Resurrect channel deregistration and constructor changes

Motivation:

Due to the complexity of handling deregistration and re-registration of
a channel, we previously decided to remove the deregister() operation
completely to simplify our code.  However, we realized that it shouldn't
be that complicated to implement it during our discussion about making
I/O scheduling more flexible and more customizable [1], and thus the
removal of deregistration and re-registration is unnecessary now.

Modification:

- Revert commit c149f4b
- Revert commit e743a27
- Make some additional adjustments

Result:

- deregister(), fireChannelUnregistered(), and channelRegistered() were
  added back..
- Channel constructors do not require an EventLoop anymore.

[1] netty#2250

handler/src/main/java/io/netty/handler/logging/LoggingHandler.java

@@ -195,6 +195,14 @@ public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
         ctx.fireChannelRegistered();
     }
 
+    @Override
+    public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
+        if (logger.isEnabled(internalLevel)) {
+            logger.log(internalLevel, format(ctx, "UNREGISTERED"));
+        }
+        ctx.fireChannelUnregistered();
+    }
+
     @Override
     public void channelActive(ChannelHandlerContext ctx) throws Exception {
         if (logger.isEnabled(internalLevel)) {

testsuite/src/test/java/io/netty/testsuite/transport/socket/SocketTestPermutation.java

@@ -21,7 +21,6 @@
 import io.netty.bootstrap.ServerBootstrap;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelOption;
-import io.netty.channel.EventLoop;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.oio.OioEventLoopGroup;
@@ -109,8 +108,8 @@ public List<BootstrapComboFactory<Bootstrap, Bootstrap>> datagram() {
                     public Bootstrap newInstance() {
                         return new Bootstrap().group(nioWorkerGroup).channelFactory(new ChannelFactory<Channel>() {
                             @Override
-                            public Channel newChannel(EventLoop loop) {
-                                return new NioDatagramChannel(loop, InternetProtocolFamily.IPv4);
+                            public Channel newChannel() {
+                                return new NioDatagramChannel(InternetProtocolFamily.IPv4);
                             }
 
                             @Override

transport-native-epoll/src/main/java/io/netty/channel/epoll/AbstractEpollChannel.java

@@ -32,12 +32,12 @@ abstract class AbstractEpollChannel extends AbstractChannel {
     volatile int fd;
     int id;
 
-    AbstractEpollChannel(EventLoop eventLoop, int fd, int flag) {
-        this(null, eventLoop, fd, flag, false);
+    AbstractEpollChannel(int fd, int flag) {
+        this(null, fd, flag, false);
     }
 
-    AbstractEpollChannel(Channel parent, EventLoop eventLoop, int fd, int flag, boolean active) {
-        super(parent, eventLoop);
+    AbstractEpollChannel(Channel parent, int fd, int flag, boolean active) {
+        super(parent);
         this.fd = fd;
         readFlag = flag;
         flags |= flag;

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollDatagramChannel.java

@@ -23,7 +23,6 @@
 import io.netty.channel.ChannelOutboundBuffer;
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.ChannelPromise;
-import io.netty.channel.EventLoop;
 import io.netty.channel.RecvByteBufAllocator;
 import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.socket.DatagramChannelConfig;
@@ -51,8 +50,8 @@ public final class EpollDatagramChannel extends AbstractEpollChannel implements
     private volatile boolean connected;
     private final EpollDatagramChannelConfig config;
 
-    public EpollDatagramChannel(EventLoop loop) {
-        super(loop, Native.socketDgramFd(), Native.EPOLLIN);
+    public EpollDatagramChannel() {
+        super(Native.socketDgramFd(), Native.EPOLLIN);
         config = new EpollDatagramChannelConfig(this);
     }
 

