• Netty(四):AbstractChannel源码解析


    首先我们通过一张继承关系的图来认识下AbstractChannel在Netty中的位置。

    除了Comaprable接口来自java自带的包,其他都是Netty包中提供的。

    Comparable接口定义了Channel是可以比较的。

    AttributeMap接口为Channel提供了绑定其他属性的能力。

    这两个接口我们先不去深入了解,主要看ChannelOutboundInvoker。

    ChannelOutboundInvoker接口主要提供了与网络链路相关的一些操作以及读写相关的操作,并统一返回了ChannelFuture对象,便于我们可以监听这些操作是否成功。

    Channel接口继承了ChannelOutboundInvoker,在接口内部定义了Unsafe接口,增加了一部分方法,一些方法用来判断通道状态,一些方法用来绑定EventLoop,Pipeline和Unsafe对象。

    接下来看AbstractChannel的源码:

       1 /*
       2  * Copyright 2012 The Netty Project
       3  *
       4  * The Netty Project licenses this file to you under the Apache License,
       5  * version 2.0 (the "License"); you may not use this file except in compliance
       6  * with the License. You may obtain a copy of the License at:
       7  *
       8  *   http://www.apache.org/licenses/LICENSE-2.0
       9  *
      10  * Unless required by applicable law or agreed to in writing, software
      11  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
      12  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
      13  * License for the specific language governing permissions and limitations
      14  * under the License.
      15  */
      16 package io.netty.channel;
      17 
      18 import io.netty.buffer.ByteBufAllocator;
      19 import io.netty.channel.socket.ChannelOutputShutdownEvent;
      20 import io.netty.channel.socket.ChannelOutputShutdownException;
      21 import io.netty.util.DefaultAttributeMap;
      22 import io.netty.util.ReferenceCountUtil;
      23 import io.netty.util.internal.PlatformDependent;
      24 import io.netty.util.internal.ThrowableUtil;
      25 import io.netty.util.internal.UnstableApi;
      26 import io.netty.util.internal.logging.InternalLogger;
      27 import io.netty.util.internal.logging.InternalLoggerFactory;
      28 
      29 import java.io.IOException;
      30 import java.net.ConnectException;
      31 import java.net.InetSocketAddress;
      32 import java.net.NoRouteToHostException;
      33 import java.net.SocketAddress;
      34 import java.net.SocketException;
      35 import java.nio.channels.ClosedChannelException;
      36 import java.nio.channels.NotYetConnectedException;
      37 import java.util.concurrent.Executor;
      38 import java.util.concurrent.RejectedExecutionException;
      39 
      40 /**
      41  * A skeletal {@link Channel} implementation.
      42  */
      43 public abstract class AbstractChannel extends DefaultAttributeMap implements Channel {
      44 
      45     private static final InternalLogger logger = InternalLoggerFactory.getInstance(AbstractChannel.class);
      46 
      47     private static final ClosedChannelException FLUSH0_CLOSED_CHANNEL_EXCEPTION = ThrowableUtil.unknownStackTrace(
      48             new ClosedChannelException(), AbstractUnsafe.class, "flush0()");
      49     private static final ClosedChannelException ENSURE_OPEN_CLOSED_CHANNEL_EXCEPTION = ThrowableUtil.unknownStackTrace(
      50             new ClosedChannelException(), AbstractUnsafe.class, "ensureOpen(...)");
      51     private static final ClosedChannelException CLOSE_CLOSED_CHANNEL_EXCEPTION = ThrowableUtil.unknownStackTrace(
      52             new ClosedChannelException(), AbstractUnsafe.class, "close(...)");
      53     private static final ClosedChannelException WRITE_CLOSED_CHANNEL_EXCEPTION = ThrowableUtil.unknownStackTrace(
      54             new ClosedChannelException(), AbstractUnsafe.class, "write(...)");
      55     private static final NotYetConnectedException FLUSH0_NOT_YET_CONNECTED_EXCEPTION = ThrowableUtil.unknownStackTrace(
      56             new NotYetConnectedException(), AbstractUnsafe.class, "flush0()");
      57 
      58     //父Channel
      59     private final Channel parent;
      60     private final ChannelId id;
      61     //Unsafe对象,封装ByteBuf的读写过程
      62     private final Unsafe unsafe;
      63     //关联的Pipeline对象
      64     private final DefaultChannelPipeline pipeline;
      65 
      66     private final VoidChannelPromise unsafeVoidPromise = new VoidChannelPromise(this, false);
      67     private final CloseFuture closeFuture = new CloseFuture(this);
      68 
      69     //本地地址和远端地址
      70     private volatile SocketAddress localAddress;
      71     private volatile SocketAddress remoteAddress;
      72 
      73     //用来处理读写的线程
      74     private volatile EventLoop eventLoop;
      75 
      76     private volatile boolean registered;
      77     private boolean closeInitiated;
      78 
      79     /** Cache for the string representation of this channel */
      80     private boolean strValActive;
      81     private String strVal;
      82 
      83     /**
      84      * Creates a new instance.
      85      *
      86      * @param parent
      87      *        the parent of this channel. {@code null} if there's no parent.
      88      */
      89     protected AbstractChannel(Channel parent) {
      90         this.parent = parent;
      91         id = newId();
      92         unsafe = newUnsafe();
      93         pipeline = newChannelPipeline();
      94     }
      95 
      96     /**
      97      * Creates a new instance.
      98      *
      99      * @param parent
     100      *        the parent of this channel. {@code null} if there's no parent.
     101      */
     102     protected AbstractChannel(Channel parent, ChannelId id) {
     103         this.parent = parent;
     104         this.id = id;
     105         unsafe = newUnsafe();
     106         pipeline = newChannelPipeline();
     107     }
     108 
     109     @Override
     110     public final ChannelId id() {
     111         return id;
     112     }
     113 
     114     /**
     115      * Returns a new {@link DefaultChannelId} instance. Subclasses may override this method to assign custom
     116      * {@link ChannelId}s to {@link Channel}s that use the {@link AbstractChannel#AbstractChannel(Channel)} constructor.
     117      */
     118     protected ChannelId newId() {
     119         return DefaultChannelId.newInstance();
     120     }
     121 
     122     /**
     123      * Returns a new {@link DefaultChannelPipeline} instance.
     124      */
     125     protected DefaultChannelPipeline newChannelPipeline() {
     126         return new DefaultChannelPipeline(this);
     127     }
     128 
     129     //通道是否可写
     130     @Override
     131     public boolean isWritable() {
     132         //是否存在输出缓冲区且缓冲区可写
     133         ChannelOutboundBuffer buf = unsafe.outboundBuffer();
     134         return buf != null && buf.isWritable();
     135     }
     136 
     137     //获取剩余可写空间
     138     @Override
     139     public long bytesBeforeUnwritable() {
     140         ChannelOutboundBuffer buf = unsafe.outboundBuffer();
