Java application clustering made easy

Ever wanted to share the state and emit signals between two applications? and how about a variable number of application instances? you know how hard it is to do it efficiently, in a multicast way, etc.
And how about recognizing an instance failure? All those features are hard to write and harder to test.
Shoal comes to the rescue. This framework derived from the GlassFish project, provides cluster communication, join and failure signals, messaging and data sharing.