/*
* Copyright 2012 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.channel.nio;
import io.netty.channel.AbstractChannel;
import io.netty.channel.Channel;
import io.netty.channel.ChannelException;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelPromise;
import io.netty.channel.ConnectTimeoutException;
import io.netty.channel.EventLoop;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
import java.io.IOException;
import java.net.ConnectException;
import java.net.SocketAddress;
import java.nio.channels.CancelledKeyException;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
/**
* Abstract base class for {@link Channel} implementations which use a Selector based approach.
*/
public abstract class AbstractNioChannel extends AbstractChannel {
private static final InternalLogger logger =
InternalLoggerFactory.getInstance(AbstractNioChannel.class);
//真正底层通信的java nio的Channel,它可能是一个ServerSocketChannel也可能是一个SocketChannel
private final SelectableChannel ch;
protected final int readInterestOp; //当前channel注册到selector时感兴趣的key值，在这里NioServerSocketChannel设置的是OP_ACCEPT
private volatile SelectionKey selectionKey;
private volatile boolean inputShutdown;
/**
* The future of the current connection attempt. If not null, subsequent
* connection attempts will fail.
*/
private ChannelPromise connectPromise;
private ScheduledFuture<?> connectTimeoutFuture;
private SocketAddress requestedRemoteAddress;
/**
* Create a new instance
*
* @param parent the parent {@link Channel} by which this instance was created. May be {@code null}
* @param ch the underlying {@link SelectableChannel} on which it operates
* @param readInterestOp the ops to set to receive data from the {@link SelectableChannel}
*/
protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {
super(parent);
this.ch = ch;
this.readInterestOp = readInterestOp;
try {
ch.configureBlocking(false);
} catch (IOException e) {
try {
ch.close();
} catch (IOException e2) {
if (logger.isWarnEnabled()) {
logger.warn(
"Failed to close a partially initialized socket.", e2);
}
}
throw new ChannelException("Failed to enter non-blocking mode.", e);
}
}
@Override
public boolean isOpen() {
return ch.isOpen();
}
@Override
public NioUnsafe unsafe() {
return (NioUnsafe) super.unsafe();
}
protected SelectableChannel javaChannel() {
return ch;
}
@Override
public NioEventLoop eventLoop() {
return (NioEventLoop) super.eventLoop();
}
/**
* Return the current {@link SelectionKey}
*/
protected SelectionKey selectionKey() {
assert selectionKey != null;
return selectionKey;
}
/**
* Return {@code true} if the input of this {@link Channel} is shutdown
*/
protected boolean isInputShutdown() {
return inputShutdown;
}
/**
* Shutdown the input of this {@link Channel}.
*/
void setInputShutdown() {
inputShutdown = true;
}
/**
* Special {@link Unsafe} sub-type which allows to access the underlying {@link SelectableChannel}
*/
public interface NioUnsafe extends Unsafe {
/**
* Return underlying {@link SelectableChannel}
*/
SelectableChannel ch();
/**
* Finish connect
*/
void finishConnect();
/**
* Read from underlying {@link SelectableChannel}
*/
void read();
void forceFlush();
}
/**
* Unsafe是真正channel完成bind,connect,read,write等任务的接口，这里有一个默认实现的抽象类AbstractNioUnsafe，其
* 与NIO的实现有两个子类：
* NioByteUnsafe: 主要负责NioSocketChannel的相关操作
* NioMessageUnsafe: 主要负责NioServerSocketChannel相关的操作
*/
protected abstract class AbstractNioUnsafe extends AbstractUnsafe implements NioUnsafe {
@Override
public SelectableChannel ch() {
return javaChannel();
}
@Override
public void connect(
final SocketAddress remoteAddress, final SocketAddress localAddress, final ChannelPromise promise) {
if (!ensureOpen(promise)) {
return;
}
try {
if (connectPromise != null) {
throw new IllegalStateException("connection attempt already made");
}
boolean wasActive = isActive();
if (doConnect(remoteAddress, localAddress)) {
fulfillConnectPromise(promise, wasActive);
} else {
connectPromise = promise;
requestedRemoteAddress = remoteAddress;
// Schedule connect timeout.
