e814dd254153d6ae8c32e38f7a6745a4e79d7e2e
[controller.git] / opendaylight / md-sal / sal-dom-broker / src / main / java / org / opendaylight / controller / md / sal / dom / broker / impl / DOMNotificationRouter.java
1 /*
2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
3  *
4  * This program and the accompanying materials are made available under the
5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6  * and is available at http://www.eclipse.org/legal/epl-v10.html
7  */
8 package org.opendaylight.controller.md.sal.dom.broker.impl;
9
10 import com.google.common.base.Preconditions;
11 import com.google.common.base.Predicate;
12 import com.google.common.collect.ImmutableMultimap;
13 import com.google.common.collect.ImmutableMultimap.Builder;
14 import com.google.common.collect.Multimap;
15 import com.google.common.collect.Multimaps;
16 import com.google.common.util.concurrent.Futures;
17 import com.google.common.util.concurrent.ListenableFuture;
18 import com.lmax.disruptor.EventHandler;
19 import com.lmax.disruptor.InsufficientCapacityException;
20 import com.lmax.disruptor.PhasedBackoffWaitStrategy;
21 import com.lmax.disruptor.WaitStrategy;
22 import com.lmax.disruptor.dsl.Disruptor;
23 import com.lmax.disruptor.dsl.ProducerType;
24 import java.util.Arrays;
25 import java.util.Collection;
26 import java.util.concurrent.ExecutorService;
27 import java.util.concurrent.Executors;
28 import java.util.concurrent.TimeUnit;
29 import org.opendaylight.controller.md.sal.dom.api.DOMNotification;
30 import org.opendaylight.controller.md.sal.dom.api.DOMNotificationListener;
31 import org.opendaylight.controller.md.sal.dom.api.DOMNotificationPublishService;
32 import org.opendaylight.controller.md.sal.dom.api.DOMNotificationService;
33 import org.opendaylight.yangtools.concepts.AbstractListenerRegistration;
34 import org.opendaylight.yangtools.concepts.ListenerRegistration;
35 import org.opendaylight.yangtools.yang.model.api.SchemaPath;
36
37 /**
38  * Joint implementation of {@link DOMNotificationPublishService} and {@link DOMNotificationService}. Provides
39  * routing of notifications from publishers to subscribers.
40  *
41  * Internal implementation works by allocating a two-handler Disruptor. The first handler delivers notifications
42  * to subscribed listeners and the second one notifies whoever may be listening on the returned future. Registration
43  * state tracking is performed by a simple immutable multimap -- when a registration or unregistration occurs we
44  * re-generate the entire map from scratch and set it atomically. While registrations/unregistrations synchronize
45  * on this instance, notifications do not take any locks here.
46  *
47  * The fully-blocking {@link #publish(long, DOMNotification, Collection)} and non-blocking {@link #offerNotification(DOMNotification)}
48  * are realized using the Disruptor's native operations. The bounded-blocking {@link #offerNotification(DOMNotification, long, TimeUnit)}
49  * is realized by arming a background wakeup interrupt.
50  */
51 public final class DOMNotificationRouter implements AutoCloseable, DOMNotificationPublishService, DOMNotificationService {
52     private static final ListenableFuture<Void> NO_LISTENERS = Futures.immediateFuture(null);
53     private static final WaitStrategy DEFAULT_STRATEGY = PhasedBackoffWaitStrategy.withLock(1L, 30L, TimeUnit.MILLISECONDS);
54     private static final EventHandler<DOMNotificationRouterEvent> DISPATCH_NOTIFICATIONS = new EventHandler<DOMNotificationRouterEvent>() {
55         @Override
56         public void onEvent(final DOMNotificationRouterEvent event, final long sequence, final boolean endOfBatch) throws Exception {
57             event.deliverNotification();
58
59         }
60     };
61     private static final EventHandler<DOMNotificationRouterEvent> NOTIFY_FUTURE = new EventHandler<DOMNotificationRouterEvent>() {
62         @Override
63         public void onEvent(final DOMNotificationRouterEvent event, final long sequence, final boolean endOfBatch) {
64             event.setFuture();
65         }
66     };
67
68     private final Disruptor<DOMNotificationRouterEvent> disruptor;
69     private final ExecutorService executor;
70     private volatile Multimap<SchemaPath, ListenerRegistration<? extends DOMNotificationListener>> listeners = ImmutableMultimap.of();
71
72     private DOMNotificationRouter(final ExecutorService executor, final Disruptor<DOMNotificationRouterEvent> disruptor) {
73         this.executor = Preconditions.checkNotNull(executor);
74         this.disruptor = Preconditions.checkNotNull(disruptor);
75     }
76
77     @SuppressWarnings("unchecked")
78     public static DOMNotificationRouter create(final int queueDepth) {
79         final ExecutorService executor = Executors.newCachedThreadPool();
80         final Disruptor<DOMNotificationRouterEvent> disruptor = new Disruptor<>(DOMNotificationRouterEvent.FACTORY, queueDepth, executor, ProducerType.MULTI, DEFAULT_STRATEGY);