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollServerSocketChannel.java

@@ -19,7 +19,6 @@
 import io.netty.channel.ChannelPipeline;
 import io.netty.channel.ChannelPromise;
 import io.netty.channel.EventLoop;
-import io.netty.channel.EventLoopGroup;
 import io.netty.channel.socket.ServerSocketChannel;
 
 import java.net.InetSocketAddress;
@@ -32,13 +31,11 @@
 public final class EpollServerSocketChannel extends AbstractEpollChannel implements ServerSocketChannel {
 
     private final EpollServerSocketChannelConfig config;
-    private final EventLoopGroup childGroup;
     private volatile InetSocketAddress local;
 
-    public EpollServerSocketChannel(EventLoop eventLoop, EventLoopGroup childGroup) {
-        super(eventLoop, Native.socketStreamFd(), Native.EPOLLACCEPT);
+    public EpollServerSocketChannel() {
+        super(Native.socketStreamFd(), Native.EPOLLACCEPT);
         config = new EpollServerSocketChannelConfig(this);
-        this.childGroup = childGroup;
     }
 
     @Override
@@ -81,11 +78,6 @@ protected void doWrite(ChannelOutboundBuffer in) {
         throw new UnsupportedOperationException();
     }
 
-    @Override
-    public EventLoopGroup childEventLoopGroup() {
-        return childGroup;
-    }
-
     final class EpollServerSocketUnsafe extends AbstractEpollUnsafe {
 
         @Override
@@ -109,8 +101,7 @@ void epollInReady() {
                         }
                         try {
                             readPending = false;
-                            pipeline.fireChannelRead(new EpollSocketChannel(EpollServerSocketChannel.this,
-                                    childEventLoopGroup().next(), socketFd));
+                            pipeline.fireChannelRead(new EpollSocketChannel(EpollServerSocketChannel.this, socketFd));
                         } catch (Throwable t) {
                             // keep on reading as we use epoll ET and need to consume everything from the socket
                             pipeline.fireChannelReadComplete();

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollSocketChannel.java

@@ -66,17 +66,17 @@ public final class EpollSocketChannel extends AbstractEpollChannel implements So
     private volatile boolean inputShutdown;
     private volatile boolean outputShutdown;
 
-    EpollSocketChannel(Channel parent, EventLoop eventLoop, int fd) {
-        super(parent, eventLoop, fd, Native.EPOLLIN, true);
+    EpollSocketChannel(Channel parent, int fd) {
+        super(parent, fd, Native.EPOLLIN, true);
         config = new EpollSocketChannelConfig(this);
         // Directly cache the remote and local addresses
         // See https://github.com/netty/netty/issues/2359
         remote = Native.remoteAddress(fd);
         local = Native.localAddress(fd);
     }
 
-    public EpollSocketChannel(EventLoop eventLoop) {
-        super(eventLoop, Native.socketStreamFd(), Native.EPOLLIN);
+    public EpollSocketChannel() {
+        super(Native.socketStreamFd(), Native.EPOLLIN);
         config = new EpollSocketChannelConfig(this);
     }
 

transport-native-epoll/src/test/java/io/netty/channel/epoll/EpollSocketTestPermutation.java

@@ -19,7 +19,6 @@
 import io.netty.bootstrap.ChannelFactory;
 import io.netty.bootstrap.ServerBootstrap;
 import io.netty.channel.Channel;
-import io.netty.channel.EventLoop;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.socket.InternetProtocolFamily;
 import io.netty.channel.socket.nio.NioDatagramChannel;
@@ -100,8 +99,8 @@ public List<TestsuitePermutation.BootstrapComboFactory<Bootstrap, Bootstrap>> da
                     public Bootstrap newInstance() {
                         return new Bootstrap().group(nioWorkerGroup).channelFactory(new ChannelFactory<Channel>() {
                             @Override
-                            public Channel newChannel(EventLoop loop) {
-                                return new NioDatagramChannel(loop, InternetProtocolFamily.IPv4);
+                            public Channel newChannel() {
+                                return new NioDatagramChannel(InternetProtocolFamily.IPv4);
                             }
 