int connectTimeoutMillis = config().getConnectTimeoutMillis();
if (connectTimeoutMillis > 0) {
connectTimeoutFuture = eventLoop().schedule(new Runnable() {
@Override
public void run() {
ChannelPromise connectPromise = AbstractNioChannel.this.connectPromise;
ConnectTimeoutException cause =
new ConnectTimeoutException("connection timed out: " + remoteAddress);
if (connectPromise != null && connectPromise.tryFailure(cause)) {
close(voidPromise());
}
}
}, connectTimeoutMillis, TimeUnit.MILLISECONDS);
}
promise.addListener(new ChannelFutureListener() {
@Override
public void operationComplete(ChannelFuture future) throws Exception {
if (future.isCancelled()) {
if (connectTimeoutFuture != null) {
connectTimeoutFuture.cancel(false);
}
connectPromise = null;
close(voidPromise());
}
}
});
}
} catch (Throwable t) {
if (t instanceof ConnectException) {
Throwable newT = new ConnectException(t.getMessage() + ": " + remoteAddress);
newT.setStackTrace(t.getStackTrace());
t = newT;
}
promise.tryFailure(t);
closeIfClosed();
}
}
private void fulfillConnectPromise(ChannelPromise promise, boolean wasActive) {
// trySuccess() will return false if a user cancelled the connection attempt.
boolean promiseSet = promise.trySuccess();
// Regardless if the connection attempt was cancelled, channelActive() event should be triggered,
// because what happened is what happened.
if (!wasActive && isActive()) {
pipeline().fireChannelActive();
}
// If a user cancelled the connection attempt, close the channel, which is followed by channelInactive().
if (!promiseSet) {
close(voidPromise());
}
}
@Override
public void finishConnect() {
// Note this method is invoked by the event loop only if the connection attempt was
// neither cancelled nor timed out.
assert eventLoop().inEventLoop();
assert connectPromise != null;
try {
boolean wasActive = isActive();
doFinishConnect();
fulfillConnectPromise(connectPromise, wasActive);
} catch (Throwable t) {
if (t instanceof ConnectException) {
Throwable newT = new ConnectException(t.getMessage() + ": " + requestedRemoteAddress);
newT.setStackTrace(t.getStackTrace());
t = newT;
}
// Use tryFailure() instead of setFailure() to avoid the race against cancel().
connectPromise.tryFailure(t);
closeIfClosed();
} finally {
// Check for null as the connectTimeoutFuture is only created if a connectTimeoutMillis > 0 is used
// See https://github.com/netty/netty/issues/1770
if (connectTimeoutFuture != null) {
connectTimeoutFuture.cancel(false);
}
connectPromise = null;
}
}
@Override
protected void flush0() {
// Flush immediately only when there's no pending flush.
// If there's a pending flush operation, event loop will call forceFlush() later,
// and thus there's no need to call it now.
if (isFlushPending()) {
return;
}
super.flush0();
}
@Override
public void forceFlush() {
// directly call super.flush0() to force a flush now
super.flush0();
}
private boolean isFlushPending() {
SelectionKey selectionKey = selectionKey();
return selectionKey.isValid() && (selectionKey.interestOps() & SelectionKey.OP_WRITE) != 0;
}
}
@Override
protected boolean isCompatible(EventLoop loop) {
return loop instanceof NioEventLoop;
}
@Override
protected void doRegister() throws Exception {
boolean selected = false;
for (; ; ) {
try {
selectionKey = javaChannel().register(eventLoop().selector, 0, this);
return;
} catch (CancelledKeyException e) {
/**
* CancelledKeyException抛出的场景：
* 当前Channel已经注册了给定的selector,但是相应个key却已经被取消了
*/
if (!selected) {
// Force the Selector to select now as the "canceled" SelectionKey may still be
// cached and not removed because no Select.select(..) operation was called yet.
eventLoop().selectNow();
selected = true;
} else {
// We forced a select operation on the selector before but the SelectionKey is still cached
// for whatever reason. JDK bug ?
throw e;
}
}
}
}
@Override
protected void doDeregister() throws Exception {
eventLoop().cancel(selectionKey());
}
//给Channel的selectionKey增加OP_READ
@Override
protected void doBeginRead() throws Exception {
if (inputShutdown) {
return;
}
final SelectionKey selectionKey = this.selectionKey;
if (!selectionKey.isValid()) {
return;
}
final int interestOps = selectionKey.interestOps();
if ((interestOps & readInterestOp) == 0) {
selectionKey.interestOps(interestOps | readInterestOp);
}
}
/**
* Connect to the remote peer
*/
protected abstract boolean doConnect(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception;
/**
* Finish the connect
*/
protected abstract void doFinishConnect() throws Exception;
}