     141         // isWritable() is currently assuming if there is no outboundBuffer then the channel is not writable.
     142         // We should be consistent with that here.
     143         return buf != null ? buf.bytesBeforeUnwritable() : 0;
     144     }
     145 
     146     //还需处理多少字节才可写
     147     @Override
     148     public long bytesBeforeWritable() {
     149         ChannelOutboundBuffer buf = unsafe.outboundBuffer();
     150         // isWritable() is currently assuming if there is no outboundBuffer then the channel is not writable.
     151         // We should be consistent with that here.
     152         return buf != null ? buf.bytesBeforeWritable() : Long.MAX_VALUE;
     153     }
     154 
     155     @Override
     156     public Channel parent() {
     157         return parent;
     158     }
     159 
     160     @Override
     161     public ChannelPipeline pipeline() {
     162         return pipeline;
     163     }
     164 
     165     @Override
     166     public ByteBufAllocator alloc() {
     167         return config().getAllocator();
     168     }
     169 
     170     @Override
     171     public EventLoop eventLoop() {
     172         EventLoop eventLoop = this.eventLoop;
     173         if (eventLoop == null) {
     174             throw new IllegalStateException("channel not registered to an event loop");
     175         }
     176         return eventLoop;
     177     }
     178 
     179     @Override
     180     public SocketAddress localAddress() {
     181         SocketAddress localAddress = this.localAddress;
     182         if (localAddress == null) {
     183             try {
     184                 this.localAddress = localAddress = unsafe().localAddress();
     185             } catch (Throwable t) {
     186                 // Sometimes fails on a closed socket in Windows.
     187                 return null;
     188             }
     189         }
     190         return localAddress;
     191     }
     192 
     193     /**
     194      * @deprecated no use-case for this.
     195      */
     196     @Deprecated
     197     protected void invalidateLocalAddress() {
     198         localAddress = null;
     199     }
     200 
     201     //获取远端地址
     202     @Override
     203     public SocketAddress remoteAddress() {
     204         SocketAddress remoteAddress = this.remoteAddress;
     205         if (remoteAddress == null) {
     206             try {
     207                 this.remoteAddress = remoteAddress = unsafe().remoteAddress();
     208             } catch (Throwable t) {
     209                 // Sometimes fails on a closed socket in Windows.
     210                 return null;
     211             }
     212         }
     213         return remoteAddress;
     214     }
     215 
     216     /**
     217      * @deprecated no use-case for this.
     218      */
     219     @Deprecated
     220     protected void invalidateRemoteAddress() {
     221         remoteAddress = null;
     222     }
     223 
     224     //是否已经注册
     225     @Override
     226     public boolean isRegistered() {
     227         return registered;
     228     }
     229 
     230     /******* ChannelOutboundInvoker接口中的方法都交给pipeline对象代理********/
     231     @Override
     232     public ChannelFuture bind(SocketAddress localAddress) {
     233         return pipeline.bind(localAddress);
     234     }
     235 
     236     @Override
     237     public ChannelFuture connect(SocketAddress remoteAddress) {
     238         return pipeline.connect(remoteAddress);
     239     }
     240 
     241     @Override
     242     public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress) {
     243         return pipeline.connect(remoteAddress, localAddress);
     244     }
     245 
     246     @Override
     247     public ChannelFuture disconnect() {
     248         return pipeline.disconnect();
     249     }
     250 
     251     @Override
     252     public ChannelFuture close() {
     253         return pipeline.close();
     254     }
     255 
     256     @Override
     257     public ChannelFuture deregister() {
     258         return pipeline.deregister();
     259     }
     260 
     261     @Override
     262     public Channel flush() {
     263         pipeline.flush();
     264         return this;
     265     }
     266 
     267     @Override
     268     public ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise) {
     269         return pipeline.bind(localAddress, promise);
     270     }
     271 
     272     @Override
     273     public ChannelFuture connect(SocketAddress remoteAddress, ChannelPromise promise) {
     274         return pipeline.connect(remoteAddress, promise);
     275     }
     276 
     277     @Override
     278     public ChannelFuture connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {
     279         return pipeline.connect(remoteAddress, localAddress, promise);
     280     }
     281 
     282     @Override
     283     public ChannelFuture disconnect(ChannelPromise promise) {
     284         return pipeline.disconnect(promise);
     285     }
     286 
     287     @Override
     288     public ChannelFuture close(ChannelPromise promise) {
     289         return pipeline.close(promise);
     290     }
     291 
     292     @Override
     293     public ChannelFuture deregister(ChannelPromise promise) {
     294         return pipeline.deregister(promise);
     295     }
     296 
     297     @Override
     298     public Channel read() {
     299         pipeline.read();
     300         return this;
     301     }
     302 
     303     @Override
     304     public ChannelFuture write(Object msg) {
     305         return pipeline.write(msg);
     306     }
     307 
     308     @Override
     309     public ChannelFuture write(Object msg, ChannelPromise promise) {
     310         return pipeline.write(msg, promise);
     311     }
     312 
     313     @Override
     314     public ChannelFuture writeAndFlush(Object msg) {
     315         return pipeline.writeAndFlush(msg);
     316     }
     317 
     318     @Override
     319     public ChannelFuture writeAndFlush(Object msg, ChannelPromise promise) {
     320         return pipeline.writeAndFlush(msg, promise);
     321     }
     322 
     323     @Override
     324     public ChannelPromise newPromise() {
     325         return pipeline.newPromise();
     326     }
     327 
     328     @Override
     329     public ChannelProgressivePromise newProgressivePromise() {
     330         return pipeline.newProgressivePromise();
     331     }
     332 
     333     @Override
     334     public ChannelFuture newSucceededFuture() {
     335         return pipeline.newSucceededFuture();
     336     }
     337 
     338     @Override
     339     public ChannelFuture newFailedFuture(Throwable cause) {
