INT-3520: Add Reactor's PersistentQueue Support

JIRA: https://jira.spring.io/browse/INT-3520

INT-3520: Use `Condition` to wait items in the `Queue`

INT-3520: Reworking to the `Semaphore(0)`

* Implement 'artificial infinite wait'
* Add distributed test with infinite `receive()`

INT-3520: Correct usage of `Semaphore`

Minor Doc Polishing

src/reference/docbook/channel.xml

@@ -557,9 +557,9 @@ payload to an Integer.
 	  is polled from a <classname>QueueChannel</classname>, it is removed from the Message Store.
       </para>
       <para>
-      By default any <classname>QueueChannel</classname> only stores its Messages in an in-memory Queue
+      By default, a <classname>QueueChannel</classname> stores its Messages in an in-memory Queue
       and can therefore lead to the lost message scenario mentioned above. However Spring Integration
-      provides a <classname>JdbcMessageStore</classname> to allow a <classname>QueueChannel</classname> to be backed by an RDBMS.
+      provides persistent stores, such as the <classname>JdbcMessageStore</classname>.
       </para>
       <para>
       You can configure a Message Store for any <classname>QueueChannel</classname> by adding the
@@ -593,6 +593,21 @@ payload to an Integer.
         is a <interfacename>ChannelPriorityMessageStore</interfacename> the messages will be received in
         FIFO within priority order. The notion of priority is determined by the message store implementation.
       </para>
+	  <para>
+		  Another option to customize the QueueChannel environment is provided by the <code>ref</code> attribute of the
+		  <code>&lt;int:queue&gt;</code> sub-element. This attribute implies the reference to any
+		  <interfacename>java.util.Queue</interfacename> implementation. An implementation is provided
+		  by the <ulink url="https://github.com/reactor/reactor">Project Reactor</ulink> and its
+		  <classname>reactor.queue.PersistentQueue</classname> implementation for the
+		  <ulink url="https://github.com/OpenHFT/Chronicle-Queue">IndexedChronicle</ulink>:
+	  </para>
+		<programlisting language="java"><![CDATA[@Bean
+public QueueChannel reactorQueue() {
+    return new QueueChannel(new PersistentQueueSpec<Message<?>>()
+                    .codec(new JavaSerializationCodec<Message<?>>())
+                    .basePath(System.getProperty("java.io.tmpdir") + "/reactor-queue")
+                    .get());
+}]]></programlisting>
     </section>
 
     <section id="channel-configuration-pubsubchannel">

src/reference/docbook/whats-new.xml

@@ -237,5 +237,16 @@
 				See <xref linkend="service-activator-namespace"/>.
 			</para>
 		</section>
+		<section id="4.1-queue-channel-queue.typ">
+			<title>QueueChannel: backed Queue type</title>
+			<para>
+				The <classname>QueueChannel</classname> backed <classname>Queue type</classname> has been changed
+				from <interfacename>BlockingQueue</interfacename> to the more generic
+				<interfacename>Queue</interfacename>. It allows the use of any external
+				<interfacename>Queue</interfacename> implementation, for example Reactor's
+				<classname>PersistentQueue</classname>.
+				See <xref linkend="channel-configuration-queuechannel"/>.
+			</para>
+		</section>
 	</section>
 </chapter>