2 * Copyright (c) 2014 Pantheon Technologies s.r.o. and others. All rights reserved.
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
9 package org.opendaylight.openflowjava.protocol.impl.connection;
11 import io.netty.channel.Channel;
12 import io.netty.channel.ChannelFuture;
13 import io.netty.channel.ChannelHandlerContext;
14 import io.netty.channel.ChannelInboundHandlerAdapter;
15 import io.netty.util.concurrent.EventExecutor;
16 import io.netty.util.concurrent.Future;
17 import io.netty.util.concurrent.GenericFutureListener;
19 import java.net.InetSocketAddress;
20 import java.util.Queue;
21 import java.util.concurrent.LinkedBlockingQueue;
22 import java.util.concurrent.RejectedExecutionException;
23 import java.util.concurrent.TimeUnit;
24 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
26 import org.slf4j.Logger;
27 import org.slf4j.LoggerFactory;
29 import com.google.common.base.Preconditions;
32 * Channel handler which bypasses wraps on top of normal Netty pipeline, allowing
33 * writes to be enqueued from any thread, it then schedules a task pipeline task,
34 * which shuffles messages from the queue into the pipeline.
36 * Note this is an *Inbound* handler, as it reacts to channel writability changing,
37 * which in the Netty vocabulary is an inbound event. This has already changed in
38 * the Netty 5.0.0 API, where Handlers are unified.
40 final class ChannelOutboundQueue extends ChannelInboundHandlerAdapter {
41 public interface MessageHolder<T> {
43 * Take ownership of the encapsulated listener. Guaranteed to
44 * be called at most once.
46 * @return listener encapsulated in the holder, may be null
47 * @throws IllegalStateException if the listener is no longer
48 * available (for example because it has already been
51 GenericFutureListener<Future<Void>> takeListener();
54 * Take ownership of the encapsulated message. Guaranteed to be
55 * called at most once.
57 * @return message encapsulated in the holder, may not be null
58 * @throws IllegalStateException if the message is no longer
59 * available (for example because it has already been
66 * This is the default upper bound we place on the flush task running
67 * a single iteration. We relinquish control after about this amount
70 private static final long DEFAULT_WORKTIME_MICROS = TimeUnit.MILLISECONDS.toMicros(100);
73 * We re-check the time spent flushing every this many messages. We do this because
74 * checking after each message may prove to be CPU-intensive. Set to Integer.MAX_VALUE
75 * or similar to disable the feature.
77 private static final int WORKTIME_RECHECK_MSGS = 64;
78 private static final Logger LOG = LoggerFactory.getLogger(ChannelOutboundQueue.class);
80 // Passed to executor to request triggering of flush
81 private final Runnable flushRunnable = new Runnable() {
84 ChannelOutboundQueue.this.flush();
89 * Instead of using an AtomicBoolean object, we use these two. It saves us
90 * from allocating an extra object.
92 private static final AtomicIntegerFieldUpdater<ChannelOutboundQueue> FLUSH_SCHEDULED_UPDATER =
93 AtomicIntegerFieldUpdater.newUpdater(ChannelOutboundQueue.class, "flushScheduled");
94 private volatile int flushScheduled = 0;
96 private final Queue<MessageHolder<?>> queue;
97 private final long maxWorkTime;
98 private final Channel channel;
99 private final InetSocketAddress address;
101 public ChannelOutboundQueue(final Channel channel, final int queueDepth, final InetSocketAddress address) {
102 Preconditions.checkArgument(queueDepth > 0, "Queue depth has to be positive");
105 * This looks like a good trade-off for throughput. Alternative is
106 * to use an ArrayBlockingQueue -- but that uses a single lock to
107 * synchronize both producers and consumers, potentially leading
108 * to less throughput.
110 this.queue = new LinkedBlockingQueue<>(queueDepth);
111 this.channel = Preconditions.checkNotNull(channel);
112 this.maxWorkTime = TimeUnit.MICROSECONDS.toNanos(DEFAULT_WORKTIME_MICROS);
113 this.address = address;
117 * Enqueue a message holder for transmission. Is a thread-safe entry point
118 * for the channel. If the cannot be placed on the queue, this
120 * @param holder MessageHolder which should be enqueue
121 * @return Success indicator, true if the enqueue operation succeeded,
122 * false if the queue is full.
