2012-06-04 22:31:44 +02:00
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/*
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* Copyright 2012 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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2012-05-26 00:51:22 +02:00
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package io.netty.channel.socket.nio;
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2012-08-10 13:17:18 +02:00
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import io.netty.channel.Channel;
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import io.netty.channel.ChannelException;
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import io.netty.channel.SingleThreadEventLoop;
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2012-08-18 11:40:21 +02:00
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import io.netty.channel.TaskScheduler;
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2012-08-10 13:17:18 +02:00
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import io.netty.channel.socket.nio.AbstractNioChannel.NioUnsafe;
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import io.netty.logging.InternalLogger;
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import io.netty.logging.InternalLoggerFactory;
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2012-05-26 00:51:22 +02:00
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2012-08-10 13:17:18 +02:00
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import java.io.IOException;
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import java.nio.channels.CancelledKeyException;
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import java.nio.channels.SelectionKey;
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import java.nio.channels.Selector;
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2012-05-26 00:51:22 +02:00
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import java.nio.channels.spi.SelectorProvider;
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2012-08-10 13:17:18 +02:00
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.Iterator;
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2012-08-18 11:48:44 +02:00
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import java.util.Queue;
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2012-08-10 13:17:18 +02:00
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import java.util.Set;
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2012-08-18 11:48:44 +02:00
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import java.util.concurrent.ConcurrentLinkedQueue;
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2012-05-26 00:51:22 +02:00
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import java.util.concurrent.ThreadFactory;
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2012-08-10 13:17:18 +02:00
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import java.util.concurrent.atomic.AtomicBoolean;
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2012-05-26 00:51:22 +02:00
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2012-08-10 13:17:18 +02:00
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final class NioEventLoop extends SingleThreadEventLoop {
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2012-05-26 00:51:22 +02:00
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2012-08-10 13:17:18 +02:00
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/**
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* Internal Netty logger.
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*/
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protected static final InternalLogger logger = InternalLoggerFactory
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.getInstance(NioEventLoop.class);
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static final int CLEANUP_INTERVAL = 256; // XXX Hard-coded value, but won't need customization.
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/**
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* The NIO {@link Selector}.
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*/
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protected final Selector selector;
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/**
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* Boolean that controls determines if a blocked Selector.select should
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* break out of its selection process. In our case we use a timeone for
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* the select method and the select method will block for that time unless
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* waken up.
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*/
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protected final AtomicBoolean wakenUp = new AtomicBoolean();
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private int cancelledKeys;
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private boolean cleanedCancelledKeys;
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2012-08-18 11:40:21 +02:00
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NioEventLoop(
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NioEventLoopGroup parent, ThreadFactory threadFactory,
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TaskScheduler scheduler, SelectorProvider selectorProvider) {
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super(parent, threadFactory, scheduler);
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2012-08-10 13:17:18 +02:00
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if (selectorProvider == null) {
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throw new NullPointerException("selectorProvider");
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}
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selector = openSelector(selectorProvider);
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2012-06-06 16:02:47 +02:00
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}
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2012-05-26 00:51:22 +02:00
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2012-08-10 13:17:18 +02:00
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private static Selector openSelector(SelectorProvider provider) {
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try {
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return provider.openSelector();
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} catch (IOException e) {
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throw new ChannelException("failed to open a new selector", e);
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}
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2012-05-26 00:51:22 +02:00
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}
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2012-08-18 11:48:44 +02:00
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@Override
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protected Queue<Runnable> newTaskQueue() {
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// This event loop never calls takeTask()
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return new ConcurrentLinkedQueue<Runnable>();
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}
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2012-08-10 13:17:18 +02:00
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@Override
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protected void run() {
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Selector selector = this.selector;
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for (;;) {
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wakenUp.set(false);
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try {
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SelectorUtil.select(selector);
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// 'wakenUp.compareAndSet(false, true)' is always evaluated
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// before calling 'selector.wakeup()' to reduce the wake-up
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// overhead. (Selector.wakeup() is an expensive operation.)
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//
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// However, there is a race condition in this approach.
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// The race condition is triggered when 'wakenUp' is set to
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// true too early.
