| // |
| // ======================================================================== |
| // Copyright (c) 1995-2015 Mort Bay Consulting Pty. Ltd. |
| // ------------------------------------------------------------------------ |
| // All rights reserved. This program and the accompanying materials |
| // are made available under the terms of the Eclipse Public License v1.0 |
| // and Apache License v2.0 which accompanies this distribution. |
| // |
| // The Eclipse Public License is available at |
| // http://www.eclipse.org/legal/epl-v10.html |
| // |
| // The Apache License v2.0 is available at |
| // http://www.opensource.org/licenses/apache2.0.php |
| // |
| // You may elect to redistribute this code under either of these licenses. |
| // ======================================================================== |
| // |
| |
| package org.eclipse.jetty.util.thread; |
| |
| import java.util.List; |
| import java.util.concurrent.CopyOnWriteArrayList; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.atomic.AtomicReference; |
| |
| import org.eclipse.jetty.util.component.AbstractLifeCycle; |
| import org.eclipse.jetty.util.log.Log; |
| import org.eclipse.jetty.util.log.Logger; |
| |
| /** |
| * <p>A utility class to perform periodic sweeping of resources.</p> |
| * <p>{@link Sweepable} resources may be added to or removed from a |
| * {@link Sweeper} and the resource implementation decides whether |
| * it should be swept or not.</p> |
| * <p>If a {@link Sweepable} resources is itself a container of |
| * other sweepable resources, it will forward the sweep operation |
| * to children resources, and so on recursively.</p> |
| * <p>Typical usage is to add {@link Sweeper} as a bean to an existing |
| * container:</p> |
| * <pre> |
| * Server server = new Server(); |
| * server.addBean(new Sweeper(), true); |
| * server.start(); |
| * </pre> |
| * Code that knows it has sweepable resources can then lookup the |
| * {@link Sweeper} and offer the sweepable resources to it: |
| * <pre> |
| * class MyComponent implements Sweeper.Sweepable |
| * { |
| * private final long creation; |
| * private volatile destroyed; |
| * |
| * MyComponent(Server server) |
| * { |
| * this.creation = System.nanoTime(); |
| * Sweeper sweeper = server.getBean(Sweeper.class); |
| * sweeper.offer(this); |
| * } |
| * |
| * void destroy() |
| * { |
| * destroyed = true; |
| * } |
| * |
| * @Override |
| * public boolean sweep() |
| * { |
| * return destroyed; |
| * } |
| * } |
| * </pre> |
| */ |
| public class Sweeper extends AbstractLifeCycle implements Runnable |
| { |
| private static final Logger LOG = Log.getLogger(Sweeper.class); |
| |
| private final AtomicReference<List<Sweepable>> items = new AtomicReference<>(); |
| private final AtomicReference<Scheduler.Task> task = new AtomicReference<>(); |
| private final Scheduler scheduler; |
| private final long period; |
| |
| public Sweeper(Scheduler scheduler, long period) |
| { |
| this.scheduler = scheduler; |
| this.period = period; |
| } |
| |
| @Override |
| protected void doStart() throws Exception |
| { |
| super.doStart(); |
| items.set(new CopyOnWriteArrayList<Sweepable>()); |
| activate(); |
| } |
| |
| @Override |
| protected void doStop() throws Exception |
| { |
| deactivate(); |
| items.set(null); |
| super.doStop(); |
| } |
| |
| public int getSize() |
| { |
| List<Sweepable> refs = items.get(); |
| return refs == null ? 0 : refs.size(); |
| } |
| |
| public boolean offer(Sweepable sweepable) |
| { |
| List<Sweepable> refs = items.get(); |
| if (refs == null) |
| return false; |
| refs.add(sweepable); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Resource offered {}", sweepable); |
| return true; |
| } |
| |
| public boolean remove(Sweepable sweepable) |
| { |
| List<Sweepable> refs = items.get(); |
| return refs != null && refs.remove(sweepable); |
| } |
| |
| @Override |
| public void run() |
| { |
| List<Sweepable> refs = items.get(); |
| if (refs == null) |
| return; |
| for (Sweepable sweepable : refs) |
| { |
| try |
| { |
| if (sweepable.sweep()) |
| { |
| refs.remove(sweepable); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Resource swept {}", sweepable); |
| } |
| } |
| catch (Throwable x) |
| { |
| LOG.info("Exception while sweeping " + sweepable, x); |
| } |
| } |
| activate(); |
| } |
| |
| private void activate() |
| { |
| if (isRunning()) |
| { |
| Scheduler.Task t = scheduler.schedule(this, period, TimeUnit.MILLISECONDS); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Scheduled in {} ms sweep task {}", period, t); |
| task.set(t); |
| } |
| else |
| { |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Skipping sweep task scheduling"); |
| } |
| } |
| |
| private void deactivate() |
| { |
| Scheduler.Task t = task.getAndSet(null); |
| if (t != null) |
| { |
| boolean cancelled = t.cancel(); |
| if (LOG.isDebugEnabled()) |
| LOG.debug("Cancelled ({}) sweep task {}", cancelled, t); |
| } |
| } |
| |
| /** |
| * <p>A {@link Sweepable} resource implements this interface to |
| * signal to a {@link Sweeper} or to a parent container if it |
| * needs to be swept or not.</p> |
| * <p>Typical implementations will check their own internal state |
| * and return true or false from {@link #sweep()} to indicate |
| * whether they should be swept.</p> |
| */ |
| public interface Sweepable |
| { |
| /** |
| * @return whether this resource should be swept |
| */ |
| public boolean sweep(); |
| } |
| } |