction task from the timer.
*
* @param task Task to be cancelled
* @param timeout If the associated executor is no longer required, how
* long should this thread wait for the executor to
* terminate?
* @param unit The units for the specified timeout
*/
static synchronized void cancel(final TimerTask task, final long timeout, final TimeUnit unit) {
task.cancel();
usageCount--;
if (usageCount == 0) {
executor.shutdown();
try {
executor.awaitTermination(timeout, unit);
} catch (final InterruptedException e) {
// Swallow
// Significant API changes would be required to propagate this
}
executor.setCorePoolSize(0);
executor = null;
}
}
/**
* Thread factory that creates a thread, with the context classloader from this class.
*/
private static class EvictorThreadFactory implements ThreadFactory {
@Override
public Thread newThread(final Runnable r) {
final Thread t = new Thread(null, r, "commons-pool-evictor-thread");
AccessController.doPrivileged(new PrivilegedAction() {
@Override
public Void run() {
t.setContextClassLoader(EvictorThreadFactory.class.getClassLoader());
return null;
}
});
return t;
}
}
}