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//
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// 'wakenUp' is set to true too early if:
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// 1) Selector is waken up between 'wakenUp.set(false)' and
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// 'selector.select(...)'. (BAD)
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// 2) Selector is waken up between 'selector.select(...)' and
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// 'if (wakenUp.get()) { ... }'. (OK)
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//
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// In the first case, 'wakenUp' is set to true and the
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// following 'selector.select(...)' will wake up immediately.
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// Until 'wakenUp' is set to false again in the next round,
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// 'wakenUp.compareAndSet(false, true)' will fail, and therefore
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// any attempt to wake up the Selector will fail, too, causing
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// the following 'selector.select(...)' call to block
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// unnecessarily.
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//
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// To fix this problem, we wake up the selector again if wakenUp
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// is true immediately after selector.select(...).
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// It is inefficient in that it wakes up the selector for both
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// the first case (BAD - wake-up required) and the second case
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// (OK - no wake-up required).
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if (wakenUp.get()) {
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selector.wakeup();
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}
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cancelledKeys = 0;
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runAllTasks();
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processSelectedKeys();
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if (isShutdown()) {
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closeAll();
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if (peekTask() == null) {
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break;
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}
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}
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} catch (Throwable t) {
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logger.warn(
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"Unexpected exception in the selector loop.", t);
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// Prevent possible consecutive immediate failures that lead to
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// excessive CPU consumption.
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try {
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Thread.sleep(1000);
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} catch (InterruptedException e) {
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// Ignore.
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}
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}
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}
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2012-05-26 00:51:22 +02:00
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}
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2012-08-10 13:17:18 +02:00
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@Override
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protected void cleanup() {
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try {
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selector.close();
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} catch (IOException e) {
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logger.warn(
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"Failed to close a selector.", e);
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}
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}
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void cancel(SelectionKey key) {
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key.cancel();
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cancelledKeys ++;
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if (cancelledKeys >= CLEANUP_INTERVAL) {
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cancelledKeys = 0;
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cleanedCancelledKeys = true;
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SelectorUtil.cleanupKeys(selector);
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}
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}
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private void processSelectedKeys() {
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Set<SelectionKey> selectedKeys = selector.selectedKeys();
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if (selectedKeys.isEmpty()) {
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return;
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}
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Iterator<SelectionKey> i;
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cleanedCancelledKeys = false;
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boolean clearSelectedKeys = true;
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try {
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for (i = selectedKeys.iterator(); i.hasNext();) {
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final SelectionKey k = i.next();
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final AbstractNioChannel ch = (AbstractNioChannel) k.attachment();
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final NioUnsafe unsafe = ch.unsafe();
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try {
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int readyOps = k.readyOps();
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if ((readyOps & (SelectionKey.OP_READ | SelectionKey.OP_ACCEPT)) != 0 || readyOps == 0) {
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unsafe.read();
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if (!ch.isOpen()) {
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// Connection already closed - no need to handle write.
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continue;
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}
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}
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if ((readyOps & SelectionKey.OP_WRITE) != 0) {
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unsafe.flushNow();
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}
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if ((readyOps & SelectionKey.OP_CONNECT) != 0) {
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unsafe.finishConnect();
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}
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} catch (CancelledKeyException ignored) {
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unsafe.close(unsafe.voidFuture());
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}
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if (cleanedCancelledKeys) {
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// Create the iterator again to avoid ConcurrentModificationException
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if (selectedKeys.isEmpty()) {
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clearSelectedKeys = false;
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break;
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} else {
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i = selectedKeys.iterator();
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}
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}
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}
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} finally {
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if (clearSelectedKeys) {
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selectedKeys.clear();
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}
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}
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}
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private void closeAll() {
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SelectorUtil.cleanupKeys(selector);
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Set<SelectionKey> keys = selector.keys();
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Collection<Channel> channels = new ArrayList<Channel>(keys.size());
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for (SelectionKey k: keys) {
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channels.add((Channel) k.attachment());
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}
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for (Channel ch: channels) {
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ch.unsafe().close(ch.unsafe().voidFuture());
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}
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2012-06-02 02:51:19 +02:00
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}
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2012-05-26 00:51:22 +02:00
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2012-06-02 02:51:19 +02:00
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@Override
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2012-08-10 13:17:18 +02:00
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protected void wakeup(boolean inEventLoop) {
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if (wakenUp.compareAndSet(false, true)) {
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selector.wakeup();
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}
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2012-05-26 00:51:22 +02:00
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}
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}
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