                             @Override

transport-rxtx/src/main/java/io/netty/channel/rxtx/RxtxChannel.java

@@ -19,7 +19,6 @@
 import gnu.io.CommPortIdentifier;
 import gnu.io.SerialPort;
 import io.netty.channel.ChannelPromise;
-import io.netty.channel.EventLoop;
 import io.netty.channel.oio.OioByteStreamChannel;
 
 import java.net.SocketAddress;
@@ -40,8 +39,8 @@ public class RxtxChannel extends OioByteStreamChannel {
     private RxtxDeviceAddress deviceAddress;
     private SerialPort serialPort;
 
-    public RxtxChannel(EventLoop eventLoop) {
-        super(null, eventLoop);
+    public RxtxChannel() {
+        super(null);
 
         config = new DefaultRxtxChannelConfig(this);
     }

transport-sctp/src/main/java/io/netty/channel/sctp/nio/NioSctpChannel.java

@@ -27,7 +27,6 @@
 import io.netty.channel.ChannelMetadata;
 import io.netty.channel.ChannelOutboundBuffer;
 import io.netty.channel.ChannelPromise;
-import io.netty.channel.EventLoop;
 import io.netty.channel.RecvByteBufAllocator;
 import io.netty.channel.nio.AbstractNioMessageChannel;
 import io.netty.channel.sctp.DefaultSctpChannelConfig;
@@ -82,15 +81,15 @@ private static SctpChannel newSctpChannel() {
     /**
      * Create a new instance
      */
-    public NioSctpChannel(EventLoop eventLoop) {
-        this(eventLoop, newSctpChannel());
+    public NioSctpChannel() {
+        this(newSctpChannel());
     }
 
     /**
      * Create a new instance using {@link SctpChannel}
      */
-    public NioSctpChannel(EventLoop eventLoop, SctpChannel sctpChannel) {
-        this(null, eventLoop, sctpChannel);
+    public NioSctpChannel(SctpChannel sctpChannel) {
+        this(null, sctpChannel);
     }
 
     /**
@@ -100,8 +99,8 @@ public NioSctpChannel(EventLoop eventLoop, SctpChannel sctpChannel) {
      *                      or {@code null}.
      * @param sctpChannel   the underlying {@link SctpChannel}
      */
-    public NioSctpChannel(Channel parent, EventLoop eventLoop, SctpChannel sctpChannel) {
-        super(parent, eventLoop, sctpChannel, SelectionKey.OP_READ);
+    public NioSctpChannel(Channel parent, SctpChannel sctpChannel) {
+        super(parent, sctpChannel, SelectionKey.OP_READ);
         try {
             sctpChannel.configureBlocking(false);
             config = new NioSctpChannelConfig(this, sctpChannel);

transport-sctp/src/main/java/io/netty/channel/sctp/nio/NioSctpServerChannel.java

@@ -22,9 +22,7 @@
 import io.netty.channel.ChannelMetadata;
 import io.netty.channel.ChannelOutboundBuffer;
 import io.netty.channel.ChannelPromise;
-import io.netty.channel.EventLoop;
-import io.netty.channel.EventLoopGroup;
-import io.netty.channel.nio.AbstractNioMessageServerChannel;
+import io.netty.channel.nio.AbstractNioMessageChannel;
 import io.netty.channel.sctp.DefaultSctpServerChannelConfig;
 import io.netty.channel.sctp.SctpServerChannelConfig;
 