     340         return pipeline.newFailedFuture(cause);
     341     }
     342 
     343     /**************ChannelOutboundInvoker接口*************/
     344 
     345     //返回ChannelFuture
     346     @Override
     347     public ChannelFuture closeFuture() {
     348         return closeFuture;
     349     }
     350 
     351     //返回UnSafe对象
     352     @Override
     353     public Unsafe unsafe() {
     354         return unsafe;
     355     }
     356 
     357     /**
     358      * Create a new {@link AbstractUnsafe} instance which will be used for the life-time of the {@link Channel}
     359      */
     360     //抽象方法 具体获取Unsafe的方式交给子类实现,
     361     protected abstract AbstractUnsafe newUnsafe();
     362 
     363     /**
     364      * Returns the ID of this channel.
     365      */
     366     @Override
     367     public final int hashCode() {
     368         return id.hashCode();
     369     }
     370 
     371     /**
     372      * Returns {@code true} if and only if the specified object is identical
     373      * with this channel (i.e: {@code this == o}).
     374      */
     375     @Override
     376     public final boolean equals(Object o) {
     377         return this == o;
     378     }
     379 
     380     @Override
     381     public final int compareTo(Channel o) {
     382         if (this == o) {
     383             return 0;
     384         }
     385 
     386         return id().compareTo(o.id());
     387     }
     388 
     389     /**
     390      * Returns the {@link String} representation of this channel.  The returned
     391      * string contains the {@linkplain #hashCode() ID}, {@linkplain #localAddress() local address},
     392      * and {@linkplain #remoteAddress() remote address} of this channel for
     393      * easier identification.
     394      */
     395     @Override
     396     public String toString() {
     397         boolean active = isActive();
     398         if (strValActive == active && strVal != null) {
     399             return strVal;
     400         }
     401 
     402         SocketAddress remoteAddr = remoteAddress();
     403         SocketAddress localAddr = localAddress();
     404         if (remoteAddr != null) {
     405             StringBuilder buf = new StringBuilder(96)
     406                 .append("[id: 0x")
     407                 .append(id.asShortText())
     408                 .append(", L:")
     409                 .append(localAddr)
     410                 .append(active? " - " : " ! ")
     411                 .append("R:")
     412                 .append(remoteAddr)
     413                 .append(']');
     414             strVal = buf.toString();
     415         } else if (localAddr != null) {
     416             StringBuilder buf = new StringBuilder(64)
     417                 .append("[id: 0x")
     418                 .append(id.asShortText())
     419                 .append(", L:")
     420                 .append(localAddr)
     421                 .append(']');
     422             strVal = buf.toString();
     423         } else {
     424             StringBuilder buf = new StringBuilder(16)
     425                 .append("[id: 0x")
     426                 .append(id.asShortText())
     427                 .append(']');
     428             strVal = buf.toString();
     429         }
     430 
     431         strValActive = active;
     432         return strVal;
     433     }
     434 
     435     @Override
     436     public final ChannelPromise voidPromise() {
     437         return pipeline.voidPromise();
     438     }
     439 
     440     /**
     441      * {@link Unsafe} implementation which sub-classes must extend and use.
     442      */
     443     //Unsafe的抽象实现,虽然是抽象类,但没有抽象的方法,只是对某些方法提供了空实现;一些方法的关键实现是交给AbstractChannel的特定子类
     444     protected abstract class AbstractUnsafe implements Unsafe {
     445 
     446         private volatile ChannelOutboundBuffer outboundBuffer = new ChannelOutboundBuffer(AbstractChannel.this);
     447         private RecvByteBufAllocator.Handle recvHandle;
     448         private boolean inFlush0;
     449         /** true if the channel has never been registered, false otherwise */
     450         private boolean neverRegistered = true;
     451 
     452         private void assertEventLoop() {
     453             assert !registered || eventLoop.inEventLoop();
     454         }
     455 
     456         @Override
     457         public RecvByteBufAllocator.Handle recvBufAllocHandle() {
     458             if (recvHandle == null) {
     459                 recvHandle = config().getRecvByteBufAllocator().newHandle();
     460             }
     461             return recvHandle;
     462         }
     463 
     464         @Override
     465         public final ChannelOutboundBuffer outboundBuffer() {
     466             return outboundBuffer;
     467         }
     468 
     469         @Override
     470         public final SocketAddress localAddress() {
     471             return localAddress0();
     472         }
     473 
     474         @Override
     475         public final SocketAddress remoteAddress() {
     476             return remoteAddress0();
     477         }
     478 
     479         //注册;将Unsafe与EventLoop绑定
     480         @Override
     481         public final void register(EventLoop eventLoop, final ChannelPromise promise) {
     482             if (eventLoop == null) {
     483                 throw new NullPointerException("eventLoop");
     484             }
     485             if (isRegistered()) {
     486                 promise.setFailure(new IllegalStateException("registered to an event loop already"));
     487                 return;
     488             }
     489             if (!isCompatible(eventLoop)) {
     490                 promise.setFailure(
     491                         new IllegalStateException("incompatible event loop type: " + eventLoop.getClass().getName()));
     492                 return;
     493             }
     494 
     495             AbstractChannel.this.eventLoop = eventLoop;
     496 
     497             if (eventLoop.inEventLoop()) {
     498                 //如果当前线程是处理线程,直接注册
     499                 register0(promise);
     500             } else {
     501                 //如果当前线程不是处理线程,则包装成任务丢给eventLoop处理
     502                 try {
     503                     eventLoop.execute(new Runnable() {
     504                         @Override
     505                         public void run() {
     506                             register0(promise);
     507                         }
     508                     });
     509                 } catch (Throwable t) {
     510                     logger.warn(
     511                             "Force-closing a channel whose registration task was not accepted by an event loop: {}",
