INT-4465: Fix delay in close propagation with NIO

JIRA: https://jira.spring.io/browse/INT-4465

There is a one second delay before a socket close is propagated if there is an active
assembler. This is generally only a problem with deserializers that use EOF to signal
message end (such as the `ByteArrayElasticRawDeserializer`).

Attempt to insert an EOF marker into the buffer queue so that the `getNextBuffer()` will
exit immediately on `close()` if it is blocked awaiting a buffer.

**cherry-pick to 5.0.x, 4.3.x**

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/TcpNioConnection.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -58,6 +58,8 @@ public class TcpNioConnection extends TcpConnectionSupport {
 
 	private static final long DEFAULT_PIPE_TIMEOUT = 60000;
 
+	private static final byte[] EOF = new byte[0]; // EOF marker buffer
+
 	private final SocketChannel socketChannel;
 
 	private final ChannelOutputStream channelOutputStream;
@@ -714,7 +716,7 @@ public class TcpNioConnection extends TcpConnectionSupport {
 			while (buffer == null) {
 				try {
 					buffer = this.buffers.poll(1, TimeUnit.SECONDS);
-					if (buffer == null && this.isClosed) {
+					if (buffer == EOF || (buffer == null && this.isClosed)) {
 						return null;
 					}
 				}
@@ -758,6 +760,12 @@ public class TcpNioConnection extends TcpConnectionSupport {
 		public void close() throws IOException {
 			super.close();
 			this.isClosed = true;
+			try {
+				this.buffers.offer(EOF, TcpNioConnection.this.pipeTimeout, TimeUnit.SECONDS);
+			}
+			catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+			}
 		}
 
 		@Override

spring-integration-ip/src/test/java/org/springframework/integration/ip/tcp/connection/TcpNioConnectionTests.java

@@ -17,6 +17,7 @@
 package org.springframework.integration.ip.tcp.connection;
 
 import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.lessThan;
 import static org.hamcrest.Matchers.not;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -64,6 +65,7 @@ import javax.net.SocketFactory;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
+import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TestName;
@@ -90,6 +92,7 @@ import org.springframework.messaging.Message;
 import org.springframework.messaging.support.ErrorMessage;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
 import org.springframework.util.ReflectionUtils;
+import org.springframework.util.StopWatch;
 
 
 /**
@@ -130,6 +133,7 @@ public class TcpNioConnectionTests {
 				Socket s = server.accept();
 				// block so we fill the buffer
 				done.await(10, TimeUnit.SECONDS);
+				s.close();
 			}
 			catch (Exception e) {
 				e.printStackTrace();
@@ -806,6 +810,36 @@ public class TcpNioConnectionTests {
 		te.shutdown();
 	}
 
+	@Test
+	@Ignore // Timing is too short for CI/Travis
+	public void testNoDelayOnClose() throws Exception {
+		TcpNioServerConnectionFactory cf = new TcpNioServerConnectionFactory(0);
+		final CountDownLatch reading = new CountDownLatch(1);
+		final StopWatch watch = new StopWatch();
+		cf.setDeserializer(is -> {
+			reading.countDown();
+			watch.start();
+			is.read();
+			is.read();
+			watch.stop();
+			return null;
+		});
+		cf.registerListener(m -> false);
+		final CountDownLatch listening = new CountDownLatch(1);
+		cf.setApplicationEventPublisher(e -> {
+			listening.countDown();
+		});
+		cf.afterPropertiesSet();
+		cf.start();
+		assertTrue(listening.await(10, TimeUnit.SECONDS));
+		Socket socket = SocketFactory.getDefault().createSocket("localhost", cf.getPort());
+		socket.getOutputStream().write("x".getBytes());
+		assertTrue(reading.await(10, TimeUnit.SECONDS));
+		socket.close();
+		cf.stop();
+		assertThat(watch.getLastTaskTimeMillis(), lessThan(950L));
+	}
+
 	private void readFully(InputStream is, byte[] buff) throws IOException {
 		for (int i = 0; i < buff.length; i++) {
 			buff[i] = (byte) is.read();