Add instructions

Author: cescoffier

Diff for: resources/cluster/README.md

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+# Vert.x Cluster Configuration
+
+By default, the Vert.x cluster manager based on Infinispan uses _multicast_. If your network does not support 
+_multicast_, you can configure Infinispan to use another discovery protocol such as _unicast_.
+
+Infinispan is based on _JGroups_, and to configure the discovery, you must provide a `jgroups.xml` file in the 
+application `CLASSPATH`.
+
+The `jgroups.xml` file available in this directory is configured to use _unicast_ on 127.0.0.1. You will only 
+discover applications running on the same machine. To use this configuration, just copy the file to the 
+`src/main/resources` directory of your source code.                                                                    
+        
+