/*
* 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.concurrent.ScheduledFuture;
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 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
/**
* Provides a shared idle object eviction timer for all pools.
* <p>
* 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.
* </p>
* <p>
* This class has package scope to prevent its inclusion in the pool public API. The class declaration below should
* *not* be changed to public.
* </p>
* <p>
* This class is intended to be thread-safe.
* </p>
*
* @since 2.0
*/
class EvictionTimer {
Executor instance /** Executor instance */
private static ScheduledThreadPoolExecutor executor; //@GuardedBy("EvictionTimer.class")
Prevents instantiation /** Prevents instantiation */
private EvictionTimer() {
// Hide the default constructor
}
Since: 2.4.3
/**
* @since 2.4.3
*/
@Override
public String toString() {
final StringBuilder builder = new StringBuilder();
builder.append("EvictionTimer []");
return builder.toString();
}
Adds the specified eviction task to the timer. Tasks that are added with a call to this method *must* call cancel() to cancel the task to prevent memory and/or thread leaks in application server environments. Params: - task – Task to be scheduled.
- delay – Delay in milliseconds before task is executed.
- period – Time in milliseconds between executions.
/**
* Adds the specified eviction task to the timer. Tasks that are added with a
* call to this method *must* call {@link #cancel()} 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 BaseGenericObjectPool<?>.Evictor task, final long delay, final long period) {
if (null == executor) {
executor = new ScheduledThreadPoolExecutor(1, new EvictorThreadFactory());
executor.setRemoveOnCancelPolicy(true);
}
final ScheduledFuture<?> scheduledFuture =
executor.scheduleWithFixedDelay(task, delay, period, TimeUnit.MILLISECONDS);
task.setScheduledFuture(scheduledFuture);
}
Removes the specified eviction task from the timer.
Params: - evictor – Task to be cancelled.
- timeout – If the associated executor is no longer required, how
long should this thread wait for the executor to
terminate?
- unit – The units for the specified timeout.
/**
* Removes the specified eviction task from the timer.
*
* @param evictor 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 BaseGenericObjectPool<?>.Evictor evictor, final long timeout, final TimeUnit unit) {
if (evictor != null) {
evictor.cancel();
}
if (executor != null && executor.getQueue().isEmpty()) {
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 daemon thread, with the context class loader from this class.
/**
* Thread factory that creates a daemon thread, with the context class loader from this class.
*/
private static class EvictorThreadFactory implements ThreadFactory {
@Override
public Thread newThread(final Runnable runnable) {
final Thread thread = new Thread(null, runnable, "commons-pool-evictor-thread");
thread.setDaemon(true); // POOL-363 - Required for applications using Runtime.addShutdownHook().
AccessController.doPrivileged(new PrivilegedAction<Void>() {
@Override
public Void run() {
thread.setContextClassLoader(EvictorThreadFactory.class.getClassLoader());
return null;
}
});
return thread;
}
}
}