Make sure writing to a closed channel does not trigger an UnsupportedOperationException

- Fixes #1442

transport/src/main/java/io/netty/channel/AbstractChannel.java

@@ -29,6 +29,7 @@ import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.nio.channels.ClosedChannelException;
+import java.nio.channels.NotYetConnectedException;
 import java.util.Random;
 import java.util.concurrent.ConcurrentMap;
 
@@ -671,7 +672,20 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             }
 
             inFlushNow = true;
+
             final ChannelOutboundBuffer outboundBuffer = AbstractChannel.this.outboundBuffer;
+
+            // Mark all pending write requests as failure if the channel is inactive.
+            if (!isActive()) {
+                if (isOpen()) {
+                    outboundBuffer.fail(new NotYetConnectedException());
+                } else {
+                    outboundBuffer.fail(new ClosedChannelException());
+                }
+                inFlushNow = false;
+                return;
+            }
+
             try {
                 for (;;) {
                     ChannelPromise promise = outboundBuffer.currentPromise;

transport/src/test/java/io/netty/channel/local/LocalChannelTest.java

@@ -17,6 +17,7 @@ package io.netty.channel.local;
 
 import io.netty.bootstrap.Bootstrap;
 import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.AbstractChannel;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
@@ -27,20 +28,20 @@ import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
 import org.junit.Test;
 
+import java.nio.channels.ClosedChannelException;
 import java.util.concurrent.CountDownLatch;
 
+import static org.hamcrest.CoreMatchers.*;
 import static org.junit.Assert.*;
 
-public class LocalChannelRegistryTest {
+public class LocalChannelTest {
 
-    private static final InternalLogger logger =
-            InternalLoggerFactory.getInstance(LocalChannelRegistryTest.class);
+    private static final InternalLogger logger = InternalLoggerFactory.getInstance(LocalChannelTest.class);
 
     private static final String LOCAL_ADDR_ID = "test.id";
 
     @Test
     public void testLocalAddressReuse() throws Exception {
-
         for (int i = 0; i < 2; i ++) {
             EventLoopGroup clientGroup = new LocalEventLoopGroup();
             EventLoopGroup serverGroup = new LocalEventLoopGroup();
@@ -94,10 +95,57 @@ public class LocalChannelRegistryTest {
         }
     }
 
+    @Test
+    public void testWriteFailsFastOnClosedChannel() throws Exception {
+        EventLoopGroup clientGroup = new LocalEventLoopGroup();
+        EventLoopGroup serverGroup = new LocalEventLoopGroup();
+        LocalAddress addr = new LocalAddress(LOCAL_ADDR_ID);
+        Bootstrap cb = new Bootstrap();
+        ServerBootstrap sb = new ServerBootstrap();
+
+        cb.group(clientGroup)
+                .channel(LocalChannel.class)
+                .handler(new TestHandler());
+
+        sb.group(serverGroup)
+                .channel(LocalServerChannel.class)
+                .childHandler(new ChannelInitializer<LocalChannel>() {
+                    @Override
+                    public void initChannel(LocalChannel ch) throws Exception {
+                        ch.pipeline().addLast(new TestHandler());
+                    }
+                });
+
+        // Start server
+        sb.bind(addr).sync();
+
+        // Connect to the server
+        final Channel cc = cb.connect(addr).sync().channel();
+
+        // Close the channel and write something.
+        cc.close().sync();
+        try {
+            cc.write(new Object()).sync();
+            fail("must raise a ClosedChannelException");
+        } catch (Exception e) {
+            assertThat(e, is(instanceOf(ClosedChannelException.class)));
+            // Ensure that the actual write attempt on a closed channel was never made by asserting that
+            // the ClosedChannelException has been created by AbstractUnsafe rather than transport implementations.
+            assertThat(e.getStackTrace()[0].getClassName(), is(AbstractChannel.class.getName() + "$AbstractUnsafe"));
+            e.printStackTrace();
+        }
+
+        serverGroup.shutdownGracefully();
+        clientGroup.shutdownGracefully();
+        serverGroup.terminationFuture().sync();
+        clientGroup.terminationFuture().sync();
+    }
+
     static class TestHandler extends ChannelInboundHandlerAdapter {
         @Override
         public void messageReceived(ChannelHandlerContext ctx, MessageList<Object> msgs) throws Exception {
-            for (int i = 0; i < msgs.size(); i ++) {
+            final int size = msgs.size();
+            for (int i = 0; i < size; i ++) {
                 logger.info(String.format("Received mesage: %s", msgs.get(i)));
             }
         }