81
82         disruptor.handleEventsWith(DISPATCH_NOTIFICATIONS);
83         disruptor.after(DISPATCH_NOTIFICATIONS).handleEventsWith(NOTIFY_FUTURE);
84         disruptor.start();
85
86         return new DOMNotificationRouter(executor, disruptor);
87     }
88
89     @Override
90     public synchronized <T extends DOMNotificationListener> ListenerRegistration<T> registerNotificationListener(final T listener, final Collection<SchemaPath> types) {
91         final ListenerRegistration<T> reg = new AbstractListenerRegistration<T>(listener) {
92             @Override
93             protected void removeRegistration() {
94                 final ListenerRegistration<T> me = this;
95
96                 synchronized (DOMNotificationRouter.this) {
97                     listeners = ImmutableMultimap.copyOf(Multimaps.filterValues(listeners, new Predicate<ListenerRegistration<? extends DOMNotificationListener>>() {
98                         @Override
99                         public boolean apply(final ListenerRegistration<? extends DOMNotificationListener> input) {
100                             return input != me;
101                         }
102                     }));
103                 }
104             }
105         };
106
107         if (!types.isEmpty()) {
108             final Builder<SchemaPath, ListenerRegistration<? extends DOMNotificationListener>> b = ImmutableMultimap.builder();
109             b.putAll(listeners);
110
111             for (SchemaPath t : types) {
112                 b.put(t, reg);
113             }
114
115             listeners = b.build();
116         }
117
118         return reg;
119     }
120
121     @Override
122     public <T extends DOMNotificationListener> ListenerRegistration<T> registerNotificationListener(final T listener, final SchemaPath... types) {
123         return registerNotificationListener(listener, Arrays.asList(types));
124     }
125
126     private ListenableFuture<Void> publish(final long seq, final DOMNotification notification, final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers) {
127         final DOMNotificationRouterEvent event = disruptor.get(seq);
128         final ListenableFuture<Void> future = event.initialize(notification, subscribers);
129         disruptor.getRingBuffer().publish(seq);
130         return future;
131     }
132
133     @Override
134     public ListenableFuture<? extends Object> putNotification(final DOMNotification notification) throws InterruptedException {
135         final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers = listeners.get(notification.getType());
136         if (subscribers.isEmpty()) {
137             return NO_LISTENERS;
138         }
139
140         final long seq = disruptor.getRingBuffer().next();
141         return publish(seq, notification, subscribers);
142     }
143
144     private ListenableFuture<? extends Object> tryPublish(final DOMNotification notification, final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers) {
145         final long seq;
146         try {
147              seq = disruptor.getRingBuffer().tryNext();
148         } catch (InsufficientCapacityException e) {
149             return DOMNotificationPublishService.REJECTED;
150         }
151
152         return publish(seq, notification, subscribers);
153     }
154
155     @Override
156     public ListenableFuture<? extends Object> offerNotification(final DOMNotification notification) {
157         final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers = listeners.get(notification.getType());
158         if (subscribers.isEmpty()) {
159             return NO_LISTENERS;
160         }
161
162         return tryPublish(notification, subscribers);
163     }
164
165     @Override
166     public ListenableFuture<? extends Object> offerNotification(final DOMNotification notification, final long timeout,
167             final TimeUnit unit) throws InterruptedException {
168         final Collection<ListenerRegistration<? extends DOMNotificationListener>> subscribers = listeners.get(notification.getType());
169         if (subscribers.isEmpty()) {
170             return NO_LISTENERS;
171         }
172
173         // Attempt to perform a non-blocking publish first
174         final ListenableFuture<? extends Object> noBlock = tryPublish(notification, subscribers);
175         if (!DOMNotificationPublishService.REJECTED.equals(noBlock)) {
176             return noBlock;
177         }
178
179         /*
180          * FIXME: we need a background thread, which will watch out for blocking too long. Here
181          *        we will arm a tasklet for it and synchronize delivery of interrupt properly.
182          */
183         throw new UnsupportedOperationException("Not implemented yet");
184     }
185
186     @Override
187     public void close() {
188         disruptor.shutdown();
189         executor.shutdown();
190     }
191 }

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