     512                             AbstractChannel.this, t);
     513                     closeForcibly();
     514                     closeFuture.setClosed();
     515                     safeSetFailure(promise, t);
     516                 }
     517             }
     518         }
     519 
     520         private void register0(ChannelPromise promise) {
     521             try {
     522                 // check if the channel is still open as it could be closed in the mean time when the register
     523                 // call was outside of the eventLoop
     524                 //确认Channel仍然打开
     525                 if (!promise.setUncancellable() || !ensureOpen(promise)) {
     526                     return;
     527                 }
     528 
     529                 boolean firstRegistration = neverRegistered;
     530                 //注册具体流程
     531                 doRegister();
     532                 //修改注册状态
     533                 neverRegistered = false;
     534                 registered = true;
     535 
     536                 // Ensure we call handlerAdded(...) before we actually notify the promise. This is needed as the
     537                 // user may already fire events through the pipeline in the ChannelFutureListener.
     538                 //产生HandlerAdded
     539                 pipeline.invokeHandlerAddedIfNeeded();
     540 
     541                 safeSetSuccess(promise);
     542                 //注册成功,产生注册事件
     543                 pipeline.fireChannelRegistered();
     544                 
     545                 //激活成功
     546                 if (isActive()) {
     547                     //首次注册,产生active事件
     548                     if (firstRegistration) {
     549                         pipeline.fireChannelActive();
     550                     } else if (config().isAutoRead()) {
     551                         //如果重注册且配置了自动读
     552                         // This channel was registered before and autoRead() is set. This means we need to begin read
     553                         // again so that we process inbound data.
     554                         //
     555                         // See https://github.com/netty/netty/issues/4805
     556                         beginRead();
     557                     }
     558                 }
     559             } catch (Throwable t) {
     560                 // Close the channel directly to avoid FD leak.
     561                 closeForcibly();
     562                 closeFuture.setClosed();
     563                 safeSetFailure(promise, t);
     564             }
     565         }
     566 
     567         //绑定
     568         @Override
     569         public final void bind(final SocketAddress localAddress, final ChannelPromise promise) {
     570             assertEventLoop();
     571 
     572             if (!promise.setUncancellable() || !ensureOpen(promise)) {
     573                 return;
     574             }
     575 
     576             // See: https://github.com/netty/netty/issues/576
     577             if (Boolean.TRUE.equals(config().getOption(ChannelOption.SO_BROADCAST)) &&
     578                 localAddress instanceof InetSocketAddress &&
     579                 !((InetSocketAddress) localAddress).getAddress().isAnyLocalAddress() &&
     580                 !PlatformDependent.isWindows() && !PlatformDependent.maybeSuperUser()) {
     581                 // Warn a user about the fact that a non-root user can't receive a
     582                 // broadcast packet on *nix if the socket is bound on non-wildcard address.
     583                 logger.warn(
     584                         "A non-root user can't receive a broadcast packet if the socket " +
     585                         "is not bound to a wildcard address; binding to a non-wildcard " +
     586                         "address (" + localAddress + ") anyway as requested.");
     587             }
     588 
     589             boolean wasActive = isActive();
     590             try {
     591                 //具体绑定流程
     592                 doBind(localAddress);
     593             } catch (Throwable t) {
     594                 safeSetFailure(promise, t);
     595                 closeIfClosed();
     596                 return;
     597             }
     598             //绑定成功,产生Active事件
     599             if (!wasActive && isActive()) {
     600                 invokeLater(new Runnable() {
     601                     @Override
     602                     public void run() {
     603                         pipeline.fireChannelActive();
     604                     }
     605                 });
     606             }
     607             //将Promis设置为成功
     608             safeSetSuccess(promise);
     609         }
     610 
     611         //断开连接
     612         @Override
     613         public final void disconnect(final ChannelPromise promise) {
     614             assertEventLoop();
     615 
     616             if (!promise.setUncancellable()) {
     617                 return;
     618             }
     619 
     620             boolean wasActive = isActive();
     621             try {
     622                 //断开具体流程
     623                 doDisconnect();
     624             } catch (Throwable t) {
     625                 safeSetFailure(promise, t);
     626                 closeIfClosed();
     627                 return;
     628             }
     629 
     630             //断开成功,产生Inactive事件
     631             if (wasActive && !isActive()) {
     632                 invokeLater(new Runnable() {
     633                     @Override
     634                     public void run() {
     635                         pipeline.fireChannelInactive();
     636                     }
     637                 });
     638             }
     639 
     640             safeSetSuccess(promise);
     641             closeIfClosed(); // doDisconnect() might have closed the channel
     642         }
     643 
     644         @Override
     645         public final void close(final ChannelPromise promise) {
     646             assertEventLoop();
     647 
     648             close(promise, CLOSE_CLOSED_CHANNEL_EXCEPTION, CLOSE_CLOSED_CHANNEL_EXCEPTION, false);
     649         }
     650 
     651         /**
     652          * Shutdown the output portion of the corresponding {@link Channel}.
     653          * For example this will clean up the {@link ChannelOutboundBuffer} and not allow any more writes.
     654          */
     655         @UnstableApi
     656         public final void shutdownOutput(final ChannelPromise promise) {
     657             assertEventLoop();
     658             shutdownOutput(promise, null);
     659         }
     660 
     661         /**