124 public boolean enqueue(final MessageHolder<?> holder) {
125 LOG.trace("Enqueuing message {}", holder);
126 if (queue.offer(holder)) {
127 LOG.trace("Message enqueued");
132 LOG.trace("Message queue is full");
136 private void scheduleFlush(final EventExecutor executor) {
137 if (FLUSH_SCHEDULED_UPDATER.compareAndSet(this, 0, 1)) {
138 LOG.trace("Scheduling flush task");
139 executor.execute(flushRunnable);
141 LOG.trace("Flush task is already present");
146 * Schedule a queue flush if it is not empty and the channel is found
149 private void conditionalFlush() {
150 if (queue.isEmpty()) {
151 LOG.trace("Queue is empty, not flush needed");
154 if (!channel.isWritable()) {
155 LOG.trace("Channel {} is not writable, not issuing a flush", channel);
159 scheduleFlush(channel.pipeline().lastContext().executor());
163 * The synchronized keyword should be unnecessary, really, but it enforces
164 * queue order should something go terribly wrong. It should be completely
167 private synchronized void flush() {
168 final long start = System.nanoTime();
169 final long deadline = start + maxWorkTime;
171 LOG.debug("Dequeuing messages to channel {}", channel);
174 for (;; ++messages) {
175 if (!channel.isWritable()) {
176 LOG.trace("Channel is no longer writable");
180 final MessageHolder<?> h = queue.poll();
182 LOG.trace("The queue is completely drained");
186 final GenericFutureListener<Future<Void>> l = h.takeListener();
188 final ChannelFuture p;
189 if (address == null) {
190 p = channel.write(new MessageListenerWrapper(h.takeMessage(), l));
192 p = channel.write(new UdpMessageListenerWrapper(h.takeMessage(), l, address));
199 * Check every WORKTIME_RECHECK_MSGS for exceeded time.
201 * XXX: given we already measure our flushing throughput, we
202 * should be able to perform dynamic adjustments here.
203 * is that additional complexity needed, though?
205 if ((messages % WORKTIME_RECHECK_MSGS) == 0 && System.nanoTime() >= deadline) {
206 LOG.trace("Exceeded allotted work time {}us",
207 TimeUnit.NANOSECONDS.toMicros(maxWorkTime));
213 LOG.debug("Flushing {} message(s) to channel {}", messages, channel);
217 final long stop = System.nanoTime();
218 LOG.debug("Flushed {} messages in {}us to channel {}",
219 messages, TimeUnit.NANOSECONDS.toMicros(stop - start), channel);
222 * We are almost ready to terminate. This is a bit tricky, because
223 * we do not want to have a race window where a message would be
224 * stuck on the queue without a flush being scheduled.
226 * So we mark ourselves as not running and then re-check if a
227 * flush out is needed. That will re-synchronized with other threads
228 * such that only one flush is scheduled at any given time.
230 if (!FLUSH_SCHEDULED_UPDATER.compareAndSet(this, 1, 0)) {
231 LOG.warn("Channel {} queue {} flusher found unscheduled", channel, queue);
237 private void conditionalFlush(final ChannelHandlerContext ctx) {
238 Preconditions.checkState(ctx.channel() == channel, "Inconsistent channel %s with context %s", channel, ctx);
243 public void channelActive(final ChannelHandlerContext ctx) throws Exception {
244 super.channelActive(ctx);
245 conditionalFlush(ctx);
249 public void channelWritabilityChanged(final ChannelHandlerContext ctx) throws Exception {
250 super.channelWritabilityChanged(ctx);
251 conditionalFlush(ctx);
255 public void channelInactive(final ChannelHandlerContext ctx) throws Exception {
256 super.channelInactive(ctx);
259 LOG.debug("Channel shutdown, flushing queue...");
260 final Future<Void> result = ctx.newFailedFuture(new RejectedExecutionException("Channel disconnected"));
262 final MessageHolder<?> e = queue.poll();
267 e.takeListener().operationComplete(result);
271 LOG.debug("Flushed {} queue entries", entries);
275 public String toString() {
276 return String.format("Channel %s queue [%s messages flushing=%s]", channel, queue.size(), flushScheduled);