Java tutorial
/* * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved. * * This program and the accompanying materials are made available under the * terms of the Eclipse Public License v1.0 which accompanies this distribution, * and is available at http://www.eclipse.org/legal/epl-v10.html */ package org.opendaylight.mdsal.dom.broker; import org.opendaylight.mdsal.dom.spi.DOMNotificationSubscriptionListener; import org.opendaylight.mdsal.dom.spi.DOMNotificationSubscriptionListenerRegistry; import org.opendaylight.mdsal.dom.api.DOMNotification; import org.opendaylight.mdsal.dom.api.DOMNotificationListener; import org.opendaylight.mdsal.dom.api.DOMNotificationPublishService; import org.opendaylight.mdsal.dom.api.DOMNotificationService; import com.google.common.base.Preconditions; import com.google.common.base.Predicate; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableMultimap; import com.google.common.collect.ImmutableMultimap.Builder; import com.google.common.collect.Multimap; import com.google.common.collect.Multimaps; import com.google.common.util.concurrent.Futures; import com.google.common.util.concurrent.ListenableFuture; import com.lmax.disruptor.EventHandler; import com.lmax.disruptor.InsufficientCapacityException; import com.lmax.disruptor.PhasedBackoffWaitStrategy; import com.lmax.disruptor.WaitStrategy; import com.lmax.disruptor.dsl.Disruptor; import com.lmax.disruptor.dsl.ProducerType; import java.util.Arrays; import java.util.Collection; import java.util.List; import java.util.Set; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; import org.opendaylight.yangtools.concepts.AbstractListenerRegistration; import org.opendaylight.yangtools.concepts.ListenerRegistration; import org.opendaylight.yangtools.util.ListenerRegistry; import org.opendaylight.yangtools.yang.model.api.SchemaPath; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Joint implementation of {@link DOMNotificationPublishService} and {@link DOMNotificationService}. Provides * routing of notifications from publishers to subscribers. * * Internal implementation works by allocating a two-handler Disruptor. The first handler delivers notifications * to subscribed listeners and the second one notifies whoever may be listening on the returned future. Registration * state tracking is performed by a simple immutable multimap -- when a registration or unregistration occurs we * re-generate the entire map from scratch and set it atomically. While registrations/unregistrations synchronize * on this instance, notifications do not take any locks here. * * The fully-blocking {@link #publish(long, DOMNotification, Collection)} and non-blocking {@link #offerNotification(DOMNotification)} * are realized using the Disruptor's native operations. The bounded-blocking {@link #offerNotification(DOMNotification, long, TimeUnit)} * is realized by arming a background wakeup interrupt. */ public final class DOMNotificationRouter implements AutoCloseable, DOMNotificationPublishService, DOMNotificationService, DOMNotificationSubscriptionListenerRegistry { private static final Logger LOG = LoggerFactory.getLogger(DOMNotificationRouter.class); private static final ListenableFuture<Void> NO_LISTENERS = Futures.immediateFuture(null); private static final WaitStrategy DEFAULT_STRATEGY = PhasedBackoffWaitStrategy.withLock(1L, 30L, TimeUnit.MILLISECONDS); private static final EventHandler<DOMNotificationRouterEvent> DISPATCH_NOTIFICATIONS = new EventHandler<DOMNotificationRouterEvent>() { @Override public void onEvent(final DOMNotificationRouterEvent event, final long sequence, final boolean endOfBatch) throws Exception { event.deliverNotification(); } }; private static final EventHandler<DOMNotificationRouterEvent> NOTIFY_FUTURE = new EventHandler<DOMNotificationRouterEvent>() { @Override public void onEvent(final DOMNotificationRouterEvent event, final long sequence, final boolean endOfBatch) { event.setFuture(); } }; private final Disruptor<DOMNotificationRouterEvent> disruptor; private final ExecutorService executor; private volatile Multimap<SchemaPath, ListenerRegistration<? extends DOMNotificationListener>> listeners = ImmutableMultimap .of(); private final ListenerRegistry<DOMNotificationSubscriptionListener> subscriptionListeners = ListenerRegistry .create(); @SuppressWarnings("unchecked") private DOMNotificationRouter(final ExecutorService executor, final int queueDepth, final WaitStrategy strategy) { this.executor = Preconditions.checkNotNull(executor); disruptor = new Disruptor<>(DOMNotificationRouterEvent.FACTORY, queueDepth, executor, ProducerType.MULTI, strategy); disruptor.handleEventsWith(DISPATCH_NOTIFICATIONS); disruptor.after(DISPATCH_NOTIFICATIONS).handleEventsWith(NOTIFY_FUTURE); disruptor.start(); } public static DOMNotificationRouter create(final int queueDepth) { final ExecutorService executor = Executors.newCachedThreadPool(); return new DOMNotificationRouter(executor, queueDepth, DEFAULT_STRATEGY); } public static DOMNotificationRouter create(final int