     662          * Shutdown the output portion of the corresponding {@link Channel}.
     663          * For example this will clean up the {@link ChannelOutboundBuffer} and not allow any more writes.
     664          * @param cause The cause which may provide rational for the shutdown.
     665          */
     666         private void shutdownOutput(final ChannelPromise promise, Throwable cause) {
     667             if (!promise.setUncancellable()) {
     668                 return;
     669             }
     670 
     671             final ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;
     672             //如果不存在输出缓冲区,设置Promise为失败,抛出已关闭异常
     673             if (  == null) {
     674                 promise.setFailure(CLOSE_CLOSED_CHANNEL_EXCEPTION);
     675                 return;
     676             }
     677             
     678             this.outboundBuffer = null; // Disallow adding any messages and flushes to outboundBuffer.
     679 
     680             //线程关闭原因
     681             final Throwable shutdownCause = cause == null ?
     682                     new ChannelOutputShutdownException("Channel output shutdown") :
     683                     new ChannelOutputShutdownException("Channel output shutdown", cause);
     684             Executor closeExecutor = prepareToClose();
     685             if (closeExecutor != null) {
     686                 closeExecutor.execute(new Runnable() {
     687                     @Override
     688                     public void run() {
     689                         try {
     690                             //关闭流程
     691                             doShutdownOutput();
     692                             promise.setSuccess();
     693                         } catch (Throwable err) {
     694                             promise.setFailure(err);
     695                         } finally {
     696                             // Dispatch to the EventLoop
     697                             eventLoop().execute(new Runnable() {
     698                                 @Override
     699                                 public void run() {
     700                                     closeOutboundBufferForShutdown(pipeline, outboundBuffer, shutdownCause);
     701                                 }
     702                             });
     703                         }
     704                     }
     705                 });
     706             } else {
     707                 try {
     708                     // Execute the shutdown.
     709                     doShutdownOutput();
     710                     promise.setSuccess();
     711                 } catch (Throwable err) {
     712                     promise.setFailure(err);
     713                 } finally {
     714                     closeOutboundBufferForShutdown(pipeline, outboundBuffer, shutdownCause);
     715                 }
     716             }
     717         }
     718 
     719         private void closeOutboundBufferForShutdown(
     720                 ChannelPipeline pipeline, ChannelOutboundBuffer buffer, Throwable cause) {
     721             buffer.failFlushed(cause, false);
     722             buffer.close(cause, true);
     723             pipeline.fireUserEventTriggered(ChannelOutputShutdownEvent.INSTANCE);
     724         }
     725 
     726         private void close(final ChannelPromise promise, final Throwable cause,
     727                            final ClosedChannelException closeCause, final boolean notify) {
     728             if (!promise.setUncancellable()) {
     729                 return;
     730             }
     731 
     732             if (closeInitiated) {
     733                 if (closeFuture.isDone()) {
     734                     // Closed already.
     735                     safeSetSuccess(promise);
     736                 } else if (!(promise instanceof VoidChannelPromise)) { // Only needed if no VoidChannelPromise.
     737                     // This means close() was called before so we just register a listener and return
     738                     closeFuture.addListener(new ChannelFutureListener() {
     739                         @Override
     740                         public void operationComplete(ChannelFuture future) throws Exception {
     741                             promise.setSuccess();
     742                         }
     743                     });
     744                 }
     745                 return;
     746             }
     747 
     748             closeInitiated = true;
     749 
     750             final boolean wasActive = isActive();
     751             final ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;
     752             this.outboundBuffer = null; // Disallow adding any messages and flushes to outboundBuffer.
     753             Executor closeExecutor = prepareToClose();
     754             if (closeExecutor != null) {
     755                 closeExecutor.execute(new Runnable() {
     756                     @Override
     757                     public void run() {
     758                         try {
     759                             // Execute the close.
     760                             doClose0(promise);
     761                         } finally {
     762                             // Call invokeLater so closeAndDeregister is executed in the EventLoop again!
     763                             invokeLater(new Runnable() {
     764                                 @Override
     765                                 public void run() {
     766                                     if (outboundBuffer != null) {
     767                                         // Fail all the queued messages
     768                                         outboundBuffer.failFlushed(cause, notify);
     769                                         outboundBuffer.close(closeCause);
     770                                     }
     771                                     fireChannelInactiveAndDeregister(wasActive);
     772                                 }
     773                             });
     774                         }
     775                     }
     776                 });
     777             } else {
     778                 try {
     779                     // Close the channel and fail the queued messages in all cases.
     780                     doClose0(promise);
     781                 } finally {
     782                     if (outboundBuffer != null) {
     783                         // Fail all the queued messages.
     784                         outboundBuffer.failFlushed(cause, notify);
     785                         outboundBuffer.close(closeCause);
     786                     }
     787                 }
     788                 if (inFlush0) {
     789                     invokeLater(new Runnable() {