@@ -46,9 +44,8 @@
  * Be aware that not all operations systems support SCTP. Please refer to the documentation of your operation system,
  * to understand what you need to do to use it. Also this feature is only supported on Java 7+.
  */
-public class NioSctpServerChannel extends AbstractNioMessageServerChannel
+public class NioSctpServerChannel extends AbstractNioMessageChannel
         implements io.netty.channel.sctp.SctpServerChannel {
-
     private static final ChannelMetadata METADATA = new ChannelMetadata(false);
 
     private static SctpServerChannel newSocket() {
@@ -65,9 +62,9 @@ private static SctpServerChannel newSocket() {
     /**
      * Create a new instance
      */
-    public NioSctpServerChannel(EventLoop eventLoop, EventLoopGroup childGroup) {
-        super(null, eventLoop, childGroup, newSocket(), SelectionKey.OP_ACCEPT);
-        config = new NioSctpServerChannelConfig(this, javaChannel());
+    public NioSctpServerChannel() {
+        super(null, newSocket(), SelectionKey.OP_ACCEPT);
+        config = new DefaultSctpServerChannelConfig(this, javaChannel());
     }
 
     @Override
@@ -143,7 +140,7 @@ protected int doReadMessages(List<Object> buf) throws Exception {
         if (ch == null) {
             return 0;
         }
-        buf.add(new NioSctpChannel(this, childEventLoopGroup().next(), ch));
+        buf.add(new NioSctpChannel(this, ch));
         return 1;
     }
 

transport-sctp/src/main/java/io/netty/channel/sctp/oio/OioSctpChannel.java

@@ -26,7 +26,6 @@
 import io.netty.channel.ChannelMetadata;
 import io.netty.channel.ChannelOutboundBuffer;
 import io.netty.channel.ChannelPromise;
-import io.netty.channel.EventLoop;
 import io.netty.channel.RecvByteBufAllocator;
 import io.netty.channel.oio.AbstractOioMessageChannel;
 import io.netty.channel.sctp.DefaultSctpChannelConfig;
@@ -88,17 +87,17 @@ private static SctpChannel openChannel() {
     /**
      * Create a new instance with an new {@link SctpChannel}.
      */
-    public OioSctpChannel(EventLoop eventLoop) {
-        this(eventLoop, openChannel());
+    public OioSctpChannel() {
+        this(openChannel());
     }
 
     /**
      * Create a new instance from the given {@link SctpChannel}.
      *
      * @param ch    the {@link SctpChannel} which is used by this instance
      */
-    public OioSctpChannel(EventLoop eventLoop, SctpChannel ch) {
-        this(null, eventLoop, ch);
+    public OioSctpChannel(SctpChannel ch) {
+        this(null, ch);
     }
 
     /**
@@ -108,8 +107,8 @@ public OioSctpChannel(EventLoop eventLoop, SctpChannel ch) {
      *                  {@link} has no parent as it was created by your self.
      * @param ch        the {@link SctpChannel} which is used by this instance
      */
-    public OioSctpChannel(Channel parent, EventLoop eventLoop, SctpChannel ch) {
-        super(parent, eventLoop);
+    public OioSctpChannel(Channel parent, SctpChannel ch) {
+        super(parent);
         this.ch = ch;
         boolean success = false;
         try {

transport-sctp/src/main/java/io/netty/channel/sctp/oio/OioSctpServerChannel.java

@@ -22,9 +22,7 @@
 import io.netty.channel.ChannelMetadata;
 import io.netty.channel.ChannelOutboundBuffer;
 import io.netty.channel.ChannelPromise;
-import io.netty.channel.EventLoop;
-import io.netty.channel.EventLoopGroup;
-import io.netty.channel.oio.AbstractOioMessageServerChannel;
+import io.netty.channel.oio.AbstractOioMessageChannel;
 import io.netty.channel.sctp.DefaultSctpServerChannelConfig;
 import io.netty.channel.sctp.SctpServerChannelConfig;
 import io.netty.util.internal.logging.InternalLogger;
@@ -49,7 +47,7 @@
  * Be aware that not all operations systems support SCTP. Please refer to the documentation of your operation system,
  * to understand what you need to do to use it. Also this feature is only supported on Java 7+.
  */
-public class OioSctpServerChannel extends AbstractOioMessageServerChannel
+public class OioSctpServerChannel extends AbstractOioMessageChannel
         implements io.netty.channel.sctp.SctpServerChannel {
 