queueDepth, final long spinTime, final long parkTime, final TimeUnit unit) { final ExecutorService executor = Executors.newCachedThreadPool(); final WaitStrategy strategy = PhasedBackoffWaitStrategy.withLock(spinTime, parkTime, unit); return new DOMNotificationRouter(executor, queueDepth, strategy); } @Override public synchronized <T extends DOMNotificationListener> ListenerRegistration<T> registerNotificationListener( final T listener, final Collection<SchemaPath> types) { final ListenerRegistration<T> reg = new AbstractListenerRegistration<T>(listener) { @Override protected void removeRegistration() { final ListenerRegistration<T> me = this; synchronized (DOMNotificationRouter.this) { replaceListeners(ImmutableMultimap.copyOf(Multimaps.filterValues(listeners, new Predicate<ListenerRegistration<? extends DOMNotificationListener>>() { @Override public boolean apply( final ListenerRegistration<? extends DOMNotificationListener> input) { return input != me; } }))); } } }; if (!types.isEmpty()) { final Builder<SchemaPath, ListenerRegistration<? extends DOMNotificationListener>> b = ImmutableMultimap .builder(); b.putAll(listeners); for (final SchemaPath t : types) { b.put(t, reg); } replaceListeners(b.build()); } return reg; } @Override public <T extends DOMNotificationListener> ListenerRegistration<T> registerNotificationListener( final T listener, final SchemaPath... types) { return registerNotificationListener(listener, Arrays.asList(types)); } /** * Swaps registered listeners and triggers notification update * * @param newListeners */ private void replaceListeners( final Multimap<SchemaPath, ListenerRegistration<? extends DOMNotificationListener>> newListeners) { listeners = newListeners; notifyListenerTypesChanged(newListeners.keySet()); } private void notifyListenerTypesChanged(final Set<SchemaPath> typesAfter) { final List<ListenerRegistration<DOMNotificationSubscriptionListener>> listenersAfter = ImmutableList .copyOf(subscriptionListeners.getListeners()); executor.submit(new Runnable() { @Override public void run() { for (final ListenerRegistration<DOMNotificationSubscriptionListener> subListener : listenersAfter) { try { subListener.getInstance().onSubscriptionChanged(typesAfter); } catch (final Exception e) { LOG.warn("Uncaught exception during invoking listener {}", subListener.getInstance(), e); } } } }); } @Override public <L extends DOMNotificationSubscriptionListener> ListenerRegistration<L> registerSubscriptionListener( final L listener) { final Set<SchemaPath> initialTypes = listeners.keySet(); executor.submit(new Runnable() { @Override public void run() { listener.onSubscriptionChanged(initialTypes); } }); return subscriptionListeners.registerWithType(listener); } private ListenableFuture<Void> publish(final long seq, final DOMNotification notification, final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers) { final DOMNotificationRouterEvent event = disruptor.get(seq); final ListenableFuture<Void> future = event.initialize(notification, subscribers); disruptor.getRingBuffer().publish(seq); return future; } @Override public ListenableFuture<? extends Object> putNotification(final DOMNotification notification) throws InterruptedException { final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers = listeners .get(notification.getType()); if (subscribers.isEmpty()) { return NO_LISTENERS; } final long seq = disruptor.getRingBuffer().next(); return publish(seq, notification, subscribers); } private ListenableFuture<? extends Object> tryPublish(final DOMNotification notification, final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers) { final long seq; try { seq = disruptor.getRingBuffer().tryNext(); } catch (final InsufficientCapacityException e) { return DOMNotificationPublishService.REJECTED; } return publish(seq, notification, subscribers); } @Override public ListenableFuture<? extends Object> offerNotification(final DOMNotification notification) { final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers = listeners .get(notification.getType()); if (subscribers.isEmpty()) { return NO_LISTENERS; } return tryPublish(notification, subscribers); } @Override public ListenableFuture<? extends Object> offerNotification(final DOMNotification notification, final long timeout, final TimeUnit unit) throws InterruptedException { final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers = listeners .get(notification.getType()); if (subscribers.isEmpty()) { return NO_LISTENERS; } // Attempt to perform a non-blocking publish first final ListenableFuture<? extends Object> noBlock = tryPublish(notification, subscribers); if (!DOMNotificationPublishService.REJECTED.equals(noBlock)) { return noBlock; } /* * FIXME: we need a background thread, which will watch out for blocking too long. Here * we will arm a tasklet for it and synchronize delivery of interrupt properly. */ throw new UnsupportedOperationException("Not implemented yet"); } @Override public void close() { disruptor.shutdown(); executor.shutdown(); } }