     790                         @Override
     791                         public void run() {
     792                             fireChannelInactiveAndDeregister(wasActive);
     793                         }
     794                     });
     795                 } else {
     796                     fireChannelInactiveAndDeregister(wasActive);
     797                 }
     798             }
     799         }
     800 
     801         private void doClose0(ChannelPromise promise) {
     802             try {
     803                 doClose();
     804                 closeFuture.setClosed();
     805                 safeSetSuccess(promise);
     806             } catch (Throwable t) {
     807                 closeFuture.setClosed();
     808                 safeSetFailure(promise, t);
     809             }
     810         }
     811 
     812         private void fireChannelInactiveAndDeregister(final boolean wasActive) {
     813             deregister(voidPromise(), wasActive && !isActive());
     814         }
     815 
     816         @Override
     817         public final void closeForcibly() {
     818             assertEventLoop();
     819 
     820             try {
     821                 doClose();
     822             } catch (Exception e) {
     823                 logger.warn("Failed to close a channel.", e);
     824             }
     825         }
     826 
     827         @Override
     828         public final void deregister(final ChannelPromise promise) {
     829             assertEventLoop();
     830 
     831             deregister(promise, false);
     832         }
     833 
     834         private void deregister(final ChannelPromise promise, final boolean fireChannelInactive) {
     835             if (!promise.setUncancellable()) {
     836                 return;
     837             }
     838 
     839             if (!registered) {
     840                 safeSetSuccess(promise);
     841                 return;
     842             }
     843 
     844             // As a user may call deregister() from within any method while doing processing in the ChannelPipeline,
     845             // we need to ensure we do the actual deregister operation later. This is needed as for example,
     846             // we may be in the ByteToMessageDecoder.callDecode(...) method and so still try to do processing in
     847             // the old EventLoop while the user already registered the Channel to a new EventLoop. Without delay,
     848             // the deregister operation this could lead to have a handler invoked by different EventLoop and so
     849             // threads.
     850             //
     851             // See:
     852             // https://github.com/netty/netty/issues/4435
     853             invokeLater(new Runnable() {
     854                 @Override
     855                 public void run() {
     856                     try {
     857                         doDeregister();
     858                     } catch (Throwable t) {
     859                         logger.warn("Unexpected exception occurred while deregistering a channel.", t);
     860                     } finally {
     861                         if (fireChannelInactive) {
     862                             pipeline.fireChannelInactive();
     863                         }
     864                         // Some transports like local and AIO does not allow the deregistration of
     865                         // an open channel.  Their doDeregister() calls close(). Consequently,
     866                         // close() calls deregister() again - no need to fire channelUnregistered, so check
     867                         // if it was registered.
     868                         if (registered) {
     869                             registered = false;
     870                             pipeline.fireChannelUnregistered();
     871                         }
     872                         safeSetSuccess(promise);
     873                     }
     874                 }
     875             });
     876         }
     877 
     878         @Override
     879         public final void beginRead() {
     880             assertEventLoop();
     881 
     882             if (!isActive()) {
     883                 return;
     884             }
     885 
     886             try {
     887                 doBeginRead();
     888             } catch (final Exception e) {
     889                 invokeLater(new Runnable() {
     890                     @Override
     891                     public void run() {
     892                         pipeline.fireExceptionCaught(e);
     893                     }
     894                 });
     895                 close(voidPromise());
     896             }
     897         }
     898 
     899         @Override
     900         public final void write(Object msg, ChannelPromise promise) {
     901             assertEventLoop();
     902 
     903             ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;
     904             if (outboundBuffer == null) {
     905                 // If the outboundBuffer is null we know the channel was closed and so
     906                 // need to fail the future right away. If it is not null the handling of the rest
     907                 // will be done in flush0()
     908                 // See https://github.com/netty/netty/issues/2362
     909                 safeSetFailure(promise, WRITE_CLOSED_CHANNEL_EXCEPTION);
     910                 // release message now to prevent resource-leak
     911                 ReferenceCountUtil.release(msg);
     912                 return;
     913             }
     914 
     915             int size;
     916             try {
     917                 msg = filterOutboundMessage(msg);
     918                 size = pipeline.estimatorHandle().size(msg);
     919                 if (size < 0) {
     920                     size = 0;
     921                 }
     922             } catch (Throwable t) {
     923                 safeSetFailure(promise, t);
     924                 ReferenceCountUtil.release(msg);
     925                 return;
     926             }
     927 
     928             outboundBuffer.addMessage(msg, size, promise);
     929         }
     930 
     931         @Override
     932         public final void flush() {
     933             assertEventLoop();
     934 
     935             ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;
     936             if (outboundBuffer == null) {
     937                 return;
     938             }
     939 
     940             outboundBuffer.addFlush();
     941             flush0();
     942         }
     943 
     944         @SuppressWarnings("deprecation")
     945         protected void flush0() {
     946             if (inFlush0) {