     private static final InternalLogger logger =
@@ -72,17 +70,17 @@ private static SctpServerChannel newServerSocket() {
     /**
      * Create a new instance with an new {@link SctpServerChannel}
      */
-    public OioSctpServerChannel(EventLoop eventLoop, EventLoopGroup childGroup) {
-        this(eventLoop, childGroup, newServerSocket());
+    public OioSctpServerChannel() {
+        this(newServerSocket());
     }
 
     /**
      * Create a new instance from the given {@link SctpServerChannel}
      *
      * @param sch    the {@link SctpServerChannel} which is used by this instance
      */
-    public OioSctpServerChannel(EventLoop eventLoop, EventLoopGroup childGroup, SctpServerChannel sch) {
-        super(null, eventLoop, childGroup);
+    public OioSctpServerChannel(SctpServerChannel sch) {
+        super(null);
         if (sch == null) {
             throw new NullPointerException("sctp server channel");
         }
@@ -198,7 +196,7 @@ protected int doReadMessages(List<Object> buf) throws Exception {
                     if (key.isAcceptable()) {
                         s = sch.accept();
                         if (s != null) {
-                            buf.add(new OioSctpChannel(this, childEventLoopGroup().next(), s));
+                            buf.add(new OioSctpChannel(this, s));
                             acceptedChannels ++;
                         }
                     }

transport-udt/src/main/java/io/netty/channel/udt/nio/NioUdtAcceptorChannel.java

@@ -19,9 +19,7 @@
 import com.barchart.udt.nio.ServerSocketChannelUDT;
 import io.netty.channel.ChannelException;
 import io.netty.channel.ChannelOutboundBuffer;
-import io.netty.channel.EventLoop;
-import io.netty.channel.EventLoopGroup;
-import io.netty.channel.nio.AbstractNioMessageServerChannel;
+import io.netty.channel.nio.AbstractNioMessageChannel;
 import io.netty.channel.udt.DefaultUdtServerChannelConfig;
 import io.netty.channel.udt.UdtServerChannel;
 import io.netty.channel.udt.UdtServerChannelConfig;
@@ -36,16 +34,15 @@
 /**
  * Common base for Netty Byte/Message UDT Stream/Datagram acceptors.
  */
-public abstract class NioUdtAcceptorChannel extends AbstractNioMessageServerChannel implements UdtServerChannel {
+public abstract class NioUdtAcceptorChannel extends AbstractNioMessageChannel implements UdtServerChannel {
 
     protected static final InternalLogger logger =
             InternalLoggerFactory.getInstance(NioUdtAcceptorChannel.class);
 
     private final UdtServerChannelConfig config;
 
-    protected NioUdtAcceptorChannel(EventLoop eventLoop, EventLoopGroup childGroup,
-            ServerSocketChannelUDT channelUDT) {
-        super(null, eventLoop, childGroup, channelUDT, OP_ACCEPT);
+    protected NioUdtAcceptorChannel(final ServerSocketChannelUDT channelUDT) {
+        super(null, channelUDT, OP_ACCEPT);
         try {
             channelUDT.configureBlocking(false);
             config = new DefaultUdtServerChannelConfig(this, channelUDT, true);
@@ -61,8 +58,8 @@ protected NioUdtAcceptorChannel(EventLoop eventLoop, EventLoopGroup childGroup,
         }
     }
 
-    protected NioUdtAcceptorChannel(EventLoop eventLoop, EventLoopGroup childGroup, final TypeUDT type) {
-        this(eventLoop, childGroup, NioUdtProvider.newAcceptorChannelUDT(type));
+    protected NioUdtAcceptorChannel(final TypeUDT type) {
+        this(NioUdtProvider.newAcceptorChannelUDT(type));
     }
 
     @Override