     947                 // Avoid re-entrance
     948                 return;
     949             }
     950 
     951             final ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;
     952             if (outboundBuffer == null || outboundBuffer.isEmpty()) {
     953                 return;
     954             }
     955 
     956             inFlush0 = true;
     957 
     958             // Mark all pending write requests as failure if the channel is inactive.
     959             if (!isActive()) {
     960                 try {
     961                     if (isOpen()) {
     962                         outboundBuffer.failFlushed(FLUSH0_NOT_YET_CONNECTED_EXCEPTION, true);
     963                     } else {
     964                         // Do not trigger channelWritabilityChanged because the channel is closed already.
     965                         outboundBuffer.failFlushed(FLUSH0_CLOSED_CHANNEL_EXCEPTION, false);
     966                     }
     967                 } finally {
     968                     inFlush0 = false;
     969                 }
     970                 return;
     971             }
     972 
     973             try {
     974                 doWrite(outboundBuffer);
     975             } catch (Throwable t) {
     976                 if (t instanceof IOException && config().isAutoClose()) {
     977                     /**
     978                      * Just call {@link #close(ChannelPromise, Throwable, boolean)} here which will take care of
     979                      * failing all flushed messages and also ensure the actual close of the underlying transport
     980                      * will happen before the promises are notified.
     981                      *
     982                      * This is needed as otherwise {@link #isActive()} , {@link #isOpen()} and {@link #isWritable()}
     983                      * may still return {@code true} even if the channel should be closed as result of the exception.
     984                      */
     985                     close(voidPromise(), t, FLUSH0_CLOSED_CHANNEL_EXCEPTION, false);
     986                 } else {
     987                     try {
     988                         shutdownOutput(voidPromise(), t);
     989                     } catch (Throwable t2) {
     990                         close(voidPromise(), t2, FLUSH0_CLOSED_CHANNEL_EXCEPTION, false);
     991                     }
     992                 }
     993             } finally {
     994                 inFlush0 = false;
     995             }
     996         }
     997 
     998         @Override
     999         public final ChannelPromise voidPromise() {
    1000             assertEventLoop();
    1001 
    1002             return unsafeVoidPromise;
    1003         }
    1004 
    1005         protected final boolean ensureOpen(ChannelPromise promise) {
    1006             if (isOpen()) {
    1007                 return true;
    1008             }
    1009 
    1010             safeSetFailure(promise, ENSURE_OPEN_CLOSED_CHANNEL_EXCEPTION);
    1011             return false;
    1012         }
    1013 
    1014         /**
    1015          * Marks the specified {@code promise} as success.  If the {@code promise} is done already, log a message.
    1016          */
    1017         protected final void safeSetSuccess(ChannelPromise promise) {
    1018             if (!(promise instanceof VoidChannelPromise) && !promise.trySuccess()) {
    1019                 logger.warn("Failed to mark a promise as success because it is done already: {}", promise);
    1020             }
    1021         }
    1022 
    1023         /**
    1024          * Marks the specified {@code promise} as failure.  If the {@code promise} is done already, log a message.
    1025          */
    1026         protected final void safeSetFailure(ChannelPromise promise, Throwable cause) {
    1027             if (!(promise instanceof VoidChannelPromise) && !promise.tryFailure(cause)) {
    1028                 logger.warn("Failed to mark a promise as failure because it's done already: {}", promise, cause);
    1029             }
    1030         }
    1031 
    1032         protected final void closeIfClosed() {
    1033             if (isOpen()) {
    1034                 return;
    1035             }
    1036             close(voidPromise());
    1037         }
    1038 
    1039         //将任务提交给EventLoop执行
    1040         private void invokeLater(Runnable task) {
    1041             try {
    1042                 // This method is used by outbound operation implementations to trigger an inbound event later.
    1043                 // They do not trigger an inbound event immediately because an outbound operation might have been
    1044                 // triggered by another inbound event handler method.  If fired immediately, the call stack
    1045                 // will look like this for example:
    1046                 //
    1047                 //   handlerA.inboundBufferUpdated() - (1) an inbound handler method closes a connection.
    1048                 //   -> handlerA.ctx.close()
    1049                 //      -> channel.unsafe.close()
    1050                 //         -> handlerA.channelInactive() - (2) another inbound handler method called while in (1) yet
    1051                 //
    1052                 // which means the execution of two inbound handler methods of the same handler overlap undesirably.
    1053                 eventLoop().execute(task);
    1054             } catch (RejectedExecutionException e) {
    1055                 logger.warn("Can't invoke task later as EventLoop rejected it", e);
    1056             }
    1057         }
    1058 
    1059         /**
    1060          * Appends the remote address to the message of the exceptions caused by connection attempt failure.
    1061          */
    1062         protected final Throwable annotateConnectException(Throwable cause, SocketAddress remoteAddress) {
    1063             if (cause instanceof ConnectException) {
    1064                 return new AnnotatedConnectException((ConnectException) cause, remoteAddress);
    1065             }
    1066             if (cause instanceof NoRouteToHostException) {
    1067                 return new AnnotatedNoRouteToHostException((NoRouteToHostException) cause, remoteAddress);
    1068             }
    1069             if (cause instanceof SocketException) {
    1070                 return new AnnotatedSocketException((SocketException) cause, remoteAddress);
    1071             }
    1072 
    1073             return cause;
    1074         }
    1075 
    1076         /**
    1077          * Prepares to close the {@link Channel}. If this method returns an {@link Executor}, the
    1078          * caller must call the {@link Executor#execute(Runnable)} method with a task that calls
    1079          * {@link #doClose()} on the returned {@link Executor}. If this method returns {@code null},
    1080          * {@link #doClose()} must be called from the caller thread. (i.e. {@link EventLoop})
    1081          */
    1082         protected Executor prepareToClose() {
    1083             return null;
    1084         }
    1085     }
    1086 
    1087     /**
    1088      * Return {@code true} if the given {@link EventLoop} is compatible with this instance.
    1089      */
    1090     protected abstract boolean isCompatible(EventLoop loop);
    1091 
    1092     /**
    1093      * Returns the {@link SocketAddress} which is bound locally.
    1094      */
    1095     protected abstract SocketAddress localAddress0();
    1096 
    1097     /**
    1098      * Return the {@link SocketAddress} which the {@link Channel} is connected to.
    1099      */
    1100     protected abstract SocketAddress remoteAddress0();
    1101 
    1102     /**
    1103      * Is called after the {@link Channel} is registered with its {@link EventLoop} as part of the register process.
    1104      *
    1105      * Sub-classes may override this method
    1106      */
    1107     protected void doRegister() throws Exception {
    1108         // NOOP
    1109     }
    1110 
    1111     /**
    1112      * Bind the {@link Channel} to the {@link SocketAddress}
    1113      */
    1114     protected abstract void doBind(SocketAddress localAddress) throws Exception;
    1115 
    1116     /**
    1117      * Disconnect this {@link Channel} from its remote peer
    1118      */
    1119     protected abstract void doDisconnect() throws Exception;
    1120 
    1121     /**
    1122      * Close the {@link Channel}
    1123      */
    1124     protected abstract void doClose() throws Exception;
    1125 
    1126     /**
    1127      * Called when conditions justify shutting down the output portion of the channel. This may happen if a write
    1128      * operation throws an exception.
    1129      */
    1130     @UnstableApi
    1131     protected void doShutdownOutput() throws Exception {
    1132         doClose();
    1133     }
    1134 
    1135     /**
    1136      * Deregister the {@link Channel} from its {@link EventLoop}.
    1137      *
    1138      * Sub-classes may override this method
    1139      */
    1140     protected void doDeregister() throws Exception {
    1141         // NOOP
    1142     }
    1143 
    1144     /**
    1145      * Schedule a read operation.
    1146      */
    1147     protected abstract void doBeginRead() throws Exception;
    1148 
    1149     /**
    1150      * Flush the content of the given buffer to the remote peer.
    1151      */
    1152     protected abstract void doWrite(ChannelOutboundBuffer in) throws Exception;
    1153 
    1154     /**
    1155      * Invoked when a new message is added to a {@link ChannelOutboundBuffer} of this {@link AbstractChannel}, so that
    1156      * the {@link Channel} implementation converts the message to another. (e.g. heap buffer -> direct buffer)
    1157      */
    1158     protected Object filterOutboundMessage(Object msg) throws Exception {
    1159         return msg;
    1160     }
    1161 
    1162     static final class CloseFuture extends DefaultChannelPromise {
    1163 
    1164         CloseFuture(AbstractChannel ch) {
    1165             super(ch);
    1166         }
    1167 
    1168         @Override
    1169         public ChannelPromise setSuccess() {
    1170             throw new IllegalStateException();
    1171         }
    1172 
    1173         @Override
    1174         public ChannelPromise setFailure(Throwable cause) {
    1175             throw new IllegalStateException();
    1176         }
    1177 
    1178         @Override
    1179         public boolean trySuccess() {
    1180             throw new IllegalStateException();
    1181         }
    1182 
    1183         @Override
    1184         public boolean tryFailure(Throwable cause) {
    1185             throw new IllegalStateException();
    1186         }
    1187 
    1188         boolean setClosed() {
    1189             return super.trySuccess();
    1190         }
    1191     }
    1192 
    1193     private static final class AnnotatedConnectException extends ConnectException {
    1194 
    1195         private static final long serialVersionUID = 3901958112696433556L;
    1196 
    1197         AnnotatedConnectException(ConnectException exception, SocketAddress remoteAddress) {
    1198             super(exception.getMessage() + ": " + remoteAddress);
    1199             initCause(exception);
    1200             setStackTrace(exception.getStackTrace());
    1201         }
    1202 
    1203         @Override
    1204         public Throwable fillInStackTrace() {
    1205             return this;
    1206         }
    1207     }
    1208 
    1209     private static final class AnnotatedNoRouteToHostException extends NoRouteToHostException {
    1210 
    1211         private static final long serialVersionUID = -6801433937592080623L;
    1212 
    1213         AnnotatedNoRouteToHostException(NoRouteToHostException exception, SocketAddress remoteAddress) {
    1214             super(exception.getMessage() + ": " + remoteAddress);
    1215             initCause(exception);
    1216             setStackTrace(exception.getStackTrace());
    1217         }
    1218 
    1219         @Override
    1220         public Throwable fillInStackTrace() {
    1221             return this;
    1222         }
    1223     }
    1224 
    1225     private static final class AnnotatedSocketException extends SocketException {
    1226 
    1227         private static final long serialVersionUID = 3896743275010454039L;
    1228 
    1229         AnnotatedSocketException(SocketException exception, SocketAddress remoteAddress) {
    1230             super(exception.getMessage() + ": " + remoteAddress);
    1231             initCause(exception);
    1232             setStackTrace(exception.getStackTrace());
    1233         }
    1234 
    1235         @Override
    1236         public Throwable fillInStackTrace() {
    1237             return this;
    1238         }
    1239     }
    1240 }

    我们可以看到ChannelOutboundInvoker接口的方法主要交给Pipeline代理。

    并且AbstractChannel留下了很多类似doXXX的抽象方法。这应该是模板模式的应用,由不同的子类实现不同的逻辑。

    还注意到一点,AbstractChannel中有个抽象的内部类,实现了Unsafe接口。

    Unsafe接口有很多方法与ChannelOutboundInvoker中的方法类似。

     看AbstractUnsafe中的实现,与网络链路相关的方法中,具体的业务实现仍然是交给外部接口的方法实现。

    比如register方法;关键的业务逻辑还是交给AbstractChannel中的doRegister方法。

    并且在doRegister注册完成后,调用pipeline的fireXXX方法,让事件在Pipeline中传递。从而实现Netty的事件驱动。

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  • 原文地址:https://www.cnblogs.com/insaneXs/p/9854440.html
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